What is the latest in PCB etching when you can't wait 2 weeks? - Page 1
Forum section: electronics / beginners

author: Merlysys
author_rank: Regular Contributor
timestamp: September 14, 2015, 01:15:27 am
content: I haven't done any PCB etching in over a decade. So I looked into restarting home etching, the local (Sayal) store carry all kinds of stuff from MG chemicals. But since there are numerous types of ingredients I couldn't figure out how to go about it.Are Is there kits I can order to do the entire process? Of course there must be, so what experience do you have with them kits and what is recommended and what should be stayed away from?

author: KL27x
author_rank: Super Contributor
timestamp: September 14, 2015, 02:05:07 am
content: IMO, the latest and greatest in DIY PCBs is dextrin coated paper for toner transfer. It's carried by electronics suppliers like Mouser, now, under the brand name Pulsar. It'll cost in the neighborhood of $1.00-1.50 a sheet, but this is quite a bargain, AFAIC.

author: tautech
author_rank: Super Contributor
timestamp: September 14, 2015, 02:38:33 am
content: Few recent threads:https://www.eevblog.com/forum/beginners/smallest-pitch-for-home-made-pcb-that-is-doable-for-experienced-guys/https://www.eevblog.com/forum/beginners/what-paper-should-i-use-for-making-pcbs-using-the-toner-transfer-method/https://www.eevblog.com/forum/projects/pcb-at-home-guide/

author: KL27x
author_rank: Super Contributor
timestamp: September 14, 2015, 03:20:17 am
content: It's obvious to me from reading those threads that a lot of guys doing toner transfer are just playing around with it and are happy to get results from stuff they have laying around. I haven't been doing it that long, but I have done a lot of boards SSOP pitch and 10 mil traces, standard, and a lot of the stuff I am reading in those threads is pure garbage, from a cost-efficiency standpoint.I don't know of a kit. For toner transfer:1. Laser printer that is not Brother (or if you already have one, buy some replacement toner and dump out your current cartride).2. transfer paper : take your pic. For the cost, Pulsar paper saves time and time is money. I have never had to redo a board using Pulsar. I have half a 100 pack of PnP blue and various expensive glossy photo papers in a junk box, somewhere. I would say PnP blue works better than magazine paper, and non of the photo papers I used were worth a darn. Pulsar is head and shoulders above the rest. (I never tried laser printer label backing paper).3. transfer tool: I use a laminator and a heat gun. If you open the plastic case, you can tweak the roller clamps on the side so you can fit a full 0.062" board. Otherwise, the board might get stuck and you will have to help it along. Leave the cover off, because if you shoot the board with a 1200 W heat gun while it's going through, you can transfer in 2 passes. 1 with a preheat. Otherwise, it may take multiple passes.4. etchant: take your pic. Ferric, muriatic + peroxide, or cupric chloride are all popular. Note, if you use ferric, you can reuse it indefinitely with a bubbler tank. It will slowly create cupric chloride as the end product. Just add a little water and acid every now and then. If you use muriatic + peroxide, despite common folklore that says it will turn into cupric, it won't. You use it, then you toss it, because the peroxide spontaneously decomposes after the solution is contaminated with copper ions. If you want pure cupric chloride, you have to start with muriatic plus peroxide, fit it with a bubbler, and toss in the copper from a few scrapped power cords per liter, or so, and let it dissolve immediately.A couple of my tips:Pre-etch the board in the etchant. Some tutorials suggest scrubbing the board. Yes. Scrub with wet steel wool with a drop of dish soap, and rinse. Then pre-etch it. That gives the best surface for making the toner stick, and to reduce any chance of smears, fat traces, and flaking resist that will happen with a smooth, shiny surface. Pre-etch is just dipping the board into the etchant for 5 seconds, swishing in clean water, and then drying with the heat gun.A lot of people use acetone to remove the resist, after etching. I highly recommend you just scrub it off with steel wool under running water. Because it's faster, it's easier, it helps to clean the board of etchant salts, and it preps the board for soldering and/or a final finish (I coat with liquid rosin). And also because using acetone will cause permanent carbon black stains on your FR-4 board. Acetone dissolves plastic, and that's a cool parlor trick. But it's not practical or efficient, and it adds another tool/reagent to what's already a long list. I always have a quart of acetone on hand, but this is not the application for it.I started with the habit of making 4 when I needed only 1. Since nailing all the finer points, I still usually make multiples more than what I need. It just makes sense, in case you need more in the future. Firing up the DIY PCB machine is a mental process. But if I happen to have just the right size copper clad and/or Pulsar paper for a single board, I will use it and have 100% confidence that the single board will come out without error. No sharpies, no scraping bridges, no taking the board in for inspection and repair prior to etching. The only inspection I do is to look at the dextrin paper when it comes off (instantly), to make sure all the toner came off (which is practically a given). I don't give the board more than a cursory glance before etching.