Components randomly wiped out in reflow

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Hi experts, I have some multiple and randomly missing compo... - Mar 22, 2018 by Diego

hello Diego, I would start by opening oven and looking fo... - Mar 23, 2018 by bukas

You should answer two questions. 1. Were the components plac... - Mar 23, 2018 by Evtimov

What sort of components are missing? One possibility is m... - Mar 23, 2018 by dwl

Normally some random components of size 0604 or below and ma... - Mar 25, 2018 by Diego

Hello Diego, are the components missing on the first side o... - Mar 27, 2018 by Buckcho

Diego

#80052

Components randomly wiped out in reflow | 22 March, 2018

Hi experts, I have some multiple and randomly missing components after reflow. PADs are seen in AOI as if the component was never there. I have seen no evidence of the chipmounters missing any components at all while populating the board. We don't have AOI pre-reflow but we do have doubts regarding to what is going on inside the oven, however, it can not be stopped in production.

What would you recommend to do to diagnose this problem ?

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bukas

#80053

Components randomly wiped out in reflow | 23 March, 2018

hello Diego,

I would start by opening oven and looking for missing components. once you locate them you can work from there. are you using any alu caps on your board? I had problem with bad alu caps exploding in oven and scattering other components. you can also check impact force of PnP machines and oven blowers. I assume you already checked oven chain conveyor, that plastic curtain barrier between zones can also be a problem. Some images of PCBs and info on your machinery will help too.

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Evtimov

#80060

Components randomly wiped out in reflow | 23 March, 2018

You should answer two questions. 1. Were the components placed? 2. If first answer is "Yes" Are there components in the oven?

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dwl

#80062

Components randomly wiped out in reflow | 23 March, 2018

What sort of components are missing?

One possibility is moisture sensitive parts outgassing during reflow. The jets of steam propel the parts off the PCBA.

Another thing to look at is your convection oven fan speeds. On some ovens this is adjustable, and if set too high, might be blowing parts off the boards.

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Diego

#80064

Components randomly wiped out in reflow | 25 March, 2018

Normally some random components of size 0604 or below and may be due to a thermal mass being close like a transformer or AC electrolytic caps.

We tried changing fan speed, but this will change the thermal profile and avoid the thermal mass from being correctly soldered out.

Now that you mention moisture outgassing, I wonder if this could be the issue. It does sound reasonable and also fits with some bigger components being moved. The solder paste could also have flux outgassing.

I wonder if there is any kind of high temperature camera to collect more real information of what happens inside the oven.

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Buckcho

#80078

Components randomly wiped out in reflow | 27 March, 2018

Hello Diego, are the components missing on the first side or the second side. Like Mr. Evtimov said, you can check before the oven the pcbs's visually and see what happens after the oven. In this way you can see if it is the oven for sure. Then there are most likely 2 options - components from top side falling due to big temperature and thermal mass when producing bottom side or popcorn effect. If it is popcorn - sounds more like outgassing of moist pcbs. But in popcorn you can be lucky sometimes to see components all over the panel and boards. You can try also drying the panels if that is your case.

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