Ioan
I submitted a lot of the wetting balance data for J-STD-002 to the committee after we completed a very extensive study in AT&T. ( G.C.Munie, E.A.Heiser, P.C.Moy, D.A.Machusak, G.M.Wenger, "Development of AT&T's Internal Solderability Standard: Building on External Specifications and Assembly Experience", Proceedings of Surface Mount International 1995, San Jose, CA, August 28 - 31, 1995) This study was done at the AT&T Oklahoma City works on the assembly line and involved over a million solder joints, extensive solderability evaluation and reliability testing of all assemblies afterwards.
Some of that was incorporated in the standard. Over the years, (through much tutoring by George Wenger) I have come to take a slightly different look at wetting balance and solderability testing. At the risk of repeating what I've said before on this forum I suggest the following for testing:
1) Use the wetting balance equipment to control depth, time, temperature, etc.
2) Use the actual force results of the wetting balance to assess your solderability. The values I recommend are in the reference I listed above.
3) ONLY use water white rosin flux for testing. (See reference.) NEVER EVER use ANY active flux. Yes, it will "smooth out" the wetting results when done at different times and locations but it will not give you a measurement that reflects real manufacturing processes on your line. I expect some brickbats on this statement!
4) If you want to simplify interpretation and avoid using the numbers from the balance use the balance to control your dip and look but ONLY accept parts as solderable if they show ACTIVE wetting with water white rosin flux.
On the last point I define active wetting as the solder spreading beyond the immersion limit. And I defend that assesrtion by noting that active wetting is exactly the process you want in manuafcturing. You want the solder to wick up the hole. You want the solder to wet up the lead to form a good heal fillet. Coverage alone without solder spread is meaningless for manufacturing. But that coverage MUST be demonstrated with non-active flux.
Greg Munie
-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Tempea, Ioan
Sent: Monday, April 23, 2007 9:13 AM
To: [log in to unmask]
Subject: [TN] solderability testing
Hi Technos,
I need to setup a sort of solderability testing process.
J-STD-002 is pretty clear, but I would like to know how are you set up for the job. Mainly I would like to be able to make a decision on dip and look OR wetting balance?
What kind of equipment are you using?
How to make the tests less of a black magic and more of a repeatable process, with easy to interpret results?
Thanks,
Ioan
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