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What catalyst can be added to a phosphoric/sulphuric acid mix to achieve a good etch rate and quality?


Dear Sir or Madam,

My company manufacture power semiconductors. The process steps are quite lengthy and have complex interactions between the parameters. In one of the stages, we try to etch aluminium. We currently use a commercial electropolish mix consisting of phosphoric and sulphuric acid with 0.5% of component X. We have tried several in-house component mix but to no avail. I thought component X might be some form of chelating agent. But recently, I have been told by another manufacturer that it is a catalyst instead. We are not getting good technical support on several contamination issues. I would like any readers out there to suggest any catalyst that I can try to achieve a good etch rate and quality.

Mervyn Seet
- Chippenham, Wiltshire, UK


If you are trying to etch quickly, and there is no reason not to, why not caustic etch? Is there another material in the item which is too sensitive to caustic, Mr. Seet?

Unless we were to investigate and verify the full lifetime biography of the responders, it would be difficult for us to know whether the responder might be illegitimately disclosing a trade secret about 'component X', so a public forum like this may not be the best place to seek to learn what 'component X' is.

Ted Mooney, finishing.com
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey

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