Photoresist Puns

I am using photoresist technique to make a watch dial. I first apply the photoresist, develop it then electroplate and remove the photoresist. The watch dial has quite small font and other fine details. When doing the developing the photoresist I feel like I am 80% there however I don’t feel like I am getting the fine details like I should and the font is just about legible.

I know I should be able to get this level of detail. When doing a photoresist are there techniques to get fine level of detail?

Lastly I am using 2 layers of transparency paper that have my design on it to form my image. Is it possible to do a good photoresist with just one layer of transparency paper with my design on i if my goal is not to etch with ferric acid but prevent any plating from binding to those areas?

When working with photoresist film, do I need to be working in the dark, or need a specific type of light so that I won't prematurely expose the film?

Looking to adapt some of the pcb board making methodology to do some electroplating masking. Are there any real difference in photoresist films or are some really better than others? If there are some that give consistent quality results, mind sharing them?

Has anyone encountered a problem where they stick the dry film to the board, expose it, remove the cover, developed it, and the film looks property developed and readt to etch, but there is still a super thin layer of the film covering everything and it prevents the etching?

Usually when I expose photoresist and develop it immediately afterwards, there is a clear and discernible pattern. This time, I exposed it under a 13-watt CFL for 45 minutes, and then went away for 30 minutes. When I developed it, it was completely blank and everything dissolved. I'm still experimenting with the process, but previously when I exposed it under the same CFL for 30 minutes and developed it immediately afterwards there was a discernible pattern (albeit underexposed and with a lot of broken traces).

I'm using generic purple photoresist from China (Taobao), developing using sodium carbonate.

I'm an engineer - There seem to be a lot of equations describing in depth mechanisms - for example I theoretically understand that this one resist is chemically amplified. Meaning on UV exposure each photon generates a H+, and when baked afterwards this H+ allows some kind of formaldehyde-melamine cross-linking reaction wherein these crosslinked areas are insoluble (not to mention surface inhibition due to base contamination to some depth that is never given anywhere). It goes further as there are bleaching dyes (which I can't find what compound/how they work) that cause exposed regions to decrease in absorptivity, allowing more uniform reaction in thickness down the resist. This particular crosslinking resist does not bleach and so theoretically only the first few microns of resist get exposed, so further down there is lateral development allowing different post-processing procedures to be performed. However, for example, I can't find anywhere how the rate of absorptivity decreases as a function of Z thickness, how the H+ diffuses during the bake, what the actual photoacid generator is... There are many basic articles on lithography but where is this specific info? What's the use of all the dang equations if there are no datatables to fill them in and apply them!

Sorry, maybe a rant. I am part of SPIE but that is super cutting edge stuff only. I feel like photoresist chemistry would/should be a hugely profitable and thus researched subset of chemistry...

Hello all,

Im struggling with developing the UV dry film after curing. I’ve tried Sodium Carbonate (as recommended by the manufacturer) in strengths 1-3% and at different temperatures with varying degrees of success, more often with larger traces.

I’m currently trying to etch some very thin 0.25mm) and close together (0.35mm) traces and cannot get the development right. Either the un-cured film isn’t completely dissolved or the whole resist eventually gives up and floats away as a spongey, blue, afro-jellyfish. I’ve tried gentle persuasion with a brush and sponge - which helped with the larger parts but no dice this time.

Any suggestions? Is there a better developing agent?

P.s I’ve also tried the toner transfer method to death and I can’t say I like it much.

Thanks!

So I watched a video on youtube that toured PCBWay and they used a transparent sheet with the mask printed on to harden specific areas on the PCB during manufacturing.

Obviously, the quality of the traces is directly tied to the quality of the mask. But how do they print the mask? I've seen other Youtube videos make their own mask from their home laser printer and it's not up to par for thin traces less than 1mm or between traces less than 1mm.

I know they get theirs professionally done but I guess what I'm asking is how are such high quality masks produced?

EDIT: Found it. The pros use a photoplotter which is a special laser printer with around 26000 dpi.

Hello,

I've been experimenting with dry film photoresist for a while. After getting film adhesion perfect, and film exposure very good, I'm turning my focus to the master artwork (copper layer). I am using an HP Deskjet F2430 (inkjet) to print onto a transparency sheet (doubled), using black ink on the printers "Best" setting- I believe it is printing at 600 DPI. While examining the art under a microscope, I noticed the printed areas are blotchy and littered with pinholes, often blending together into the traces. As I double up the transparencies anyway, this is probably not an issue due to inconsistencies of the blotches. What's strange however, when I set my printer to "Draft" it spits out the image much faster, but also razor sharp and void of holes. I'm guessing "Best" applies multiple passes or something? I would obviously stick with that setting if it weren't for the print head skating around, causing parts of the board to become misaligned (my guess is the printer is moving so fast, not sure though).

I'm curious to see if anyone has also experienced something similar. Do you think I can achieve a sharper image with laser? My little research says not really.

https://preview.redd.it/4vbc2kx9h9c51.jpg?width=640&format=pjpg&auto=webp&s=546492cbe82517395976dcc1fa30119bf1eb5d63

https://preview.redd.it/ye59ghw9h9c51.jpg?width=640&format=pjpg&auto=webp&s=f9f23eacde0982fc02685f906f81190b662c525c

Usually when I expose photoresist and develop it immediately afterwards, there is a clear and discernible pattern. This time, I exposed it under a 13-watt CFL for 45 minutes, and then went away for 30 minutes. When I developed it, it was completely blank and everything dissolved. I'm still experimenting with the process, but previously when I exposed it under the same CFL for 30 minutes and developed it immediately afterwards there was a discernible pattern (albeit underexposed and with a lot of broken traces).

I'm using generic purple photoresist from China (Taobao), developing using sodium carbonate.