At 350C you should be flushing the work area with nitrogen. This will slow
down charring/caramelising of the flux and simplify removal. 

You might find a die attach type paste is more suited to this application.
They are formulated for high Pb and post solder cleaning for wire bonding.  

Probably you will find a semi-aqueous (as opposed to a solvent) process is
best. 
Speak to recognised flux removal companies. They will already have
investigated the best material/process recommendations for cleaning to wire
bonding standards.

Regards


Mike 


-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of jonathan noquil
Sent: Monday, February 08, 2010 5:47 AM
To: [log in to unmask]
Subject: [TN] Flux Cleaning

Hi All
What is the best flux cleaning agent that can effectively remove flux on
ENiAu bond pads?
We solder a copper strap on the silicon with PbSn5 at 350 degc temperature,
the flux contaminates the bonding pads.
Paste is from Heraues. We used an ultrasonic cleaning equipment.
During Au wirebonding, we have lots of bond off occurences? We tried to do
FTIR on the surface and found some traces of that resin contamination.

Is the flux difficult to remove with flux cleaning agent when it was
reflowed at high temperature?


Thanks


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