Vernon - The only place where I have seen sulfur contamination on components
was from packing material; cardboard boxes to be specific. We were trying to
pretin Leadless Ceramic Chip Carriers that had gold castellations, and we
couldn't get the solder to wet to the gold. As you probably know, if you
can't get solder to wet to Gold, you have a problem. As for the Silver
depletion, are you are using Palladium-Silver terminations on the resistors,
and are you using Sn62 solder?

Ed Valentine
Electronics Manufacturing Solutions
8612 Mourning Dove Road, Raleigh, NC 27615
Phone: (919) 270-5145, Fax: (919) 847-9971
Email: [log in to unmask]
Website: http://www.ems-consulting.com

----- Original Message -----
From: Vernon Richard <[log in to unmask]>
To: <[log in to unmask]>
Sent: Wednesday, June 14, 2000 7:12 PM
Subject: [TN] Resistor termination disappearing


> Hello, TechNet!
>
> We're working a problem with a resistor where the value increases due to
> some chemical reaction. The reaction takes place between the termination
> silver and sulfur present on the component. This causes the resistor to
> change value due to the silver being depleted from the connection
interface.
> We don't introduce any sulfur in our processes (std smt w/ aqueous wash,
Dow
> 1753 coated), so we suspect that it comes from the resistor manufacturing
> process. We also seem to have a gap in the glassivation over the interface
> area.
>
> Has anyone seen this before? What was done to eliminate the problem? Help-
> our customer is getting very concerned!
>
> Thanks. Rick Vernon
>
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