Inside of an automotive ECU I noticed that all three crystals are mounted about 1/4" above the PCB. What is the advantage of doing this versus mounting the case flush with the board? This seems like it could lead to vibration cracking the solder joints over time. Is there a thermal issue – crystals don't really dissipate much heat? Manufacturing constraint? Some of the capacitors are mounted in a similar way, although this looks more normal to me.
Electronic – Why would one mount components above the PCB
automotivecrystalpcbpcb-assembly
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Best Answer
The bent leads set the component height during wave solder. It does four things:
During wave soldering:
After soldering:
The extra lead helps prevent cracking at the lead/component junction in high-vibration environments by spreading the flex over the lead, rather than concentrating flex at the component itself.