We did few prototypes and everything was working fine. We just received our production units and CM4 doesn't fit in one of the side in most of the boards (HDMI side). The connectors looks like genuine Hirose connectors. We used same PCB manufacturing and assembly house that we used for prototypes. The only difference we made is now our assembly is lead free. I am really confused because one side fits nicely in all of the boards and I can even hear the click. Second side I can fit but have to go really hard upto a point I feel like CM4 bends and will break BGA solder pads. What could be the issue?
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It looks as though one of the connectors hasn't centered on the pads, may be with the lead free solder the temperature isn't quite warm enough to let surface tension centre the connector.
Have you checked the CM4's in use? There is also the risk that their connector are 'missaligned' (means slightly shifted or rotated (there was at least one report of this).
I will ask assembly house about temperature profile used.dp11 wrote: It looks as though one of the connectors hasn't centered on the pads, may be with the lead free solder the temperature isn't quite warm enough to let surface tension centre the connector.
I was under impression that they used too high temperature since its lead free assembly and the connectors expanded little bit due to excessive heat.
We tried few different batches of CM4 as well. Looks like Rotation is not issue, because these connectors are symmetrical and I couldn't insert same side with CM4 180 degree rotated.