Transistor die mounting and heat sinking

Feb 03, 2007 9 Replies

I'm looking for information how a (2N2222 typ ) die can be attached to a pc board to provide a low thermal path and am looking for info on analyzing the thermal path and what material to use to hold the die to the board.



I've done a google search but likely have not used the right terms touse for the search.



Any suggestions would be appreciated.



Harry


Are you truly asking about DIE? If so, there are metal-filled epoxies used for such DIE mount.

...Jim Thompson

| James E.Thompson, P.E. | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC\'s and Discrete Systems | manus | | Phoenix, Arizona Voice:(480)460-2350 | | | E-mail Address at Website Fax:(480)460-2142 | Brass Rat | | http://www.analog-innovations.com | 1962 | I love to cook with wine. Sometimes I even put it in the food.

Nominaly, transistor die are soldered to a metal pad (or the can if a metal case). So do the same thing: die attach using (high temp) solder. Please do not ask what alloy is used, becasue (so far) nobody is talking. BTW, you cannot get blood (better power rating, better sat, etc) out of a turnup (the crappy *low* power *signal* 2N2222). The damn thing is a resistor above "reasonable" currents (say in the

100mA region)!

More expensive and less reliable than solder.

Most plastic packaged ICs seem to be attached to their leadframe using conductive epoxy. There must be some reason for doing it this way. One popular brand is Ablestik.

Chris

Maybe because the die attach area is to small to work with?

'Molytabs'(Molybdenum metal)are usually used as a pedestal for the die. Then held together with silver epoxy. Most commonly used on alumina substrates...

Not so, most _IC_ die-bonds are eutectic.

Most chip bonds to _PCB_ ARE epoxy.

...Jim Thompson

| James E.Thompson, P.E. | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC\'s and Discrete Systems | manus | | Phoenix, Arizona Voice:(480)460-2350 | | | E-mail Address at Website Fax:(480)460-2142 | Brass Rat | | http://www.analog-innovations.com | 1962 | I love to cook with wine. Sometimes I even put it in the food.

Perhaps I was wrong when I said most, however certainly hundreds of millions of plastic packaged ICs use conductive epoxy, for example LFCSP packages at least. I don't know about older dual in line packages etc.

Chris

Hmmm! I've not noted that, but will take your word for it, for I don't know for sure.

...Jim Thompson

| James E.Thompson, P.E. | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC\'s and Discrete Systems | manus | | Phoenix, Arizona Voice:(480)460-2350 | | | E-mail Address at Website Fax:(480)460-2142 | Brass Rat | | http://www.analog-innovations.com | 1962 | I love to cook with wine. Sometimes I even put it in the food.

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