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Water Soluble Paste

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#36386

Water Soluble Paste | 30 August, 2005

EdgeTech SMT Tech here. I was questioning the process our Engineers are using concerning Water Soluble solder paste. I have no experience with this paste. I was wondering what need so be done differently when using this paste. As far as I know the only thing they are doing is sending completed boards through a dish washer using tap water... Can this be right? I would think you would use distilled water. Any help would be helpful. Thanks

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Rob

#36391

Water Soluble Paste | 30 August, 2005

Tap water will leave residues, whereas de-mineralised/de-ionized shouldn't.

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PWH

#36394

Water Soluble Paste | 30 August, 2005

Agreed - D.I. a must. Also, operators will have to pay attention to lesser stencil life than no-clean paste. Product specs. might say the stencil life is similar but experience has showed us that no-clean last much longer and rolls for a longer time. Additionally, NC doesn't clog up stencil aps. as readily for the products we use. So... periodic ultrasonic wash in DI for stencils depending on frequency of use.

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Rob

#36396

Water Soluble Paste | 30 August, 2005

Cheers - didn't notice the rolling difference - our printers kneed the paste regularly so keep it workable.

You learn something every day.

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#36420

Water Soluble Paste | 31 August, 2005

Thanks for the input guys. I was thinking the minerals found in tap water may cause the components to short/malfunction

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PWH

#36426

Water Soluble Paste | 31 August, 2005

One more thing to think about - if placing BGA's using water sol., you must ensure they are clean and dry beneath the component post wash. A few ways to do this. Simplest is to use DI from low pressurized nozzle and hand wash them at different attack angles then; dry them with compressed air nozzle (low pressure). Storing finished boards on edge will also help if any water was not blown out.

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