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Video Training Script for the Lindberg Furnance
Part 1: Introduction to Lindberg Furnace
The Lindberg furnace consists of four tube furnaces, which are used for curing polymers, sintering, and growing oxides and nitrides on silicon wafers. Let’s get familiar with the various part of the machine.
There are four main parts to the Lindberg Furnace:
- Gas flow times
- Flow meters
- Three-way valve
- Temperature controls
Let’s also introduce our lab users.
Part 2: Overview of Controls
Gas Flow Timers
There are four gas flow timers for the Lindberg Furnace. The orientation of the timers match the orientation of the tubes they correspond with. With a maximum time of 12 hours, the flow timers are used to control the time the gas flows in the furnaces. The minimum amount of time for the process to function correctly is 2 hours. When the timer reaches zero, the gas will discontinue to flow.
Flow Meters
There are three flow meters located just below the gas flow timers. Beneath each of the flow meters are two flow meter valves. The cut-off valves are the valves closest to the flow meters. The handles are at a ninety degree when the flow meters are closed. When the handles are parallel with the flow meter, they are open. The lower valves are the needle valves, which control the gas flow into the flow meters. To open the needle valves, turn the round handles counter-clockwise. The leftmost flow meter controls tube 4, which uses nitrogen gas. The middle flow meter controls tube 2. The flow meter to the right controls tube 1 which uses forming gas. Tube 3 is controlled by the mass flow controller next to the Lindberg Furnace.
Three-way Valve
Just to the right of the flow meters is the tree-way valve. This valve controls which gas flows into tube two. The two selectable gases are Oxygen and Nitrogen. The narrow pointed end of the handle should point to the gas that is being used. When tube two is not in use, the valve should be turned to the off position. When you use furnace tube 2, which performs oxidation, you must remember to make sure that the oxygen cylinder in the chase behind the Lindberg Furnace is on. In order to check that the gas pressure is sufficient, you must read the cylinder gauge closest to the cylinder. The gauge just to the left of that one indicates the gas line pressure. It should be set to approximately 25 psi. When your process is finished, the oxygen cylinder should be turned off by turning the valve clockwise.
Temperature Controls
The furnace temperature is controlled by a programmable temperature control unit. There is one control unit for every furnace. There are programmable temperature controllers on each of the temperature control units. These controllers control each of the furnace zone heaters and allow the programming of several process steps. To operate the furnaces, you must be able to perform the following steps:
- Set the appropriate atmosphere
- Load the Furnace
- Set the temperature program
- Run the process
- End the run
Part 3: Setting the Atmosphere
When you log in to the Lindberg Furnace, select the furnace tube you are going to use for your process.
The first step in setting the atmosphere is to set the gas flow timer to the length of your run. This will prevent the waste of gas in the system when your tube sits idle at the end of your run. The next step is to set the flow of gas using the flow meters. Make sure the cut-off valve is open. Then use the needle valve to set the desired amount of gas flow.
WARNING: The needle valve should never be turned all the way open or close. Over tightening of the valve could damage it.
If you want to turn off the gas flow temporarily, turn off the cut-off valve.
Part 4: Loading the Furnace
The first step in loading the furnace is to place your samples into a quartz boat which should be found in the nitrogen box next to the Lindberg Furnace.
The next step is to remove the cap on the end of the tube and place the boat just inside the opening. When that step is completed, use the metal rod to carefully push the boat to the middle of the furnace tube. You will know that it’s reached the middle when the marking on the metal rod is aligned with the metal cover at the mouth of the tube.
WARNING: Do not the metal rod touch the inside of the Furnace tube. The metal can cause damage to the quartz.
Part 5: Setting the Temperature
The first thing you need to do when you set the temperature is open the black covers below the white arrow keys on the programmable controllers on the front panel of the control unit. The run/hold, REM, and P key should be displayed. Please note that if the red light in the lower left hand corner of access temperature gauge appears, then the system has suffered an over temperature alarm. The system will not ramp up until this light is off. In order to do this, you simply need to reset the alarm by pressing the yellow button just beneath the red light.
To initiate the programming procedure, press the P key and hold until Pr1 is displayed on the program display. With Pr1 displayed, press the white arrow keys to set the first desired ramp rate in degrees Celsius per minute. Now press the P key again to display Pl1. Select the desired temperature in degrees Celsius using the arrow keys. Press the P key again to display Pd1 and set the delay time in hours at the set temperature using the arrow keys. Press the P key again to set the program and display Pr2 if needed for further process steps. Repeat the above steps for the remaining two temperature controllers.
When ready to ramp down, set the Prn to sleep, set the Pln to 25 degrees Celcius, and set the Pdn to end.
Part 6: Running and Ending the Process
To run the program, hit all three Run/Hold keys. To hold the program, allowing correction settings, hit the Run/Hold keys and then hit them again to return to run. To abort the program that is running, press the up and down arrows at the same time. When you’ve reached the end of your process, make sure that the temperature is about room temperature when the program is done. To remove the boat from the furnace, you simply need to reverse the loading procedure.
WARNING: The quartz tube and it’s cover may still be extremely hot from the process. Make sure you wear the heat resistant gloves to prevent injury. The gloves should be near the opening of the furnace tubes.
If you turned the gas on, turn it off now. When you finish using the Lindberg Furnace, leave it in a neat and orderly fashion.
Part 7: Concluding Remarks
After watching this training video you should have a good understanding of how to:
- Set the appropriate atmosphere on the furnaces
- Load the samples into the furnace
- Set the temperature program on the temperature controls
- Run and finish the process
If you have any questions, please direct them to the trainer for this equipment. Do not direct your comments to Charlie.