Printed Circuit Board Assembly & PCB Design SMT Electronics Assembly Manufacturing Forum

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solder joint appearance



solder joint appearance | 27 July, 2004

Hi Recently i have noticed that after reflow (hot air oven) on the solder lands without components but with solder(screen printing) there is discoloration. It looks like gasolin spilled on the wet road (rainbow). Any idea and reason


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Steve Stach


solder joint appearance | 28 July, 2004

Hi Ralf,

This discoloration may be re-oxidation. Fluxes are supposed to do three things (1) remove oxide, (2) promote wetting, and (3) protect surface from reoxidation. The solder paste possibly is not protecting from reoxidation. Best Regards, Steve Stach Austin American Technology

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solder joint appearance | 29 July, 2004

Could be lots of things. With limited information about temperatures, solder alloy, and cleaning; we'll swing for the fence that you got these solder connections very hot. So hot that Pb oxide is dominating the solder joint surface instead of the usual Sn oxide.

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