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Why Are Printed Circuit Boards Usually Green? (2017)
- Eduardo3rd 8y agoInteresting example of a place where a small but meaningful advantage in a manual application (reduced eye strain during visual inspection) leads to a larger, nearly insurmountable advantage in a world where the task has been largely automated thanks to preexisting R&D/economies of scale. I expect we will see more and more of this in the coming decades across multiple industries. Anything else fit this pattern today?
- brianwawok 8y agoQWERTY keyboards? Built so mechanical typewriter keys would not hit. Used for computers.
- jsjohnst 8y ago> Built so mechanical typewriter keys would not hit. Most likely a myth. There’s tons of articles on it, but here’s one to get you started: https://www.smithsonianmag.com/arts-culture/fact-of-fiction-the-legend-of-the-qwerty-keyboard-49863249/ https://www.smithsonianmag.com/arts-culture/fact-of-fiction-...
- stan_rogers 8y agoThe authors of the paper seem to believe that the object would have been to slow down the typist (had the jamming hypothesis been correct). The opposite would have been true. Increase the difference of the angle of approach of successive hammers, and you decrease the chance of jamming and increase the speed. I'll admit that the Z-SE ("dot-dot-dot-space-dot" in early American Morse, with the length of the space/mark mkaing the difference) problem makes some superficial sense, but then there's a corresponding R-EI ("dot-space-dot-dot") and others that aren't reflected on the QUERTY keyboard. (The original Morse code needed far too much space-length discipline, which is why it was replaced fairly quickly, even in the NIH-heavy USA.)
- analog31 8y agoGUI. Small but meaningful advantage in a manual application: * Guiding the user to guide a complex machine through a precise sequence of steps in order to achieve a goal, such as reading mail or writing a letter Automation: * Natural language recognition, shell scripting Economy of scale: * Beautiful formatted text has lost its value due to being ubiquitous, and more and more document processing consists of copying and pasting in an e-mail program
- jacwah 8y agoThis reminds me of "The Calf-Path": https://www.poets.org/poetsorg/poem/calf-path https://www.poets.org/poetsorg/poem/calf-path
- the-dude 8y agoI have read somewhere else the US Army standarized on it.
- InGodsName 8y agoMy asus motherboard is brown colored.
- bluedino 8y agoSomewhere in the early 3D video card years, I took one out of the box and the PCB was red! Blew my mind. I want to say it was a Diamond card but I'm not 100% sure.
- SmellyGeekBoy 8y agoI have a GeForce 2 which is red, I think it's the earliest non-green card in my collection (2000-ish).
- wenc 8y agoAll Gravis Ultrasound cards were red (>1992ish). [1] It was partly a marketing choice, to make them stand out from conventional Sound Blaster cards. [1] https://en.wikipedia.org/wiki/Gravis_Ultrasound#Versions https://en.wikipedia.org/wiki/Gravis_Ultrasound#Versions
- mhd 8y agoYes, that's the first non-green PCB I can remember, too. And it took a while until I saw it become common -- I guess a big incentive was the appearance of side windows on PC cases. At first all DIY (Dremel), then commercially sold.
- greglindahl 8y agoOne of my startups was purchased by QLogic, which made PCI cards in bulk. One of their corporate standards is that prototypes have red PCBs, to prevent them ever being mixed together with production parts. These days I have some friends who have a particular debit card that's the same color of red. Every time I see it, I twitch.
- dkersten 8y agoI wonder if this is also why a lot of boards from eg sparkfun are red.
- pmorici 8y agoSparkfun does the red for branding. Their early stuff was green. They also use black for their SparkX experimental boards. Adafruit is know for their blue boards and oshpark for plurple it’s all branding.
- mhh__ 8y agoI would guess not, given that these days (At least in small quantities, which I assume scales) the choice of colour is aesthetic (To first order) rather than dictated economically.
- borgel 8y agoAt work we often try to do a different color for each revision so you can tell at a glance what's in a given unit. It's definitely saved me a few times!
- starky 8y agoWe use different solder mask colours to differentiate different product variants that share a board outline. It is way easier to tell a factory to install the red board when making a specific product variant than to have them read a part number off the board.
- pvarangot 8y agoWe started doing that but I think we ran out of colors pretty fast.
- msoad 8y agoApple PCBs are all black nowadays. They probably went all they to make the black pigmened oil as good as green.
- userbinator 8y agoI suspect it's a deliberate choice both as a fashion statement and to discourage repair. It's interesting to see a similar phenomenon with desktop PC motherboards: "gamer" or otherwise "enthusiast" boards are often a non-green colour and come with superfluous design elements (like plastic covers over the actual components, which sort of remind me of the engine covers on newer cars...), while both the ultra-cheap prebuilt and ultra-expensive server boards remain green and free of fluff.
- zrobotics 8y agoI blame case windows for this. The last desktop I built, it was a chore finding a case that didn't look stupid, and I eventually gave up on a normal motherboard, as anything with a z170 chip set looked like it belonged in a transformers toy. And while people definitely geek out over servers, it's nearly all about specs. After all, why make something that gets hidden away in a rack in a DC look pretty? I suspect that is one reason Apple isn't using green mask, since the connotation for many people is 'cheap'
- userbinator 8y agoIronically enough, case windows were created so people could show off the components inside, but now they're only showing off the covers on them.
- stephen_g 8y agoI doubt it has anything to do with repair. When you’ve got a 18 or so layer PCB, probably with microvias (invisible if they’re in pads), and very closely spaced QFN and BGA-packaged parts everywhere, soldermask colour is the least of your problems. So much of the design is on internal layers inside the board and so much interconnection to internal layers in pads (if using microvias) and under BGAs that being able to easily see the top and bottom layer traces easily would give you very little to go on. You’d really need design files to do anything more than just reflowing the odd part... It probably is a lot to do with fashion though. It’s literally one of the only reasons that I always specify blue or black soldermask at work - just looks a lot cooler. Green boards just have that late-90’s electronics look.
- deleted 8y ago[deleted]
- peterburkimsher 8y agoPinouts usually use red and black to indicate power and ground [1]. It's possible to use several colours of solder mask on the same PCB. [2] What I'd like to see is a developer board targeted at the education market that uses colours to show the traces. I think that at least showing the power and ground could reduce the risk of shortouts. It would be a lot easier for teachers to say "plug the red wire into the red pin" instead of "the top right ... no, other top, turn it around". [1] Raspberry Pi pinout https://cdn-images-1.medium.com/max/1000/1*QlSyHfcfNu4ePpNoNtKcZQ.jpeg https://cdn-images-1.medium.com/max/1000/1*QlSyHfcfNu4ePpNoN... [2] https://i2.wp.com/makezine.com/wp-content/uploads/2009/12/200912010746.jpg?resize=1200%2C670&strip=all&ssl=1 https://i2.wp.com/makezine.com/wp-content/uploads/2009/12/20...
- danellis 8y agoAlmost certainly a lot cheaper to just use keyed connectors.
- sannee 8y ago> It would be a lot easier for teachers to say "plug the red wire into the red pin" instead of "the top right ... no, other top, turn it around". Well blowing stuff up is part of the electronic learning experience isn't it? :)
- ultrasounder 8y agoIn various places I have worked we used Red color soldermask to indicate that the PCBAs were in early prototype stages(EVTs,DVTs) and once the final designs were released for manufacture(PVT) they were Green in color. This also was used to indicate that these boards were RoHS compliant. Again, this might have been very industry specific(Medical devices in my case) and YMMV. IN another FAANG place that I worked our ODMs who also worked with Chinese Fab houses started out with Green soldermask. Nowadays I find it fascianting that one can order preactically any solder mask color one chooses to, though i have a special affinity towards pink.
- jpm_sd 8y agoAt this point, they're usually green because they're usually green. It's the most common mask color, therefore the cheapest. Also, oddly enough, not only do different mask colors have different achievable resolutions (minimum line widths) - some colors don't stick to the PCB as well!
- userbinator 8y agoNote that in the early days of electronics, PCBs did not have soldermask, because it wasn't necessary: https://en.wikipedia.org/wiki/File:IBM_SMS_card_circuit_side.agr.jpg https://en.wikipedia.org/wiki/File:IBM_SMS_card_circuit_side...
- setquk 8y agoAlso lots of boards had transparent solder mask after that (Tektronix did this) which was great for debugging! Examples here: http://golddredgervideo.com/kc0wox/tek/7504/detailedpictures.htm http://golddredgervideo.com/kc0wox/tek/7504/detailedpictures... Whole scope is a work of art!
- userbinator 8y agoWow, gold everywhere. Even the ICs have gold-plated pins... that's not something I've seen before.
- dkersten 8y agoI’ve only seen one such circuit before and it was some kind of radiation hardened thing. It looked cool though!
- jacquesm 8y agoThey're beautiful. Good luck oxidizing any of that in normal environments, those scopes will outlast the people that built them. Old computer hardware used to be just like that, I would buy the boards by the pound in the 70's for parts. Gorgeous stuff.
- setquk 8y agoAnnoyingly the IC sockets tend to oxidise if the board doesn’t! I’ve lost count of the number of them I’ve had to replace in my life. If it wasn’t for mechanical switches, pots, contacts and some dubious thermal design I imagine the kit would last for 100 years easy. I have 40-50 year old stuff on my bench in daily use.
- lambda 8y agoI love that OSH Park (https://oshpark.com/ https://oshpark.com/) uses purple soldermask. It's a fairly unusual soldermask color, but they use only purple. It looks great with gold plating, and it gives a satisfying sense of branding to for open source hardware and prototyping.
- setquk 8y agoActually OSHpark boards I find are pretty crap. They have mouse bites left over, the mask is crap and the registration poor on some boards. Getting better boards from JLC but you lose HASL and purple.
- lambda 8y agoYeah, there are a lot more options for easy, small-batch prototyping PCBs these days. OSH Park was one of the first that was really easy and accessible to hobbyists, so even if it's not the best or the cheapest any more, the purple soldermask still has a place in my heart.
- ludwigvan 8y ago> 1. Green can relieve visual fatigue and aid in inspections > In the early days, due to technological restrictions, quality inspections relied on workers manually checking the boards with their bare eyes. Squinting at tiny circuits all days is tiring work, but neurologists and psychologists agree that the wavelength of green light has relaxing effects on the body and can reduce fatigue. Additionally, they have found that the sensors in human eyes, or cones, are most sensitive to green light. Therefore, the contrast is greater between the circuit traces, pads, silkscreen printing and empty spaces. Just by observing the boards from the outside, one can easily identify defects in the outer layers. Compare the below images of green boards to other colors such as blue, yellow or even black and white. With higher contrast, errors are easier to spot. Perhaps an IDE theme with a green background would be similarly helpful for programmers. Any particular suggestions?
- robterrell 8y agoThis research is why we were sold computers with green-colored phosphor monitors back in the 80s. I'm not going back, but if you're into it, maybe try: https://marketplace.visualstudio.com/items?itemName=gerane.Theme-Green https://marketplace.visualstudio.com/items?itemName=gerane.T...
- amelius 8y agoAt some point people started switching to amber. If above research is correct, then why was amber deemed preferable?
- aparks517 8y agoMy recollection is that it was mostly for brightness. I think the amber phosphor had shorter persistence and was less prone to burn-in as well. But yeah, kinda harsh on the eyes in comparison.
- spindle 8y agoI don't know why it was initially deemed preferable, but as a user it was really nice to have something different for a change.
- bsder 8y ago> Green solder mask is physically superior Possibly chemically. Practically? EVERY other solder mask color is better. I find that because green is the default, cheap, PCB soldermask, manufacturers thin it to hell and back in order to save money. As such, I regularly get coverage gaps over vias underneath QFN components which then short to the pad underneath the chip. (Manufacturing tip: if you can, only put vias underneath the chip that are tied to the same signal as the QFN thermal pad and your reliability will be much better.) If I want good soldermask coverage, I always order an alternate color (with the requisite expense) and almost always get great results.
- Sniffnoy 8y agoWhat this article doesn't answer is, when it talks about the green soldermask being physically superior, is that only because it's had more R&D put into it due to being popular, or would it actually be the best regardless? (Admittedly, I don't know how one would possibly answer that question without, like, actually trying to invent better soldermask of other colors. But it bugs me that the article doesn't even ask the question.)
- hwillis 8y agoSolder dams come down to a bunch of factors, but the bottom line is basically the best dye is the one that lets the resin cure stable and strong. For instance, white dyes are hard (for a lot of things) because white dye particles are large[1] and you need a lot of them. That means they can interfere with curing. Green dye can be relatively small amounts since green is so visible to the human eye, but afaik its more down to the fact that theyve been able to tune the dyes down better over time. [1]: also why you can't dye anodized aluminum white. Most dyes are colored at the molecular level, and are much smaller than the wavelengths they reflect. White dyes need to reflect every wavelength, and normal molecules only reflect quite narrow ranges where they resonate. In order to reflect white light you need particles at minimum the size of the wavelength. Then you need a range of particles for each wavelength. In practice this judt gives you black, since each particle will also be absorbing light at other wavelengths. You need one size of particle with fine, often fractal-like microstructure that has features at every size. That means white dye particles are hundreds of times larger than colored dyes.
- jacquesm 8y agoThank you. That answers a question I once had but could not get a satisfying answer to other than 'can't be done'.
- dboreham 8y agoNit, but I doubt silk screen mask is used much these days. When I was last involved with board production 20+ years ago all our vendors switched to photoimagable mask in order to get the registration accuracy and resolution necessary for fine lead SMT.
- deleted 8y ago[deleted]
- Andre607 8y agoThe article mentions that there are "even mixed color boards", does anyone have a photo of any? I did a cursory search and didn't see any, but am interested in how these looked.
- guan 8y agoI recall reading that the map of Italy on the back of an Arduino Uno is tendered using white solder mask, because traditional silk screens did not provide enough resolution.
- MrXOR 8y agoSoldermask is most commonly green in color but nearly any color is possible Another reasons: based on old military requirements and standard, UV (ultra-violet) sensitive photopolymers and LPISM technology patent story https://electronics.stackexchange.com/questions/82669/why-are-circuitboards-traditionally-green https://electronics.stackexchange.com/questions/82669/why-ar...