DIY PCB fab with UV laser engraver - need router/drilling machine - Page 1
Forum section: electronics / general

author: rx8pilot
author_rank: Super Contributor
timestamp: August 19, 2016, 06:37:33 pm
content: I am considering an experiment to make DIY PCBs. The goal/purpose of DIY is primarily to make fixtures for tests and assembly as well as working out various circuit designs that cannot be bread-boarded.The technical needs are modest - double side, no mask, no silk. Not sure what minimum trace width I can get away with, but nothing crazy. With all that out of the way - I have reviewed all the usual DIY PCB methods out there (even made a few when I was a kid). They are all too time consuming and/or fiddly to be interesting until I considered the option of using my Epilog laser marking machine to replace the transparencies, toner transfer, exposure part of the process. The laser can go up to 1200dpi and have a dot circle of around .003" / .076mm.I was thinking that I just buy pre-sensitized PCBs, put them in the laser, out of the laser into developer and etching. On paper, it sounds fast and easy but I may be naive about what it is really like. I saw a YT video where someone did a PCB in a similar way - looks like a good idea since I already have the high resolution laser system which is the majority of the cost.https://youtu.be/4SNkzoOvoD8Also, one of the goals is to be able to deal with the fact that the majority of my PCBs are not squares. If I am going to work out a prototype shape with connectors, wiring, hardware and full assembly testing before sending for fab - I would need a router to both cut the outline as well as drill the holes. Any recommends for a reasonable quality router with very high-speed spindle would be good. There are a ton of super cheap, super crappy/fiddly options out there. It would be nice to have a step-up from the bottom, but not a super amazing top-of-the-line model either. The reason I would like to have this capability is because my last project was 7 PCB's interconnected in a very small enclosure. I did my best to 3D model everything including fasteners, but until I build a few with real parts, hardware, and wires - it was not known if it could be assembled. Tiny details matter and being able to quickly spit out 5-10 PCB shapes to optimize production assembly process would be a great time saver. Even the fastest PCB fab is a few days and at that speed it is top price of at least a few hundred per pass between the fab and overnight shipping. If I have 4-5 interconnecting designs, it could be significantly more money in addition to the time.I may be crazy, but this seems cheap to try. Any tips from those that have done any of this would be great to hear.

author: rob77
author_rank: Super Contributor
timestamp: August 19, 2016, 08:01:53 pm
content: forget toner transfer and forget the positive pre-sentised boards....definitely go for negative dry photo-resist - RISTON, you will need a 1200DPI printer, print the negative of the board to polyester transparencies and use a really powerful UV lamp. you will be surprised what fine details you can achieve that way(results on par with PCB houses)of course you have to use genuine riston photoresist and use the polyester transparencies for printing... with fake riston and printing to paper + spray making the paper transparent you'll get much worse results.i personally use :photoresist: DuPont Riston T215 MV3507Atransparencies: RAYFILM matt polyester R1060.1123Asolder mask: ROHM&HAAS - Dynamask 5000UV lamp: 15x 3W UV LED (PROLIGHT OPTO PM2L-3LLS-SD) in a array of 3x5 with 5cm spacing (5-10 seconds for the photoresist and same for initial exposure of solder mask - then approx 1-2 minutes for final curing of solder mask)both photoresist and solder mask are negative and the only chemicals (except etching) you'll need is washing soda Na2CO3 to develop both photoresist and solder mask and sodium hydroxide NaOH to remove photoresist after etching.

author: rx8pilot
author_rank: Super Contributor
timestamp: August 19, 2016, 08:55:56 pm
content: The critical goal is to not use transparencies and traditional photo exposure - but use the UV from a high resolution laser to directly expose the photo resist.Step 1: Put phto-resist PCB directly in laser machine.Step 2: DevelopStep 3: EtchWhy do you not like the positive pre-sensitised PCB's? Is there a limitation with them? I can send positive or negative on the laser system with the click of the button so choosing the best photo-chemical option. One of the reasons I was looking at the pre-sensitized is for speed. At the end of the day - this is for a business so labor is a significant consideration. As few steps as possible and designing a process that almost anyone can do is best (ideal).Did you watch the video above?

author: rob77
author_rank: Super Contributor
timestamp: August 19, 2016, 09:17:55 pm
content: positive is very unforgiving - if you have a 10micrometer crack in your transparency then you'll end up with a 10um crack in the photoresist and even wider crack after etching because with positive you basically destroying the photoresist with UV, so any imperfection in the transparency will result in holes and cracks in traces. if you'll use direct imaging as you describe then it's the same - any reflected/scattered UV light form you UV source will damage the surrounding resist.furthermore any level of overexposure means start over, with presintized boards it's a big waste.another disadvantage of positive presintized is the developer solution - it's sodium hydroxide... 3% solution is developing the resist while more concentrated hydroxide is removing the resistwith negative method you're curing the photo resit so any imperfection in mask or scattered/reflected UV will just partially cure the surrounding resist - and you can easily compensate for that during developing the resist.. you simply keep it a bit longer in the developer solution (washing soda) and monitor it till the unwanted half-exposed artifacts are gone. the fully cured resist won't go anywhere it's rock solid so you can developing the board for ages. i saved once a significantly overexposed board (was lazy to laminate a new one - but would be faster to laminate a new resist) by developing it for something like 15-20 minutesand if you really mess it up then just remove the resist with NaOH , clean and rinse the board, laminate a new resist onto it (with a standard unmodified office laminator) and repeat

author: rx8pilot
author_rank: Super Contributor
timestamp: August 19, 2016, 09:27:14 pm
content: Good info! Thanks.Exposure will be an experiment for sure. I was thinking that i can make a repeating difficult to etch pattern and use various power levels to do a test - I could do a whole bunch of patterns on a single PCB. After it is done, I can decide which one is best and document it. The nice thing about the laser is that it is consistent. Once I find the exposure level that works - it will not vary by any significant amount.How much effort is it to prep a bare clad with the photo resist you are talking about? Is that fairly easy and quick?

author: rob77
author_rank: Super Contributor
timestamp: August 19, 2016, 09:41:11 pm
content: yes it's very quick, just clean the copper , cut the resist film slightly bigger than the clad, peel of the protective coating from the photoresist film, place the clad onto a sheet of paper , place the film onto the clad - make sure there are no bubles underneth the film and laminate it with a office laminator (paper is needed to avoid the excess photoresist sticking to the laminator's drum) . whole process is approx 1 minute for me (after some practicing of course).some people like to place the film onto the clad submersed in water - it's much easier to avoid air bubles that way.

author: Aodhan145
author_rank: Frequent Contributor
timestamp: August 20, 2016, 12:42:27 am
content: I have experimented with a number of ways. I now only do simple one sided boards with toner because it takes no effort. The other ones you need to put effort in to. I am interested in the laser method. I will watch the video later as I have no saftey glasses currently to watch it with and I don't want my eyes to be damaged.

author: TJ232
author_rank: Frequent Contributor
timestamp: August 20, 2016, 04:27:39 am
content: "I will watch the video later as I have no saftey glasses currently to watch it with and I don't want my eyes to be damaged. "Huh? You must be kidding, right?

author: rx8pilot
author_rank: Super Contributor
timestamp: August 20, 2016, 04:30:53 am
content: Quote from: TJ232 on August 20, 2016, 04:27:39 amExcellent joke for a nerd audience, I think.

author: rx8pilot
author_rank: Super Contributor
timestamp: August 20, 2016, 06:01:37 am
content: Trying to find a source for the DuPont dry film here in the USA. No luck yet.Any ideas where to find it in small quantities?Sent from my horrible mobile....

author: rob77
author_rank: Super Contributor
timestamp: August 20, 2016, 07:28:51 am
content: Quote from: rx8pilot on August 20, 2016, 06:01:37 ami'm buying it from a local pcb manufacturer who happens to have a webshop selling raw materials . and i just realized they have another webshop in English language:http://pcb-diy.com/other types of negative dry photoresist films might (and will) work great as well, so you can test those available in your area, it's not that expensive (usually 1meter length of 30cm wide roll is approx 2-5Eur).and also you can try to buy some from e-bay , if you get a good one which works flawlessly then you have your supplier

author: Ammar
author_rank: Regular Contributor
timestamp: August 20, 2016, 07:57:28 am
content: If you are doing lots of odd shaped PCBs you could go for a milling machine. The quick circuit variety work well and the tools go down to .125 mm. You can then change the tool to cut out the shape. Only catch is they tend to be a few grand. But they are super quick for prototyping and save a whole lot of mess.

author: rob77
author_rank: Super Contributor
timestamp: August 20, 2016, 08:15:05 am
content: Quote from: Ammar on August 20, 2016, 07:57:28 amthey save a whole lot of mess while making another whole lot of different mess0.125mm tool means not enough detail, if you're lucky you'll get something like 0,25mm details with that (10/10 spacing) and that's not enough. furthermore that 0,25mm detail is dancing on the edge, so it will be more like 15/15 or even 20/20 (that's usable for easy boards with DIL and SOI packages though)and don't forget... if you will not use isolation routing, then you will mill the board for ages... several hours of noise and FR4 dust ? thanks i'll stay with my 30 minutes per board including solder mask (end-to-end and regardless of size).

author: rx8pilot
author_rank: Super Contributor
timestamp: August 20, 2016, 04:11:04 pm
content: Isolation milling will not likely fit my needs as well as the hyrbrid photochemical and router-drill approach. From all accounts including what is written above, its quick and is not impacted by geometric complexity of the PCB layout.As for routing and drilling, I have not yet found a decent CNC option. Not sure what brands or vendors to look at. Like I said earlier, I don't want to mess around with a DIY or random eBay thing. As always, finding a middle of the road option is difficult. They all seem to be toys/crap or over-the-top professional/expensive. The Cirqoid seems like the nicest one I have seen and is within my budget range.Sent from my horrible mobile....

author: Aodhan145
author_rank: Frequent Contributor
timestamp: August 20, 2016, 07:55:47 pm
content: Quote from: rx8pilot on August 20, 2016, 04:11:04 pmThis is why I am going to build my own CNC some time in the next two years.

author: l0wside
author_rank: Regular Contributor
timestamp: August 22, 2016, 07:55:03 am
content: If I get you correctly, you are planning to etch the PCB tracks and use a router only for the outer shape. This is about as simple as it gets for a router. Only 2D, and soft material (1.6mm of FR4 is nothing compared to some mm of steel). A Shapeoko might do.Disclaimer: I do not have a router. I just had been looking around to get one for this exact purpose, but could not (yet) justify the cost and the space.Max

author: tszaboo
author_rank: Super Contributor
timestamp: August 22, 2016, 08:06:23 am
content: I can order 5 PCBs (say 80*100mm) without soldermask, with milling, drilling, with 2 day delivery for 200 EUR. I day 277 EUR. Do you really think that your time invested in this is worth less? Say, you make it in 4 hours, and 30% is your material and equipment cost. In that case you can save something less than 35 EUR minus your wage. And you are working with toxic stuff, which gives you cancer or can make you a vegan or worse. Is it worth it?

author: rx8pilot
author_rank: Super Contributor
timestamp: August 22, 2016, 04:35:06 pm
content: Quote from: NANDBlog on August 22, 2016, 08:06:23 amI am hoping that I can be in the neighborhood of 1 hour end-to-end with a direct imaging and dedicated-process engineered setup. Maybe 2 hours? I don't really know since I have not made PCB's. The goal is less about saving the money spent on proto boards and more about saving the 2-3 days to get them.CASE (0)Over the past year, there have been dozens of opportunities that are measured in hours - not days for my little business. Most of those are little modifications and add-ons to our existing products. All of them can be accomplished by putting 10-15 parts on a 2-layer PCB, testing it, and shipping. Generally the details of the problem are not known until the customer needs it and they only need it right then. If I tell them that it will take 4 days - no deal. If I can ship the next day, it's a deal. The revenue from the custom add-on is not the goal either - the juicy bit is that they purchased a dozen of our main products because of the simple function added by the fast turn PCB circuit.CASE (1)Analog circuit shake-down during design. When I am designing something new I would really like the confidence gained by building sections of the circuit as I go to reduce iterations. Ideally, I would be able to cycle through 3 iterations of the circuit in a single day including build and test. The same iterations would take 2 weeks and $750-$1000 waiting for the various PCB houses after including the rush fees and overnight shipping. The time savings during design is what I am after which is much more expensive than the PCB fabrication.CASE (2)Fixtures. Test and assembly fixtures have totally transformed my validation and assembly process. The problem is that all of my fixtures are crazy dremel hack jobs that take a long time to build and are so odd that I cannot expect others to use them. I would like to be able to design and build various test and assembly fixtures while I am testing and assembling and the issues are fresh. I can iterate the fixture design quickly and get something that is worthy of production in hours (hopefully).So - the goal is to save time not PCB fab cost, although the direct costs of building simple PCB's in house is rather modest even if I spend a few thousand $ on a router. Keep in mind I already own the laser system and it is used for many other things. In theory, the only things I need to buy are the basic supplies and a router with it's supplies and dust control (guessing about $3-4k total for that). When I have people that I am paying and customers that are waiting, time is very valuable. If a system like this can save a single day, it could pay for itself. I suspect that if designed well - it can do much better than that. Like my pick and place assembly system - it sits doing nothing most of the time. When it is needed - it becomes VERY valuable to have in-house.Quote from: l0wside on August 22, 2016, 07:55:03 amThis is closer to my area of expertise since I owned and operated a high-end machine shop for a long time. The geometry for PCB routing and drilling is very simple as you point out. The challenge is mainly in the spindle where very high speed and VERY good runout is very important. I would hope to route with smaller than .062" (~1.5mm) and drill down to .015" (.4mm) if possible. A sloppy spindle, and sloppy frame will snap those tools all day long. In addition to that, XY motion has to be smooth to avoid tools breaking. The bigger the tools, the sloppier the machine can be. Almost everything in PCB manufacturing uses tiny tools - making the price go way up. I also won't be able to deal with some fiddly DIY software interface where it requires some custom Python program to translate something on a Linux box to finally create the motion code (I am just making things up to illustrate). Hoping for the solution that gets from the PCB design to the router with as few steps as possible - that may cost a little more. Since this project is oriented toward a business, I cannot be too risky. It should work the vast majority of the time and not be so DIY that I am the only one that can operate it.I hope that at least makes the intentions clear. The reason I started the thread is to learn from others that have done this so that I can make an informed decision about whether or not I am being realistic. If I take out the router and just do some tests at my old CNC shop - it will be very cheap to try. That may help understand if it will be worth going all in. The cost of purchasing the pieces is only half the cost too - the time it takes for me to learn, design, and setup the process will be at least double the cost of the equipment/router.

author: rob77
author_rank: Super Contributor
timestamp: August 22, 2016, 04:37:53 pm
content: Quote from: NANDBlog on August 22, 2016, 08:06:23 amyou're far far away regarding the costyour 30% estimate is way too high... 5 boards 80x100 without soldermask is something like ~ 6-7 Eur in material (including copper clad fr4, photoresist, etching) + add some cost for milling & drilling (upto 2-3 eur max) + add cost for riveted vias at approx 0.02 Eur/piece (replacement for through-hole plating)... so you'll see it's more like 12Eur in material for those 5 boards in total (considering 20 vias per board)... so 12 euros and few hours of your labor ... savings are HUGE. even with solder-mask and chemical tin plating it will be something like 15-16 eur in total.

author: tszaboo
author_rank: Super Contributor
timestamp: August 22, 2016, 05:46:44 pm
content: Quote from: rob77 link=topic=72832.msg1009886#msg1009886Quote from: NANDBlog on August 22, 2016, 08:06:23 amAdd that 3000 EUR for the milling machine, and another few thousand for the laser engraver, and another few for the other equipment. Say total 10 000. Divide down for some few hundred batch of 1-5 boards made with the setup over the next few years.OK, probably a cavemen can do it with a cheap rock hammer, but equipment cost is going to be large. And dont underestime labour cost. USSA salary is some 5 times as much as in the USSR.QuoteI usually laser print the layout, stick it on a cardboard, and cut the shape with a scalpel. Works quite well, TH connectors get a hole punched, SMD gets double sided tape.

author: rx8pilot
author_rank: Super Contributor
timestamp: August 22, 2016, 06:27:52 pm
content: I already have the laser system that does other work as well so that helps a lot.Quote from: NANDBlog on August 22, 2016, 05:46:44 pmI am guessing I will do 25-30 year or so. Since I live/work in California - I am all too familiar with crazy wages for simple work. If all goes well - this could give me a better way to keep people busy with productive work. Not the PCB's but the opportunities gained from making the PCB's in a short period of time.Opportunity cost is what I am shooting for. Think about this, I customer contacted me over the weekend and needs a special configuration of what we make. Since I have the P&P machine sitting right next to me, I can modify the assembly board by board and have it done in an hour. The customer needs this on Tuesday (tomorrow) morning or the need evaporates and they will go after something different. The total sale is about $3k - but only if I deliver in 1 day. I am hoping to capture more of that odd ball business $3k-$5k at a time that hinges on some simple but obscure circuit add-on. At that point I don't really care so much about the cost of the materials or a few hours of labor. The time waiting for the PCB house is the killer, NOT the cost of the PCB. If I need something in hours to enable a $4k sale - the PCB house just cost me $4k since they cannot get me a PCB in 3 hours. All of a sudden, the $3k for the router and even another few $k on other things seems like cheap money. Of course that is only true if I can make this a reliable process. If it is a total pain in the ass and always takes 3 tries, etc - I would re-consider for sure. I do not expect the first dozen PCBs to be great or fast. After a reasonable learning curve is the time to evaluate whether it is worth it or not. That is when I could start making promises to a real customer without getting myself in trouble.Quote from: NANDBlog on August 22, 2016, 05:46:44 pmRight now, I do this with our existing laser machine and acrylic. Not too bad for for pure mechanical tests and it literally takes about 5min per PCB to cut it out. Making a working/partially PCB is a big bonus. Especially one that I can properly solder things to instead of glue.

author: MT
author_rank: Super Contributor
timestamp: August 23, 2016, 12:58:58 am
content: Sad there still not a single 2 layer PCB printers around, only DIY on old Epson's and the faff of curing pigment, etc, no what i want is a 2 layer printer that uses same sticky crap as positive photo resist is made of without being photosensitive.Maybe indian/chinese ink could work, its sticky stuff particularly the shellac based?!The key to getting things to stick to various surfaces is its free energies and metals tend to have very high surface free energies while polymers and ceramics are quite low. So surface preparation is one key but i wonder if the manufacturers of positive resist uses roll of resist and flame activationor spray and spin thing something?!I dont give a crap it would take 15 minutes to print, 5 minutes to dry, its still faster and cheaper then 3-6 days from china.Speaking of which, spin coating liquid materials used in wafer fabs:Poly(methyl methacrylate) (PMMA), Poly(methyl glutarimide) (PMGI) ,Phenol formaldehyde resin (DNQ/Novolac), SU-8,OSTE PolymersAparently these folks do it.http://www.microchem.com/PriElex.htm

author: bicc1306
author_rank: Contributor
timestamp: August 23, 2016, 05:27:07 am
content: I really like the PCB fab with UV laser engraver video.I actually don't no much about PCB, but looking to learn more.