DIY PCB with photoresist method. - Page 1
Forum section: electronics / general

author: piyushpandey
author_rank: Newbie
timestamp: April 11, 2016, 09:02:22 am
content: Hi guysI found lot of topics discussing the photoresist method of the PCB designing and therefore I find it good to post mine here.Actually before posting my problem I want to tell you guys that what I have till now in order to make my own PCB with photoresist method.So here are the steps which I followed:1 -- I bought the Liquid photoresist DH-203 (Blue Color) the datasheet of which I have attached in the attachment section.2 -- I took one teaspoon of the photoresist and diluted it with acetone a little bit to make the emulsion, and so that it can be easily spread over thecopper clad PCB laminate.3 -- Now I put few drops of the liquid photoresist on the PCB and used a spatula to spread it as even as possible on the copper laminate.4 -- after that I let it dry in the dark and little warmer place and covered it with paper.5 -- After few hours it gets dried and ready for experiment.6 -- I put the image on the surface of it and get ready for the UV exposure.7 -- Here in the exposure phase I tried two things :a) -- First I bought one CFL of 15 Watt from one of Local Electronic Store and exposed the PCB with it for almost 30 min.b) -- Second I also exposed the laminate in the sunlight as I find on some site that in noon the Sun is good source of UV light.8 -- After exposure the PCB gets ready for the chemical treatment like developing and etching.9 -- I got two chemicals NaOH and Na2CO3 for the developing and stripping of the photoresist of the PCB board.10 -- I took 40 gram and 106 gram of NaOH and Na2CO3 respectively and dissolved it in the 1 liter of water (see guys I am not sure that thesesolutions are purely of 1 Molar since I am not sure of the purity of NaOH and Na2CO3, since I bought it from local store). But these arepretty strong which I am saying from my experiment as far as NaOH is concerned it stripped out the photoresist as soon as the laminate wasdipped in to it, and also the Na2CO3 dissolved all the photoresist into it giving the indication that it is quite strong.11 -- Thereafter I made Sodium Carbonate solution more dilute and tried with the fresh laminate.12 -- I repeated this experiment many times with each fresh laminate with Photoresist on it and exposed to CFL light and sunlight.But all these experiments failed to give me desired result.I am stuck at the developing stage.I don;t know where I am doing mistake and why I am not able to develop the image.Please guys help me out of this.thanks and regards

author: Fred27
author_rank: Unknown
timestamp: April 11, 2016, 10:39:51 am
content: I'd recommend starting with a presensitized board to eliminate one potential problem, even if you intend to go back to applying your own resist later.I've found that metasilicate based developers are much easier to use than NaOH. Less risk of overdeveloping.Definitely do an exposure test to see how long you need to expose for. Take a board and expose strips of it for different lengths of time to tune how long it needs.

author: wraper
author_rank: Unknown
timestamp: April 11, 2016, 10:54:03 am
content: NaOH as developer sucks. It will strip away even sightly overdeveloped photoresist, therefore very good photomask (very low transparency of black areas) is needed and a tight exposure control as well. I's not like you can expose for some random time and expect a reasonable result. For NaOH solution temperature is very important, 5-10oC temp difference can ruin your day.Metasilicate is much more forgiving.Na2CO3 is for negative photoresist, useless in your case. BTW, I recommend using negative dry film instead, liquid photoresist is a pain in the ass.

author: piyushpandey
author_rank: Newbie
timestamp: April 11, 2016, 02:46:38 pm
content: Hey guysI am not using NaOH as developer right now , instead I am using the Sodium Carbonate as developer and I want to ask wraper that why I can't use sodium carbonate as developer.Please tell me some other easily available developer for this photoresist.Has anybody tried this DH-203 before.thanks

author: wraper
author_rank: Unknown
timestamp: April 11, 2016, 10:33:54 pm
content: Quote from: piyushpandey on April 11, 2016, 02:46:38 pmChemistry?For example, why you cannot use citric acid as developer? It's also white and powdery.BTW, I say this considering that your photoresist is positive type what liquid photoresists usually are. That so called "datasheet" does not mention even this.For negative types, solution should have about 1% of Na2CO3. And then NaOH solution is used for stripping the photoresist after etching the board.JUST LOL. Now I reread that datasheet, it's not a photoresist. It's a paint for screen printing.