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SMT electronics assembly manufacturing forum.


Flux residue cleaning procedure

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#44756

Flux residue cleaning procedure | 29 October, 2006

We have a current problem on our packages after we bake it for 24 hrs prior BGA rework. Flux or white residues found on the connector leads and terminals that cause not contact problems during mating. Could you help us how to clean the fluxes properly and how could this phenomeon happenned?

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#44783

Flux residue cleaning procedure | 30 October, 2006

As we understand it, you: * Get some nice BGA from your supplier * Find BGA to be packaged properly * Bake the BGA for 24 hours at [what temperature?] to reduce the potntial for damaging moisture sensitive components during following processes * Remove BGA from oven and prepare to rework a board * Observe the BGA making poor contact with the board, because the BGA connector balls are coated with a white residue

What changes would you make with this interpretation of the concern that you have?

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#44784

Flux residue cleaning procedure | 30 October, 2006

thanks for your inputs,but what i meant was that a connector component beside the BGA for repair has some flux residue on its leads after baking, the BGA was Ok.

we are wondering why this happened...pls enlightened us.

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#44785

Flux residue cleaning procedure | 30 October, 2006

So, after the repair of a BGA, you notice white reside on a nearby connector. Correct? [Sorry we're so dense. Long day.]

Tell us about: * Flux class used in repair * Flux class used in original assembly

Why are you baking the assembly after repair?

What cleaning process does the board see after repair?

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#44786

Flux residue cleaning procedure | 31 October, 2006

thanks for your reply, actually we bake the PCB assembly prior the rework because the package was exposed for quite some time already. The baking time was 24hrs @ 125 deg.C. We notice that there were flux residues on the connectors after the baking.

We just neglect it and we proceed to BGA rework, after repair of the BGA, we process through the assembly, then it was detected at testing process that it has connection problems on the connector.

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#44810

Flux residue cleaning procedure | 31 October, 2006

First, we assume the white residue is only on the connector and not on other components. That would imply that either: * White stuff was on the connector when it came in-house from your supplier. [Confirm this theory by baking some connectors from stock.] ... OR * White stuff is a reaction between the stuff on the connector when it came from the supplier and the stuff you put on it during assembly. [Perform experiment to confirm this theory.]

Second, the results of your testing suggests that either the connector was: * Never soldered well ... OR * Came unsoldered during rework of the nearby BGA

... which is it?

Next, the method for cleaning the white residue on the connector will depend on the composition of that material. You say that it is flux. What type of flux do you have on the connector?

Finally, whenever we hear "white residue" and "flux" used in the same sentance, we think: "low residue flux and water". Together low residue flux and water cause the flux residue to go milky white. [Hint: IPA is 50% water.]

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#44850

Flux residue cleaning procedure | 2 November, 2006

Thank you very much for your reply, we'll try to perform your advice. I'll feedback you soon for the results. 'till then...

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#44971

Flux residue cleaning procedure | 9 November, 2006

hams, whats the result?

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