Electronics Forum | Thu Nov 21 06:36:30 EST 2002 | Ben
I'm doing SMT of lead-free solder BGA on FR4 Ni-Au PCB. The solder paste I'm using is Sn/Ag/Cu and reflow with peak temp at 240C. I found there are voids(1-2) in almost every solder joint(500 micron in dia) under xray. And the void size is violate th
Electronics Forum | Wed Oct 20 14:24:32 EDT 2004 | Steve Gregory
It all depends where the voids are, and that's tough to do with a transmission x-ray. One needs to be able tilt the assembly at 45-degrees during x-ray, so you can get an idea where the void is. Or, you spend some big bucks for an x-ray laminography
Electronics Forum | Wed Oct 20 14:44:24 EDT 2004 | Steve Gregory
It all depends where the voids are, and that's tough to do with a transmission x-ray. One needs to be able tilt the assembly at 45-degrees during x-ray, so you can get an idea where the void is. Or, you spend some big bucks for an x-ray laminography
Electronics Forum | Tue Jul 26 08:20:46 EDT 2005 | Bob R.
All you can do is try it. I did a literature search last year on causes of BGA voiding and came up with a pretty long list, sometimes contradictory. I also discussed it with several paste suppliers. What I came away with is that what aggravates voi
Electronics Forum | Tue Aug 21 20:52:06 EDT 2007 | davef
There is not standard for the force to pull an axial lead from a soldered connection. ".....IPC does not have pull tests in any of its standards, and some reliability experts would prefer to keep it that way, pull tests are commonly used by some lea
Electronics Forum | Mon May 25 08:37:28 EDT 2009 | d0min0
Hello, recently we changed supplier of the LF BGA, we did corossection and now have doubts... previous BGA specs : pitch 1mm, ball diameter 0.6mm future BGA specs : pitch 1mm, ball diameter 0.4mm on the crossecrion we found that one of the ball seem
Electronics Forum | Wed Feb 13 09:17:47 EST 2008 | scottp
The causes of voids are extremely paste dependent. I did a literature search a couple years ago and the papers all disagreed with each other - one would say turn knob "A" to the right and the next would tell you to turn it to the left. I did my own
Electronics Forum | Mon Oct 15 10:51:49 EDT 2001 | davef
On over printing, the general issues are: * Paste deposits being so large that when reflowing, collapse onto many, rather than a single solder mass. * Paste expanding during heating and being close to other solder deposits and bridging [as you say].
Electronics Forum | Thu Jan 24 19:57:40 EST 2002 | davef
Are there formalized standards for the properties of solder balls? No Get IPC-7095 �Design & Assembly Process Implementation for BGA's�. General comments about array package solder balls are: * Ceramic packages use harder solder, like 90/10. * Pla
Electronics Forum | Tue Apr 13 09:46:39 EDT 2004 | davef
Now, that's different. We misunderstood the problem from your original descrtiption. We thought the voids were showing at the via in the pad. Now, we understand the voids appear to be in the solder balls. Suggestions are: * Search the SMTnet Arch
