Manufactorer for flexible aluminum PCBs / bending aluminum PCBs - Page 1
Forum section: electronics / general

author: stefan_o
author_rank: Regular Contributor
timestamp: December 27, 2024, 07:08:22 pm
content: Hi,I want to get a LED stripe board manufactured (small quantity) on aluminum. The boards should be able to bend (radius 8cm) without any issue.Some manufacturers advertise with that:https://www.pcbonline.com/blog/flexible-aluminum-pcb.htmlBut I couldn't find anybody offering online quotes for that kind of boards (I suppose when I need to contact them for a quote it will be either very expensive or they won't do prototype/small quantities at all)As 8cm radius is not that much I think also thin standard aluminum PCBs could work, but again I couldn't find anyone with a thickness under 0.8mm (pcbway offers 0.4mm in theory, but when you select that no price can be calculated).Anybody has any experience with flexible aluminum PCBs or what standard aluminum PCBs are suited for what maximum bending radius?Best regardsStefan

author: Jackster
author_rank: Frequent Contributor
timestamp: December 27, 2024, 07:16:12 pm
content: You can do some quite ridiculous bends with the thin aluminium boards. I think the traces have to be a bit wider as you will get some deformation in the copper layer but not that much at that radius.I have seen some boards with something like a 2-3mm radius bending at 90°.I would get some test boards made up with copper traces of various thicknesses and run some bend tests before doing anything though.I am also sure I have seen aluminium boards with rigid flex if you are worried about it.

author: stefan_o
author_rank: Regular Contributor
timestamp: December 27, 2024, 07:34:53 pm
content: I have tried with some standard aluminum boards I still had lying around (1mm thickness, 1cm board width), they are not that easy to bend precisely. I don't want them bend them "somehow" but into a nice circle, and 1mm thickness seems a bit much for that.

author: thm_w
author_rank: Super Contributor
timestamp: December 27, 2024, 08:06:06 pm
content: I'm guessing its just very thin aluminum. JLC does down to 0.8mm, probably not thin enough. PCBway does 0.4 or 0.6mm those might be good. Just ask them for a quote, this is obviously a niche spec.What components are you planning to use? They must be small otherwise they will crack and fall off the board.Probably can use FPC instead, why are you thinking the aluminum is required?

author: stefan_o
author_rank: Regular Contributor
timestamp: December 27, 2024, 09:04:54 pm
content: Quote from: thm_w on December 27, 2024, 08:06:06 pmPCBway is quite expensive compared to JLC (about 3 times the cost at 0.8mm aluminum for my board size) and for 0.4mm I won't show any cost, so I assume it's either not available at the moment or not for small amounts (same for PCBgogo).Quote from: thm_w on December 27, 2024, 08:06:06 pmIt's just 17 leds (2835, Cree J series), two resistors (1206) and four solder points (= a LED stripe designed for 48V). I oriented all LEDs and resistors that the two pads are perpendicular to the bending direction, hoping to reduce the stress put on the components/solder jointsQuote from: thm_w on December 27, 2024, 08:06:06 pmMost important reason: Aluminum is quite easy to solder: "Just" apply the the solder paste and position the components, but it on the stove (electric ceramic glass top, not induction), as soon as the solder starts melting turn off the stove and carefully move the PCB to the side. Very easy, worked perfectly for me in the past. For FPC it's a lot more complicated to solder and also more expensive to produce.Additionally aluminum has better heat dissipation from the LEDs.

author: thm_w
author_rank: Super Contributor
timestamp: December 27, 2024, 09:52:56 pm
content: FPC you can make large copper planes, I suspect the heat dissipation difference would not be massive. But I have not tested it.For soldering you can use cheap aluminum hot plate:https://www.aliexpress.us/item/3256808030102461.htmlor put a aluminum sheet on your stove and slide it out of the way, if you are really budget limited..You can see similar commercial product, its white but I think it was FPC?:

author: stefan_o
author_rank: Regular Contributor
timestamp: December 27, 2024, 10:38:13 pm
content: Quote from: thm_w on December 27, 2024, 09:52:56 pmDo you have another link or a product name (search for "aluminum hot plate" gives a diverse list of various products)? For me it shows "Sorry, the page you requested can not be found:(" (I tried changing location/currency to Canada)Quote from: thm_w on December 27, 2024, 09:52:56 pmNot sure what it is, for FPC it looks very stiff

author: thm_w
author_rank: Super Contributor
timestamp: December 28, 2024, 12:06:19 am
content: Google search 500W hot plate, or see ebay here:https://www.ebay.com/itm/226269868371Lots of ali stuff is blocked in germany.The reason I say its FPC is because you can see the white tracks on the back. I can't see that happening with aluminum, it should be silver.JLC does 0.1 to 0.2mm FPC, you could probably find thicker and it would be quite stiff.How many watts dissipation are we talking? The clive one did not get warm at all, but was only ~2.5W.

author: stefan_o
author_rank: Regular Contributor
timestamp: December 28, 2024, 03:42:54 am
content: Quote from: thm_w on December 28, 2024, 12:06:19 amThanks, I also found a lot of those a lot cheaper on Aliexpress now (maybe, Aliexpress costs are a bit random, could be different once you proceed to checkout)Quote from: thm_w on December 28, 2024, 12:06:19 amA single PCB (about 7mm x 150mm) will be about 4W, so a lot more heat than the one Clive disassembled while being a lot smaller. But I think the LEDs are quite efficient, I remember I calculated with the spectrum given in the datasheet the theoretical maximum lm/W and the LEDs reached a little over 60% of that. Considering some light will be absorbed by the PCB and losses in the traces and the two (very small resistors), it will be about 2W of heat.As JLCPCB has a greyed-out option for 0.4mm aluminum PCBs, I contacted them and asked under what circumstance 0.4mm aluminum PCB is available, the answer was not at all at the moment. I assume the other companies with online ordering use the same fab to produce the aluminum PCBs, considering all other options are the same and they cannot give a quote for 0.4mm/0.6mm.I just checked my old order and the PCBs I tested for bending are actually 1.2mm not 1mm, so maybe 0.8mm does work. I think I'll order them in 0.8mm aluminum, the stencil is the most expensive part anyway, so if it doesn't work I'll order some flex pcbs and already have the stencil.

author: mtwieg
author_rank: Frequent Contributor
timestamp: December 28, 2024, 02:16:45 pm
content: The concept of a "bendable" aluminum PCB is quite strange to me. A "flexible" aluminum PCB (as in meant for repeated flexing) sounds like nonsense, I'm not aware of any aluminum alloys suitable for such a thing.Why not just start with a standard aluminum PCB (before assembling components on it) and machine it from the backside with channels/grooves to allow bending at specific places (i.e. not near large SMT components). You'd have to do some math to ensure that the copper traces won't be excessively strained. Perhaps having other aluminum alloys would help with this, but for an 8cm radius I'm betting you don't need such a thing.Using a much thinner aluminum substrate and bending it as a continuous arc seems like a poor idea. You'd be straining all the SMT components and sacrificing thermal performance.

author: stefan_o
author_rank: Regular Contributor
timestamp: December 28, 2024, 05:20:19 pm
content: Quote from: mtwieg on December 28, 2024, 02:16:45 pmManufacturers call it flexible aluminum. But the description states it is not intended for regular flexible use, but rather bending it into a special shape.Quote from: mtwieg on December 28, 2024, 02:16:45 pmYes, I also thought about that and hoped that you could order the PCB directly with that (one-sided v-grooves and defined places), but that doesn't seem possible, and I don't have the tools to make the grooves myself (at least not easily, I could manually do it with a saw).Quote from: mtwieg on December 28, 2024, 02:16:45 pmI'm bending in a way that the components are on the inside, so I don't thing I'll put too much stress on the traces and only minimal on the components, as they are all perpendicular towards the bending direction (pads will not change distance due to bending).

author: mtwieg
author_rank: Frequent Contributor
timestamp: December 30, 2024, 02:47:49 pm
content: Quote from: stefan_o on December 28, 2024, 05:20:19 pmThe website you linked seems to show a photo of such a thing, so I assume it's within their capabilities, see here:https://cdn.pcbonline.com/icon/bendable-aluminum-substratepcb.webpI doubt this would be something you could quote via an automated process, though. It's not the kind of thing one can simply define through gerber files. Would have to make a separate drawing for them to review.QuoteSounds good. How do you intend to attach the board? If you intend to bend it "in place" you may need quite a bit of force holding it down (especially if you're relying on heat conducting to whatever it's mounted to). Might need a jig to pre-form the assembled PCBA before putting it in the final assembly.

author: stefan_o
author_rank: Regular Contributor
timestamp: December 30, 2024, 03:39:26 pm
content: Quote from: mtwieg on December 30, 2024, 02:47:49 pmIt would certainly be possible (just use a separte gerber layer for that), but I assume this is not common enough that implementing that is worth the effort, especially if the production process is not automated.Quote from: mtwieg on December 30, 2024, 02:47:49 pmI will attach the boards to the enclosure with heat-conducting glue. As the LEDs directly face a the side of a diffuser disk, the boards can also go nowhere. My intention is to either bend them in place, leave them for a few hours too check that they don't bend back if the remain correct, glue them down, otherwise repeat bending process.

author: jpanhalt
author_rank: Super Contributor
timestamp: December 30, 2024, 05:48:13 pm
content: As for recommended minimum bend radius, this table might help:https://www.cumberlandmetals.com/aluminum/minimum-bend-radii/You need to know the alloy for hardened versions, but for soft alloys, you can approximate.Precise bends are most easily done with a press brake rather the common box and pan brake. For aluminum and small runs, the press can be made from mild steel. With a box and pan brake, you can control the radius by adding waste sheets on top of what you are bending. Of course, you need to set the top die back accordingly. With practice and dry runs, you can get pretty close.