Electronics Forum: bottom (Page 3 of 227)

Epoxy on bottom of SMT component

Electronics Forum | Tue Nov 27 14:56:33 EST 2007 | jaimebc

Shy, What is your current method of applying adhesive? If the terminals of the component that has adhesive are not wetting ( or not forming a solder joint I think we are talking about ) after reflow, then you must be applying too much adhesive. As

Epoxy on bottom of SMT component

Electronics Forum | Sun Nov 25 20:36:15 EST 2007 | shy

Hi Devaf, Sorry to make unclear statement earlier. I believe the issue that i'm trying to discuss is regarding the adhesive that place beneath (center) the component to prevent it from drop during wave soldering process. Normally the component pack

Epoxy on bottom of SMT component

Electronics Forum | Mon Nov 26 13:09:20 EST 2007 | realchunks

Even a slight amount of epoxy will prevent a part from soldering. Look at the part after print. If you any trace of you epoxy between the pad and part, you have a potential problem.

Epoxy on bottom of SMT component

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.

Epoxy on bottom of SMT component

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?

Epoxy on bottom of SMT component

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.

Epoxy on bottom of SMT component

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.

Epoxy on bottom of SMT component

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.

Epoxy on bottom of SMT 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?

Epoxy on bottom of SMT component

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.


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