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Dewetting on QFP

#34791

Dewetting on QFP | 7 June, 2005

Hi there,

I have questions regarding on dewetting issue..

Q1) How to identify on good or bad ICs lead that could contribute to dewetting? Q2) What actions that must be taken in facing this issue?

Thank n regards,

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#34801

Dewetting on QFP | 7 June, 2005

Q1) How to identify on good or bad ICs lead that could contribute to dewetting? A1) Distinguish between good or bad IC that could contribute to dewetting by testing for solderability, according to J-STD-002.

Q2) What actions that must be taken in facing this issue? A2) It depends on the cause of your dewetting issue.

If we assume that you�re talking about the portion of the lead other than the toe area, poor solderability at the toe area of the lead , where the lead is cut, is acceptable.

If we assume that you have palladium solderability protection on your component leads, soldering to palladium: * Highly dependent on the specific flux activator. * Slower dissolution rate into solder than other metallic coatings (eg, solder, tin, silver, gold) that we typically see on components. This means you may have to alter your soldering recipe to allow for more soldering time. * Some people think a thick palladium finish can cause a solder joint to crack. * Some people think a thick palladium finish won't cause a solder joint to crack.

If we assume the improper wetting of Alloy 42, check whether the leads of the component are Alloy 42 [you can do that with a magnet]. If they are affected by the magnet, they are Alloy 42. If so, either your: * Peak reflow temperature was too low. You need about 15*C higher for Alloy 42 than copper * Alloy 42 is not solderable.

More detail about your situation would be helpful.

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