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February 1997

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Subject:
From:
"Mohd Misri-RSB019" <[log in to unmask]>
Date:
Fri, 14 Feb 1997 8:30:00 +0800
Content-Type:
text/plain
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---------------------------- Forwarded with Changes ---------------------------
From: [log in to unmask]@INTERNET at #EMAIL
Date: 2/12/97 1:32PM
To: Misri Mohd RSB019 at ZMY04_CC03
*cc: [log in to unmask]@INTERNET at #EMAIL
*cc: [log in to unmask]@INTERNET at #EMAIL
Subject: Re: Discolouration in Electrochemistry
-------------------------------------------------------------------------------


I'm working with Semiconductor reel-to-reel solder plating process.
It is Solder over copper plating process.

 Among the problem that we face is "Discolouration", whereby the plated
products
change colour from shining white to gray, bluish or black marks.
This situation normally occure during production line stoppages. What we
observe is that chemical remain on the parts for extended period lead to 
oxidation process.

Our process flow is something like this

Cathodic stripping----->Anodic stripping---->acid Activation-->
 --->solder plating--->rinsing.

Those parts remain in acid Activation and solder plating are the most
critical.

Some of the thing that i tried were 
1)to immediately rinse the part when the production stop. The problem is that, 
the water rinse dilute the plating solution.

2)Reverse plating or deplate and plate.
    -Revese the cathode/anode polarity. The solder will be strip out during line 
    stoppages. Then replate again. This method fail soldaribility due to not    
    sufficient pre-cleaning and copper contamination.


Do you have any opinion on this?
Any other suggestion to resolve this problem?

regards
Mohamed Misri
ISMF
Seremban, Malaysia

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