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# Do you need the pressure applying bots

It has been long thought that you had to have bolts clamping the hot and cold plates together because the pressure required FAR exceeds the recommended pressure for a CPU. If the bolts aren't required then this would simplify direct die TEC blocks and most importantly make them smaller. It seems that MBM manufactures are intent to putting massive caps as close as possible to the CPU making it had to find the extra space required for the bolts.

After doing some investigation it seems that 150-300 psi is is recommended and the formula for finding the recommend torque on the screw are the result of this formula

T = (C x D x F x in2) / (# of screws)

Using the following equation you can solve for torque per screw:
T = torque per screw (in-lbs)
C = torque coefficient (0.20 as received, 0.15 lubricated)
D = nominal screw size (4/40 = 0.112, 6/32 = 0.138, 8/32 = 0.164)
F = Force (lbs / in2)
in2 = Module surface area (length x width)

I'll be using these numbers

C= 0.20 (who oils their bolts)
D= 0.157 (4mm)
F= 150 (150 is the minimum recommended)
in2= 3.875 (50x50mm TEC)
# of screws = 4

4.5628125 = (0.20 x 0.157 x 150 x 3.875) / (4)

So to achieve the minimum required pressure on the TEC you'd have to do each bolt up to 4.56 inch pounds.

This is all very nice but doesn't mean much without knowing the mounting pressure of your current block to the CPU.

I have a D-tek fuzion V1. I then used this torque wrench to measure the required force on the spring. What i found is that the torque wrench hardly registered any movement!

This doesn't however mean you couldn't remove the springs and do the bolts up more.

I then had a play with the torque wrench i held it tight and tried to do up a 4mm fillips head screw to get a feel for how much 5 inches was

at 20 inches the screw driver slipped out and stripped the head a bit ( its hard trying to hold everything

15 inches seem like a lot i dont think i'd be brave enough to apply 15inches to a MBM

10 inches is pretty firm

So it's my opinion that it could be possible to meet the minimum recommended pressure of a 50x50 mm TEC. it may or may not require a aftermarket backing plate like IRA-K uses but it wouldn't do any harm having one that's for sure.

Im not about to crank my CPU block up to see if it will support 4.56 inches per screw i'll have to leave that to someone else to do and measure the force.

Keep in mind that 4.56 is the minimum required for a 50x50mm TEC so a bigger TEC will require more bolt tension and better performance should be achieved at 300psi over the 150 we have used here.

-----------------UPDATE 28/10/08-----------------------
Well today at work a working 1.6 p4 (478) PC was passing my desk and i just couldn't resist taking it home for some "TESTING"

Right what i've done is bin the 478 bracket and drilled and tapped the heat sink to take 4mm screws. I then made a back plate out of 4.5 mm Acrylic. There's some nice foam there too.

Well i can tell you i could apply 5inch pound in this format. the acrylic is bending a bit though.

I then booted the machine and all was well

After that i went for 10 pound which is at the top end of the recommend force of 300 psi and what you'd need minimum if you were running 2 TEC's

Well i couldn't achieve the 10 pounds all that was happening was the mbm and acrylic was bending to much and the screws weren't going into the heat sink straight any more this is a very dubious 8 pounds.

I then booted the machine and all was well

Well i believe i've answered the question, that it's not totally necessary to uses the pressure applying bolts. though i still recommended them for top performance and safety. you'd definitely need a torque wrench to know how much your applying 5 pounds does feel like a lot when your doing it to your mbm and watching everything bend!

10 pound should be possible with a bigger and better backing plate but i think it would have to be quite substantial like a large peace of 3mm steal

Credit goes to Ira-K for being a credible TEC user and suggesting you didn't necessarily need the bolts and to me who decided to find out if it was true.

Edited by Ultrasonic2 (muffy) - 10/28/08 at 3:14am
 My System (13 items)
 My System (13 items)
make a custom cpu backplate like i did and apply the ~300 PSI

I plan on strengthening my current backplate so I can do such a thing.. my current setup has the d-tek springs for the block completly compressed and I even put some pressure on the spacers ... motherboard did not even flex a bit
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Custom backplate? nice man show a pic! I will need to figure something out when I go Tec.
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Nice man thanks! I will have to make one of those when I go TEC.
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Logitech Antec 650w Neopower herbal green Logitech
Rotting blue/black neo
Unfortunately that is a very poor back plate as it doesn't apply any pressure to the back of the CPU socket. The pressure is being applied to the CPU so you need to support the back of it otherwise your just bending the MBM . you'd be better off with the fuzion back plate which applies the pressure in the correct place.

When i get my chillier going i'll make a new back plate even though i wont need it for applying TEC pressure cause we should be able to get better CPU temps with more pressure
 My System (13 items)
 My System (13 items)
Actually its mounted directly to the mobo with a thick pad under it.... that pic isnt right.. i need to edit it when i clean up my CPU block this weekend

but yeah its directly on the CPU socket now... ira-k gave me a post-full when I made the mistake the first time around lol

edit: combining post+full gives you po****ll.. it has ST*U in the middle so it sensors me
Edited by XFreeRollerX - 10/24/08 at 11:32am
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Western Digital AAKS Series 500GB Windows 7 Enterprise x64 Custom Cooked for SPEED Samsung 58" B650 1080p Plasma Logitech DiNovo Mini
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Western Digital AAKS Series 500GB Windows 7 Enterprise x64 Custom Cooked for SPEED Samsung 58" B650 1080p Plasma Logitech DiNovo Mini
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Well thats good to here
 My System (13 items)
 My System (13 items)
I make mine with 3/8" HDPE with a 1/16" piece of Neoprene between it and the mobo..I use rubber flat washers on the top-side around the studs with a washer and nut on top of it, that way I can pre-compress the Neoprene before I ever bolt down the TEC block..Works pretty well on TEC or WC'ing for a nice hard mount...

The cut outs are to keep the back of the v-reg's open to air circulation..

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2x Seagate 160 Perp. RD-1 2x Asus Vista Premium Corsair HX 620
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Nice Ira...I was planning on using some neo in between purely for insulation. However now I see that it is for more then that. It looks like you used one of your wife's cutting boards to make that back plate out of lol
 Bong Rig (13 items)
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E6750 @3.6 1.40v P5N-D SLI 750i EVGA 9800GX2 4Gigs G.Skill 800
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40G WD IDE/250G sata 40xDVDRW Vista 64bit 22" hp A4576A
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Logitech Antec 650w Neopower herbal green Logitech
Rotting blue/black neo
 Bong Rig (13 items)
CPUMotherboardGraphicsRAM
E6750 @3.6 1.40v P5N-D SLI 750i EVGA 9800GX2 4Gigs G.Skill 800
Hard DriveOptical DriveOSMonitor
40G WD IDE/250G sata 40xDVDRW Vista 64bit 22" hp A4576A
KeyboardPowerCaseMouse
Logitech Antec 650w Neopower herbal green Logitech