Gerry,

I have had to deal with this situation before. I came to a simple conclusion which has been accepted by my customers. It is as follows.

FACT: HASL can be and should be considered a form a thermal stress. Actually the process 
          in more in line with a thermal shock. During the days of tin lead plate and reflow, at 
          least the panels were processed thru a preheated pot of oil before seeing the actual 
          reflow temperature. Most customers should agree with this. Therefore, any cross 
          sections done at final inspection is in fact after some degree of thermal stress.

To remedy the problem of establishing objective evidence in the form of cross sections, I would recommend you get your customer to agree to a section after tin lead plating prior to HASL. This should satisfy all parties concerned and resin recession should not be present.  You should also be able to quote the military requirements for as received sections. It is generally accepted that if it meets Mil-P-55110 requirements is should meet any unspecified IPC commercial standards.  The 55110 spec also defines "as received" as after solder coated ( see para. 3.6.2.3) . Since you product does seem to meet all specified requirements, have you asked you customer what the concern is? Perhaps someone is questioning resin recession due to some problem experienced in the past that has nothing to do with resin recession.  Just a thought. Hope this helps.

Ed Cosper
Director Quality Assurance and Engineering
Graphic Electronics Inc.

----------
From:  D'Auteuil, Gerry[SMTP:[log in to unmask]]
Sent:  Monday, March 03, 1997 3:32 PM
To:  'IPC Forum'
Subject:  RE: Resin Recession


 ----------
   

I have a question with regard to Resin Recession prior to thermal stress.
  Both IPC-600 and 6012 only indicate an acceptable condition after   
thermal stress.  There is no mention of the acceptability of resin   
recession after HASL.  I am looking to find any information which I could   
supply to one of my accounts that would indicate what the criteria would   
be prior to thermal stress.   MIL-P-55110 paragraph 3.6.2.1.10.1 has a   
criteria prior to thermal stress.
This product is also in excess of 175 mils thick.  We have also recently   
moved to aprox. 175 degrees C,Tg material to alleviate lifted lands but   
we are now seeing more resin recession.  Would someone at TechNet  or IPC   
be able to comment on their views or  findings for Resin Recession prior   
to thermal stress?


 Thank you
 Gerry D'Auteuil
E-Mail [log in to unmask]

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