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Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.

Clean the No-Clean

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Clean the No-Clean | 13 February, 2006

Hello, I am automating a process on our floor from wire solder hand application to dispensed paste and reflow. The process involves "lidding" a shielding lid around our assemblies for microwave quieting. The result is non-hermetic. For cosmetic purposes, we need to clean the residue on the exterior of the part, but we need to use no-clean as we cannot reliably clean the internal residue. With the hand soldering application an ultrasonic IPA bath did the trick, but with the higher flux content of paste we have found that our usual soak and dehydrate (even with some brushing) does not remove all flux residue leaving behind a nasty white crust. I am looking into alternate cleaning solutions/solvents, but it is preferable to not have to soak at all as the "lid" or shield will trap fluid inside and I am doubtful of the dehydration bake's effectiveness. In short,

Could you recommend a no-clean paste formula that is cleaned easily? or Could you recommend an effective cleaning process that will not flood our assembly's interior and minimizes operator effort and time? Best regards, -Russ

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Clean the No-Clean | 13 February, 2006

Some low residue [no-clean] flux residues are cleanable, others are not. Talk to your paste supplier for a recommendation of cleanable low residue flux.

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Clean the No-Clean | 13 February, 2006

I'd check around for a wire solder that doesn't leave as much residue behind or a "clearer" residue behind. Or tell your customer you can save them a few bucks by just soldering a few points on the lid (since it's a air tight seal).

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Clean the No-Clean | 13 February, 2006

Here are some cleaning chemistry companies that have products to clean no-clean flux residues:

They all have engineers on staff that can assist with setting up a custom cleaning process.

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Clean the No-Clean | 13 February, 2006

Cleaning no-clean is the pitts. If cleaning required migrate to water soluble.

Can IPC help here? No cleans only need to be removed per IPC if the joint inspection is inhibited...and in general if form-fit-funciton is not achievable. But then there is always that annoying customer who insists it be removed merely on the basis of cosmetics (even though the product is burried in a chassis, kept in a dimly lit dungeon in an Artic region) I will assume this is a customer driven specification. In which I will recommend re-evaluating no-clean solder pastes in addition to new cleaning chemistries. There are cleaning service providers that would gladly walk you through the process and have much experience in these matters (for a fee of course).

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Clean the No-Clean | 15 February, 2006

I have used Indium SMQ 92 H (not the newer J flux type) It cleans perfectly in the aqueous cleaner. Ionograph results come up clean.

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