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I am working on a device that I want to work outdoors far up north (e.g. on a farm), maybe down to -40C. I read a lot about through-hole circuit boards being more resistant to environmental stress than surface mounts, including heat, but no mentions of cold. I am guessing that

  • because of the larger distance between parts they would be more resistant to condensate that might form and also
  • because through-hole parts have "legs" or pins, those act like springs when the board expands-contracts during the temperature fluctuations

Are those valid guesses? Are there any other advantages/disadvantages I am missing?

SM is cheaper than THM so I am trying to make a list of pros and cons before I decide whether to choose one or the other.

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    \$\begingroup\$ If it's going to be in an extreme environment, then I would highly suggest putting a conformal coating on it. Urethanes are very sturdy. \$\endgroup\$ – Aaron Feb 1 '20 at 4:17
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    \$\begingroup\$ I worked for a company in the 90's and early '00's that routinely did surface-mount boards that functioned down to -40. We didn't worry much about the mechanical effects of the cold. The circuit design itself presents some challenges -- expect failures at cold, and learn from them. \$\endgroup\$ – TimWescott Feb 1 '20 at 5:12
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    \$\begingroup\$ Have you considered microphonics? Many tiny surface-mount capacitors employ high dielectric constant ceramics that translate vibration-to-voltage. Larger through-hole parts may have high-Q mechanical resonances in the audio range too. \$\endgroup\$ – glen_geek Feb 1 '20 at 15:01

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