DIY multilayer PCB and FPC with circuit vinyl cutter?

Thread Starter

strantor

Joined Oct 3, 2010
5,968
I just ordered this adhesive copper foil sheet and this adhesive Capton tape sheet to try an experiment making Flexible Printed Circuits (FPC), multilayer PCBs, and multilayer FPC. In my mind, I can throw either/both of these sheet materials into my wife's Cricut vinyl cutter and cut out circuits in the exact same way it cuts out vinyl logos.
1. Stick Capton sheet to mat, cut sheet (through holes and pads) apply transfer tape, weed out cut area, apply to <something>. This will serve as solder mask. Remove transfer tape.
2. Stick copper sheet to mat, cut sheet, apply transfer tape, weed out cut area, align & apply to capton sheet from step 1. Remove transfer tape.
3. Stick Capton sheet to mat, cut sheet (through holes & vias), apply transfer tape, weed out cut area, apply to copper sheet from step 2. Remove transfer tape.
4. Stick copper sheet to mat, cut sheet, apply transfer tape, weed out cut area, align & apply to capton sheet from step 3. Remove transfer tape.
5. Stick Capton sheet to mat, cut sheet (through holes & pads), apply transfer tape, weed out cut area, apply to copper sheet from step 4. Remove transfer tape.

If you're just making a 2-sided FPC then you're done. Or, keep stacking sandwiches of capton and copper sheets until you get bored. You could start with a sheet of capton like I described above for FPC (you will end up with one sticky side you might want to clean the adhesive off) or you could start with a regular PCB. Do your first side with normal methods (routing, etching, UV, whatever) then start layering capton and copper.

What do you guys predict? Will it work? Or will it suck?

EDIT: Fixed Links
 
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Thread Starter

strantor

Joined Oct 3, 2010
5,968
Thanks mods for moving my thread, I forgot there was a subforum for this topic.

Are the Amazon links blocked for you guys? When I click them I get about:blocked, not sure if it's just my browser.

This is what I linked to (attached).

EDIT: Fixed links, removed giant screenshots from body of post
 

Attachments

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LowQCab

Joined Nov 6, 2012
2,060
If You can get the Board to work reliably,
there's still the issue of repetitive bending of the Copper.
This will "work-harden" the Copper and cause it to crack at the weakest point.

If it's only going to be bent a couple of times, you might have a workable plan.
.
.
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Thread Starter

strantor

Joined Oct 3, 2010
5,968
If You can get the Board to work reliably,
there's still the issue of repetitive bending of the Copper.
This will "work-harden" the Copper and cause it to crack at the weakest point.

If it's only going to be bent a couple of times, you might have a workable plan.
.
.
.
I planned on using them in the same way most FPCs are used, as advanced ribbon cable (imagine LCD connectors, etc) - no repetitive flexing. If it is as easy as it looks in my head (surely it isn't, things never are) then I might do it even when FPC isn't required. Just because it's (hypothetically) easier than toner transfer & etching.
 

MrSalts

Joined Apr 2, 2020
1,762
If You can get the Board to work reliably,
there's still the issue of repetitive bending of the Copper.
This will "work-harden" the Copper and cause it to crack at the weakest point.

If it's only going to be bent a couple of times, you might have a workable plan.
.
.
.
molex makes a few different flat flex cables - copper core - the most rigid are specified to flex 10k times, the most flexible are specified for a million flexes. Could you more clearly define "a couple" and "flex".
 

LowQCab

Joined Nov 6, 2012
2,060
Overall, sounds like a pretty cool plan .........

Copper is not just "Copper",
it's always alloyed with several other Modifiers / Metals to give it the properties that are desired.
I'm sure that Molex has a proprietary,
"super-secret-sauce" Copper-Alloy
that they specify just for the purpose of increased flexibility.
The same goes for Connector-Pin-Plating.
.
.
.
 

panic mode

Joined Oct 10, 2011
2,135
continuous or frequent flexing is possible is copper layer is thin enough and bending radius is sufficiently large. same goes for robotic cable which endure repetitive flexing and torsion. the wire is made of really fine strands of copper wire.
 

Ya’akov

Joined Jan 27, 2019
5,682
I suspect if you overcome the issues of vias, etc. you will still have to deal with an unexpected stiffness. If oyu include a ground plane the combination of the polyimide tape and the copper will produce something rather stiff. I think it would fold rather than flex. More layers would make this effect more pronouned,

On the other hand, “sandwich” with polyimide “bread” and copper traces “meat” might do OK.

When I get a moment I am going to try a polyimide tape / copper tape version. I will report back.
 

MrSalts

Joined Apr 2, 2020
1,762
I suspect if you overcome the issues of vias, etc. you will still have to deal with an unexpected stiffness. If oyu include a ground plane the combination of the polyimide tape and the copper will produce something rather stiff. I think it would fold rather than flex. More layers would make this effect more pronouned,

On the other hand, “sandwich” with polyimide “bread” and copper traces “meat” might do OK.

When I get a moment I am going to try a polyimide tape / copper tape version. I will report back.
It's all been done before.
46405F96-E41C-40A5-9F73-F8052C58C183.jpeg

And a four-layer flex board...
2354D4A1-6720-4304-A8BD-4A7B1D7D28A5.jpeg
 

MrSalts

Joined Apr 2, 2020
1,762
Overall, sounds like a pretty cool plan .........

Copper is not just "Copper",
it's always alloyed with several other Modifiers / Metals to give it the properties that are desired.
I'm sure that Molex has a proprietary,
"super-secret-sauce" Copper-Alloy
that they specify just for the purpose of increased flexibility.
The same goes for Connector-Pin-Plating.
.
.
.
The alloys conduct less than copper so they'll need more. The usual answer is to simply use less and support the copper foil so it doesn't crease. The molex and other Flat-Flexible Cables use 9, 12 or 16 micron thick copper. No magic alloy, just the physics of materials (ie 1/4oz copper is more flexible than 1oz copper - way more flexible. And polyimide and some fluoropolymers can make great supporting materials even though they are less than 10-microns thick).
 

Thread Starter

strantor

Joined Oct 3, 2010
5,968
I suspect if you overcome the issues of vias, etc. you will still have to deal with an unexpected stiffness. If oyu include a ground plane the combination of the polyimide tape and the copper will produce something rather stiff. I think it would fold rather than flex. More layers would make this effect more pronouned,

On the other hand, “sandwich” with polyimide “bread” and copper traces “meat” might do OK.
FWIW in my primary quest I don't really need it to flex. I just was looking for a way to DIY multi layer PCBs and the 2nd "bread" option I considered happened to be what I believe FPCs are made of and I thought "hey, I think that makes it a FPC to boot!"
When I get a moment I am going to try a polyimide tape / copper tape version. I will report back.
Well shoot, I didn't expect anyone would jump up and go try it. I hope you're slower than Amazon. Nearly every time I've had an idea that turned out to be a good one, I find that someone else already did it 50 years ago or more. Being beaten to this by mere days or hours betrayed by my own announcement would be tragically ironic.

I'm only joking of course (mostly); I do look forward to seeing your results. If either of our results show any promise, maybe this technique is something that can be developed right here on this forum thread. Maybe one day it will be a "sticky." And surely I've just doomed it by saying that.
 
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MrSalts

Joined Apr 2, 2020
1,762
FWIW in my primary quest I don't really need it to flex. I just was looking for a way to DIY multi layer PCBs and the 2nd "bread" option I considered happened to be what I believe FPCs are made of and I thought "hey, I think that makes it a FPC to boot!"

Well shoot, I didn't expect anyone would jump up and go try it. I hope you're slower than Amazon. Nearly every time I've had an idea that turned out to be a good one, I find that someone else already did it 50 years ago or more. Being beaten to this by mere days or hours betrayed by my own announcement would be tragically ironic.

I'm only joking of course (mostly); I do look forward to seeing your results. If either of our results show any promise, maybe this technique is something that can be developed right here on this forum thread. Maybe one day it will be a "sticky." And surely I've just doomed it by saying that.
I always taught my kids that "unwanted help is not help, it's a warning sign that a friend is going to be too clingy. And, if they were the ones offering unwanted help, they are the clingy one". Good luck.
 

Ya’akov

Joined Jan 27, 2019
5,682
FWIW in my primary quest I don't really need it to flex. I just was looking for a way to DIY multi layer PCBs and the 2nd "bread" option I considered happened to be what I believe FPCs are made of and I thought "hey, I think that makes it a FPC to boot!"

Well shoot, I didn't expect anyone would jump up and go try it. I hope you're slower than Amazon. Nearly every time I've had an idea that turned out to be a good one, I find that someone else already did it 50 years ago or more. Being beaten to this by mere days or hours betrayed by my own announcement would be tragically ironic.

I'm only joking of course (mostly); I do look forward to seeing your results. If either of our results show any promise, maybe this technique is something that can be developed right here on this forum thread. Maybe one day it will be a "sticky." And surely I've just doomed it by saying that.

I did try just a full width, 12.5mm trace between 2 25mm pieces of polyimide tape. I’d forgotten I was playing around making capacitors that way.

It seems promising. Just what I made could be a very low profile high current jumper. Or maybe an antenna. I need to figure out what the ampacity is.
 

Thread Starter

strantor

Joined Oct 3, 2010
5,968
I did try just a full width, 12.5mm trace between 2 25mm pieces of polyimide tape. I’d forgotten I was playing around making capacitors that way.

It seems promising. Just what I made could be a very low profile high current jumper. Or maybe an antenna. I need to figure out what the ampacity is.
Did you do it with a Cricut or comparable vinyl cutting plotter? Or did you do it by hand with an X-acto knife? Or?
Did you just happen to already have adhesive-backed copper foil laying around or what did you use?
Pictures?
 

Thread Starter

strantor

Joined Oct 3, 2010
5,968
Overall, sounds like a pretty cool plan .........

Copper is not just "Copper",
it's always alloyed with several other Modifiers / Metals to give it the properties that are desired.
I'm sure that Molex has a proprietary,
"super-secret-sauce" Copper-Alloy
that they specify just for the purpose of increased flexibility.
The same goes for Connector-Pin-Plating.
.
.
.
Good call. Here are some copper alloys used in commercial FPCs. I will manage my expectations of any gymnastic ability from my copper meat sandwiches but the multi-layer aspect was the more alluring one for me anyway. If it works at all (in configurations more complex than @Ya’akov's 1/2" high current jumper/antenna), that will be a major victory. If it is then also flexible enough to join two PCBs at 90 degrees and never move again, that will be icing on the cake.
 
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Ya’akov

Joined Jan 27, 2019
5,682
Did you do it with a Cricut or comparable vinyl cutting plotter? Or did you do it by hand with an X-acto knife? Or?
Did you just happen to already have adhesive-backed copper foil laying around or what did you use?
Pictures?
I have adhesive backed copper foil in 6.5mm, 12.5mm, and 25mm. I have polyimide tape in similar sizes. The tape is the kind used, for among other things, stained glass work.
 

Thread Starter

strantor

Joined Oct 3, 2010
5,968
I have adhesive backed copper foil in 6.5mm, 12.5mm, and 25mm. I have polyimide tape in similar sizes. The tape is the kind used, for among other things, stained glass work.
I have a roll of polyamide tape somewhere, can't remember the last time I saw it. I didn't know that adhesive-backed sheets of copper foil or polyamide were even a thing until I searched for them. What do you use the adhesive-backed copper for?
 

Ya’akov

Joined Jan 27, 2019
5,682
I have a roll of polyamide tape somewhere, can't remember the last time I saw it. I didn't know that adhesive-backed sheets of copper foil or polyamide were even a thing until I searched for them. What do you use the adhesive-backed copper for?
I use it for trace repairs and shielding mostly. Occasionally for a repair of something similar. I have a lot of materials because I always want to have the right thing for a job. Tapes, glues, solvents, lubricants, wipes, swabs, ziplock bags in various sizes for components and hardware... etc.

I really like to have the right thing for whatever comes up.

tempImageCE0Asm.gif
 

Thread Starter

strantor

Joined Oct 3, 2010
5,968
I have results to report, not good.

I tried cutting the copper from front and back. Neither way worked. Cutting from the front, the copper traces and pads were lifting off. Cutting from the back, the paper was lifting off. I tried many different blades and settings, then my wife did. If she can't make it work then odds are it doesn't work.

20220528_223751.jpg

20220528_223813.jpg

Tried it with just regular vinyl and got the same result.
20220528_184851.jpg

I think the details are just too fine in this board I chose as a test. I think it probably would work for something with thicker traces and bigger pads. I will try a simpler board but I chose this on purpose because it is representative of the boards I want to make with regards to trace width, pin pitch, etc.

I have ordered some thicker copper foil. This stuff i got is .035mm thick, about a 1oz PCB thickness. Just ordered some 0.1mm thick, about 3oz PCB thickness. Will see if that does any better.

Another experiment I hope to get to this weekend, is to take a regular copper clad FR4 board, adhere a sheet of vinyl to it, and throw it in the cricut. Let the cricut cut out a circuit directly on the board, weed out the vinyl, then etch using the remaining vinyl as an etch resist (ferric chloride). I doubt the vinyl will adequately protect the copper under it, but we will see. I have limited hope that since the vinyl is being cut on the board as opposed to suck on afterwards, the knife will leave a nice natural seal around all the edges it cuts.

Here are some challenges I faced:
  • Cricut software will only let you import BMP, JPG, PNG, GIF, HEIC, DXF OR SVG. Only two of those are parametric files AFAIK so the rest will suffer from scaling.
    • Eagle doesn't export SVG
    • Cricut doesn't import DFX worth a damn. (All pads and vias missing, other components missing, scaling is wrong, some traces taper off and fizzle out into nothing)
    • Eagle doesn't export DXF worth a damn. (Hashes are not correct. Things like header pin holes are completely filled. You can modify the block in Autocad to fix them and they all get fixed at once, but now the traces going to them are present inside all the holes. So you have to go into each hole and clean it out. Same for vias)
    • Eagle only properly exports PDF, but then, not at high enough resolution to take a screenshot and import into cricut.
    • The only way I found to get a decent transfer from eagle to cricut is to export as DXF, touch up in Autocad, export to BMP from Autocad at 600+ dpi resolution, import to cricut. That works but it's a PITA
  • I hadn't considered this before, but for the capton layers, you actually have to have something to print (cut). It's not like with a PCB where you do one side of the board, do the other side, and the part in the middle is magic. You have to generate a file for the middle. Through-holes and vias. If you're doing more than 2 layers, your middle-files will be different from each other.
I haven't tried cutting the capton yet, didn't get around to it. Wanted to make sure I could cut the copper first. But I will probably try it tomorrow.

It occurred to me that, since this is a vinyl cutter after all, I could just cut out a silkscreen out of vinyl.
 
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