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White residues

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White residues | 25 May, 2008

Dear All,

I would like to take your opinion about the result that we have faced after cleaning the PC assemblies in a cleaning machine (Miele Dishwasher) with the cleaning detergent Qualitek Everkleen 1005. We use DI water for cleaning purpose in the machine. The water temperature was 140 Degrees F, and the concentration of the detergent was changed between 5-10% for trials.

We have seen white residues type formations, almost all over the solder joints which has formed by solder paste reflow. Strange thing is that there was no white residues formed on wave solder or hand solder joints. So those white residues should be a chemical interaction between the flux in the solder paste, detergent and DI water.

We have changed and tried the solder paste from Multicore, Alpha and Qualitek, the residue concentration has changed, lesser with Qualitek may be but still there.

I will be appreciated any comments that you can send me for helping me to get rid of those white residues and find a solution to have shiny solder joints after cleaning.

Best regards,

Necdet Ozyonum

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White residues | 26 May, 2008

It's possible that the flux residues from the solder paste used in your SMT process is not compatible with your water wash process. For instance, some no-clean fluxes leave resudues that are not water washable. When these residues are washed, they develop a milky white coating on the solder connection.

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White residues | 26 May, 2008

Hi Mr. Necdet Ozyonum,

Recently we did have same kind of problems when we use lead free reflow profile for leaded solder paste (AIM WS-483). There where solder resist lacks, we found white residue after aqueous cleaning. Not in the solder joints but in the PCB between pads. Fine pitch IC packages were most common places to found white residue. We found that only way to get this white residue off the board is mechanical brush or bath in the ultra sonic cleaner with the cleaning detergent (5% Aimterge).

Solution for this problem was to lower reflow profile peak temperature to normal level for leaded solder paste.

Hope this helps :)


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