Post by thread:[OT] conductive epoxy (and SI :)

maybe it helps one or another: i just saw a Master Bond announcement for a nickel conductive 2-component epoxy (EP76M), surface resistance ~2 ohm, volume resistivity 15 ohm cm (maybe for gluing vias on boards --there was this thread in the last days :) but: the thermal conductivity they give as "25 BTU/hr/ft^2/¡F/in" -- geez :) when i wrote my example why i think SI units are cool, i thought i may have exaggerated a bit in the part of the examples of "traditional" units -- but obviously not. anybody out there who can make a case why, after having calculated the electrical resistance of the epoxy using [ohm cm], =anybody= would want to calculate the thermal conductivity in that unimaginable unit above? i sure think [W/m K] -- or, if you want, [W/cm K] -- looks =a lot= nicer :) this independently of the fact that the above unit is wrong and should be [BTU/hr/ft^2/(¡F/in)], which derives from the fact that thermal conductivity is usually thermal flux ([W/m^2] or [(BTU/hr)/ft^2]) per temperature gradient ([K/m] or [¡F/in]), which then combines to either [W/m K] -- or [BTU/hr/ft^2/(¡F/in)]... ge

>Why not make your own conductive epoxy. Regular epoxy mixed with copper >powder. For some reason this is done with silver powder usually. Maybe copper reacts with the epoxy, its sufrace oxidizes and looses conductivity. Once I have tried antimony powder instead and it worked, but that is not advisible due to antimony toxicity. I had good results with another conductive glue - polysterene (or styropore - foamed polystyrene) dissolved in acetone and mixed with graphite powder. As graphite source I used a pencil refil, heated it in the stove to burn the wax off and then ground with a razor. Hopefuly I have all the words right. Josef ====================================================================== Electronical devices for chemical laboratory, custom electonics design ---------------------------------------------------------------------- Snail Instruments Josef Hanzal, M. S. Vojanova 615 phone/fax: +420-311-24433 266 01 Beroun e-mail: spam_OUTsnailTakeThisOuTiol.cz Czech Republic URL: http://www.vitrum.cz/snail/ ======================================================================

You can buy very fine ground graphite powder in an artists' shop. It is also the best lubricant for car door locks. Sven -----Ursprungligt meddelande----- FrŒn: Snail Instruments <.....snailKILLspam@spam@IOL.CZ> Till: PICLISTKILLspamMITVMA.MIT.EDU <.....PICLISTKILLspam.....MITVMA.MIT.EDU> Datum: den 20 april 1999 19:18 €mne: Re: [OT] conductive epoxy (and SI :) {Quote hidden}>>Why not make your own conductive epoxy. Regular epoxy mixed with copper >>powder. > >For some reason this is done with silver powder usually. Maybe copper >reacts with the epoxy, its sufrace oxidizes and looses conductivity. Once I >have tried antimony powder instead and it worked, but that is not advisible >due to antimony toxicity. > >I had good results with another conductive glue - polysterene (or styropore >- foamed polystyrene) dissolved in acetone and mixed with graphite powder. >As graphite source I used a pencil refil, heated it in the stove to burn >the wax off and then ground with a razor. Hopefuly I have all the words right. > >Josef > > >====================================================================== >Electronical devices for chemical laboratory, custom electonics design >---------------------------------------------------------------------- >Snail Instruments Josef Hanzal, M. S. >Vojanova 615 phone/fax: +420-311-24433 >266 01 Beroun e-mail: EraseMEsnailspam_OUTTakeThisOuTiol.cz >Czech Republic URL: http://www.vitrum.cz/snail/ >====================================================================== >

At 22:33 04/20/99 +0200, MILTON MEDICINTEKNIK KB wrote: >You can buy very fine ground graphite powder in an artists' shop. It is also >the best lubricant for car door locks. actually, you should get it in hardware shops, too. it's commonly used as a lubricant with all kinds of metal where oil/grease is not appropriate. ge