Author Topic: How to remove a big area of soldermask  (Read 937 times)

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Offline Koen

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How to remove a big area of soldermask
« on: September 10, 2019, 07:48:47 pm »
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
 

Offline SteveyG

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Re: How to remove a big area of soldermask
« Reply #1 on: September 11, 2019, 10:18:12 am »
I can only think an abrasive would do the job without access to more controlled equipment.

Offline Fire Doger

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Re: How to remove a big area of soldermask
« Reply #2 on: September 11, 2019, 11:19:36 am »
Laser
 

Online Pinkus

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Re: How to remove a big area of soldermask
« Reply #3 on: September 11, 2019, 11:20:41 am »
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.
 

Offline TheHolyHorse

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Re: How to remove a big area of soldermask
« Reply #4 on: September 18, 2019, 03:24:45 pm »
You probably need a pretty decent later though.
 

Online KaneTW

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Re: How to remove a big area of soldermask
« Reply #5 on: September 18, 2019, 05:41:15 pm »
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/en describes 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.
 

Offline T3sl4co1l

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Re: How to remove a big area of soldermask
« Reply #6 on: September 18, 2019, 10:43:14 pm »
Use DCM very carefully: it swells PCB laminate.

I've seen a stiff fiberglass brush recommended for this, with or without chemicals.

Tim
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Bringing a project to life?  Send me a message!
 


Offline SMTech

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Offline eliocor

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Re: How to remove a big area of soldermask
« Reply #9 on: September 19, 2019, 10:49:52 am »
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!
 

Offline mrpackethead

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Re: How to remove a big area of soldermask
« Reply #10 on: September 20, 2019, 05:21:13 am »
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.

Your basing your comments about chinese PCBs on what?  Actual fact or just the standard china is rubbish mindset?
On a quest to find increasingly complicated ways to blink things
 

Online Berni

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Re: How to remove a big area of soldermask
« Reply #11 on: September 20, 2019, 05:35:39 am »
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.
 

Offline T3sl4co1l

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Re: How to remove a big area of soldermask
« Reply #12 on: September 20, 2019, 07:13:02 am »
Your basing your comments about chinese PCBs on what?  Actual fact or just the standard china is rubbish mindset?

Protos 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
Seven Transistor Labs, LLC
Electronic design, from concept to prototype.
Bringing a project to life?  Send me a message!
 

Offline blueskull

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Re: How to remove a big area of soldermask
« Reply #13 on: September 20, 2019, 07:21:26 am »
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.).

PCBWay has now a so called advanced PCB service, which uses Japanese photopolymer solder mask.

Also, most Chinese fabs by now offer matte service, which can be better than glossy.

But I never ran into any problems with solder mask. It's always copper peel off or PCB delamination that happen first.
 

Offline T3sl4co1l

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Re: How to remove a big area of soldermask
« Reply #14 on: September 20, 2019, 07:26:08 am »
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
Seven Transistor Labs, LLC
Electronic design, from concept to prototype.
Bringing a project to life?  Send me a message!
 

Offline GerardG

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Re: How to remove a big area of soldermask
« Reply #15 on: September 27, 2019, 02:09:53 pm »
I have used a CO2 laser to remove big areas of soldermask.
Settings to 60W

After lasering we cleaned the board with IPA.

Offline HHaase

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Re: How to remove a big area of soldermask
« Reply #16 on: October 05, 2019, 01:01:17 pm »
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.
 

Offline blueskull

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Re: How to remove a big area of soldermask
« Reply #17 on: October 05, 2019, 02:17:10 pm »
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.

Especially for CO2 lasers.

1. They are collimated (which is stupid in 2019 considering the benefits and reduced cost of fiber coupled Qsw DPSS).
2. CO2 laser has two dominant peaks, 9.4um and 10.6um.
3. Copper has virtually perfect reflection at 10um.
 

Offline GerardG

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Re: How to remove a big area of soldermask
« Reply #18 on: October 09, 2019, 07:43:41 am »
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.

Offline Koen

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Re: How to remove a big area of soldermask
« Reply #19 on: October 30, 2019, 09:00:56 pm »
Thank you for all your replies. I tried solvents then fiberglass brush then laser. Laser triumphed.
 

Offline Fire Doger

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Re: How to remove a big area of soldermask
« Reply #20 on: October 31, 2019, 09:15:39 am »
"told ya" :-DD
Can you share any pics to complete the topic?
 


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