Precleaning of soldered circuit cards to prevent white residue

Details Precleaning of soldered circuit cards to prevent white residue Precleaning of soldered circuit cards to prevent white residue

1993-02-16

1994-05-17

Ramsey, Kenneth J.

Metal fusion bonding

Process

With subsequent treating other than heating of bonded parts...

228202, H05K 334

Patent

active

053120272

ABSTRACT:
Following soldering of electrical components on a circuit card in a soldering process that includes use of an aqueous-based flux, the circuit card, containing the soldered electrical components, is exposed to a dilute aqueous basic solution prior to a final hot water rinse. The dilute basic solution prevents the formation of a white residue commonly associated with the use of aqueous-based fluxes. For example, using a flux consisting essentially of an aqueous solution of citric acid, and rinsing in either an aqueous ammonia solution consisting essentially of about 20 to 250 ppm ammonium hydroxide or an aqueous solution of about 0.1 to 3 wt% sodium bicarbonate, prevents formation of the white residue.

REFERENCES:
patent: 3482755 (1969-12-01), Raciti
patent: 3588998 (1971-06-01), Corsaro
patent: 3604104 (1971-09-01), Glasgow
patent: 3896828 (1975-07-01), Foster et al.
patent: 3997459 (1976-12-01), Bogie et al.
patent: 4441938 (1984-04-01), Poliak et al.
patent: 5141568 (1992-08-01), Turner et al.

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