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May 2009

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Subject:
From:
Robert Kondner <[log in to unmask]>
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Date:
Thu, 14 May 2009 16:57:56 -0400
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Richard,

 Your wrote:
 "Non-ESD polyethylene bags are notorious ESD generators. I wouldn't want
them in my factory."


  You will NEVER get a ESD event from polyethylene because it is an
insulator, right?

  However I see lots of ESD events with grounded metal objects. Since UL
requires metal machines to be grounded I guess you don't want any metal
machines in your factory?

 What is going on here?

Bob Kondner





-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Stadem, Richard D.
Sent: Thursday, May 14, 2009 3:12 PM
To: [log in to unmask]
Subject: Re: [TN] Bare PCB Packaging Requirements

1. The same moisture barrier bags that are ESD-safe Faraday bags also
work well as moisture barrier bags for shipping and storing PWBs. These
Faraday bags often work well for storage of the CCA during assembly. Why
use two different types of bags if one fits the bill? Non-ESD
polyethylene bags are notorious ESD generators. I wouldn't want them in
my factory.

2. Many CEMs and OEMs have requirements for the PWBs to be shipped in
MBBs, in order to prevent against surface finish oxidation in the case
of IAg, ISn, HASL and FTL finishes. Some invoke a requirement such as
IPC 4552 or 4553 in order to ensure the boards are dry and hermetically
sealed.

3. All PWBs absorb moisture from the air. Having the boards sealed
prevents excess moisture ingress, in some cases if the boards are
shipped in sealed bags with desiccant, the user may not need to pre-bake
if they are able to successfully perform Kanban pull from the fabricator
within a short time frame. This, of course, requires qualification and
validation of the process and procedures.

So, if a bag is required, use one from start to finish that meets
multiple requirements.

I assume you understand why moisture within the PWB is not a desirable
condition.


-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of John Parsons
Sent: Thursday, May 14, 2009 1:37 PM
To: [log in to unmask]
Subject: [TN] Bare PCB Packaging Requirements

Tell us, how many CEM's out there are demanding that bare PCB's be
received
in vacuum sealed moisture barrier anti-static bags.  If so, what is your
reasoning?  Just to be clear my focus here is "anti-static" not the
moisture
barrier properties of the packaging.

 

Regards

 

John Parsons

 


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