parth_155
Posts: 33
Joined: Tue Aug 18, 2020 11:26 pm

Compute Module 4 Doesn't fit properly one side.

Tue Apr 20, 2021 8:47 pm

Hello,
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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dp11
Raspberry Pi Engineer & Forum Moderator
Raspberry Pi Engineer & Forum Moderator
Posts: 487
Joined: Thu Dec 29, 2011 5:46 pm

Re: Compute Module 4 Doesn't fit properly one side.

Tue Apr 20, 2021 9:24 pm

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.

aBUGSworstnightmare
Posts: 2811
Joined: Tue Jun 30, 2015 1:35 pm

Re: Compute Module 4 Doesn't fit properly one side.

Wed Apr 21, 2021 5:24 am

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).

parth_155
Posts: 33
Joined: Tue Aug 18, 2020 11:26 pm

Re: Compute Module 4 Doesn't fit properly one side.

Wed Apr 21, 2021 2:28 pm

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 will ask assembly house about temperature profile used.
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.

aBUGSworstnightmare wrote:
Wed Apr 21, 2021 5:24 am
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).
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.

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