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Socket for semi-permanently connecting a solder ball grid array device using a dendrite interposer    
United States Patent5691041   
Link to this pagehttp://www.wikipatents.com/5691041.html
Inventor(s)Frankeny; Richard Francis (Elgin, TX); Frankeny; Jerome Albert (Taylor, TX); Massey; Danny Edward (Georgetown, TX); Vanderlee; Keith Allan (Austin, TX)
AbstractA socket for attaching a flip chip die or ball grid array devices to a printed circuit board substrate having a pattern of solder covered lands, with resources for removing the flip chip die or ball grid array device, resources for directly aligning the solder balls of the flip chip die or ball grid array device to the printed circuit board, resources for using an interposer of dendrite coated vias or pads to electrically and physically connect the solder balls of the flip chip die or ball grid array devices to the solder deposits of the printed circuit board, resources for having the interposer reconfigure the wiring for testing or replacement purposes, resources for utilizing the flexibility and resilience of the interposer to improve dendrite connections, and resources for heat sinking the flip chip die or ball grid array device by direct thermal contact. The socket applies an evenly distributed force to connect the aligned flip chip die or ball grid array device solder ball pattern to the underlying printed circuit board solder deposit pattern through dendrite penetration of the solder using an interposer situated between and aligned to each such solder pattern.
   














 Title Information Submit all comments and votes
 
Patent Text Patent PDF Print Page Summary File History
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Drawing from US Patent 5691041
Socket for semi-permanently connecting a solder ball grid array device

     using a dendrite interposer - US Patent 5691041 Drawing
Socket for semi-permanently connecting a solder ball grid array device using a dendrite interposer
Inventor     Frankeny; Richard Francis (Elgin, TX); Frankeny; Jerome Albert (Taylor, TX); Massey; Danny Edward (Georgetown, TX); Vanderlee; Keith Allan (Austin, TX)
Owner/Assignee     International Business Machines Corporation (Armonk, NY)
Patent assignment
All assignments
Publication Date     November 25, 1997
Application Number     08/536,880
PAIR File History     Application Data   Transaction History
Image File Wrapper   Patent Term   Fees
Litigation
Filing Date     September 29, 1995
US Classification     428/209 257/712 257/727 361/714 361/725 428/901 439/71 439/74 439/75
Int'l Classification     B32B 003/00 H01R 004/58 H05K 005/00 H05K 007/16
Examiner     Lam; Cathy F.
Assistant Examiner    
Attorney/Law Firm     Salys; Casimer K.
Address
Parent Case    
Priority Data    
USPTO Field of Search     428/209 428/901 257/706 257/712 257/704 257/727 439/74 439/75 439/71 361/725 361/714 427/282
Patent Tags     socket semi-permanently connecting solder ball grid array device dendrite interposer
   
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 U.S. References
 
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 Technical Review Submit all comments and votes
 Claims Submit all comments and votes
 


We claim:

1. A socket apparatus, comprising:

a planar interposer of flexible dielectric material having a multiplicity of vias or pads covered with dendrites, which vias or pads are distributed in an array pattern substantially conforming to an array pattern of balls on a surface of an electronic ball grid array device;

a rigid cap with a planar surface alignable to be substantially coplanar with the surface of the ball grid array device;

means for aligning the array pattern of balls on the ball grid array device with the planar interposer and with an array pattern of contact regions on a board; and

means for translating the cap to compress the ball grid array device, the interposer, and the contact regions of the board adequately to cause dendrite penetration into ball grid array device balls and contact regions on the board.

2. The apparatus recited in claim 1, further comprising:

a stiffener with a planar surface; and

means for positioning the cap planar surface and the stiffener planar surfaces to be substantially coplanar.

3. The apparatus recited in claim 1, wherein the means for aligning is a set of alignment pins located with reference to the contact regions on the board.

4. The apparatus recited in claim 2, wherein the means for aligning is a set of alignment pins located with reference to the contact regions on the board.

5. The apparatus recited in claim 3, wherein the planar interposer is comprised of multiple layers with patterned electrical paths connecting selected vias or pads.

6. The apparatus recited in claim 4, wherein the planar interposer is comprised of multiple layers with patterned electrical paths connecting selected vias or pads.

7. The apparatus recited in claim 5, wherein the pattern of contact regions on the board is comprised of solder lands.

8. The apparatus recited in claim 6, wherein the pattern of contact regions on the board is comprised of solder lands.

9. The apparatus recited in claim 1, wherein the means for translating is selectively adjustable as to compression and applies force central to the cap.

10. The apparatus recited in claim 2, wherein the means for translating is selectively adjustable as to compression and applies force central to the cap.

11. The apparatus recited in claim 9, wherein the means for aligning the pattern of balls on the surface of the ball grid array device mates with the balls of the ball grid array device.

12. The apparatus recited in claim 10, wherein the means for aligning the pattern of the balls on the surface of the ball grid array device mates with the balls of the ball grid array device.

13. The apparatus recited in claim 3, wherein the means for translating is selectively adjustable as to compression and applies force central to the cap.

14. The apparatus recited in claim 4, wherein the means for translating is selectively adjustable as to compression and applies force central to the cap.

15. The apparatus recited in claim 14, wherein the alignment pins are connected to the stiffener for extension through and alignment with the board, and the cap is a thermally conductive heat sink.

16. The apparatus recited in claim 15, wherein the planar interposer is composed of multiple layers of patterned electrical paths connecting selected vias or pads.
 Description Submit all comments and votes
 


CROSS REFERENCE TO RELATED APPLICATIONS

The invention in the present application is related to the subject matter in copending U.S. patent application Ser. No. 08/352,301, filed Dec. 7, 1994. The applications are commonly assigned.

FIELD OF THE INVENTION

The present invention relates generally to the connection of the electronic devices. More particularly, the invention is directed to a socket which reliably connects a ball grid array configured electronic device to a printed circuit board substrate having a corresponding connection pattern, yet facilitates easy removal of the electronic device for replacement or the like.

BACKGROUND OF THE INVENTION

Shrinking integrated circuit dimensions and increasing functionality have dramatically increased the input/output connections of die packages while decreasing the contact pitch. These trends have led to die packaging technologies which utilize ball grid array input/output connections, in contrast to the peripherally located pin technologies characterizing conventional designs. A particularly efficient input/output connection technique for integrated circuit die is the flip chip technology, where the ball grid array is formed onto the die body. Integrated circuit die packages using arrays of pins instead of balls do exist, but they are very expensive, susceptible to damage, and require complex mating sockets.

Multi-chip module technology represents another packaging application where fine pitch ball grid array connections are finding increased use. Again, connection of the module ball grid array to the electronic system printed circuit board has proven to be a challenge if removal of the module with reasonable effort is contemplated.

Ball grid array modules or flip chip die are conventionally attached to correspondingly arranged arrays of copper lands on printed circuit boards through solder reflow techniques. Typically, low temperature solder or low temperature solder paste predeposited on the printed circuit board is reflowed to make the connections to high temperature solder balls formed on the ball grid array module or flip chip die.

The use of a ball grid array to connect modules or die to a printed circuit board materially increases the relative density of connections attainable when compared to peripheral pin or pin grid array packages. Unfortunately, ball grid array configured modules and die suffer in two respects. First, it is difficult to make reliable temporary connections to the balls of the die or modules for purposes such as testing or burn-in. Secondly, if a defective connection occurs between a solder ball of the grid and a printed circuit board land during reflow attachment it is difficult to locate and correct the defective solder connection. In most cases, the complete module or flip chip die must be desoldered.

Developers of the assignee recently discovered that palladium dendrites formed by plating metal vias or pads can be used to make reliable connections between the vias or pads and solder balls of modules or die. Connections between dendrite covered pads or via ends and solder balls were found to be particularly effective in that the dendrites penetrate the solder ball surface oxides, for reliable electrical connections, and become imbedded into the relatively softer solder sufficiently to produce a mechanical bond and seal between the dendrite covered via or pad and the solder ball. The related concepts are described in U.S. Pat. No. 5,137,461 and IBM Technical Disclosure Bulletin Volume 36, No. 7, July 1993, pages 137 and 138, the subject matter of both references being incorporated herein by reference.

Though the use of dendrites, and the connection of a solder ball grid array devices to dendrite plated vias or pads has been known, attempts to apply the concept have proven less than successful. When attempts were made to connect a ball grid array module, nominally having 0.75 millimeter balls with a spacing of 1.25 millimeters, or a flip chip die, nominally having 0.125 balls with a spacing of 0.25 millimeters, array alignment and reliable connection between the array of solder balls and an array of solder covered lands on a printed circuit board using a dendritic interposer proved to be a significant challenge.

Therefore, there arose a need for a ball grid array device socket which allowed for a temporary but reliable connection between the solder balls of a ball grid device and a corresponding pattern of lands on a circuit board while allowing removal or replacement of the module or die as needed.

SUMMARY OF THE INVENTION

The present invention relates to an electronic device socket, comprising a planar interposer of flexible dielectric material having a multiplicity of vias or pads covered with dendrites, which vias or pads are distributed in a pattern substantially conforming to an electronic ball grid array device, a rigid cap with a planar surface alignable to be substantially coplanar with the surface of the ball grid array device, means for aligning a pattern of balls on a surface of the ball grid array device with the planar interposer and with a pattern contact regions on a board, and means for translating the rigid cap to compress the ball grid array device, the interposer, and the contact regions of the board adequately to cause dendrite penetration into the ball grid array device balls and the contact regions on the board.

In a particularized form of the invention, the ball grid array socket comprises a rigid planar stiffener, with alignment pins for extending through a printed circuit board, a planar interposer having a multiplicity of dendrite coated vias or pads alignable by holes to the pins of the stiffener, an alignment planar having holes for alignment with the pins of the stiffener and with select balls of a ball grid array device, a rigid planar heatsink capable cap, and an arch connectable to the alignment pins of the stiffener. A screw in the arch applies a force to the cap to compress connect the balls of the ball grid array device to the top side of the interposer and the bottom side of the interposer to solder deposits on lands of the printed circuit board. In another form, the flexible interposer is itself composed of multiple layers with electrical routing to pro