Underwater laser cutting and silver sintering to make ceramic circuit boards

Thermal stress cracking can be completely avoided by CO2 laser cutting thin alumina sheets underwater. I also show how to formulate and apply silver paste, then sinter in a kiln to produce double-sided ceramic printed circuit boards with conductive vias.

60W CW CO2 laser at 80% power. 10mm/sec. Standard lens focal length (50mm). 2mm water above ceramic. 180 passes to cut through 0.75mm thick alumina.

Silver paste: 97% silver powder, 3% glass powder by mass. Particle size 1 micron or less. Add poly vinyl alcohol mold release until desired consistency reached.

Paste applied with 4 mil thick vinyl stencil. Dried in air 10 minutes, then rapidly brought up to 900*C, held for 10 minutes, then rapidly brought back down to room temperature. Total cycle about 45 minutes.

I measured electrical conductivity of the finished traces from my process with vinyl stencils: 4 milliohms per square at 10 micron final thickness. This is pretty close to the Dupont published spec ( less than 2 milliohm/sq at 16 micron thick)

[bigclivedotcom]

This makes me appreciate the science behind making the ceramic dielectric barrier ozone generator plates with their metal electrodes.

[mattfleming]

"Maybe I should do that more often...."
YES YOU SHOULD.
I have never watched your content and not been fascinated and intrigued- even with subjects that I'm not that interested in.

[malachilandis]

I would enjoy seeing videos about your tools, especially the custom electronics / custom programmed devices. I feel like those are the ones that I would be the least likely to go out and make (mechanical engineer here), so seeing your methods would be useful.

[RomSerge]

My professor said before doing research first to go to a library. because 99% of the time someone is already dome in before. your video made me remember his words that i heard more than 15-20 years ago.

Thank you.

[HuygensOptics]

Loved that you took so much effort to find this method! As for ceramic PCB, the easiest way is to cut it is the "green" state (LTCC). You can then also easily create multi-layer boards and drill vias using a laser. As for your question about the crust on your silver: it is silver oxide. You can avoid this by heating in a vacuum oven. This is not complicated, just use a small surplus dental oven. These generally have a vacuum seal and can be bought very cheaply (and are programmable)

[sethphillips]

I love how the solution to both of the biggest hurdles in this project was... water. Plain water. I for one would really enjoy a video on the equipment you put together, using reflow software for that kiln is genius!

[indyguy]

100% I'd like to see videos of your raspberry pi kiln controller and any other hacked together tools you use. Your ingenuity is the reason I'm here.

[Vigilon]

The highlight of these videos is always the part where you mention how easy these things are to make at home. "The only tools we're going to use in this technique are a CO2 laser cutter and a small kiln." Always cracks me up.

[maxsmith]

I’d love to see videos going in depth about your tools and setups

[lmenascojr]

Used to work at a company that manufactured thick film substrate circuits, including screening resistors (this was in the seventies). DuPont was the place where we got our inks from. The silver conductive inks that we worked with actually included 7% or more of palladium or platinum. I recall the binder being a petroleum base. Over time the ink would dry out/get thicker in the large cold cream size jars they would come in, so we would have to add a relatively thick thinning agent to bring them back to a screenable consistency. We used 400 stainless steel mesh stretched across relatively small steel frames that fit into a semi automated screen machine. The largest ceramic we would screen would be a little more than 3 square inches. Most were the area of a 14 or 16 pin dip package. The kiln was a multi zone chain linked belt that took 35 to 100 mins for a substrate to be fired, depending on what particular inks were being fired.

On a separate question, what about cutting gorilla glass?

[TheDanyschannel]

Another incredible technique that my professors told me was way out of the scope of DIY. Your videos never disappoint. I'm thinking this + thin film sputtering + metal to glass/ceramic soldering = DIY ultra stable resistors??? A certain German volt nut might be interested...

[Kalanchoe]

this channel is one of those rare gems.

[fltching]

Spitballing here, but couldn't you cut grooves into the surface like you mentioned was possible with the water+CO2 laser combo then use the groves for the traces? Then you could control the thickness of the traces and not need a mask, just put the paste on, and wipe it off allowing the paste to get stuck in the grooves.

[Mrcaffinebean]

Listen man, I would literally watch just about any video you would make. I would DEFINITELY watch tool videos!

[dtnicholls]

A video on your kiln would be extremely interesting.

And you'll probably get a lot of interest from the metalworking community in that as well, heat treat ovens aren't cheap so a good DIY version would probably be of significant interest to many.

[anarchangel]

Definitely a video on the kiln pi. That's a very useful build. But tool videos in general are always appreciated.

[rogersj]

I'd love to see more details on the kiln, with an eye towards application to a diy metal foundry.

[bpark]

MACOR shrinks A LOT when you fire it afterword.
In order for the glass to fuse in properly, its coefficient of expansion must match that of the alumina, or it will form micro-cracks.
There is a process using manganese & molybdenum to form metal-to alumina bonds. This is used in the manufacture of argon laser tubes (mentioned in some Coherent patents), & is very robust against stress & CTE mismatch. There is also a "silver palladium" process used by RCA in the 1990's to manufacture thick-film hybrids.

[dipayanbose]

Hey, the colour of the plain glass is probably due to sodium vapour emission. The fused silica won't have that, it also won't have inherent lattice defects, maybe that's why it cuts better.

[cvoisineaddis]

I have done some rudimentary material testing, and I have to say kudos to you for going through all the effort to figure out the silver paste and get around all the stupid proprietary secrets, and sharing it with the world.