Metal fusion bonding – Process – Plural diverse bonding
Patent
1995-05-30
1996-07-16
Ramsey, Kenneth J.
Metal fusion bonding
Process
Plural diverse bonding
22818021, 22818022, 427282, H01L 2158
Patent
active
055359361
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.
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Chong Ku H.
Crockett, Jr. Charles H.
Partridge Julian P.
Sanghavi Bhavyen S.
International Business Machines - Corporation
Ramsey Kenneth J.
Salys Casimer K.
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