Electronics Forum | Tue Jul 30 12:15:15 EDT 2002 | Rick Lathrop
Hi Dave, The paste applied to the board ends up on the tombstone. The pad has a thin covering of solder most of the time, this is why I think they call it a dewet. Occasionally the pad shows some areas of gold and very rarely are some pads not wet at
Electronics Forum | Tue May 13 08:26:29 EDT 2008 | davef
First, on your reflow temperature comment: The 183*C focus for reflow recipes for tin-lead solder is a falicy. If you held a recipe for tin-lead solder at 183*C peak, it would never reflow. Recipes for tin-lead solder need to be at liquidus plus 20*C
Electronics Forum | Thu Oct 28 09:25:35 EDT 1999 | Dave F
Chris: Typical non-wetting causes are: * Poorly controlled soldering process * Incorrect material * Surface contamination * Insufficient preheat * Misapplied solder mask * Shadowing Without intending to insult you, all of the causes of non-w
Electronics Forum | Wed Oct 27 19:50:59 EDT 1999 | chris
Hi What is the possible cause of non-wetting of solder paste to the gold land pad. What we observed in the surface of the non-wet pad is an organic FM, and using FTIR we found out that it is a flux. It is possible that the cause of non-wetting is
Electronics Forum | Thu Nov 07 12:35:38 EST 2002 | slthomas
Sounds like you're talking about the "heel" of the lead not being soldered, in other words, no heel fillet, which IS necessary. That problem, for us, was attributed primarily to poor layout (insufficient length of pad extension to provide room for
Electronics Forum | Wed Nov 06 19:03:33 EST 2002 | broncos
If you are certain that reflow process is good, I would suggest starting checking the following: 1. Check to see if leads / pads are contaminated or oxidized. However, this usually results poor solder quality throughout the board. 2. Check the amou
Electronics Forum | Wed Nov 06 16:31:59 EST 2002 | slthomas
I would also consider paste control (don't take it personally...I always have to get after people about this one), time on the stencil, time between print and reflow, solderability of the component leads, paste volume (that one really got us once....
Electronics Forum | Fri Nov 05 10:01:04 EST 1999 | Dave F
Chris: You can have more than "one question!!!" Anyhow, yes crappy solder paste can cause non-wetting, but before you go there understand why the paste is wetting some surfaces, but not others. Ta Dave F
Electronics Forum | Thu Nov 04 21:36:36 EST 1999 | chris
Hi John, Thanks to your reply, just one question is it possible that the solder paste ( flux material )applied to the pads cause the non-wet. regards Chris
Electronics Forum | Thu Oct 28 20:45:38 EDT 1999 | chris
Hi Dave, We suspect that the organic FM causes the non-wetting problem. FTIR analysis confirm that the FM is a flux residue. Dave we only used FTIR to detect organic contaminants, we also used SEM/EDX to determined the elemental composition of the
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