Rudolph,
I don't think the residue left behind from the no-clean process is the only
potential problem area.
It is my opinion that you must check for ionic contamination on a sample
basis on all assemblies.  If you think the components always come in clean
just think about how they build them.  One of the last steps of the assembly
process is tin/lead plating.  They use very corrosive materials (Methyl
Ethyl Bad Stuff) to clean the leadframes then more bad stuff to plate on the
tin/lead.  Most of todays in-line plating systems are very sophisticated
with tight controls, however, almost everyone has experienced a glitch from
time to time.

We use an Ionograph to check for ionic residues on components.  We do lead
tinning of component leads and have not failed a solderability test in years
since implementing routine ionograph testing. (Knock on wood) We also did
lots of other things.  I believe there is some good discussion of the
equipment, test methods and theory of fixed vs automatic cycles on the
equipment in the TechNet archives.  Try searching on "ionograph" or "ionic".


-----Original Message-----
From: Rudolph Yu <[log in to unmask]>
To: [log in to unmask] <[log in to unmask]>
Date: Tuesday, September 01, 1998 5:50 PM
Subject: [TN] Inspection criteria for no clean assembly?


>Currently we accept no clean assembly as long as we can not see stain
>mark or powder residue on the assembly within 2 feet after the wave
>soldering process.  What is yours like?
> Is there a need to check for contamination level on no clean assembly?
>If the answer is yes, then what measurement should I test it against?
>What tester in the market does serve this function?
> The reason why i ask the question is because I heard that even no clean
>flux does contain small amount of corrosive material, thus can affect
>the product in long run.
>Thank you
>
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