Note: Descriptions are shown in the official language in which they were submitted.
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HIGH DENSITY CONNECTOR AND
METHOD OF MANUFACTURE
Background of the Invention
1. Field of the Invention:
The present invention relates to electrical conndctors and more
particularly high I/O density connectors, such as array connectors.
2. Brief Description of Prior Developments:
The drive to reduce the size of electronic equipment, particularly
personal portable devices, and to add additional functions to such
equipment, has resulted in an ongoing drive for miniaturization of all
components, especially electrical connectors. Efforts to miniaturize
connectors have included reducing the pitch between terminals in
single or double row linear connectors, so that a relatively high
number of I/O or other lines can be interconnected by connectors that
fit within tightly circumscribed areas on the circuit substrates allotted
for receiving connectors. The drive for miniaturization has also been
accompanied by a shift in preference to surface mount techniques
(SMT) for mounting components on circuit boards. The confluence of
the increasing use of SMT and the required fine pitch of linear
connectors has resulted in approaching the limits of SMT for high
volume, low cost operations. Reducing the pitch of the terminals
increases the risk of bridging adjacent solder pads or terminals during
reflow of the solder paste. To satisfy the need for increased I/O
density, array connectors have been proposed. Such connectors have
a two dimensional array of terminals mounted on an insulative
substrate and can provide improved density. However, these
connectors present certain difficulties with respect to attachment to
the circuit substrates by SMT techniques because the surface mount
tails of most, if not all, of the terminals must be beneath the connector
body. As a result, the mounting techniques used must be highly
reliable because it is difficult to visually inspect the solder connections
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or repair them, if faulty. In the mounting of an integrated circuit (IC)
on a plastic or ceramic substrate the use of ball grid array (BGA) and
other similar packages has become common. In a BGA package,
spherical solder balls attached to the IC package are positioned on
electrical contact pads of a circuit substrate to which a layer of solder
paste has been applied, typically by use of a screen or mask. The unit
is then heated to a temperature at which the solder paste and at least
a portion or all of the solder ball melt and fuse to an underlying
conductive pad formed on the circuit substrate. The IC is thereby
connected to the substrate without need of external leads on the IC.
While the use of BGA and similar systems in connecting an IC
to a substrate has many advantages, a corresponding means for
mounting an electrical connector or similar component on a printed
wiring board (PWB) or other substrate has yet to be developed. It is
important for most situations that the substrate-engaging surfaces of
the solder balls are coplanar to form a substantially flat mounting
interface, so that in the final application the balls will reflow and
solder evenly to a planar printed circuit board substrate. Any
significant differences in solder coplanarity on a given substrate can
cause poor soldering performance when the connector is reflowed onto
a printed circuit board. To achieve high soldering reliability, users
specify very tight coplanarity requirements, usually on the order of
0.004 inches. Coplanarity of the solder balls is influenced by the size
of the solder ball and its positioning on the connector. The final size
of the ball is dependent on the total volume of solder initially available
in both the solder paste and the solder balls. In applying solder balls
to a connector contact, this consideration presents particular
challenges because variations in the volume of the connector contact
received within the solder mass affect the potential variability of the
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size of the solder mass and therefore the coplanarity of the solder balls
on the connector along the mounting interface.
Another problem presented in soldering connectors to a
substrate is that connectors often have insulative housings which
have relatively complex shapes, for example, ones having numerous
cavities. Residual stresses in such thermoplastic housings can result
from the molding process, from the build up of stress as a result of
contact insertion or a combination of both. These housings may
become warped or twisted either initially or upon heating to
temperatures necessary in SMT processes, such as temperatures
necessary to reflow the solder balls.
Such warping or twisting of the housing can cause a
dimensional mismatch between the connector assembly and the PWB,
resulting in unreliable soldering because the surface mounting
elements, such as solder balls, are not sufficiently in contact with the
solder paste or close to the PWB prior to soldering.
A need, therefore, exists for reliably and efficiently mounting
high density electrical connectors on substrates by surface mounting
techniques.
Summary of the Invention
Electrical connectors according to the present invention provide
high I/O density and reliable attachment to circuit substrates by SMT
techniques. These connectors exhibit high coplanarity along the
mounting interface.
Electrical connectors of the present invention are ones in which
one or more terminals are connectable by a fusible electrically
conductive material to a substrate. This fusible electrically conductive
material is a solder mass, preferably comprising a solder ball that can
be reflowed to provide the primary electrical current path between the
terminal and a circuit substrate.
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An aspect of the invention includes methods for forming an
exterior fusible conductive contact on an element of an electrical
connector. According to one method, a recess is formed on the
exterior side of the connector elements or contacts. A section of a
conductive contact extends from adjacent the interior side of the
conductor element into the recess on the exterior side of the housing.
The recess is filled with a controlled volume of solder paste. A fusible
conductive element, for example a solder ball, is positioned in the
recess on the exterior side of the housing. The conductive element
placed in the recess is then heated to a temperature sufficient to fuse
the solder paste and fuse the fusible conductive element to the section
of the contact extending into said recess.
Also encompassed by this invention is a contact for use in an
electrical connector which comprises a terminal tab area where said
contact is connectable to a fusible conductive element, such as a
solder ball. A medial area of the contact is positioned between the
terminal tab and a contact area. The medial area is adapted to resist
molten solder flow, for example, by application of a coating or plating
of a non-solder wettable material. By this arrangement wicking of the
solder from the solder ball from the area of attachment to the contact
avoided.
Coplanarity of the surface mounting interface of the connector
is maintained by providing an insulative connector housing in which
stress buildup is avoided. According to this aspect of the invention, a
contact terminal is inserted into an opening in the housing. The cross
section of the opening is configured so that at least one side thereof
has or comprises a shaped projection adapted to be deformed by the
terminals as the terminal is inserted into the opening. By means of
this arrangement, stress build up as a result of multiple contact
CA 02497606 2007-05-04
insertions is avoided, so as to minimize warping and twisting of the
housing.
Accordingly, the present invention provides an electrical connector
comprising:
5 a dielectric base, the dielectric base defining a mounting surface, a
mating surface, and a passageway that extends from the mounting surface
to the mating surface;
an electrical contact positioned inside the passageway defined by the
dielectric base, the electrical contact comprising a tab with a free end; and
a fusible element fused onto the tab adjacent to the free end of the
tab, wherein the fusible element extends at least partially into the
passageway.
Brief Description of the Drawings
The method and connector of the present invention is further
described with reference to the accompanying drawings in which:
Fig. 1 is a top plan view of a receptacle connector of a preferred
embodiment of the connector of the present invention;
Fig. 2 is a partially cut away end view of the receptacle shown in Fig.
1;
Fig. 3 is a top plan view of a plug element of a preferred embodiment
of the present invention;
Fig. 4 is a partially cut away end view of the plug element shown in
Fig. 3;
Fig. 5 is a cut away end view of the receptacle and plug shown in
Figs. 1 - 4 in unmated relation;
Fig. 6 is an end view of the receptacle and plug shown in Fig. 5 in
mated relation;
Figs. 7a, 7b and 7c are cut away end views showing respectively
first, second and third sequential stages in the mating of the receptacle
end plug shown in Fig. 5;
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Fig. 8 is a bottom plan view of the receptacle shown in Fig. 1
before the placement of solder balls thereon;
Fig. 9 is a bottom plan view of the receptacle shown in Fig. 8
after placement of the solder balls thereon;
Fig. 10 is a detailed cut away view of area XII in Fig. 1;
Fig. 11 is an enlarged view of the cut away area in Fig. 4;
Fig. 12 is an enlarged view of the cut away area in Fig. 10;
Fig. 13 is an enlarged cross sectional view through 13 - 13 in
Fig. 10;
Fig. 14 is a top plan view of a second preferred embodiment of a
receptacle connector of the present invention;
Fig. 15 is an end view of the receptacle shown in Fig. 14;
Fig. 16 is a top plan view of a second preferred embodiment of a
plug connector of the present invention;
Fig. 17 is an end view of the plug shown in Fig. 16;
Fig. 18 is an end view of the mated receptacle and plug shown
in Figs. 14 - 17;
Fig. 19 is a top plan view of a receptacle used in a third
preferred embodiment of a receptacle connector of the present
invention;
Fig. 20 is an end view of the receptacle shown in Fig. 14;
Fig. 21 is a top plan view of the plug element of the third
preferred embodiment of a plug connector of the present invention;
Fig. 22 is an end view of the plug element shown in Fig. 2;
Fig. 23 is an end view of the mated receptacle and plug shown
in Figs. 19 - 22;
Fig. 24 is a side cross sectional view in fragment of another
embodiment of a connector according to the present invention;
Fig. 24a is a fragmentary view of a portion of the structure of
Fig. 24 modified to form a deeper recess;
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Fig. 25 is a front cross sectional view in fragment of the
connector shown in Fig. 24 in which the plug and receptacle are
unmated;
Figs. 26a and 26b is a graph showing temperature versus time
and distance during solder reflow in Examples 1 and 2 of the method
of the present invention;
Figs. 27a - 27f are laser generated profiles of the product of
Example 3 of the method of the present invention;
Figs. 28a and 28b are x-ray photographs showing the product of
Example 4 of the method of the present invention;
Figs. 28c and 28d are electron microscope photographs showing
the product of Example 4 of the method of the present invention.
Fig. 29 is a view similar to Fig. 10 in which the ground and
power contacts have been omitted;
Fig. 30 is a cross sectional. view through XXXI - XXXI in Fig. 13;
Fig. 31 is a computer generated representation of predicted
stresses in an insulative housing similar to those illustrated in the
preferred embodiments of the present invention;
Fig. 32 is a graph of contact retention force as a function of the
amount of deformation (compression) in a rib of the insulative housing
as is shown in Fig. 29;
Fig. 33 is a front elevational view of a receptacle signal contact
used in a preferred embodiment of the connector of the present
invention;
Fig. 34 is a front elevational view of a plug signal contact used
in a preferred embodiment of the connector of the present invention;
Fig. 35 is a front elevational view of a receptacle ground/power
contact with carrier strip used in a preferred embodiment of the
connector of the present invention; and
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Fig. 36 is a front elevational view of a plug ground/power
contact with carrier strip used in a preferred embodiment of the
connector of the present invention.
Detailed Description of the Preferred Embodiments
Referring generally to Figs. 1 - 2 and 12 - 13, a set of
intermating connectors according to a first embodiment of a high
density connector of the present invention includes a receptacle which
is shown generally at numeral 10. A base section of the receptacle is
shown generally at numeral 12. The base is preferably formed by
molding an appropriate insulating polymeric material capable of
withstanding SMT reflow temperatures, for example, liquid crystal
polymer (LCP). Referring first to the base section, this element
includes a base wall 14 having an exterior side 16 and an interior side
18. On the exterior side there are outer recesses as, for example,
recesses 20, 22, 24, 26 and 28 (Fig. 12). On the interior side there are
inner contact receiving recesses as, for example, recesses 30, 32, 34,
36 and 38. Connecting these inner and outer recesses are medial
slots as, for example, slots 40, 42, 44, 46 and 48. Each of the outer
recesses has a base wall and a lateral wall as, for example, base wall
50 and lateral wall 52 (Fig. 12). Each of the inner signal contact
receiving recesses has a base wall and intersecting lateral walls as, for
example, base wall 54 and lateral walls 56 and 58. Each of the inner
ground or power contact receiving recesses also has a base wall and
diagonal lateral walls as, for example, base wall 60 and lateral walls
62 and 64. The above described inner and outer recesses and
connecting medial slots receive ground/power contacts or signal
contacts.
The ground or power contacts preferably have an upper section,
shown generally at numeral 66, formed of two contacting forks 68 and
70. Each of these forks has a converging section 72, a contact point
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74 and an outwardly diverging or lead-in section 76. The ground or
power contacts also include a medial section 78 passing through the
lower wall of the receptacle and a lower section 80 that extends into
the outer recess. A solder ball 82 is fused onto lower section 80, as
will be described below.
Each of the signal contacts (Figs. 12 and 13) includes an upper
section shown generally at numeral 84 preferably having a contact
projection 86, a lead-in bend 88 and a stiffening rib 90. The signal
contacts also include a medial section 92 which passes through the
lower wall of the receptacle. Each signal contact includes a lower
section 98 (Fig. 13) extending into the outer recess for example, recess
22 in Figs. 12 -13, where a solder ball 100 is fused to lower section 98
as will be explained below.
Referring particularly to Figs. 1 - 2, the base section of the
receptacle includes latching structures, for example, as is shown
generally at numeral 102. This latching structure includes an upward
tab 104 which is superimposed over a vertical groove 106 and which
has an outward projection 108. The base section of the receptacle
also has other similar latching structures 110, 112 and 114. The
receptacle also includes an upper section shown generally at 116
which is superimposed over the base section. This upper section has
a top wall 118 and a peripheral side wall 120. This upper section is
fixed to the base section by means of latching structures as is, for
example, shown generally at numeral 122. Each of these latching
structures has a side wall recess 124 and a U-shaped latch 126 which
extends downwardly from the top wall and is spaced from the side
wall recess. The tab 104 fits between the U-shaped latch 126 and the
side wall recess 124 to enable the U-shaped latch to engage the
outward projection 108 on the latching structure 102 of the base
section. The upper section includes other similar latching structures
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128, 130 and 132 which engage, respectively, latching structures 110,
112 and 114 on the base section. The upper section 116 or the base
102 also may have mounting brackets 134 and 136 which have
fastener apertures 138 and 140, respectively. On the top wall 118 of
5 the upper section 116 there are also signal contact access apertures
as, for example, apertures 142 and 144. These access apertures are
arranged in a plurality of rows corresponding to the rows of signal
contacts in the base section. Interposed between these rows of signal
contact access apertures are elongated ground or power contact
10 access slots as, for example, slots 146 and 148. The upper section
116 forms a mating interface between receptacle 10 and a mating plug
150 described below.
Referring to Figs. 3 - 4 and Fig. 11, the plug element of the
connector is shown generally at numeral 150. The plug includes a
base wall 152 and a peripheral side wall 154. There are opposed gaps
156 and 158 in the side wall and there is an open side 160 in opposed
relation to the base wall. Projecting laterally from the plug are
mounting brackets 162 and 164 having fastener receiving apertures
166 and 168 respectively, that are alignable with the fastener
receiving apertures 138, 140 in the mounting brackets of the
receptacle.
Referring to Fig. 11, on the inner side of the base wall 152 there
are inner signal contact receiving recesses such as recess 170. Also
on the inner side of the base wall are inner power or ground contact
receiving recesses such as recess 172. In opposed relation to the
outer recesses on the base wall there are outer signal contact receiving
recesses such as recess 174, and outer power or ground contact
receiving recesses, as at recess 176. Connecting the outer and inner
signal contact receiving recesses and the outer and inner power or
ground contact receiving recesses are, respectively, medial slots 178
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and 180. Mounted in the power/ground contact receiving recesses via
the medial slots 180 are power or ground contacts, shown generally at
numeral 182. Each contact 182 has an elongated inner section 184,
an elongated medial section 186, which is mounted in base wall 152,
and an outer section 188 extending into recess 176. A solder ball 190
is fused onto section 188. The outer section 188 and the solder ball
are partially contained in the outer recess 176. The plug also includes
a plurality of signal contacts 192. These signal contacts each have an
inner section 194, a medial section 196 mounted in the base wall, and
a terminal tab 198 extending into recess 174. A solder ball 200 is
fused onto terminal tab 198. Again it will be observed that this outer
section and the solder ball are partially contained in the outer recess
as at 170.
Referring to Figs. 5 - 7c, it will be seen that the plug described
above is mounted on a circuit substrate, such as a rigid PWB 202,
and the receptacle is mounted on a similar PWB 204. The plug and
receptacle thereby form a board to board interconnection, as
illustrated in Fig. 6. The plug has a two dimensional array of signal
contacts, such as 192 onto which are fused solder balls 200 and a
plurality of ground/power contacts, such as contacts 192, onto which
are fused solder balls 190. By use of SMT techniques, the solder balls
are also fused to the PWB 202 to fix the entire plug to the PWB and
effect electrical contact between the signal contacts and ground or
power contacts in the plug and the PWB. It will be appreciated that
although not all contacts are illustrated in Fig. 5, all such contacts are
connected to solder balls and to the PWB in the same way. Similarly,
solder balls 100 are fused onto receptacle signal contacts 84 and
those solder balls are fused to the PWB 204. Receptacle
ground/power contacts 66 are mounted in slot 134 and are fused to
solder balls 82 and these solder balls are fused to PWB 204.
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The plug is aligned with the receptacle so that the peripheral
side wall 154 of the plug overlaps the peripheral side wall 120 of the
upper section 118 of the receptacle.
Referring particularly to Figs. 7a - 7c the engagement of the
plug and receptacle is shown in greater detail. Fig. 7a shows, after
initial alignment, the ground/power contacts in the plug initially
entering the ground/power contact receiving slots in the receptacle
and engaging the corresponding power/ground contacts in the
receptacle. The signal contacts have entered the signal contact slots
in the receptacle. Fig. 7b shows the signal contacts in the plug
initially engaging the corresponding signal contacts in the receptacle
and the power/ground contacts in the plug becoming further engaged
between the opposed leaves of the power ground contacts in the
receptacle. Fig. 7c shows that the signal contacts in the plug being
fully engaged with the signal contacts in the receptacle. The
power/ground contacts in the plug have become positioned at the
base of the fork of the power/ground contacts in the receptacle.
Referring to Fig. 8, the exterior side 16 of the base section 12 of
the receptacle is shown prior to the application of the solder balls.
Prior to the application of the solder balls, the terminal tabs of the
signal contacts, for example, terminal tab 82, and of the power ground
contacts, for example terminal tab 98, are disposed within a
corresponding outer recesses for example, outer recesses 20, 22, 24,
26 and 28, by insertion of the contacts into the opposite surface 18 of
the base 12. A quantity of solder paste of appropriate composition is
applied to substantially fill each outer recess. The solder balls are
then applied over the outer or mounting surface of the base.
Preferably, the outer recesses are smaller in transverse extent than
the solder balls, so that the solder balls are supported on the edges of
the recesses, at a position near the terminal tabs of the contacts. To
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maximize the stability of the solder ball in the recess, a recess that is
round or the shape of a regular polygon in cross-section is preferred.
The solder paste aids in holding a solder ball in each of the exposed
recesses as is shown in Fig. 9, where, for example, solder ball 82 is
shown in recess 20 and solder ball 100 is shown in recess 22.
Additional solder balls, 230, 232 and 234 are shown, for example, in
recesses 24, 26 and 28. A solder ball will be positioned in all of the
outer recesses of the receptacle. It will also be understood that the
exterior side of plug will be substantially identical to the exterior side
of the receptacle before placement of the solder balls as is shown in
Fig. 8 and after emplacement of the solder balls as is shown in Fig.
11. After emplacement of the solder balls in the outer recesses, the
connector is subjected to a reflow process to fuse the solder balls onto
the terminal tabs. The exterior sides of the connectors, together with
the solder balls and particularly the outer surfaces of the solder balls,
form a substantially planar mounting interface, along which the
connector is mounted onto a supporting circuit substrate, such as a
PWB.
Figures 10 and 13 show a variant of the Figure 1 embodiment
wherein, instead of the forked receptacle contacts 66, oppositely
disposed pairs 66a and 66b of blade type contacts engage the
ground/power terminals 182.
Figs. 14 - 18 illustrate a second preferred embodiment of a set
of intermating connectors of this invention. Referring particularly to
Figs. 14 - 15, this set includes a receptacle shown generally at
numeral 236. This receptacle includes an insulative housing shown
generally at 238 which has an inner side 240, a lateral side 242 and
an exterior side 244. The housing also includes opposed alignment
projections 246 and 248. On the inner side of the housing there are
contacts 250 and 252 each having sections which bow away from
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each other and then converge to a contact point from which then
again diverge. Contacts 251 are mounted on base 231 in the same
manner as the embodiments shown in Figs. 1- 13. Solder balls, such
as solder ball 254, are mounted to the board side of contacts 250 and
252 in the same manner as described above. Referring particularly to
Figs. 16 and 17, the set also includes a plug shown generally at 258
which includes an insulative housing shown generally at 260 having
an inner side 262, a peripheral lateral side 264 and an exterior side
266. At one end of the housing there are a pair of vertical end walls
268 and 270 with a medial end recess 272. At the opposed end of the
housing there are another pair of end walls 274 and 276 with a medial
end recess 278. Extending from the inner side of the housing there
are a plurality of contacts as at contact 280 that extend from recesses
as at 282. Onto each of these contacts is fused a solder ball 284. It
will also be seen that these contacts are positioned in a staggered
arrangement. For example, contact 286 is offset with respect to
contact 280, so rows of contacts can be spaced closer together to
increase contact density. Referring particularly to Fig. 18, it will be
seen that each contact in the plug such as contact 280 is vertically
aligned with one of the pairs of converging contacts, such as contacts
250 and 252, in the receptacle and is interposed between these
converging contacts. It will also be seen that the alignment
projections 246 and 248 also engage the end recesses 272 and 278 in
the plug. In this embodiment the separate ground/power contacts
used in the Figs. 1 - 13 embodiment are not present. Such functions
can, if desired, be incorporated into the undivided contacts pairs.
Figs. 19 - 23 show a third preferred embodiment of a set of
intermating connectors. The plug is shown generally at numeral 290.
This plug includes a housing generally 292 having a base wall 294
and a peripheral lateral wall 296, as well as opposed alignment
CA 02497606 1997-10-10
projections 298 and 300. The base wall of the housing has an inner
side 302 and an outer side 304. Signal contacts, such as contact 306,
extend from inner side 302. It will be seen that the signal contacts are
also staggered or offset in alternate rows, to increase contact density.
5 The plug also includes ground or power contacts 310, 312, 314 and
316 arranged adjacent each of the sides of the plug parallel to one side
of the lateral wall. On the exterior side of the base wall are signal
contact solder balls, such as solder ball 318, and power ground
contact solder balls, such as 320, which are fused to their respective
10 contacts in the same way as described with respect to the first
embodiment. The receptacle is shown generally at numeral 322 and
has an insulative housing 324 that includes a base wall 326, a
peripheral lateral wall 328 and alignment projection receiving recesses
330 and 332. The base wall also has an exterior side 334 and an
15 inner side 336. Projecting from the inner side are signal contacts
such as contacts 338 and 340. The contacts in adjacent transverse
rows are also axially offset to allow an increase in contact density.
Parallel to each side of the peripheral wall there are lateral power or
ground contacts 342, 344, 346 and 350. On the exterior side of the
base wall there are for each signal contact a solder ball, such as solder
ball 352. There are also solder balls, such as at solder ball 354, for
attaching each of the power or ground pins. Referring to particularly
to Fig. 23, it will be seen that at the plug 290 engages receptacle 322.
As previously mentioned, components such as electrical
connectors, that are to be mounted on circuit substrates by SMT
techniques must meet very demanding specifications for coplanarity.
If tight tolerances on coplanarity, usually on the order of about 0.003
to about 0.004 inch, are not maintained, manufacturers experience
undesirably high failure rates resulting from faulty solder connections.
Variations in the distance of a surface mount portion of a contact from
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the circuit substrate can result from variations in the location of the
contact in the insulative housing occurring as a result of the contact
insertion process and from deformation of the housings, resulting in
bowing or warping of the mounting interface of the connector body.
Connectors made in accordance with the present invention are
capable of attaining strict coplanarity requirements by use of features
that carefully locate and size the fusible bodies used for bonding the
connector to a substrate and by the use of contact securing
arrangements that prevent accumulations of stresses in the connector
housing that tend to distort the housing.
In the embodiments of Figures 1 - 23 the metal contacts are
secured in insulative housings in a manner to avoid the inducing of
stress in the body of the housing. This securing is achieved by the
use of a shaped slot or opening into which a securing portion of the
contact is inserted. In one arrangement especially useful for the
smaller signal contacts, the slot has a shape that closely conforms in
shape and dimensions to all the surfaces of the contact but one. The
wall of the slot facing that one surface has an integrally molded lateral
projection projecting into the slot. The distance between the distal
end of the projection and the opposing wall of the slot is less than the
thickness of the contact. Thus the distal portion of the projection is
engaged by and deformed by the contact as it is inserted into the slot.
The contact is held securely in the slot by the normal force exerted on
the contact by the deformable projection. Because the distal of the
projection is free to deform, the build up of stresses in the housing is
avoided. In the preferred embodiments illustrated, the projection
comprises a pyramidal rib integrally formed on one of the side walls of
the slot.
The specific rib configuration illustrated is believed to be
optimum for the particular housings in which it is employed, but
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other similar ribs of somewhat different shape or size might be
advantageously employed with other types of housings. Referring
particularly to Figs. 29 and 30, a signal contact 494 is retained in slot
496 and abuts against rib 498. The rib has a planar surface 500,
where it engages the contact 494, and opposed oblique sides 502 and
504. The contact 494 is securely retained in the slot by engagement
with the back and side edges of the slot 496 and rib 498. The portion
of the rib adjacent surface 500 is free to deform as contact 494 is
forced into slot 496, thereby relieving any stresses that result from
contact insertion.
Similarly, a power/ground contact is retained in slot 508 and
bears against deformable rib 510. The rib has a distal portion 512,
where it abuts against the contact, and opposed oblique sides 514 and
516. In this arrangement, there is also an opposed rib as, for
example, rib 518. This opposed insulative rib also has a distal portion
520 and oblique sides 522 and 524. The opposed deformable ribs can
be used for securing larger contacts and for centering the contact in
the slot. Those skilled in the art will also appreciate the particular
shape, size, number and placement of such ribs may vary for different
types of housings, and these factors would be selected so that, to the
greatest extent possible, stresses in the housing are isolated in the
deformable ribs. Fig. 31 which was generated using ANSYS stress
analysis software available from Ansys, Inc. of Houston, Pennsylvania
shows that by use of the contact securing arrangement illustrated in
Figs. 29 and 30, high levels of stress are essentially isolated in the
ribs, and do not extend substantially beyond the contact mounting
slots thereby significantly reducing the risk of warpage or twisting of
the housing which could otherwise result from a large number of
contact insertions. The units for the various stress areas shown in
Fig. 31 is N/mm2 and the mm is the unit for displacement shown.
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Fig. 32 shows that, for a typical contact 494, increases in deformation
(compression) of the distal portion of the deformable rib up to about
0.0004 inch resulted in an increasing retention force between the
contact and the housing, resulting from the normal force imparted on
the contact by the rib. After 0.0004 inches of deformation
(compression), only minor increases in retention force resulted.
As previously mentioned, another factor influencing coplanarity
of the substrate mounting face of a connector utilizing BGA mounting
is the uniformity of the size of the solder balls and the position of the
solder balls with respect to the board mounting face of the connector
housing. In the preferred embodiments previously described, the
termination tab of each contact is positioned in a recess. The outer
recesses are substantially uniform in size and shape. These recesses
provide several features of importance with respect to the present
invention. The recesses can receive a highly uniform amount of solder
paste placed therein, for example, by a simple deposit and squeegee
operation. Thus the amount of solder available for securing each
solder ball onto a contact is substantially uniform. The recesses
locate the position of each solder ball in the lateral X - Y directions
prior to attachment of the solder balls onto the contacts. The recesses
also locate the solder balls in the Z direction with respect to the
bottom surface of the housing and the distance of the solder ball from
the terminal tabs of the contacts. The nominal extension of the tab
into the recess is set so that at the maximum of the tolerance for
extension of the tab into the recess, the tab does not touch the solder
ball and thereby influence its Z direction location. However, fusing of
the solder ball onto the contact tab is assured by having a relatively
uniform and adequate amount of solder, from the solder paste, in the
recess. Any variation in the distance between the contact tab and the
CA 02497606 1997-10-10
19
solder ball is absorbed by the variable volume of solder paste placed in
the recess.
In order to maintain an adequate amount of solder adjacent the
solder ball during the reflow step used to attach the solder balls onto
the contacts and to prevent solder wicking onto the engagement
surfaces of the contact, the contact is treated to resist solder wicking.
Referring particularly to Fig. 33, contacts 526 and 528 are shown
attached to a carrier strip 530. The contacts have a contact
engagement area 532 usually plated with non-oxidizing metals such
as gold, palladium or alloys of palladium. The contacts also have a
central area 534, a portion of which forms the contact retention area
in the housing. An anti-solder wicking or non-solder wettable
material is applied to the central area 532. One preferred material for
this purpose is nickel plating. While not intending to be bound by any
particular theory, it is believed that the solder resistant feature of this
nickel plated area results from or is enhanced by the oxidation of the
nickel after plating, for example, by exposure to ambient air for several
days. Surprisingly and unexpectedly, it is found that the nickel or
nickel oxide barrier prevents or reduces solder wicking in such
contacts. For the nickel or nickel oxide plating to have such a
passivation function, it is preferred that the plating have a thickness
of from l0 in to 100 in and more preferably about 50mm. Other
solder wick resistant materials are believed to be usable for this
purpose, such as flourine containing solder resist coatings. These
may be especially useful if the entire contact is plated with a
continuous outer layer of a solder wettable metal, for example, gold.
The contact tab area 536 may preferably be plated with a solder
receptive material such as gold, tin or tin alloys. Preferably the entire
contact will be plated with nickel. On the upper section there is a
precious metal layer selectively plated over the nickel. This upper
CA 02497606 1997-10-10
section precious metal plating will preferable have a thickness of from
l0 in to 100 in and more preferable 30 in. On the lower section
there is a solder wettable metal layer selectively plated on the lower
section. Alternatively, an electroplated layer of chromium can be
5 substituted for the nickel layer. Referring to Fig. 34, plug signal
contacts 538 and 540 are shown attached to a carrier strip 542. Each
of these contacts has a gold plated tab area 544, a nickel plated
central retention and anti-wicking area 536 and a precious metal
plated engagement area 548. Similarly in Fig. 35, the ground/power
10 contact 550 is shown attached to carrier strip 552. This contact has a
lower gold plated tab area 554, a nickel plated central anti-wicking
area 556 and an upper gold plated contact engagement area 558.
Another feature of ground/power contact 550 which is also found to
reduce wicking is a series of notches in the tab area 554 such as
15 notches 560, 562 and 564. Another feature of ground/power contact
550 which was included in embodiments disclosed above is vertical
slots such as slot 566. Referring to Fig. 36, a plug ground/power
contact 568 is shown which has a lower gold plated tab area 570, a
nickel plated central anti-wicking area 572 and an upper gold plated
20 area 574. It will be seen that ground/power contact 568 does not
have a separate carrier strip, but it does have apertures such as
aperture 576 which allow the contact itself to serve this carrier
function. With each of the contacts described above it will be
understood that tin or other solder wettable material may be
substituted for gold in the lower area. For all the contacts shown in
Figs. 33 - 36 the width of the lower gold plated tab area as is, for
example, shown at wi in Fig. 36 will preferably be from about 0.1mm
to about 0.25mm. The width of the nickel plated central area as is
shown, for example, at w2 in Fig. 36 will preferably be from about
0.1mm to about 1mm.
CA 02497606 1997-10-10
21
Referring to Figs. 24 - 25, an embodiment of the invention
having another arrangement for affixing solder balls is shown. The
receptacle of this connector is shown generally at numeral 324. This
receptacle has a base wall 326 having an exterior side 328 and an
interior side 330. On the exterior side there are recesses such as at
recesses 332, 334, 336, 338, and 340, (Fig. 25) 342 and 344 (Fig. 24).
Each of these recesses preferably has an oblique base wall 360 having
a rounded surface 362. On the interior side 330 there are recesses as
at recess 346, 348, 350, 352, 354 (Fig. 25), 356 and 358 (Fig. 24).
Between the exterior and interior recesses there are medial slots as at
slot 364, 366, 368, 370, 372 (Fig. 25), 374 and 376 (Fig. 24). Each of
these slots has a retention projection (not shown) for retaining the
contact in the slot, in a manner substantially the same as that
previously discussed in connection with Figs. 29 and 30. On the
interior side, the receptacle has substantially the same construction
as the receptacle illustrated in Figs. 1 and 2. It includes an upper
section 436 secured on base 326 in a suitable manner, preferably by
latches (not shown) as discussed with respect to Figs. 1 and 2. The
upper section or cover 436 has a plurality of openings, such as
openings 452 and 460, for receiving individual contacts from a mating
plug or slots, such as slots 454, 456, 468 (Figs. 25) for receiving
ground or power contacts from the mating plug. The signal contacts,
such as contact 408, and ground f power contacts are of a form
substantially as described with respect to any of the previous
described embodiments. For example, the ground contact 382 (Fig.
25) has a lower section 384 from which there is a tab 386. This
contact also has an upper section shown generally at numeral 388
which is made up of forks 390 and 392. Each of these forks has a
converging section 394 and an outwardly diverging lead-in section
396. The tab 386 is located in recess 336. Each signal contact, such
CA 02497606 1997-10-10
22
as contact 408, has an upper section 410 with a forward projection
412 and rearward bend 414. The signal contact also has a medial
section 416 where it engages the insulative housing and a lower tab
418 located in recess 334.
The tab 386 of ground contact 382 and the tab 418 of signal
contact 408 are formed by bending the tail portions of the respective
terminals about the surfaces 362, after the contacts are inserted into
base 326. Each surface 362 serves as bending mandrel for an
associated contact tail. The tails are bent to the extent of the oblique
surface 360 and are allowed to spring back so that the tabs are
transverse to the longitudinal axis of the contact and are substantially
parallel to the surface 328. This assures a high degree of coplanarity
of the tabs. Subsequent to formation of the tabs, solder paste is
applied to the outside surface of each tab. Solder balls, such as 398,
400, 402, 404, 406 (Fig. 25), 426 and 428 (Fig. 24) are then applied to
the tabs and the assembly is heated to fuse the solder paste and
solder ball onto each tab. In an alternative structure, shown in Fig.
24a, the recess 334a are deepened so that surfaces 360a and 362a are
positioned further from bottom surface 328a. As a result, the solder
ball 398a is located partially within the recess 334a and is stabilized
by the edges thereof, as previously discussed especially with respect to
Figs. 12 and 13. As a result, when solder balls of highly uniform size
are used, these arrangements can yield finished connectors that
exhibit coplanarity of the contacts across the mounting interface.
A plug having generally the same construction as the plugs
previously described is shown generally at numeral 430. It includes a
base wall 432 having an exterior side 434 and an interior side 436.
On the exterior side there are recesses as at recess 438, 440, 442, 444
and 446. Each of these recesses has an oblique base wall 448 and a
curved wall 450. Connecting with each of these recesses are contact
CA 02497606 1997-10-10
23
slots 452, 454, 456, 458 and 460. The plug also has a number of
power/ground contacts as, for example, is shown generally at numeral
462. Each of these contacts has a contact section 464 that engages
the forks of the ground/power contacts of the receptacle. These
contacts also have a medial section 466 where it engages the housing
and a solder ball tab 468 for receiving a solder ball 470. The plug also
includes a number of signal contacts as, for example, is shown
generally at numeral 476. Each of these signal contacts includes a
contact section 478 which engages the signal contacts in the
receptacle, a medial section 480 where it engages the housing and a
solder ball tab 482 for receiving a solder ball. Other signal contacts as
at 486 and 488 engage respectively other solder balls as at 490 and
492. The solder ball tabs are formed and solder balls 470, 474, 484,
490 and 492 are applied to the plug in substantially the same manner
as previously described with respect to the receptacle.
In the method of this invention the conductive element will
preferably be a solder ball. Those skilled in the art, however, will
appreciate that it may be possible to substitute other fusible materials
which have a melting temperature less than the melting temperature
of the insulative body. The fusible element can also have a shape
other than a sphere. The solder ball or other conductive element will
also preferably have a diameter which is from about 50 percent to 200
per cent of the width of the recess. This diameter will also preferably
be related to the depth of the recess and be from 50 percent to 200 per
cent of that depth. The volume of the solder ball will preferably be
from about 75 percent to about 150 percent of the volume of the
recess and, more preferably, will be about the same volume as the
recess. The contact tab will extend into the recess by a sufficient
amount to present adequate surface area for the solder ball to fuse to,
and will usually preferably extend into the recess from about 25
CA 02497606 1997-10-10
24
percent to 75 percent and more preferably to about 50 percent of the
depth of the recess as previously mentioned. The recesses ordinarily
will be circular, square or the shape of any other regular polygon in
cross section. When the conductive element is solder, it will
preferably be an alloy which is in the range of about 90%Sn and
10%Pb to about 55%Sn and 45%Pb. More preferably the alloy will be
eutectic which is 63%Sn and 37%Pb and has a melting point of
183 C. Typically, a"hard" solder alloy with a higher lead content
would be used for mating to materials such as ceramics. The "hard"
solder ball will "mushroom" or deform slightly as it softens under
typical SMT conditions, but will not melt. A "soft" eutectic ball is used
for attachment to PCB's and will usually reflow and reform itself under
typical SMT conditions. Other solders known to be suitable for
electronic purposes are also believed to be acceptable for use in this
method. Such solders include, without limitation, electronically
acceptable tin-antimony, tin-silver and lead-silver alloys and indium.
Before the solder ball or other conductive element is positioned in a
recess, that recess would usually be filled with solder paste.
Alternatively, in place of the solder ball previously described, a
body of material which is not fusible at SMT temperatures may be
attached by reflow of the solder paste in the recesses onto the
contacts. The connector mounting interface would comprise a
plurality of infusible spheres in a tightly coplanar array. Such a
connector would be secured on a substrate by conventional SMT
techniques.
While it is believed that a solder paste or cream incorporating
any conventional organic or inorganic solder flux may be adapted for
use in this method, a no clean solder paste or cream is preferred.
Such solder pastes or creams would include a solder alloy in the form
of a fine powder suspended in a suitable fluxing material. This
CA 02497606 1997-10-10
powder will ordinarily be an alloy and not a mixture of constituents.
The ratio of solder to flux will ordinarily be high and in the range of
80% - 95% by weight solder or approximately 80% by volume. A
solder cream will be formed when the solder material is suspended in
5 a rosin flux. Preferably the rosin flux will be a white rosin or a low
activity rosin flux, although for various purposes activated or
superactivated rosins may be used. A solder paste will be formed
when a solder alloy in the form of a fine powder is suspended in an
organic acid flux or an inorganic acid flux. Such organic acids may be
10 selected from lactic, oleic, stearic, phthalic, citric or other similar
acids. Such inorganic acids may be selected from hydrochloric,
hydroflouric and orthophosphoric acid. Cream or paste may be
applied by brushing, screening, or extruding onto the surface which
may advantageously have been gradually preheated to ensure good
15 wetting. Although it has been found that wicking of the solder onto
the contact is significantly reduced when a solder paste or cream is
used, it is believed that paste type solder flux alone may also be used
when a suitable, passivation agent is used. Such a suitable
passivation agents would include fluoride containing solder resist
20 coatings such as FLOURAD which is available from the 3M
Corporation.
Heating is preferably conducted in a panel infra red (IR) solder
reflow conveyor oven. The solder element would ordinarily be heated
to a temperature from about 183 to about 195 C. but, depending on
25 the material of the housing, solders having melting temperatures may
be used. The conveyor oven would preferably be operated at a rate of
speed from about 10 to 14 inches per second and would be moved
through a plurality of successive heating phases for a total time of
about 5 minutes to about 10 minutes. Prior to being inserted into the
conveyor oven the connector housing, contacts and solder elements
CA 02497606 1997-10-10
26
may be preheated at an elevated temperature for at least an hour. In
the conveyor oven a temperature profile would be developed based on
an appropriate peak temperature, maximum slope and time above
reflow temperature. Peak temperature is the highest temperature
reached by the housing. For a solder element with a melting point of
183 C, peak temperature would usually be between 185 C and 195 C.
Maximum slope is measured in C/ sec. and specifies how fast the
connector housing temperature is allowed to change, so as to avoid
warping or bending. For most applications of this method, maximum
positive slope will preferably initially be from about 2 C/sec to 15 C
/ sec. After the wetting point of the solder is reached negative slope
will preferably be -2 C/sec to -15 C/sec. An important aspect of the
method of this invention is that time above reflow is minimized. Time
above reflow is a measure of how long the solder element remains in
its liquid phase. It is found that when time of the solder in its liquid
phase is minimized, wicking of solder from the recess up the contact
is eliminated or significantly reduced. Preferably rise time of
temperature as measured on the board between 180 C and 200 C and
fall time of temperature as measured on the board between 200 C and
180 C will both be from about 10 seconds to about 100 seconds.
While not intending to be bound by any particular theory, it is
believed that during such relatively short periods of time, surface
tension of the liquid solder element will restrain the liquid solder from
flowing through the contact receiving slot in the base of the recess.
After such periods of time, however, the liquid solder will begin to flow
through the contact receiving slot and wick up the contact. Prior to
bringing the temperature of the solder element to its melting
temperature, it may also be advantageous to initially have a relatively
high slope but before melting temperature is reached to slow the rate
of temperature increase or decrease after which a relatively high slope
CA 02497606 1997-10-10
27
is then adopted until the melting temperature is reached. The
selection of an appropriate housing material may also enhance
results. Preferably the housing material will be wholly aromatic liquid
crystal polyester (LCP) with characteristics of high glass transition
temperature, low thermal coefficient, low moisture absorption, high
fracture toughness, good flow and low viscosity, high temperature and
high flash point.
The method of the present invention is further described with
reference to the following examples.
Example 1
An insulative housing for a connector plug and receptacle
substantially is described above in connection with Figs. 1 - 18 was
made. Contacts also substantially in accordance with that description
were also positioned in the housing. These contacts were beryllium
copper and were plated with gold over their entire surface area to a
thickness of 30 microns. The housing material was DUPONT H6130
liquid crystal polymer (LCP). The length and width of the plug were
respectively 52.5mm (including mounting brackets) and 42.36mm.
The recesses on the exterior surfaces of the plug and receptacle
housing were cross sectionally square having a side dimension of
0.62mm and a depth of 0.4mm. About 2mm of the contact extended
into the recess. Other dimensions were generally in proportion to the
above dimensions in accordance with Figs. 1 - 18. On the exterior
sides of both the plug and receptacle the recesses were filled or
substantially filled with CLEANLINE LR 725 no clean solder cream
which is commercially available from Alphametals, Inc. of Jersey City,
New Jersey. Both the plug and receptacle were turned over on their
exterior sides on a quantity of spherical solder balls so that a solder
ball became embedded in each of the recesses. The solder balls used
were ALPHAMETAL no flux 63SN/37PB spherical solder balls which
CA 02497606 1997-10-10
28
had a diameter of .030 inch .001 inch and a weight of approximately
.00195g. The plug and receptacle were then treated with FLUORAD, a
solder anti-wicking material available from 3M Corporation. After
such treatment the plug and receptacle were then dried in a
convection oven for 2 hours at 105 C. The plug and receptacle were
then positioned on separate circuit boards made of conventional
reinforced epoxy printed circuit board material, having thicknesses of
.061 inches. Referring to Fig. 9, a thermocouple was placed on the
exterior surface of the plug in position T. Another thermocouple was
centrally positioned upon the supporting board surface adjacent the
plug. Both the plug and the receptacle were then treated in a panel-
infrared (IR) conveyer solder reflow oven. As is conventional for this
type of oven, the plug and receptacle were moved through six zones in
the reflow oven. The conveyor speed was 13 in/ min. Heating
temperatures in each zone are shown in Table 1. Minimum and
maximum temperatures for the plug and for the supporting board are
shown in Table 2. Both positive and negative maximum slopes are
shown in Table 3. Rise time and fall time measured on the board
between 180 C and 200 C are shown in Table 4. Temperature by time
and distance for the plug is shown in the curve in Fig. 26a wherein
the heavy line is the temperature at the thermocouple on the
supporting board and the light line is temperature at the
thermocouple on the plug exterior surface. A visual inspection of the
plug and the receptacle after solder reflow showed that nearly all the
solder balls had fused to the contact leads in their respective cavities.
Solder ball height above the exterior surfaces of the plug and the
receptacle also appeared to be relatively uniform. There was no
noticeable warping or bending of the housing.
CA 02497606 1997-10-10
29
Example 2
Another plug and receptacle were prepared in essentially the
same way as was described in Example 1 and solder balls were
emplaced in the recesses on the exterior sides. Several hours after the
treatment in the solder reflow oven in Example 1, when atmospheric
conditions were somewhat different, another plug and receptacle
essentially similar to the ones used in Example 1 were subjected to
similar reflow heating as were used in Example 1. Oven conditions
are shown in Table 1. Minimum and maximum temperatures of the
plug and the adjacent supporting board are shown in Table 2. Both
positive and negative maximum slope is shown in Table 3, rise time
and fall time measured on the board between 180 C and 200 C is
shown in Table 4. Temperature by time and distance is shown in Fig.
26b. It will be seen that the curve shown in Fig. 26b is somewhat
different than that shown in Fig. 26a which difference is attributed to
different ambient atmospheric conditions. A visual inspection of the
resulting connector showed similar results to those achieved in
Example 1.
TABLE 1
Temperature ( C)
Example ZONE #1 #2 #3 #4 #5 #6
1 UPPER 350 Unheated 275 230 310 Unheated
1 LOWER Unheated Unheated 275 230 310 Unheated
2 UPPER 350 Unheated 275 230 310 Unheated
2 Lower Unheated Unheated 275 230 710 Unheated
TABLE 2
Connector Board
Example Max Tem ( C) Time (Min. & Sec.) Max Temp ( C) Time (Min 8a
Sec
1 188 4:37.6 ------- -------
1 --- ------- 232 4:19.8
2 191 4:53.2 ------- -------
CA 02497606 1997-10-10
2 --- ------- 229 5:10.4
TABLE 3
Positive and Negative Maximum Slope C (Secl
Connector Board
5 Example Max Time Reached Max Time Reached
(Min & Sec) (Min & Sec)
1 +2 0:50.4 +2 0:30.4
1 -2 6:45.2 -3 5:58.8
10 2 +3 7:08.0 +3 1:14.8
2 -15 6:13.8 -7 6:14.0
TABLE 4
Rise Time and Full Time Between 180 C and 200 C
(Measured on Board)
15 Example Rise Time (Min & Sec) Fall Time (Min &
Sec
1 0:28.8 0:15.2
2 1:31.6 0:40.6
20 Example 3
Another connector was made using essentially the same
conditions as were described in Examples 1 and 2 except that the
specific curves shown in Fig. 26a and 26b may have been somewhat
different because of atmospheric conditions. After the completion of
25 this connector, the solder balls at six locations on the exterior surface
of the plug were examined by Laser Point Range Sensor (PRS)
available from Cyber Optics Corporation of Minneapolis, Minnesota.
Referring to Fig. 9, these locations are identified as areas 27a and 27b
when the laser was directed from Li, as areas 27c and 27d when the
30 laser was directed from L2 and as areas 27e and 27f when the laser
CA 02497606 1997-10-10
31
was directed from L3. At all these areas a laser profile was taken of
the profiles of the five solder balls in each of these areas.
Reproductions of these laser profile are shown in Fig. 27a - 27f. The
height of each of these solder balls at its highest point above the plane
of the exterior side of the plug is shown in Table 3. For each of these
groups the solder ball closest to the front of the plug as shown in Fig.
9 was considered the first position in Table 5 and was the solder ball
on the left of the graphs in Figs. 27a - 27f. An examination of these
results reveals that in each group of five solder balls there was what
was considered to be an acceptable degree of uniformity for the height
of the solder balls.
TABLE 5
POSITION HEIGHT (.001 in.l
GROUP 1 2 3 4 5
27a 18.1 18.9 19.5 19.6 19.1
27b 19.2 18.5 17.6 18.5 18.0
27c 20.4 21.1 21.6 21.1 21.4
27d 19.9 20.1 20.1 21.2 20.5
27e 18.2 18.9 19.3 18.2 18.7
27f 19.1 18.2 19.0 18.2 18.9
Example 4
Another connector was made essentially according to the
conditions described in Examples 1 and 2 except because of
atmospheric conditions the specific curves shown on Figs. 26a and
26b may have been somewhat different. In almost all cases solder
balls were satisfactorily fused to the contact leads and solder balls
were of an acceptably uniform height above the plane of the exterior
surfaces of the plug and receptacle on visual inspection. A stencil
CA 02497606 1997-10-10
32
with a pattern matching the solder balls on both the plug and
receptacle was used to apply solder paste onto conductive solder pads
on two different circuit boards having a thickness of .061 inches. The
plug was positioned on one circuit board and the receptacle was
positioned on the other. The plug and receptacle were then separately
again treated in the conveyor oven under conditions similar to those
described in fusing the solder balls to the contacts except that
conveyor speed was decreased to 11 in/ sec. After cooling, the plug
and receptacle were found to have been satisfactorily fused to their
respective boards. A photograph showing these x-rays of selected
solder balls are attached respectively at Figs. 28a and 28b. Cross
sectional electron microscope photographs were taken to show the
fusing of the solder balls to the signal contact leads and the fusing of
the solder balls to the printed circuit board material. These electron
microscope photographs are shown respectively at Figs. 28c and 28d.
There was only one short between adjacent signal contacts and good
connections were made between the contacts and the solder balls and
between the solder balls and the boards at all other points.
It will be appreciated that electrical connector and the method
of its manufacture has been described in which the connector that
can utilize BGA technologies for mounting on a PWB. Surprisingly
and unexpectedly it was also found that there was a relatively high
degree of uniformity in the profiles of the solder balls and, in
particular, in the weights and/or volume of the solder balls.
While the present invention has been described in connection
with the preferred embodiments of the various figures, it is to be
understood that other similar embodiments may be used or
modifications and additions may be made to the described
embodiment for performing the same function of the present invention
without deviating therefrom. Further, the arrangements described
CA 02497606 1997-10-10
33
can be used with respect to components other than connectors, that
comprise housings formed of insulative materials which carry
elements to be fused onto a PWB or other electrical substrate.
Therefore, the present invention should not be limited to any
single embodiment, but rather construed in breadth and scope in
accordance with the recitation of the appended claims.
