How to remove a big area of soldermask - Page 1
Forum section: electronics / general

author: Koen
author_rank: Frequent Contributor
timestamp: September 10, 2019, 07:48:47 pm
content: Hello, would you have any tricks to remove a massive area of soldermask from a PCB ? I forgot to clear it in the gerber. Thank you, Koen

author: SteveyG
author_rank: Unknown
timestamp: September 11, 2019, 10:18:12 am
content: I can only think an abrasive would do the job without access to more controlled equipment.

author: Fire Doger
author_rank: Regular Contributor
timestamp: September 11, 2019, 11:19:36 am
content: Laser

author: Pinkus
author_rank: Frequent Contributor
timestamp: September 11, 2019, 11:20:41 am
content: Depending on the quality of the mask lacquer it can be quite difficult. Cheap Chinese PCBs are usually easier, good quality western facilities are often using quite stable lacquer.At single prototypes I usually scratch it away with a scalpel. Otherwise my tip: throw it away and re-produce it.Edit: never thought about a laser ... indeed THAT could be a good solution for larger quantities.

author: TheHolyHorse
author_rank: Regular Contributor
timestamp: September 18, 2019, 03:24:45 pm
content: You probably need a pretty decent later though.

author: KaneTW
author_rank: Frequent Contributor
timestamp: September 18, 2019, 05:41:15 pm
content: Without knowing what soldermask was used, I can just shoot in the dark. Try dichloromethane, acetone, toluene. DCM probably the most likely to work. If that doesn't work, hot 40% sodium hydroxide solution should work.https://patents.google.com/patent/US5304252A/endescribes a aqueous solution of 5-40% alkali hydroxide and ~15% of softening agent like 2-pyrrolidone or glycol ethers. Read through the thing, or maybe just buy a commercially available stripper.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: September 18, 2019, 10:43:14 pm
content: Use DCM very carefully: it swells PCB laminate.I've seen a stiff fiberglass brush recommended for this, with or without chemicals.Tim

author: eliocor
author_rank: Unknown
timestamp: September 19, 2019, 04:58:08 am
content: https://uk.rs-online.com/web/p/pcb-cleaning-brushes/0514868/https://uk.rs-online.com/web/p/pcb-cleaning-brushes/0514874/

author: SMTech
author_rank: Frequent Contributor
timestamp: September 19, 2019, 07:37:30 am
content: Quote from: eliocor on September 19, 2019, 04:58:08 amCertainly work, be prepared for evil glass splinters in your fingers.

author: eliocor
author_rank: Unknown
timestamp: September 19, 2019, 10:49:52 am
content: No, the pen (holder) is just done for protecting your fingers and the brushes wear is very little.I have used such brushes even by hand (no holder) without any problem.Please take care that, with good soldermask, the brushing process is rather slow!

author: mrpackethead
author_rank: Super Contributor
timestamp: September 20, 2019, 05:21:13 am
content: Quote from: Pinkus on September 11, 2019, 11:20:41 amYour basing your comments about chinese PCBs on what? Actual fact or just the standard china is rubbish mindset?

author: Berni
author_rank: Super Contributor
timestamp: September 20, 2019, 05:35:39 am
content: If you just want to remove all of it then sandpaper is the easiest way.If you want it in a prceise area then a laser engraver sounds like the best bet. They are plenty powerful enough to burn off most kinds of paint and coatings but don't have nearly enough power to do anything to copper.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: September 20, 2019, 07:13:02 am
content: Quote from: mrpackethead on September 20, 2019, 05:21:13 amProtos often use a cheaper(?), weaker, glossy soldermask. This is at least true of PCB4U, PCBCart, ALLPCB and ITEAD in my experience, and most likely the other budget services.My experience with PCBCart full custom has been they use a stronger soldermask. Most western fabs use a glossy or matte formula with good to excellent strength (e.g., Advanced Circuits, Eagle Electronics, etc.).It may just be coincidence that these are all Chinese fabs using the formula in question. More likely, it's simply "you get what you pay for".Tim

author: T3sl4co1l
author_rank: Super Contributor
timestamp: September 20, 2019, 07:26:08 am
content: It's more about what you're doing. I would dare consider weaker soldermask a benefit, for proto purposes. To a point. Easier to scrape off and make new pads. Not so weak that it's flaking everywhere, of course.For production I think matte is better, something about the flow of paste?Tim

author: GerardG
author_rank: Regular Contributor
timestamp: September 27, 2019, 02:09:53 pm
content: I have used a CO2 laser to remove big areas of soldermask.Settings to 60WAfter lasering we cleaned the board with IPA.

author: HHaase
author_rank: Regular Contributor
timestamp: October 05, 2019, 01:01:17 pm
content: Some repair shops I deal with use small bead-blasters to clear large areas, though they are also usually dealing with clearing off battery corrosion too.If you go the laser route, definitely keep it in a laser-safe enclosure. Copper loves to reflect.

author: GerardG
author_rank: Regular Contributor
timestamp: October 09, 2019, 07:43:41 am
content: Thank you Blueskull for your reply.As the CO2 laser removes only the soldermask and reflected from the copper you are not removing any copper.This was a nice solution for the 12 layer PCB we had to modify.Do not position the laser on a place without copper as it will ruin your PCB.

author: Koen
author_rank: Frequent Contributor
timestamp: October 30, 2019, 09:00:56 pm
content: Thank you for all your replies. I tried solvents then fiberglass brush then laser. Laser triumphed.

author: Fire Doger
author_rank: Regular Contributor
timestamp: October 31, 2019, 09:15:39 am
content: "told ya"Can you share any pics to complete the topic?