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March 1997

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Subject:
From:
Mohd Misri-RSB019 <[log in to unmask]>
Date:
Thu, 6 Mar 1997 11:31:00 +0800
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We are doing surface mount semiconductor assembly. 
After solder plating process the products goes to Trimming/Forming followed by 
Final Electrical testing.

One of the problem we face is 'Contact' problem.
The product leads are connected  to electrical circuits (we call it Test blade) 
for the test. Once each product unit complete the test it will move to next 
process. Another product unit will be connected again and so on...This process 
take very short period of time. Few product units are tested in a second. 
Thousands of products are continousely ON and OFF going to this Test blade.

Sometime the test blade can last for few days before getting dirty. Then we can 
either clean or change it.

Sometime the test blade can only last for few hours! When we analyse this fast 
dirty test blade, we found black solder layer. It should be Tin/lead oxide build 
up.Some theory says, if the 'contact' between test blade and product leads are 
not good it can create a 'spark' and burn the solder very fast.

The question is, what is the factors that affect the test blade life or how to 
slow down the solder build up? Is it Tin/lead composition, humidity or 
temperature ?

regards
M_Misri 

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