Author Topic: Heat sinking  (Read 924 times)

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Offline lorddamaxTopic starter

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Heat sinking
« on: October 01, 2010, 10:49:08 AM »
I know that transistors require heat sinking.

What about optocouplers? Relays? I cant find any reference saying they do or do not... and dont want to burn anything out making a guess! :)

Offline futmacl

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Re: Heat sinking
« Reply #1 on: October 01, 2010, 11:12:03 AM »
I know that transistors require heat sinking.

What about optocouplers? Relays? I cant find any reference saying they do or do not... and dont want to burn anything out making a guess! :)

Transistors only require heat sinks when dissipating significant amounts of heat (i.e., in power switching applications, especially close to their operational limits - or if used improperly). Most signal processing and many smaller power switching applications don't require heat management.

Most ICs also do not need this, although high-speed CPUs may (32 bits and beyond, few hundred MHz at least); voltage regulators and other power management ICs may need them too; so do power resistors if used for current limiting, but this is usually not something you should be attempting anyway.

Most other low-voltage, low-power electronic components don't require heat sinks. Properly operated optocouplers, relays, etc, are almost always fine without one.





Offline lorddamaxTopic starter

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Re: Heat sinking
« Reply #2 on: October 01, 2010, 11:17:35 AM »
My bad - I should have added "when soldering" to the title ;)

Do I need to heat sink a relay or optocoupler when soldering?

Offline futmacl

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Re: Heat sinking
« Reply #3 on: October 01, 2010, 12:08:11 PM »
Do I need to heat sink a relay or optocoupler when soldering?

You don't need to add heat sinks to much anything when soldering, but it sometimes helps and may improve component lifespan and performance - especially if you're just making your first steps with the soldering iron.

In general, devices in plastic housings (some relays, LEDs, switches), electrochemical components (batteries, electrolytic caps), and various electromechanical or mixed technology devices (optocouplers, MEMS accelerometers and gyroscopes, displays, potentiometers, sensors) are particularly vulnerable.

"Plain" semiconductors, resistors, film capacitors, etc, less so - but they also don't take prolonged heat too kindly, and their characteristics may change gradually.

Offline futmacl

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Re: Heat sinking
« Reply #4 on: October 01, 2010, 12:09:15 PM »
Do I need to heat sink a relay or optocoupler when soldering?

You don't need to add heat sinks to much anything when soldering, but it sometimes helps and may improve component lifespan and performance - especially if you're just making your first steps with the soldering iron.

In general, devices in plastic housings (some relays, LEDs, switches), electrochemical components (batteries, electrolytic caps), and various electromechanical or mixed technology devices (optocouplers, MEMS accelerometers and gyroscopes, displays, potentiometers, sensors) are particularly vulnerable.

"Plain" semiconductors, resistors, ceramic capacitors, etc, less so - but they also don't take prolonged heat too kindly, and their characteristics may change gradually.

 
« Last Edit: October 01, 2010, 08:39:38 PM by futmacl »

Offline z.s.tar.gz

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Re: Heat sinking
« Reply #5 on: October 01, 2010, 07:07:23 PM »
I know capacitors don't like too much heat because it boils the fluid inside them. Semiconductors don't like heat due to the microscopic whatchamajigers inside. Resistors seem to be pretty resilient.

I've never put a heatsink on anything while soldering because if it was meant to be soldered it can stand at least 5 seconds of continuous heat.

(this is all from personal experience)
Save yourself the typing. Just call me Zach.

Offline cyberfish

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Re: Heat sinking
« Reply #6 on: October 01, 2010, 10:58:42 PM »
And if you are doing reflow soldering, you can't use a heatsink, so all the components (well, 99%) have to be rated for 240C+ (for lead free reflow).

 


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