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Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.


Process issue!Help!

Bryan She

#28337

Process issue!Help! | 30 April, 2004

I found much ICT fails on the same location(Ref.des:Q166) on my boards. 1.Defects rate:more than 20%. 2.We measured the value of the transistor before reflow oven,it's ok.but measure again after been reflowed,result is fail.it seems fails happen during reflow.we reviewed the profile...it's ok.peak:210~220C,rising and cooling slope<2C/s. 3.We use 20 pcs the same kind of transistors(same p/n and supplier) on each board,and fails only happen on the same Ref.des :Q166.we exchange the left parts with other production line,and also fails happen only on the same line. 4.when check the schmatics,we found the transistor is connected with a thermistor...R532. 5.after replaced with other good transistors,these board can pass the ICT. 6.reflowed the parts pre-mounting,measure the value of transistors with multimeter,it's ok.and after reflowed on board,fail happen. 7.The production line has the same configuration with other lines except that we use a reflow pallet on other lines,but the profile is the same. any suggestions or questions will be greatly appreciated!

Thanks a lot! Bryan.she@163.com Bryan

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Bryan She

#28343

Process issue!Help! | 30 April, 2004

In addition,the transistor is SOT23 packeage.it seems that after the reflow excursion,this parts was damaged.but...why this damage only happens on the same location on board?Maybe,i'd like to do a cross-section of the damaged parts. it looks strange. Regards! Bryan

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#28352

Process issue!Help! | 30 April, 2004

You're correct. It IS strange.

How do you determine that the part is damaged after reflow? With your ICT? Is it possible that the component is being damaged by an inappropriate command that is programmed into your ICT?

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RicardoF

#28354

Process issue!Help! | 30 April, 2004

you use reflow pallets on the other lines, can't you use reflow pallet on that one?

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Bryan She

#28359

Process issue!Help! | 30 April, 2004

we can test the defects with multimeter after reflow ,before ICT.and if we replace this damaged parts with good ones.everthing is ok.I'm sure this part is damaged during reflow,but why not other 19 same parts of the 20 on each board?we attach a thermal couple on the point,profile seems good. I dont know whether the reflow pallets affect.but I've learned this kind of defects also happen on other lines,but the defect rate is rather low. it's random these large defect rate happen on which line. I am totally frustrated these days with "same J6 corner ball open issues of CSP,SOT23 transistors damaged on same ref.des.Why does so many same things happen?

Bryan

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#28361

Process issue!Help! | 1 May, 2004

Try rotating [eg, 90*, 180*, etc] the board prior to running it through the oven. Ditch the pallet, as a previous poster suggested.

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soldering station

Reflow Ovens thermal process improvement