I have some interesting problems on my hands that some of you may know the answers to. I am currently wave soldering a through hole connector to a rigidized flexible circuit. This is a compliant pin connector that is supposed to be pressed into a hardboard and not wave soldered at all. Because our flex is only .050" thick, we had to open the through-hole and solder it. Oh, and we have to use no-clean flux as well (my first experience with it). This leaves me two issues that are currently happening:
1. I am getting bridging between at least 2 of the pins on 75% of every trailing edge. The pitch between the closest pin is .055" and my stick through is .025". My pads are .038" so I tried adding solder thieves that were .050" behind them. Before I added the thieves, we were getting 100% bridging on every connector. My thoughts were to make larger thieves or possibly reduce the stick through by increasing my rigidizer (FR4) thickness. Any design or process ideas?
2. Because it's flex, I also have to use carrier pallets. Due to a feature on the connector, the opening in the pallet comes extremely close to the closest pad (.020" on one side) and I'm getting voids only along that edge. We currently spray flux and it appears there is proper distribution of the flux, but I'm not sure what this close pallet feature is doing to those pads during (IR) preheat and in the solder itself. Is this shadowing? Is the flux burning off or is this pallet feature robbing heat from these pads? I can't clearance the connector any further. Any help is appreciated, I'm a bit of a rookie. Thank you in advance!
Dave
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