Photo resist DRY Film No light gone exists in board - Page 1
Forum section: electronics / general

author: ehsansis0
author_rank: Newbie
timestamp: January 21, 2019, 09:04:36 am
content: hi guysi have a problem with PCB printing with Photo resist DRY Film method. i used to 15w UV light with 395nm. my problem is after exposure with main light finished, i run operation developing with 10g sodium carbonate with 1lt water. but after developing is finished, in some space between track or polygon photo resist No light gone was exists and don't removed.please help me which step is wrong?Best RegardsEhsan Farahani

author: sleemanj
author_rank: Super Contributor
timestamp: January 21, 2019, 09:18:03 am
content: Hard to tell between english as second language and photo, but it looks like1. artwork not clamped tightly enough to board during exposure2. exposure too long3. developing too shortIt is best to do a shorter exposure time first, develop it, use a vibrating toothbrush to gently rub during developing can help, then after developing and rinsing in water, put it under UV light again (no need for the artwork, just put all under UV) for about twice as long as the initial exposure and inspect, after the second exposure it will be easy to see resist still in places it should not be if there is and you can put it back in the developing solution for a short time with toothbrush to clean that up before you etch.Fixing the developed image is a lot easier than fixing it after etching, so take your time after developing to very carefully inspect for any resist residue still left over, or any other problems.

author: ehsansis0
author_rank: Newbie
timestamp: January 21, 2019, 09:32:11 am
content: thanks very much for your response. i will add some pictures to first post. in picture i declare not removed laminate from PCB with green arrow. i will try again with 1 and 2 minutes exposure.my developing operation time around of 3 or 4 minutes.in attached picture to this post i declared full removed no light gone laminate from PCB with red arrow and exists no light gone laminate with green arrow.all pieced of my pattern printed to PCB. only i can't remove some no light gone laminate from PCB.Thanks.

author: sleemanj
author_rank: Super Contributor
timestamp: January 22, 2019, 12:10:35 am
content: Yes I would reduce exposure time.You want it first exposed so it is just enough to not be damaged when developing, depends on your UV source, but for me about 22 seconds is my initial exposure, then develop, then expose for 50 seconds or longer to harden.

author: ehsansis0
author_rank: Newbie
timestamp: January 22, 2019, 05:43:02 am
content: thanks very much dear. could you please send some pictures and information about your UV light source and after and before of exposing and developing?

author: james_s
author_rank: Super Contributor
timestamp: January 22, 2019, 06:41:34 am
content: You really need to press the artwork firmly against the board, my friend uses photo etching and he uses a heavy piece of glass, prints on tracing paper and then puts the paper print side against the board, puts the glass over that and sets a light box over that.

author: sleemanj
author_rank: Super Contributor
timestamp: January 22, 2019, 07:08:30 am
content: Quote from: ehsansis0 on January 22, 2019, 05:43:02 amhttps://sparks.gogo.co.nz/dry-film-tips.pdf

author: ehsansis0
author_rank: Newbie
timestamp: January 22, 2019, 07:34:59 am
content: I've seen it before. The documentary is very good. thanks very much for sharing document.