>Solder mask is a recent, however many years,
> a standard.  It has creeped at a high pace
>as evidenced by many people calling for both
>sides being masked.  In my opinion there are
>way too many times mask is called for which is
>NOT needed.  Pricing of boards has included masks
>which could add over $1.50/board plus extra tooling.
>You probably will have a hard time getting a quote
>on a board which does not call for mask.
>In other words, I will agree with anyone who says that
>"I DO NOT THINK MASK IS WARRATED".
>

My company manufactures many types of board but there is one volume 6-layer
multi-layer which is reflowed with no solder mask for press fit application.
This particular panel has virtually no track on the surface being pads only
and all the tracking is on internal layers.

I think the main problem with any board which requires a solder mask for
assembly wave solder is that it needs to be hot air levelled to avoid
tin-lead under the solder resist. This increases the cost again due to
tin-lead strip, and hot air level processes. Reflow is the cheapest but alas
seems to be declining and fewer companies seem able to offer it preferring
to standardise on HASL.

Reflow should be considered for surface mount work if they are infra red
fused without wave solder. I have evaluated thinner tin-lead deposits
reflowed and it is very successful on fine line work. Solder mask over
tin-lead would not be a problem then if required for environmental
protection.

One benefit of solder mask is it improves the surface insulation resistance
and is less attractive to contaminants. It's up to the customer at the end
of the day but I agree it is more expensive and not always necessary.

Best
Paul Gould
Teknacon Circuits Ltd

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