Electronics Forum | Mon Nov 26 21:41:09 EST 2007 | davef
Shy: Oh, we NOW understand what you're asking. Sorry to be so dense. We agree that the standoff of component from the board could end-up being a little heigher than the pad height when using chipbonder adhesive. We rarely see a problem.
Electronics Forum | Tue Nov 27 04:50:45 EST 2007 | lococost
you say you use the glue to keep the components on during wave, why would you want to solder them twice, once in reflow and once in wave?
Electronics Forum | Tue Nov 27 06:11:42 EST 2007 | shy
Hi Loco, my PCBA got top side and bottom side and 90% SMT and 10% THP (top side) which need to be cover by wave solder. And that's why i need to go through reflow and wave.
Electronics Forum | Tue Nov 27 07:27:58 EST 2007 | realchunks
I'm still confused. Why reflow solder a part when you're going to wave solder it? Seems like a waste of resources and material.
Electronics Forum | Tue Nov 27 07:36:29 EST 2007 | shy
solder the part is for SMT component (located at top side and bottom side) and wave solder is for THP (located at top side only).
Electronics Forum | Tue Nov 27 07:44:59 EST 2007 | davef
We do not paste when we glue. We glue components so they will stay inplace during wave soldering. In wave soldering there is ample solder to bridge the standoff between the component and the pad.
Electronics Forum | Tue Nov 27 07:51:21 EST 2007 | shy
is there any gap between the pad and terminal if we place the glue? Btw, my practice to print solder pate then punch glue then PNP component and finally reflow. Also we find drop/missing chip after wave eventhough we glue the component.
Electronics Forum | Tue Nov 27 08:21:43 EST 2007 | shy
How many mils the gap between the terminal and pad? Your practice is for technology SMT-4? What is problem with glue cure? is it due to the reflow profile? how long the glue can be keep in room temperature with humidity 40-60?
Electronics Forum | Wed Nov 28 06:52:33 EST 2007 | davef
So, you're curing glue on a thermal recipe intended for reflow even though your supplier recommends that you cure at 150C, because you want to use paste that isn't necessary.
Electronics Forum | Wed Nov 28 06:56:57 EST 2007 | shy
the paste is necessary for the component that had no glue. btw, for solder paste specs, 150C is at reflow time plus soaking time and i believe it will cause nothing to the glue and can cured as per recommended? correct me if i'm wrong.
