Doug Pauls wrote:
>
> In a message dated 97-11-28 04:25:16 EST, you write:
>
> >                I have a white resiude problem after aqueous assembley,
> >  i know the solder resist manufacturer has changed his formulation, but I
> >  would like to work with the solder resist manufacturer as the resist has
> >  numerous advantages.
>
> This problem can be caused when assemblers use aqueous cleaning systems outside the recommended limits, especially temperature. This applies when the solder resist is
acrylic/epoxy based, it can absorb moisture in hot alkaline conditions. Often the
cleaner contains an organic alkali placing it between a resist developer and a resist
stripper which accelerates the problem. It is advisable not to allow the temperature to
go above 40 deg. Celcius. This effect is also seen when solder resisted boards have been
electroless nickel gold plated and not dried properly.
        The white disclouration may be removed by giving the board a thermal excursion
above 100 deg celsius.

Roger Hammond

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