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February 1998

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From:
Peter Swanson <[log in to unmask]>
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Date:
Tue, 17 Feb 1998 09:08:47 GMT
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In message  <[log in to unmask]> [log in to unmask] writes:
> In an effort to reduce soldershorts at SOICs from occuring during our wave-
> soldering process, we apply what we call "pre-wave mask", pretty typical
> process, I believe.  (The SOICs are previously paste-reflowed.)  However, we
> have experienced damage to the leads of the SOICs when we peel the pre-wave
> mask off from the wave-soldered boards.  In order to prevent this from
> occuring, we are contemplating not peeling this mask away and just leaving it
> on for the life of the product.  The big question:
>
> Is there any long-term reliability issues here?  Could the mask being a future
> failure location due to contamination growth or some other reason?

You do not mention the chemistry type of the mask which you use - there are
several, including latex (both natural and synthetic), pvc and urethanes. Some
have been known to contribute to poor SIR test results, although my belief is
that this is only the latex types. Ask if the mask supports fungal growth.
Around the edges of the mask is an area where flux entrapment can occur - would
these residues be benign in your case?

I think what you want to do could work, with the correct choice of mask.
Peter
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Peter Swanson                                              Oxfordshire, England
INTERTRONICS
[log in to unmask]                      http://www.cygnetuk.demon.co.uk

Suppliers of materials and consumables to the electronics & related industries
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