Heat from IC - anything to be concerned about?

[Hippogriff]

I have my 9 RGB LED circuit. A PIC 16F1825 running at 32MHz with 9 pins used to connect to a pair of ULN2003ANs - 6 pins to one of them and 3 to the other (maybe I would balance them out more in future - 4 and 5 - if the answer to this question is "yes").

The ULN2003ANs are then used to connect my RGB LEDs to 12v.

I have run my circuit for hours at a time and everything appears fine. The LEDs switch colours, flash and fade. I'm really just asking this question for my own due diligence and safety.

I've noticed that the ULN2003AN with 6 connections does get warm. I'm not sure how warm, but much warmer than room temperature but not warm enough to hurt / burn when I touch it.

My other ICs (MAX667 and PIC) do not get warm at all. The other ULN2003AN (with 3 connections) gets warm, but not as warm as the first ULN2003AN.

The ULN2003AN is, apparently, rated to 70 degrees Centigrade and I don't think it's anywhere near that (I really should buy something to measure this) but I'm curious as to whether I should bite the bullet now and pro-actively consider some kind of heatsink in the small space that I have available to me, or whether I'm concerned about nothing?

Any thoughts appreciated... firstly, I guess... is it normal with what the IC is doing? I guess that nearly all its transistors are changing state all the time with what is going on in the circuit. That must be expected to generate heat.

If I decided I wanted / needed a heatsink, would I just glue some metal to the top of the IC?

 

[alec_t]

If you can keep your finger on the chip for 10 secs without pain, and the circuit is in a well-ventilated enclosure, then you probably don't need a heat-sink (although one might well give the chip a longer life-time). If you do decide to add a heat-sink, don't attach it with hot-melt glue !

 

[Hippogriff]

Oh, yes, I can easily put my finger on the IC for more than 10 seconds without pain. I would certainly still be interested in anything easy and cheap that would give the IC a longer timetime. Are there specific IC heatsink components (something that, heaven-forbid, might just "clip on"?) or is scrap metal usually the way to go?

P.S. - ah, RN70M from Maplin for 14 / 16 pin IC. Will keep looking.

 

[Mr RB]

A small piece of metal screwed or clamped down on top of the IC will do wonders. You can also glue-on a small metal sink of top of the ic, but don't use superglue use 2-part epoxy.

 

[KeepItSimpleStupid]

There is a clip on heat sink. It works well when the device is socketed. You need clearance to insert it from the edge if you don't use a socket.

 

[Hippogriff]

Everything is socketed, so I'm OK there.

**broken link removed**

I'm in two minds about whether to go and even try this now... alec_t's post made me feel more relaxed about the situation. It was running perfectly fine for several hours again last night, so I don't think it's like something that's going to go "pop, fizzle".

Then again, best for me to know more about all this stuff, for whenever the need arises.

 

[audioguru]

Your IC is warm, not hot so it will be fine.
A socket prevents heat from travelling from the pins to the copper on the pcb.
The IC will be cooler if it is soldered to the pcb copper and if the copper tracks on the pcb are wider.

 

[KeepItSimpleStupid]

This is what I have used: http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=HS179-ND

It was a motor diver and I used a machine pin socket for that.