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Discussion Starter #1
Although having similar properties, Silicone Dielectric Grease is not the same as Thermal Grease. Silicone Dielectric Grease is a temperature resistant material used for lubrication and as a sealant to prevent corrosion. Thermal Grease is a temperature conductive material used to assist with efficient heat transfer to a heat sink with electronic components. The incorrect application of Dielectric Grease on your new TFI ICM or using Thermal Grease to seal a harness connector can result in component failure. Let’s find out why…





Silicone Dielectric Grease is a waterproof, non-conductive, temperature resistive lubricant usually used for preserving rubber parts, such as o-rings. It does not swell or soften rubber as may be the case with hydrocarbon based lubricants. Typically, it is used as a means of lubricating and sealing the rubber portions of a connector without arcing.

When used in a spark plug boot, it seals the boot from water intrusion and prevents the rubber from sticking to the spark plug ceramic. It is formulated to withstand higher temperatures and it does not break down in the spark plug environment. Because it is non-conductive, it can be applied to the actual contact as well because the spark plug high contact pressure is sufficient to penetrate the grease.

On the other hand, this is not the case with multi-pin electrical connectors where it is not recommended to be applied to the electrical contacts. In this case, it could interfere with the electrical signals passing through the connector where the contact pressure is very low. With harness connectors, it should only be used as a lubricant and sealant on the nonconductive mating surfaces of the connector.

Silicone Dielectric Grease is typically a component of Thermal Grease due to its supportive properties. In addition to carrying suspended heat conductive particles, Dielectric Grease fills the gaps and conforms to both the component's and the heat sink's uneven surfaces, adheres to those surfaces, maintains its consistency over the required temperature range, resists drying out or flaking over time and does not degrade with oxidation or break down over time.





Thermal Grease (also called thermal gel, thermal compound, thermal paste, heat paste, heat sink paste, heat transfer compound, or heat sink compound) is used to support conductive heat transfer between the TFI ICM and the heat sink. This conductive heat transfer is done through a thermal interface, or direct contact between the two surfaces.

Thermal Compounds improve the efficiency of conductive heat transfer by filling minute air gaps that occur between imperfect surfaces. The contact area between the heat sink and ICM has inherent surface imperfections from machining marks, casting irregularities and even invisible sub-microscopic spaces which reduce direct contact and promote air spaces. These small air spaces within the contact area reduce conductive heat transfer due to air being approximately 8000 times less efficient at conducting heat than, for example, aluminum which is a common heat sink material.

Thermal Conductivity and "Conformability" (i.e. the ability of the material to conform to irregular surfaces) are the important characteristics of thermal grease. These compounds generally contain a conductive substance such as ceramic, metal or carbon and usually include Silicone Grease as a medium for conformability. Keep in mind that Thermal Compounds conduct heat far better than air, but far worse than metal. These compounds are only intended to fill the gaps that would otherwise hold air, not to create a layer between the ICM and heat sink as this would reduce conductive contact decreasing the effectiveness of the heat sink. In other words, excess grease separating the metal surfaces more than the minimum necessary to exclude air gaps will only degrade conductivity, increasing the risk of overheating. The compound must have a suitable consistency to apply easily and remove all excess to leave only the minimum needed.





Arctic Silver 5 is a premium thermal compound having a high-density filling of micronized silver and enhanced thermally conductive ceramic particles. This efficient silver thermal compound exceeds the conductive properties of metal oxide, nitride, copper and aluminum. It is commonly used for modern high-power CPUs and high performance heat sinks and can be found at most electronic stores. Be aware that silver based thermal grease can be slightly electrically conductive or capacitive, meaning if some flows onto sensitive circuits it can cause malfunctioning and damage. At $9.95 for a 3.5g tube, this is the high end product many in-the-know are using for TFI ICM installation.

Radio Shack/Walmart/Comp USA – (Arctic Silver 5) Part # AS5-3.5G





Automotive TFI ICM Heat Sink Compounds

Napa/Echlin – (Echlin) Part# Echlin TPL45

AutoZone – (Wells Vehicle Electronics) Part# Duralast SL203

O’Reilly Auto Parts – (Borg Warner) Part# BWD CL80

Discount Auto Parts – (Standard Motor Products) Part# SMP SL-3
 

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It's equally important to note that Dielectric Grease is the OPPOSITE of Electrical Grease, although they appear very similar and are both silicone greases.



Electrical grease is no more electrically conductive than dielectric, but that's not why it improves electrical connections. Dielectric is not merely an insulator; it has high film strength (like EP chassis & bearing grease), so it physically separates surfaces, just like the oil in the bearings in a running engine. Electrical grease is noticeably thinner, and doesn't impede physical contact nearly as well. So because it shares the water-displacing and Oxygen-inhibiting properties of dielectric grease, it only improves electrical connections in the long-term by reducing oxidation & corrosion that could interfere later.

So for electrical contacts with HIGH contact pressure (like alternator studs), dielectric grease doesn't live up to its name, and many people THINK it's good for that application. But it's not - the film can reduce the actual contact area such that, over time, the terminals will overheat in those spots & burn out (slowly, due to the silicone grease blocking Oxygen), breaking the connection after some time.

Thermal Grease is also usually based on silicone grease, but the silicone is primarily a binder for the Zinc oxide which transfers the heat. This renders thermal grease ineffective as a lubricant, so "thermal compound" is a more-accurate name.

Then there are all the varieties of Lithium Grease (blends of any type of oil & a lithium ester as a soap), to include white lithium (a cheap general-purpose automotive grease for hinges & latches), lithium bearing grease (for equipment bearings that don't see particularly high loads, temperatures, or duty cycles), lithium EP (extreme pressure) grease (for trailer bearings & harsh equipment that doesn't see high temperatures), lithium EP water-resistant bearing grease (for boat trailers), and lithium EP disk brake wheel bearing grease (for EP applications that can be subject to 300F or more). Of course, there are MANY other lithium grease formulations for every specific application, including arresting gear on aircraft carriers, and steam equipment.

Teflon (PTFE) Grease is a fairly new specialty grease with limited application due to cost (mostly related to DuPont's patents). Ford adopted it in bulk for driveshaft noise in the late 90s/early 00s, but also recommends it for certain older applications like speedometer cables. It is similar to Graphite Grease in that both use a solid powdered low-friction filler material to thicken the base oil.

Molybdenum Disulfate Grease (GMD) was the original speedo cable lubricant, but it has largely been abandoned by the automotive & consumer industries due to its hazardous & toxic properties. It is still in-use by the US military in certain applications in gunnery, tracked vehicles, & aircraft.

The list of greases goes on to include hundreds of natural types (like mink oil, lard, tallow, & shortening), refined types (like asphalt & Vaseline), and synthetic types (like Krytox) or blends (like KY). Each has a specific set of characteristics that make it better-suited to certain applications, and few are totally interchangeable.

USE THE RIGHT GREASE. :thumbup
 

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Discussion Starter #3
As a side note, today I went to O’Reilly Auto Parts and asked for a package of Thermal Compound for the TFI ICM. What they brought me was BWD CL80 which their computer lists for that specific purpose. I was surprised to see that is was a clear product showing no sign of suspended conductive substances. This appeared to be plain old Silicone Dielectric Grease which is primarily used as a lubricant and insulator.

I have also confirmed that Ford currently recommends Motorcraft XG-3A (supercedes D7AZ-19A331-A (Motorcraft WA-10)) for TFI ICM installation. Fact is, XG-3-A is a non-opaque, waterproof Dielectric Compound also used for Brake Caliper lubrication and spark plug boot insulation. This may not provide the best heat conduction for your TFI ICM as this product is heat resistant as opposed to heat conductive.

Quality Thermal Compound should have a base of Dielectric Grease or polysynthetic oils with suspended combinations of silver, zinc nitride, aluminum oxide, boron nitride and/or ceramic fillers giving it an opaque white, brown or black color. Be sure to look at the Thermal Compound that you receive and ensure that it is correct to provide maximum heat protection for your TFI ICM. Again, my recommendation is to use a quality Thermal Compound for the best conduction to protect your TFI ICM from heat related failure.



Thermal Compounds










Dielectric Compounds






 

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I have also confirmed that Ford currently recommends ... waterproof Dielectric Compound... This may not provide the best heat conduction for your TFI ICM as this product is heat resistant as opposed to heat conductive.
Take a closer look at your first post: even thermal compound is NOT as conductive as straight metal-to-metal contact. And if you follow the proper procedure to apply XG-3A to the ICM, you'll end up with virtually no grease between it & the heat sink. The reason is: WATER is the enemy. If it gets in there, it causes corrosion, which is an even-better insulator than a microscopic film of waterproof grease. So the grease isn't there to directly promote heat transfer; it's there to keep the water out, which would degrade the transfer. Just run a wide, flat file across the heat sink to clean it down to the bare metal (the new ICM you're installing should already be shiny), and bolt them together with the recommended grease. This isn't a 10W LED being pushed to its limit on a marginal heat sink with a tiny contact patch inside a sealed housing; the ICM has a HUGE contact patch against the heat sink, and both surfaces are VERY flat, so thermal compound isn't as important as water displacement, especially in an underhood environment.

TRUST FORD - they know what they're recommending. :thumbup
 

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Discussion Starter #5
Although I appreciate your perspective, I will have to disagree with you on this one.


You miss the point on the use of Thermal Compound. Again, what it does is improve the efficiency of conductive heat transfer by filling minute air gaps that occur between imperfect surfaces. Yes, direct contact of the metal surfaces is most efficient but this would require an almost polished smooth surface. Fact is Thermal Compound fills in the many very small imperfections with conductive metallic or ceramic material giving the surface a better contact area which provides more efficient conduction. Whether you follow the Ford procedure or not, you will still end up with at least a small layer of compound between the ICM and the heatsink. Just remove an ICM and look at the contact areas. Nothing in the Ford Installation procedure says to wipe off the new grease, only to coat with 0.79mm (1/32" thick) and torque the ICM mounting screws to 15-35 lb-in starting with the upper right hand screw.


TRUST FORD - they know what they're recommending. :thumbup
I am not suprised that you would follow the Ford line of using Dielectric Grease, but in my many conversations with experienced Ford Techs and Managers they do in fact recommend a Thermal Compound. I have even read that Ford Accelerated Credential Training is instructing techs to use a white Thermal Compound as well. As you know, many of these Thermal Compounds have a base of Dielectric Grease or proprietary oils that do create water resistance minimizing intrusion and promotion of corrosion. And as you, Ford Engineers and Techs also know, Ford designs parts and materials that efficiently have multiple uses such as the Motorcraft XG-3A (aka Silicone Brake Caliper Grease and Dielectric Compound). This has to do with heat resistance, not heat conduction. Ford's penchant for cost efficiency on a vast scale does NOT necessarily make XG-3A Dielectric Grease the BEST product for ICM installation. Like any other auto maker, Ford knows what is best for Ford which may deem XG-3A adequate, but that's not good enough for me. Again, I do not recommend using Dielectric Grease for TFI ICM installation.


Thanks for posting your perspective in my Tech Write-up. :thumbup
 

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Hey Seattle what if I wanted to re-seal my heat-sink and bought the Arctic Silver 5 and used that for the majority of the base where the TFI contacts the heat-sink, and then used the XG-3 that I already have to line the outside perimeter for water protection. That way I would have the particles in the middle to help with contact and heat transfer and the bead of XG-3 on the outer edge to keep the water out.....how does that sound? :thumbup -Kevin-
 

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Ok fellas. Need to install my new ICM on the side of my distributor. What's the suggestion there. What I have been reading from here your ICM are mounted to heat sink which draws the heat away from it. However when bolting it direct to a distributor what's your suggestion.
 

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Heat sink compound should be used on either style.

Before the TFI systems that Ford started using I can remember using the heat sink compound on every transistor we ever replaced in dad's shop big or small I didn't matter. The heat some of these transistors produce is pretty insane without a suitable heat sink they would cook themselves to failure.
 

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Same, same.
Heat sink compound should be used on either style.

Before the TFI systems that Ford started using I can remember using the heat sink compound on every transistor we ever replaced in dad's shop big or small I didn't matter. The heat some of these transistors produce is pretty insane without a suitable heat sink they would cook themselves to failure.
Thanks guys. After some searching some more I found that a Heat Sink compound is best just as you suggested.
 

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yo,
For posterity;
by Ford in 1996 F-Series and Bronco with Gasoline Engines Workshop Manual (Partial)

Section 03-07A: Ignition, Distributor
REMOVAL AND INSTALLATION
Ignition Control Module
Removal
1.Remove two screws retaining ignition control module (ICM) (12A297) heat sink assembly to left fender apron.
2.Disconnect harness connector from ignition control module.
3.Remove two screws retaining ignition control module to heat sink and remove ignition control module.
Installation
1.Coat ignition control module baseplate with silicone compound, approximately 0.0179mm (1/32-inch) thick. Use Silicone Dielectric Compound (WA-10) D7AZ-19A331-A or equivalent meeting Ford specification ESE-M1C171-A.https://www.fcsdchemicalsandlubricants.com/Main/product.asp?product=Silicone Brake Caliper Grease and Dielectric Compound&category=Greases'

2.Position ignition control module onto heat sink and tighten two retaining screws to 1.2-1.8 Nm (11-16 lb-in).

3.Install ignition control module heat sink assembly on left fender apron using two retaining screws, and tighten to 9-14 Nm (80-124 lb-in).
4.Connect wiring to ignition control module.
 

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Discussion Starter #13
Again,

In my many conversations with experienced Ford Techs and Managers they do in fact recommend a Thermal Compound. I have even read that Ford Accelerated Credential Training is instructing techs to use a white Thermal Compound as well. As you know, many of these Thermal Compounds have a base of Dielectric Grease or proprietary oils that do create water resistance minimizing intrusion and promotion of corrosion. And as Ford Engineers and Techs also know, Ford designs parts and materials that efficiently have multiple uses such as the Motorcraft XG-3A (aka Silicone Brake Caliper Grease and Dielectric Compound). This has to do with heat resistance, not heat conduction.

Ford's penchant for cost efficiency on a vast scale does NOT necessarily make XG-3A Dielectric Grease the BEST product for ICM installation. Like any other auto maker, Ford knows what is best for Ford which may deem XG-3A adequate, but that's not good enough for me. Again, I do not recommend using Dielectric Grease for TFI ICM installation when a better performing product is readily available.

I choose to use Arctic Silver 5, which is a premium thermal compound having a high-density filling of micronized silver and enhanced thermally conductive ceramic particles. Due to these characteristics, I believe this efficient silver thermal compound exceeds the performance for Motorcraft XG-3-A for TFI ICM installation.
 

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yo Settle,
I hear you; I never researched the Arctic Silver 5 and appreciate your info and choice.
The MSDS for both products doesn't help much exc to show Specific Gravities;
4.05-4.15 for Arctic Silver 5
1.1 @25°C for XG-3-A
 

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Ceramique II vs Arctic Silver 5

Sorry for bringing this back from the dead, but I would like to continue this conversation just a bit. I agree with Seattle FSB, and applaud him for the great writeup. I have two new points to consider.

First, let me start by saying that after some thorough testing, I've come to realize that the Distributor housing IS the ignition ground. In other words, when your coil is turned on, it is ultimately the distributor housing that is bolted to the engine block that is grounding the high amperage coil. The distributor touches the metal plate on the back of the module, as well as having two little bolts that connect the module to the distributor. So now the module is grounded to the distributor (maybe...). The module SENDS this ground to the PCM and to the coil, when it wants to ground the coil (turn it on).

Before I realized this, I thought that Ceramique II would be the best choice for module paste, since it contains no metal, just ceramic. That makes the module have no electrical contact with the distributor base, except via the two bolts. Also, Ceramic compound is not quite as good at transferring heat as a silver compound. But the Arctic Silver 5 has some capacitance, and electricity can travel through it. Now that I know the module needs to electrically connect with the distributor housing to provide an ignition system ground, I think my choice of Ceramique II was not the best. Although I'm pretty sure it will work just fine, since there are the 2 module bolts still connecting the module backing plate to the distributor. And better than dielectric grease anyway.

Second, the tube of Ceramique II that I bought is very thick. It's difficult to spread, and even more difficult to spread thin. The recommended 1/32 of an inch would be tough, unless bolting it down helps squeeze it around some, or a hot engine does something for slightly melting the compound (unlikely). What I had hoped for was something with a consistency about like toothpaste, maybe slightly thicker. What I got was something more like nearly frozen honey, or gasket silicone that's starting to dry. It is far more "sticky" than "wet". I'm not sure if I got a bad batch, or if this is just a bad choice of material. [I ask you to share your experience with Ceramique II with me].

I would also note that the specific gravity of Ford's silicone dielectric grease versus Arctic Silver 5 is telling. Arctic Silver 5 was 4x as dense. That's a good sign that there's a lot of silver in that compound, increasing it's weight.

So I think I'm going to try Arctic Silver 5 next. I would like to hear how thick it is, versus Ceramique II. I think we're looking for something with a consistency very similar to anti-seize. I would also like to hear if the increased capacitance of Arctic Silver 5 is problematic, or beneficial in your opinion.
 
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