I disagree with this philosophy, or at least have a
general problem understanding this philosophy.

The IPC has been telling us for years that it would
be better for our industry to develop generic
specifications that all vendors should be able to
meet as a bisic minimum, and that designers can
refer to these basic guidelines instead of having
to come up with vendor-specific solutions.
That's the reason so many companies participate
in their existence, so we can all benefit from the
result.

Why should every customer use precious time, money
and resources to "develop a matrix", unless there is
some "outside the normal realm of board manufacture"
reason for doing so?

feeling lazy today,
Jack


----- Message from Jeffrey Bush <[log in to unmask]> on Thu, 29
Jul 2004 10:06:26 -0400 -----

                Subject: Re: LPI soldermasks


In fact this was the 1 issues that I can see.  I will recommend using the
IPC-SM-840 to cover the thickness requirement. This is based on the
materials ability to withstand 500 VDC without leakage.  As far as the mask
finish - LPI material come in so many flavors that I think it is important
to develop a matrix of acceptable LPI types in your PCB specification.
This will allow for good control of specific LPI part numbers from
suppliers that meet you needs for flux types, conformal coating
compatibility, etc.  Letter screen inks should also be a part of this
requirement.  The most effective method would be to solicit this
information from your suppliers as these will be the ones that are
currently working for you.  Any new suppliers/materials could undergo a
controlled testing program to ensure compatibility with your process.



Jeffrey Bush
Director, Quality Assurance and Technical Support

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