Electronics > Beginners
SMT vs Thru hole: Thermal/vibration application?
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RogerThat:
Hi,

Trying to understand when there is a good time to use thru hole rather than SMT part.
When googling the above I find alot of copy-past information 'Use thru hole when there is a lot vibration or thermal cycling'.
But, there is no info what 'a lot' is?

Seeing that more or less all accelerometers are SMT I guess the vibration argument goes away?

Looking at other products like bike computers, smart adventure watches, etc that are subject to both vibration/shocks and thermal cycling it's surface mount all the way. Maybe due to size?

The only reason for thru hole that I found is if the component is physically large/heavy (like big inductors/capacitors).

If I build a IoT which will be placed outdoors(+60c in summer to -30c in winter, also daily cycling) and that I want to work for years on end, is SMT ok or should I go for thru hole?
Jeroen3:

--- Quote from: RogerThat on January 28, 2019, 08:54:01 am ---Seeing that more or less all accelerometers are SMT I guess the vibration argument goes away?

Looking at other products like bike computers, smart adventure watches, etc that are subject to both vibration/shocks and thermal cycling it's surface mount all the way. Maybe due to size?

--- End quote ---
Accelerometers still break internally when the forces applied are too high. Not only the duration, also amplitude and frequency matter.
Both smart watches and bike computers are not special applications regarding vibrations.
Engine mounted sensors en equipment, rockets, airplanes, tanks are heavy vibration environments.

The reason to go for through hole is that some components are only available in tht, are cheaper in tht or can do more power in tht.

If you want more reliability, look into coating or potting. That keeps moisture out.
hsn93:
i did not read this but two days ago i stepped by it and now i remembered it after seeing your question.


https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20100029736.pdf
mvs:

--- Quote from: RogerThat on January 28, 2019, 08:54:01 am ---If I build a IoT which will be placed outdoors(+60c in summer to -30c in winter, also daily cycling) and that I want to work for years on end, is SMT ok or should I go for thru hole?

--- End quote ---
Modern automotive electronics has excessive use of SMT and the conditions are even more harsh. If BOM costs are not a major concern for your application, look at automotive ( AEC-Qxxx qualified) or industrial grade parts. They may have some additional features like soft termination (MLCC caps, chip resistors) to prevent cracks.
max_torque:
TH vs SMC used to favour TH when the SMC components were basically the TH ones with the leads cut off or bent differently.

Today, however, most SMC componentry is optimised for it's package and usually a lot smaller and lighter than the TH stuff, and hence is suited to high vibration environments. The exceptions are high current or high temperature components, where they have to be physically large, and hence heavy, and hence require a stronger mechanical restraint.  Increasingly however, that is simply provided with larger, better designed footprints with a larger surface area.


In really high vibration environments, the devices will need to be potted, and that brings a whole other load of constraints and potential issues
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