Why do some chips run so hot without a heat sink?

[120volts]

Why do some chips run so hot without a heat sink?
After working on quite a few electronic devices that heat causes major problems.
What the XXXX why don't they heat sink them.

My friends Plasma TV keep shutting down until I installed a small fan.

I'm working on a 32" sharp that the picture get un-viewable after it heats up

Circuit cool spray makes it work for about an hour

[SteveNielsen]

Re: Why do some chips run so hot without a heat sink?

Some things are designed poorly. Heat is always a major problem in electronics. If cooling is skimped on then the life of the device will be limited.

[mariushm]

Re: Why do some chips run so hot without a heat sink?

ICs can handle various temperatures depending on manufacturing process, internal structures, package type etc. For example, in general memory ICs (sdram) which are basically small dies with lots of bond wires going to each IC pin would not be able to handle heat as well as linear regulator ICs which usually have a copper substrate that can radiate heat more efficiently.

Point is, just because a chip is hot, doesn't mean it's bad, doesn't mean the circuit is badly designed, it could be that the particular IC is warm/hot but still well within its thermal design. For example, a linear regulator that will crap out when internal die reaches 125C could obviously be as hot as 80C on the outside and in theory it would still be reliable for years, though it doesn't mean it would be a good idea to use it like that since it would cook the pcb and components around it.

Heat can cause problems in the sense that lots of fluctuations in temperature can cause shrinking and expansion and cause weak/cracked solder joints, a not that rare diagnostic for problems like the one you mention (like un-viewable after it heats up etc)

[stj]

Re: Why do some chips run so hot without a heat sink?

heatsinks cost money.