How to mount LED in a product front panel - Page 1
Forum section: electronics / general

author: VEGETA
author_rank: Super Contributor
timestamp: November 04, 2022, 01:17:58 am
content: Hello,kindly check the image here.I am interested into learning how to mount LEDs on front panel like this and which part from Digikey can be used? I know he uses PCBs as front and under panel while the design PCB itself (green color) is in between..more pics from here:https://www.axunworks.com/product-p341706.htmlthanks

author: ataradov
author_rank: Super Contributor
timestamp: November 04, 2022, 02:51:07 am
content: This is just standard 3.5 mm LEDs mounted on the green board and poking though the top cover.There is nothing like this that can be used with a single board and with an actual lens. But if you are ok with just a hole in the top panel PCB and light shining though, then you should search for reverse-mount LEDs. Some of them are flush with the mounting surface, some will sit in the hole and may end up being flush with the panel surface.Basically thishttps://dammedia.osram.info/media/img/osram-dam-2711021/s,x,760,y,0/00142087_0.jpgor thishttps://www.we-online.com/catalog/media/o135755v209%20Family_WL-SFRW.jpgAlthough some seem to be more attractive, may be even suitable for direct use without additional lenseshttps://www.digikey.com/en/product-highlight/s/sunled/1206-reverse-mount-with-inner-dome-lens

author: SiliconWizard
author_rank: Super Contributor
timestamp: November 04, 2022, 03:16:50 am
content: Mounting TH LEDs like this is an annoyance in terms of production (if you have any kind of production to do, now if it's just prototypes, who cares.)Usually easier to use SMD LEDs and light pipes to guide light to the front panel. Like this:https://www.lumex.com/lightpipe.html

author: ledtester
author_rank: Super Contributor
timestamp: November 04, 2022, 04:07:59 am
content: I've seen plastic spacers used to get the LED at exactly the correct height. Search for LED spacer/standoff or LED lamp holder.

author: ataradov
author_rank: Super Contributor
timestamp: November 04, 2022, 04:16:13 am
content: There are spacers, but then you will be running into an issue of designing your stuff around those spacers. Plus they are still annoying for mass production. Avoid if at all possible.

author: VEGETA
author_rank: Super Contributor
timestamp: November 04, 2022, 10:30:33 am
content: well, in my case the top cover PCB will be without any electric connections, just a matte black nice front panel. So I think it cannot host such reverse mounted LEDs.I thought of spacers but these will need me to put them and solder the LEDs by hand rather that assembling them in PCB assembly factory.Seems no option is perfect but I am ok with the result similar to picture in original post.

author: AndyBeez
author_rank: Frequent Contributor
timestamp: November 04, 2022, 11:23:28 am
content: What is the gap between the PCB and front panel surface?You might be able to use 'lighthouse' PTH led: about 10mm high with a 2mm end diameter. Or for a short distance, there are press on plastic lenses for SMT leds. Google "smd 5050 led lens"

author: Psi
author_rank: Super Contributor
timestamp: November 04, 2022, 11:27:33 am
content: If you leave copper and soldermask off the PCB in an area on top and bottom you can shine light through the PCB substrate. It actually works really well and allows you to light up a pattern or shape that you can define on the PCB.The PCB is diffuse enough that you don't get light hot spots.You can do it with LEDs on a separate PCB, or reverse mount LEDs on the back of the main PCB.You want to use high-intensity 20mA leds though, there's some light output loss in getting through the PCB.The diffuse PCB also works well if you want to mix color with an RGB led. the PLCC ones work great.If you want to see it i can dig out my old one and make a short video of it lighting up the logo.

author: VEGETA
author_rank: Super Contributor
timestamp: November 04, 2022, 11:46:24 am
content: I prefer traditional way of either through hole LED with spacer or reverse mount smt one... but the reverse mount have to be mounted at the bottom side of the top cover PCB which needs me to run wires from main PCB to it. is there any better way?how about just using regular through hole LED without spacer? just solder it and leave it. does it do any problem? i guess spacers are better.as for SMT reverse mount ones, as mentioned, it will require me to have wires going from main PCB to the bottom side of the top cover PCB. has anyone done this before? assuming the product will be similar to that of the picture, it will not be inside an enclosure but rather having top and bottom cover PCB panels.so assume I need 4 LEDs for indicating user choices... then I would need 4 power and 1 ground signal to run from main PCB to the bottom side of top panel PCB. the push button of choosing + the 4 LEDs will mostly be on the side not in the middle... so maybe I can have the wires coming from the middle of main PCB to middle of top cover PCB. then route them to the specified place on the bottom side of top PCB.this way the wires will be hidden away from the user. but the problem is in the assembly stage since it will be kinda hard to do such short wires. I hoped for a more neat and cheap solution.what do you think?

author: Kean
author_rank: Unknown
timestamp: November 04, 2022, 12:33:11 pm
content: In your original photo it looks like they are using standard 3mm through hole LEDs, and I suspect they have LED spacers in place to avoid the LED getting "pushed in". Common suppliers of these spacers are BIVAR and Essentra.If you are making the front panel with a PCB, then it makes sense to leverage that and use reverse mount LEDs, and use appropriate length board to board SMD connectors. You really don't want to be soldering wires between boards as that removes any assembly advantage of the reverse mount LEDs.You need to work out the trade off between soldering some through hole LEDs vs SMD assembly of a second PCB. Using an actively connected PCB for the front panel can certainly give you additional design options like capacitive touch buttons or better shielding.

author: VEGETA
author_rank: Super Contributor
timestamp: November 04, 2022, 12:56:40 pm
content: as for reverse mount LEDs... can't I just use a ribbon cable with good enough length then after soldering either bend it to place or loctite it?what type of connectors and cables are u suggesting?

author: sokoloff
author_rank: Super Contributor
timestamp: November 04, 2022, 01:13:46 pm
content: You could also consider something like spring contacts to electrically connect the boards and using the backside of the panel PCB to have traces and hold the resistor and LED.

author: Kean
author_rank: Unknown
timestamp: November 04, 2022, 02:32:06 pm
content: Quote from: VEGETA on November 04, 2022, 12:56:40 pmOf course you can use ribbon cable, but that would be an extra assembly task and time consuming. Is this a one off, or a production design?If I was designing it, I would be adding an SMD connector to the main PCB, and SMD pins to the rear of the front panel. Obviously they need to be properly aligned just like the mounting holes.Something like these (Harwin just as a quick example with pics, GCT, Samtec, etc are some other supplier options)https://www.harwin.com/products/M20-7810345/https://www.harwin.com/products/M20-8750342/You can get different height mating connectors to suit the required distance between the PCBs.

author: VEGETA
author_rank: Super Contributor
timestamp: November 04, 2022, 02:39:08 pm
content: Quote from: Kean on November 04, 2022, 02:32:06 pmyour suggestion is nice and can do the job for sure, not so expensive too.however, the design will have stand-offs and can also get rubber feet. now how to match the lengths of all those?? not easy.the design is still in, well, designing phase. but for sure going to be production one day.

author: Kean
author_rank: Unknown
timestamp: November 04, 2022, 02:53:45 pm
content: Those example Harwin parts are 3.75mm tall for the female connector, and 9.9mm tall for the male header.So those would suit 10mm or 11mm standoffs between the two PCBs, but versions of the male header can be found in a wide variety of lengths or even custom ordered if you have large enough requirements.That female connector also supports top or bottom entry, so you can have holes beneath the connector and let slightly longer header pins poke through to the other side of the PCB, or even mount the female connector on the back side of the lower PCB if that suits the design requirements better.There are heaps of other board-to-board connector choices depending on height, number of pins, and pitch/density requirements - but these types of 0.1" pitch are very common and cheap. And most importantly they are available in a huge range of pin count and heights/lengths.

author: AndyBeez
author_rank: Frequent Contributor
timestamp: November 04, 2022, 03:29:46 pm
content: So how and where are you having the front panel designed and manufactured?

author: VEGETA
author_rank: Super Contributor
timestamp: November 04, 2022, 03:35:57 pm
content: Quote from: AndyBeez on November 04, 2022, 03:29:46 pmwell right now i am about to have another design (dreamcast power supply) delivered to me so I can test it and so on... once I wrap this up then I will try to dig into this design we are speaking of.PCBs are made by PCBway, another option would be AllPCB. not going for others for price of course.both have Matte Black PCBs so that is fine. as for the main PCB it could be just regular black or even make the bottom PCB panel the main PCB if possible. I just need to put some rubber feet if you know any good and cheap ones.so the standoff should connect all these PCBs down to the rubber feet.It is the first time I am doing something like this, and it is kinda not cheap to keep getting boards here due to customs and shipping.

author: Jackster
author_rank: Frequent Contributor
timestamp: November 04, 2022, 04:37:19 pm
content: +1 for SMD LEDs with light pipes. Especially if your board is already 100% SMD. Don't want to add another process to your BOM (if this is a production run product).That and they look nice and keep crap from getting into the housing. Easier to assemble the product too.

author: VEGETA
author_rank: Super Contributor
timestamp: November 04, 2022, 04:59:39 pm
content: Quote from: Jackster on November 04, 2022, 04:37:19 pmcan you link to say a blue led with some 20mm light pipe? for reference. I assume they are installed by press fitting them right?reverse leds seem nice too, but i thought of using those suggested smt board to board connectors not just for the led signals... but for mounting the PCBs together instead of standoffs.like getting the appropriate female connectors with male pins, then put 4 of each corner plus 3 distributed in the middle for more sturdiness. anyone ever done that?

author: thm_w
author_rank: Super Contributor
timestamp: November 04, 2022, 09:26:44 pm
content: Quote from: ledtester on November 04, 2022, 04:07:59 amTons available. I think its a viable option:https://www.lcsc.com/products/Photoelectric-Accessories_958.htmlBut if you don't want to hand solder a few boards, SMD option also good. Can either get board mount, or one that presses/clips into the panel (would look nicer).https://www.aliexpress.us/item/2251832782960596.html

author: Jackster
author_rank: Frequent Contributor
timestamp: November 04, 2022, 09:39:07 pm
content: Quote from: VEGETA on November 04, 2022, 04:59:39 pmI got mine from VCC.https://vcclite.com/product-category/lightpipes/panelmountlinearlightpipes/Digikey has them all. Sadly they are in freedom units but you should manage to find something close.There are other brands that make them in metric.My light pipes end up being about 1mm away from the LEDs which is ideal.Yes they are press fit. I use hot glue on the other side though as my product gets abused. They sell little rubber things to go on the inside but I don't rate them.As for the LEDs I used, I picked them based on stock availability at the time. Wanted a full reel so that limited my selection in 2020.Any in the 0406-0603 range will do with 3-4mm light pipes.Reverse LEDs can be nice but you get crap in the hole and the LED gets blocked... As someone else suggested, get the PCB host to route most the way through the FR4 and use the last layer as a defuser. If done right, it looks nice. But not very bright. Good luck with that in daylight.

author: VEGETA
author_rank: Super Contributor
timestamp: November 04, 2022, 10:51:09 pm
content: sticking light pipes is another problem as well.by reverse leds i meant those which can stick out to be flush with the board. so I can dig a hole in pcb to fit it.

author: SiliconWizard
author_rank: Super Contributor
timestamp: November 05, 2022, 08:07:37 pm
content: Benefits of using SMD LEDs and light pipes, beyond making it cheaper/easier for production, is that they make it easier for waterproofing (or just dust protection), and they also avoid any direct mechanical coupling between the front panel and the PCB, which is way better in terms of long-term reliability.One alternative of course if you still prefer TH LEDs for any reason, is to mount them on a separate PCB which will be mounted close to the panel, and connect this PCB to the main PCB via a cable. Makes it easier for production and avoids directly mechanical coupling, at least to the main PCB. A bit more expensive, although a small LED PCB would be dead cheap in any kind of quantities.

author: VEGETA
author_rank: Super Contributor
timestamp: November 05, 2022, 08:28:54 pm
content: Quote from: SiliconWizard on November 05, 2022, 08:07:37 pmok, so light pipes are mounted on top of smt led (what size?) using pressing right?I saw this one for example:https://www.digikey.com/en/products/detail/bivar-inc/VLP-600-R/4926905so I need to make 3.1mm cut in the top pcb to fit this one... and on main pcb i need to do some cuts to press fit it? its 2 legs are 0.6mm of size, meaning 0.7mm holes?how can i couple the smt led with the light pipe though? to make sure light travels good and the pressing is very firm.and as a comparison, what kind of pricing between smt LED on main pcb + light pipe vs reverse mounted led on top pcb with smt board to board connectors? this is going to be a tough comparison i believe. i hope someone who tried them both to say his opinion and experience.and there is this "flexible" one too:https://www.digikey.com/en/products/detail/bivar-inc/LC-1-0/3091462but i guess the flexible one suits crammed designs where you need to route the pipe somewhere on another level, like from main pcb to a side panel.Quick comparison for 100 boards:Board to board connectors mentioned above + reverse LEDs = about 180$.SMT LEDs+ light pipe I mentioned = about 160$.is this ok or am i missing something?

author: ataradov
author_rank: Super Contributor
timestamp: November 05, 2022, 08:37:15 pm
content: Light pipes are mechanically mounted to the case and on the PCB side they just hover over the LED. That's the whole advantage - you do mechanical stuff separately from electrical stuff. Minor inaccuracies in LED positioning or board mount within the device won't matter.The specific one you link has alignment pins that would need alignment holes in the PCB. This is not how this is usually done. But I guess if you are working with off the shelf components, you have to deal with whatever you can get.And the description says "press fit", so I guess you are supposed to undersize the holes. But this does not sound interesting to me, I don't see how this is useful in any way. You will have more control with a through hole LED with a spacer. It makes more sense to me mechanically.

author: VEGETA
author_rank: Super Contributor
timestamp: November 05, 2022, 09:09:28 pm
content: Quote from: ataradov on November 05, 2022, 08:37:15 pmI think I am a bit lost.is the light pipe press fitted on top of the led itself on the main PCB, then peeks through the case? or press fitting on the case? I cannot imagine how to press fit it on the case without it being able to be pushed inside... the one i linked has 2 little pipes which I assumed they need to be press fitted in the main pcb.please correct me.if i ever gonna go with these light pipes, then smd leds are the choice not through hole ones.if through holes to be used then we need to see how to fit them firmly on both sides.I actually prefer smaller size led\pipe to be peeking on top so I am ok with very small diameter ones if available.

author: ataradov
author_rank: Super Contributor
timestamp: November 05, 2022, 09:25:10 pm
content: Usually light pipes are fixed to the case and don't even physically touch the LEDs. They don't have to be press fit, they may be mounted any way you like or suits your application. There is a picture in this thread of them being glued to the case.Yes, the whole point of using light pipes is that you can use SMD LEDs.I personally would design things around through hole LEDs and regular holes in the case. Only go with light pipes if you are making a custom case and a custom light pipe design. Off the shelf light pipes make no sense to me in most cases, you still have to design your stuff around a fixed product, so might as well design around the LEDs themselves.If alignment becomes challenging, it is far cheaper to make (3D print) alignment tool, or even custom spacers. They don't have to be pretty, since they will be inside the case.

author: Jackster
author_rank: Frequent Contributor
timestamp: November 05, 2022, 09:26:41 pm
content: They press fit into your case and hover 1-2mm above the SMD led.They don't go all the way through as there is a mushroom cap on the top to prevent this.That is why in my assembly photo, I have added some glue to stop them coming back out the same way I pushed them in.The datasheet for the ones I linked show how they fit in as well as the profile.

author: VEGETA
author_rank: Super Contributor
timestamp: November 05, 2022, 09:41:51 pm
content: I don't want any type of manual gluing stuff, no hot glue or anything.so for through hole leds... you use those plastic stand-offs which have 2 holes for the LED legs? and pick the appropriate standoff size? this way it becomes firm but you would still need to match the lengths with the pcb stand-offs themselves.I was hoping for some light pipes that would stick to the main board for much easier installation... then it would peek a bit out of the top panel while being firmly installed on main pcb. i can't find why it does not work this way.Is there any pictures of real products available to demonstrate this? I saw many teardowns but couldn't see an example, or i wasn't interested to notice it.

author: mariush
author_rank: Super Contributor
timestamp: November 05, 2022, 09:45:00 pm
content: Digikey also has some things in the Optoelectronics - Lenses or SpacersFor example, a transparent lens cap that you can press fit from above and then insert through hole led from the other side :https://www.digikey.com/en/products/detail/keystone-electronics/8659/317087They also have them in various colors , here's the whole list :https://www.digikey.com/short/dd1j0mz3And here's a red example :https://www.digikey.com/en/products/detail/keystone-electronics/8668/317093or another red :https://www.digikey.com/en/products/detail/visual-communications-company-vcc/SMB-200-RTP/4515614You could potentially also check the light bar category, as there are there pieces with 2 or more leds in a case that you could in theory glue to the top pcb/case, or maybe have some thermal/adhesive pad/ some pad between the base pcb and the led bar to keep the led bar pressed into the top coverExample of such led bar with 2 red leds :https://www.digikey.com/en/products/detail/kingbright/WP934EB-2ID/1747693Check the Panel indicators / Panel lights as well , and even the LED spacer sections - maybe you'd find spacers just the right height and in big enough stock that you could get them cheaply.

author: ataradov
author_rank: Super Contributor
timestamp: November 05, 2022, 09:51:47 pm
content: Quote from: VEGETA on November 05, 2022, 09:41:51 pmYou may not need the standoff. The challenge with LEDs like this is to mount them straight and at the right height. Once this done they don't need to be supported. So, how you approach this depends on the design. If LEDs are in the tight spot where no removable jig can be placed, then you would probably have to use a standoff. Otherwise you can design a spacer that you use during assembly and then remove.Quote from: VEGETA on November 05, 2022, 09:41:51 pmThe one you linked is press fit into the PCB. You would still need to design some tool to make sure it is inserted perpendicular to the PCB, but it might work.The idea here is to order some of the tings you think may work and experiment. It is hard to tell what may or may not work in your case.Quote from: VEGETA on November 05, 2022, 09:41:51 pmDemonstrate what?

author: VEGETA
author_rank: Super Contributor
timestamp: November 06, 2022, 08:40:02 am
content: I believe the press fit lenses are ok if managed correctly, then the through hole led does not need any standoff or spacer... just soldered and inserted.Still, the press fit pipes into the main pcb seem the best overall but i also need to make sure when i press it down it does not touch or squeeze the smt led itself. also the size of the led...etc. the drawings does not include all info and i could not find 3d model to check.I need for now a blue light, so getting a blue smd led with clear pipe of vise versa. what type of smt led works well with the pipe i listed above do you think? for example this led:https://www.digikey.com/en/products/detail/harvatek-corporation/B1931NB-20C007614U1930/15861263Quoteif you solder them and let them peek from the case or top pcb, i guess they can be pressed down or move if not supported by a standoff or spacer.Quotewhy a tool?it has 2 legs where you press them till they both click. no way it won't be perpendicular i guess. but my concert is the space for the led is it enough? and what sizes of leds are supported.Quotewell, i might just finish the design, then order a prototype board from pcbway to test its main function... along with that i let them buy a couple of those stuff to test them as you said.Quotei meant pictures to show all these options we talked about in real product for more clearer picture for someone like me who never done them before

author: PlainName
author_rank: Super Contributor
timestamp: November 06, 2022, 05:17:55 pm
content: These are the light pipes I used for a project some time ago: Tru Opto LPC060CTP.Basically you drill a hole in the case and push these through. There's a lip which stops them going all the way through, and a spring clip on the other side stops them coming back out. Ten second job to mount. LED on the PCB sits under the light pipe and the result is a nice diffuse light on the panel with no hole for nasty stuff to get inside. Use with SMD or PTH LEDs as the whim takes you.There are many other similar. A lot of light pipes mount on the PCB but that means they can't fill the hole in the front panel (easily - in theory they could be the tolerance would have to be fine enough that they would be a pain to assemble). Generally, those types have a hole with a light behind and don't look quite as neat.

author: ataradov
author_rank: Super Contributor
timestamp: November 06, 2022, 05:19:43 pm
content: Quote from: VEGETA on November 06, 2022, 08:40:02 amNo idea, you will have to experiment.Quote from: VEGETA on November 06, 2022, 08:40:02 amAgain, you are theorizing this, but have you tried? This method is used a lot and it works fine. It also depends on how tall your LED/light pipe needs to be.Quote from: VEGETA on November 06, 2022, 08:40:02 amIt is very long, at this length minor misalignment would result in quite a bit of misalignment at the top. Regular LEDs have a domed shape and can generally align themselves quite well. Light pipes with flat top may be more frustrating to assemble. If you pick a light pipe with rounded top or just a short one, it would probably be fine.But I really see no reason to use a light pipe here.It seems just strange to me. Usually you use light pipes if your outside indicator shape is unconventional or the geometry is such that you can't do it with a simple trough hole LED.But if you are considering this straight light pipe, then just use a regular LED. Especially if you are not assembling a lot of those boards, since LED part would need to be mounted by hand.Quote from: VEGETA on November 06, 2022, 08:40:02 amIt is hard to think of particular products right away. Here is one example where light pipes make sense :https://des.gbtcdn.com/uploads/2015/201504/heditor/201504061001509379.JPG/https://www.tag-connect.com/wp-content/uploads/2021/06/ulink-pro-case-opened-with-tc2030-ctx-debug-programming-cable-installed.jpgYou can see outside indicators of unconventional shape, they would be impossible with regular LEDs.Of course, a big advantage of light pipes, even the simple ones is that you may not want to have people with any soldering skills doing final assembly. In case of a light pipe only mechanical assembly is required, and this mya be easier. But this is something I would worry about if I'm making more than 1000 of something. For smaller quantities, I can't see how it would be worth it.