Black wax (apiezon) is no good for KOH. It's good for HF+HNO3+ systems. Try
protek from brewer.
Shay

-----Original Message-----
From: mems-talk-bounces@memsnet.org [mailto:mems-talk-bounces@memsnet.org]
On Behalf Of Chin-Jen Chiang
Sent: Tuesday, November 06, 2007 1:44 AM
To: mems-talk@memsnet.org
Subject: [mems-talk] black wax for koh etch

Hi guys,

  For some reasons I can't use nitride or oxide layer as etch mask for KOH
etching in my process and plan to use black wax as etch mask. Do you know
where I can get the black wax. Dose the black wax need to be special one or
the regular black wax used to wax car is fine. I will appreciate your
advice. Thanks.