Greetings,
I have not posted here in quite awhile, but have been building my own metalization system. Last night, I was finally able to do my first ever aluminum coating test runs. The results went way beyond my expectations. I built this small system to coat laser mirrors and other small parts. The various posts by people here were very helpful to me in developing my system.
My system consists of the following major components:
1) Edwards es200 roughing pump that was collecting dust for many years
2) MDC KMST-100-2 foreline trap(ebay)
3) 1 torr Barotron capacitance manometer rough vacuum sensor(ebay)
4) Leybold TMP150 turbomolecular pump (ebay)
5) 2 Edwards PV25PKA valves (ebay) for roughing pump isolation and Foreline
6) Veeco RG1002 Guage controller Bayard-Aplert Guage tube (ebay)
7) Leybold NT150 turbomoleculatr pump comtroller.
8) Custom 6 way 100ISO/NWF25 manifold - turned from aluminum on my lathe.
9) Eight inch Chamber - turned from aluminum on my lathe
10) Various NW25 and 100ISO fittings and adapters - turned from brass and aluminum on my lathe.
11) 2 STC 3 way Pneumatic valves to control the Edwards valves (ebay)
12) Eight inch Pyrex glass bowl for top of the chamber (Kmart)
13) various orings (online, Marco rubber)
With extensive scrounging and careful shopping I was able to put this system together for around $500.00 (US)
I used slow setting JB-weld epoxy to assemble flanges to manifolds, and feed-thru conductors to flanges. Various sources on the web indicate that this was a good cheap alternative to products like torr seal. It makes incredibly strong bonds to aluminum. I designed my epoxy joints to expose the minimum epoxy surface (annular ring) to the high vacuum. I was also careful to outgas the epoxy. To do this, I used a discarded pressure cooker as a chamber and my roughing pump to expand and remove any bubbles from the epoxy in the assembled joints. I needed to apply vacuum very slowly or the epoxy would explode out of the joints and make a mess.
My chamber now pumps down in a few minutes to 5X10-6 torr with the turbo pump. Ultimate vacuum is in the high-mid 10-7 torr range. The ultimate vacuum is very sensitive to foreline pressure. I need to warm up my single stage roughing pump well, and gas ballast it for awhile in order to get the needed rough vacuum in the range of 10-20 millitorr. I started my depositions when I reached 5X10-6 torr with the turbo.
My chamber being rather small, I used a single KJ Lesker basket emitter centered low in the chamber. This seems to be working well for now. I am using a rewound MOT and variac to hand-control the emitter power. I was very careful to baffle the throat of my turbo pump to prevent it from being in line of sight of the emitter.
For my first test run, I coated a microscope slide. I fixtured it couple of inches above the emitter. I slowly ramped the emitter voltage up to 50% rated and this melted the aluminum and coated the tungsten basket. I used a half gram or so of electrical wire for my source charge. Once this was melted, I ramped power up to 100% rated (4.65 volts for my basket source), and after a couple of seconds *poof* and I had a coating. The microscope slide went silvery/opaque, and everything in line of sight of the emitter, such as areas of my chamber bowl, acquired a silvery coating. I then turned off power to the emitter. This was very encouraging. When I examined the results, I had a beautiful shiny coating exactly where I wanted it. There were some minor pits and streaks, but I was not especially careful with cleaning the slide, so I expected this.
Next, I tried a prototype plastic part that a colleague from work wanted coated. This part was produced on a inkjet stereolythography printer, and it was a bit gunky from uncleaned process residue. I cleaned it up as best I could, and suspended it above the emitter and ran the cycle. The coating on the chamber top was a bit black this time, but the part, while not as shiny as I would like, turned out okay. I suspect the part was outgassing pretty bad. I will probably bake the next one a bit before I try coating this material again.
Finally, I ran decided to apply an unobstructed coat to the inside of the eight inch bowl that is my chamber top. It is nearly hemispherical and roughly concentric with the emitter, so I figured it would be a pretty good "best case scenario" to test. First, I scrubbed the residue of the past runs out with detergent and scotchbright then reinstalled the bowl. I then ran the coating cycle. After a few seconds at 100% power, the bowl became silvery and opaque to the glow of the emitter basket. I cut power, and examined the coating. The coating was nearly perfect.
My next improvements will be to bore more holes in the chamber wall and add flange fittings to accommodate a high voltage feed-through for plasma cleaning and a port to install a thickness monitor sensor.
I will post a few pics of my setup later.
