Metal treatment – Compositions – Fluxing
Patent
1997-01-17
1999-05-18
Simmons, David A.
Metal treatment
Compositions
Fluxing
148 24, 148 25, B23K35/34
Patent
active
059047828
ABSTRACT:
A resin-based VOC-free soldering flux consists of 40 to 50 wt % of a liquid epoxy resin, 25 to 30 wt % of a non-volatile liquid epoxy diluent, 20 to 33 wt % of a polyfunctional carboxylic acid, and 2.0 to 3.5 wt % of a thixotropic agent. There are no volatile organic solvents or compounds in the flux which can evaporate during the reflow process. The carboxylic acids are provided in powdered form and are suspended in the epoxy blend wherein they remain as solid particles until heated in the solder reflow process. A VOC-free solder paste formed from the flux consists of 40 to 95 wt % soldering particles, and 5 to 60 wt % of the VOC-free soldering flux. The thixotropic agent improves printability of the solder paste onto printed wiring boards. A VOC-free flux-core solder wire includes the VOC-free flux as the inner core of the wire with an outer shell of solder alloy. The VOC-free, epoxy resin based flux effectively activates the solder powder and the copper contact during the reflow process, while at the same time hardens to leave a solid, dry, yet flexible residue on a printed wiring board. No organic compounds are emitted during the reflow process.
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Fry Metals, Inc.
Koehler Robert R.
Simmons David A.
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