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

Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.


Board contamination

Mario Carluccio

#4423

Board contamination | 13 April, 2000

Can anyone advise me what are the types of contaminants which can be present on a printed circuit board at the very beginning of a SMT line. Of these contaminants, are any of them detrimental to the SMT process (i.e. label application, or solder paste printing) and therefore must be removed beforehand?

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#4424

Re: Board contamination | 14 April, 2000

Mario: Your ask a very broad question and give no background information.

Generally, the amount and type of residues present on a printed circuit board at the very beginning of a SMT line depends on the exposure of the board up to that point. For instance: * Process used to fabricate the board. * Processing and handling after fabrication and before SMT.

So, how was your board processed and handled to the point of concern?

I would surprised not to see ionic and non-ionic residues on your board. Possible sources of these residues are: IONIC RESIDUES: Salts from etching and plating, salts from flux, flux activators, rinse water minerals, MEA from saponifier, salts from saponifier, fire retardant salts, and salts from finger prints. NON-IONIC RESIDUES: Rosin or resin fluxes, polymers from fluxes, polyglycols from fluxes, diethylene glycol monobutyl ether from saponifier, oil from finger prints, and soldering oil.

So, what are the incoming board cleanliness requirements that your purchasing and quality people impose on your suppliers? And, what are the handling requirements for materials that you apply between incoming and SMT assembly?

Final question Mario: What�s the problem?

It's a beautiful day. I'm starting the weekend. Mike C what's that four letter word? Golf!!!!

Have a nice one all!!! Dave F

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