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Description  |
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BACKGROUND OF THE INVENTION
The subject invention relates to a universal production ball grid array
socket for establishing solderless connections between the conductive
bails of a ball grid array package and a printed circuit board. More
particularly, the lead balls of a ball grid array package can be
solderlessly mounted within the contacts of the ball grid array socket.
There currently exists several different methods for packaging
semi-conductor devices. One popular type of semiconductor packaging is
referred to as a quad flat pack (QFP), which is a type of peripheral lead
package. A new type of packaging technology is referred to as the ball
grid array (BGA). The ball grid array was introduced by International
Business Machines Corp. (IBM) and includes a number of benefits including
small package size, good yield, better electrical performance, and lower
profiles, among others.
The BGAs generally place conductive ball leads over entire surface of a
chip, instead of just around the edges. Thus, BGA packages allow system
designers to place more leads in a given package size using looser
tolerances than peripheral lead type packages such as the quad flat pack.
Therefore, board producers are not required to use the fine pitch spacings
that are now necessary for high lead count packages. Also, BGAs have finer
pitch spacings than pin grid arrays (PGA), since the solder balls do not
have the coplanarality problem associated with through-hole PGAs. In the
prior art, the electrical connection between the BGA package and
underlying PC board was generally provided by soldering the ball leads
which are located underneath the BGA package onto pads which are provided
on the upper surface of printed circuit boards.
In many applications the soldering of the ball leads of the ball grid array
package to the printed circuit board is undesirable. For example, it is
impossible to visually locate a short or ground between the ball grid
array package and printed circuit board. Usually, an expensive X-ray
technique is required to inspect the connections since the ball leads are
hidden under the ball grid array package. Further, the increasing number
of ball leads being provided by ball grid array packages makes the
soldering of the ball grid array packages to printed circuit boards more
difficult.
Accordingly, in the prior art, an improved connector has been developed
which is designed to eliminate the need for the soldering the ball leads
of a BGA package to a printed circuit board. One example of a device which
satisfied this criteria is the fuzz ball socket. The fuzz ball socket
comprises a plurality of electrical contacts mounted within an insulated
housing. Each contact resembles a brillo pad, made up of individual gold
plated wires, forced into a through hole of the insulated housing. Using a
great deal of pressure the fuzz ball socket can be forced down and bolted
onto a PC board, thereby providing the proper electrical contact. The BGA
package is then placed in the fuzz ball socket, a metal cover is placed on
top of the BGA package and a great deal of pressure is exerted on the
cover to force the ball leads of the BGA package into the proper
electrical connection with the fuzz ball socket.
In many applications, the necessity of using a great deal of pressure to
force the ball leads of a BGA package into a fuzz ball socket is
undesirable. For example, the number of ball leads placed on a BGA package
are increasing, thereby making the mounting of a BGA package within a fuzz
ball socket increasingly difficult since greater and greater pressure is
required to create a proper electrical connection. Further, the great
force required to push the ball leads into contact with the fuzz ball
socket creates wear on the BGA ball leads and increases the likelihood of
distorting the ball leads. Additionally, the manufacture of a fuzz ball is
very expensive since wire must be individually wired into each through
hole.
It is therefore an object of the subject invention to provide a universal
production ball grid array socket which eliminates the necessity to solder
the conductive ball leads of a BGA package to the contacts of a printed
circuit board.
It is another object of the subject invention to provide a universal
production ball grid array socket which reduces the large amount of
pressure required to mount a BGA package onto a BGA socket.
It is still another object of the subject invention to provide a universal
production ball grid array socket having a unique resilient electrical
contact capable of achieving electrical connection between the contact of
a circuit board and the conductive ball lead of a BGA package. In
particular, a socket is disclosed having a contact which resiliently
expands to electrically engage conductive ball leads of varying diameters.
It is a further object of the subject invention to provide a universal ball
grid array socket wherein the ball grid array package is positively locked
within the housing of the ball grid array socket thereby preventing the
degradation of the electrical connection due to vibration or other
disturbance.
It is an object of the second embodiment of the subject invention to
provide a coverless universal ball grid array socket having resilient
contacts for clasping the ball leads of a BGA package thereby establishing
a relatively high retentive force and preventing the degradation of
electrical connection due to vibration or other disturbance.
It is an object of the third embodiment of the subject invention to provide
a coverless universal ball grid array socket having resilient contacts for
clamping the ball leads of the ball grid array package where only a slight
portion of the resilient contact is utilized as a means for preventing
contact slippage within the universal ball grid array socket.
It is an object of the fourth embodiment of the subject invention to
provide a coverless translucent ball grid array socket which allows for
quick and easy inspection of a ball grid array package and ball grid array
socket combination.
An additional object of the subject invention is to provide a method for
mounting ball leads onto a ball grid array socket.
SUMMARY OF THE INVENTION
In accordance with these and many other objects, the subject invention
provides for a universal production ball grid array socket assembly for
receiving a ball grid array package having an array of conductive ball
leads. The socket assembly includes a generally rectangular,
non-conductive housing having a carrier base, a plurality of upstanding
side walls, and a cover. The carrier base has an upper surface, a lower
surface, and a plurality of apertures corresponding to the plurality of
conductive ball leads of the ball grid array package. Each aperture
extends through the carrier base and is defined by an inner surface. The
side walls define an insert area in which the ball grid array package can
be placed. The cover is for retaining the ball grid array package placed
in the insert area and for forcing the ball grid array package into
electrical contact with the ball grid array socket. A plurality of
tulip-shaped conductive ball receiving contacts are provided with each
ball receiving contact mounted within an aperture of the carrier base.
Each ball receiving contact includes a split collar having a plurality of
upwardly extending resilient cantilevered leaves, a plurality of
downwardly extending cantilevered tangs, and a downwardly extending
cantilevered blade. The resilient cantilevered leaves of each ball
receiving contact are for releasably receiving and electrically engaging a
ball lead of an inserted ball grid array package. The cantilevered tangs
of each ball receiving contact engage the inner surface of the aperture in
an interference fit. The cantilevered blade of each ball receiving contact
is for engagement with an underlying semi-conductor device.
In a second embodiment of the subject invention there is provided a
coverless ball grid array socket assembly which clasps an inserted ball
grid array package into position. In particular, the socket assembly
includes a generally rectangular, non-conductive carrier base having a
plurality of apertures. Each aperture is defined by an inner surface and
extends through the carrier base. A plurality of conductive ball receiving
contacts are provided with each contact being mounted within an aperture
of the carrier base.
Each ball receiving contact includes a base plate having an upper surface
and a lower surface, two opposing cantilevered resilient arms extending
upwardly from the base plate and two opposing resilient tangs extending
upwardly from the base plate for engaging the inner surface of the
surrounding aperture in an interference fit. Each resilient cantilevered
arm of the ball receiving contact has a clasping mechanism for clasping a
ball lead of an inserted ball grid array package. By this arrangement, the
ball lead of an inserted ball grid array package is retained by and
electrically engaged with the ball receiving contact without use of a
cover. A conductive ball lead may be mounted to the lower surface of the
base plate of the ball receiving contact for connection to an underlying
semi-conductor device.
In a third embodiment of the subject invention there is provided a
coverless ball grid array socket assembly which clasps an inserted ball
grid array package into position through a plurality of conductive
resilient ball receiving contacts. In particular, the socket assembly
includes a generally rectangular, non-conductive carrier base having a
plurality of apertures. Each aperture is defined by an inner surface and
extends through the carrier base. A plurality of conductive ball receiving
contacts are provided with each contact being mounted within an aperture
of the carrier base.
Each ball receiving contact includes a base plate having an upper surface
and a lower surface, two opposing cantilevered resilient arms extending
upwardly from the base plate and four resilient tabs projecting slightly
above the upper surface of the base plate for engagement with the inner
surface of the surrounding aperture in an interference fit. Each resilient
cantilevered arm of the ball receiving contact has a clasping mechanism
for clasping a ball lead of an inserted ball grid array package. By this
arrangement, the ball lead of an inserted ball grid array package is
retained by and electrically engaged with the ball receiving contact
without use of a cover. A conductive ball lead may be mounted to the lower
surface of the base plate for connection to an underlying semi-conductive
device.
In a fourth embodiment of the subject invention there is provided a
coverless translucent ball grid array socket assembly which clasps an
inserted ball grid array package into position through a plurality of
conductive resilient ball receiving contacts. In particular, the socket
assembly includes a generally rectangular translucent non-conductive
carrier base having an upper surface, a lower surface and a plurality of
apertures. Each aperture extends through the carrier base and is defined
by an inner surface. A plurality of conductive ball receiving contacts are
provided with each contact being mounted to the lower surface of the
carrier base and extending within an aperture of the carrier base.
Each ball receiving contact includes an elongated base plate having a top
surface, a bottom surface, and a length which is greater than the diameter
of the carrier base aperture. Portions of the top surface of the elongated
base plate are mounted to the lower surface of the carrier base. The ball
receiving contact further includes two opposing cantilevered resilient
arms which extend upwardly from the elongated base and into an aperture of
the carrier base. Each resilient cantilevered arm has a clasping mechanism
for clasping a ball lead of an inserted ball grid array package. By this
arrangement, the ball lead of an inserted ball grid array package is
retained by and electrically engaged with the ball receiving contact
without use of a cover. The ball receiving contact may further include a
conductive ball lead mounted to the bottom surface of the elongated base
plate for engagement with an underlying semi-conductor device.
A method for the subject invention is provided for mounting a plurality of
ball leads onto a ball grid array socket comprising the steps of mounting
a plurality of ball receiving contacts within a plurality of apertures of
a carrier base, the carrier base having a bottom surface and each ball
receiving contact mounted within a corresponding aperture such that the
bottom surface of each ball receiving contact is flush with the bottom
surface of the carrier base to create a contact grid having contact areas
and non-contact areas; inverting the carrier base; and depositing a
plurality of ball leads onto the inverted carrier base, each ball lead
deposited on the bottom surface of each ball receiving contact in the
contact grid.
In summary, there is provided a universal production ball grid array socket
assembly having tulip-shaped ball receiving contacts which allow ball grid
array packages having ball leads of varying diameters to be solderlessly
mounted to an underlying circuit board.
In summary, the second embodiment of the subject invention provides a
coverless universal ball grid array socket having ball receiving contacts
which clasp the ball leads of the ball grid array package with a
substantial retentive force.
In summary, the third embodiment of the subject invention provides a
coverless universal production ball grid array socket having clasping ball
receiving contacts which have four slightly projecting tabs for mounting
the ball receiving contacts within the universal production ball grid
array socket of the subject invention.
In summary, the fourth embodiment of the subject invention provides a
translucent coverless ball grid array socket which allows for quick and
easy inspection of a ball grid array package and a ball grid array socket
combination.
In summary, a method for the subject invention is provided for mounting a
plurality of ball leads onto a ball grid array socket.
Other objects of the invention will become apparent from the following
description in connection with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is an exploded perspective view of the ball grid array socket of the
subject invention.
FIG. 1A is a side elevational view, partially in section, of a ball grid
array package taken along line 1A--1A in FIG. 1.
FIG. 2 is an exploded perspective view, partially in section, of a first
embodiment of the subject invention.
FIG. 3 is a perspective view of a tulip-shaped ball receiving contact of
the first embodiment of the subject invention.
FIG. 4 is a side elevational view of a tulip-shaped ball receiving contact
of the first embodiment of the subject invention.
FIG. 5 is a front view of a tulip-shaped ball receiving contact of the
first embodiment of the subject invention.
FIG. 6 is a top plan view of a tulip-shaped ball receiving contact of the
first embodiment of the subject invention.
FIG. 7 is an exploded side elevational view, partially in section, of a
ball grid array lead disengaged from a tulip-shaped ball receiving contact
of the first embodiment of the subject invention.
FIG. 7A is a side elevational view, partially in section, of a ball grid
array lead engaged with a tulip-shaped ball receiving contact of the first
embodiment of the subject invention.
FIG. 8 is an exploded perspective view of a ball grid array lead disengaged
from a dual contact of the second embodiment of the subject invention.
FIG. 9 is a side elevational view of a dual contact of the second
embodiment of the subject invention.
FIG. 10 is a side elevational view, partially in section, of a ball grid
array lead engaged with a dual contact of the second embodiment of the
subject invention.
FIG. 11 is an exploded perspective view of a ball grid array lead
disengaged from a ball receiving contact of the third embodiment of the
subject invention.
FIG. 12 is a side elevational view, partially in section, of a ball grid
array lead engaged with a ball receiving contact of the third embodiment
of the subject invention.
FIG. 13 is an exploded perspective view of a ball grid array lead
disengaged from a ball receiving contact of the fourth embodiment of the
subject invention.
FIG. 14 is a side elevational view, partially in section, of a ball grid
array lead engaged with a ball receiving contact of the fourth embodiment
of the subject invention.
FIG. 15 is a perspective view of the ball receiving contact of the fourth
embodiment of the subject invention with continuous front and rear edges.
FIG. 16A-D illustrates a method of mounting ball leads to a ball grid array
socket utilizing a solder resist.
FIG. 17A-E illustrates a method of mounting ball leads to a ball grid array
socket utilizing a dry resist.
DETAILED DESCRIPTION OF THE INVENTION
Referring to FIGS. 1 and 1A, the present invention is indicated generally
by the reference numeral 10. A ball grid array package 12 typically
consists of a semi-conductor device 14 and a plurality of ball leads 16
extending downwardly from the bottom surface 18 of the semi-conductor
device 14.
The present invention 10 includes a non-conductive base 20 and a plurality
of walls 22 extending upwardly from the base 20. The base 20 and the
plurality of walls 22 define an insert area 24 in which the ball grid
array package 12 can be placed. A plurality of apertures 26 extend through
the base 20 of the ball grid array socket 10. Additionally, the present
invention includes a cover 28 which can be mounted to the upper surfaces
30 of the plurality of walls 22 through a plurality of screws 32. In
particular, the plurality of screws 32 are screwed through a plurality of
apertures 34 which extend through the cover and into a plurality of
threaded holes 36 which extend into the plurality of walls 22.
As explained in further detail below, a ball grid array package 12 can be
mounted to the ball grid array socket 10 of the subject invention by
placing the ball grid array package 12 in the insert area 24 of the ball
grid array socket 10. The cover 28 is then mounted on top of the ball grid
array package 12 and ball grid array socket 10 combination by the
plurality of screws 32.
Turning to FIG. 2, the cooperation between a ball lead 16 of the ball grid
array 12 and an aperture 26 of the ball grid array socket 10 is shown in
greater detail. The aperture 26 of the ball grid array socket 10 is
tapered and is defined by an inner surface 40. The tapered aperture 26 has
a maximum diameter adjacent the upper surface 42 of the base 20 and has a
minimum diameter adjacent the lower surface 44 of the base 20. A
tulip-shaped ball receiving contact 46 engages the inner surface of the
tapered aperture 26 in an interference fit. As explained in further detail
below, as each ball lead 16 of the ball grid array 12 enters its
respective tapered aperture 26 in the ball grid array socket 10 the ball
lead 16 engages the upper portion of the tulip-shaped ball receiving
contact 46.
Turning to FIGS. 3-6, the tulip-shaped ball receiving contact 46 of the
first embodiment of the subject invention is shown in greater detail. The
tulip-shaped ball receiving contact 46 includes a split collar 48 from
which a plurality of upwardly extending cantilevered leaves 50 extend. The
tulip-shaped ball receiving contact 46 also includes a plurality of
cantilevered tangs 52 and a single cantilevered blade 54 extending
downwardly from the split collar 48. The tulip-shaped ball receiving
contact 46 may be formed from any known resilient conductive material. One
example being heat-treated beryllium copper.
As seen in FIGS. 3 and 6, each leaf 50 of the tulip-shaped ball receiving
contact 46 has a shallow V-shaped configuration with the apex of the V
extending toward the center axis of the split collar 48. The upper inner
portions 56 of each leaf 50 define the primary contact points between the
tulip-shaped ball receiving contact 46 and an inserted ball lead 16 of a
ball grid array package 12.
The plurality of tangs 52 extend downwardly from the split collar 48. Each
tang extends beyond the outer surface 60 of the split collar 48. The tangs
52 become compressed when the tulip-shaped ball receiving contact 46 is
inserted into the tapered aperture 26 of the base 20. This compression of
the tangs 52 results in an interference fit between the tulip-shaped ball
receiving contact 46 and the inner surface 40 of the tapered aperture 26.
This interference fit prohibits shifting of the tulip-shaped ball
receiving contact 46 during engagement and disengagement with a ball lead
16 of the ball grid array package 12.
The cantilevered blade 54 extends downwardly from the split collar 48 and
includes a projection 62. This cantilevered blade 54 can be plugged into a
socket of an underlying device or bent over and bolted to an underlying
circuit board. Additionally, the blade 54 can be bent over and trimmed so
that only the projection 62 is present. The projection 62 can then be
soldered to an underlying electrical component.
Referring to FIGS. 7 and 7A, the ball grid array ball lead 16 and
tulip-shaped ball receiving contact 46 combination is shown. In general,
the ball lead 16 of the ball grid array package 12 and the ball receiving
contact 46 move from a disengaged position where the ball grid array
package 12 is inserted into the insert area 24 of the ball grid array
socket 10 (FIG. 1) to an engaged position where the ball grid array
package 12 is clamped into place by mounting the cover 28 onto the ball
grid array package 12 and ball grid array socket 10 combination.
Turning to FIG. 7, the disengaged position of the tulip-shaped ball
receiving contact 46 and the ball lead 16 is shown. At the disengaged
position the ball lead 16 is spaced a distance from the tulip-shaped ball
receiving contact 46. The resilient leaves 50 of the tulip-shaped ball
receiving contact 46 are at rest and spaced apart at a distance less than
the diameter of the ball lead 16 of the ball grid array package 12. The
upper most portions of the cantilevered leaves 50 are flush with the upper
surface 42 of the base 20. The cantilevered blade 54 of the tulip-shaped
contact 46 projects below the lower surface 44 of the base 20 for
engagement with an underlying electrical device.
Turning now to FIG. 7A, the engaged position of the tulip-shaped ball
receiving contact 46 and the ball lead 16 is shown. In the engaged
position the ball lead 16 engages the upper inner portions 56 of the
cantilevered leaves 50 of the tulip-shaped ball receiving contact 46. In
particular, the resilient leaves 50 bend away from the ball lead 16 that
the tulip-shaped ball receiving contact 46 is receiving. Accordingly, the
upper inner surface 56 of each leaf 50 wipes the ball lead 16 and engages
in an electrical connection with the ball lead 16. As a result, a
plurality of electrical connections of high integrity are created as the
ball lead 16 is received within the plurality of leaves 50 of the
tulip-shaped ball receiving contact 46. It should be noted that the leaves
50 never bend far enough so as to exceed the elastic limit of the material
from which the tulip-shaped ball receiving contact 46 is made or bend far
enough so as to come into contact with the inner surface 40 of the tapered
aperture 26.
Turning to FIGS. 8-10, the second embodiment of the ball receiving contact
of the subject invention is illustrated and is designated generally by the
reference numeral 70. The dual contact 70 comprises a base 72 having an
upper surface 74 and a lower surface 76. A pair of cantilevered resilient
opposing arms 78 and a pair of cantilevered resilient opposing tangs 80
extend upwardly from the upper surface 74 of the base 72. The lower
surface 76 of the base may be in the form of a well 82. A ball lead 84 may
be soldered onto the lower surface 76 of the base 72 after the dual
contact 70 has engaged the inner surface 40 of the tapered aperture 26 in
a strong interference fit. The dual contact 70 may be formed from any
known resilient conductive material. One example being heat-threaded
beryllium copper.
As shown in FIG. 8, each resilient upwardly extending cantilevered arm 78
further includes a clasping mechanism. The preferred clasping mechanism is
a tapered aperture 86 disposed adjacent the free end of the cantilevered
arm 78.
The opposing pair of resilient tangs 80 are spaced apart at such a distance
so as to ensure a strong interference fit between the dual contact 70 and
the inner surface 40 of the tapered aperture 26. In particular, the dual
contact 70 is inserted through the tapered aperture 38 adjacent the upper
surface 42 of the base 20 of the ball grid array socket 10. The dual
contact 70 is pressed into the aperture 26 until the base 72 of the dual
contact 70 is flush with the lower surface 44 of the base 20 of the ball
grid array socket 10. At this point the tangs 80 are engaged in an
interference fit of sufficient strength with the inner surface 40 of the
aperture 26 so as to ensure that the dual contact 70 remains in place as
it engages and disengages a ball lead 16 of the ball grid array package
12. After the dual contact 70 engages the inner surface 40 of the tapered
aperture 38 a ball lead 84 may be soldered onto the base 72 of the dual
contact 70. The ball lead 84 may then be mounted to an underlying circuit
board. The soldering of the ball lead 84 onto the base 72 of the dual
contact 70 further strengthens the engagement of the dual contact lead 70
with the base 20 of the ball grid array socket 10 since the ball lead 84
is of a greater diameter than the minimum diameter of the tapered aperture
26 adjacent the lower surface 44 of the base 20. In other words, the ball
lead 84 cannot be pulled through the tapered aperture 26 as the ball lead
16 is removed from the dual contact 70.
Referring to FIGS. 8 and 10, the disengaged and engaged positions of the
ball grid array ball lead 16 and of the dual contact 70 are shown. In
general, the ball lead 16 and dual contact 70 are in a disengaged position
when the ball grid array package 12 is placed into the insert area 24 of
the ball grid array 10 (see FIG. 1). The ball lead 16 and dual contact 70
are in an engaged position when a slight force is exerted on the ball grid
array package 12 causing each dual contact 70 to clasp its respective ball
lead 16.
Turning to FIG. 8, the disengaged position of the dual contact 70 and ball
lead 16 is shown. In the disengaged position the ball lead 16 is spaced a
distance from the dual contact 70. The pair of opposing resilient arms 78
of the dual contact 70 are at rest and spaced apart at a distance less
than the diameter of the ball lead 16 of the ball grid array package 12.
Turning to FIG. 10, the engaged position of the dual contact 70 and ball
lead 16 is shown. In the engaged position the ball lead 16 is clasped
between each inner surface 88 of the clasping aperture 86. In going from
the disengaged position to the engaged position the ball lead 16 initially
causes the opposing arms 78 to resiliently expand away from each other as
the ball lead 16 is inserted between them. However, when the ball lead 16
is pressed between each clasping aperture 86 the opposing arms 78 spring
shut thus clasping the ball lead 16 between the inner surfaces 88 of the
clasping aperture 86. It should be noted that the retentive force exerted
by each dual contact 70 is significantly greater than the initial
insertion force required to press a ball lead 16 into engagement with the
dual contact 70. As a result, a ball grid array socket 10 employing the
second embodiment of the ball receiving contact 70 does not require a
cover to ensure proper engagement between the ball grid array package 12
and ball grid array socket 10.
Turning to FIGS. 11-12, the third embodiment of the ball receiving contact
of the subject invention is illustrated and is designated generally by the
reference numeral 90. The ball receiving contact 90 comprises a base 92
having an upper surface 94 and a lower surface 96. A pair of cantilevered
resilient opposing arms 98 extend upwardly from the upper surface 94 of
the base 92. Two opposing pairs of tabs 100 project slightly from the
upper surface 94 of the base 92. A ball lead 102 may be soldered onto the
lower surface 96 of the base 92 after the ball receiving contact 90 has
engaged the inner surface 40 of the tapered aperture 26 in a strong
interference fit. The ball receiving contact 90 may be formed from any
known resilient conductive material. One example being heat-treated
beryllium copper.
As shown in FIG. 11, each resilient upwardly extending cantilevered arm 98
further includes a clasping mechanism. The preferred clasping mechanism
for the third embodiment of the ball receiving contact is a bifurcated
annular contact 104 disposed adjacent the free end of the cantilevered arm
98.
The opposing pairs of upwardly projecting tabs 100 are spaced apart at such
a distance so as to ensure a strong interference fit between the ball
receiving contact 90 and the inner surface 40 of the tapered aperture 26.
In particular, the ball receiving contact 90 is inserted through the
tapered aperture 26 at its maximum diameter, i.e., adjacent the upper
surface 42 of the base 20 of the ball grid array socket 10. The ball
receiving contact 90 is pressed into the aperture 26 until the contact
base 92 is flush with the lower surface 44 of the base 20 of the ball grid
array socket 10. At this point the opposing pairs of tabs 100 are engaged
in an interference fit of sufficient strength so as to ensure that the
ball receiving contact 90 remains in place as it engages and disengages a
ball lead 16 of the ball grid array package 12. After the ball receiving
contact 90 is engaged with the inner surface 40 of the aperture 26 in an
interference fit a conductive lower ball lead 102 may be soldered onto the
lower surface 96 of the base 92. The ball lead 102 may then be mounted to
an underlying circuit board.
Referring again to FIGS. 11 and 12, the disengaged and engaged positions of
the ball grid array ball lead 16 and the ball receiving contact 90 of the
ball grid array socket 10 are shown. In general, the ball lead 16 and the
ball receiving contact 90 are in a disengaged position when the ball grid
array package 12 is first placed in the insert area 24 of the ball grid
array socket 10 (see FIG. 1). The ball lead 16 and the ball lead receiving
contact 90 are in an engaged position when a slight force is exerted on
the ball grid array package 12 causing each ball lead receiving contact 90
to clasp its respective cooperating ball lead 16.
Referring to FIG. 11, the disengaged position of the ball receiving contact
90 and ball lead 16 is shown. In the disengaged position the ball lead 16
is spaced a distance from the ball receiving contact 90. The pair of
opposing resilient arms 98 of the ball receiving contact 90 are at rest
and spaced apart at a distance less than the diameter of the ball lead 16
of the ball grid array package 12.
Referring to FIG. 12, the engaged position of the ball receiving contact 90
and the ball lead 16 is shown. In the engaged position the ball lead 16 is
clasped between the bifurcated annular contacts 104 of the resilient arms
98. In moving from the disengaged position to the engaged position the
ball lead 16 initially causes the opposing arms 98 to resiliently expand
away from each other as the ball lead 16 is inserted between them.
However, when the ball lead is pressed between each bifurcated annular
contact point 104 the opposing arms 98 spring towards each other thus
clasping the ball lead 16 between the bifurcated annular contact points
104 of the opposing resilient arms 98. It should be noted that the
retentive force exerted by each ball receiving contact 90 is significantly
greater than the initial insertion force required to press a ball lead 16
into engagement with a ball receiving contact 90. As a result, a ball grid
array socket 10 employing the third embodiment of the ball receiving
contact 90 does not require a cover to ensure proper engagement between
the ball grid array package 12 and ball grid array socket 10.
Additionally, it should be noted that the tabs 100 of the third embodiment
of the ball receiving contact 90 are manufactured from significantly less
material than the tangs 80 of the second embodiment of the ball receiving
contact 90. As a result, the third embodiment of the ball receiving
contact 90 can be mass produced at a cost that is significantly less than
the cost to mass produce the second embodiment of the ball receiving
contact 90.
Turning to FIGS. 13 and 14, the fourth embodiment of the ball receiving
contact of the subject invention is illustrated and is designated by the
reference numeral 110. The ball lead receiving contact 110 comprises an
elongated base 112 having an upper surface 114, a lower surface 116, a
front edge 118, a rear edge 120 and opposing side edges 122, 124. A
cantilevered resilient arm 126 extends upwardly from each side edge 122,
124. The front and rear edges 118, 120 may have a plurality of annular
projections 128, FIG. 13, or may be a continuous arc 130, FIG. 15. As seen
in FIG. 14, the distance between the front edge 118 and the rear edge 120
is greater than the minimum diameter of the aperture 26. Accordingly, the
ball receiving contact 110 does not engage in an interference fit with the
aperture 26 that it is inserted within. A dry film 132 is used to connect
the elongated base 112 to the lower surface 44 of the base 20 of the ball
grid array socket 10. As a result, there is no pressure put on the inner
surface 40 of the apertures 26. This is a critical aspect of this fourth
embodiment of the ball receiving contact 110 because it allows the carrier
base 20 of the subject invention to be manufactured from a translucent
material containing a high percentage of glass. In particular, the lack of
internal pressure caused by the lack of the friction fittings in the
apertures 26 is critical because pressure caused by friction fittings
would shatter a carrier base 20 formed from a translucent material. A ball
lead 134 may be soldered onto to the lower surface 116 of the base 112 of
the ball receiving contact 110 after the ball receiving contact 110 has
been connected by the dry film 132 to the lower surface 44 of the carrier
base 20.
As shown in FIG. 13, each resilient upwardly extending cantilevered arm 126
further includes a clasping mechanism. The preferred clasping mechanism
for the fourth embodiment of the ball receiving contact 110 is a
bifurcated annular contact point 136 disposed adjacent the free end of the
cantilevered arm 126.
Referring to FIGS. 13 and 14, the disengaged and engaged positions of the
ball grid array ball lead 16 and of the ball receiving contact 110 are
shown. In general, the ball lead 16 and ball receiving contact 110 are in
a disengaged position when the ball grid array package 12 is first placed
into the insert area 24 (see FIG. 1) of the ball grid array socket 10. The
ball lead 16 and ball receiving contact 110 enter into an engaged position
when a slight force is exerted on the ball grid array package 12 causing
each ball receiving contact 110 to clasp its respective cooperating ball
lead 16.
Turning to FIG. 14, the disengaged position of the ball receiving contact
110 and ball lead 16 is shown. In the disengaged position the ball lead 16
is spaced a distance from the ball receiving contact 110. The pair of
opposing resilient arms 126 of the ball lead receiving contact 110 are at
rest and spaced apart at a distance less than the diameter of the ball
lead 16 of the ball grid array package 12.
Turning to FIG. 14, the engaged position of the ball receiving contact 110
and ball lead 16 is shown. In the engaged position the ball lead 16 is
clasped between the bifurcated annular contacts 136 of the resilient arms
126. In moving from the disengaged position to the engaged position the
ball lead 16 initially causes the opposing arms 126 to resiliently expand
away from each other as the ball lead 16 is inserted between them.
However, when the ball lead 16 is pressed between each bifurcated annular
contact point 136 the opposing arms 126 spring back towards each other
thus clasping the ball lead 16 between their bifurcated annular contact
points 136. It should be noted that the retentive force exerted by each
ball receiving contact 110 is significantly greater than the initial
insertion force required to press a ball lead 16 into engagement with the
ball receiving contact 110. As a result, a ball grid array socket 10
employing the fourth embodiment of the ball receiving contact 110 does not
require a cover to ensure proper electrical engagement between the ball
grid array package 12 and ball grid array socket 10.
Referring now to FIGS. 16A-16D, a method for mounting a plurality of ball
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