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Date: | Thu, 31 Jul 2014 19:52:15 -0400 |
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do you know for sure your CM use DI? not city water?
On Jul 31, 2014, at 10:38 AM, Nutting, Phil wrote:
> Over the past years we have had relays, optos and pots fail due to
> corrosion being found inside the parts after post soldering wash.
> The quick solutions have been to use other manufacturer's parts or
> install after wash with hand solder "no-clean" cored flux. One
> manufacturer said it was because of halides in the flux. Our
> primary CM's and our flux contains halides, but we haven't seen as
> many failures with in-house processed PTH boards as with CM built
> boards. Recent pot failures have been explained by component
> manufacturers as too much wash pressure or bad flow direction from
> the wash jets. Opto failures were similarly diagnosed.
>
> Our in-house process, all PTH, is foam flux with OA flux, wave
> solder with 63/37 or SC995e followed by a closed loop DI wash with
> no chemicals. This has been a great process since 2006 when we
> switched from a no-clean foam flux, 63/37 wave and terpene/alcohol
> wash to our listed system above.
>
> We do not dictate flux/wash process to our CMs, but we do specify
> cleanliness to J-STD-001 C-22 using the 1.56 μgm / cm2 NaCl
> equivalent contamination value. Forcing the CM to change fluxes
> for our product met great resistance and added cost so no change in
> flux was made.
>
> Our business is high voltage from 30 kV to 240 kV so clean with NO
> residue is very important. The DI wash has provided that in-house.
>
> We are using different CMs going forward, but not necessarily for
> this reason.
>
> Is this a problem unique to us or do other suffer from similar
> problems?
>
> Phil Nutting | HVP Development Engineer | Excelitas
> Technologies Corp
>
> Lab: +1 978.224.4332 | Office: +1 978.224.4152
> 35 Congress St, Salem, MA 01970 USA
> [log in to unmask]<mailto:[log in to unmask]>
> www.excelitas.com<http://www.excelitas.com/>
>
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