Aluminum PCB, dauble layer - Page 1
Forum section: electronics / projects

author: elektrinis
author_rank: Regular Contributor
timestamp: March 22, 2011, 06:31:51 pm
content: Hello to everyone. I have a question here to those who had ever built something on Aluminum PCB. That is:Thing is, I'm designing a power module with SMD mosfets (IRF3107-7, 240A 75V) and think that aluminum board would be the best way to cool it off (I need to make it very small).The problem is that I need two layers and the lower layer should be exposed on some regions of the board (for better thermal conductivity).Has someone been here already and can recommend a PCB manufacturer? This is not a "one-time hobby" project, I will need to make over 100 pcs. of these, when the design is perfected.If interested, I am currently here:

author: Fraser
author_rank: Super Contributor
timestamp: March 22, 2011, 06:47:03 pm
content: With the thermal conductivity of aluminium almost half that of copper, could you not use a copper heat sink design that is more conventional and efficient ?

author: elektrinis
author_rank: Regular Contributor
timestamp: March 22, 2011, 06:50:24 pm
content: Quote from: Aurora on March 22, 2011, 06:47:03 pmThis is not a heatsink. It's a part of PCB, that is being screwed on to heatsink. Just like "star" LED's are done:

author: Fraser
author_rank: Super Contributor
timestamp: March 22, 2011, 07:04:53 pm
content: Hmmm Ok but in that case copper is still a better medium for the efficient transfer of heat between the thermal sources and the heatsink to which the PCB will be attached.IMHO aluminium (aluminum) is a compromise thermal dissipation material used either for low weight or lower cost than copper. Copper is king when it comes to transfering or radiating heat away from a source, which is why laptop heat pipes are usually copper. For even better performance Silver or Gold could be used but that just gets sillyI am only questioning the use of an aluminium/copper composite PCB because I would expect a copper multi layer PCB to be an easier fabrication process and it would permit the easy creation of multi-layer copper thermal transfer couplers (feed-throughs) to the copper heatsink interface layer.

author: elektrinis
author_rank: Regular Contributor
timestamp: March 22, 2011, 07:09:30 pm
content: Quote from: Aurora on March 22, 2011, 07:04:53 pmActually silly is that we are discussing about thermal conductivity when the question is about who can manufacture what I need. I've done some calculations and aluminum plate will be good enough. Aluminum is easier to manufacture and by it self it is cheaper. Also anodized aluminum is corrosion-proof.Anyway, if you can point me to manufacturer who makes copper-based PCBs, please do. Otherwise this discussion is pointless.

author: Zero999
author_rank: Super Contributor
timestamp: March 22, 2011, 07:10:01 pm
content: Quote from: Aurora on March 22, 2011, 07:04:53 pmCopper is nearly three times heavier and more expensive than aluminium.I find the most effective form of heatsinking is to solder the tab of the device to a piece of copper busbar which is then mounted to an aluminium heat sink with the electrical insulating material sandwiched in-between. The small piece of copper reduces the thermal resistance by spreading the heat across a larger area of electrical insulation to a larger area of aluminium which is used as the bulk heat to air transfer medium.

author: elektrinis
author_rank: Regular Contributor
timestamp: March 22, 2011, 07:12:52 pm
content: Quote from: Hero999 on March 22, 2011, 07:10:01 pmYes, this is my backup plan. But it involves complicated assembly and bulkier design. My designs involves multiple transistors these copper bars would be a pain in the arse. I need mine plain and simple.

author: Fraser
author_rank: Super Contributor
timestamp: March 22, 2011, 07:15:33 pm
content: elektrinis,Fair enough, pointless it is.Have fun getting it made

author: squeezee
author_rank: Contributor
timestamp: March 23, 2011, 09:27:03 am
content: Quote from: elektrinis on March 22, 2011, 07:12:52 pmIf an aluminum PCB is adequate; Wouldn't a thin aluminum plate covering all the transistors with athermal interface materialinbetween be enough?

author: elektrinis
author_rank: Regular Contributor
timestamp: March 23, 2011, 09:33:32 am
content: Quote from: squeezee on March 23, 2011, 09:27:03 amIf I understood you correctly, you are suggesting to mount SMD transistors on standard PCB and then glue on a heatsink on top of them? If so, unfortunately, this method is no good. I have to dissipate 300W from these six transistors. I'd like to solder them on aluminum-based PCB and then put it on heatsink or water cooling system.I've got some quatations from PCB manufacturers, but... price for two PCBs is over 1'000 USD (35 USD @ 100 pcs). This is way too much.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: March 23, 2011, 10:00:05 am
content: If you can get it down to a single layer then you can use a standard process - Eurocircuits amongst others offer a prototyping service on aluminium.However 300W is a lot of power (Is that dissipated power or output power?), and you'll need more than an aluminium PCB to acheive that in a small space.

author: elektrinis
author_rank: Regular Contributor
timestamp: March 23, 2011, 11:15:37 am
content: Quote from: mikeselectricstuff on March 23, 2011, 10:00:05 amUnfortunately no, this design is not possible on one layer, as I have many power traces crossing over. But I will try to think of a solution. Thank you for link, will check them out.Quote from: mikeselectricstuff on March 23, 2011, 10:00:05 am300W is a peak power dissipation in worst case scenario. The power in output is over 10kW.I think that 300W of dissipated power is not that big deal. Transistors with 2cm² footprint manage to do that. My overall aluminum PCB footprint will be over 40cm², so I don't see a problem here. Of cause, 300W in term of natural convection heatsink size is a big deal (for this footprint), but I will attach it to big aluminum chassis or use water cooling. Other components (motor for example) are water-cooled anyway.

author: PsI-On
author_rank: Contributor
timestamp: March 23, 2011, 12:03:15 pm
content: Can you get your Power devices or an equivalent in a traditional package?

author: elektrinis
author_rank: Regular Contributor
timestamp: March 23, 2011, 12:08:42 pm
content: Quote from: PsI-On on March 23, 2011, 12:03:15 pmI can, but that would increase overall size twice. Size and weight are very important to this design. Cost - not so much.

author: Jimmy
author_rank: Regular Contributor
timestamp: March 25, 2011, 11:35:37 am
content: Tryhttp://www.pcbco.com.au/pcb_al-back.htmlIs this for a home project or is this your job.Reason I ask is because the disapative heat from the ices would be 2.2kw

author: elektrinis
author_rank: Regular Contributor
timestamp: March 25, 2011, 12:17:45 pm
content: Quote from: Jimmy on March 25, 2011, 11:35:37 amThanksQuote from: Jimmy on March 25, 2011, 11:35:37 amHow did you get this value?

author: FreeThinker
author_rank: Frequent Contributor
timestamp: March 25, 2011, 03:21:13 pm
content: Just my 2C but would you not have problems withA. Thermal creep? seems that the design is quite high power and copper / aluminium would expand at different rates.b. Chemical reaction between the aluminium and copper interface? I know from experience that aluminium busbars in a power distribution can corrode quite badly when copper lugs are used (or vice versa) Denso paste was used to reduce the effect.

author: elektrinis
author_rank: Regular Contributor
timestamp: March 25, 2011, 03:24:43 pm
content: A: Copper layer is very thin. Will risk it. Also, temperatures will not swing that badly.B: There is no contact between aluminum and copper. You've missed the concept of aluminum PCB.

author: FreeThinker
author_rank: Frequent Contributor
timestamp: March 25, 2011, 05:44:33 pm
content: Quote from: elektrinis on March 25, 2011, 03:24:43 pmI've not missed the point of aluminium pcb's I've not got a clue about them. <off to google>

author: metalphreak
author_rank: Frequent Contributor
timestamp: March 28, 2011, 03:33:44 pm
content: http://www.goldphoenixpcb.biz/products.phpSays they do aluminium boards. You'll have to email them for prices though.

author: scrat
author_rank: Frequent Contributor
timestamp: March 28, 2011, 09:49:00 pm
content: It seems it is possible to manufacture double layer Insulated Metal Substrate, the first place I find is here:http://www.aitechnology.com/products/thermalinterface/thermclads/.

author: pcb_manufacturer
author_rank: Newbie
timestamp: April 23, 2011, 09:16:12 am
content: Copper is nearly three times heavier and more expensive than aluminium PCB.The small piece of copper reduces the thermal resistance by spreading the heat across a larger area of electrical insulation to a larger area of aluminium which is used as the bulk heat to air transfer medium.

author: Psi
author_rank: Super Contributor
timestamp: November 14, 2013, 01:04:43 pm
content: Maybe you should get a diamond PCB

author: owiecc
author_rank: Frequent Contributor
timestamp: November 14, 2013, 02:14:28 pm
content: This is quite strange stack-up. It will be quite expensive. Why not put the transistors on a DCB or single sided aluminum PBC and put the rest on a daughter board and connect them with bondwires? I have a picture somewhere of an old Grundfoss power module which uses this method.Are you really sure you want to do this kind of layout. All passives and ICs will be working at highly elevated temperatures because they will be seating directly on the heatsink. There is a reason why power modules today are made as a single housing and all gate drivers and control go over that.

author: Niklas
author_rank: Frequent Contributor
timestamp: November 14, 2013, 09:43:59 pm
content: Perhaps check with Wuerth in Germany about their PCB service. They seem to make small series of FR4 with thermal vias that is laminated onto an aluminum substrate. Here is a link to their design guide about thermal sensitive PCBs:http://we-online.com/web/en/index.php/show/media/04_leiterplatte/2012_2/w_rmemanagement/2012_DesignGuide_Heatsink_Poster.pdf

author: Rufus
author_rank: Super Contributor
timestamp: November 14, 2013, 10:36:00 pm
content: This thread is 2 and half years old, I think the OP has worked it out or given up by now.

author: tszaboo
author_rank: Super Contributor
timestamp: November 15, 2013, 08:35:33 pm
content: I'm still glat that it came up.It is called ALUMINIUM. Please. This is from the urban dictionary:"How the entire world (except the Americans) say aluminium.Why?Because that's how it's spelled."Not to mention, that PCB is not made from it. It is made from Alumina substrate, which is aluminium oxide.And having a two layer IMS board (because that is how it is called. Insulated metal substrate) completely against the cause. You need one layer, because it needs to be thermally coupled with the alumina substrate.Grr.

author: Corporate666
author_rank: Unknown
timestamp: November 17, 2013, 12:47:56 am
content: Quote from: NANDBlog on November 15, 2013, 08:35:33 pmIncorrect.Aluminum is just as correct as aluminium. Our periodic table lists the metal "Al" as "Aluminum". It's not just an incorrect pronunciation.As for the original question, I realize it's quite old, but MyroPCB and UltimatePCB both offer aluminum PCB's. I haven't done (or seen, actually) a stack up with two layers on top of each other on one side of a metal core PCB, but I have done two sided metal core PCB's before.For extremely demanding applications, check out Sinkpad. They have a technique where they etch down into the copper then put a dielectric and your traces - this leaves the unetched areas of the coppers at the same level as the rest of your solder pads. And you can reflow the heat tabs of electrically isolated devices directly to these copper pads, which means they are directly connected to the substrate without going through a dielectric.More expensive than normla MCPCB's but not outrageously so - very useful for highly demanding thermal applications.

author: Claudia
author_rank: Newbie
timestamp: December 23, 2013, 03:48:43 am
content: For aluminium PCB , I summarize other names as followaluminum PCBAlu PCBMetal core PCBIMS (Insulated Metallic Substrate) circuit boards

author: mrflibble
author_rank: Super Contributor
timestamp: December 23, 2013, 06:24:26 am
content: Quote from: Corporate666 on November 17, 2013, 12:47:56 amSo in case of doubt just go with the IUPAC standard for the element name which is, you guessed it ... aluminium.And to stay a bit more on topic ... does anyone know of affordable MCPCB manufacturers a la itead/seeed that makes 10 pieces for a doable price? I've looked for MCPCB manufacturers about 1 year ago and then it was a bit too expensive for me. So I ended up doing double layer board riddled with thermal vias. But maybe MCPCB prices have come down be now?

author: tszaboo
author_rank: Super Contributor
timestamp: December 23, 2013, 11:01:07 am
content: Eurocircuits makes IMS PCB pooling. Of course you have to #define affordable.

author: mrflibble
author_rank: Super Contributor
timestamp: December 23, 2013, 11:12:33 am
content: Quote from: NANDBlog on December 23, 2013, 11:01:07 amFair enough. Let's say ~ 2x price of regular double layer, so $40 for 10 pieces of 10cm x 10cm.Edit:Just did aquick calcand the above comes to ~ 200 euro. So, almost the desired price.

author: tszaboo
author_rank: Super Contributor
timestamp: December 23, 2013, 01:24:07 pm
content: That price is only available if you order hundreds of the board. Or you have to go to PRC. But I doubt they use the same quality base material, which is really important for IMS, i think.