Can anyone shed any light on the cause and cure of the following problem?
Some test panels with edge connectors were gold plated on a tab plater:-

        Electropolish - phosphoric acid
        rinse
        activate - 10% sulphuric acid
        rinse
        gold plate - nickel hardener
        rinse
        dry

These boards were then passed through a conveyorized solder resist curing oven.

The area  exposed to the tab plater solution turned a red/ purple colour.

Other boards also tab plated were washed in a post hasl cleaner, passed through a 3%
caustic soda coveyorized resist stripper and finally passed through a brushing machine.

When passed through the the resist curing oven the area exposed to the tab plater
solutions turned red/purple.

When I tested the insulation resistance between the edge connector fingers on the
stained boards at 1000 volts it was 145 gigohms.

Some of the stain can be removed with acetone but not other solvents.

Thankyou in advance

Roger Hammond

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