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Author Topic: how to use heatsink  (Read 5943 times)

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Offline fugrammerTopic starter

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how to use heatsink
« on: October 30, 2006, 08:27:49 PM »
hi, i know that this can be simpe for others but how do i stick heatsink to the IC chip? btw, what is the heatsink compound for?

Thanks in advance.

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Re: how to use heatsink
« Reply #1 on: October 30, 2006, 09:02:25 PM »
what type of chip? how many pins?

IC's, such as a voltage regulator or MOSFET, usually have a hole at the top where you can screw a heatsink right on it.

You can also use what is called thermal glue, which is basically a glue with low thermal resistance. This is the heatsink compound you mentioned.

The screw method is better, if you can get a nice tight connection between surfaces - only use thermal glue if you cant use screws (its a little messy and reduces heat transfer a little).

Offline sdk32285

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Re: how to use heatsink
« Reply #2 on: October 30, 2006, 10:49:07 PM »
the thermal compound is to increase thermal-conductivity between the heat-sink and the IC. the thermal compound does not dry. if you need a permanent attachment you can use thermal epoxy (cheap brands= cheap product=bad thermal conductivity). the downside to epoxy is that it is permanent and you have a good chance of damaging the IC when trying to remove it.
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Offline fugrammerTopic starter

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Re: how to use heatsink
« Reply #3 on: October 31, 2006, 07:44:41 AM »
i will be using the heatsink on SN754410, dip. If i want to temporary stick the heatsink to the chip, can heatsink compound do that job?

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Re: how to use heatsink
« Reply #4 on: October 31, 2006, 09:51:45 AM »
Yeap, it will work.

The datasheet says 1A output current capability with 2075mW dissipation, and also thermal shutdown.

How many amps do you plan to draw, and at what voltage?

Offline fugrammerTopic starter

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Re: how to use heatsink
« Reply #5 on: October 31, 2006, 10:41:07 PM »
Around 12v at 550ma. The book that i had stated i shld use a heatsink if i plan to draw more than 300+ ma.

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Re: how to use heatsink
« Reply #6 on: November 01, 2006, 08:36:12 AM »
Hmmm so 12V * 550mA is 6.6W (plus inefficiencies). The IC can only handle 2W. You need way more than a heatsink . . .

What you might want to do is put 4 of the IC's in parallel, reduce the voltage, or use a different driver . . .

Offline fugrammerTopic starter

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Re: how to use heatsink
« Reply #7 on: November 02, 2006, 12:23:44 AM »
is there any chip that you can recommend me??? actually i like to use the L298(i think) chip, but can its pin fit into the PCB prototyping board? or is there any way to fit it in?

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Re: how to use heatsink
« Reply #8 on: November 02, 2006, 08:38:37 AM »
Can you explain your application? What device are you driving? If it is a motor, do you need it to rotate both directions or just one?

Offline fugrammerTopic starter

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Re: how to use heatsink
« Reply #9 on: November 02, 2006, 07:20:44 PM »
Yar, it is a motor. Both direction is required. If possible, the chip could haf a break feature. 

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Re: how to use heatsink
« Reply #10 on: November 03, 2006, 07:58:23 AM »
Ok so what you need is a motor driver, such as this one
http://www.dimensionengineering.com/SyRen10.htm

See the electronics parts list page for motor drivers/controllers.

Offline pomprocker

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Re: how to use heatsink
« Reply #11 on: November 27, 2008, 10:07:54 PM »
I bought a couple heatsinks off sparkfun.com for my TO-220 packaged voltage regulators. Do I need to use special nuts/bolts to attach it? and do I need to use thermal grease?


Also can anyone explain to me how a heatsink on a voltage regulator benefits the circuit.
« Last Edit: November 27, 2008, 10:08:51 PM by pomprocker »

Offline SciTech02

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Re: how to use heatsink
« Reply #12 on: November 28, 2008, 12:08:40 AM »
Also can anyone explain to me how a heatsink on a voltage regulator benefits the circuit.

Voltage regulators "vent" off that extra energy they may gain from their use.  Thermodynamics always has a way for proving that all systems lose energy and that this "lost" energy is given off as heat.  Voltage regulators are no exception, they give off heat, lots of it (depending on their use).  If they get too hot, damage could be done to the sensitive components inside or the surrounding circuitry (which can lead to a short).  The heatsink would prevent this from occurring.  Small circuits generally don't use heatsinks on them (the energy they're regulating is to small to cause a catastrophic rise in temperature), but on a high-energy application, such as a motor driver, they are needed.

So, heatsinks act as a protection against heat damage.  They may also increase the lifespan of the components (they would stay cooler and wouldn't ware out as quickly).

I don't think special nuts/bolts are needed, it just needs to make contact with the device it is trying to cool; hence, you use thermal grease to make that contact.
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Re: how to use heatsink
« Reply #13 on: November 30, 2008, 10:13:08 PM »
Just to add on to what SciTech02 said, many voltage regulators have whats called 'thermal shutdown.' This means that if they overheat, they stop working until they cool down.

With a heat sink you can increase the amount of power being pumped through the regulator because it will take more heat for it to thermally shut down.

Offline pomprocker

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Re: how to use heatsink
« Reply #14 on: November 30, 2008, 11:08:02 PM »
Do I have to use thermal grease, or am I ok without it?

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Re: how to use heatsink
« Reply #15 on: December 01, 2008, 02:01:55 AM »
You are ok without it, it helps only a little bit.

 


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