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] ______________________________________________________________________