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
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 | Fri Mar 06 16:17:38 EST 2009 | aj
whats your board finish?
Electronics Forum | Fri Mar 06 10:50:21 EST 2009 | fountain42
Just my opinion but it look's like your doing a great job. i would try another paste. I'm somewhat lucky that we get to use OA's. If your stuck using the no-cleans they are so tempermental. (The nitrogen is making up for the poor paste) Your de-wetti
Electronics Forum | Fri Mar 06 02:47:15 EST 2009 | lococost
Have you tried higher peaktemp? I saw the QFP is sn90pb10, This has a liquidus of 268 - 302 C. A good paste should be able to handle 230C (or more), of course you would need to check your other components peak temp.
Electronics Forum | Thu Mar 12 06:37:48 EDT 2009 | gregoryyork
I agree you are too cold for the profile get it up to 230C and possibly allow it to dwell a little longer in preheat as opposed to pushing up the reflow zone only. Sn90/Pb10 melts at 220C so 2C hotter than your profile so you are reliant on it alloyi
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