Questions tagged [thermal]

Relating to temperature rise, the flow of heat, or cooling of components

Excepting superconductors, current flow through any conductor results in energy being converted to heat within that conductor. This results in a temperature rise within the conductor. As all materials have a maximum safe operating temperature, failure to properly dissipate this heat can result in failure of components.

Heat flows from hot objects to cooler ones, by the laws of thermodynamics. As such, it is possible to assist heat dissipation by providing a low-impedance thermal connection between the component generating heat and some other material known as a heat sink. Eventually, the heat sink (or sinks) must dissipate their heat to some other surrounding substance, typically the atmosphere of the Earth.

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Optimize heat sink design - connect cooling pad on PCB backside by vias

In one of my current projects I'm using an MC7805 in a D2PAK package to generate my logic supply of 5 V from an available 24 VDC supply. The current required by the circuit is 250 mA. This results in a dissipated power of the MC7805 of: \$P=(24\…
KarlKarlsom
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How do I determine the area of copper needed on a PCB to provide adequate heatsinking for a power SMD MOSFET?

I am planning to use the IRFR5305PBF Power MOSFET (http://www.irf.com/product-info/datasheets/data/irfr5305pbf.pdf) to switch on a load. I have determined that I need an external heatsink with Rthsa < 29 C/W. How would I go about determining the…
dla59
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Why aren't CPUs cooled from below as well as above?

The transistory bits of an integrated circuit are approximately in the centre of the (plastic or ceramic) package. They sometimes get hot, and we cool them by affixing a heat sink to one side. Sometimes we just blow air over them with a fan. Some…
Paul Uszak
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How to solder a 70 °C (158 °F) thermal / temperature fuse

For my DMX project (schematics is not important), I soldered this temperature fuse which has just two leads (see picture below). The fuse doesn't work (meaning it does not conduct electricity) ... which of course is logical since my soldering…
Michel Keijzers
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TO-92 not getting hot enough

I am controlling a DC fan by an AVR MCU and I am curious about the thermal characteristics of a 2N3904 NPN transistor over which the fan is connected. Reading the transistor's datasheet, I find the following values: $$ R_{\theta J-A} = 200\text{…
Nikola Malešević
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How do filament LED bulbs work, looking very similar to incandescent bulbs?

Filament LED bulbs use very narrow strips containing the LED, which look similar to filaments of an old incandescent bulb: They look like a normal bulb with large "old-style" coal filaments, and are of about the same size and shape as the common…
Volker Siegel
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Why do 0 dB attenuators exist?

I am reading this paper : Upgrade of a low-temperature scanning tunneling microscope for electron-spin resonance and found that for thermalization, they use 0 dB attenuators. Page 6: Having the finite cooling budget of our cryostat in mind, and…
Blackwidow
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Does the paint colour matter on a heat sink?

Heat leaves a heat sink via conduction, convection and radiation. I was taught that black surfaces are best at radiating heat and correspondingly a lot of heat sinks are black. But they also have fins for convection. And large heat sinks have…
Paul Uszak
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Entire Perimeter of FPGA Getting Hot - Why?

I have a commercially-produced board with an Altera EPF10K30-series FPGA. There is an abnormally high current draw on the board. Where +5V should be present, there is only +2.6V. When comparing thermal images of a known good, working board to the…
jfriend
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Why are electrically insulating heatsinks so rare? Is it just cost?

Edit: It seems my initial question (Why are there no insulating heatsinks?) was based on a false premise, and there are in fact insulating heatsinks--I just wasn't able to find them with a cursory search. So instead, I'm changing this to ask about…
Hearth
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SMD IC mounted upside-down inside a drill hole for extreme low-profile requirements

I don't know if the title is descriptive enough, but I came across this PCB and could stop to wonder about its brilliant design. It is an aftermarket trigger controller for an airsoft gun that works linear Hall sensors, such that you may glue tiny…
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Is a thermally conductive pad always useful between TO220 and heat-sink?

I have a doubt about heat-sinking that I could not solve by surfing the Web. My doubt arised when mounting a TO220 package on its heat-sink using these dirty cheap pads, but actually it has quite a general scope. There are a lot of articles out…
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How much of the power drawn by a chip turns into heat?

If I have a circuit with a computing chip drawing 1W, how much of that gets turned into heat? EDIT: I mean turned into heat 1. straight away (not in 1000 years) and 2. within the vicinity of the device, typically in the same room My understanding is…
asac
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What is reasoning behind the common wisdom of limiting the temperature rise of a PCB trace to 5/10/20°C?

When deciding on the trace thickness required to carry a certain amount of current on a PCB, the answer depends on how much temperature rise you are willing to accept. This leads the designer into the difficult situation of trying to decide how much…
jvok
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Can an infrared thermometer (IR gun) be used to measure the ambient room temperature?

I know the principle of an IR thermometer, but have one question regarding that are as below. As an IR thermometer senses the radiated IR waves from external bodies coming in their field of view and gives surface temperature reading, can we point…
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