Multi layer, dual sided PCB Printer. - Page 1
Forum section: electronics / projects

author: excitedbox
author_rank: Regular Contributor
timestamp: April 27, 2019, 05:35:48 am
content: I am starting development on a PCB Prototyping 3d Printer and wanted to start this thread as a place where I could post questions I may have and updates for those interested as the project develops.The current options for prototyping PCBs are messy, time consuming or expensive, especially for multilayered boards. The current approaches for 3D printers are very expensive and way out of the range of most small businesses or hobbyists and the CNC approach is slow with low quality results.The final goal is to have the Makerbot of PCB printers in the form factor of an office laser jet printer. In my opinion the maker bot was the first real low cost option for the hobbyist to have a 3D printer and kicked the maker movement into high gear.My plan is to build a custom printer using UV cure inks for solder masks and non-conductive layers and flash sintering of copper or silver inks for traces. The printer will also contain a tiny spindle to drill through holes to the other side through the substrate before the printing process.Objective:The Objective will be to develop a Printer that can create multilayered, dual sided PCBs faster, cheaper, cleaner than current methods without human intervention throughout the printing process.Requirements:- Cost Less than $3000 for base unit.- Trace width of .1mm- Multi layer and Dual sided- No etching chemicals- No slow CNC milling- Max 15 min per Layer for 10x10cm PCB- Printing on FR4- Non intervention printing start to end.Obstacles:- Ink development- Ink storage life- Print quality on non flat substrates- Dust from drilling operation- Speed Speed Speed- Print head selection- Ink delivery system- Sintering- UV curing- Project Funding (I have done a ton of research that I will start compiling/organizing and adding over the next week or so as I get time.When I came up with the idea for this project I first considered many other options besides printing from the mild to the down right crazy. I considered foil stamping, milling, lasers, laminating, sand blasting (the test result was quite interesting but messy), robotic/automated etching, depositing etching gels, etc. Eventually I settled on printing because it is already done with good results but the prices are too high ($50-300k).I am also looking for help/participants and funding (sponsors/partners) for this project if anyone is interested. Once a prototype is developed I want to make a Kickstarter to get them manufactured and sell them.

author: Rerouter
author_rank: Super Contributor
timestamp: April 27, 2019, 05:58:26 am
content: How strong is the adhesion of your flash sintered inkAre you able to use this process to create plated via's, including out of order blind vias, e.g. 1-2 + 2-3 + 3-4is the 0.1 dependent on the ink jet, or on the positioning tolerance of the machine

author: excitedbox
author_rank: Regular Contributor
timestamp: April 29, 2019, 12:21:12 am
content: The trace size is dependent on several factors but mostly the positioning and DPI of the print head. Inks will also play a roll but as long as you have an unbroken line it should work.Ink recipes I am working with use Copper containing chemicals and causing them to form nanoparticles of predictable sizes.Plating vias should be possible in any combination for all the layers on each side of the PCB since you are basically building up an image of your PCB one layer at a time. I am still exploring options for plating vias through the substrate. Currently I am leaning towards building up a filled in via during the printing process with a final drilling process in the end to drill a hole through the metal plug that has built up on that part of the PCB.Since I have not finalized an ink yet I can not say how good adhesion will be but the inks I am working on use Nanometer size copper particles that when sintered form solid copper layers. It should be possible to control adhesion depending on how complete the curing of the layer of UV acrylic underneath is.You should picture the process as running the same paper through a printer over and over and printing a new image over the old one until your board is done. By manipulating how long and when you cure the UV acrylic non-conductive parts or sinter the copper traces you control the build up of the board. Because print heads deliver such tiny amounts of ink per drop you have extremely precise control over layer thickness and shape. Through fancy positioning of the print head it should be possible to print on non flat surfaces and on almost any substrate that can stand up to the solvents and acrylic inks. Future models could include more print heads to print a base layer to allow printing on absorbent materials such as fabrics as well.Right now I just want to develop the basic printing mechanisms and inks and after that worry about going fancy.This was typed out on my cellphone so please excuse predicted text replacement and typos.

author: Thararot
author_rank: Newbie
timestamp: April 29, 2019, 03:12:33 am
content: Each of these stories may not be the same.

author: excitedbox
author_rank: Regular Contributor
timestamp: April 29, 2019, 01:34:11 pm
content: Could it be you posted in the wrong thread?

author: excitedbox
author_rank: Regular Contributor
timestamp: July 23, 2019, 05:27:58 am
content: Sorry I haven´t updated since I started the thread. I have stocked up on components and chemicals (about 90 packages in all). I still need to get components for the xenon IPL to sinter the ink into traces and a settle on a printhead.I have a prototype ink recipe developed that should work pretty well. There are some research papers using a similar process achieving 69% bulk copper conductivity (~2.43uOhm) with one flash of ~7.9J/cm3. I am hoping to be able to improve on that by mixing the different size nano particles.I have done a few test runs making the copper nano particles and I am quite happy with the results.I need to clean some of the printheads I have here to start testing the ink next while I wait for the rest of the pieces to come in.The layout and tech is all planned out and I am working on designing the many different circuits needed for the controlsI am using a 30W UV led for curing UV inksXenon flash lamp for sintering (havent decided if I want to use round or straight)laser for x and y positioning feedbacka stepper for the x axisDC motor for the y axismini stepper for z axisBLDC for drillingESP32 as the brain but may switch to a teensy because of the 2 co-processorsI may or may not add a solder paste dispenser if I do it will have to go on a second y axisI hope now that I have (almost) everything here things will move faster.

author: Siwastaja
author_rank: Super Contributor
timestamp: July 23, 2019, 05:45:03 am
content: Work on the proof-of-concepts regarding your key technological showstoppers, namely:* Flash sintering of copper traces. You need toprovethat you can create robust traces down to about 0.2mm in width, and you need toprovethis is fast enough. Measure the surface area rate you can build copper with. It's OK if filling a 15x10cm area takes a few hours of machine time, but if it takes days, you are better off just ordering the boards.* Printing with soldermask inks. Inkjetting is fairly complex.Silver ink "PCB printer" projects have come and gone. It won't work, it isn't solderable, and the conductivity is just too low (1/10th of the copper in actual products I looked at).Working on these two doesn't require massive funding, nor product design. You need to solve these first behind the curtains. The rest will come automatically.Stepper motors? ESP32? Who cares? Do not spend time developing control electronics or UI, or funding. These are trivial.The "kickstarter" market is full of projects that have trivial details worked out, marketing, and funding, but completely lack the fundamental piece, making them dummies or scams. Don't be that way.

author: excitedbox
author_rank: Regular Contributor
timestamp: July 23, 2019, 05:56:33 am
content: Here are 2 (blurry) pictures of the copper nano particles that I am testing for oxidation. They haven´t been sintered yet so the color is quite reddish. The blue specs are copper sulfate crystals I spilled on my work surface. The picture with the spread out nano particles is actually see through and looks like a fingerprint or smudge to the naked eye on the plastic slide I put them on. Even on that picture those are whole clusters on particles. That darker spot in the bottom left corner can barely be seen with the naked eye.As another project I am building a laser microscope which will be able to get down to a much better resolution to where we might actually be able to recognize some particles.

author: excitedbox
author_rank: Regular Contributor
timestamp: July 23, 2019, 06:01:35 am
content: Speed all depends on the printhead you are using. There are projects that have much higher conductivity than the 10% you are claiming. There is a commercial product that you run through a normal laminator that gets up to 39% of bulk copper.https://copprint.com/they list 30-50% of bulk copper for their inks. The picture below from a research paper shows much more copper colored traces and achieves much better conductivity.I am looking for about the speed of the Epson WF printer in photo mode for a basic model. That takes about 6 minutes to print a 15x15 area. An industrial printhead such as the Xaar will obviously be much faster but costs 10times as much.PS. I have private funding already.

author: Siwastaja
author_rank: Super Contributor
timestamp: July 23, 2019, 09:50:49 am
content: 30-50% of copper conductivity (at same volume) would be already good enough for many purposes; especially if you have the option to compensate by printing thicker layers (i.e., 70µm instead of standard 35µm). You just need to demonstrate adhesion and solderability.

author: excitedbox
author_rank: Regular Contributor
timestamp: July 23, 2019, 01:16:50 pm
content: I know. You could already place the printed board into a copper plating bath for a few seconds and get 100% bulk copper and solderability because the board will already be conductive where the traces are.I am pretty sure that once there is a masking layer printed over the copper traces adhesion for the traces won´t be a problem, the pads I will have to see. I want to print the copper onto semi cured layers of the dielectric when they are still sticky so I hope that they will be held from the bottom.

author: SiliconWizard
author_rank: Super Contributor
timestamp: July 23, 2019, 01:21:45 pm
content: I suppose you know Voltera:https://www.voltera.io/and have taken a look at their approach.

author: Siwastaja
author_rank: Super Contributor
timestamp: July 23, 2019, 04:03:00 pm
content: Quote from: SiliconWizard on July 23, 2019, 01:21:45 pmThey specify resistivity as 12mOhm/sq at 70 um. Equivalent copper is about 0.25mOhm/sq. This is 50x worse, meaning completely useless for most purposes, at least without extra precautions during design.This is something you need to look at with silver ink devices. A huge trap, because such a number is not advertised clearly.

author: CM800
author_rank: Frequent Contributor
timestamp: July 23, 2019, 05:43:43 pm
content: What about using a DLP such as the DLP3010, to image over the PCB. (put it on an XY table for imaging larger pcbs with higher accuracy/resolution.)https://www.mouser.co.uk/ProductDetail/Texas-Instruments/DLP3010AFQK?qs=sGAEpiMZZMt5lO6VlnEbAxiv2nFtIxLjlbgdN2kUgPvpRGb2T%2FeJVQ%3D%3D

author: SiliconWizard
author_rank: Super Contributor
timestamp: July 23, 2019, 07:44:42 pm
content: Quote from: Siwastaja on July 23, 2019, 04:03:00 pmYes, this is pretty bad. But "useless for most purposes" is a bit of a stretch...Anyway, I'm not advocating Voltera whatsoever, I was just making sure the OP knew what he was "competing against" and that they had searched for "prior art" properly.It's always good to do so when starting an ambitious new project.

author: Siwastaja
author_rank: Super Contributor
timestamp: July 23, 2019, 09:17:29 pm
content: Quote from: SiliconWizard on July 23, 2019, 07:44:42 pmIt really isn't a stretch at all. 5x worse than copper would be a "maybe-ish?" corner case. 50x is totally useless.In most PCB designs, we really rely on a decades of experience of "good practice" of our own or that of others. So we are handwaving our stuff and adding a good safety margin. Do you analyzeeach and everytrace for current, heating, etc? No, no one does such perfect job unless designing a trivial sub-unit for a space station with unlimited budget.Yet we tend to mostly succeed and only encounter a few gotchas every now and then. We fail whenever our assumptions are wrong, but they are not wrongtoo often. This is because we have a lot of margin in our handwaving. This isn't by coincidence - the components areengineeredto mostly work intypical conditions, and datasheet examples, appnotes and generic wisdom communicate this idea of "typical". They are supposed to be mounted on a copper PCB with a certain conductivity. The exact value usually isn't important.But when your track resistivity suddenly goes up, not by 2x, or 3x, not even by 10x, butby 50x, all of the mental rules you follow suddenly change - you are two orders of magnitude away.Suddenly your puny simple microcontroller circuit's Vcc is fluctuating, not by meaningless 5mV, but by 250mV.You wire the trendy ESP8266 module up like everybody else to prototype your newest IoT coffeemaker breakthrough? Tough luck, it's pulling spikes of 350mA, and it's already brown-outing due to trace resistance of your 50mm long power trace, even though you used a generous 20-mil trace. dV=420mV for this magical silver ink; dV=9mV for copper.Poweranythingjust stops working. Including regulators and supply rails to anything bigger than the smallest AVR or PIC circuit blinking an LED at 10mA.Suddenly anything using more than half a watt becomes "power electronics", with associated difficulties.Only the least demanding corner cases are left. But as a customer and an engineer,genericitywould be exactly what you wanted from such a device.Sure, you can analyze the shit out of every circuit, learn and accept the new rules, and get working circuits out of it, but really, the device's supposed to exist to enable quick prototyping. Which of course isn't possible if you need to design with completely different rules and knowledge than for production circuits. Or limit yourself to a very small subset of possible circuits. And need to rule all power electronics out completely.I'm not saying OP's solution would be as crappy as this, they are clearly aware of the issue. Quite the opposite, it seems that "prior art" is so crappy that the market is totally there, without serious competition. We just shouldn't make excuses for crappy products, but concentrate on finding and fixing the showstoppers (ink resistivity clearly still being one of them. Hint: if you can do it properly, that's a great selling argument).

author: MagicSmoker
author_rank: Super Contributor
timestamp: July 23, 2019, 09:28:21 pm
content: Quote from: Siwastaja on July 23, 2019, 09:17:29 pmOn the plus side, you get excellent damping of any stray resonant networks...***I think the OP's idea is very interesting, so mainly just replying here to be subscribed to the thread. Carry on.

author: excitedbox
author_rank: Regular Contributor
timestamp: August 09, 2019, 02:10:23 pm
content: When 69% copper is already being done I don´t know why you are suddenly talking about 50X the resistivity. We are talking less than 1.5X the resistivity with current technology.Pretty much all displays these days are printed using inkjet technology. I am trying to bring the cost of the printers down from the 200k+ point to something that is affordable for hobbyists and smaller companies.Voltera is very different. They are mixing conductive things with plastic to make conductive paste like those conductive 3d printer filaments. Then they squeeze it out of a syringe. Way too slow and not conductive enough. You can light up a LED but battery life will be crap. They have been working on their ink for years and I already had better conductivity on my first test.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: August 09, 2019, 03:07:13 pm
content: Have you considered electroless copper plating? This is catalyzed by an activated surface, or autocatalyzed by a metal surface (so it continues to build up while it soaks in solution). Any conductive ink could be used, or ink need not be used at all if an appropriate activation bath can be found. (Which, I think they do this with FR4 commercially, anyway, so this should be practical?)I don't know how practical such a process is for a printer; you'd probably need a reservoir of starting reagents, a bath where they mix with the board (handling should be pretty easy, just teflon-lined grippers and stuff, if nothing else?), then a waste disposal tank where the spent materials can be stored for disposal (or processed for recovery, or for easier disposal e.g. evaporating solvent to concentrate it for reuse, ion exchange to remove/recover heavy metals (copper), evaporating to solid for dry disposal, etc.).Hm, I suppose all those things are what the industrial proto printers do already, wouldn't it be? A few extra steps (tin resist, electroplate, etch, strip..), but those could be omitted for a somewhat lower quality process. In which case you'd still have basically the same thing, and consequently it wouldn't really be cheaper, huh? So I guess your intent is to avoid chemical processes if at all possible?I wonder if PVD something or other would ever be competitive. Drawing a hard vacuum is a pretty high bar to start off with (the hardware alone would probably account for 1/3 your target cost..), but if you can manage that, repeatably and cheaply enough, it's not nearly as messy, I don't think? You'd feed in, either copper plate for sputtering, or wire (to a tungsten/molybdenum boat) for evaporation. Still need a resist and/or etch step though, hmm.I wonder if a plasma process could be employed for the etching, too? It wouldn't be practical on thick layers though, so you'd have to start very thin (~um) regardless. Which isn't very helpful compared to, say, a conductive ink, which does the same basic thing with a lot less bother!And that's to say nothing of multilayer, which none of this is any help with.So that sounds like, working on inks is the right direction, which is encouraging.Flash sintering sounds awfully cool (hot); how do you control the temp rise in the insulator/substrate and conductor? Would that be a matter of picking exposure wavelengths versus absorbance spectrum? Doping with susceptors (e.g. graphite) or reflectors (e.g. TiO2 white pigment)? Alternately, spreading out the power density through depth, by using a much more translucent insulator than the conductor?If it's not so easy to control, would it be necessary to raise the insulator melting point instead? Flash sintered ceramic or glass would be awfully cool. Harder to handle (brittle), but another interesting product nonetheless -- consider the cost of existing ceramic hybrids. Smaller market I would suppose, but still a problem in need of a solution? Would also allow better consolidation (final step in a kiln; should be a simple enough physical process, at worst needing an inert or reducing gas fill, no liquid or solid chemicals and no additional waste?).Huh, does flash sintering not have any problems with the substrate curling up like a potato chip?Anyway, just thinking out loud. This sounds really cool, and I wish you the best of luck on it!Tim

author: excitedbox
author_rank: Regular Contributor
timestamp: August 09, 2019, 09:56:43 pm
content: Electroless plating is how PCBs are made right now. I don´t plan on using PVD so no vacuum or anything like that. The flash pulses are so short that the materials don´t heat up much. It is more about activation energy than actual heat. Between 7-12 J/cm^2 is about right in a 5ms pulse.Making copper nanoparticles is extremely easy using almost any copper containing chemicals. I have chosen copper sulfate. Using surfactants such as the ones used in soap making, and glycerin or polypropylene glycol which is used in vape fluid and ascorbic acid you can make inks containing copper nanoparticles.Copper is very reactive though so it oxidizes quickly but during the manufacturing process the copper particles are capped with the reducing agent which slows that process. After printing the ink onto the substrate you can use photonic sintering to quickly cause a reducing reaction to get rid of the oxygen atoms, break down the capping agent, and melt the now pure copper particles together into copper traces.The above is a simplified description of how it works but that is the basic process with a few spices thrown in. I have capped copper nanoparticles that after being exposed to air for the last month still have not oxidized. I am now experimenting with different sizes of particles and setting up a better test environment to control and test the parameters and do size classification of the particles.I also want to experiment with the flash wavelengths and pulse lenght/power to get good penetration so that when you print multiple layers they are sintered all the way through and not only on the surface or else you build up a layer cake with unsintered ink.

author: Siwastaja
author_rank: Super Contributor
timestamp: August 10, 2019, 08:45:12 am
content: Quote from: excitedbox on August 09, 2019, 02:10:23 pmI included full quote trail to prevent confusion, but yes, it wasn't related to your product, but your competitor's. Please read carefully before replying. Thank you.QuoteThat's an amazing achievement, and you are doing much better than most of your competitors, if you can deliver it. Keep going.

author: excitedbox
author_rank: Regular Contributor
timestamp: August 10, 2019, 05:16:45 pm
content: I was trying to steer the thread back on topic, I did read your posts fully. I just find it useless talking about steam engines in an internal combustion engine discussion.So far I don´t have results of 1.5X but others who´s research mine is based on have gotten around 1.3X and I am getting closer with each test. I need to build a stronger flash unit with more control to fine tune things.

author: AlanS
author_rank: Unknown
timestamp: September 11, 2019, 11:57:40 pm
content: I'll be watching this project with great interest.