Manufacturing Chromium Powder for Sputter Targets
A sputtering target is used to make thin films through a process called sputter deposition. The process takes a solid material, breaks it down into small particles using gaseous ions, and then sprays it onto another material. This process is often used to make computer chips and semiconductors, and it often uses Chromium powder. The process of changing Chrome Ore over into electrolytic Chromium metal to use in sputtering is fairly straightforward.
This Process Involves a Few Specific Steps
Step 1: First, the Chrome Ore must be dissolved into a solution that can be used in the electrolytic process. Generally, either a Chromic acid or a Chrome alum sulfate solution is used. A Chromic acid is a Hexavalent process, while the Chrome alum sulfate results in a trivalent process. The correct process depends on how pure the Chromium needs to be. For a sputter target that requires 99.9%+ pure Chromium, a Hexavalent process is required since it results in a much higher purity level than the trivalent process. A trivalent process, on the other hand, is more efficient and is the better option when purity isn’t a factor. The trivalent process can produce highly pure Chromium, but it’s inconsistent.
The final resulting powder should be completely free of Hexavalent Chrome. Any of that material in the Chrome Ore should be converted to inert Chromium metal during the electrolytic process. Random samples should be taken during the process to test for the presence of Hexavalent Chrome.
Step 2: The next step is to degas the electrolytic Chromium using a high temperature hydrogen reduction. This keeps the Sulfur and Oxygen levels within the required range. The end application of the Chromium will determine what degree of degassing is needed. Degassing can be done with Chromium in its pre-crushed powder form or flake form.
Step 3: After degassing, the Chromium is crushed using impact mills to achieve the proper particle size. Special materials are used to crush the Chromium in order to reduce the likelihood of any trace elements contamination. Milling can be done in an inert atmosphere if the oxygen levels required are critical to the final result. The powder should then be blended to create a homogeneous free flowing lot.
In order to guarantee that all targets made from the same batch of Chromium powder perform identically, particles must be distrusted consistently from batch to batch during the milling process. This can be achieved by very carefully controlling the milling process.
Step 4: Samples should be periodically taken from the run in order to check for tap density, particle size distribution, and chemistry. This will ensure that the powder meets all manufacturer requirements before it’s used in the sputter targeting process. Random samples should be taken throughout the process to make certain that the quality of the batch has not changed.
What You Get as the Final Result
The final Chromium powder can be customized to meet our customers specifications for size, purity and density. Exotech’s Chromium Powder ranges in purity from 99.7% to as high as 99.98% if required. We can control critical elements such as Al, Si, Fe, O2 and many others to meet specifications.
Our Chromium nugget products come in sizes such as 0.5 – 1.5mm, 1 – 3mm, 2 – 4mm and 4 – 6mm. We stock our Chromium powder products in sizes of -50 mesh, -60 mesh, – 80 mesh, -100 mesh, -270 mesh, and -325 mesh. Exotech is also now manufacturing fine mesh sizes such as -20 micron, -25 micron and -30 micron.
Exotech produces all of our Chromium Powder in house in Pompano Beach, FL. We use a variety of raw materials, including flake, nugget and recycled/scrap materials. Please email us your specifications and we will be glad to provide prompt pricing and lead time.