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Author Topic: MXM graphics card module upgrade (heatsink)  (Read 1229 times)

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Offline kat

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MXM graphics card module upgrade (heatsink)
« on: February 22, 2018, 08:17:33 AM »
The process below relates to making a simple custom heatsink for an ATI/AMD 6700M MXM graphics card (an AMD 5950M recognised by Windows 10 as an 6700M) with limited tools, to fit inside a HP Elitedesk 800 G1 USDT (Ultra-Small/Slim Desk Top) computer (system uses the same/similar MXM module configuration typical of mobile workstation or laptop video card upgrades - note also, MXM type II graphics cards only fit MXM mounting slots, they cannot be fitted to internal/laptop pci express slots). Notwithstanding the heat-sink itself, to actually run an MXM graphics card a 180W external power adapter was needed (Part No. #613766-001 or alternatively #613766-002) as the original 135W results in a POST error relating to power shortages (not enough).

Parts used/needed;
- AMD/nVidia Type III MXM card[1].
- Copper or aluminium plate or sheet[2].
- 40 x 40 x 30mm aluminium heatsink[3].
- 3M double-sided thermal adhesive pad/tape[4].
- CPU/GPU thermal pad/s (silicone)[5].

Optionally;
- Machine screws/bolts; M2 (2mm x 8mm) and M1.6 (1.6mm x 5mm)[6].

Tools used for the job
- junior hacksaw with metal blade.
- standard bastard file for metal.
- needle files (round).
- 2mm drill bit for metal.
- pin-vice.
- wet-n-dry fine grit.
- craft knife.
- scissors.

Making the heat-sink
To keep the process as simple as possible, the plan is to mount the aluminium heatsink square on a section of plate that’s cut to size and drilled so it can be mounted to the MXM module mounting posts on the motherboard (M1.6 screws). To avoid waste and keep the amount of work to a minimum, the baseplate will first be draw to size on a sheet of paper or thin card. This will then be cut out, placed on the metal sheet, which will be marked and cut based on this template, mounting holes included.

The basic MXM heatsink with aluminium block and copper baseplate

First mark the mounting holes to determine base-plate actual size.
The simplest way to do this is use the MXM graphics card mounting bracket on the underside of the board (if the MXM board has no mounting bracket use the holes the bracket will attach to). Hold a piece of paper over the bracket (board underside) and poke holes where the mounts are. Double-check position and alignment (cf. #1 below).

Holes puched in paper to double-check measurements for baseplate

With holes punched, the distance between them should be;

 - 46mm centre-to-centre

Using at minimum a 2mm drill-bit to match the M2 mounting bolts/screws, this makes the inside edge-to-edge measurement 44mm (or 43mm nominally), with an outside edge-to-edge of 48mm[7] (or 49mm nominally) (cf. below).

Basic measurements for the copper baseplate - 46mm centre-to-centre, 56x56mm

Knowing MXM specific mounting hole size (not the same as typically expected for ATI/AMD graphics cards) and placement the heatsink plate can be drawn relative to the MXM graphics cards overall size and the GPU’s position on the board[8].
Using 2mm thick copper or aluminium plate[9] (1.2mm minimum) and the centre-to-centre mounting hole distance of 46mm, add another 5mm hole-centre to outside edge, making the plate 56mm x 56mm[10] overall (5mm from hole-centre to outside plate edge). This forms the template and should look similar to the image below;

Paper and card templates used to draw/scribe copper baseplate

Once drawn, the MXM heatsink template can be cut out and transferred.
Double-checks measurements after initial layout then cut paper or card template using a craft knife and straightedge or steel ruler. Place on copper or aluminium plate and mark or scribe the baseplates outline and centre-punch the mounting holes [11] (spray-glue may help here).

The basic heatsink baseplate marked on 2mm thick copper plate

Cut to shape and drill mounting holes.
Using a metal cutting saw cut as close to the outside edge of the heatsink as possible (the outer border)[12] to minimise the amount of excess material that needs to be removed. Once cut, confirm the mounting hole centres are clearly punched, drill using a 2mm or 3mm drill-bit for metal[13]. Finish up using a metal file to finalise the shape, remove any heavily scribed lines or marks on the upper surface with wet-n-dry sanding paper or other abrasive.

Cooper (2mm) baseplate scribed, drilled and sized

Clean, de-oxidise and de-grease surfaces.
To make sure the heat-resistant double-sided tape sticks the aluminium heat-sink block and baseplate firmly together clean and de-grease using surface cleaners and/or alcohol[14] – this is critical for lasting adhesion. Apply the tape to the underside of the heatsink block – cut to shape/size and/or trim excess where needed. Centre the block over the plate and press down firmly[15]. The MXM heatsink unit is now ready to install.

The basic MXM cooling unit with aluminium heatsink block and copper baseplate

Installing the custom MXM heat-sink.
The final step is to install the heat-sink unit to the MXM graphics card module. Apply thermal grease to the GPU, alternatively use a silicone thermal pad. Position the heat-sink and fasten using standard M2 bolt/screws – although pressure ensures a tight fit between GPU chip and heat-sink be mindful of gaps that may form when fastening pressure is unevenly applied[16].

The custom made MXM heatsink installed in a HP 800 G1 USDT
Hardware properties of AMD Catalyst in Windows 10

Does the MXM heatsink work?
In a word, yes. Performace boost will differ depending on the module installed but they should generally be greater than embedded GPU chipsets. Unless installing an MXM card to run multiple monitors, the addition of an MXM graphics card does mean the system had two effective graphics units, or rather two GPU's, the MXM module and embedded Intel-based chipset that came with the system. This may cause conflicts (power issues notwithstanding), which can generally be solved disabling the embedded GPU in faviour of the unit on the MXM card.

Why make a heatsink?
Wouldn't it be cheaper to just buy a heatsink?. Ordinarily yes, if MXM graphics cards used standard fittings. As they don't nothing off-the-shelf fits; either mounting holes are too far apart or too close together, often by a millimetre or two, or stock heatsinks are too large to fit inside the confines a the USDT case/format, a similar issue as might be found in some server rack units where custom heatsinks need to be made to accommodate and cool server graphics cards.


Footnotes:
[1] although "Type III" MXM graphics cards may physically fit the available MXM motherboard slot, they may not be hardware or Operating system compatible, a condition that might not be discovered until booting up.

[2] metal plate or sheet material for baseplate should be a minimum thickness of 1.2mm to limit distortion and flexing – thicker material can be used but will typically affect ease of production.

[3] heatsink dimensions are largely determined by the height from GPU to underside of the case lid, and reduced width/depth as allowed for access to mounting holes – larger prefabbed heatsinks can be used but will need altering to allow for mounting point access.

[4] thermal tape is often used to ‘stick’ heatsinks to chips mitigating mounting pins and brackets. Success depends explicitly on clean surfaces. Thermal adhesives are not the same as silicon heatsink pads that aid heat transfer between surfaces.

[5] thermal pads made from silicone should be preferred to thermal past as the spongy resistance is used to ‘tension’ the heatsink once mounted instead of springs as might normally be used.

[6] to mount the heatsink itself to the MXM bracket the same type of M2 screws/bolts used in laptops can be used. To mount the MXM card itself to the motherboard MXM mounts M1.6 screws/bolts are needed. These requirements may vary depending on motherboard and card mounting brackets or posts.

[7] as the holes related to M2 threaded bolts/screws they will need to be slightly larger to ensure the mounting bolts have wiggle room if needed to fit the mounting plate. Drilled with a 3mm bit, or a 2mm then expanded using a needle file, either/or subject to availability, this makes the inside edge-to-edge measurement between 44mm (maximum) to 45mm (minimum) – ideally 44.5mm, and/or an outside edge-to-edge of 47mm (minimum) to 48mm (maximum) – ideally 47.5mm.

[8] ] GPU chip placement is not always centred within the space defined by the brocket and holes, or perpendicular to the MXM board edges.

[9] baseplate should be a minimum of 1.2mm thick to minimise flexing when fastened to the MXM mounting bracket.

[10] the size described here is based on defining an area that allows enough room to fully support the mounting holes without undue bending or twisting of the plate (depending on plate thickness and tempering) – the heatsink baseplate could be made large or smaller depending on the space available and/or whether partially or fully covered other onboard chips and modules is possible (they don’t obstruct the baseplate).

[11] it will be easier to mark or scribe around a card version of the template using an indelible pen, fine-line marker, or pointed object. If scribing, initial markings should be light so corrections can be made with relative ease.

[12] depending on the metal used for the base plate, use a powered, ‘junior’ or full-sized hacksaw with metal-cutting blade (teeth close together). To be absolutely sure of mounting hole placement, positioned the MXM card on top of the plate and marked down through the holes double-checking their position relative to those marked. Do this before cutting out the raw baseplate.

[13] drill one hole and double-check the diagonal (e.g. bottom-left to top-right) for placement and accuracy before drilling the opposite corner. To allow some wiggle room, use of a 3mm bit is recommended else holes may be too tight (alternatively a needle file can used to clean up or widen the holes). Countersink holes to de-burr.

[14] for copper plate in particular use Brasso or similar branded or off-brand, mild abrasive, surface cleaner/metal polish before clearing any residue with (isopropyl) alcohol or nail-polish remover.

[15] use a table and once positioned, apply full weight to the unit for a moment to ensure absolutely fast adhesion. Test by checking for any play or wiggle – if tape comes unstuck the surfaces would not properly cleaned and prepared.

[16] ideally fasteners should be spring loaded in that a long bolt is fastened to the mounting bracket under the MXM board which is then tensioned by the presence of compression springs. Unfortunately, these types of fittings are not readily available for MXM cards so the use of silicon thermal pads is recommended to provide adequate thermal transfer and compressive resistance to the downward pressure of the fixings that are used.

Offline kat

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Re: MXM graphics card module upgrade (heatsink)
« Reply #1 on: September 14, 2018, 06:52:17 PM »
To update this topic on making a custom heatsink for a proprietary MXM card (grrrr). The initial version, whilst it worked, was limited in a number of ways that meant once the card starts to cycle up, the heat dissipation couldn't properly take advantage of the rear case fan. A design that could do this was needed.

So version two, a copper plate (a little larger than version one) was utilised extending the base closer to the fan, onto which a set of 0.2mm copper fins were bonded (heat resistant epoxy putty). Each fin plate was bent around a 2mm stainless steel plate making the overall width approx. 3mm. A series of these were bonding c.5mm from one another. The end result worked better that the first but the fins had contact issues due to using epoxy putty, which caused gapping and uneven transitions from plate to fins. So, another version was made bonded with resin epoxy.

Version two of the MXM heat sink extended the copper base so one side of the 0.2mm dissipation fins were next to the rear case fan for more direct air flow.

Version three was an improvement to version two, taking the same basic principle and extending it a little, slightly modified base and more fins bonded using a heat resistant resin-based epoxy with a slightly longer set time to allow in-place adjustments.

A simple but more stable bending rig was use (claps and bench rig rather than using fingers to manually bend plate) to shape the copper blanks around a 2mm precision-ground tool-steel blank (hardened steel so it won't bend). This gave each fin much sharper bottom edges. Once fins are shaped they're bonded into place propped up with a steel set-square to ensure reasonable squared-ness whilst the epoxy sets (shorter fins are cut and formed to accommodate bracket screws in the corners of the plate).

Once installed into the machine a makeshift cowl was made from corrugated cardboard that fit over the entire heatsink, end butting up to the rear case fan to force airflow the the tunnel this creates and over the dissipation fins. Works surprisingly well considering (not shown below).

Copper dissipation bending rig for the 0.2mm fins - copper sheet bent around 2mm precision-ground tool-steel blank.

Fins propped-up whilst epoxy sets hard enough for it to support weight of fins. Set-square ensures they stand upright, match-sticks to fix the distance (which just happened to be the right tool for the job).

Final custom built MXM heatsink installed (sans cardboard cowl). Spring-tension that keeps the plate in place for good heat transfer is created using 1mm silicon thermal pad between chip and heatsink base.

 

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