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Patent 1269596 Summary

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Claims and Abstract availability

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(12) Patent: (11) CA 1269596
(21) Application Number: 539855
(54) English Title: CHIP MOUNTING DEVICE AND CHIP CARRIER MOUNTING DEVICE
(54) French Title: DISPOSITIF DE MONTAGE DE PUCES ET DISPOSITIF DE MONTAGE DE SUPPORTS DE PUCE
Status: Expired
Bibliographic Data
(52) Canadian Patent Classification (CPC):
  • 148/59
  • 26/90
  • 113/96
(51) International Patent Classification (IPC):
  • H01L 21/58 (2006.01)
  • B23K 3/06 (2006.01)
  • B23K 35/02 (2006.01)
  • B23K 35/14 (2006.01)
  • H05K 3/32 (2006.01)
  • H05K 3/34 (2006.01)
  • H05K 13/04 (2006.01)
  • H05K 3/40 (2006.01)
(72) Inventors :
  • ALLEN, LESLIE JOHN (United Kingdom)
  • CHERIAN, GABE (United States of America)
  • DIAZ, STEPHEN H. (United States of America)
(73) Owners :
  • RAYCHEM CORPORATION (United States of America)
(71) Applicants :
(74) Agent: FETHERSTONHAUGH & CO.
(74) Associate agent:
(45) Issued: 1990-05-29
(22) Filed Date: 1984-06-29
Availability of licence: N/A
(25) Language of filing: English

Patent Cooperation Treaty (PCT): No

(30) Application Priority Data:
Application No. Country/Territory Date
509,684 United States of America 1983-06-30
610,077 United States of America 1984-05-14

Abstracts

English Abstract


ABSTRACT



A chip carrier mounting device includes a retaining
member having a predefined pattern of apertures in
which are positioned preforms of joint-forming material
such as solder. The preform retains its general
configuration after the interconnection or soldering
process to form a resilient joint which is more capable
of withstanding stress, strain and fatigue. The
joint-forming material may be a filled solder composition
or a supported solder which substantially maintain
their physical shape when the solder is molten, or a
conductive elastomer.


Claims

Note: Claims are shown in the official language in which they were submitted.


26775-71D
THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A solder composition comprising:
solder; and
disposed in the solder a filler comprising discrete
particles or filaments which are solid at a temperature at which
the solder is molten, which are present in an amount of from 20%
to 80% by weight based on the total weight of the solder-filler
mixture, and which are of sufficient size and density substantial-
ly to maintain the solder in a preformed shape when the solder is
molten.
2. A solder composition according to claim 1 wherein the
filler comprises metal particles or filaments.
3. A solder composition according to claim 2 wherein the
metal comprises copper.
4. A solder column for forming electrical connections com-
prising:
solder; and
disposed in the solder a filler comprising discrete
particles or filaments which are of a material which is solid at
a temperature at which the solder is molten, and which are present
in an amount sufficient substantially to maintain the column-like
shape when the solder is molten
5. A solder column according to claim 4 wherein the filler
comprises a metal powder or filament.
- 35 -

26775-71D

6. A solder column according to claim 4 wherein the filler
comprises lengths of metal wire.
7. A solder column for forming electrical connections
comprising:
solder; and
disposed about the outside of the solder a support
strand or tape which is of a material which is solid at a
temperature at which the solder is molten, and which to disposed
about the outside of the solder in a pattern whereby the column-
like shape of the solder is substantially maintained when the
solder is molten.
8. A solder column according to claim 7 wherein the support
comprises a metal wire or a metal tape.
9. A solder column according to claim 7 wherein the support
strand or tape is disposed about the solder wire in the form of a
spiral wrap.
10. A solder column according to claim 7 wherein the support
strand or tape is disposed about the solder wire in the form of a
braid.

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26775-71D

11. A method of making a columnar solder preform, which
comprises,
(a) providing a solder wire; and
(b) providing a support strand or tape disposed about
the outside of the solder wire such that the shape of the preform
is substantially maintained by surface tension when the solder is
molten, the material of the support strand or tape being solid at
a temperature at which the solder is molten.
12. A method as claimed in claim 11, which includes the step
of heating the preform, after the support strand or tape has been
applied, so as to cause the solder to flow.
13. A method as claimed in claim 11, in which the support
strand or tape is disposed about the solder wire in the form of a
spiral wrap.
14. A method as claimed in claim 13, in which the support
strand or tape is so disposed by wrapping the strand or tape
around the wire.
15. A method as claimed in claim 11, in which the support
strand or tape is disposed about the solder wire in the form of a
braid.
16. A method as claimed in claim 15, in which the support
strand or tape is so disposed by braiding the strand or tape

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26775-71D
around the wire.
17. A method as claimed in claim 11, which includes the step
of cutting the preform into pieces after the support strand or
tape has been applied.
18. A method of making an assembly of solder preforms which
comprises the steps of providing a retaining member having
apertures therein for receiving respective solder preforms, and
positioning solder preforms made by the method claimed in claim 11
in the apertures.
19. A method of melting a columnar solder preform, which
comprises:
(a) providing a preformed support in the form of a
spiral wrap or a braid of a strand or tape,
(b) immersing the support in molten solder which is at
a temperature at which the material of the support is
substantially solid; to that solder fills the support; and
(c) removing the support from the molten solder;
the support being such that solder is substantially maintained
within it when molten by surface tension.
20. A method as claimed in claim 19, which includes the step
of cutting the preform into pieces after the support strand or
tape has been applied.
- 38 -

26775-71D
21. A method of making an assembly of solder preforms, which
comprises the steps of providing a retaining member having
apertures therein form receiving respective solder preforms, and
positioning solder preforms made by the method claimed in claim 19
in the apertures.
22. A method as claimed in claim 19, which includes the step
of forming the support.
23. An assembly of at least two electrically conductive
elements, each having at least one contact, and a columnar solder
preform which extends between the contacts forming an electrical
connection between them, the preform comprising a support in the
form of a spiral wrap or braid of a strand or tape, and a quantity
of solder within the support, the support being such that the
solder is substantially maintained within it when molten by
surface tension.
24. An assembly as claimed in claim 23, in which one of the
elements is a circuit board.
25. An assembly as claimed in claim 23, in which one of the
elements is a chip carrier.

- 39 -

Description

Note: Descriptions are shown in the official language in which they were submitted.


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This is a divisional of copending Canadian Patent
Application Serial No. 457,810 filed on June 29, 1984
by Raychem Corporation.
This invention relates to electrical interconnections,
and to methods, devices and materials for forming such
interconnections. More particularly, the invention is
directed to methods, devices and materials for attaching
electronic components, especially chips ~r chip carrier
packages, to each other or to supporting substrates, such as
circuit boards.
The microelectronics industry is steadily moving
toward the use of large chips and chip carrier packages
~O (CCP) which have connection pads on the faces and/or edges.
These are generally used where there are limitations with
the use of dual inline packages (DIP). The number of
~ connections on the most popular packages can range f~om 64
; to 156. Chip carrier packages can be produced with leads
attached (leaded~ or they can be leadless.
Leaded CCPs can be soldered directly onto printed cir-
cuit boards (PCB) or printed wire boards (PWB)~ Leadless
CCPs can be soldered onto ceramic boards or installed into
connectors. However, with glass/epoxy printed circuit boards
~o or printed wire boards, leadless CCPs are usually mounted
into connectors which are in turn mounted on the PCBs because
o~ the effect of the different thermal expansion coefficients
of the materials involved when subjected to temperature
fluctuations~ These connectors are complex to manufacture
~o and costly to use. As used herein "electrically conductive
elements" is intended to include CCP, PCB, PWB and other
electronic or electrical components.




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A5 the CCP technology improve and their reliability
increases, more emph~sis iB directed to ~olderin~ the~e
; packag0s directly onto t~Ei PCBs to ~ske more use of the
board ~pa~e~ and di~pensing with the connectors ~ven though
the use of connector~ per~its replacement of ~ulty CCPi.
The ro~t of conventional connectors relative to the C08t of
the CCPi can be disproportionately high. Thi~ i8 8 strong
incentive to use CCPs without connector~.
However, the direct soldering of CCPs on PCBs without
the use of connectors iB associated with a number of problems.
(1) The variation of the surface flatness and non-parallel
contours between the CCP and the boards produces vHrying
sol~er joint heights. (2) The solder ~ill have a tendency
to wick o.ut of the joint area into crevices or ~astellations
in the CCP9 thus "starving" the joint are~. (3) ~old elloy-
ing with the solder ~ill produce ambrittlement of the
Btaryedll joint. (4) Differential thermal e~pansion between
~` ~ the CCP and the board will fr~ctur~ a thin aolder joint due
to the high shear strains in the joint~ (5) 8ridging
;~ ~o between joints may occur if exce3s solder is present or if
the distance between the jointe i8 small. ~S) Solder
looation toleranceR are small and getting smaller yet with
. ~ .
~; ~ incr~asing packaging density, ~ith e typical connection
:~ p~d hsving ~ width o~ O.:D12 inehes and a O.D22-inch cienter-
~5 to-center spacing~ ~7) Flux remoYal from the space between
~:~ the CCP and the PCB and ~ubsequent in~pection thersof. (8)
~; The sol:der p~stes used to attsch the CCP will produce loose
solder balls which cEuse electrical problems.

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Different ~olutiDns h~ve be~n pr~o~ed for the fore-
going problems. Th~ proper positioning of R prodBtermined
quantity of solder may be achieved with the use of ~older
preforms spaced on B carrier or template in the locations
corresponding to the points where the solder joint~ are to be
formed. Example~ of this technique ~ay be found in U.S.
Patents 3,320,658, issued to Bolda et al; 3,396,B94, issued
t~ Ellis; ~,472~365, issued to Tiedems; 3,719,9B~, i8 ued to
5teitzg 3,744912g, i~sued to Dewey; 4,209,B9~, issued to
Dyce et al.; and 49216,350j.i~sued to Reid.
Other examples of solder p~cks and solder preforms are
in U.S. Patent Nos. 3,040,119 to Granzow; 3,535~769 to
Gold~chmid; 3,750,265 to Cushman; 4,099,615 to Lemke et al~
~nd 4,142,286 to Knuth et ~1. U.S. P~tent No. 3,9B2,320 to
Buchoff et al. disclo~es electrically conductive connectors
constructed from non-conductive and conductive el~stomers.
Although the foregoing techniques provide for the cor-
rect placement of a predetermined qu~ntity of solder or
other ~uitsble joint-forming materi~l, snd with the proper
2~ dimensioning of the carrier or template~ cufficiently small
qua~tities of solder can be positioned on close sp~cing
between centers, these proposals do not address the problem
of hi~h shear strains in the solder joints.
As noted above, among the factors considered in forming
~5 acceptable electricsl connections between the CCP and the
~B is that the connect~ons mu~t be ~ble to withstand
~tre~ses developed due to the effect of temperature fluctua-
tions and the difference~ in thermal expsnsion coefficients
between the moteri~l of the CCP and the substr~te or circuit
board on which it i8 mounted. ~hus, a CCP may be ~ade of a
cersmic material and the circuit board may be made of an
epoxy-gless composition, snd when subjected tD ~levsted
te~perature~ these ~lement~ will expand at dif~erent r~tes,
inducing ~tre8~e8 in the connections.
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Even if the materi~:ls uaed in the CCP ond the oirouit
board h~ve ther~al expansion ooef`ficients whieh are close in
val~le to minimize the differential expansion ef~ect~l heating/
cooling eycle~ which result ~qhen power i8 bpplied acros3 the
~CP induce a temperature differential between the CCP ~nd the
PCB to produce stresses in the joint
, lt i8 ~ell known, and as summarized belo~, that if the
solder joint iB formed into.~ "long" colu~n configuration
in which the height of the o~lumn i8 much greEIter th~n the
dia~et~r or transverse dimension of the ~oint, le88 atre~s
i~ induced in the joint snd consequently the joint has
greater reliability and longer life.
In the patent to Krall, U.S. No. 3,921,2e5, a method
is described for joining microminiature component~ to e
carrying ~tructure in which the height of the eloctrical
connections may be adjustsd during original joining of thR
com~onent to the oarrying struoture or in a two-step solder
r~flow pro~es~.
In U.S. Patent No. 4,412,642 to Fisher le~dless chip
csrriers are convertsd to ~cast-le~ded chip oarriers" by
molding high m~lting point lead~ to the chip carrier.
~ddition~l example~ of ~ethods and devices for interconnecting
chip.carriers and bo~rds ~re chown in U . S. Patent Nos.
3.~73,4Bl to Lins et el.~ 3,6BO,lgB to Wood, 3,811,186 to
~5 Larnerd et al. ~nd 4,179,B02 to 30shi et ~1. Other methods
of atteching eleetronic co~pon~nts, include the pin solder
:~ :terminals of U.S. Pat~nt No. 3,750,252 to Lendm~n and the
ollapsed springc of U.S. Patent No. 3,616,532 to 8eck.
OSh~r exemples of 301dering chip carriers to bo~rds include
31~ U. 5 . Pst~nt Nos. 3 ,392 ,442 to Napier et ~1., 3 ,401,126 tD
;`Mill~r ~t al., 3~4Z9,040 to Miller, 3,355,D78 to Smith,
~ 3,B59,723 to Ho~er et al. ~nd 3,61149B32 to Ch~nce et ~1.



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~ he abov~ disclosure~ ~ddress the problem of connections
which ~st be able to ~ithstand the ~tree~e3 From thermal
oyolea, none disclose a ~Dtisfactory ~olution ~hi~h both
~nlves the problem and i suit~ble for reliable msnufacturing
proce~es.
In the ~bove diaclosuP~s the solder used i5 conventional
solder which r~adily flows when molten. The flow i8 u8U~lly
uf a capillary nature when the ~older i~ on a ~ettable
surface~ ~uch ~8 a pre-tinned contact lead. Such conventional
~Q solder has a high surface tension tending to make the molten
solder form balla when un ~ non-wettable ~urface or when
positioned on n sm~ll ares of wett~ble surface, ~uch ss an
: el~ctrical oDntact psd, and ~urrounded by a ncn wettable
surface, such 88 ~pOXy ~oard or ceramic sub3trate. When the
mass of the solder is too grest fDr the ~v~ilable wett~ble
~ urface, the solder will ~low ~cross the non-wettable
-~ eurf~ces and m~y bridge nearby electrical contaot~.
Solder hss been used in verious forms and oompositions
fer a variety of purp~ses as illustrated in U.S. Patent Nos.
1,281,126 to Bevan, 1,291,B7B to Hess, 1~564,335 to Feldkamp,
2,431~611 to Dur~t, 3,163,50~ to Konr~d et al., 3,467,765 to
Gr-~ft, 3,605,902 and 3,638,734 to Ault, 3,900,153 to Beerwerth
~t al., ~nd 4,290,195 to Rippere.

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It is a primary object of the present invention to pro-
vide a device and a method for the precise placement of a
predetermined quantity of material for the formation of a
solder-type connection between electrically-conductive
elements.
Another object of the invention is to provide a
connection~forming material which will sufficiently retain
its shape at melting temperatures to form structural and
electrical connection between electrically conductive
elements,
Another object of the invention is to provide an appara-
tus and a method of the foregoing type for the placement of a
connection-forming material having a predefined configuration.
Another object of the invention is to provide an appara-

tus and a method of the foregoing type for the placement of aconnection-forming material preform having a height dimension
greater than its transverse dimension.
Yet another object of the invention is to provide an
apparatus and a method of the foregoing type for the formation
of solder-type connections which are resilient and better able
to withstand fatigue or repetitive thermal cycling.
Still another object of the invention is to provide an
apparatu6 and a method of the foregoing type for the simultane-
ous formation of a plurality of resilient solder-type connec-

ti~ns between a plurality of parallel-disposed electrically-
conductive elements.
A further object of the invention is to provide an
apparatus and a method to attach an electronic component to
a circuit board.
Yet a further object of the invention is to accurately
~ aligo the CCP uith the PWB.


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- 8 - 26775-71D
A specific object of the present invention and that of
the parent Canadian Application Serial No. 457,810 is to provide
apparatus, materials and methods to attach an electronic component
to a circuit board with resilient solder joints which are better
able to withstand thermal cycling/fa-tigue stresses, to accommodate
dimensional irregularities in the components, the circuit board
and the conductive elements thereon and to enable higl~ speed, high
reliability manufacture of electronics component - circuit board
devices~
The joint forming material of the parent invention may
be a filled solder composition or a supported solder, which will
retain its shape upon the solder melting or reflowing. As used
herein the term "filled solder~' means a solder material which
contains a filler which prevents a shape of the filled solder
from changing substantially in dimensions when the temperature
of a preformed shape of the filled solder is raised to or above
the melting point of the solder. The filler comprises discrete
particles or filaments which are solid at temperatures at which
the solder is molten. The filler is present in an amount suffi-
cient to substantially maintain the preformed shape of the filled
solder when the solder is molten. The filler may be particulate
po~der or filaments such as discreet len~ths of wire or may be
a mesh




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or "~ool" of continuous or intern~ixæd fila~nents. P~eferably
the fill~r is electrioslly conductive and Isost pre~erably is
a metal. The QmOunt of ~iller present is that which is
sufficient to maintain the pre~ormed shape of the filled
solder~ such as a column, when the solder is melted or
reflow~d. Ihe amo~nt i5 generally from about 20Z by weight
to about 80~ by ~eight based on the total weight of the
solder-filler ~ixture, preferably from about 25~ to about
7~, more preferably from about 30~ to about 60~, and most
lo preferably ~rom about 35Z to about 4~0~.
As used herein the te~m "supported solder" means a
solder preform shape which is supported by a support strand
or tape which is disposed about the outside of the solder
preform shape. The support strand or tape must be solid at
temperatures at which the solder is molten and is disposed
about the outside of the preform shape in a pattern whereby
the shape of the solder is substantially maintained through
the surface tension of the solder when the solder is molten.
The pattern in which the support strand or tape is disposed
and the spacing, angles, etc. of the pattern will depend on
the cross-sectional dimension of the solder preform shape,
on the height of the preform shape and on the solder composition
due to its apparent surface tension relative to the support
strand or tape material. The pattern may be a spiral wrap of
~5 tape or wire, a braid of wire or the like, wherein the
spacing, for example between the spiral wraps will be
gp-v-erned by the above factors. In gener~l, the supported
solder shape will be a column type shape suitable for
~; connecting electrically conductive elements.
~o As used herein the term `'column" means a shape which
c~n form g connertion between electrically conductive
elements. In general the shape will be cylindrical where
the length or height of the column is grester than its
cross-sertion di~ension berause thi- ~onfig~rstion provides

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1~6~5~ MPOB64




ease of ~anufacture and interconnect flexibility for thermal
expansion of the electrically conductivlE elements. ~he
column may be straight~ curved, S-shaped, C-shaped, spiraled,
etc. The term "column~ also used herein to include
5 shapes wherein the length or height is less than the cross-
sectional dimension and ~ny cross~section shape suitable for
connecting electrically conductive elements where the
distsnce between the elements is greater than the distance
used for conventional capilary flow soldering. The "col~mn"
lo need not be of uniform cross-section dimension, but May vary
for flexibility or other ressons, e.g. an hour-glass shape.
As used herein the term "solder" means any conventional
or specifically formulated material for forming connection
between elements by melting ~nd freezing. Solders are well
known as exempli~ied by the Kirk-~thmer Encyclopedia of
Chemical Technclogy, 3rd Edition ~19B3), Vol. 21, pages
342-355.
As used herein, the term "spertures" means holes in or
through the retsining member. Usually the holes will
extend through the retaining member so that the preform of
joint-forming material may be plsced therein and be exposed
; at both ends or have both ends extending from the retaining
member to form a connection with an electrically conductive
'e'lement. However, the apertures may be holes in the side or
L5 edge of the retaining member ~hich receive a portion of the
preform and hold the preform for proper positioning to form
sn electrical interconnect. These various configurations
are illustrated heiein.

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The various aspects of the present invention may be
summarized as follows.
According to one aspect, the invention provides a
solder comprising: solder; and disposed in the solder a filler
comprising discrete particles or filaments which are solid at a
temperature at which the solder is molten, which are present in
an amount of from 20% to 80% by weight based on the total weight
of the solder-filler mixture, and which are of sufficient size
and density substantially to maintain the solder in a preformed
shape when the solder is molten.
According to another aspect, the invention provides a
solder column for forming electrical connections comprising:
solder; and disposed in the solder a filler comprising discrete
particles or filaments which are of a material which is solid at
a temperature at which the solder is molten, and which are present
`~ in an amount sufficient substantially to maintain the column-like
shape when the solder is molten.
According to yet another aspect, the invention provides
a solder column for forming electrical connections comprising:
solder; and disposed about the outside of the solder a support
strand or tape which is of a material which is solid at a tempera-
ture at which the solder is molten, and which is disposed about
the outside of the solder in a pattern whereby the column-like
~;~ shape of the solder is substantially maintained when the solder is
molten.
According to still another aspect, the invention pro-
` vides a method of making a columnar solder preform, which
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- lla - 26775-71D

comprises:
(a~ providing a solder wire; and
(b) providiny a support strand or tape disposed about
the outside of the solder wire such that the shape of the preform
is substantially maintained by surface tension when the solder is
molten, the material of the support strand or tape being solid at
a temperature at which the solder is molten.
According to a further aspect, the invention provides a
method of making a columnar solder preform, which co~prises:
(a) providing a preformed support in the form of a
spiral wrap or a braid of a strand or tape,
(b) immersing the support in molten solder which is at
a temperature at which the material of the support is substantially
solid; so that solder fills the support; and
(c) removing the support from the molten solder;
the support being such that solder is substantially maintained
wlthln it when molten by surface tension.
According -to a final aspect, the invention provides an
assembly of at least two electrically conductive elements, each
having at least one contact, and a columnar solder preform which
extends between the contacts forming an electrical connection
between them, the preform comprising a support in the form of a
spiral wrap or braid o~ a strand or tape J and a quantity of solder
within the support, the support being such that the solder is
substantially maintained within it when molten by surface tension~
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Various embodiments of the presen~ i~vention will now
be described by way of example with reference to the
accompanying drawings in which:

Figr 1, labeled Prior Art, represents, on an enlarged
scale, a solder joint between a chip device and a circuit
board formed in accordance with existing techniques;

Fig. 2 is a showing similar to Fig. 1, illustrating
a joint formed with the column-type connection;

Fig. 3A is a representation of the column of Fig. 2
as a cantilevered beam fixed at one end and showing the
force acting on it for the purposes of considering the
; resultant displacement and stresses;

Fig. 3B is a representation of the column of Fig. 2
:~ as a beam fixed at one end and guided at the other and
deformed as a result of the relative movement of its ends;

Fig. 4 is a perspective view of one embodiment of the
preform placement device of the present invention showing a
plurality of column-type solder preforms mo~nted in a
retaining member in the form of a perimeter type carrier
element;
~~
Fig. 5 is an elevational view showing one of the column
preforms illustrated in Fig. 4;
.

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Fig. 6 is a cross-sectional view along line ~-6 in
Fi~. 5 showing a column preform containing a filler to
maintain it~ col~mn-type shape;

Fig. 7 is an elévational cross-section showing the
preform placement device of Fig. 4 positioned between two
structures to be joined, prior to the soldering of the
connections;

Fig. 8 is a showing as in Fig. 7, after the solder
connections have been formed and the retaining member of
the preform placement device has been removed;

Fig. 9 shows another embodiment of the present invention;

Fig. 10 is an elevational view, in section, showing the
placement device of Fig. 9 in position after the solder joints
have been formed;

Fig. llA-C show alternative configurations of the solder
prefvrms useable in connection with the present invention;
:' :
Figs. 12 and 13 show additional configurations for the
solder preforms as well as alternative aperture configurations
in the retaining member; and

Figs. t4A-D show embodiments of supported solder columns
- of this invention wherein Fig. 14C shows column after the
solder joints have been formed and the retaining member
~: removed.


:

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, .. ~ :
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,


-14-

In the ~es~ript~on herein, the solder iDining of a chip
~arrier package, which is re~erred to hereafter as a "chip
device" or a "chip carrier", and a circuit board is used as
an illustrative application of the present invention. The
joining of other electronic components is also comprehended,
and the invention may be employed wherever and whenever a
solder connection of i~creased reliability and longer life is
desired.
Referring to the drawings, and more particularly to Fig. 1,
a joint or connection made 'in accordance with techniques
known in the prior art is shown formed between a chip device
10 and a circuit board 12. The chip device 10 has a plurality
of electrical contacts which may be disposed along its edge.
Only one contact area is shown for the sake of simplicity.
The circuit board 12 has a plurality of complementary contact
areas on its surface ~only one shown). The circuit board 12
may be a printed circuit board (PCB) or a printed wire board
(PWB), and may be referred to hereinafter simply as a ~board"
~; or "circuit board." In a known fashion, the chip device will
be disposed above the surface of the circuit board such that
- the contact areas are vertically aligned and mechanically and/or
' electrically joined, such as with a solder connection. In the
illustration of Fig. 1, the opposed, facing surface of the chip
device 10 and the circuit board 12 is provided with a layer 14
of conductive material, such as copper, and these layers
~re interconnected with a suitable solder composition 16,
which may be of known tin-lead alloy.


:~ .




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~21~9~

-15-

As noted above, a s~ld~r connection 5uch as shown in Fig. 1
is subjected to s~resses in~uced by thermal and mechan~cal
forces. These stresses are the result of strains produced by
mechanical deformation, differences in temperature between
the chip device and the printed circuit board and/or differen-
- ces in the thermal coefficients of expansion between the chip
device and ~he PCB. For example, ~hermal stresses may result
from power cycling even when the materials of the chip device
and circuit board do not exhibit any differences in the
coefficient of thermal expansion, but because of the power
applied to the chip device, a temperature diEferential exists
bet~een the chip device and the circui~ board.
It can be seen that as the connection is subjected to
repeated heating and cooling cycles, it will ultimately fail
due to fatigue, and the connection will fail earlier if the
stresses induced therein are high. Therefore, to prolong the
life of the ~oint and to increase its reliability, the
resultant stresses therein should be reduced. In order to
determine how the stresses can be reduced, the factors
governing the creation of the stresses in the joint should
be considered.
- In Fig. 2 a column type connection 18 is illustrated
and Figs~ 3A and 3~ illustrate the relationship between the
deflection F for a given column of height H and diameter
D for a given forces F. As will be apparent, the column
t~p~-connection will have a longer life due to better
withstanding of~stresses. The selection of hei~ht and
diameter will be determined by a number of factors of
-~ size and materials. A detailed finite element analysis
of similar joint structures was presented by E. A. Wilsonr

.,


~ .

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.~

` `'` '' ''

-16- 26775-71

Honeywell, Phoenix, Arizona, and E. P. Anderson, Honeywell,
Bloomington, Minnesota, in their paper entitled "An Analytical
Investigation into Geometric Influence on Integrated Circuit
Bump Strain," which was presented at the 33rd Electronic Components
Conference, May 16 18, 1983, in Orlando, Florida IProceedings page
320-327). This analysis confirms the advantages of columnar
structures.
It is understood that by reducing the peak stresses as
described above in a repeti-tive loading situation, the number of
cycles required to produce failure is greatly increased.
From the foregoing evaluations, it can be seen that
the life of the solder joints can be increased substantially by a
relatively s~all increase in solder joint height. Likewise, a
reduction in solder joint diameter will extend the life of the
solder joints. A concomittant advantage in using joints of in-
creased height and/or reduced diameter is the opportunity for
increased packing density. The foregoing evaluations are helpful
ln predlcting the general properties and performance to be expected
from the devices and methods of this invention. However, it is
a1so helpful to verify performance properties by empirical testing
of the devices of this invention.
The foregoing advantages of reduced stresses and
extended life in the solder joints and the opportunity for
increased packing density are-incorporated in the present inven-

, ~ tion which provides a device for the precise positioning of
solder preform of slender cylindrical shapes at predefined
locations. In the embodiment of the invention illustrated in
Fig. 4, the interconnectlon preform placement device 20



' .

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' ' ''; :

~P~a6

. -17-

includes a ret~ining member 22 o~ ~lectric~lly nonconductive
materisl h~ing a ~onfiguration ~nd size ~ub~tantislly the
8ame as the chip carrier f~r whi h the prefarm placement
device i~ u3~d in mo~nting the chip carrier on 8 3uit~ble
substrat~, such aa a circuit board. The holder 22 has a
central cut-out Z4 to form-~ perimeter or bordering portion
in which ~re Rp~ed et predetermin~d locati~ns a plurslity
of holos 26 which receive preforms 28 of solder in the shepe
of slender cylindrieel columns, such ~ sh~wn in Fig. 5.
~0 The ret~ining member m~y ~150 herein be referred to e9 a
"holder."
~ The location and positioning of the holes 26 on the re-
: tsining ~ember 22 ~re determined by the spac~ng of the con-
ductive contscts disposed on the edge of the chip cerrier tD
~5 be ~ounted1 Gener~lly, the height of e~ch solder preform 28
. ~ill ba aomewhat taller than the thickness of the ret~ining
; ~ember 22 auch thot the upper and lower edge portion~ of each
aolder preform 2~ will extend above the corre~ponding surfaces
of the retaining member, ~nd in uae these exposed surf~ces
: ~O will make physical contsct with the corresponding conductive
p~ds on the chip carrier and on the circuit board~
hile not pecifically ~hown in Fig. 4, the preform plsce-
ment device i8 provided with appropriate meanY for properly
locating and orienting the reteining member 22 with respect to
2s the chip carrier ond the circuit bDard 80 that the conductiYe
pad3 on the chip c~rrier, the conductive p~ds on the circuit
~ board and the column solder pre~orm~ ere properly ~ligned~
Such locating ~eane are kn~wn, and m~y include a chQmfered
oorner which m~te~ with ~ similerly-configured ~urfscP on



.



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: : ::: : .

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MPOB64


..
the ohip carrier. One cr ~ore of the corners m~y h~ve an
indexing notch~ Additionelly~ alignment pins may be provided
on the bottom ~urf~ce ~f the ret~ining member 22, sr hDles
to accept pin~ ~hioh regi~ter ~ith positioning hole~
provid0d on ths circuit board. A combination of s~ch
pnsitioning techniques ~ay be incorporated into the holder
2~.
It i~ possibls to v~r~ the composition of the ~older
~aterial ~uch that the solder preform will give or rompress
under the weight of the chip carrier to be mounted. This
compressibility of the solder preform i8 important becau~e
the chip carrier ~nd the circuit board are typically not
truly flat 80 that the length~ of the solder columns must
chsnge during the soldering proces~ to eccommodate the~e
irregularitie~.
The retaining member 22 may be made from any suitable
materiAl, and prefer~bly is of an electrically-nonconductive
.material. The material may be a ~ingle sheet or lay0r of
desired thicknes~, or may be 9 lamin~te of 8 plurality of
20 thin sheet~ or lsyers of suitable meterisl or may be A
~lurolity of elements which form a sheet-like structure~
Such material ~ould include, but is not limited to, glass
matt and high-temperatur0 polymerio materials such B9
Ultem~(Ultem is a trademark of General Electric Company.).
~5 The m~terial nf the retaining ~ember 22 should be sufficiently
rigid and temperature-re~ist~nt to maintsin the solder
~ preform's position during the soIdering procea~.
-~ Preferably there ~re t~o cstegorie~ of reteining
member~, those th~t are removable and those thet beco~e a
~o perm~nent part of the interconnection. The remov~ble type
could be dissolvable, fr~ngible, ~egmented, or defDrmable
without harming the prefor~. The permanent ar nonremovable
., .
type can be p~ive or can perfQrm electric~l, mech~nical
~nd/or therm~l functions. The removable type cen therefore


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MP0864



be destroye~ by dis301Ying or breaking apsrt. Th~ 9108s
~stt e~bodiment can be phy~ic~lly pulled away in ~hole or
pieoe by piece. ~he Ulte~ materi~l csn be dissolved by
~ell-known chemical ~esn~ without harmirlg the preform
or electrical ly conductive elements.
It is ~ithin the scope of the invention to makP a
aegmented retsining member that can be ~tripped away aFter
interconnection. The retaining me~ber 22 in Figure 4 can be
provided with lines of weakness ~r cuta æs iehown Bt 29 in
~o ph~ntom line. In thie ~sy, the retaining ~ember 2~ may be
removed in one or ~ore pieces end directions. The retaining
member may el80 originally be made from individual elements
as will be discussed later.
Thus it con be eeen that the removsble retaining member
~5 may also be conductive such a8 an aluminum foil in order to
maintain the position of the preforms during interconnection.
It is important that ~uch 8 ret~ining member not bDnd to the
prefor~ during the process.
Finelly, the reteining member cQn be mede from a thin
heet nf ~older material which could melt end flow into the
~older-like pref~rms during the soldering procs~s.
The reteining member which remains in place should be
generally nonconductive and relatively flexible 80 that it
doe~ not interFere with the motion of the preform columns.
~5 Additionslly, it may provide ~n impedence-metched interconnec-
~ tion if it is o combinetion of conductive ~nd dielectric mate-
;~ rial ~o that it provides ~ trensmissiDn line or microstrip
offect, or s coaxi~l type shield eround the preforms.
In another ~mbodi~ent the reteining member could be made
from ~ noncondutive materisI ~hich, ho~ever, becDmes conduc-
tive ~hen ~ specific voltage threshold is exceeded, this
ShreshDld being just ~bove the normal operating voltage of the

`::



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MPD864

-2~-

~ircuit. Thi~ type of' ret~i~ing member ~ould provide protec-
tion to the chip device by ahorting DUt any potenSially dam~-
ging tr~nsi0nt overvoltage ~hieh m~y result from electro-
~tatic di~charge or other electrical f~ults.
In 30me ~pplications, it ~y be desir~ble to m~ke the
retaining member from a ~terial which exhibits heat-recovery.
T.his type of retaining member could be reinforced ~ith gla~s
fibPr or the like ts control ~t~ coef~icient of thermal expan-
3inn, but locally the holes which are provided for ret~ining
the ~older-like oolumns could be fabricated B0 ea to ountract
in diameter during soldering and thereby extrude the solder
column up to neet the CCP ~nd PWB.
Although the retaining member has been ~hown to position
only interconnection preform~ in Figures 4 snd 7-10, it i8
under~tood that other element~ ~ould al80 be pnsitioned by the
retaining member ~nd attached to the chip devire and board. A
heat-sink device could be csrried in the central opening of
the retaining ~ember oF Figure 4 and bondsd to the CCP and PWB
during soldering. 5imilarly~ ~ vibration damper, structural
reinforcement9 or a Peltier type cooler could be po3itioned
~nd attached to the CCP ~nd the PWB. Al~o, fln electricfll
ground plane could be positioned near the interconn,ection
preforms to benefioially ~odi~y their electronic impedence
ehar,~.cteristic~ similar to ~ microstrip board trace.
Figure 4 shows 8 square periphersl srrsy of intercon-
n~ction~. However, other p~tterns or arrBy~ could ~130 be
ac-oomplished by this invention. Any m~trix of intercon-
nections on ~ regular rectiline~r form~t could be provided.
Non-rectilinesr or psrtially filled arrsy~ c~uld olso be
prov~ded.

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MP0864



lf the interconnection3 are arranged suffici~ntly
~lo~e together, a random-type interconnection 8y8tem could
be produced. In this type of syRtem, since the intercon-
nection density i~ much higher than the density of the
pads o~ ~he ~CP Qnd PWB~ then ~tatistic~:Lly there will
~lways be ~t lea~t one interconnecting preform loe2ted
between each pad set to be interconneet~d. The arr~ngement
of the interconnection~ i8 completely random in this type of
holder sy~tem. This type of retaining member mcy ideally be
msde from a plur~lity o~ element~ bonded together, esch
hAving at least one ~perture therethrough. The elements,
such as 31 shown in phantom in Fig. 4, ~ay be of uniform or
random cross-~ection in order that they msy be efficiently
b~ndled and permanently or temporarily joined together such
lS as by fusion or proper adhesive materisl to form n sheet-like
~tructure. In ~uch n bundled configuration the reteining
. member elements may be formed by continuously extruding the
- retaining member material over the preform, cutting the
extruded composite into discrete pieces, bundling the
~ 20 axi~lly-aligned pieces and prafer~bly joining the ret~ining
:~ member ~aterial nnd then ~licing the assembly st right
angles to the axial alignment to make a preform placement
device.
Also ~hown in the configuration shown in Fig. 4, the
retaining member 22 csn be ideally stamped from 8 sheet of
~ateriAl, or othsrwi~e cut from sheet material. Quite pos-
~ibly the ret~ining member f~bricating proeess would provide
for the oimultaneous eta~ping of the holder ~hape and the
central cut-out 24 ~nd form~tion of the properly_spaced
3~ hole~ 26~ and insertion ~f the solder preforms into the
holes. Of course, it is pos3ibIe that the production of the
retoining member 22 c~n be ~chieved in ~ sequence of steps

.



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MP0854

-22-

in ~ h the ~ ining ~ember with it~ cut-out end orienta-
tion a~rfsces i8 st~ped ~ro~ a ~heet ~aterial, ~nd aubsequent
techniqu~s are ~sed to form the hol~ into which the solder
preforms ~re inserted. Other ~anuf~cturing ~ethods such as
molding or in~ert molding ~re within the seope of the
invention.
The retaining member ~2 m~y be fabricated ~rom a ~heet or
a l~minate of he~t recover~ble m~terial, whereby the retainlng
member is ~tamped from the m~teri~l sheet, the holes formed
D therein, Rnd the solder preforms positioned within the holes.
~ubsequently, the reteining member i8 he~ted to a temperature
sufficient to oause the ~aterial to recover such that the
diameters o~ the holes 26 are reduced, but ~t a temperature
below the melting point of the solder preforms. Ihe use of
a heat~recoverable material ~or the retsining 22 affords the
odvantages that the holes csn be form~d to a predefined ~hape,
~uch 88 ~n hourglsss, with vsrying diameters, such that the
diameter of the middle section is smaller thsn the diameter
at the ends. These holes would be expanded to a unifor~
~o diameter l~rger than the diameter of the preform~ so that the
preforms car~ be more readily positioned in the holes, after
which the ret~ining member 22 i8 heat-recovered, causing each
hole to constrict to r size ~ubstantially identical to the
diameter of the preform, thus securely gripping the preform
within the retaining member. Furthermore, the use of a heat-
rec-o-Yerable materi~l sffords the sdvantsge that in ~se, when
heat i~ applied to effect the sDlder joint, such ~s by a
~older reflD~ process, the ~irm gripping o~ the solder pre-
froms by the heat-recovered ret~ining member material will
~o i~p~rt the origin~l hourglass sh~pe of the holes to the
preform, thus improving the flexibility of the ~olumn-type
joints, Dnd in turn reducing the ~tresses ~nd improving the
relinbility of the joints.

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MPOB64

-~3- .

~ t i~ D posaib~e to further control the ulti~ate con-
figur~tion of the solder joint by the u~e Df ~ he~t-recoverable
~teri~l in th~ retaining me~ber 22. This can be ~chieved by
p~rtially recovering the material, causing the holes to
securely ~rip the pref~rms. ~hen, during the soldering
process, su~ficient heat i8 applied to cause the material of
the retaining ~ember to further recover, thereby further
decre~ing the dismeter of the holes to apply a con~trictive
force onto the moltsn or ~oftsned preForm. Thiæ will have
o a ten~ency to produce column joint~ of height greater
than the thickneRs of the retaining ~ember 22.
While the ret~ining member 22 has been shown in F:lgure
4 ~s a perimeter conFigur~tion, it i8 possible th~t the
retaining member csn be a layer of ~aterial without ~ny
out-outs therein, and in which the nece~sary number of
solder preforms are properly locsted throughout the entire
~ ~urf~ce of the retaining member ~8 nece~sitated by the
: number, looation and configuratisn of the conductive
pad~ to be joined.
The preforms 28 ~ay be made of sny suit~ble joint
Forming m~teri~l, such ~s ~older, filled solder, ~upported
solder or conductive elsstomer materiel which wll at lesst
p~rtially melt or ~often then adhere to an electric~lly
conductive element when contacted therewith ~nd coo1ed.
The preform~ can be produced by any suitable technique, 3uch
A8 b-y---the oontinuous extru~ion of the ~older m~terial
thr~ugh appropriate-sized die~ snd cutting the extrud~te to
the proper lengths. The preforms m~y be molded. Filled
solder i8 u3ed to ~intain the columnar configur~tion during
the solder~ng process; particles of metallic or ncn-metallic
aterial may be embedded in the solder pre~orm~, ~uch 0s

''




.
.:.

-24-

shown in Fig. 6 For examp~e, discreite pieces 30 of metallic
material 5 such as pieces of copper, may be embedded in the
solder preforms by mixing the particles in the composition
prior to extr~sion7 ~nd then extruding the mixt~re in a
known f~hion. ~s ahown in Fig. 6~ the discrete particles
may be ~ligned along the longitudinal 8XiS of the extrudate.
This alignment c~n be achieved with appropriate techniques,
such ns the ~pplication of a magnetic force during the
extrusion process, or simp~y by the shearing and other
~o forces applied by the extruder on the extruding material.
The particles mixed into the ~older should have a
melting point above the melting point o~ the solder, and
good metallurgical, mechanical and electrical properties.
In addition to copper, discussed above, Fillers could
include nickel, iron, ~nd metsl-coated high-temperature
polymer or glass films with a high espect ratio. These
materials could be discrete particles or continuous lengths
with 8 slngle strsnd or many strands in each preform.
Solder could completely coat the strands or fibers, or could
Xo be deposited only at the ends of inherentIy conductive
fibers~ Additionally, the interconnection bonding agent or
solder could be added in a separate operation. Thus,
continuous conductors or fiber bundles coùld be retained by
t~e retaining member and then attachment would be accomplished
~5 by immer~ing the assembly in molten solder which will wick
an~ wet the components and make the electrical and mechanical
interconnection.

'`'

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MP0864

-25- .

~ dditionally, the p~rti~le~ in the filled ~older may be
oriented in ~ny other de~ir~ble nlignment, ~nd the rel~tive
content of the psrticles in the solder preforms, ~8 well QS
the ~ize ~ the p~ticles r~l~tive to the height of each
preform, csn be tailored to the requirement~ of the joints to
be for~ed. Furthermore, ~he ~urfaces of the solder preforms
~ay be coated with 8 suitable flux, or the flux msy be coated
only on the end portions of.ths pre~or~ ~o that during the
soldering proceæa the flux will coat the respective cont~ot
areas on the oonductive pads to ~nsure proper flow of the
001dPr. The flux m~y æl30 be incorporated ~ithin the preform.
The use of the preform placement device 20 in mounting
a chip carrier 32 to a suit~ble substrate, ~uch ~8 a circuit
board 34, iB illu~trsted in Figs. 7 and B. The ret~ining
member 22, ~ith the sol~er preform 2~ secured therein, is
positioned between the lower ~urf~ce of the chip carrier 32
~nd the oppo~ing upper surface of the circuit board 34, and
properly loc~ted 80 that the snd portions of ~ach solder
preform 28 m~ke contact ~ith the conductive contacts on the
2~ chip carrier ~nd the conductlng land on the circuit board ~4.
~ Means may be provided For aligning or orienting the chip
- carrier 32 relative to the circuit board 34, such a8 by
providing ori~ntation hole~ 36 in the chip carrier which ~re
vertically ~ligned ~ith oorresponding holes 3~ in the
~5 GirCuit board end hDles 39 in the pr~form placement devic~
by inserting pins through the eligned holes 36, 3~ and
39. Other alignment or orienting me9n8 can be used. After
~ thz soldering process, the ends of the colu~n solder preforms
;~ 2~ ~re ~ecurely bonded tc thsir respective condu~tive
DntaCts ~nd l~nd~ on the chip carrier ~2 ~nd the circuit
boerd }4, aa shown in Fig. B.

~: '




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MPOB64

-26-

Fi~ure 4 illu~tr~te~ e ~at ~temped retaining member
but, ~f cour~e, the holder eould be formed by et~mping~
folding or molding in~o ~ cup shaped s~ructure into ~hich
~h2 ~CP could be accur~tely plcced. Detznt features could
be provided a~ pres~ure-sensitive or hot-melt adhe6ives
~ould be pro~ided ~ithin the rstaining meinber sa th~t the
ohip e~rrier eould be prea~sembled to the CCP before
application to the PWB. This subassembly could then be
locnted to the PWB u~ing fixtures, pick and pl~ce equipment,
elignment features ~uch as holes or pins, or the like.
Adhesives or pinfi could be provided in the center ~urf~ces
o~ thi~ retaining member as di~cu~ed e~rlier with respect
to Fagure 4 to maintain po~iticn during the ~oldering
or reflowing operation.
~5 Figure 4 illustretes a single retaining member but, of
cours~9 these components could c~nveniently be ~upplied
oonRected together like a bandolier for convenient assembly
packeging and ~pplication.
During the soldering or reflowing process, it i~
underst20d thot suitsble ~ean~ will be utilized to maintain
good cont~cts bet~een the oonductive elements on the chip
c~rrier 32 and the circuit b~rd ~4 until the ioint has
~olidified. Techniques for meintaining this cont~ct ~re
known. Another technique ~or providing this retaining force
: ~S .i8 chown in Fi~s. 9 and 10 ~nd esn be incorporated into the
ret~ining member ~or the 801der pr~forms.
A~ shown in Fig. 9, ~n illustrative number of solder
preforms 28 ore dispo~ed in holes prDvided in the ret~ining
~e~ber 40 which is made from ~ l~yer of heat-recov`er&ble
~o material, and e~ch gurfuce ie formed with a depre~sion or
recess 42. Form~tiDn of the re e~s 42 ceu~0~ the opposite
~urface nf the ret~ining member to be raised in ~ correspond-
ingly-shaped protrusion or bump 44. The elev~ted planar




, ~ '
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MP0864

-2~-

surf~ce of the pro~ru~ion 44 i8 c~ated ~ith a ~uit~ble ~dhe-
sive 46. ~he r2ce~aes 4~ and the protrusion~ 44 ~n be con-
voniently for~ad by c 8tamping OpBratiOn in ~hich appropri-
~tely-shaped dies are presaed onto the opposed 8urfsce3 of
the holder 409 ~eusing recesses 42 to be formed in one sur-
face and forcin9 the m~terial out in the form of protrusion
44 Dn the other surface, as ~hown more clearly in the cross-
~ection of Fig. 10.
Once ~pplied between the chip csErier 32 and the circuit
io boerd 34 9 the end portions of e~ch solder preform~ 28 m~ke
contact with the conductive elements 1~ ~nd 12 on the chip
carrier and circuit bo~rd, and the adhesive 46 on the sur-
f~ces nf the protrusion3 44 make contact, re3pectively, with
the opposed surfaces of the chip carrier and the circuit
bo~rd, thus holding the chip ccrrier to the circuit board.
During the ~ldering proces3, the upplicat.ion of heat causes
the heat-recDverable material of the retaining me~ber 40 to
recover in ~ known ~a hi~n, cau~ing the recesse~ 42 and the
protrusions 44 to revert to the f~at configur~tion of the
~o retsining me~ber, thu3 pulling the chip carrier 32 to~ard
- the circuit board 34 and cau ing the solder to wet the
contact element~ on each re~pective device.
The ~hspe at the rece~ae3 ~nd protru~ion~ ~ho~n in Figs.
9 ~nd 10 ere illustrative only; other configurations may be
equally suitable. The trapezoidal configuration of the
~ece~3e~ 42 and protrusions 44 shown in the drawings are
; particularly advantageous in thet they provide ~ relatively
rge fl~t~surf~ce onto ~hich the cdhesive 46 may be applied,
~nd the form of the reces3e~ ~nd protrusions c~n be easily
de in the retaining member 4a. In u~e, the l~rge-area
adhe~ive layers prcvide 8 ~trong gripping ~orro to the
`~ re~pective surf~ces of the chip csrrier ~2 and the circuit
board 34~ ~nd the contractivs ~orce produced by the recover-
ing m~terial of the retaining member 40 exertB 8uf~icient


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MP0864

-2B-

-foree to pull the chip csrrier down teward the ~ir~uit board
34. The shapeR ~l~o aid in venting bet~een chip ~nd board.
ObYiously, ~dhesive c~n be put ~s ~ell on flat ret~ining mem-
bers, without any protrusions9 simply to secure the deYice
S on the bosrd and the CCP on the d~vice ~with or ~ithout
hest-shrinking) or for vibrsticn damping, etc., as discussed
earlier.
Although the ~older pre~orms considered thus f~r h~ve
been of ~lender cylindrical configurations, other
o gh~pes ere equally ~uitable, depending upon the requirements
of the mounting. Preforms ~ith BqUare~ hexagGnal cr other
~hapes of cross-~ections can be u~ed.
Furthermore, some examples of other configurations are
shown in Fig~. 11A-C, Fig. 12 ~nd Fig~ 13. The S-nhnpe of
the preforms shown in Figs. 11A-C prDvide~ joint~ of greater
flexibility which permit relatively large displ~cements
between the chip carrisr 32 snd the circuit board 34 without
inducing undue stresses in the fixed portions of the joint.
With the reverse S-shape preform 4B shown in Fig. 11A, a
~ subst~ntially l~rge contact ares is af~orded et the upper
: portions Df. the prefcrm making cont~ct with the conductive
pads 10 snd 12 on the chip carrier 32 and the circuit board
34. The preform 48 i8 supported by two parallel-disposed
.~ holder l~ers S0 and 52.
2~ The 5-sh~ped preform 54 of Fig. 11~ affords the same
~dvantages as the prefor~ 48 of Fig. 11A end, ~dditionally,
provides two probe areas P and P which may be used to
test for electrical continuity of the connection. This
configuretion ~s perticulsrly ~dvsntageous ~hen u~ed
~ in ~aking connection~ slong the periphery of the chip
~; carrier when the contact~ ~re spaced elong the edges o~ the
chip carri~r innsmuch a8 the probe areas sre re~dily access-
ible. As with the prefnrm 4B, the preform 54 is aupported


`

-~9- 26775-71 V
by parallel-disposed retaining member layers 50 and 52. In
fabricating the preforms 48 and 54 and positioning them into the
retaining members 50 and 52, the preforms are initially straight
elements which are inserted into the corresponding, vertically
aligned holes in the retaining member layers 50 and 52 and the
ends are bent into the configuration shown in Figs~ llA and llB.
The S-shaped preform 56 shown in Fig. llC is provided
in a single retaining member layer 58 having a thickness substan-
tially greater than the individual retaining member layers 50
and 52 shown in Figs. llA and llB. Otherwise, the preform 56
affords the same advantages as the preforms 48 and 54.
The preform 60 shown in Fig. 12 is of C-shape configur-
ation which is suitably attached along the edge of the retaining
member 58 by element 61 being inserted into the aperture in
member 58. Due to its uni~ue conEiguration the C-shape preform
60 is most advantageously used when disposed along the peripheral
edges of the retaining member 58. The preform 60 provides a very
substantial joint surface which may be used to test for lectrical
;` continuity between the chip carrier 32 and the circuit board 34.
Although the preforms have been generally described as
being made of filled solder the preforms may also be made from
: :~
supported solder or from a continuous length of conductive material
such as wire with filled solder or supported solder material
located at the ends thereof for interconnection purposes. In some
methods the preforms may be solder or conductive elastomer. These
materials may also be a continuous strand of conductive material
with filled solder or suppor~ed solder column located at the ends
thereof for interconnection purposes as will be appreciated with
;




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-29a- 26775-71
respect to Figures 11-13.
For maximum flexibility and resilience between the chip
carrier 32 and the circuit board 34, the coiled spring




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-~confi~uration 62 ~h~n in Fig. 13 î~ id~al. ~he preform 62
~ould be readily formed by sxtruding the filled ~older
co~po~ition as a continuoua extrudate, forming it into ~
coiled configur~tion of ~uit~ble ~pring msterial of de~ired
di~mete~ and length~ nnd appropristely holding each spring
prefor~ within the ret~ining ~mber 58. The degres of
reailience ~ffDrded by the preform fi2 oan be controlled in
~ubstantislly the ~sme fsshion th~t the parameters regulating
the performsnce of conven~ipnal springs ere controlled, such
as oontrolling the diametric 8ize8 of each turn of the
spring, the length of the spring and th~ dismeter of the
extrudate from which the spring i8 made. The spring
configuration could also be made from a supported solder
disclosed horein.
Since each solder preform i8 individu~lly pl~ced in
s given location, the preform configuratlon can be tailored
~ to meet the specific requirements of a psrticular joint.
; Thus, for ex~mple, the diameter and/or height of the
eylindrical preform at certnin locations c~n be different
from the pr~forms at other locations to meet the specific
n~ed~ of the joint being formed. Conceivably, each joint
may be unique snd mey incorporate ~ different solder preform.
Additionally, it i8 possible to co~bine different preform
configuration~9 such as combining the cylindric~l pre~orms
with ~ny of the preform3 ~hown in Figs. 1t-13 tD meet the
~pëclfic needs for re3ilience and stress reduction in one or
ore particuler solder ~oints.
-; Fig. 14 show~ ~o~e exa~plss of the supported solder
preform embodiment of this inv~ntion. Fig. 14A sho~ a
~o ~older column supported by ~ire ~trands in the form of s wire
breid 72. Fig. 14~ ~hows the ~olumn ~upported by ~ ~ire
str~nd ~2 wrapped around the column in a spir~l f~shion. In
the ~ire braid and the ~pir~l ~ire wrap e~bodimen~s, the
diameter ~f the eolumn and the ~p~cing between the wires are
~5 aeleet~d ~o th~t the surf~ce tension of the ~older used




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MP0864


relotive to th~ wire us~d ~ill maintain the ~ub~tsntially
columnar ah~p2 of ths sDlder ~hen ~olten, Fig. 14B showa a
~upport~d solder oolunn 91 u~ing ~ met~l tnpe or ribbon
92. Fig. 14C shows the 3upported solder column sfter the
connection h~ been ~nde ~herein it can be sBen that the
cDlumn sh~pe of the ~upported solder has been substanti~lly
~aintained ~hile the solder formPd fillet~ 94 at interconnect
pads 10 ~nd 121 The solder in the supported solder column
flow8 ~lightly to form the fillets ~nd the colu~n scts a8 a
~o reservoir of solder which i~ slightly depleted 8~ 6een ~t
~illet 95 between the tape support. This characteristic of
the supported solder columna provides manufacturing proceRs
advantages ~8 ~11 as columns of improved ~lexibility. An
example of ~uch a tape found particularly useful For interconnect
l$ pads sp~ced on 0~050 inch centers i8 a copper tape 0.003
inch thick end 0.013 inch wide wrapped around a salder
column 0.020 to 0.025 inch in diamete~ with 0~008 ts 0.01
inch ~pace between wraps of the tape. It should be noted
thst the suppDrted solder columns may be ~ade using filled
20 ~older in p1ace oF the conYentionsl ~older.
~ he suppDrted aolder can be made by applying the
upport ~trand or tape to the outside of e column of solder,
e.g. a solder wire. In this method support strands c~n be
braided ~r ~rapped around a solder wire and the wr~pped
2s solder wire thsn cut into length to for~ column~ of a
d¢sir¢d dimension usefui in this ~nvention. Similarly
~thl tape oan be wrapped around t~e ~older ~ire ~nd the
wr~pped ~older ~ire cut to de~ired length~. The supported
solder can al80 be m~de by dipping the pre~ormed ~upport;
uch as ~ wire brnid or ~ ~piroled wire or tape, in molten
~older tc fill the interior ~psce in the support ~ith ~older
then ~olidifying the ~older. This method c~n likewi~e be done
in long 8~Ction8 which sre then cut to lengths required to form
the columns u~eful in this inventiGn. In thiE; fashion the
35 supported solder columns cen be formed in situ in the reteining


,
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-32-

~ember o~ thi~ inv~ntion. For ~x~mple, ~ ~pir~l ~etsl tcpe
can be placed in the epertures of the retsining member
then ~illed with ~olten ~older, ~uch a in wave soldering
oper~t~Dn? then oool~d. The s~pported ~solder column in the
reteining ~esn6 ~ill then function in for~ing interconne~tion~
from which the ret~ining ~eans can be rlemoved if desired~
The form~tion of supported solder columns in situ oould
~180 be done simultaneously ~ith as~embling the electrioally
conductive elements~ whereby the ~older ~upport such 8S ~
lo cpir~l metel t~pe, in the retaining me~ns is filled ~nd the
connections formed at the end~ of the supported ~oldEr
column sll in one soldering operstion. It h~s been found
th~t in ~ome case~ when ~ solder wire is wrapped with a
tape, it is useful to reflow the solder then cut the desired
length columns for u6e in this invention end thereby discard
~ny portions thereof th~t ~ay not have sufficient solder
therein.
The interconnectiDn preform placement device o~ the pre-
~ent invention provides ~ unique and conveni~nt technique
Zo for eccur~t.ely positioning e plurality o~ preforms between a
chip c~rrier and 8 circuit board to which the carrier is
mounted. The use of cylindric~l column preforms of solder
result~ in solder joint~ of low bending stif~ness.and hence
low ~he~r stres~es, which contribute to high fstigue resist-
~S ance in the joints._._lhe u~e of the column-~haped preform in
the present invention ensure~ th~t the desir~ble oolumn
~nfigurations will be ret~ined during the snldering process
and th~t the Formed solder joint~ will be of column ~hepe
h~v ing low shear ~tresses di~tributed therethrough.
In ~ddition to-the e~bodiment of ~i98. 9 ~nd 1~ de6-
crib~d ebove, the interconnectiOn preform pl~cement device




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MPOB64

-~3-

~y h~ve a layer of pres~ure-~ensitive edhesive on it~
0urfaces, with or ~ithout a "rele~se" paper or co~er. This
~dhesive ~ill MBintain the device on ~he c~rcuit boQrd and
the chip package on the device during hsndling prior to the
oldering ~r reflowing prnce~3. The adhesive i~ ~pplied in
~uch ~ w~y as not to interfere with the sold~ring or re~lowing
:: process.
The retaining member may be m~de of a suitable high-
temperature material capsble of sustaining the heat applied
; lo during the coldering or refl~wing proces~ snd be of ~n
electric~lly insulating materi~l to be left in pl~ce ~Fter
soldering to provide an electrical insulator and an ~nvironmental
~eal. AlternativEly, the retaining member may be made of
material which is he~t-soluble, chemically soluble, or
~ disintegr~ble such th~t after ~olderin~ the ret~ining member
: can be dissolved or disint~gr~ted end removed from the
ounting to provide clearance for flux removal, for instance,
or for other procedures to c~mplete the in~tall~tiDn.
It will bE appreciated that ~hile this invention has
~: 20 been illugtra~ed by embodiments of sl2nder cylindrical
column, the devices, erticle~, methods cnd composition o~
;~ this invention are equally useful to form connections between
electrically conductive element~ ~here the joint forming
matérial need not bé sn elongate column but can be a disk,
2S ~fer or other configuration where the ~idth is greater
th~n thc l~ngth ~r height, ~uch as in applic~tions where
~: ~omp&ct spacing or current speed i8 more import~nt th~n
therm~l cycling~ It will ~180 be appreci~ted that this
~: invention is useful with other conventional proce~ing
. ~ methods, for ex~mple, the interconnect points on the

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~lectrically conductive element~ or the el~ds of the p~cfDrms
can be coated, fDr exe~ple, by 8 g~reening process~ ~ith a
801der ~re~m to enh~nce the formatiDn or efficiency of the
connection.
The concepts ~mbodied in the present invention may be
sd~pted for use in attaching ~ ehip to ~ chip carrier or
a chip directly to a circuit bo~rd, or to ~ttach leaded
CCP~ or hybrid thick-film-t~pe chip carrie~s to circuit
bo~rd~. Multiple preform plscement devices or larger-scale
o placement devices c2n ~ccommodate the simultsneous boncling
of numerou~ chip carrier packages. Further, the interconnec-
tion preform pl~cement device m~y be placed between two
circuit board~ to interconnect verticAlly the conductive
p~d6 of bo~rds.
~ hile preferred embodiments of the invention heve been
illustr~ted ~nd described, it will be ~ppreciated thst
v~ristions there~rom may be made without dep~rting from the
scope of the invention es defined in the nppended clsims.

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Representative Drawing
A single figure which represents the drawing illustrating the invention.
Administrative Status

For a clearer understanding of the status of the application/patent presented on this page, the site Disclaimer , as well as the definitions for Patent , Administrative Status , Maintenance Fee  and Payment History  should be consulted.

Administrative Status

Title Date
Forecasted Issue Date 1990-05-29
(22) Filed 1984-06-29
(45) Issued 1990-05-29
Expired 2007-05-29

Abandonment History

There is no abandonment history.

Payment History

Fee Type Anniversary Year Due Date Amount Paid Paid Date
Application Fee $0.00 1987-06-16
Registration of a document - section 124 $0.00 1987-12-29
Maintenance Fee - Patent - Old Act 2 1992-05-29 $100.00 1992-04-21
Maintenance Fee - Patent - Old Act 3 1993-05-31 $100.00 1993-04-13
Maintenance Fee - Patent - Old Act 4 1994-05-30 $100.00 1994-04-18
Maintenance Fee - Patent - Old Act 5 1995-05-29 $150.00 1995-04-21
Maintenance Fee - Patent - Old Act 6 1996-05-29 $150.00 1996-04-17
Maintenance Fee - Patent - Old Act 7 1997-05-29 $150.00 1997-04-17
Maintenance Fee - Patent - Old Act 8 1998-05-29 $150.00 1998-04-17
Maintenance Fee - Patent - Old Act 9 1999-05-31 $150.00 1999-04-19
Registration of a document - section 124 $0.00 1999-06-23
Maintenance Fee - Patent - Old Act 10 2000-05-29 $200.00 2000-04-17
Maintenance Fee - Patent - Old Act 11 2001-05-29 $200.00 2001-04-20
Maintenance Fee - Patent - Old Act 12 2002-05-29 $200.00 2002-04-03
Maintenance Fee - Patent - Old Act 13 2003-05-29 $200.00 2003-04-02
Maintenance Fee - Patent - Old Act 14 2004-05-31 $250.00 2004-04-06
Maintenance Fee - Patent - Old Act 15 2005-05-30 $450.00 2005-05-04
Maintenance Fee - Patent - Old Act 16 2006-05-29 $450.00 2006-05-01
Owners on Record

Note: Records showing the ownership history in alphabetical order.

Current Owners on Record
RAYCHEM CORPORATION
Past Owners on Record
ALLEN, LESLIE JOHN
CHERIAN, GABE
DIAZ, STEPHEN H.
RAYCHEM CORPORATION
Past Owners that do not appear in the "Owners on Record" listing will appear in other documentation within the application.
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Document
Description 
Date
(yyyy-mm-dd) 
Number of pages   Size of Image (KB) 
Drawings 1993-10-07 6 195
Claims 1993-10-07 5 156
Abstract 1993-10-07 1 19
Cover Page 1993-10-07 1 28
Representative Drawing 2001-08-07 1 6
Description 1993-10-07 35 1,628
Fees 1996-04-17 1 69
Fees 1997-04-17 1 72
Fees 1995-04-21 1 69
Fees 1994-04-18 1 60
Fees 1993-04-13 1 63
Fees 1992-04-21 1 62