Hello Toni,

You appear to have a bad case of outgassing. This is coming from voids in
the copper plating through the holes. This can be due to thin plating or
poor hole drilling, or usually both.

If you can get micro sections of the holes, check plating thickness is more
than 20 microns and that the drilling is are not unduly rough.

A long low temperature bake is better than a short high temperature one. Say
about 100 C for 2 hours should be sufficient but if the pcb's are really
bad, it may take longer.

Ask your supplier to submit a spare pcb with each batch in future so that
you can conduct solderability tests before assembly. You will then be able
to reject the batch if quality is not acceptable.

Good quality pcb's should not require baking but some assembly shops do this
as a precaution, especially after long periods of storage in damp
conditions.

Hope this helps,

Regards
Paul Gould
Teknacron Circuits Ltd
UK
+44 1983 866531 Tel
+44 1983 865141 Fax

-----Original Message-----
From: [log in to unmask] <[log in to unmask]>
To: [log in to unmask] <[log in to unmask]>
Date: 13 June 1998 11:44
Subject: [TN] Outgassing problem in pcb's soldering


>Dear Sir /Mme:
>
>My name is Toni Casas and I'm working as a quality engineer in an
entreprise
>which performs electronic circuits and devices for industrial aplications.
>
>I have heard about your organization and I'm sending you this e-mail in
>order to ask some things about soldering processes. I explain a little
about
>our productive process.
>
>First of all we perform SMD assembly. Then we mount conventional components
>by hand and then the pcb's are soldered in a new technology soldering line.
>
>We have problems, especially in large pcb's, by the humidity of the pcb amb
>the problem known by the name of outgassing. You know, we enter the pcb
into
>the soldering line and when the tin reaches any pad of the pcb, then it
>explodes by the presence of humidity. Our pcb's supplier says that is the
>outgassing problem, but we know nothing about that: Nothing about
>outgassing, and nothing about how to use pcb's properly to get a good
solder.
>
>If you have any information about that, I please ask you to send it at the
>address
>
>[log in to unmask]
>
>which is my personal address.
>
>Toni Casas Pujadas
>Quality Enginner

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