inches
Posts: 16
Joined: Tue May 03, 2016 7:55 pm

Soldering under the CM3

Fri Apr 28, 2017 1:26 am

Is it advisable to have solder holes beneath where the CM3 is mounted?

For example, I want to solder some wires to some holes on the space below the module so that I don't waste all that space.
http://imgur.com/HGrNmBc

I'm using a 1473149 SODIMM connector which states the module height (the center of the compute board) is at 3.4mm.
http://imgur.com/glR8M2N

The datasheet for the CM says max component height on the back of the CM is 1.5mm. Board thickness is 1.0mm.

Does that mean I take 3.4 module height - half the PCB thickness of .5mm minus max object height 1.5mm and get 1.4mm?

Regardless of how the math ends up, I still would like to hear generally if it's advisable.
Last edited by inches on Fri Apr 28, 2017 4:26 am, edited 1 time in total.

W. H. Heydt
Posts: 10563
Joined: Fri Mar 09, 2012 7:36 pm
Location: Vallejo, CA (US)

Re: Soldering under the CM3

Fri Apr 28, 2017 2:22 am

inches wrote: The datasheet for the CM says max component height on the back of the CM is 1.5mm. Board thickness is 1.0mm.

Does that mean I take 3.4 module height - half the PCB thickness of .5mm minus max object height 1.5mm and get 1.6mm?
1.5mm + 0.5mm = 2.0mm. You have, therefore, 1.4mm clearance. But that is only in part of the area. In most areas you will have about 2.9mm (3.4mm - 0.5mm).

FrozenNick
Posts: 24
Joined: Tue Apr 18, 2017 3:51 am

Re: Soldering under the CM3

Fri Jul 28, 2017 7:53 am

as long as sodimm connector height is tall enough so that the compute module does not touch the pins, i don't see any reason why you can't :)

User avatar
aTao
Posts: 1086
Joined: Wed Dec 12, 2012 10:41 am
Location: Howlin Eigg

Re: Soldering under the CM3

Fri Jul 28, 2017 8:11 am

For a 1 off, or bespoke build, then its ok, provided you check the height of the wire stub (if poked though from other side) or wire height (if poike through from top side) after soldering.
In a production situation this would be an expensive nuisance.

You might test your idea by assembling one and dabbing ink on the wire, inset CM extract it and inspect for ink transfer.
>)))'><'(((<

JesperBKK
Posts: 6
Joined: Mon Aug 07, 2017 6:09 pm

Re: Soldering under the CM3

Mon Aug 07, 2017 6:43 pm

No problem,

The only drawback (apart from the height contraint) is that it's very difficult to debug / get an oscilloscope probe in under it. I have decoupling caps under the CM3 on my board.


Jesper

Return to “Compute Module”