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SMT electronics assembly manufacturing forum.


Finding a white strand on fine pitch components

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#59528

Finding a white strand on fine pitch components | 13 August, 2009

Hello Everyone, I have noticed that everytime that we have ran a PCB with fine pitch components (or even 0603s), there are little white strands on the leads or on top of the components. It occurs on both lead and lead free solder. We usually soak our boards for 10+ minutes and then wash it. Does anyone know what and why this occurs?

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#59533

Finding a white strand on fine pitch components | 14 August, 2009

So, in order to understand your issue better, please * Tell us more about your process [eg, process flow, machine setting, measured temperatures, etc] * Tell us more about your materials [eg, board, paste, etc] * Describe the extent of the problem [eg, multiple, single assembly; multiple, single production line; whole, part of the assembly, etc] * Tell us when in your process that the problem occurs * Let us know the composition of the material of the 'white strand' * Post a picture

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#59576

Finding a white strand on fine pitch components | 20 August, 2009

When I've seen white strands in the solder on SMT boards, it's been fibers from stencil wipes that stuck to the stencil, then transfered to the board when it was printed. I'm not sure why this would only happen with fine pitch components though.

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#59698

Finding a white strand on fine pitch components | 28 August, 2009

Do you clean the stencil manually or using the automated under-stencil cleaner on your Printer (recommended)?

1. Ensure that stencil wipes are lint-free and soaked sufficiently with solvent before use.

2. If your printer supports automated cleaning, you should use a vacuum swipe after solvent clean, especially due to presence of finepitch appertures.

3. If you adopt the manual cleaning method, you could use an external air jet to remove cleaning wipe residue if entrapped in finepitch appertures, by supporting these using a solvent soaked wipe held at opposite side.

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