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December 2005

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Subject:
From:
Eddie Rocha <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Eddie Rocha <[log in to unmask]>
Date:
Mon, 5 Dec 2005 09:07:41 -0700
Content-Type:
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text/plain (150 lines)
Actually I can't figure out how you plate electrolytic Ni
and Au after soldermask or why? Could you explain?
Thank you,
Eddie Rocha
South Bay Circuits


Hello Eddie,

Thanks for your good idea.

Can you explain how to process Electrolytic Ni and Au
plating before LPI solder mask in detail?  I can't figure
out how it is done.

Best regards,

Linda Li


-----Original Message-----
From: Eddie Rocha [mailto:[log in to unmask]]
Sent: Saturday, December 03, 2005 12:59 AM
To: TechNet E-Mail Forum; Li, Linda
Subject: Re: [TN] How to prevent solder mask peeling
problem for ENIG+ENEG circuit boards


I would have used the following sequence of processes:
 Electrolytic Ni & Au plating before LPI soldermask, etch
the outer layer image, LPI soldermask, peelable mask (to
protect the electrolytic gold features, then ENIG. I
wouldn't expect soldermask adhesion problems with this
approach.

Thank you,
Eddie Rocha
South Bay Circuits


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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