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From [log in to unmask] Wed Dec 18 10: |
48:17 1996 |
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YOU WILL NOT GET A "FARADAY" SHIELD EFFECT WITH 10*11 OHMS..
ASSUMING THE ISSUE IS DUE TO AN ELECTROSTATIC FIELD, "AN ELECTROSTATIC
SHIELD MATERIAL SHALL HAVE A CONDUCTIVE LAYER WITH A SURFACE
RESISTIVITY OF LESS THAN 1.0 X 10 * 4 OHMS/SQ."
REF. EIA - 541 "PACKAGING MATERIAL STANDARDS FOR ESD SENSITIVE ITEMS"
______________________________ Reply Separator _________________________________
Subject: ESD packaging: antistatic polythene or metallised bags?
Author: [log in to unmask] at smtp
Date: 12/18/96 10:17 AM
I am in something of a dispute with one of our suppliers, a large Japanese
manufacturer, of high value ESD sensitive assemblies. They supply the
assembly in blue antistatic polythene bags (see below) with no secondary
protection. I insist that they package in metallised ESD protective bags,
but with a negative response so far as they believe their packaging is adequate.
This is not an innocent issue as we have suffered several failures which
this manufacturer ascribes to ESD damage. Being confident in our own
precautions I believe the delivery packaging could be the principal cause.
Their QA department's response is as follows:
"I collected the physical properties of anti-static polyethylene
packaging for TFT and C-STN as follows.
Items Standard
Sort APTSTAT-Blue 50 micron m
Material (main resin) MITSUBISHI-Polyrthy LD F250
(sub resin) Anti-static resin
Surface resistivity 10**9 to 10**12 Ohm
We use this ESD packaging for not only all TFT products but also
all C-STN products.
By the way, surface resistivity of a metallised bag giving a Faraday
cage effect is about 10**11 Ohm.
Therefore, we think this is not problem.
Thank you and Best Regards
QA department, Japan"
Can anyone give me an authorative reference that I can use to decide this
argument one way or the other please.
Merry Christmas
John Loveluck
Quality Manager
Tadpole Technology plc
[log in to unmask]
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