Electronics Forum | Sat May 02 23:31:06 EDT 2009 | kareal
Thanks davef. The defect always occurred during UHAST reliability, but not find in reflow. The key is that there is tin diffuse to copper trace under solder mask. is it a "normal" board defect and what is the potential risk for device? thanks!
Electronics Forum | Fri May 08 04:39:32 EDT 2009 | kareal
Hi Davef, I want to explain that the tin diffusion in my project is not on solder bump/Pad region. It is on copper trace between bumps. so it is very wondering for me.
Electronics Forum | Fri May 08 09:44:23 EDT 2009 | davef
Board fabricators use solder as a resist to protect copper traces from process chemicals. Fabricators remove this resist in later processing. It's possible that board fabrication processing is the source of the tin that you see.
Electronics Forum | Mon Jun 20 02:43:55 EDT 2011 | milroy
What is the correct FR4 for RoHS? This PCB is a 4layer board. When we get the boards from the supplier they are properly packed in vaccum sealed bags without HIC card but there is desicant in side.
Electronics Forum | Fri May 01 07:22:56 EDT 2009 | kareal
In my project of flip chip PGA production , I found serious delamination in interface of solder mask and first layer copper trace of substrate after UHAST 96hrs( 130C, 85%RH) reliability test. The delamination are always around one type solder bump,
Electronics Forum | Mon Jun 13 09:43:11 EDT 2011 | mosborne1
Delamination almost always is caused by moisture in the PCB. You can try to keep some of the PCBs in a dry box after recieving them. You can also slowly heat them up to bake out moisture. If you are purchasing boards form overseas form a board house
Electronics Forum | Thu May 07 08:11:58 EDT 2009 | davef
We don't have a good answer for you, but we do have several thoughts on the issue: * First, tin in your solder or solderability protection is going to diffuse into the copper trace or pad on the board naturally. You can stop that by using a protectiv
Electronics Forum | Thu May 07 19:29:40 EDT 2009 | kareal
Hi Davef, Do you means it is natural for tin diffusion to copper trace during SMT process? but I could not detect tin in UHAST T=0 unit, and the tin diffusion was found only in copper trace of C4 cage. Two question: 1) Could you tell me which pr
Electronics Forum | Sat May 09 23:05:17 EDT 2009 | kareal
Davef, It seems the tin resist residue on copper trace is root cause of whitish layer. but it could explian why I could not detect tin on fresh unit without UHAST. I have performed X-section and EDS analysis on many fresh units,but no any tin was
Electronics Forum | Sat May 09 09:00:54 EDT 2009 | davef
For more on using tin as a resist during bare board fabrication, read "2.5.6 Introduction To Tin And Tin/Lead Plating" here: http://books.google.com/books?id=etfNcpiR5ZUC&pg=PT570&lpg=PT570&dq=%22circuit+board%22+%22etch+resist%22+%22acid+sulfate%22&
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