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  for Metal Finishing since 1989
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PVD problem

I do aluminum deposition (thermal evaporation)using PVD process.There are 16 tungsten coils to be wrapped with aluminum coils. I find that in some coils the aluminum does not melt completely and globules are formed (balling effect)on the tungsten coil. Further even if we try to heat these coils the globules do not melt. I would like to know why this happens. It happens even if the contacts are cleaned thoroughly and with new coils. But this effect is not always. Also I would like to know whether all tungsten coils will have same current carrying capacity?

Regards,

Mahendra
- Nashik, Maharashtra, India
2003

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It sounds as if you could have contaminated aluminium or dirty coils , poor contacts perhaps and possibly not a low enough vacuum...

Best regards,

Andrew Taylor
- UK
2003