PCB etching   -where do i start?  - Page 1
Forum section: electronics / beginners

author: parkeraph
author_rank: Newbie
timestamp: August 06, 2014, 02:12:46 pm
content: Hello,I have finally finished a design and i would like to reduce the size of it. I was told to make my own pcb for it.I have been researching how and have found myself in a mess. What solutions do I need? how do i design it?Any advice and answers are greatly appreciated.-parker

author: Kjelt
author_rank: Super Contributor
timestamp: August 06, 2014, 02:24:22 pm
content: A bit cryptic post there.You have a design, is it a breadboard? And now you would like to make a pcb for it?First start learning a pcb cad program like Eagle pcb or any other to create first the schematic of the design with the correct components and if you want to go smaller try to change to SMD components. From the schematic Eagle or other cad program will let you create the pcb by placing the components and routing the "wire" traces between the components according to the schematic. If that is finished you can use the output (board file or gerber file) to let a company make a pcb or couple of pcb's for you. Some companies can do it (depending on pcb size) for $20 to $30.I would not recommend etching yourself if you have no experience.

author: con-f-use
author_rank: Unknown
timestamp: August 06, 2014, 08:00:43 pm
content: Quote from: Kjelt on August 06, 2014, 02:24:22 pmEtching is a messy potentially dangerous process that needs some practice. Most people don't bother and have it manufactured.I personally etch boards if a) I can't wait b) I just want to make prototypes or c) I'm not feeling like spending money. It is not hard and there's a ton of tutorials. Just go slow and use your brain until you get practise.My process is something like this:1.) Create the schematic2.) Lay out the board in eagle3.) Wash my hands, put on gloves, glasses and my working cloth4.) Print the layout on paper with my laser printer (so I can check it and glue an appropriately sized patch of press'n'peel to it)5.) Print the layout on press'n'peel6.) Prime the board by pre-etching in the solution for a minute or two cleaning it afterwards (I find the toner sticks better this way)7.) Transfer the layout using a laminator8.) Throw the board with the layout into HCl peroxide mixture and wait till its etched (10 min for a well prepared solution)9.) Clean the board first with plenty of water and than with acetone to get the toner off10.) Drill and populateStep 1 and 2 can take from 15 min. to months. At first steps 3 to 10, the actual etching, took me about two hours. Now I've streamlined the process and set up the equipment. I need 30 min now if all goes well. Still etching is messy and involves chemicals, a spot with running water that can get dirty and some gear (gloves, safety glasses, plastic canisters, plastic pliers and/or tweezers, clothing that can get dirty and is acid resistant).

author: corrado33
author_rank: Frequent Contributor
timestamp: August 06, 2014, 08:25:24 pm
content: Quote from: con-f-use on August 06, 2014, 08:00:43 pmEtching isn't dangerous unless you drink the chemicals used. (And if you do that, then you deserve everything that happens to you.) Etching at home is easy, but I'd recommend getting actual products to help you instead of trying to "get by" by doing things the "cheap" way.Buy yourself some toner transfer paper and some Ferric Chloride. Alternatively you can use pretty much any relatively concentrated acid you have available to you, but FeCl3 works very well. After that simply print your design out onto the transfer paper, iron it on to the copper, then etch away. You'll mess up the first few, but you'll figure it out.Just as a note. Most of the components in Eagle libraries have pads much too small to be comfortably soldered by hand, especially for someone new to soldering.

author: Falcon69
author_rank: Super Contributor
timestamp: August 06, 2014, 08:41:42 pm
content: If you have time, it will be cheaper i think for you to just order a PCB made. There are plenty of sites you can download your gerber files to, and they will make the boards based on those specifications. I myself use Sitopway off eBay, about $40 to have it made. I've been pretty happy with them so far. They usually ship to my door within 5 days. I think it will cost you alot more then that to buy all the chemicals and stuff to do it yourself. Although, it may be a good learning experience for you, and anyone else new to it.If you don't know how to operate the software to do it, I can do it for you if it's not a hard or complicated circuit. I don't mind, gives me something to do. I can upload the file to you in 3D as well, so you can see it, if it all looks good, I can send the gerber files to you, and you can send them off to whoever you have them made from.Jason

author: kamilon
author_rank: Newbie
timestamp: August 06, 2014, 08:44:18 pm
content: If you really want to do it at home I made a blog post a while ago on homemade PCB creation:http://blog.kamilon.com/?p=69However, getting started isn't super cheap. It'll probably be cheaper to have them ordered. I mostly order my boards now unless, like a previous poster said, I want the boards like NOW.I also don't like doing anything at home that isn't a single sided PCB. It just isn't worth the trouble.

author: Fred27
author_rank: Unknown
timestamp: August 06, 2014, 09:02:53 pm
content: You should only etch your own PCBs if you enjoy the process and challenge of creating it yourself. You won't really save money or time, but it's fun. Well, I think it is anyway.

author: Kjelt
author_rank: Super Contributor
timestamp: August 06, 2014, 09:14:15 pm
content: Not to mention that home etching has limits to the minimum size of your layout.SMD will be tricky with under or over etching which can occur frequently. And also double sided exposure with exact alignment has its challenges.

author: rob77
author_rank: Super Contributor
timestamp: August 06, 2014, 09:30:56 pm
content: if you'll decide to go for etching at home, the be VERY careful with the hydrochloric acid and peroxide - those are nasty chemicals. never use HCl + peroxide inside - the fumes are aggressive - every single piece of metal will start corrode from the fumes - so do it outside.other possible chemicals are Ferric chloride FeCl3 or Sodium per-sulfate Na2S2O8neither of the chemicals is nice to you and the environment, so you'll have to take care of the disposal afterwards.

author: K1JOS
author_rank: Regular Contributor
timestamp: August 07, 2014, 02:41:02 am
content: QuoteCan you offer some beginner advice for Eagle? What would be a good starting default pad diameter and default trace sizes for home fabrication of small PCB's

author: miguelvp
author_rank: Super Contributor
timestamp: August 07, 2014, 03:35:37 am
content: Lecture 8 (linked) and lecture 9 will get you going:https://www.sparkfun.com/tutorials/108Edit: Lecture 10 bonus create your own part in Eagle.

author: tautech
author_rank: Super Contributor
timestamp: August 07, 2014, 04:43:08 am
content: Quote from: K1JOS on August 07, 2014, 02:41:02 amI try to keep most simple TH pads 100 mil (0.1") minimum.Many power devices need larger of course.For 2 reasons: ease of hand soldering and pad robustness for any rework.I may have to make pads oval or rectangular to maintain clearances and robustness.For DIY etching, (especially while learning/perfecting the etch) keep tracks a minimum of 20 mil (0.5 mm), this allows some tolerance when things go wrong(under cutting, semi porous toner transfer).Polygon pour and track to track clearance: 20 mil minimum again, but I prefer 40 mill (1 mm) less chance of solder bridges and better electrical clearance for higher voltages <~100 VHole size: I use only one. 20 mil. Why? it is a good centering size for drilling. But I use a 30 mil (0.8 mm) drill and enlarge more when needed.Without the benefit of top and bottom overlays, you can add a few mods to footprints to help with population.These I normally always do:Square pad for: IC pin 1, header pin 1, Cathode, +ve pad Ecap or VDD to or from PCB.Copper text: K for Cathode, + for polarized components, Net labels, IC #'s (4013 etc)I use a PCB solder through spray on lacquer after etching to prevent PCB oxidation.

author: kolbep
author_rank: Frequent Contributor
timestamp: August 07, 2014, 05:41:48 am
content: Quote from: rob77 on August 06, 2014, 09:30:56 pmTalking about that,once I was building a few chasers for christmas lights to go in Margate, and Ramsgate South Africa,whilst the owner of the company, and his brother was making up metal frames of christmas trees, etc, to hang the rope lights on.Pack up and go home.Come there the next morning, and the metal frames looked eaten away. The owner then asks me what the stuff in the 'Easy Etchant' bottle is used for. I had to try not laugh, as I explained to him that it is designed to etch away metal.What had happened the night before, is that they had a few patches of rust on the metal, so they took whatever chemical they could find, and brushed it all over the frames...

author: con-f-use
author_rank: Unknown
timestamp: August 07, 2014, 08:05:03 am
content: The four etchants I have used of are: H202 + HCl, Fe3Cl, H2O2 + Kitchen Vinegar, Sodium persulfate. Fe3Cl works very well when heated a little bit but makes very nasty stains, vinegar plus peroxide is cheap and readily available but doedn't etch all that fast, sodium persulfate is incredibly slow and relatively expensive, also not that easy to source. I prefer muriatic acid plus peroxide as the best of the four.Here is athat covers some other etchants.Quote from: corrado33 on August 06, 2014, 08:25:24 pmYou can damage your eyes with almost every etchant, the fumes are irritating to you your respiratory system and with HCl or H2O2 you can get chemical burns. Of course you need to be very clumsy or stupid, but its still something to watch out for.Quote from: rob77 on August 06, 2014, 09:30:56 pmOnly while the HCl + H2O2 solution is fresh. After a board or two the etching process will be a bit different and cupric chloride will be the main etchant (so don't trow away your "spent" etchant). See e.g. thisinstructableor themore "scientific" explanation(if you are into that sort of masochism).

author: sleemanj
author_rank: Super Contributor
timestamp: August 07, 2014, 08:21:00 am
content: Quote from: K1JOS on August 07, 2014, 02:41:02 amTrace size: 20 mil is easy as pie, 13 mil is starting to get interesting, 10 mil is "only where necessary" and 8 mil is "oh man, is there really no other way to do this at all" area. All are do-able at home (with some practice).Trace separation: similar to the size, but for home purposes I find that going less than 12mil separation is just asking for trouble (hairline shorts between traces). I typically say that thin traces are easy, close traces are hard.Hole size: for through holes for most parts I use at least 60 mil (1.524mm) pads with 0.8mm or 0.9mm holes, I will typically make them oval where possible with about 75 mil on the long dimension to give a bit extra footprint, they look a bit funny perhaps but I just find ovals nicer to hand solder. I shrink the hole size a bit when DIY etching, using mygerber to etchable PDF script, which has the facility to shrink the holes in the gerber, this is so the etched centers of the holes are large enough to help center the bit, bit small enough that there is some extra room for error when dealing with double sided boards.Not to be overlooked is pad size for SMD components, if you are hand soldering, make them a bit longer so you can get your iron onto them - just adding 0.1-0.2mm to the length of the pad can make quite a difference

author: sleemanj
author_rank: Super Contributor
timestamp: August 07, 2014, 08:31:35 am
content: As for the fuming of HCl+H202 etchant. People have a tendency to run the etchant too strong which would make it fume like crazy.Dilute the HCl so it's not fuming, use less H202 so it's a manageable rate (of course if your H202 is weak to begin with, it can do the diluting for you).As above, don't discard the etchant, just keep using it, add a little H202 every etch, and a little HCl every now and then - no need to be scientific, just go-by-eye, too dark green, add H202, too slow for you, add HCl.Obviously still do it outside, and wear appropriate safety stuff (glasses are a good idea, just in case of splashes, and of course gloves, you don't want it on your skin).

author: Fred27
author_rank: Unknown
timestamp: August 07, 2014, 09:39:41 am
content: Quote from: Kjelt on August 06, 2014, 09:14:15 pmSMD is easy enough with home etching. In fact as it minimises drilling, a lot of people (like me) prefer it. I do 0805, 0603, SOIC and TSSOP happily. Not done LQFP yet but I'm not expecting a problem.Alignment is easy enough if you make an "envelope" of pre-aligned transparencies taped on 3 sides and slide the board in. Leave the corners untaped.Other personal preferences. Others may disagree:Presensitised UV boards are better than toner transfer. If you're making a through-hole shield for an Arduino then toner transfer might be for you. However, I prefer quality over saving a few pennies.People complain about FeCL3 but HCl/H2O2 is so much nastier. I don't want my lathe, laser cutter and CNC mill to rust from the fumes!Bungard Dynamask 5000 solder mask is excellentTinning is worth itZiploc vacuum bags are good for holding transparencies against the PCB for exposureI've not finished a good PCB write-up but some info here:http://0xfred.wordpress.com/2014/02/28/further-pcb-improvements/

author: con-f-use
author_rank: Unknown
timestamp: August 07, 2014, 12:22:46 pm
content: Quote from: Fred27 on August 07, 2014, 09:39:41 amI don't like the extra step and chemical (developer). I'd wager for 0603 and TSSOP my boards are just as good. But results vary with printer, toner, transfer paper and even the brand of copper clad used. It did take some experimentation to get it down right. UV certainly has less variance there but now I'm convinced of toner transfer. If I had a laser cutter though, I'd spray my boards with black paint, laser print my layout on there and edge that. Even more direct and precise.Quote from: Fred27 on August 07, 2014, 09:39:41 amI want a laser cutter and a lathe!But HCl+H2O2 is only bad for the first two boards or two days. Once the original etchant is spent and you actually etch with cupric chloride it doesn't corrode anything. Also there's lids for your etchant containers. Fe3Cl is much more nasty.Quote from: Fred27 on August 07, 2014, 09:39:41 amAgreed. Longer boardlife, more robust traces in general, easier smd soldering and shinier. Soldermak is overrated though. If I'm worried about accidental shorts, I spray it with some "Plastik 70" once all is soldered, tested and cleaned up. I'm lazy that way.

author: sleemanj
author_rank: Super Contributor
timestamp: August 07, 2014, 01:24:06 pm
content: Quote from: con-f-use on August 07, 2014, 12:22:46 pmDry film photoresists develop in a very weak Sodium Carbonate (or Percabonate and various other combinations) solution - 30g/L at the most, your granny probably hand washed the clothes in much stronger concentrations for much of her life, that's why it's called washing soda. Takes just a couple minutes, less if it's warm. They will happily strip in it to if you leave it for 1/2 an hour, but acetone is quicker.Pre-sensitised boards though do use a much less benign developer with sodium silicates and sodium hydroxide though, you wouldn't want to be putting your fingers in that.