Electronics > Beginners
LED driver at -40degc ambient
ocset:
Hello,
We have an 40W offline LED driver which uses no electrolytic capacitors...only ceramic ones.
Also, it uses only sequence switched linear regulators, -no SMPS.
It is only surface mount components.
Optocouplers, resistors, caps, diodes, FETs, SFH5711 light sensor, MCP9701 temp sensor, MCP6001 opamp, BZX84C-XX zeners.
Do you think we will have problems at -40degC?
The PCB sits on a rubbery thermal pad which is on a heatsink
We are getting it in the oven at -40degc, but wonder if there are any long term effects.
The product is totally enclosed..no vent holes....a rubbery gasket makes the seal between the optic and the heatsink
ArthurDent:
The question is will it work at -40 degf :-DD
ArthurDent:
Seriously I would wonder if a through hole design might be better. I'd wonder if parts and circuit board would expand and contract at different rates and perhaps break ceramic caps or component solder bonds with the board. I would think that leaded components would allow some give that you might not get with surface mount. Might be worth looking into for long life.
One place I worked in winter (Mount Washington, New Hampshire) would get temps approaching the limits you're using. When the rebar reinforced thick concrete walls approached these temps we would hear load noises like gun shots as the rebar and concrete contracted at different rates and 'readjusted'.
mdszy:
--- Quote from: ArthurDent on August 20, 2018, 04:59:23 pm ---Seriously I would wonder if a through hole design might be better. I'd wonder if parts and circuit board would expand and contract at different rates and perhaps break ceramic caps or component solder bonds with the board. I would think that leaded components would allow some give that you might not get with surface mount. Might be worth looking into for long life.
One place I worked in winter (Mount Washington, New Hampshire) would get temps approaching the limits you're using. When the rebar reinforced thick concrete walls approached these temps we would hear load noises like gun shots as the rebar and concrete contracted at different rates and 'readjusted'.
--- End quote ---
I feel like you'd also have to worry about the solder joints cracking at that point.
Ian.M:
Yep, ROHS Sn based solders can turn into non-conductive grey powder at very low temperatures. See https://en.wikipedia.org/wiki/Tin_pest
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