Solder paste

Details Solder paste Solder paste

1994-09-21

1997-10-07

Andrews, Melvyn

Metal treatment

Compositions

Fluxing

428403, B23K 3534

Patent

active

056743262

ABSTRACT:
Solder pastes presently harden or congeal over time. This results in wasted solder paste and in production down time. This hardening is a result of the long polymer chains created by the dicarboxylic acid in the activator and the indium (In) or tin (Sn). A solder paste is described in which the metal alloy is coated by an agent that inhibits the reaction with the dicarboxylic acid. One solution involves coating the metal alloy powder with monocarboxylic acids, which truncate the polymer chain. Another manner for truncating the polymer is to coat the metal alloy powder with complexing agents. The metal alloy powder can also be coated by a stable metal such as lead (Pb), gold (Au), silver (Ag), bismuth (Bi), palladium (pd), platinum (Pt), a silver palladium alloy (AgPd) or a silver platinum alloy (AgPt).

REFERENCES:
patent: 2923649 (1960-02-01), Todd
patent: 4298407 (1981-11-01), Taylor
patent: 4994326 (1991-02-01), Shimmura et al.
patent: 5086966 (1992-02-01), Melton et al.
patent: 5177134 (1993-01-01), Mullen, III et al.
patent: 5328521 (1994-07-01), Keusseyan
patent: 5328522 (1994-07-01), Sowa et al.
patent: 5334260 (1994-08-01), Stetanowski
Dr. M. Warwick et al., "Solder Paste Design Considerations", Circuits Assembly magazine, Aug. 1994, pp. 36-42.

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