A propos Heat sink, there are now about 20 reports and articles on Heat transportation on my Dropbox. E.g. a 20 pages long slideshow from GORE. Explains how heat is transfered in the adhesive matrix and what you should know. And more will come. Inge On 31 January 2013 00:32, Steven Creswick <[log in to unmask]>wrote: > Victor, > > You definitely need to review the product data sheet and MSDS for the > specific thermal compound which you are using. > > The Product Data sheet should list the dielectric constant, which can give > you an idea of what impact this material might have on your circuit's > operation. > > The Product data sheet should also list the breakdown voltage of the paste. > It will likely range from 100's to 1000's of volts/mil, etc. > > Hopefully, the MSDS would tell you if you have a metal filler. Most likely > it is an oxide filler, but you need to check for sure. > > Some thermal materials harden up quite distinctly, others remain 'squishy > and sticky' for a long time, as I believe it was Larry that mentioned. If > your material is one of those that hardens, I would immediately begin to be > concerned. One of the first things I would contemplate is doing some DSC > testing to get a feel for the material's thermal coefficient of expansion > over the temperature range that is applicable to your product. Silicones > will typically have high CTE's [100-200 PPM/°C], but may have a low enough > modulus to not be offensive to your product. > > I've never done it, but you might be able to suction off some of the excess > paste, if it is a gel/grease-like material. Regardless, it will still be a > huge mess. > > As has been said, we can't definitively answer your question about > functionality since we don't know the specific material, nor the circuit, > nor application. > > > Steve Creswick > Sr Associate - Balanced Enterprise Solutions > http://www.linkedin.com/in/stevencreswick > 616 834 1883 > > > > -----Original Message----- > From: TechNet [mailto:[log in to unmask]] On Behalf Of Inge Hernefjord > Sent: Wednesday, January 30, 2013 4:17 PM > To: [log in to unmask] > Subject: Re: [TN] Gray Thermal Heat Sink Compound-paste > > Hi Vic Tor, > Application of thermal paste is an art.The interface between the heat > generating component and the surrounding is often meticously calculated, > because the heat transfer capability and precision decides the life of the > component .either it's chip, a BGA, a power transistorr or else. Removal of > heat is often the most forgotten parameter. One reason why Ericsson had > such > a success decade after decade is that a guy started todig deeply into this > topic. He made models, travelled around and preached his 2cooling message" > on Ericsson's facilities and fostered a whole generation of design > engineers > to do better heat transferrng constructions. > > The heat flow is representated in a equation as a lot of series- and > parallel coupled resistances, with addition of series/parallel coupled > capacitors. Now, let' s take a power transistor against a chassis. If you > torque the package naked, you get three main heat flows: > convection/radiation to ambient, a flow path creatid by the many > metal-to-metal contacts and radiation cross the micrometer thick non-metal. > I performed the calculations for leading away heat om a super computer. The > volume for the twenty stacked wafers was a cube, 12 inches sides, and my > job was to remove 12,000 Watts peak power! I filled the gap between the > wafers with Helium and the heat exchange was a ,salt solution. > > Now Vic Tor, if you fill the space wth 'a good thick layer' you may make a > big mistake, depending on what paste you use. The heat transfer of a paste > is not super, which many think. A thick layer can result in a worse heat > transfer, than a naked , well torqued transistor. The paste is used only > for > improving the volumes of non-physical contact, i.e. something that is > better > than air. If you have a fat paste or mat layer, you risk that the > metal-to-metal contacts be fewer. And there is a risk for material flow, > whereby the the important good contacts become fewer too.With other words : > use as thin fill-up as possible. > > I have some real good stuff about this, but my contract fromEricsson is > vivid as long as I live. In my opinion there is nothing that isn't found in > today's computer models, but Ericsson are extremly stringent. But you'll > manage on your own, there are lots to buy, put in your facts, press enter > and the computer does the job. > > I will add some good stuff in my Dropbox, will take little time... > > Inge > > > > > On 30 January 2013 16:22, Victor Hernandez > <[log in to unmask]>wrote: > > > Folks, > > > > Again I state my inquiry, " Can/theatrically excessive saturation > > of the SMT components-BGA, etc. devices with the above stated product can > a > > leakage condition". I don't feel I got an answer. I am very aware > that > > the placement of the paste should only be over the die surface and with a > > control volume. I don't have the brand and/or composition make of the > > gray material before me, only the aftermath effects of the component > > /BGA over saturation. > > > > Victor, > > > > -----Original Message----- > > From: TechNet [mailto:[log in to unmask]] On Behalf Of Nutting, Phil > > Sent: Wednesday, January 30, 2013 9:05 AM > > To: [log in to unmask] > > Subject: Re: [TN] Gray Thermal Heat Sink Compound-paste > > > > Hi guys, > > > > In our testing the type of thermal paste does not make a difference if > > the surfaces are really smooth (16 µin or better surface). Where it > > makes a difference is in rougher surfaces. And Brian is right, more is > not better. > > > > For electrical isolation we have switch from a thixotropic phase > > change material (Isostrate) to T-gard with great results. > > > > Just my 2 ¢ > > > > Phil > > > > -----Original Message----- > > From: TechNet [mailto:[log in to unmask]] On Behalf Of Brian Ellis > > Sent: Wednesday, January 30, 2013 9:52 AM > > To: [log in to unmask] > > Subject: Re: [TN] Gray Thermal Heat Sink Compound-paste > > > > It depends.... on its composition. If it's grey, it may rely on fine > > metallic powder. I have some Thermaltake TG2 which the makers claim > > has low electrical conductivity but I suspect it may have metal in it. > > I use it for CPUs to radiators, so its electrical characteristics are > unimportant. > > Consult the manufacturer's data. BTW, don't put on an excess; if it > > squeezes out, you're wasting a costly product :( > > > > Brian > > > > On 30/01/2013 15:41, Victor Hernandez wrote: > > > Folks, > > > > > > Can excessive saturation of the SMT components-BGA, etc. devices > > with the above stated product can a leakage condition. Cosmetic wise > it > > doesn't look pretty. I am concern functionally over a long period of > time. > > > > > > Victor, > > > > > > ____________________________________________________________________ > > > __ This email has been scanned by the Symantec Email Security.cloud > > > service. > > > For more information please contact helpdesk at x2960 or > > > [log in to unmask] > > > ____________________________________________________________________ > > > __ > > > > > > > ______________________________________________________________________ > > This email has been scanned by the Symantec Email Security.cloud service. > > For more information please contact helpdesk at x2960 or > > [log in to unmask] > > ________________ > > > > ______________________________________________________________________ > > This email has been scanned by the Symantec Email Security.cloud service. > > For more information please contact helpdesk at x2960 or > > [log in to unmask] > > ________________ > > > > ______________________________________________________________________ > > This email has been scanned by the Symantec Email Security.cloud service. > > For more information please contact helpdesk at x2960 or > > [log in to unmask] > > ______________________________________________________________________ > > > > ______________________________________________________________________ > This email has been scanned by the Symantec Email Security.cloud service. > For more information please contact helpdesk at x2960 or [log in to unmask] > ______________________________________________________________________ > > ______________________________________________________________________ > This email has been scanned by the Symantec Email Security.cloud service. > For more information please contact helpdesk at x2960 or [log in to unmask] > ______________________________________________________________________ > ______________________________________________________________________ This email has been scanned by the Symantec Email Security.cloud service. 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