Component rework

Details Component rework Component rework

1993-08-20

1994-12-06

Picard, Leo P.

Electricity: conductors and insulators

Conduits, cables or conductors

Preformed panel circuit arrangement

22818022, 174258, 361768, 361767, H01K 116

Patent

active

053713281

ABSTRACT:
An easily reworkable circuit module is provided that allows unusable electronic components that have been encapsulated to be removed from a printed circuit board. A chip or MCM attached to a carrier using direct chip attach methods (DCA), such as C4 or SBC techniques that leave a space between the chip/MCM and carrier, due to the height of the solder balls, connection pads and the like. The present invention places a non-stick release coating on all surfaces intermediate of the chip and carrier. That is, the release coating of the present invention is placed by spraying, or the like between the chip and carrier to form a thin liquid film which inhibits the adhesion of a subsequently applied and cured rigid polymer encapsulant. Thus, when a chip or MCM tests as "bad", rework is a relatively simple matter. The solder connections between the chip and carrier of the module are reflowed and the chip is lifted off. The solder reflow temperature will be below the melting point of the encapsulant, and since the encapsulant did not stick to the chip or carrier, it can be merely wiped away with a dry cloth.

REFERENCES:
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patent: 3707039 (1972-12-01), Neimirovich
patent: 3719981 (1973-03-01), Steitz
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patent: 5121190 (1992-06-01), Hsiao et al.
patent: 5147084 (1992-09-01), Behun et al.
patent: 5329423 (1994-07-01), Scholz
IBM TDB, "Semiconductor DIE Encapsulant with Intrinsic Release Layer", vol. 34, No. 2, Jul. 1991, pp. 181-182.

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