A blog on the repair, operation and calibration of surface analysis systems and components including electron spectrometers, sputter ion guns and vacuum related hardware. Click on the Index tab below to see a list of all posts. Visit our website at http://www.rbdinstruments.com
Category Archives: General Optics and Vacuum
General information on repair, maintenance, and operation of both PHI (Physical Electronics) and other manufacturers’ systems and components
The DGC III ion gauge controller (also called the DIG 3) used on many of the older PHI surface analysis systems can operate 2 ion gauges (only one at a time). There is a relay inside the DGC III that puts the filament current output to the ion gauge connectors on the back of the DGC III. Normally there is only one ion gauge on the vacuum chamber and it is plugged into the Ion Gauge 1 connector (normally closed) on the back of the DGC III. The relay is shown in the photo below.
DGC III filament select relay
If your DGC III does not read correctly, you can first check the +/-12V and +5V power supplies. Here is a link to some information on how to do that – DGC III power supplies test. If any of the power supplies are low and have a high AC component, then usually that issue is caused by a leaky capacitor on the power supply board. ** CAUTION! Make sure that someone who is trained on working safely with voltages up to 500V performs the voltage measurements. There are potentially lethal voltages inside the DGC III.**
If the power supplies check out OK then it is possible that the filament select relay is dirty. To test that, make sure that the DGC III is OFF and then move the black filament cable on the back of the DGC III from filament 1 to filament 2. You do not need to move the COL BNC cable as those are both tied together.
Turn the DGC III back on and press the 2 button. That will select ion gauge 2. Press the I/T 3 button to measure the vacuum and see if the DGC III works normally. If it does, then the filament select relay is dirty. You can just keep the ion gauge connected to ion gauge 2, or, you can clean the relay and connect the ion gauge back to ion gauge 1.
To clean the relay, make sure that the power is OFF to the DGC III and if not already down, pull the unit out of the rack and remove the cover.
Pull the relay out and remove the 4 screws on the bottom of the relay.
The contacts that are touching are the normally closed ion gauge 1 contacts. Use a small strip of some very fine emery cloth or sandpaper to gently clean the contacts on both sides. Then, use a small strip of paper with some isopropyl alcohol on it to remove the leftover grit. Replace the cover on the relay and reinstall the relay.
Ion gauge 1 should work properly now but if not you can order a new relay from companies like Grainger or Mouser. Just make sure that the pins match schematic that is on the side of the relay. Google 105 3PDT 10A relay and you will find it.
If your DGC III does not work and you need some help or a loaner, please contact RBD Instruments for assistance.
The raster size potentiometers that are used in the 11-065 ion gun control are coarse single turn potentiometers that make it difficult to accurately reproduce raster sizes.
By replacing the single turn potentiometers with 10-turn 1% potentiometers, the accuracy of the raster sizes is greatly improved. This will improve the repeatability of your sputter rates when changing raster sizes. One turn of the raster size potentiometer will now equal 1 mm instead of 10 mm.
When you replace the 25 kΩ 1-turn deflection potentiometers in the 11-065 with 25 kΩ 10-turn potentiometers, note that CCW = black and CW = solid brown. The other wires are the wipers.
You will also need to replace the one turn raster size knobs with a 10 turn vernier dial.
TIP: When removing the old potentiometers you can simply cut the tabs off the old ones and then insert and solder the tabs into the new potentiometer. That is much easier than un-soldering the wires from the old potentiometers.
It is very important that the CW, CCW and wipers wires match up with the old potentiometers. Otherwise the raster sizes might be backwards (0 = full raster and 10 = zero raster.
If your 11-065 controller ever needs repair and you send it to RBD Instruments, we will ask you if you would like us to add this update to your 11-065 as part of the repair.
If you are new to UHV vacuum chambers and how to create a seal using copper gaskets when mounting optics, this blog post has some useful tips.
In many cases, installing the copper gaskets that are used to seal flanges on UHV vacuum chambers is as simple as placing the copper gasket in the knife edge recess. If the flange is facing down, then the gasket can be placed on the optics part being installed and the gasket will stay in place.
But in cases where the flange is perpendicular to the floor, the gasket will not stay in place on its own because the gravitational constant will prevent the gasket from staying in place. In other words, the gasket will fall.
There are a few ways to install a gasket onto the flange. But first, you need to make sure you’ve removed the old gasket properly.
Removing Gaskets
When you remove the old gaskets, you want to be very careful not to nick the knife edge on the flange when removing the old copper gasket because a nicked knife edge often results in a vacuum leak. And, nicked knife edges are difficult and sometimes very expensive to repair.
Usually the gaskets will come off easily with a minimum amount of force. For those gaskets that are pressed in tightly and very hard to remove, I have found that using a long-nosed vice grips locking pliers works quite well.
You can adjust the gap on the pliers so that it firmly clamps down on the gasket, then simply bend the pliers so that the leverage will pop the gasket off the flange. It works every time and most importantly, it follows the number one rule of flanges – protect the knife edge. You can use a screwdriver to pry up the edge of the gasket, but if the screwdriver slips, you risk damaging the knife edge.
The first method is to use a gasket clip. Gasket clips hold the copper gasket to the flange via a spring action. They line up with the flange’s leak check groove and hold the gasket in an area that is just past the knife edge of the flange.
Here is a link to the gasket clips that Ideal Vac provides:
Gasket clips work well most of the time. Sometimes they will not work due to geometry limitations with other nearby flanges or optics.
If you do not have gasket clips, there are some other ways to mount a copper gasket to a horizontal flange.
Method 2: Elongate the Gasket
The second method is to elongate the gasket. This works well for larger copper gaskets, such as those for 10-inch and 8-inch flanges. It works with smaller gaskets as well, but you will need to drop them from a higher distance from the floor.
For an 8-inch gasket, hold the gasket about 1 foot above the floor. Hard concrete floors work best. This technique will not work on carpet.
Drop the gasket on its edge and it will hit the floor and bounce back up. You need to catch it when it bounces back up. If you don’t catch it and it falls to the floor, that is OK. You will just need to clean the gasket off with some isopropanol or methanol.
It takes a little bit of practice to get the correct height from which you are dropping the gasket. But the general rule is that the smaller the gasket, the higher the height. I have used this technique on 10-inch to 4.5-inch gaskets with good results. 10-inch flange gaskets should be dropped from about 6 inches. 4.5-inch gaskets should be dropped from about 18 inches. 2.75-inch gaskets are more difficult as they are harder to deform than the larger gaskets.
When you insert the gasket into the flange, you need to press it into the knife edge recess. The slight elongation will act like a spring and the gasket will stay in place.
Method 3: Cellophane (Scotch) Tape
Which brings us to the third method for mounting copper gaskets – cellophane (Scotch) tape.
You can use Scotch tape to mount the gasket as long as the tape is just barely on the gasket. Since the tape is mounted outside the knife edge, then it is OK if any of the tape stays on the gasket because it will be on the air side of the knife edge.
The pictures below show the knife edge cuts on common gasket sizes. For most copper gaskets (2.75- to 10-inch flange sizes) the knife edge is approximately .100 inches from the outside edge of the gasket. For the very small 1.33” flange, it is .050 inches from the gasket’s outside edge.
The procedure is to place the tape to where it is barely on the gasket (outside the knife edge region) and then very lightly touch the flange. You can use 2 or 3 sections of tape as needed.
Once you get the optics part mounted to the flange with just a few nuts or bolts to hold it in place, pull the tape straight up and away from the flange. Usually all of the tape will come out. But if any small piece of tape is left behind, it will not matter since it is on the air side of the knife edge and will not have an effect on the vacuum.
Rotate the flange slightly to make sure that the copper gasket is properly seated before you tighten the bolts.
And don’t forget that if you are up to air for awhile and need to cover a flange or optics component with aluminum foil, you should use a UHV foil such as All Foils. UHV foil does not have an oil coating on it like foil from the super market does.
There are 2 schools of thought on tightening copper CF gaskets. The most prevalent is to use a star pattern where you crisscross the bolts that you are tightening as shown in the drawing below.
Star pattern method of tightening bolts on a CF flange
The other method is to simply tighten in a circle pattern (which is the method that I prefer). The trick with this method is that you need to use very small increments of increased torgue as you move from one bolt to the next, otherwise you can over-tighten one section of the gasket or possibly bend the flange out of shape which would result in a leak. But, going in a circle is easier to keep track of which bolt is next.
Here are some links to other posts on the subject of how to tighten a CF copper gasket, so that you can make your own decision on which way is best. The top link has some information on recommended torgue for different size flanges.
