Poh:
I believe what you are seeing is a reaction between the 245 flux residue and
the solvent/carrier in the 955. The 245 core solder leaves behind a
rosin/resin encapsulated residue on the board. The 955 flux contains a large
amount of 2-propanol, I believe about 90%. This alcohol in the 955 will
react with and disturb the 245 resinous flux shell. It will start to break
it down but not completely solvate it. It results in a powdery white
granular appearance that can be a collection site for contaminants and
moisture.

To clean the existing assemblies you can use a solvent cleaner and a brush.
Typically ones designed for rosin and/or resin removal seem to work best.
Some of the Bioact and Flux-off spray cleaners will work but all require
mechanical help. Apply cleaner, brush and re-apply cleaner until flux
residue is gone.

To prevent it on future product you may want to use Kester RF741 auxiliary
flux in place of the 955.


Regards

Michael Barmuta

Staff Engineer

Fluke Corp.

Everett WA

425-446-6076



-----Original Message-----
From: Poh Kong Hui [mailto:[log in to unmask]]
Sent: Saturday, June 22, 2002 8:17 AM
To: [log in to unmask]
Subject: [TN] : White residue using Kester flux & wire


Hi All,

I have problem using the Kester 955 flux with R245 wire.

We manually used these material to solder a row of connectors.

In term of soldering quality, it is alright, except it turned
white after 3 to 4 days.

Is there anyone has experience such issue, and what can I do
to prevent this from happening.

Our customer is not very happy with the white stuffs, but
there is not solution to the issue.

Thanks.

Poh

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