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Mixing No-clean and water soluble processes

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#61202

Mixing No-clean and water soluble processes | 23 February, 2010

Is there any harm in washing SMT soldered with NoClean paste? The PCA has some large thru-hole connectors that we would prefer to do as water soluble on out selective solder but the SMT consists of LGA's and other low parts that we would not be able to adequately clean under. The wash is strait DI water.

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#61206

Mixing No-clean and water soluble processes | 23 February, 2010

There should be no problem. Recognize that the residue of some low residue fluxes turn a milky-white color when you wash them. This could freak your quality people.

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#61209

Mixing No-clean and water soluble processes | 23 February, 2010

Davef is right on as usual. We are doing exactly what you do. Some smt with no clean paste then the plate through connectors on our selective solder machine using water soluble flux. We then clean with a ultrasonic water process. We do see the residue from the no clean paste turn a milky white color. We have been doing this for over a year, have sold a few hundred modules and have had no issues in regards to the flux and cleaning.

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DRT

#61211

Mixing No-clean and water soluble processes | 24 February, 2010

Agree with what has been said so far. Check with your end customer and make sure the white haze appearance of the board will be acceptable. You will never get the board to look like it did before you started. It may be clean but it won't look like to some people and possibly cause for rejection.

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#61212

Mixing No-clean and water soluble processes | 24 February, 2010

Thanks for the input! We are doing a few protos this week and we will see how they go!

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XPS

#61216

Mixing No-clean and water soluble processes | 24 February, 2010

Hi Vince, we don't know, which kind of flux no-clean was used, and which reflow profile also was used (standard or lead free)?

Anyway, white residue formation is known to occur after PCAs are cleaned in an aqueous cleaning system where the water temperature is relatively high (> 60° C).

Moreover (by IPC standard)... "White residues resulting from no-clean or other processes are acceptable provided the residues from chemistries used have been qualified and documented as benign...".

So, use an EDX or IC analysis in order to qualify the final result... XPS analysispcb.com

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#61217

Mixing No-clean and water soluble processes | 24 February, 2010

I apologize for being so vague. It is a standard leaded process using ALPHA OM-5100 for the SMT. So would a reduction in wash temp result in less white residue?

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XPS

#61225

Mixing No-clean and water soluble processes | 25 February, 2010

Sorry, but I don't know this brand. Anyway pay attention, because if the chemistry is resin based, is difficult to clean and the residuals may be hygroscopic. So, I only can suggest you to read the data sheet and follow the instructions by the solder paste supplier about the washing additives and parameters to use... Hi XPS analysispcb.com

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#61239

Mixing No-clean and water soluble processes | 25 February, 2010

We use the OM-5100 and wash it with relatively good results. Just dont let it sit longer than a few days before wash. We've used Zestron AC200 and A-250 in a batch cleaner set to 140 wash temp for 8-10 min @ the recommended concentrations. We have had cleanliness results done and everything passed with flying colors.

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