Jia,

Some of the units have a small vacuum buffer (tank). When resist it sucked
in, it sometimes goes there and blocks the entrance. If you have one, remove
it, clean and try again. Also, the chuck shaft has vacuum seals. If you
misplaced or damaged them, the vacuum will leak.

shay

-----Original Message-----
From: mems-talk-bounces+shay=mizur.com@memsnet.org
[mailto:mems-talk-bounces+shay=mizur.com@memsnet.org] On Behalf Of Brad
Cantos
Sent: Thursday, December 09, 2010 9:30 PM
To: General MEMS discussion
Subject: Re: [mems-talk] spin coater vacuum path

Jia,

I'm not familiar with this particular Laurel unit, but most spinners have a
vacuum interlock switch that prevents spinning if there is insufficient
vacuum at the chuck.  This can often get stuck if photoresist gets down the
shaft.  If your switch is making partial contact, it could explain some of
the symptoms that you are seeing.  I would look for this interlock switch
and clean it just as you did the solenoid.

Brad Cantos