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 ΅in 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,
> >
> > ______________________________________________________________________
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