A wide process window is essential. I beleive that design for
manufacturability is the key to generating a wide process window. The PCB
finish will help marginally but ultimately it's down to good design
processes. At the design / layout stage of an assembly it's important to
consider the process flow for the assembly and that means taking the
capabilities of the materials and equipment into account, when designing the
pad geometries, clearances, component positions etc..
You need to know what materials/machines are going to be used, if many and
varied you still need to know what they are.
If you don't design manufacturability for a given process set up at the
outset then you can forget it you will never have a wide process window.

Regards

At 05:30 14/05/98 -0500, you wrote:
>Hi TechNet!
>
>In a former life, I met the late Jim Bryan and was treated to several
>lectures on "What a 'process' is".  He also wrote a series of articles on
>this subject for PC Fab which I no longer have (sometimes you just have to
>clean house).
>
>Does anyone still have a copy of these articles they could fax to me?
>Please reply offline.  Also, I WILL contact PC Fab myself.
>
>Also, I would like to have the TechNet's opinion of what a 'process' is to
>them.  I am about to enter into this discussion with a bunch of assembly
>folks (I'm just a board guy, you know) who think I ought to be able to spec
>in the boards so they can go through all of their 'processes' no matter how
>they control them, several sites, one material.
>
>As I recall, (and, trust me, I used to be able to recite this in my sleep)
>Jim said that the process window had to be large enough so that a variety
>of materials can run through without a change in process parameters, and
>all of these materials will acquire the desired characteristics of the
>outcome of the process.  In other words, you shouldn't have to change your
>process every time something different comes along and you should be able
>to run a lot of different materials through your process.  A robust process
>has a window you could drive a truck through.
>
>Anyone care to continue this discussion?  My apologies to those who don't
>like this sort of thing on TechNet.
>
>Regards,
>
>Dave Sullivan
>Rockwell Collins
>
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