Printed Circuit Board Assembly & PCB Design SMT Electronics Assembly Manufacturing Forum

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facing cold joint problem

#26923

facing cold joint problem | 18 January, 2004

we are facing cold joint problem in selected component please advise me possiblity of this problem

imtiaz

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#26924

facing cold joint problem | 18 January, 2004

Materials added to solder can change its appearance. For instance: * Gold in tin/lead solder is dull / grainy * Palladium in tin/lead solder is dull / grainy

We do NOT advocate using visual appearance to define the appearance of a good and a bad solder joint.

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#26927

facing cold joint problem | 19 January, 2004

How did you come to the conclusion that you are having a cold joint problem. Just by appearance ?

As Dave stated if you have any of the metals that he listed in the joints they will appear to be dull and grainy sometimes.

But... Dave, I will have to dissagree with one thing that you said to a degree "We do NOT advocate using visual appearance to define the appearance of a good and a bad solder joint."

I just had a meeting in our facility with an applications engineer from a very reputable paste manufacturer. He told me that appearance is a very good indicator to the quality of the solder joint. I have never in my 13 years of in the trenches process experience observed a shiny joint with good fillets that was faulty.

If you think you are seeing cold joints, then the first thing to do is check your reflow profile. I am not sure what kind of component you are speaking of, but high thermal mass on a particual part could cause a cold joint.

I agree with Dave on this point: Component and/or circuit pad metalization. Check your component supplier for specs on the lead metalization of that particular part. If you are only seeing it on one part then there is probably a metalization issue. You could also have old parts...have you checked date codes ?

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