Many years ago all boards were made this way.  That was before surface
mount/mass reflow.  For either hand solder or wave solder this didn't
present a cosmetic problem because any solder deposits which got heated
to reflow temperatures were fluxed beforehand.

It is natural for the solder to oxidize heavily (tarnish) when heated
above reflow with no flux applied.  This oxidation would make a weak
solder joint, but it is still an OK surface coating.

Wayne Thayer   

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Kong Hui Poh
Sent: Friday, November 30, 2007 12:25 AM
To: [log in to unmask]
Subject: Re: [TN] Tin/Lead plating board, turned tarnish

Hi Technetters,

I am facing a problem with a tin/lead plating board.

I am facing a problem with boards that are of Roger material and was
tin/lead plated.

The traces are not being masked, hence exposed.

We subject the boards to reflow, and those area where no solder joint
turned tarnish.

This is the first time we handle such kind of board. We have no
experience on this.

I wander if tarnish is a defect. Can someone advise me how to remove
this tarnish  as I try using IPA to rub it off, it seems nothing
happened.
I could not find this in the IPC.

Please advise me.

Thanks.

KH Poh

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