[labnetwork] hotplates
Luciani, Vincent
vincent.luciani at nist.gov
Wed Nov 24 12:04:50 EST 2010
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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