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Subject:	Re: Nonwetting
From:	Brian Ellis <[log in to unmask]>
Reply To:	TechNet E-Mail Forum.
Date:	Sat, 14 Oct 2000 11:19:15 +0300
Content-Type:	text/plain
Parts/Attachments:	text/plain (47 lines)

Jim

I have seen this quite often with immersion gold on copper and on nickel
over copper. The gold is so thin and porous, and copper can migrate
through the gold at a phenomenal rate, that it offers little practical
protection. Also, if the gold bath is poorly maintained, too much
organics may be co-deposited with the gold.

If it is just the odd pad, then retouching (which I don't like) may be
done on extreme cases. Better may be to use a more active flux in the
paste. If the problem is due to oxidation or migration, this may do the
trick. If it is due to organics, maybe not.

FWIW

Brian

"West, Jim" wrote:
>
> Hi everyone,
>
> I have a situation where the solder is adhering to the component and 3/4 of
> the pad out from the component.  The pads have immersion gold on them.  Can
> I classify this as nonwetting?  The component ends appear to have a properly
> wetted fillet.  This is the first time I have used immersion gold on pads
> and I'm wondering if this is normal, or if this is causing the problem.
> Also, would touching up the pads with an iron to finish the flow cause any
> problems?  Thanks in advance for your input!
>
> Jim
>
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