Hi Doug, 

One "process aid" that can be a source of contamination in PCB shops is the slip sheets used to separate inner layers during transport between process stages. Board shops should clean these regularly (frequency depends on many factors, but should probably be once/lot at minimum).

The draft is coming along nicely. One item I would add to the soldermask section is the pre-clean operation, prior to soldermask deposition. It is critical to use DI water in this operation, not tap water (<-- this is a more common practice than you would think). Tap water quality - particularly in Asia - is highly variable and can contain elevated levels of Cl and other ionics that are then trapped under the soldermask and can cause corrosion and could affect adhesion and cure. 

Todd MacFadden


-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Douglas Pauls
Sent: Thursday, May 10, 2012 12:40 PM
To: [log in to unmask]
Subject: Re: [TN] IPC-5703 Question 3

Graham,
I think you are referring to assembly tooling.  I have considered things 
like transport racks, fixtures, etc.  for the fab process.

Doug Pauls



From:   [log in to unmask]
To:     "TechNet E-Mail Forum" <[log in to unmask]>, 
<[log in to unmask]>
Date:   05/10/2012 11:37 AM
Subject:        RE: [TN] IPC-5703 Question 3



Hi Doug
How about contamination transferred to the assembly from tooling - e.g.
wave pallets, holding fixtures, alignment jigs...

regards,
 - Graham
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Douglas Pauls
Sent: Thursday, May 10, 2012 1:23 PM
To: [log in to unmask]
Subject: [TN] IPC-5703 Question 3

Perhaps I should have prefaced Question 1 with INCOMING!!!!!!

A commenter has indicated that we should have a section discussing
possible contamination or process residues that come from "Processing
Aids" in board fabrication operations.  We already discuss items like
sharpees, grease pencils, tapes, stickers, etc.

What other "process aids" should be included in a primer on board
cleanliness for fabricators and why?

One of the commenters for this was Dewey, and the IPC Dewey filter
automatically routes those to a black hole.......

Doug Pauls


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