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Subject:	Re: Flux residue with a no-clean process, BGA Reballing
From:	[log in to unmask]
Reply To:	TechNet E-Mail Forum.
Date:	Thu, 31 Jan 2002 14:56:39 EST
Content-Type:	text/plain
Parts/Attachments:	text/plain (50 lines)

In answer to your question, yes the benefit can be lost if the component is
cleaned. We have worked with clients that have experienced problems with BGA
components that were balled using a low solids no clean flux. These units
were assembled with water-soluble solderpaste and cleaned in an aqueous
inline system. The low solids no clean residue absorbed the activators and
moisture from the assembly process and created a corrosion cell on finished
assemblies. I would recommend that good cleaning and drying process for the
components that will be subjected to aqueous cleaning of water-soluble
solderpaste.
We found that Ion Chromatography analysis corresponded well to the electrical
performance testing (failures had high chloride levels).

Terry Munson
CSL Inc.
P 765-457-8095
F 765-457-9033

<A HREF="www.Residues.com">www.Residues.com</A>

<< have a client using our Reballing system to recondition all sorts of BGA
and uBGA for re-use after de-soldering. They are currently using a water
soluble paste and cleaning with DI, however the residual absorbed moisture
presents a concern, so the devices are baked after cleaning. This increases
turnaround time, so they are considering moving to a no-clean process.

My opinion is that there will be residues and they could possibly be
incompatible with subsequent platforms utilized by the end user, as well as
creating aesthetic impact. Cleaning alternatives for no-clean fluxes rival
the more aggressive (therefore more forgiving) water solubles, so the benefit
is lost if cleaned.

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