Method of forming a solder layer on pads of a circuit board and

Details Method of forming a solder layer on pads of a circuit board and Method of forming a solder layer on pads of a circuit board and

1990-11-26

1992-06-02

Rowan, Kurt

Metal fusion bonding

Process

Chemical reaction produces filler material in situ

2281802, 228224, 228248, 427259, B23K 0000

Patent

active

051180294

ABSTRACT:
A paste-like composition containing a lead salt of an organic acid and tin powder is applied on a pad array portion of a circuit board. Then, the paste-like compsition is heated so as to cause precipitation, thereby forming a solder layer formed of a Sn-Pb alloy substantially only on the pads. This precipitation is performed in a state that a liquid pool is formed on the pad array portion when the paste-like composition is liquefied by heating, and the tin powder is settled in the liquid pool. When an electronic part is mounted on the pads, first, preparatory solder layers are formed on the pads by the above-mentioned precipitation process. After a paste-like composition is applied on the preparatory solder layers, the electronic part is put on the paste-like composition. Then, the paste-like composition is heated, thereby soldering leads of the electronic part to the pads.

REFERENCES:
patent: 3978378 (1976-08-01), Tigner et al.
patent: 4132341 (1979-01-01), Bratschum
patent: 4293592 (1981-10-01), Morishita
patent: 4490283 (1984-12-01), Kleiner
patent: 4661173 (1987-04-01), Barajas
patent: 4728023 (1988-03-01), Barajas
patent: 4810672 (1989-03-01), Schwarzbauer
patent: 4851153 (1989-07-01), Kono et al.
patent: 4960236 (1990-10-01), Hedges
patent: 5021269 (1991-06-01), Kono et al.

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