The HardwareLogic Thermal Compound Round-Up

[Mondoman]

Just to clarify: AS5 is NOT electrically conductive (although it *does* have some capacitance).

[garetjax]

Originally Posted by Mondoman

Just to clarify: AS5 is NOT electrically conductive (although it *does* have some capacitance).

Thanks for stopping by. What did you think of the article?

[Capper]

maybe you can explain the difference between the two as they pertain the thermal compounds, and why AS5 is much more prone to shorting out hardware as compare to synthetic compounds that are neither electrically conductive nor electrically capacitive.

[Reloadron]

Originally Posted by Capper

maybe you can explain the difference between the two as they pertain the thermal compounds, and why AS5 is much more prone to shorting out hardware as compare to synthetic compounds that are neither electrically conductive nor electrically capacitive.

Maybe I can shed a little light on things, or simply confuse things.

Before all else we should note that the application and use of any thermal compound should be done with extreme care. The idea being to apply the compound so it is sandwiched between two surfaces that are both electrically and thermally conductive. We want the paste to be highly thermally conductive and actually if the paste were slightly electrically conductive it would matter not, as long as the paste were properly applied.

However, sometimes in our haste to get things up and running so we can see that first splash screen of our new build we tend to get a little sloppy. Sometimes we apply a slightly large amount of paste and when the HSF assembly and CPU surfaces mate and are squeezed together thermal paste can escape and get on our motherboard and components surrounding the CPU pins. This can be a "bad thing"!

Let's take a lookie at what Arctic Silver has to say about a few things:

Not Electrically Conductive:
Arctic Silver 5 was formulated to conduct heat, not electricity.
(While much safer than electrically conductive silver and copper greases, Arctic Silver 5 should be kept away from electrical traces, pins, and leads. While it is not electrically conductive, the compound is very slightly capacitive and could potentially cause problems if it bridges two close-proximity electrical paths.)

Arctic Silver Incorporated - Arctic Silver 5

High-Density:
Arctic Silver 5 contains over 88% thermally Conductive filler by weight. In addition to micronized silver, Arctic Silver 5 also contains sub-micron zinc oxide, aluminum oxide and boron nitride particles. These thermally-enhanced ceramic particles improve the compound's performance and long-term stability.

Sort of like reading the ingredients in breakfast cerial. OK, according to their specifications for this stuff we have 88% inert filler that is thermally conductive. The remaining 12% consist of micron sized particles of some conductive (electrically) stuff.

Now a little speculation on my part. Just about anything is conductive. Yes, even insulators are conductive. The trick becomes how much electromotive force (Voltage) we need to place accross it to get a current (Amps) flowing actually more like milli-Amps. A rubber mat or block of wood will actually conduct if we place a great enough potential accross it. The question becomes will something "Break Down" and conduct under conditions of its intended use. In the case of Arctic Silver 5 I would say nope and therefore we could call it non conductive. Not to say it will not conduct, only to say when used as suggested it won't conduct.

Electrical Conductance and Resistance share a relationship. They are reciprocals meaning Conductance = 1/Resistance and Resistance = 1/Conductance. Resistance is measured in Ohms while Conductance is measured in Mhos (Interesting as Mho is Ohm spelled backwards).

Now we have yet another electrical unit to contend with. The Farad, which is the unit of measure for Capacitance. A real quick and simple defination of Capacitance is it opposes voltage change. Go figure huh? Resistance opposes current flow while Conductance aids current flow. Capacitance opposes Voltage Change. Seems these things are always aiding or opposing something huh?

Capacitance has a few "flavors" and can be our best friend as is the case with PSU power filtering. However, unwanted Capacitance can also be a hell of a big problem.

Let's think about data for a moment. Data for our purposes is pulses. We have all heard the term "Clock Pulses" as it pertains to RAM or a CPU. Data is transfered as pulses and these pulses are a very rapid voltage change. The pulses have a leading and trailing transitional edge. How fast does the leading edge of a pulse transition from Zero Volts to a stabil level above Zero Volts? Without beating pulse timing and characteristics to death we know a pulse is generated when we have a voltage change and capacitance does what? Remember a pulse is a square or rectangular waveform of rapidly changing amplitude (voltage).

Any two conductors placed side by side have capacitance. Look closely at the runs or traces on a PCB (Printed Circuit Board) and there is capacitance between them. The existing capacitance matters not for traces serving to only carry power such as bus voltages, however in the case of high frequency pulse trains the spacing between runs and subsequent capacitance is critical to our data. Known sometimes as "Stray Capacitance" it is actually carefully calculated in during board design. Calculated in a way that will not have an adverse effect on our data transfer. Excess unwanted and undesired capacitance can have very serious effect on our data pulses. The pulses become distorted and effects of integration and differentiation come into play. Things just get ugly.

The problem is not that the thermal paste is actually all that capacitive in nature. The problem is that if the thermal paste "bridges" runs or traces in critical areas it will change the natural capacitance between the runs or traces. The thermal paste serves as an unwanted and unplanned dielectric between the runs. That is the problem.

Again, the best way to avoid such problems is to develop and employ good workmanship skills and practices when applying paste. Take your time and apply as the manufacturer reccomends. That is the road to a nice splash screen of your BIOS.

Hope this helps answer a few questions regarding thermal paste electrical conduction and capacitance.

Ron

[screwballl]

Originally Posted by Reloadron

blah blah blah super long post

Ron

sorry had to

so what you are saying is to not splash or squeeze any Thermal Compound on the board or outside of the contact area as it may cause problems, more likely so with AS5 and some others and less likely to with certain types.

[Reloadron]

Originally Posted by screwballl

sorry had to

so what you are saying is to not splash or squeeze any Thermal Compound on the board or outside of the contact area as it may cause problems, more likely so with AS5 and some others and less likely to with certain types.

LMAO, yeah in the full unabridged version. Like 700 words or more!

Started with use the stuff right and concluded with use the stuff right. Guess it could have been covered in like a few words.

Ron

[screwballl]

it is good to get a very technical explanation for those wanting to dig deeper into the WHY... for the rest of us, it is simple:

do not splash or squeeze any Thermal Compound on the board or outside of the contact area as it may cause problems.

[Reloadron]

Originally Posted by screwballl

it is good to get a very technical explanation for those wanting to dig deeper into the WHY... for the rest of us, it is simple:

do not splash or squeeze any Thermal Compound on the board or outside of the contact area as it may cause problems.

Yeah, I agree. Capper asked:

maybe you can explain the difference between the two as they pertain the thermal compounds, and why AS5 is much more prone to shorting out hardware as compare to synthetic compounds that are neither electrically conductive nor electrically capacitive.

So I took a stab at the question. Rather lengthly stab but a stab.

Ron

[Mondoman]

Originally Posted by Reloadron

... Sort of like reading the ingredients in breakfast cerial. OK, according to their specifications for this stuff we have 88% inert filler that is thermally conductive. The remaining 12% consist of micron sized particles of some conductive (electrically) stuff.

Nice post; I'd quibble a tiny bit and interpret AS's text above as saying that the 88% includes the silver, and that the 12% is the weight of the oil components of the compound.

[Capper]

You wouldn't happen to be an AS Rep would you?