For a wrist strap, the fail low at 750 kilohms is just checking for the 1
megohm current limiting resistor. Similarly for footwear verifying that
amount of resistance which can be just the rubber, etc.
Basically for the wrist strap, the only failure mode is a blown short
resistor. Some footwear have current limiting resistors, but since you have
changed the footwear many times, I'll have to think about it and ask my
co-workers.
Compliance Verification ESD TR53 (the required test method per ANSI/ESD
S20.20-2007) has troubleshooting sections. I'll see if it offers any help.
Gene Felder
[log in to unmask]
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of John Anselmo
Sent: Wednesday, May 20, 2009 12:31 PM
To: [log in to unmask]
Subject: Re: [TN] ESD Heel Strap / Shoe Checker - low resistance
Does he put the end of the strap inside the shoe (between his shoe and his
sock) or on the inside of his sock against his skin?
-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Helena Pasquito
(Cobham DES SSA)
Sent: Wednesday, May 20, 2009 12:53 PM
To: [log in to unmask]
Subject: [TN] ESD Heel Strap / Shoe Checker - low resistance
Hello Tech Net,
Assemblers and techs check their shoes on an ESD Shoe checker, each day
before the start of their shift. We have one person that works in the
warehouse that always fails low (resistance). We have tried new heel straps,
walking for an hour or two in regular ESD shoes, even wearing someone elses
shoes that had just passed. Nothing seems to work. He has also tried to
apply lotion to the strap that sits inside his sock. Do you know of any
tricks we can try to employ? Have you seen issues like this before? I think
some of the steps we took may have helped for a high resist fail but not a
low resist. Even the wrist strap test fails for him (multiple wrist straps).
Any suggestions would be much appreciated.
Helena Pasquito
Training Specialist
Certified IPC Trainer
Cobham Electronic Systems
1001 Pawtucket Blvd., M/S 160
Lowell, MA 01853
978-442-5024
[log in to unmask]
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