[labnetwork] hotplates

[John Shott]

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