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December 2005

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Subject:
From:
"Linda.Li" <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Linda.Li
Date:
Fri, 2 Dec 2005 16:15:04 +0800
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Hello all,

We have a design using ENIG plus ENEG surface finishing on circuit boards, ENIG is used for Al wire bonding, ENEG is used for Au wire bonding.  We met 2 problems about this design.

1) We found solder mask peeling problem after aging the assembled circuit boards at 150 degree C for 2 hours.  We contact the circuit board supplier and were told that because of 2 times UV exposure( 1 time is in solder mask exposure, the other is in ENIG process), the solder mask was apt to peel off.  So far the supplier doesn't have any good method to solve this problem.   Do you have any suggestions to solve this problem?  Thanks.
2) During ENIG process, the gold is seeped onto the surface of copper pad that needs to be electrolytic gold plated.   It's because of air bubble entrapped during dry film lamination.  The supplier has changed the lamination speed, processed the panels in different direction, but still can't solve the problem.   I am in urgent need of your expert advice .

The circuit board fabrication process flow is as follows:  >> solder mask printing>>dry film lamination>> UV exposure>>dry film development>>Electroless Nickel Immersion gold plating>>strip dry film resist>>Electrolytic nickel and gold plating>>

Thanks for your help in advance!

Best regards,

Linda Li





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