Green epoxy circuit boards are tough. Any easy way to cut them?

Thread Starter

whitehaired novice

Joined Jul 15, 2017
283
The title says it all really. I bought one of those cheap surplus circuit boards sold for the purpose of cannibalizing the parts. When it came I realized that I would be far better off if I cut the five small (about 5 mm on a side) squares out of the board. The rest of the board had nothing I could use.

I couldn't find anything to cut it including my Dremel with a diamond cut off wheel. Now maybe my wheel is worn out and I need a new one, but it seems to handle most stuff. I had to unsolder the five small spring loaded pins and resolder them to the new board--tough going for someone with my limited small muscle control.
 

jpanhalt

Joined Jan 18, 2008
8,070
I use a vinyl tile cutter from Home Depot.
upload_2018-6-12_17-37-56.png

Used to be about $25. Guess supply and demand. Look for a cheaper price. I then sand the edges on a disk sander if accuracy is needed.
 

BobTPH

Joined Jun 5, 2013
2,047
Diamond saw is good. I just bought a tiny table saw with a diamond blade, but I have not tried it yet. Previously I used a dremel with diamond wheel cutter.

Bob
 

jpanhalt

Joined Jan 18, 2008
8,070
@BobTPH
Diamond is for hard materials. Epoxy is not generally considered hard. It can be ground, but it may gum up your "diamond" saw, unless it is quite coarse.
 

Lyonspride

Joined Jan 6, 2014
137
A Dremel isn't going to do it, my weapon of choice would be my angle grinder cutting stand.......... I do have a sheet metal sheer that'll cut steel up to 6mm thick and 200mm long, but with a PCB that would either go really well or extremely badly (i'm actually going to have to try it one day) :p
 

jpanhalt

Joined Jan 18, 2008
8,070
At one point in my life, I had access to a really fine shop for making prototypes and such. A strict rule in that shop was not to use the small metal shear (e.g., a PEXTO C-throat) for cutting PCB's. The glass ruined the edge. I have the same shear in my shop now, but I never use it for PCB's. That's why I got the cheap (at that time) vinyl cutter.

Can you get by with a few cuts? Sure. But, if you do a lot of that, you will notice a rough edge on aluminum and other metals cut on the same shear.
 

jpanhalt

Joined Jan 18, 2008
8,070
PCB's are epoxy, glass fiber , and gummy copper. I used to use a carbide blade in a small (MicroMark) bench saw. It works, but I got tired of dodging the little chips. If I didn't have the vinyl cutter, that is what I would/did use. The cheap shear is so much easier to set up and makes no mess.
 

Ylli

Joined Nov 13, 2015
788
It's fiber glass, cut it like you would other glass. Make a deep scribe mark with an awl of multiple passes of an approxo knife. Then brace it on the edge of the bench and give it a good bend along the scribe. Some runs are going to get torn to pieces, but as long as you are scrapping the board anyway.
 

ebp

Joined Feb 8, 2018
2,332
I have used a diamond wheel on a rotary tool like a Dremel and it cuts extemely fast and easily and I've never had even a hint of problem with them gumming up. I've cut up a very large number of boards this way (I used to combine a bunch of small boards into a panel to save money when getting prototype boards made). Unfortunately, it seems to be hard to find decent wheels that are round, have the hole in the actual centre, have diamonds only on the edge and not on the faces and aren't too small. Good ones are available from supplies to the jewelry making arts, but they are quite expensive and generally small than I like. If you buy diamond cutoff wheels from China, beware of mandrels that might be included. My experience is that they are mostly complete and utter garbage and only slightly harder than rubber.

Do not breath the dust! I used a vacuum pickup as best I could while cutting and wore a good mask and eye protection.

I envy BobTPH for his miini table saw. I always thought that would be by far the best tool.

You can get hacksaw blades that are made with tungsten carbide particles in a binder on the edge. They work OK.

Shears do work, but the glass is murder on the blade. I have used the score-and-break method using a carbide tipped tool. It is a little slow and, like a shear, not suited for anything but straight cuts completely across a panel.

It would be difficult on a board with parts, even working from the back, but solid tungsten carbide router bits will cut well. The standard is 1/8" shank for types intended for PCB laminate, so they work in a Dremel with the little router base. Again, dust is an issue. You can find router bits specifically manufactured for PCB work on eBay. As long as you don't go with very small diameters, they are reasonably robust. Tungsten carbide is extremely brittle and small drills and router bits will break easily (small carbide drill bits will snap if you so much as give them a dirty look).
 

dl324

Joined Mar 30, 2015
9,121
I use this shear from Harbor Freight. Cost around $125, but it appears they no longer sell it...

upload_2018-6-12_17-45-32.png

But it won't work well for populated boards.

If you don't use a cutter, be mindful of fiberglass dust from FR material.
 

Thread Starter

whitehaired novice

Joined Jul 15, 2017
283
Today I found myself looking at my standard side cutters--tried to cut a small green glass epoxy board and what do you know--it worked!

Wouldn't work, probably, on a larger board but it is the small ones that I most often want to cut down.
 

DickCappels

Joined Aug 21, 2008
5,933
I've been cutting that stuff with hacksaws followed with smoothing with a file for the past 47 years. Hacksaw blades last a while and they are cheap.
 

mcgyvr

Joined Oct 15, 2009
5,394
Today I found myself looking at my standard side cutters--tried to cut a small green glass epoxy board and what do you know--it worked!

Wouldn't work, probably, on a larger board but it is the small ones that I most often want to cut down.
Yep... Even large scissors/tin snips would do the trick too..
I routinely cut them for prototype needs with a side/wire cutter if thats the only tool I have around..
Scoring with a blade then snapping works fine too..
I do have a 3ft and 4ft shear so I use that when I'm near it obviously..
 

MaxHeadRoom

Joined Jul 18, 2013
19,162
I'm fortunate to have a large selection of available tools, one I use for this is the H.S. angle grinder with a suitably thin disc.
Max.
 
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