Electronics Forum | Tue May 25 11:37:50 EDT 2010 | davef
Where on the assembly is the dewetting occurring? Factors that influence dewetting usually involve non-ionic contamination such as: * Residues from board manufacture including silicone surfactants from solder resist & HASL rinse contamination * Comp
Electronics Forum | Thu Dec 06 11:01:19 EST 2001 | Carol Stirling
This SMT process certainly makes a body want to win the $$$ and retire! We have been trying to stabalize the process and keep running into new problems. Any help would be appreciated on this issue. All pads on both sides have the same look - partial
Electronics Forum | Thu Dec 06 19:46:08 EST 2001 | davef
First, we�re assuming that we�re talking hot air solder leveled [HASL] bare boards, eh? Consider using A-600 - Acceptability of Printed Boards as the basis for discussing the bare board problems. It is the bare board analog of A-610 - Acceptability
Electronics Forum | Tue Nov 05 12:34:54 EST 2013 | rgduval
3-6 months, say, depending on the environment), I might consider a ramp-soak-spike profile to allow sufficient time for the flux to clean any potential contaminants. Cheers, ..rob
Electronics Forum | Wed Nov 06 03:51:28 EST 2013 | cuperpeter
Hi rob, Thank you very much for your response. Profiling was made exactly on the pad, which showed dewetting, so the values are mentioned for this pad. PCB's is about a week old. It is possible that the surface of pads is already oxidized? I will t
Electronics Forum | Tue Nov 05 09:57:45 EST 2013 | cuperpeter
Hello All, We have a problem with dewetting of solder paste. Problem is most visible on the pads without components (see attached pictures) and occurs randomly, 20% of PCB's. Pcb supplier sent us a cross-section of pads with thickness of Cu, Ni and
Electronics Forum | Wed Nov 06 10:03:59 EST 2013 | rgduval
Hi, Peter, I'm not an authority on surface finish thickness, and it's effect on reflowing, so, I can't advise on that front. If the boards are a week old, and ENIG, I would not suspect surface contamination. It's always a consideration, of course,
Electronics Forum | Fri Mar 06 10:46:35 EST 2009 | davef
First, we agree with Loco that your QFP is nonwetting, rather than dewetting. Your sceen-shots look like ol' timey SnPb paste recipes. Turn-up the heaterometer dial. Second, on nitrogen: * We kinda think your O2 needs to be around 100ppm with 99.99%
Electronics Forum | Fri Mar 06 11:01:53 EST 2009 | dyoungquist
I have attached a pdf version of an article that explains the basics of a nitrogen atmosphere when soldering. It gives some basic guidlines as to when one may want to use nitrogen and what it can and can not accomplish. FYI- I did not write that ar
Electronics Forum | Thu Mar 05 11:53:09 EST 2009 | dcell_1t
Hello to all. for certain time, we have been struggling with some issues on a PCB where have tombstoning on 0402 components (due to pad design) and dewetting in qfp256 0.5 mil pitch (discussed on another threads on this forum) component, we have pro
