3m Thermally Conductive Tape or Thermal Paste for CPU heat-sink interface - Relative Merits 1

[M98Ranger]

Any engineer experience and thoughts on the following would be helpful.:

I am wondering about the relative merits of using thermally conductive tape (specifically 8805, 8810, 8815 and 8820) for interfacing CPUs. I know that the tape is commonly used for smaller electronic devices like mosfets etc., but is it advised to use it on something like a CPU. I was thinking that I would like to use it on my new computer w/ i7 processor and thought that it would be a more reliable means of interfacing due to the fact that the thickness and volume, thermal conductivity, etc is going to be much more controllable with a manufactured product like tape as compared to a thermal paste.

The reason that I think that thermal paste would be less reliable in terms of heat transfer properties is because the properties are all related to;
[ol 1]
[li][/li]
[/ol] the thickness of the layer applied
[ol 2]
[li][/li]the distribution of pressure throughout the cpu/heat-block interface
[/ol]
[ol 3]
[li][/li]and the quality of the curing process....as well as the quality control on the side of the materials used.
[/ol]

Is the reason that computer manufacturers don't use thermal tape such as 3m thermally conductive heat tape 8805,8810,8815, or 8820 because of the relative cost/benefit ratio?

Also, I would assume that I want the lowest possible thermal impedance taking into account the relative life of the product right? So in this case as thermal impedance is lowest with 8805 increasing to max with the 8820 (the last digits denote the thickness of the substrate in mm (5mm, 10mm, 15..)).

Any advice or help in deciding an appropriate application would be great. By the way, this is mostly for application to things that I build for myself (I always strive to over-design things whenever I can.). THANKS IN ADVANCE FOR ANY INPUT.

 

[IRstuff]

By virtual of the fact that tape has thickness and a solid surface, its conformance to a given roughness must be less than that of a grease. Proper application of grease ought to result in a lower thickness of material and better roughness conformance.

TTFN
faq731-376

 

[EdStainless]

In the overclocker world you hand lap the top of the CPU and the bottom of the heat sink. Then you use a silver loaded synthetic heat transfer grease and apply as thin of a film as you can.
Maximum surface contact and minimum thickness will optimize heat transfer.
Most CPUs use tape. It is easy and simple and it makes up for a lot of fit errors. This is called TIM (thermal interface material) and it actually changes properties as it gets heated so that it becomes more rigid. It can't be reused.

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