| On various PCB's after building processes,such as reflow, flowsolder and wash. The soldermask on the PCB's have become discoloured, like a 'marble' effect all along the solder side of the board, it is lighter in contrast than normal, although when other added comps. are assembled and handsoldered afterwards the soldermask seems to return to its normal darker colour around the solder joints where the heat from the iron has been applied. There has been no prominant changes in our processes, not sure where to start trouble shooting or whether it is a PCB manufacturing issue involving problems with curing soldermask. | | Your help would be appreciated, thanks in advance. | | Jack |
Jack,
Does the discolor have a milky appearence underneath the solder mask? If use hot air or solder iron the color will return (white diappears).
By chance are you using a Kester 2331 zx water soluable flux? Do PCBs have a Taiyo brand soldermask? If so you may be having a chemical reaction with mask, flux, and wash.
Check the archives for "white layer appearance on soldermask"
Happy Hunting!
Tom B.
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