keithl@loop.UUCP (Keith Lofstrom) (03/10/90)
In article <1990Mar6.033339.2016@cs.dal.ca> lane@cs.dal.ca (John Wright/Dr. Pat Lane) writes: > > ... >I asked him about putting a heat sink on the chip and he recommended >against it, especially gluing one on with epoxy, since this might disrupt >the chips own heat dissapation ability and make things worse. > >Now this might be a conservative, "if-it-isn't-in-the-book-don't-do-it" >response. What do the engineering-types here on the net think? Anyone >have any experience in this area? >... Putting heat sinks on things might possibly break them if they weren't designed for it. Probably not, but possibly. I suspect this is simply C.Y.A.; if the heat sink causes something to fail, Intel might be liable if they told you to go ahead, and loses nothing by telling you not to. Silicon, ceramic, plastic, and metal all have different coefficients of thermal expansion. When a packaged IC changes temperature, this creates stress in the materials and the adhesives bonding them - I've seen large die pop loose from their epoxy die attach because of thermal stress. Still hanging on the bond wires, but liable to get VERY HOT with only conduction through the bond wires to cool them, killing the chips. There is a small possibility that the Intel packaging engineer designed the part so that particular combination of metal and ceramic would bend and flex with temperature in a special way - more likely they just tried it and it worked, and changes in the formula didn't work. Note: if you do try a heat sink, find a sheet of thermoset epoxy to mount it. Trying to smear on liquid epoxy may create bubbles and voids which cause stress and lead to failure - another reason most people shouldn't add their own heat sinks. And be sure to let the rest of us know how it turned out! -- Keith Lofstrom keithl@loop tektronix!psueea!qiclab!loop!keithl Launch Loop, P.O. Box 1538, Portland, Oregon 97207 (503)-628-3645
tom@ismdqa.intel.com (Tom Soukup ~) (03/13/90)
In article <39@loop.UUCP> keithl@loop.UUCP (Keith Lofstrom) writes: >In article <1990Mar6.033339.2016@cs.dal.ca> lane@cs.dal.ca (John Wright/Dr. Pat Lane) writes: >>I asked him about putting a heat sink on the chip and he recommended >>against it, especially gluing one on with epoxy, since this might disrupt >>the chips own heat dissapation ability and make things worse. >> [Stuff deleted] > >Note: if you do try a heat sink, find a sheet of thermoset epoxy to mount it. >Trying to smear on liquid epoxy may create bubbles and voids which cause >stress and lead to failure - another reason most people shouldn't add their >own heat sinks. And be sure to let the rest of us know how it turned out! The most important thing to here is to make sure that the heat sink is attached using a good thermal conductor. If you use plain epoxy, you might acutally insulate the co-processor, preventing heat dissipation. Tom Soukup. PS: This is my own opinion. I don't speak for Intel. ________________________________________________________________________________ DISCLAMER: Intel doesn't agree with much of anything that I say. UUCP: {amdcad,decwrl,hplabs,oliveb,pur-ee,qantel}!intelca!mipos3!ismdqa!tom ARPA: tom%ismdqa.intel.com@relay.cs.net CSNET: tom@ismdqa.intel.com