[labnetwork] hotplates

[Brian Baker]

Hi all,

If anyone is interested in a good quality wafer baking hot plate for cheap:

We recently purchased a few used 8" wafer baking hot plates (not for
chemical use) for $200 each.  They were originally part of a wafer track
system. We have installed and tested them and they are in excellent shape
and have very good temperature uniformity.  We also slightly modified them
so we could raise and lower the wafer off the hotplate using a switch. I can
provide information on how we did that if anyone is interested.

They don't have these listed on their website but the salesperson told me
they have dozens:

http://www.outbackequipment.com/

C73304 Wafer Coating Track Hot Plate

-Brian Baker
U of U Nanofab


From: "Luciani, Vincent" <vincent.luciani at nist.gov>
Date: November 24, 2010 10:04:50 AM MST
To: "labnetwork at mtl.mit.edu" <labnetwork at mtl.mit.edu>
Subject: Re: [labnetwork] hotplates

Hello,
I have also found that hotplates inside a fume hood have a very short life.
The best solution I have experienced is when the hotplate is remoted from
the controls with the controls outside the hood.  We also combined this with
sealing around the underside of the ceramic hotplate with the orange high
temperature RTV.  The stuff made for engine head gaskets, you can get it at
any auto parts store.  It is very chemical and heat resistant. Even on the
non-remote style, you can extend the life of the hotplate by taking it apart
and adding this RTV to seal up all the electronics, including the heater
wiring feedthroughs and the joint around the perimeter on underside of the
heated plate.  You want to keep fumes and liquids from reaching the heating
elements.  Good luck.

Vince




-----Original Message-----
From: labnetwork-bounces at mtl.mit.edu [mailto:labnetwork-bounces at mtl.mit.edu]
On Behalf Of John Shott
Sent: Wednesday, November 24, 2010 9:24 AM
To: labnetwork at mtl.mit.edu
Subject: Re: [labnetwork] hotplates

Oops, I see that I responded to Mathieu directly, but failed to also 
include my comments to the mailing list.  So, I will repeat those 
comments here.

Matt:

I hate hot plates too!  My biggest concern, however, is the safety risk 
that they pose.  As you likely know, the most-common Corning hot plates 
can reach 500 Centigrade.  I think that it is not inaccurate to say that 
hot plates have caused more cleanroom fires over the years than any of 
the other hazards with which we deal.

We've tried a number of things but, to my knowledge, we haven't really 
come up with things that we are perfectly happy with.  In fact, for 
heating significant volumes of chemicals (1-2 liters and up) we still 
use the 10" by 10" Corning ceramic tops with remote controls.  The one 
thing that we have done on those which helps with safety a bit, is to 
machine some custom stop rings that fit behind the knob on the D-shaft.  
In that way, if we decided that a particular hot plate should not be 
used at a setting higher than 4, for example, we can insure that this 
cannot happen by having a mechanical stop that prevents the knob from 
being turned past 4.

Particularly for resist bake applications, we've used a variety of 
digital hot plates including the Thermo Scientific Super-Nuova Series.  
Some of these feature an independently settable maximum surface 
temperature and come in either milled aluminun or ceramic coated 
versions for either wafer baking or chemical heating applications, 
respectively.  Torrey Pines Scientific also offer some nice digital hot 
plates that can do things like reasonably well controlled ramp rates 
that offer another useful option for resist baking and similar 
applications.  I'm not sure that we have a favorite, but I'm hopeful 
that others will add their experiences to this discussion.

Good luck,

John



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