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I am mounting a PCB, which deals with currents up to 5A and essentially switches down 60V to 12V and 5V, on a bicycle frame. I have four holes, one at each corner, that are padded with copper traces to the ground plane. Is it ok to fix the pcb to the frame by screwing the pcb through these holes directly on the metal of the frame or can this lead to problems? Thank you for your help!

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marked as duplicate by Dmitry Grigoryev, Wesley Lee, uint128_t, Voltage Spike, DoxyLover Mar 21 '17 at 6:56

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  • \$\begingroup\$ Fixing the bare PCB on your bike won't create problems, but riding your bike will. \$\endgroup\$ – Dmitry Grigoryev Mar 17 '17 at 11:41
  • \$\begingroup\$ Considering you have already asked How to mount electronics on a vehicle chassis safely, do you mind explaining what aspects specifically weren't covered by previous answers? Otherwise, you risk getting the same wisdom about vibration effects and harsh environment that you already got. \$\endgroup\$ – Dmitry Grigoryev Mar 17 '17 at 11:49
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    \$\begingroup\$ Thank you, in my previous question I was just wondering about industry standards. Here I wanted to ask about the electrical implications of passing screws through these holes to a metallic conducting structure, if that would have any effect on the functioning of the pcb. I also am using anti vibration dampes between the pcb and the structure. \$\endgroup\$ – Eliott W Mar 17 '17 at 15:40
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It is usually OK to screw through those holes when mounting a PCB in a regular appliance. A bike is going to be a bit tougher than that.

  • Don't apply too much torque. Screw holes which are surrounded by a ring of vias can take more torque than one which is just a plated through hole with a big pad.
  • Think about where you are screwing it on the bike frame. You might be surprised how much a bike frame flexes when it's being ridden. If the screws move even 1mm relative to each other, it's going to crack the PCB quite fast.
  • Think about vibration. If the bike is being ridden outside of a velodrome, the vibration could damage the solder joints on larger/heavier parts. Rubber grommets or standoffs would transmit less vibration to the board than if you just screw it on.
  • Think about dirt and road grime, especially road salt. You might want to enclose the PCB, in which case you'd be better off bolting the PCB to the inside of the enclosure, and the enclosure to the bike.

If it was me, I'd probably fix the PCB inside a diecast box with rubber/flexible mounts, then bolt that to the bike.

Also, your question was about mounting so I've only discussed mounting, but the vibration thing is a big potential problem. Mounting with rubber mounts will reduce the vibration reaching the board, but depending on the speed/surface the bike is being ridden at/on and the components used on the PCB it may not be enough. Also consider component selection, securing large components with glue, encapsulating or potting the board, or just living with high failure rates.

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  • \$\begingroup\$ Thank you for your time! I am gonna use anti vibration dampers between the pcb and the frame, and am thinking about potting the pcb with epoxy. But the actual connection established between the ground of the board and the conducting metal structure of the bike will not be a problem? \$\endgroup\$ – Eliott W Mar 17 '17 at 15:44

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