Fine pitch solder formation on printed circuit board process and

Details Fine pitch solder formation on printed circuit board process and Fine pitch solder formation on printed circuit board process and

1994-09-30

1996-02-20

Thomas, Laura

Electricity: conductors and insulators

Conduits, cables or conductors

Preformed panel circuit arrangement

174260, 174250, 361760, 361767, 22818022, H05K 118

Patent

active

054930758

ABSTRACT:
A method, and product created thereby, by which low melting point solder suitable for reflow connection of components is formed on select fine pitch contacts of a printed circuit board. The method is particularly suited to the attachment of flip-chip die to printed circuit boards which also include coarse pitch surface mount components. Controlled volumes of solder are formed onto fine pitch contacts of the printed circuit board through selective holes in a mask formed onto the board. The deposit is accomplished by molten solder immersion preferably using conventional hot air solder level manufacturing equipment. The volume of solder is related to the thickness of the mask. The mask is then removed, the deposited low temperature solder is flattened, and the coarse pitch contacts are covered with solder paste in a conventional screening process. Flux is applied to the fine pitch contacts. After component placement, the solder reflow connects in one operation both the fine and coarse pitch components to their respective printed circuit board contacts.

REFERENCES:
patent: 4722470 (1988-02-01), Johary
patent: 5060844 (1991-10-01), Behun et al.
patent: 5147084 (1992-09-01), Behun et al.
IBM TDB, vol. 37, No. 02B, Feb. 1994, "Improvements in the Sacrificial Substrate Burn-In Methodology for Known Good Die", pp. 19-20.
IBM TDB, vol. 30, No. 7, Dec. 1987, "Fine Pitch Printing for Surface Mounted Technology", pp. 314-315.
Research Disclosure, Nov. 1988, No. 295, "Solder Mask Elimination on Printed Circuit Boards".
Research Disclosure, Feb. 1992, No. 334, "Ladder Pattern for Soldering Circuit Board Ground Pads".
Sandia National Laboratories, DE93 009631, "A Maskless Flip-Chip Solder Bumping Technique", Chu et al.
Circuits Assembly, Feb. 1993, "A Step in the Right Direction", Payne et al, pp. 59-64.

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