Note: Descriptions are shown in the official language in which they were submitted.
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BACKGROUND OF T~ INVENTION
The present invention relates in general to an im-
proved gang bonding interconnect tape for use in bonding ma-
chines for automatic gang bonding of semiconductive devices and
to a method of making same.
DESCRIPTION OF THE PRIOR ART
Heretofore, gang bonding interconnect tapes, having
a series of interconnect patterns formed thereon, have been
used in automatic gang bonding machines to bond the individual
semiconductive chips to the inner ends of the individual lead
patterns and for subsequent bonding of the outer regions of
~; the interconnect lead pattern to a lead frame structure.
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In one prior method of fabricating the gang bonding
interconnect tape, a 5 mil thick polyimide tape is coated on
one side with a half mil thick layer of adhesive. The coated
tape is then punched to provide two rows of outer sprocket holes
and then centrally punched to provide a row of personality
holes, i.e., the hole in the central region of the interconnect
lead pattern to receive the chip or die. The tape is also
punched with a ring of apertures in the region of the outer
lead bond in each lead pattern to facLlitate shearing of the
, interconnect lead pattern at the time of making of the outer
i lead bond to the lead frame structure. A 1.3 to 1.4 mil thick
copper sheet is hot laminated over the central region of the
adhesive coating to provide a laminated tape structure. The
copper is coated with a layer of photoresist, and exposed to
images through a mask corresponding to each of the individual
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nterconnect lead ~atterlls, such mask being indexed via the
punched sprocket holes. The exposed tape is then developed,
and etched to form the interconnect lead patterns in the
copper sheet.
The result tape is fed through a first automatic gang
bonding machine wherein the inner ends of the individual inter-
connect leads are thermal compression gang bonded to gang bond-
ing bumps on the semiconductive device. In this first bonding
step, the semiconductive device is transferred to the tape.
The tape is then fed through a second automatic bonding machine
wherein the individual lead patterns are sheared out of the
tape and thermal compression gang bonded at their outer ends
to the inner ends of a pattern of leads, such as a lead frame
structure, printed circuit board or flexible circuit.
A problem with this first method of fabricating an auto-
matic gang bonding interconnect tape is that the interconnect
lead paterns are indexed to the punched sprocket holes which
are not virgin holes for use in the bonding machine.
In a second method for fabricating an automatic gang
bonding interconnect tape, a half mil thick polyimide coating
is cast onto one side of a 1.3 to 1.4 mil thick 7" wide master
copper tape. Next, the master tape is coated with photoresist
on both sides. The master tape is then exposed simultaneously
on both sides with different patterns of optical radiation,
the copper side being exposed with patterns for parallel rows
of individual interconnect leads and parallel rows of sprocket -
holes, whereas the polyimide side is exposed with patterns
corresponding to parallel rows of personality holes, rows of
sprocket holes and rows of rings of perforations in the region
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of the shcar line at the outer lead bond srea of the indivitual
lead patterns. Next, the polyimide side is etched to provide
the personality holes, the sprocket holes and the outer lead
pattern perforations. Next, the copper side is etched to
provide the interconnect lead patterns, and the sprocket hole
patterns. The resultant master tape is then slit into a
plurality of resultant tapes and used in an automatic gang
bonding machine in the same manner.as previously described.
A problem with this latter method for fabrication
of an automatic gang bonding interconnect tape is that some
of the etched sprocket holes are used in the slitting step
so that some of the sprocket locator holes for the resultant
tapes are not virgin as used in the bonding machine. Also,
the patterns formed in the master tape are not indexed to
the tape and thus spacing errors in the patterns can accumulate
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- along the length of the resultant tapes.
Therefore, it is desired to provide an improved
"~ method for manufacture of an automatic gang bonding inter-
? connect tape which provides virgin sprocket holes for use in
` 20 the gang bonding machine and which has improved indexing of
the individual interconnect lead patterns and their respecti~e
sprocket holes.
SUMMARY OF THE PRESENT INVE~TION
The principal ob~ect of the present invention is
~' the provision of an improved method for fabrication of a gang
bonding interconnect tape.
The invention is used in a method for fabricatlon
of a gang bonding interconnect tape for interconnecting a
first pattern of leads and a second pattern of leads, such
, 30 interconnect tape having a series of metallic interconnect lead
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patterns thereon, lndlvidual one~ of the lead pattern~ lncluding
a plurallty of rlbbon-shaped metalllc leads ex~ending outwardly
from a central portion of the pattern to an outer region of
the pattern and including an electrically insulative support
structure interconnecting a plurality of the ribbon-shaped
metallic leads in a region of the pattern intermediate the
outer region thereof and the central region thereof. The
invention relates to the steps of: forming a row of fir~t
locator holes along the marginal ~ide edge of an elongated tape;
; 10 forming a row of the metallic interconnect lead patterns in
the tape; forming a second row of locator holes in the tape
for locating the interconnect patterns in the bondlng machine
in which the tape is to be employed for gang bonding to the
semiconductive devices; indexing the formation of respective
ones of the second row of locator holes to the formation of
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respective ones of the row of interconnect lead patterns; and
indexing the formation of both of the second row of locator
holes and the row of interconnect lead patterns to the row of
~ ~ first locator holes.
¦ 10 In another feature of the present invention, a
~ ~process of-photoetching i9 employed for the formation of the
t ~ ~ rows of interconnect lead patterns and rows of their respective
j locator holes. A mask, utiIized for exposing the photoresist
~; coating on the master tape, is indexed to the master tape via
-~ 8procket holes in the master tape. The mask serve~ to index
respective sets of locator holes to respective ones of the
interconnect lead patterns.
~` Other features and advantages of the present invention
will become apparent upon a perusal of the following specification
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taken in connectlon with the accompanying drawings wherein:
~RIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a plan view of a metallic,tape depicting
the parallel rows of electrically insulative support structures
deposited thereon,
Fig. 2 is an enlarged view of a portion of the
structure of Fig. 1 delineated by line 2-2,
Fig. 3 is a view similar to that of Fig. 1 depicting
the step of exposing the photoresist coated metallic tape to
the patterns of radiation corresponding to the individual
interconnect lead patterns and locator hole patterns,
Fig. 4 is an enlarged detail view of a portion of
the structure of Fig. 3 delineated by line 4-4,
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Eig. ~ is dn enlarged detail view of a portion of
the structure of Fig. 3 delineated by line 5-5,
Fig. 6 is a plan view of one of the individual auto-
matic gang bonding interconnect }ead tapes after having been
separated from the composite tape of Fig. 3,
Fig. 7 is an enlarged detail view of a portion of
the structure of Fig. 6 delineated by line 7-7,
Fig. 8 is an enlarged sectional view of a portion of
the interconnect lead structure of Fig. 7 as bonded to a die
and to an outer lead frame,
Fig. 9 is a sectional view of a semiconductor die
bonded to a first interconnect lead pattern which is in turn
bonded to a second surrounding interconnect lead pattern of Fig.
10, and
Fig. 10 is a schematic plan view of an alternative
interconnect tape embodiment of the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring now to Figs. 1 and 2, a 1000 foot roll of
wrought copper sheet having a wei~ht of one ounce per square
foot or a thickness of 1.3 to 1.4 mils is slit into a 70 mil-
limeter width to provide a copper tape 11. The copper tape 11
is preferably coated with copper phosphate or other materials, -~
using conventional techniques, to promote adhesion of organic
plastic materials to be subsequently applied to the copper tape.
The copper tape is punched along opposite side marginal edges
thereof with sprocket holes 12 to be utilized as locating holes.
The holes 12 are spaced at 1.5 inch intervals along the length
of tape 11. The copper tape is then annealed and cleaned.
A pattern of electrically insulative support struc-
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~res 13, such as rings, are then screened, as by screening,
onto one face of the copper tape 11. In the screening process,
the sprocket holes 11 are utilized as locating holes for in-
dexing the screening pattern so as to provide proper indexing
for the pattern of support structure 13. In a typical example
of the screening step of the process, the support structures 13
are screened through a 3" x 3" screen pattern. The support struc-
tures 13 are deposited to a thickness of ~etween 0.5 mlls and
2 mils. The electrically insulative screening material 13 should
10 be compatible with bonding temperatures of approximately 400C
for 0.1 second, have a pot life of four hours at 25C, be flex-
ible in thicknesses of O.S to 2.0 mils, and have the electrical
properties of a good dielectric. Suitable electrically insula-
tive support structure materials include thermal setting plastic
materials and thermoplastic materials. The thermal setting
plastic materials include, cycloalaphatic plastics with anhydride
cure, low molecular weight bisphenol with anhydride cure, both
cycloalaphatic and low molecular weight disphenol with phenolic *
cure, silicon material such as silanol and vinyl containina sil-
20 oxane cured with an SIH siloxane, polyimide, polyamide, mixtures
of polyimide andpolyamide, phenolics, and diallylphthalate with
peroxide cure. Suitable thermoplastic materials include poly-
sulphone, polycarbonate, and ABS. The use of these materials
should be compatible with the temperatures encountered in subse-
~uent bonding steps. Thus, for thermal compression bonding
where temperatures of 450C are encountered the aforecited epoxy
and polyimide materials are most suitable.
A suitable epoxy for use in the screening step of the
process includes anhydride cured cycloalaphatic epoxy resin
30 which is liquid at room temperature and which has a relatively
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¢, ,~ viscosity at ~5C, that is, a viscosity less than 500
centipose. The cpoxy resin includes a thixotroping agent to
carry the viscosity from 500 to over 120,000 centipose and to
provide a low yield value. A suitable thixotroping agent
includes 7 to 8% by weight of fumed sili~ca treated with silane
or silazane so as to convert the silanol groups to trimethyl
siloxy groups. This epoxy forms the subject matter of appli-
cant's U.S. Patent 4,043,969, issued August 23, 1977.
As an alternative to screening of the electrically
insulative support structures 13 onto the copper tape 11 they
may be applied by any one of a number of conventional methods
such as injection molding, electrostatic spraying through a mask, -
or by transfer from a sheet of the material to the copper sheet.
For screening, the thermal setting materials are suit-
able when they include a suitable thixotropic agent. For electro-
static spraying through a mask, either the thermal setting
materials or the thermoplastic materials may be utilized. For
injection molding, either the thermal setting or thermoplastic
materials may be utilized. For transfer moldin~, the thermal
setting materials are suitable.
A number of different formats may be employed depending
upon the size of the die which is to be bonded to the inter-
connect lead palterns to be formed on the tape. More particu-
larly, these support structures 13 are screened onto the tape 11
in a number of parallel rows 14 extending longitudinally of the
' tape 11. The number of parallel rows 14 depends upon the width
of the individual tapes which are to be subsequently formed by
slitting o~ the master tape 11.
One format corresponds to an individual tape width
of 11 millimeters to be utilized with a die size less than 60
x 60 mils,such pattern having a pitch P of 0.1667 inch, where the
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~tch is the longi.tudinal spacing between the center of adja-
cent support structures 13 of a given row, there being five
rows 14 of such support structures 13 in the 70 millimeter
width of the master tape 11. In such a case, a 3" length of the
composite tape 11 will accommodate 90 support rings 13.
A second format corresponds to an individual tape
width of 13.75 millimeters for accommodating die sizes less than
90 x 90 mils, such pattern having a pitch P of 0.214 inch and
providing four rows 14 in the 70 millimeter width of the master
tape 11 and 5Ç die locations per th,ree inch length of the master
tape 11.
A third format correspond to an individual tape
~idth of 16 millimeters to, accom,modate die'si~es less than 200 ~,
mils by 200 mils, such pattern having a pitch P of 0.300 inch,
there being three rows of such support structures 13 for a 70
millimeter wide master tape 11. This third format provides 30
die locations per three inch length of the master tape'll.
After the support structures 13 have been deposited on
the tape 11, the tape'is cured in an oven in an atmosphere.of
nitrogen gas so as to harden the individual support structures
13. At this point.the tape 11 may be inventoried if desired.
The method for fabricating a gang bonding interconnect tape em-
ploying the deposited support structure 13 forms the subject
matter of and is claimed in copending application Serial No.
251,273 filed April 28, 1976 and assigned to the same assignee
as the present invention.
Next, the master tape 11 having the support struc-
tures 1.3 deposited thereon is cleaned of the adhesion promoting
coating and any oxides thereon by appropriate etching and then
coated with an antioxidant coating such as chromate to promote
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photoresist adherence. The chromate antioxidant coating is
applied to the copper tape 11 by cleaning the copper tape with
hydrochloric acid and then immersing the copper tape in a plat-
ing solution of chromic acid mixed with sulfuric acid, such mix-
ture being 2.0% chromic acid to 8% full strength sulfuric acid
to 90~ deionized water by volume. The ~ape is immersed for one
minute at room temperature then removed, rinsed in deionized
water and dried. In this process, a chromate antioxidant coating
is deposited on the copper surface to a thickness of between 10
and 100 angstroms.
Next, the composite tape 11 is coated on both sides
with a positive type photoresist coating of conventional type
utilized in the semiconductor art. -
Next, the side of the tape ll which is opposite tothat containing the support structures 13 is exposed to patterns
15 of optical radiation to which the photoresist material is
sensitive. The patterns 15 of radiation are produced by a con-
ventional 4" x 4" photo mask as utilized in the semiconductor -
art (see Figs. 3-5). The mask 16 hasthereon an array of pat-
terns 15 corresponding to the individual interconnect lead
patterns to be formed in the copper tape 11. In a typical ex-
ample, the mask 16 exposes a three inch length of the tape 11.
In addition to the individual interconnect lead patterns 15,
the mask contains patterns 17 corresponding to sprocket holes
17' for each of the tapes which are to be subsequently split
from the master tape 11.
Due to a peculiarity of the automatic gang bonding
interconnect machines, the sprocket locator holes 17' for a
given interconnect pattern 15 must be axially displaced along
the tape from the particular lead pattern of interest by ap-
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proximatel~ 0.5" for the 11 mm, 0.642" for the 13.75 mm and 0.6"
for the 16 mm + ~ 0.0005". Thus, in the case of the 11 mm for-
mat the interconnect patterns 15 on the mask at the leading edge
thereof have their respective sprocket holes 17 trailing by 0.5"
as shown in Fig. 4. Similarly, at the trailing edge of the mask
16 the pattern for the sprocket holes 17 lags behind the respec-
tive interconnect pattern 15 by 0.5". Thus, the individual tape
sprocket holes 17 are indexed to the respective lead portions 15 i~-
via the mask 16 to a tolerance of + 0.0005".
10On the other hand, the mask 16 is indexed to the tape
11 by means of the sprocket holes 12 at the marginal edge of the
master tape 11. These sprocket holes 12 can provide indexing of
the mask 16 to the pattern of insulative support structures 13
to + 5 mils. At the overlap of one set of patterns 15 exposed
on the tape 11 through the mask 16 to a subsequent set of pat-
terns exposed through the mask 16 the overlap tolerance is + 5
mils as provided by the sprocket holes 12. However, the automatic
gang bonding machine has the capability of picking up or relé~sin~
the individual tape to compensate for the up to + 30 mil jump in
spacing of the sprocket holes 17 at the overlap of two patterns.
Suitable automatic gang bonding interconnect machines are the
ILB and OLB Model No. 1-1000 manufactured and marketed by Jade
Corporation of Philadelphia, Pennsylvania.
Next, the composite tape 11 is slit into the appropriate
number of individual tape strips 21, as shown in Figs. 6 and
7, such slitting occuring inbetween adjacent rows of sprocket
holes 17'. The indi~idual gang bonding interconnect tapes ~1
include a series of virgin sprocket holes 17' along opposite
marginal side edges thereof and a series of gang bonding inter-
connect lead patterns 15 formed therein.
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The individual patterns 15 are personalized to the
particular semiconductive die type to which they are to be
bonded and each includes an array of ribbon-shaped leads 22
extending outwardly from a central aperture 23 ~personality
hole) to an outer region 24 of the copper tape 21. The mar-
ginal edge of the personality hole 23 is defined by the inner
lip of the electrically insulative support structure 13 (ring)
and the ring 13 has sufficient radial extent ot provide suf-
ficient support for the individual leads 22 and to hold the
leads 22 in the desired circumferentially spaced position in
electrically insulative relation. The inner ends of the leads
22 overhang the inner periphery of the personality hole 23 for
bonding to gang bonding bumps on the semiconductive die.
An annular gap 25 is defined between the outer peri-
phery of the electrically insulative support structure 13 and
the inner lip of the frame portion 24. This gap 25 is provided
to facilitate shearing of the individual leads 22 at their
outer regions at the time that the interconnect lead pattern 15
is thermal compression bonded to the inner lip of the lead frame
structure, as more fully described below with regard to Fig. 8. -
After the individual tapes 21 have been separatedfrom the composite tape 11 they are inspected and spliced to-
gether into long lengths as of 1000 feet. The tape is then uti-
lized in the conventional manner with conventional automatic
gang bonding interconnect machines such as the aforementioned
Jade Model 1-1000. Briefly, in these automatic gang bonding
interconnect machines, as shown in Fig. 8, a semiconductive die
27, having a plurality, such as 14, gang bonding bumps 28 formed
thereon, is indexed with an individual personality hole 23 by
the gang bonding machine.
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The aang bonding bumps typically have a height of
between 1.0 and 2.0 mils and are connected at their bases to
patterns of interconnect metallization on the semiconductive
die 27. The inner ends of the leads 22 are thérmal compres-
sion bonded to the gang bonding bumps 28 by the gang bonding
tool, not shown, which presses the inner ends of the leads
22 down against the upper surface of the gang bonding bumps
2~. In a typical example the gang bonding tool is made of
carbon and heated to a temperature of, for example, 550C and
presses the inner ends of the interconnect leads down against
the gang bonding bumps with a pressure of approximately 8
grams per square mil for a time of approximately 0.2 seconds.
The gang bonding tool gang bonds 14 of such gang bonding bumps
to their respective interconnect leads 22 simultaneously.
The die 27 is held to a base support structure via
a release wax and due to the heating of the die by the thermal
compression tool, the wax releases the die and it is thereby
transferred to the tape 21. The tape 21 with the dies 27 at-
tached thereto is fed throughla second gang bonding machine
which thermal compression bonds the outer portions of the inter-
connect leads 22 to the inner ends of a set of lead frame mem-
bers 29. For bonding the inner ends of the lead frames 29 to
the outer ends of the interconnect leads 22,\the thermal com-
pression tool, now shown, is brought up against the lower side
of the interconnect leads 22lfor pressing the upper surface of
the interconnect leads into engagement with the lower surface
of the lead frame structure 29. In a typical example, the
temperature of the bonding tool for the outer lead bond is
approximately 450C and is held in engagement with the inter-
connect leads for approximately 0.15 seconds with a bondinq
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pressure of approximately 25 grams per square mil.
As the thermal compression bond is made between the
interconnect lead 22 and the inner ends of the lead frame 29,
the copper interconnect lead pattern 15 is sheared along a shear
line 31 located just inside the outer ~arginal edge of the
interconnect lead pattern 15. In this manner, the lead attached
die 27 is transferred from the tape 21 to the lead frame struc-
ture 29.
The advantages of the automatic gang bonding inter-
connect tape 21 and the method of fabricating same accordingto the present invention include, increased precision in the
indexing of the individual interconnect lead patterns and their
respective locator sprocket holes 17' in the resultant indivi-
dual tapes 21. In addition, the individual tapes 21 have virgin
sprocket or locator holes 17' for use in the inner lead gang
bonding machine.
- While the preferred embodiment of the present invention
utilizes the copper tape having the insulative structures formed
thereon, it is equally applicable to the other aforecited prior
art tape systems wherein in one system the copper tape portion
is laminated onto the polyimide carrier and in the other system
the polyimide is cast onto the copper tape.
In an alternative embodiment of the present invention,
see Figs. 9 and 10, a 70 mm wide copper tape 41, as of 2.6
mil thickness, is punched with sprocket holes 12 and treated
with an adhesion promoting agent, as before described. Patterns
of electrically insulative support structures 13', such as
rings, are screened or otherwise applied, onto one face of t~e
copper tape 41, as before described. The tape 11 is cured and
etched, as before described, to define certain interconnect lead
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patterns 42 which are to form 1ead patterns for rnaking gang
bonding connections to the outer ends of respective ones of
the interconnect leads 22, as previously bonded at their inner
ends to the dies 27. The interconnect lead patterns 42, thus,
take the place of the lead frame 29 of the previous example
and the dies 27 are transferred to the flexible lead patterns
42 upon making of the gang bond between the outer ends of the
inner interconnect lead patterns 22 and the inner ends of the
outer interconnect lead pattern 42. Thus the latter interconneot
lead pattern 42 is similar to a flexible printed circuit board
and may be punched from the tape 41 along outer shear lines 44
of the pattern for bonding or otherwise belng interconnected
to other electrical circuitEy at the outer margin thereof.
In this latter embodiment, additional insulative .
structures, such as a yrid pattern, are deposited at the time
of depositing the insulative rings for further strengthening
of the lead patterns located outside of the bonding area.
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