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Modifying backplate bracket.

post #1 of 6
Thread Starter 
May need to be moved to "other cooling discussions"

While this may seem arbitrary, I would like some input on modifying a backplate. My motherboard and noctua securfirm 2 bracket have 2 areas that conflict. I was curious if anyone has removed the supplied "cushion" on the back of the bracket (board side), and replaced it with a rubber with a higher durability like viton, nitrile, or butyl base, ect. that is thicker by 1+ mm (to clear the modules and resist compression). As the bracket padding has a unique shape, should it be identical, or a general shape to spread the load? Any input appreciated.

I have no problem doing this by myself, but curious if others have done it with success and could provide unforseen, to me, problems before I go all in..
Edited by siggie30 - 12/6/12 at 2:44pm
    
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post #2 of 6
To be quite honest, I don't have too much experience with actually performing these exact operations on a backplate, but from my mechanical understanding, I'd say you'll be fine either way:

a) to use thicker rubber over the backplate is quite alright - mind your screw length though, obviously.
b) if you have to, you can even consider removing material from the backplate itself where necessary, but only from non-strength-relevant areas (creases, edges and folds in the metal etc. should better be left alone, flat areas are generally ok to remove within reason).

It's supposed to be distributing the force as evenly as possibly, so the bigger the area covered by the rubber, the better it is in theory. However, if there are components in the way that stick out, they would receive an unproportionally big amount of force. So try and make the rubber touch as much flat area as possible, and as little "uneven landscape" (components) as possible, and you'll be fine. If I were to use really thick rubber (>3mm), I'd just cut out little hollows or pits over the components in question with an exacto knife, instead of removing the rubber in that place completely. Would make for a more uniform look and a better coherence of the rubber, so that it doesn't crumble or shift in place.

Maybe you can provide a few pics of the backplate and the conflicting areas in question, so we can see exactly what you're dealing with.

Chris
Edited by decnet - 12/4/12 at 5:37am
post #3 of 6
Ok, since I'm bored, I'll include a few graphs to illustrate what is going on between that rubber mat and the component.

First illustration: No cutout, the mat touching the component all the way. My (hideously) drawn load graph is supposed to illustrate that the force actually reverses next to the load spike in the middle created by that component. Not good (both the drawing and the resulting load distribution in real life).


Better solution: A clean cutout, nothing touching the component. The load on the PCB goes down right under the cut-out, obviously, but it's nothing near as dramatic as in the first illustration.


Best solution: A cutout that fits the component shape exactly. Now, this is rather hard to create, with the foam compressing by a somewhat unpredictable margin, but obviously it would be the theoretical ideal, resulting in a completely even load distribution.


Now, the ideal real-world solution would be somewhere between the second and third illustration - a cut-out that transfers some load onto the component, but probably not as much as would be required for an ideal load distribution, since it's much better to err in the direction of applying too little load. That means in general to cut out generously, so that the component doesn't touch the rubber at all while testing without torquing down the screws. When the foam is compressed, it should then transfer a light load onto the component, which will result in a rather nice and even load distribution onto the board.


Hope that helps somewhat and isn't just completely trivial.

Chris
Edited by decnet - 12/4/12 at 6:27am
post #4 of 6
Thread Starter 
I appreciate your effort and illustrations. I realize I can cut it out, how ever, the stock rubber is too thin to clear the modules. I was more or less curious if the compounds I mentioned would react with the PCB, and if anyone has "modded" their cooler mount. Looking at other heat sinks with a comparable mass, I found that some only use hard washers, which I assume are nylon to raise the flat plate, and presumably do not stress the PSB given the less area of contact. The exact MB is the EVGA z77 itx, and the specific coolers are the Noctua U9B, and d14 (based on performance of the U9B). Noctua does make a smaller cooler that does fit, just not with the Securfirm system. I suppose I am going to have to "play with it" to make it work. Shame on EVGA for the module placement, however, I am not a board designer.

EDIT: I lack the patience to illustrate. but will provide pics when complete. Thanks again.
    
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post #5 of 6
Oh, I see, you were asking mostly for the chemical compatibility of those rubber types with your PCB, sorry I got you wrong there, hope you didn't feel like I was patronizing. smile.gif Well, I'm absolutely no expert on that question from a theoretical POV, but from my practical knowledge, the question hasn't actually occurred to me - of all the (non-conductive!) crap I had touching PCBs over the years so far, ranging from natural wood through all kinds of tapes and paint to plastics and rubber, I figure that the latter would be one of the least problematic group of materials. Do you have any reason to believe that those rubber types would cause problems, and if so, what specifically?

From looking at a commercial applications guide, it seems to me that all types you mentioned except for butyl-based rubber are used in automotive engine and fuel system applications, which means they'd typically be subjected to contact with conductive and corrosion-affected metals, temperature ranges of -10 to +100°C and substances such as gasoline or lubricant oil, and are still able to perform, i.e. remain chemically unaltered over a considerable amount of time. I take it from there that butyl based is better suited for mechanical and/or cold applications, but can't cope with organic solvents that well - which probably aren't too much of a factor inside your computer case either. Viton is also used as electrical insulation material in it's own right, as is Neoprene (another common and cheap rubber type that I'd probably consider). I'd assume it will be quite safe to attach anything with those properties to the rear side of a glass-and-resin mainboard where it sits in a dry, warm place and is protected from direct sunlight, while being asked to distribute some quite negligable, entirely static loads and insulate against voltages no higher than 12V through several millimeters of material. Are you building a gaming-HTPC with that ITX board and a huge Nuctua cooler, btw?

Chris
Edited by decnet - 12/4/12 at 12:24pm
post #6 of 6
Thread Starter 
Neoprene is readily available to me, as are several others. Sounds like a good deal. Yes, my gaming requirements are not graphic intensive, ergo I do not need a healthy GPU, but I do need some for a few programs I use. As far as the heatsink, yes, I am going to try to put that Kg sink on the CPU as I am a firm believer in efficiency. By my math, it fits fine, sans the rear of the PCB. I am waiting on the board to do a mockup, but I think it will be fine.
    
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