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June 4, 2006

Several questions including specifications for hole ratio and humidity control

A few questions.

1. What is the ratio of lead to hole diameter as per standard? Which clause of the standard is applicable?

2. What is the standard temperature and humidity in electronic assembly storage and assembly area? How best to maintain it? What are the tolerance limits?  Which clause of standard is applicable?

3. We can not use wrist strap where voltage is more than 80 VAC why? What are the technical reasons behind it?

4. What are the precautions are to be taken while applying peelable mask.

Thanks for your expert advice.



Veerendra Kumar Singh

Experts Comments

I'll take the first one.
Reference DOD-STD-2000, Volume 2A, 5.1.1.2.1 - 5.1.1.2.4
Round leads
Maximum clearance, 0.028"/0.7mm
Minimum clearance, 0.010"/0.25mm
(of the maximum Lead Diameter)

Rectangular lead
Maximum clearance, 0.028"/0.7mm
Minimum clearance, 0.006"/0.15mm
(of the maximum diagonal/cross section of the lead)

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Mel Parrish
FSO/Director Training Resources
STI Electronics Inc.
Mel Parrish is the FSO and Director of Training Materials Operations, Soldering Technology International (STI), in Madison Alabama. Before coming to the STI, Mel was the Training Manager for the Electronic Manufacturing Productivity Facility (EMPF) and President of Manufacturing Technology Training Center Inc. (MTTC) in Ridgecrest, CA. He remains active in industry trade associations and organizations such as IPC, SMTA, and SME.
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