July 23, 2007

Sounds like the same problem an OEM of ours experienced some years ago.  The 
OEM had a grease like residue deposited on PWAs that were shipped in the 
pink ESD bags.  We traced the problem to what is known by the name "beef 
fat"; don't recall what the exact chemical name is.

We now only allow the Type 1 bags per MIL-PRF-81705.  These are aluminum 
colored on the outside and black colored on the inside.  We have not had any 
recent problems with this type bag leaving any noticeable residue on 
product.


>From: Kevin Glidden <[log in to unmask]>
>Reply-To: TechNet E-Mail Forum <[log in to unmask]>,              Kevin 
>Glidden <[log in to unmask]>
>To: [log in to unmask]
>Subject: [TN] Anti-Static Bags
>Date: Mon, 23 Jul 2007 16:38:45 -0400
>
>Hello 'Netters...
>
>Question: Does anyone have experience or recomendations in controlling the
>supply chain of the pink poly anti-static bags?  We currently purchase them
>per MIL-PRF-81705 Ty II.  But, it has come to our attention (via Customer
>Returns and Corrective Action) that some of the bags we were getting were
>leaving a sticky residue on the parts.  Investigation has led to the
>discovery that the anti-static properties of the bags can be attained via
>one of two major ways: 1) an anti-static topical coating or 2) anti-static
>"materials" (carbon?) impregnated into the bag itself.  Apparently the
>MIL-spec only specifies the finished properties, not the process.  I have
>been told the coating is a cheaper method than the impregnated.  I would
>like to prevent purchase of the topically coated bags, and only purchase 
>the
>impregnated versions, but how to specify it? I have found several vendors
>and / or manufacturers who claim their bags are impregnated.  But I am
>reluctant to to tie my Purchasing groups hand by limiting such a commodity
>item (there are apparently a thousand manufacturers and a million more
>distributors) to a few vendors.  I am also uncertain that most (if any)
>distributors would a) see my requirement for the impregnated version, and 
>if
>they did b) even know what type they sell.  In lieu of the above issues, it
>has been proposed we implement more stringent incoming inspection to
>visually inspect for oily residues.  While this works, it would also let 
>the
>supplier off the hook, so to speak, if we found bad bags that were still
>compliant to the purchase spec (MIL).
>
>Has anyone faced this same problem?  Any recommended vendors?  Control
>Plans?
>
>Thanks!
>Kevin Glidden
>Manufacturing Engineer
>Luminescent Systems Inc.
>
>
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