I've been using selective soldering process for about 18 months. The major problem concerns tight spacing- the distance between the SMT pads to be masked and the thru hole leads to be wave soldered should be no less than 0.150 inches. Keep the walls in the pallet as thick as possible- if less than 0.040 thick we have had problems with the pallet material breaking down and permitting solder flooding. Also keep the total pallet thickness below 8 mm total thickness or the pallet will run too deep in the wave- believe me this is a problem.
| | | Good Morning everyone. Per repeated suggestions I have been reading back issues of SMT and Circuits Assembly magazines. I have just read an article concerning selective wave soldering which I understand is to be used when active SMTcomponents are are reflowed onto both sides of the board. The board is then mounted in a fixture which covers the SMT components and allows the wave to flow the through hole parts. Only days later I was requested to investigate this process for a new, very dense, design. I am looking for any information reguarding the design parameters for these "Pallets", materials, clearances, and specifcally any vendors or fab shops with experience in design or fabrication. | | | On a completely different subject, I thank all of you who responded or e-mailed me concerning my question about cleaning ceramic substrates. I am now in the process of collecting a large amount of mostly contradictory information on the subject. I'll revisit this when I have some valid test results | | | Thanks for any help you can give. | | | Gary | | Gary, | | Check with some of the larger SMT fixture makers | | such as EMC Global Technologies 215-340-0650 or | | SP Precision International 503-357-9228. | | They should be able to help you iron out a design, | | or do a full turn key job for you. | | Steve A | |
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