Found an easy way to cut FR4 - Page 1
Forum section: electronics / general

author: pastaclub
author_rank: Regular Contributor
timestamp: October 25, 2024, 03:58:12 pm
content: By coincidence, I found a great way to cut FR4 in prototyping (not in mass production).I had to cut a trace on a PCB. I used to do that with a utility knife, but I thought, why not try my new Sonic Saber (that's an ultrasonic knife sold for post processing 3D prints). I found that not only does it effortlessly cut the trace, just touching the PCB with barely any pressure literally digs into the FR4. So I explored whether I can even cut PCBs with that thing.Result: yes, an ultrasonic knife can cut FR4. It doesn't cut right through (I estimate that with minimal pressure the cut is about 0.3 to 0.5 mm deep) - which means it works the same way as a V-cut. Then you just break it off. The blade probably wears down quickly, but it's cheaper to replace than an endmill and makes way less dust. You can also run the ultrasonic knife along the edge after breaking and simple scrape off any burr to make the edge almost as smooth as machined.Not something I'd do all the time but useful once in a while. I thought I'd share this trick.

author: jpanhalt
author_rank: Super Contributor
timestamp: October 25, 2024, 08:55:12 pm
content: Prices seem to have a wide range from $289.99 on Amazon to $14.18 on AliExpress. What did you use? Can you keep a narrow kerf and straight line, as when separating tracks in FFC?

author: thm_w
author_rank: Super Contributor
timestamp: October 25, 2024, 08:57:43 pm
content: For anyone else wondering its a $250 ultrasonic handheld knife, 40kHz. Cool, thought not something I have on hand:https://phrozen3d.com/pages/sonic-saber-ultrasonic-cutterActually cheap too compared to the competition.Some previous threads:https://www.eevblog.com/forum/eda/clean-way-to-cut-fr4-pcb/(carbide laminate cutter mentioned)https://www.eevblog.com/forum/manufacture/cutting-fr4-boards/25/Quote from: jpanhalt on October 25, 2024, 08:55:12 pm$15 is just the blade, if its the same as the one I saw.

author: julian1
author_rank: Frequent Contributor
timestamp: October 25, 2024, 09:05:26 pm
content: Is fine dust/particle matter an issue with this tool?

author: jpanhalt
author_rank: Super Contributor
timestamp: October 25, 2024, 09:23:24 pm
content: Quote from: thm_w on October 25, 2024, 08:57:43 pmMy dentist uses ultrasonic stuff. I broke a tooth earlier this year and needed a crown. It was not my first crown, but it was the most pleasant. Of course, dental stuff is by definition out of my price range. $250 -- if decent quality -- is becoming almost average. My recent Milwaukee cordless drill to replace my 25+ y.o. Craftsman cordless was in that range.I probably wouldn't use it for FR4. I use a shear plus disk sanding (if needed for precision) for that.

author: RoGeorge
author_rank: Super Contributor
timestamp: October 25, 2024, 09:50:36 pm
content: Everything that make FR4 dust is bad.For DYI cuts, just scratch the copper side a few times, then place the board on the edge of the table and snap it along the scratch. Even better would be to use a guillotine made for cutting metal sheets. Can cut very well through PCB, and doesn't make any dust. For very small boards, scissors made for cutting metal sheets might work, too, but are far from good, they bend the PCB.Any power tools (or other methods that produce dust) are to be avoided. The woven in the FR4 is fiber glass, which in the dust form is very nasty for lungs. Same for the rosin that impregnates the woven. Avoid any FR4 dust.

author: jpanhalt
author_rank: Super Contributor
timestamp: October 25, 2024, 11:19:19 pm
content: The danger of fiberglass dust is way overhyped. The US OSHA classifies it as a "nuisance" dust. If worried, just use good ventilation or a face mask.

author: coppice
author_rank: Super Contributor
timestamp: October 25, 2024, 11:27:17 pm
content: Quote from: jpanhalt on October 25, 2024, 11:19:19 pmDoes it get classified as just a nuisance because its not very harmful, or because its easy to deal with?

author: jpanhalt
author_rank: Super Contributor
timestamp: October 25, 2024, 11:34:36 pm
content: The former.

author: thm_w
author_rank: Super Contributor
timestamp: October 26, 2024, 12:07:53 am
content: Yeah I was wrong about this before, probably you corrected me, glass dust is not a major issue.In this case the amount of dust is going to be minimal compared to bandsaw, machining, or abrasive cutting of FR4. I still avoid cutting FR4, as its a pain in the ass and glass fibers always embed and irritate my skin.There is some epoxy dust mixed in as well, which I don't know if we can guarantee the contents of.https://pmc.ncbi.nlm.nih.gov/articles/PMC4928277/https://www.canada.ca/en/environment-climate-change/services/evaluating-existing-substances/screening-assessment-epoxy-resins-group.html#toc21

author: coppercone2
author_rank: Super Contributor
timestamp: October 26, 2024, 03:16:37 am
content: the best way to cut FR4 is a nibbler, it has zero dust and zero injury risk at the cost of a small slice of a extremely cheap material.

author: pastaclub
author_rank: Regular Contributor
timestamp: October 27, 2024, 01:24:58 pm
content: Tool and price: I am using the Sonic Saber by Phrozen, and yes it's around 250 USD. I looked around for cheaper comparable tools before, didn't find anything. Not a must-have but it comes in handy as it allows you to cut without friction.It's very precise. I experimented some some and I was able to cut a PCB in the middle between 1.27mm pitch through hole pads (under the microscope with multiple passes). This is not something you can do with breaking or sawing. Narrow kerf: yes, the cut can be very narrow ... if it's not deep. I found that if you cut a bit deeper, the FR4 tends to delaminate. You can prevent that by doing a V-cut from two different angles, but then it becomes much wider. For this reason, the method is not good to cut all the way through. It's excellent to cut traces and to cut a shallow line for breaking afterwards.Straight line: well, only as straight as you can cut by hand. You cannot use a ruler. If you use a plastic ruler, it will just cut into it. If you use metal, it will absorb the ultrasonic.Is fine dust/particle matter an issue with this tool? With FR4, yes. Much less dust than sawing or milling, but FR4 still falls apart into dust. More dust than scratching with a regular knife.

author: G0HZU
author_rank: Super Contributor
timestamp: October 27, 2024, 01:34:03 pm
content: For cutting out rectangular PCB shapes from bare copper PCB, I use a pair of Stanley Fatmax shears. These do a great job and they don't seem to be losing sharpness. I've also got a T-Tech 7000S PCB mill that can mill and drill PCBs and cut shapes quite precisely. This vacuum vents to outside the house and I wear a FFP2 face mask when I use it. It isn't quick or easy to use though. It requires everything to be drawn using CAD tools beforehand.

author: Doctorandus_P
author_rank: Super Contributor
timestamp: October 28, 2024, 04:33:24 pm
content: A big guillotine metal shears is excellent for cutting FR4, but I just use wire cutters. Not the very small ones for electronics, but the bigger version. These work quite well for matrix board. You can cut 5 or 6 holes deep into the PCB, and this creates a weak point. After that you can grow the crack from that point further inward. It does leave an ugly edge but I grind that off with a bench grinder, combined with some dust mitigation. (I do this outside, preferably in some wind, and don't get too much of that itchy stuff on your clothes).Some time ago I also bought a sheet metal hand shears (Laoa LA119511) This sheet metal snips costs less then EUR 20. I just tried it for the first time and it also cuts though FR4 quite easily. This may well become my favourite method to cut FR4. I quite like the Laoa tools from Aliexpress. They are not the cheapest, but they are worth their money.