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Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.

Insufficient solder joint

Paul Peterson


Insufficient solder joint | 14 December, 1999

I recently encountered reflow soldering defects on a pair diode package, the smd pad had a green contamination, I'm convinced that this is not oxidation. The no-solder condition appears to be caused by a sloppy soldermask process, although over the years I've not experienced this problem before. The defects affected at least 6 panels from the lot. Does anyone have any insight to this process that might be helpful. Also visual inspection would not be reliable, are there any sorting technics that will catch these defects previous to screen printing. Thank you.

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Re: Insufficient solder joint | 14 December, 1999

I think you're on the right track Paul. You didn't mention what type of solder mask was used but I'll presume that it was LPI (liquid photo imagable). If development of the image is incomplete some mask can remain where it is unwanted. Sometimes improper exposure or contaminants can have the same result. You shouldn't have to inspect for this. Talk with your vendor. It's up to him to take care it. John Thorup

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Re: Insufficient solder joint | 14 December, 1999

Hi Paul,

you got to find the reason first before any measures can be taken. You have to determine wether it happend somehow at your site or at the boardhouse, you can�t blame them without reason. As long as it is suspected that more of those panels go to the assembly I would say that optical inspection is the easiest thing to do. Depending on the appearance of this irregularity it might be noticeable with minimal optical equipment. Good operators have the feeling to look at suspicous things if they know what they are looking for. Once the cause is detected corrective action can be taken. Maybe it�s a one time error ( soldermask contamination tends to be it with most of the board houses )than you can cancel the inspection after an appropriate time, means the next 2 or 3 deliveries.

My 2 c


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Chris May


Re: Insufficient solder joint | 14 December, 1999


I have (as many have) come across this problem due to misregistration of resist at the PCB fab. You didn't say if these boards are inexpensive double sided or costly multis. I know this shouldn't make a difference on quality but I would tend to make noise in proportion to the costs.

You do not really want to 100% inspect incoming boards / panels etc; but a sample inspection never hurts.

Discuss this with purchasing and QA (and supplier). Has the supplier maintained a good vendor rating ? Are they normally very good and this is a hiccup ? Is it a new / diferent supplier ? ( Has purchasing started using "Boards 'R' Us" ? ) You should pass this problem back to your supplier.Reject the boards and ask them to explain how this has happened and what preventative measures they will enforce so that it doesn't occur again. Visit them and see if you feel comfortable with their process controls etc; They should be able to trace your batch of boards and it may be that a new operator was involved.

At the end of the day, you are the customer !



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