After a CAD session during which vibration isolating versions of the probe board mounting areas were designed, I looked at the miserable board to see if I could determine the cause of failure. Well, it turns out I had a cold solder joint for the GND connection to the power and battery management daughterboard.
This is the solder joint in question, in the PCB hole pointed to by the screwdriver:
I did not allow for enough heating when applying the solder, and must have done a poor job of inspecting the board because, in hindsight, the joint in the photo looks pretty bad -- it's obviously just a bleb of solder sitting there.
In the same orientation, this is the hole in the PCB layout. You can see that it is properly joined to the ground plane by thermals, to alleviate exactly this problem:
So we're back on track -- but, if I can, I will change to the vibration isolated version of my mounting, just in case. If it's not too much more trouble, it should be really helpful.
This is the solder joint in question, in the PCB hole pointed to by the screwdriver:
I did not allow for enough heating when applying the solder, and must have done a poor job of inspecting the board because, in hindsight, the joint in the photo looks pretty bad -- it's obviously just a bleb of solder sitting there.
In the same orientation, this is the hole in the PCB layout. You can see that it is properly joined to the ground plane by thermals, to alleviate exactly this problem:
So we're back on track -- but, if I can, I will change to the vibration isolated version of my mounting, just in case. If it's not too much more trouble, it should be really helpful.
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