CM4 adaptor board and heat sink issue
# │forumm
mahtin_w6lhi
05/06/2023, 10:06 PMI’m mounting #CM4’s onto the adapter board and I’m also adding a #heatsink. It’s this one: “Dedicated Aluminum Heatsink for Raspberry Pi Compute Module 4 (CM4), Notched for Antenna” at https://a.co/d/ctovFnS
I’m seeing an issue with the screw holding down the CM4 and heat sink. There’s no circular pad on the holes do a screw will impinge with components. I’ve removed the screws and I think I’ll need M2.5 plastic washers before finishing to mounting. Anyone else with this issue?
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DhanOS (Daniel Kukiela)
05/06/2023, 10:10 PMYes, this is a known limitation. The future revision of the adapter board should make more space there
DhanOS (Daniel Kukiela)
05/06/2023, 10:10 PMYou also don't need to screw the heatsinks to the adapter board. Actually people mostly don't do this
DhanOS (Daniel Kukiela)
05/06/2023, 10:11 PMYou're fine with screwing the heatsink to the module only and then the connectors are more than enough to keep the module in the adapter board
DhanOS (Daniel Kukiela)
05/06/2023, 10:12 PMThe only exception would be if you want to mount your TPi2 board in a place with a lot of vibrations, like in a car. Otherwise it's more than fine to use just the connectors to keep the module on the adapter board
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mahtin_w6lhi
05/07/2023, 12:26 AMThanks for the response! Makes sense.
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RanchoHam
05/08/2023, 7:22 PMI noticed the interference also. It's a shame that the clearance wasn't made in the original artwork since the hole is there and there is no pressing reason to crowd the layout. When I was laying out PWBs (Printed Wiring Boards) for a living, the first thing we did was put in the keep-out zones (big ones at that) around the mechanical hardware features. Only if pressed would we shrink the keep-outs to the bare minimum clearance to the hardware being used. (I notice the screw head seems to be out-of-poportion to a normal screw. Perhaps it is just the small major diameter of the screw compared to the size required for a Philips screw.) As to vibration, I plan on using both my Turing Pi V1 & V2 in my motorhome, so I will be using a nylon screw in the hole with the interference.
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DhanOS (Daniel Kukiela)
05/08/2023, 7:31 PMAs I said above, I would not risk putting a strain there, especially in the vibrating environment. Remaining 3 screws will do the job well-enough in my opinion.
DhanOS (Daniel Kukiela)
05/08/2023, 7:32 PMActually, one thing you could do would be to use a washer small enough to not put any pressure on the D2, or maybe even cut it accordingly. It's also have to be thicker than the electronics components so the head screws do not touch these elemenets
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RanchoHam
05/08/2023, 9:31 PMYou @DhanOS (Daniel Kukiela) are most likely right, but I am an old EE used to Mil-STD shock and vibration standards. I can remember an innocuous looking CK06 capacitor breaking off under vibration. Thereafter we had to put a blob of epoxy resign (we called it polymerized snot) around every CK06 capacitor on all the boards in the system...a LOT of capacitors! Cheers.
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DhanOS (Daniel Kukiela)
05/08/2023, 9:32 PMHah, I like stories like this one. Thanks for sharing 😄
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aurelienk
05/20/2023, 6:11 AMhello @mahtin_w6lhi
Asked myself the exact same question when I mounted mine yesterday.
aurelienk
05/20/2023, 6:18 AMI don't understand this affirmation : the module is not plugged in the adapter, it won't hold unless it is in horizontal state, and no tiny shock on the motherboard happens.
aurelienk
05/20/2023, 6:42 AMOK, after manipulations, yes it plugs in, sorry these things are so tiny, i fear breaking them ^^
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DhanOS (Daniel Kukiela)
05/20/2023, 4:39 PMYeah, you need to use a bit of force until it "clicks" in 🙂
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