Thermal Design Doubt

[IuriC]

Hi everyone.

I got stuck in a doubt about thermal design and I need a little help.

My system will use a TRIAC, the BTA16-600BRG. Datasheet: http://www.st.com/web/en/resource/technical/document/datasheet/CD00002265.pdf

The current flowing is about 2A RMS, giving aproximately 2W of power dissipation in the device.

The doubt is the following: Can I use a cooper board area as a heat sink for this device or I need a "real" heat sink? How would be the size of this area (mm²)?

Thank you in advance.

[KerryW]

I looked in to this recently (for a motor driver), and got conflicting information.  The data sheets sometimes give a suggested area, but that is usually for a top layer pad thermally connected to an infinite internal ground plane.

The best data I could find for a top layer single sided heat sink was 1000/cm^2.  Using that, and going for 75 C rise, you would need 26.67 square cm. About 2" x 2".

I have not yet been able to test my board under full load, so I can't say how reliable this information is.

[tszaboo]

Yes you can. Take a look at figure 11 in the datasheet. With about a 3x3cm PCB area, you have 30K/W thermal resistance, for 2W that is 60K. Even with 60 degrees ambient, you are still below the 125 degrees junction. So lower ambient and or bigger copper area should be fine.

[IuriC]

The BTA16 is on TO-220 package, and this graph is for D²PAK 

[tszaboo]

The BTA16 is on TO-220 package, and this graph is for D²PAK 

Ok, that is true.
If you want to use the PCB as heatsink, why arent you using the package which was designed to be used that way? The only reason to use the TO220 is to have a heatsink (or because you are stuck with it). If you have a TO220 than the only way to use it with the copper if you bend the leads and you surface mount it, in wich case it will act more-less than a D2PACK.

[max_torque]

Assuming you are going to use the SMC Dpak, then if i had any doubt, i'd include the footprint for a suitable heatsink too!

Even if you don't end up using it, it will help negate the need to re-spin the pcb.... ;-)

I use these neat little ones:



Because they stand over the package they hardly take up any extra real-estate, and need no mounting holes etc

[IuriC]

As you guessed, I'm stuck with the TO-220 one.

I was afraid of getting great difference bettwen D²PAK and the TO-220 bended and mounted in a copper area. I guess that the only way to figure it out is experimenting and taking some measurements.

Thank you all.