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Date: | Fri, 2 Jun 2017 13:27:03 +0000 |
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We have a power-control board designed for Pb-Free processing that has many surface-mount components, with parts mounted only on the top side. Several ICs and transistors are leadless (very low-profile) parts, some with thermal solder pads on the package bottom. I am requesting their no-clean solder-paste processing because of my fear of their inability to adequately clean a water-clean flux from under these low-profile parts. I fear a chemistry experiment, since these boards will be placed in an outdoor environment with uncontrolled temperature and humidity.
Question #1: Are my fears about properly cleaning water-clean flux from under low-profile parts justified?
This board has about 20 through-hole capacitors and 5 connectors (100 pins, total). Our normal assembly house has a water-clean flux Pb-Free wave-solder machine that could be used as a second pass process to add the through-hole parts at a lower cost, possibly reducing the hand-add labor charges. The wave-solder process would be followed by a cleaning in their new board-wash system. They do not currently have a method to determine board cleanliness after the cleaning process. I fear that the nasty flux may flow through holes in the board, finding ways under the low-profile SMD parts on the top of the board, creating another chemistry experiment.
Question #2: Are my fears about water-clean flux from the wave process flowing to the top side of the board, hiding under the low-profile parts, and performing long-term chemistry experiments valid?
Question #3: Should I trust a board-washing process that doesn’t have a way to verify the quality of the cleaning?
Question #4: Are there suggestions to alternative processing methods that I should consider?
Thanks,
Carl
Carl B. Van Wormer, P.E., AE7GD
Senior Hardware Engineer
Cipher Engineering LLC
21195 NW Evergreen Pkwy Ste 209
Hillsboro, OR 97124-7167
503-617-7447x303
[log in to unmask]<mailto:[log in to unmask]> http://cipherengineering.com<http://cipherengineering.com/>
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