Yes, Bob,
well recognized. We were stunned by solder balls looking like rotten teeth after the soldering/cleaning process. Typical was that all the "caries" holes were on one and the same side of all balls. Explanation: a)the balls consisted of two zones with different grain phases, caused by the BGA maker's production method. b)we used a flux cleaner that dissolved poor grain bindings in this two-zone interface and the result looked like what happens when a mouse takes a bite in the cheese. Well, there is a whole report about it and MOTA changed the ball concept, since then I have heard of no more such problems. If you want some pictures for comparison, I can send to you, Bob.
It's strange that we still get some soldering problems after decades of knowledge about the processes. One reason may be this: old 'goodies' disappear, newcomers more interested in IT and stockholding affairs. I knew such an ol' goodie at a company, a metalurgical dr from Germany, he WAS soldering personified (devotion and deepest interest), but when he retired noone took over, the lab personel was spread and the new bosses spent no more money. Many new in the game just scrap the surface of the mystery of soldering. Luckily, we have TWI, IM and other institutions nearby, in US there is China Lake, Sandia, Rome, IBM and....and Klein Wassink's soldering bible...oceans of knowhow for those who like digging after treasures.
I take the opportunity to ask about silver adhesive vs. soldering. Just wonder how many percents of the worlds component mounting is done with adhesives instead of solders. The adhesive makers claim that their products fit well for most applications, but many, many hesitate to change from solder to 'glue'. I don't ask for a storm of pros and againsts...not at all, just a qualified guessing from someone: how many percents? What do you think? 5%?
There is a risk that some oldies will talk, how do we stop them? (He-he)
Ingemar Hernefjord
Ericsson Microwave Systems
-----Original Message-----
From: Bob Perkins [mailto:[log in to unmask]]
Sent: den 20 mars 2000 22:01
To: [log in to unmask]
Subject: [TN] Voids in BGA Balls after reflow
Hello Technetters
Recently with the help of a high end piece of x-ray equipment we
have noticed voids in the spheres of the bga after reflow, "see
attachment-file". Has anyone seen this before, or has any idea how the
voids are created? Also does anyone know if this is a bad or good thing?
Does anyone have any recommendations to the profile?
Thanks
Bob Perkins
Automation Technician/Manufacturing Engineer
Aimtronics
[log in to unmask]
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