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Contaminants after SMT which affect wire bonding

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Chris

#44346

Contaminants after SMT which affect wire bonding | 5 October, 2006

Hi all experts,

I have no background about PCB or SMT process. I am now encountering some issues after SMT - Unstable stitch bonding condition.

I am now suspecting some contaminants remain on lead after cleaning. Therefore, how can I check the lead surface's condition and what contaminants will affect wire bonding? I checked a equipemnt call Omega meter... which can check the NaCl concentration, what is the specification about the NaCl after SMT process?

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GS

#44375

Contaminants after SMT which affect wire bonding | 5 October, 2006

I am not expert, just my comment,

the total ionic contamination allowed after SMT, by using No Clean process, theoretically it should be close to Zero. Any way the Standard IPC-JSTD-001 allows 1,56 ugr NaCl/cm2 for the final Printed Board assembled.

Omegameter (ROSE) tells you only the equivalent NaCl/cm2 but not which kind of ionic contaminant is in it (Cl, Br, F, .?) If you want to know exactly wich kind of ione it is and rigth % you should run a Ion Chromatography Test.

Any way ( I am not expert) I do not think it is a matter of ionic contamination who compromise the wire bonding.

if suspect is that surface is contaminated, you could run a FT-IR test (at least) and see if the bonding surface is contaminated by some substance that could compromise the bonding.

sorry for my English.

Regards....GS

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David

#44390

Contaminants after SMT which affect wire bonding | 6 October, 2006

Hello,

Do you have lift bonds?>

What is the solder finish of the board?. If this is gold, maybe you should check the reflow profile and max temperature which can easely kill your gold coating so problems with bonding.

Also we are using Prozone Multicore with ultrasonic to clean the board after lead free no-clean process. It is helpfull with getting good strong bonds.

Regards

David

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