How do you repair the PCB before etching it ? - Page 1
Forum section: electronics / general

author: Hextejas
author_rank: Frequent Contributor
timestamp: August 28, 2018, 07:57:37 pm
content: After I have pressed the printed copy of my circuit onto the copper plate, there were some obvious errors. Traces not connected, pads incomplete, etc.I was thinking that if I had a marking pencil/pen of the same composition as what the laser printer had imprinted, I would have been able to repair the board before the etching bath. I tried a permanent marker but it failed as I expected.If anybody invents something that could do this, they will make a fortune.

author: ogden
author_rank: Super Contributor
timestamp: August 28, 2018, 08:32:21 pm
content: Just simply don't use toner transfer. Use dry film photoresist or presensitized PCB's instead - you will get much higher quality and repeatability. Then you don't need to fix errors by hand, you just fix your errors in PCB design software and re-print transparency.Oh, and this advise is for free BTW

author: KL27x
author_rank: Super Contributor
timestamp: August 28, 2018, 09:48:40 pm
content: I have found there are several factors which affect permanent marker, and I have tried a few of the highly recommended pens - those being Sharpie, Industrial Sharpie, and Lumocolor.FWIW, the regular Sharpie brand works just fine for me using cupric chloride, so long as the copper is shiny clean where I apply it. If you use a different etchant, then your results will vary. IME, HCl and peroxide is not easy on pen, and none of these worked particularly well for me with HCl. But you may find something that works better.With HCl, the Lumocolor held up slightly better, IIRC, but still not great. And it's harder to get on the board, neatly.Ogden has a point, but I have been doing toner transfer for a good while, and it is very possible to do it with no errors down to at least 8 mil traces. Not just sometimes, but all of the time. You just need a few tools and techniques as well as quality dextrin coated transfer paper.

author: alsetalokin4017
author_rank: Super Contributor
timestamp: August 28, 2018, 09:55:10 pm
content: I've completely hand-drawn several circuits using the regular Sharpie marker. As far as I can tell it's not much different from the "Industrial" Sharpie that is specifically sold for the purpose. Except it's a lot cheaper. I'm using ferric chloride etchant.I've also laid out complete (simple) circuits using clear packing tape and Xacto knife. The clear packing tape is a great resist. You can use the knife to make little strips and shapes of the clear tape and stick those onto your PCB where you need a trace. It works great with ferric chloride, good sharp edges, but I don't know about other etchants.

author: vk6zgo
author_rank: Super Contributor
timestamp: August 28, 2018, 11:19:39 pm
content: You used to be able to buy a "Dalo" pen which was specially designed for drawing tracks.Instead of ordinary ink, it drew in "resist".

author: Mark
author_rank: Frequent Contributor
timestamp: August 29, 2018, 08:48:54 am
content: I used to use DECAdry ER06 (0.04") and ER07 tape for the tracks and their pad transfer sheets for the component pads. It worked well either directly on a PCB for one-offs or onto a clear acetate sheet for the photoresist method.Not sure if you can get either of those products now though. Maybe a craft shop would have something similar to the decadry tape.

author: Hextejas
author_rank: Frequent Contributor
timestamp: August 29, 2018, 02:21:45 pm
content: Quote from: alsetalokin4017 on August 28, 2018, 09:55:10 pmAlse, is there any particular reason that you used clear packing tape ? The reason I ask is that I have a lot of brown packing tape.

author: ogden
author_rank: Super Contributor
timestamp: August 29, 2018, 05:10:56 pm
content: Quote from: KL27x on August 28, 2018, 09:48:40 pmNah. What's dextrin? Besides film all you need is your clothes iron (or laminator), <=15$ "UV nail lamp", "silkscreen inkjet transparency" in case of inkjet printer (my favorite). For laserjets more or less any laserjet transparency works - as far as printer itself can put proper layer of toner on it. Inkjet with pigment black ink recommended, thoumostmany modern inkjets uses pigment instead of dye in the black cartridge. Indeed you shall doublecheck before shopping. Developer (Sodium Carbonate) you can get in any supermarket - as washing soda. Use any etchant you already have. Stripper after etching: acetone. Basically that's it, in short.More info regarding dry films here (pdf file).Yes, I am huge proponent of dry film. While ago we had competition with my colleague who *was* die hard fan of toner transfer. He lose pathetically in virtually every category of competition.

author: KL27x
author_rank: Super Contributor
timestamp: August 29, 2018, 09:06:57 pm
content: QuoteGenuinely curious what is this competition? And did it take into consideration time and effort?The problem with toner transfer is many people do it only halfway correctly. And it still works well enough for many people. AFAIK, it's possible to get 4 mils traces with positive resist and good etchant. That's what the commercial companies can do. But you need a high resolution printer and tracing papers. And with negative resist and home printers are you not practically limited to around 6-7 mils, and is that not pushing it? Is this not so? *More importantly, what kind of resolution do you get, personally, not just a line on a test but doing an entire 50+ square inch panel with no errors? I'm curious?For toner transfer, the few tools are the laminator, a heat gun, and the dextrin paper. Putting the transfer on the board take a bit more time and effort perhaps than putting on a dry fim. But you don't need to expose, or do the one (two?) baths, after.*From the PDF you linkedQuoteI'm sure you can do better than that with UV and negative resist. This is nothing to write home about. So what's your result? If this is what is practical, I think toner transfer is faster and has better resolution. Honestly with no fuss I can do 8/8 with toner transfer, with no worries. Large panel after panel without error. If I need X boards, I will make exactly X boards, knowing they will all be fine. (Before learning all the nuances, I would need to use 10 traces AND scale it up to make extra copies just in case. But the nuances are not difficult to execute. It's just a matter of knowing to do them. There is no trial and error or surprises.)Most people doing high density stuff at home use UV, because 10 years ago it was better. (Before you could by Pulsar paper from Digikey or Mouser). They will continue using photo resist, because that is what they know, and that is what they have invested their personal knowledge in. And they've built a UV box, and maybe they have only an inkjet printer. But only the biggest cheapskate will find much improvement in using dry film. The dry film can be a bit cheaper than Pulsar paper, if you are doing a high volume of boards. For most people this minute cost is not worth the extra effort.Most people who start out with toner transfer, it's because of the initial investment. They don't want to buy anything. And they use one of the many terrible guides on the web. There are many terrible guides, because it IS so cheap to do. And that seems to be the main point of the guide; look at me, I made a crappy board for free! If you think you need UV to get better results, you are not listening to the right advice. And you're being too cheap. Put the photo and mag paper away, for a start.

author: CatalinaWOW
author_rank: Super Contributor
timestamp: August 29, 2018, 09:58:20 pm
content: For making repairs in toner transfer boards I have used three materials successfully. Sharpie, pwb pen and fingernail polish. Sharpie requires a fresh pen and careful observation under a microscope to assure that the copper is thoroughly covered. Fingernail polish is absolutely reliable but requires fine brushes and care for fine lines, and cleanup of brushes is required.Photoresist methods work great - for some people. I have had trouble with them. I know they can work, the problem is mine, but for me it is real.When advocating a method recognize that others may have different weak spots or limitations. Not everyone has to do it my way or your way. They just have to do it well enough to meet their needs. I have never needed a large panel. If I did I would probably go commercial.

author: ogden
author_rank: Super Contributor
timestamp: August 29, 2018, 10:09:29 pm
content: Quote from: KL27x on August 29, 2018, 09:06:57 pmWe compared our results next day. I do not even know how much time and how many tries he spent trashing PCB's until one that (seemingly for him) is ok, came out. Problem with toner transfer is that usually you see problems AFTER etching AND you have to be quite skillful, own right kind of laser printer that prints right density of the toner on your transfer paper. Toner transfer preachers usually "forget" to mention this very important precondition of right printer/tonerDoes it really matter that film needs 2 minute exposure and 5 minute development + wash compared to toner transfer? It's freaking extra just 10 minutes per board maximum compared to complete disappointment after disappointment and ruined day in the end.QuoteWell... you can correctly plot your PCB using just marker and ruler. My point is exactly in what you just said: when many people try dry film and toner transfer, then those with film happen to be more successful.QuoteWe just put two sample boards under microscope. Mine won.QuotePardon me? Inkjet printers usually have better resolution compared to laser printers.

author: KL27x
author_rank: Super Contributor
timestamp: August 29, 2018, 10:21:18 pm
content: QuoteIt's a set of chemicals you have to prepare and put in a tray big enough for a board. Then dump after? Or do you save it? I dunno. But there's a reason Hot Pockets sell when "all you have to do is actually cook things." This is time and space and effort. And you have to do it in the dark or red light? Or just a dim room? I dunno how sensitive that is TBH.For toner transfer, I initially clean the board in the kitchen sink. And print up the transfers. The rest of the operation happens outside right by the etch tank. The only thing I have to prepare is to fill a bucket with water.QuoteYou have this part all wrong. You are not believing what I have said in my last post.QuoteIt's less density than you need for UV, actually. Pinholes in the transfer can transmit in UV, and for high density one trick to compensate is to double up transparencies (or tracing paper). Toner melts and merges the matrix that was initially printed. This is more time and effort for UV. I use the cheapest laser printer on the market. And the printer is probably why I'm limited to 8 mil. Although to be honest, I have never tried 7 mil. (At 6, there starts to be actual large breaks in the trace in the print, one every say few inches).QuoteThis is also a deficiency of application/methodology. I promise this is not necessarily the case, even if people are stuck to certain inefficient ways of doing toner transfer. Again you do not believe what I have just posted. There is no skill needed. No measuring, mixing, timing, no careful tweaking. No guesswork or judgment calls, at all. Nothing but 100% success following simple rules.QuoteDo you know what is the minimum trace width/separation you adhere to when you make PCB? That would be nice to know.

author: ogden
author_rank: Super Contributor
timestamp: August 29, 2018, 10:38:48 pm
content: Quote from: KL27x on August 29, 2018, 10:21:18 pmI could not find such brand and model "cheapest laser printer". Please be specific? I wonder about it's DPI because you stated that toner transfer gives better resolution than dry film.QuoteWhat about laser printer? - in case they do not own it. I think much more expensive purchase than roll of dry film and pack of inkjet transpareciesQuoteI do believe you - thatyougot it right. The same 100% success can be achieved using dry film. So what?

author: KL27x
author_rank: Super Contributor
timestamp: August 29, 2018, 10:42:28 pm
content: QuoteSo what is it takes more effort and space to do dry film. What is the advantage? And if you are "out of practice," you maybe mix the developer wrong or do too much, too little time. There is nothing to screw up in toner transfer.HP LaserJet 1102. And laser is way cheaper per page. Maybe 10 or 20 years ago, laser is not as affordable for home use. Today, it is cheaper, unless you print only color photos and such.QuotePersonally, I have not owned an inkjet printer since maybe the year 2000.

author: ogden
author_rank: Super Contributor
timestamp: August 29, 2018, 10:55:26 pm
content: Quote from: KL27x on August 29, 2018, 10:42:28 pmWay cheaper per page than what?Let's see Amazon prices:HP 85A (CE285A) Black Toner Cartridge, 1600 pages, 75.89$Epson T664120 EcoTank Black Ink Bottle 70ml, 4000 pages, 12.95$What kind of math you are using to say that laserjet page ischeeper- dunno.

author: KL27x
author_rank: Super Contributor
timestamp: August 29, 2018, 10:58:19 pm
content: You are comparing a bottle of ink to an OEM cartridge.You can buy generic toner refills, too. And there's no ink cartridge to clog up or excess inkpad in there that fills up and must be serviced.Times are changing, perhaps. I remember when they sold inkjets for $60.00 and the expensive cartridges has protection circuitry in them. Still do in many cases. At least when I switched to laser, it was way cheaper, and it still is dirt cheap. Perhaps either way it is, depending on what printer you buy.If you want to go the dirt cheap, not pay anything route, the printer you happen to already own will be a large factor, true enough. In either way, the cost of the ink/toner is pretty much a non-factor compared to the time and effort.

author: ogden
author_rank: Super Contributor
timestamp: August 29, 2018, 11:03:56 pm
content: Quote from: KL27x on August 29, 2018, 10:58:19 pmYou can't believe that you can buy genuine EPSON ink bottle on Amazon for 12.95$? Well... use google or yahoo or Amazon search, or check Epson site maybe?

author: ogden
author_rank: Super Contributor
timestamp: August 29, 2018, 11:10:06 pm
content: In case you woke from 10..20 years sleep: today you can get inkjet printer that does not requires cartridgeshttps://epson.com/ecotank-super-tank-printers

author: KL27x
author_rank: Super Contributor
timestamp: August 29, 2018, 11:44:10 pm
content: You got me. I might be old man Winkle when it comes to these new-fangled refillable inkjet printers. Maybe I'll join the color printing revolution in another decade or so. But right now, I feel another nap coming on.

author: ogden
author_rank: Super Contributor
timestamp: August 30, 2018, 12:12:25 am
content: Quote from: KL27x on August 29, 2018, 11:44:10 pmLearned a lot from your confidence in toner transfer as well. I tend to agree that in case someone owns laser printer, he shall try toner transfer first and in case of success - stick with it.