You can’t cheat physics…

…and neither can I.

So, where have I been? Up to no good, apparently.

Up until now, I have skipped altogether the way I was going to pattern the chips. The thing is, you can either have not super expensive paterning tools and expensive resists, or expensive tools and cheap resists.
Obtaining the expensive resists is, well…expensive, plus they are very especialized and sensitive. Also, the optical setup needed is not an easy task either. While looking into it, I found out that acrylic (PMMA) can be used as resist, however, it requires e-beam paterning, wich in turn means you need an electron microscope, wich is not cheap.

Some countries have kind of a market for secondhand electron microscopes, however mine doesn’t. The thing is, if you don’t actually need to scan the thing, but just to shoot electrons at it, could you use any other electron gun?

In theory, you could. It is not a question of voltage (this paper talks about very low voltage PMMA paterning) but to get the assembly to the adequate vacuum conditions. It is not enough to have a good mechanical vacuum pump.

In case you don’t believe me, here’s what a CRT tube does in 40 microns of Argon vacuum:

Here’s the setup:

Having proven that I needed a High vacuum pump, I started working on an oil diffusion pump.

However, the pieces I practiced on where 0,5mm stainless, wich proven trycky, but doable. The final pieces where only 0,25mm thick, wich, unfortunately, altough possible in short runs, it did pierce the sheet on start, wich left the pieces unusable. Shame, they where looking gorgeous:

Now that I had to start again and spend more money on it, a consensus was reached between me and an expert (to be mentioned when, if he, permits it) to try to go for a turbomolecular pump, wich are quicker to reach and stop vacuum, clean in their operation and they look like miniature turbines, wich, to be frank, turns me on. XD

 

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This Boring Company II

(GO TO PART I)

Finally got to install the temperature probes. I began by drilling/reaming a vertical hole from the heat face, so even if it was crooked, the start point was correct.

After that, a bigger hole was drilled on the other side to accept a ceramic separator that came with the probe:

To make space for the probe dome and cables, a sharp scrapper was used:

And it looks like this:

The ceramic retainer is attached to the metal plate with screws, with their head on the inside, so they can’t work loose. Also, dual nuts where used:

Now looks like a partial eclipse:

In the meantime, the plasma cutter arrived, and made my life much easier by allowing me to cut simple shapes with zero effort. So, a 3D model of what I wanted was made:

That was transferred to CAD, and then lasercut some MDF stencils to gide the plasma torch:


Other project stencils, but you get the point.

And panels where made.
Plasma cutting by hand (with stencils) is tricky for internal shapes, and thus, all holes had to be tweaked with a file for the modules to fit.

I am slowly getting better at welding (and thick sheet metal helps):

After power sanding:

First test fit alongside the oven:


The control box is upside down. xD

Nuts where welded to hold the cover:

And tabs where added to hold the box away enough from the oven side:

And then the integration began:

Power cabling:

A quick note on fiberglass covered power cable. You MUST crimp the ends before cutting the fiberglass, or it will unravel and create isolation issues. I did mine with some brass tube and parallel pliers:

Since I was not in the mood to make more holes in the box, I opted for the easy cable routing:

And no, the heatsinks can’t get hot enough to damage the fiberglass cable or the silicone cable, altough the second one might get sleeved up to the probes at some point. Let’s say it is workshop friendly as long as there are no kids around. XD

When you want a compact unit, things like this happen:

Testing the power section to ensure everything is ok:

I left it cooling overnight and then installed the timer. It is NOT connected to the power section, it’s just a convenient place to have a programable clock/alarm.

The controller also has a double circuit switch to deactivate the SSR’s, so the oven power is OFF but I can still monitor the temperature.
The oven now just requires some external quartz tube supports, but it can be used as is for now.

See ya!

Bore-DOOM.

Have nothing better to do? Watch a sputtering rig from start to finish:

It has time annotations so you can skip the uneventful bits.

Plasma starting is quirky:

  • With too low pressure, plasma won’t start.
  • With too high pressure, arcing will happen.
  • With too low voltage (below 300V), plasma won’t hold in the trap as pressure drops.
  • With too high voltage, but not low enough pressure yet, plasma will arc, then fade and won’t restart.

A current meter must be added to complete the graph, and see what is this thing doing. Next week, probably.

For now I ca n get away with hand-eye coordination.

Pride and Depositionize.

Today I finally started to characterize the vacuum chamber. Time vs Thickness, A-K voltage vs plasma current and Vacuum.

One thing I found out, is that my newly installed 50/100Ω ballast resistor was not performing well. It just didn’t allow the machine to operate properly (but without characterization, I am not sure where it acted)

With it, all tries ended up like the center piece. Looking like copper oxide, and with 250ohm resistance. Without the resistor, it was easier to achieve and mantain the plasma, and copper sputtered easily. (left and right, copper on glass)

The copper passed the tin-wetting and finger tests (it doesn’t smear when you rub the finger on it).

It’s also so shiny, the camera won’t focus on it, but rahter on the reflected image (ceiling)


That’s a really odd picture!

For fun, I tried to do a simple circuit on glass:


So proud!

However, the copper film was simply too thin, and the solder paste destroyed it when melting. In any case, that just requires more time in the chamber. I’ll have proper deposition figures soon.

See ya!

The Goblet of Fire

Plasma, that fourth state of matter:

-“When an ionised gaseous substance becomes highly electrically conductive to the point that long-range electric and magnetic fields dominate its behaviour.”
(wikipedia)

As you know, plasma is a quite hot stuff. Usually it’s density is so low that thermal transfer quickly reaches an equilibrium much lower than the melting point of materials. However, in a sputtering machine, you do concentrate plasma in a small area, so, continuous operation requires a bit more than just having a passive aluminium heatsink.

And yes, you can just powermelt the target:

An aluminium plate with concentrated plasma heats quickly, as I have found out. After medium sputtering runs (20/25 minutes, NO Argon), the magnets are so hot you can barely hold them in your hand. That must be around 40/50ºC, wich obviously can only get worse. Normal (cheap) neodimium magnets have a curie point of just 100ºC, so it’s better not to risk damaging them. And just because fuck yeah, I want to liquid cool it to allow extended operating time.

Let’s have some water channels cut into the plasma trap plate:

At first I was thinking about machining it by hand in stainless, as having a rotary table makes it a fairly easy task. However, later on, I realized I could simply make it in aluminium wich is a better heat conductor AND my 3020CNC can machine it, if you are patient. I’ll still have to tap all the holes by hand, but that’s a minor nuisance.

Having a laser cutter helps immensely with reducing waste (milling acrylic is a pain in the ass)

Some might say so many screws are overkill, and might be true, however, given the diameters involved, and that I am using viton O-rings wich are not super flexible either, I have just preferred going all the way. The acrylic is 7mm to ensure minimum deflection.

Yeah, I should have made the utside border a tad larger. (The inside diameter has to fit the magnets, so there’s not much room there.)

The screws are stainless steel, so I don’t think they will affect the shape of the magnetic trap.


Test fit on top of a non machined plate (with recess for the magnet)

Since I received my new 3D printer before machining the plate, I printed a 15mm section to test fit the magnets and general visual guidance, plus screw check.

The magnet slot had a bit too much room left (2mm) so it was reduced 1,25mm in Fusion. (to 40,75mm). The screw lenght allowance was correct.

Overall fit was good, so the minor changes where validated and saved.

Machining!

Spot drilling.
I was too lazy to actually make a separate program for this, so I used the same drilling program, but added a +6.5mm offset so it would only peck 1.5mm with the 90º spot drill, I know, extremely ineficient, but it would have taken longer to start the computer and actually make the program.

After drilling, the o-ring recesses where cut.

Quick seal check, just in case y messed up, or the o-rings where wrong.

As an afterthought, I could ave made the slots 0,5mm deeper, so the acrylic would fully compress the rings and sit flat against the plate, but well, as I said, an afterthought.

The magnet slot was cut first:

Then the water channels:


I know the pic is shaky, but I was busy, you know…

Little misshap with mach 3 going first to Z-Ø instad of X/Y-Ø, and a not-so-exact Z height setup. Fortunatey, the cut was ony 0,15 deep, so it doesn’t affect the overall performance, just my inner pride. (I tested a newish 2-flute endmill instead of the oldish 4-flute I was using, but it underperformed, so I changed back, and messed with the paper thickness Z height procedure. This part is not critical in the Z axis, so I wasn’t particularly worried.

Anyhow, everyone hail the awesome cooling plate:

I accept the fact that there will be some blow-by between inlet and outlet, but most of the water should still flow along the path.

Magnets!

The CNC part took 6.5h to machine in a cheap (ballscrew) 3020CNC router, with the following setup:

  • 2mm carbide 90º spot drill, 2,5mm carbide drill.
  • 8mm depth, 0,25 pecking depth. Lube between holes.
  • 2mm (R1) carbide ball endmill.
  • 4mm-4flute carbide endmill, flat, center cutting.
  • 0.5mm depth of cut up to 5mm depth (6mm for magnet), 1.25mm stepover. 75mm/min plunge. 150mm/min feed.
  • LUBE as if there was no tomorrow. Also make sure all the router bolts are tight.

These kind of machines are not particularly rigid, so this is the absolute limit of what they can do. If you are patient, tough, you will be able to squeeze it to the very last drop.

Using a locating setup, one could just machine the outside border and flip the part to machine the lip, however, since I have a lathe, I just prefer to do it there and avoid the hassle.

First, bandsaw the corners.

Chuck the plate from the inside…

…and slowly carve the diameters away.

After polishing all the important surfaces:

Oh! Also some custom fittings should be made, amirite?

So gorgeous.

In the heat exchanging department I would like to employ some passive cooling like this:

I know I could try to hook it up to one of my beer refrigeration units, however I pretty much prefer not to, because the vacuum chamber is at potential, and having liquid wiring around is…well, not my thing. Also it will make for a standalone unit (not that it is going to go anywhere, but hey, what if I want to sputter in the living room?) Should that not suffice, I can always connect it to one of the machines later, or make a heat exchanger or something.

In any case, the particulars of the radiator are irrelevant, any liquid computer cooling setup should work (to some extent, if you put a small one). So, pick your poison, as some say.

See ya!

Gatekeeper.

In the aftermath of the oil backstream, I finally set myself to give some attention to the pneumatic HVAC valve I had bought. I found this one on ebay for cheap, it was 1/3 the price of any other mechanical valve, and I figured it would not be that difficult to operate.

As I have mentioned before, from time to time, I binge-buy parts, just in case. Here, my pneumatics tray, with couplers, pressure reducers, pneumatic switces, one way valves, Y splitters and miniature manometers. Half are RC supplies and half have industrial origins.

I also had this cheap diaphragm pneumatic pump, wich, combined with some of the tray elements and spare parts from my RC  drawer, amount for a standalone pneumatic system:

Max pressure is 2 BAR, enough to operate the valve. I added a miniature reservoir so the pump only has to run briefly at machine start-up. The valve is a VM1000-4NU-00 pneumatic microswitch. (a lucky find allowed me to buy 8 of those very cheap, normally they are kidney-expensive)

The Y splitter, reservoir and manometer, are all RC air retract parts. As a bonus, here you have an X-ray of the manometer and microswitch (from my dead chanel X-Ray playground):

Once all the pieces for the control panel arrive, I’ll install the whole pneumatic circuit too.

See ya!

Thunderdrome 2

When we left last time, the sputtering power supply was halfway done. It was missing a current limiting resistor, an HV voltage divisor and proper cable management to the outside.
Finally, received the parts and got to it.

There is no point in having a power resistor without a heatsink, right? XD

Everything is held down with M6 nylon screws, wich also make good standoffs for the voltage divisor, comprised of 10*1MΩ and 1*100KΩ for a 1/10 reduction. (I didn’t had at hand a 100k, so I used 2*220K in parallel, wich is not exact, but aht I really need is a percentage to avoid multimeter breakdown, not a precision measurement.

A slot was cut in each screw so the resistor lead would get trapped with a nut, simple but effective.

I also had to deal with the M25 gland and a hole made by the previous owner for a SMEMA connector (SMT line interconexion standard). For the first, I would have preferred to have it at the bottom of the box for the 220V input line, but well, it was free, so I can’t complain much, so I just routed the cable away from everything to the bottom of the box. The other hole kinda messed up with my head. I could not realistically leave it there and/or solder something into it to make it disappear, so…

…I got wild and 3D printed a holder plate and two custom glands:

Since the HV lines also run inside silicone tube, I didn’t worry much about PLA dielectric constant and/or conductivity.


Looks neat enough.

For the internal connections I used faston connectors in the capacitor and screw-on terminals for the resistor. The divisor extremes where soldered to silicone cable.

Closeup of the setup:

Everything sits nicely and away from everything else, ensuring proper isolation up to the 2Kv+ the system is capable of. Note that the silicone cable was sleeved over the faston connectors, just in case the cable got yanked out, it doesn’t hang live on the inside of the case.

Final setup:

 

This will only require for current and voltage monitors, but I still haven’t received them yet, and they get installed on top as a “separate” unit.

Till next time!