Kagan,

I evaporate Ni using a tungsten helix coil (not a boat) with a small piece
of Ni wire hanging on it (like a horse shoe). Heat the Ni (slowly) until it
is red hot and then go a little hotter.  When the Ni wets to the coil,
reduce heat and adjust to your evaporation rate, ~5A/sec.  I do this
everyday, it takes a little practice.

Brent

Original Message:
-----------------
From: Kagan Topalli kagan@metu.edu.tr
Date: Sun, 25 May 2008 00:11:43 +0300
To: mems-talk@memsnet.org
Subject: [mems-talk] Damaging of boats during nickel evaporation


Dear all,

I am trying to coat nickel in a thermal evaporator. I have a problem
related with the (Alumina coated) Tungsten boats where the nickel
pellets are placed in. I have observed that nickel pellets melted as I
increased the current to ~250 Amperes. After 60-70 seconds (while the
deposition was continuing without any problem), suddenly the boat has
been damaged (There occurred a hole at the mid of the boat). I have
tried the experiment with reduced number of pellets. But the result is
same. Please note that the boats can withstand even a current of 350
Amperes during gold deposition. Is there anyone that can identify the
problem? Is there any solution for that?