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Thermic Edge LTD.
30 Brunel Road,
St. Leonards on Sea,
East Sussex
TN38 9RT
England
 
Telephone:
+44(0)1424 850811
 
E-mail:
sales@thermic-edge.com
 
 
 
 
 
 

Carbon & graphite overviewMaterial grades and specificationsGraphite heating elements

Vacuum heaters, heating elements, hot stages, single and multi wafer in vacuum heating, baking and vacuum wafer annealing, high vacuum and ultra high vacuum UHV wafer heating, UHV chamber baking and UHV wafer annealing, heater power supply unit.

We can offer a range of solutions for in vacuum heating, baking and vacuum wafer annealing, using different types of vacuum heaters and in vacuum heating elements. The pictures above show various types of resistance heating elements, both tubular and flat wafer heaters. We can also offer in vacuum halogen heaters. The pictures below show our plain high density graphite and carbon carbon composite (CCC) heating elements for low vacuum applications and for high vacuum, ultra high vacuum (UHV) or corrosive environments our silicon carbide, pyrolytic boron nitride (PBN) or pyrolytic graphite (PG) coated high density graphite and carbon carbon composite elements, in addition we supply our ultra low mass solid state pyrolytic boron nitride / pyrolytic graphite ( PG/PBN) composite ceramic elements.

Please contact us directly to discuss your vacuum heating requirement in more detail so that we can offer the best solution for your application. All of our heaters can be manufactured / modified to suit individual requirements, and we specialise in producing one off bespoke heaters. Below we detail the different types of our vacuum heaters, their properties and characteristics. We also manufacture a power supply to power our halogen heaters and ceramic topped resistance elements. Details of this are also shown below:-

 

Ceramic Toped Resistance Element

Our most cost effective and versatile heating element, is UHV compatible can be run in air and in any orientation and is not greatly effected by deposition product. It is very uniform and ideal for single wafer heating or annealing, either radiating onto a substrate or by placing the wafer directly onto the ceramic top plate. Can be supplied with central hole for stage shaft to pass through. Max element temperature is 1000 deg C using refractory metal housing or 700 deg C with standard stainless steel housing. Size range is from Ø3" to Ø12" (ceramic top plate diameter). Standard element is supplied with M6 central mounting stud on back of element casing. Options include secondary heat shields and water cooled outer heat shield. Can be used as a direct replacement for halogen heaters running off the same power supply. Element resistance and power requirement can tailored to suit existing power supplies. This element can be powered by our BOC6 power supply detailed below.

 

Halogen Heater

500w, 240v ac single halogen bulb with stainless steel reflector. Is ideal for chamber baking or substrate heating. Supplied with L shaped mounting bracket on back of reflector housing. Is suitable for UHV applications and a single lamp is capable of heating a substrate to 400°C. Can provide very rapid heating with a very low thermal mass, therefore allowing heating to be stopped instantly, but performance can be greatly effected by deposition build up on halogen bulb. These heaters can be powered by our BOC6 power supply detailed below.

 

 

Ceramic Pyrolytic Boron Nitride / Pyrolytic Graphite (PG/PBN) Composite Element

A very low mass (<1mm thick) fast response element with excellent chemical resistance and very high uniformity due to its layered pyrolytic structure. Its operating temperature is <900°C in Oxygen, >2000°C in vacuum or inert atmosphere (with N2 present). It is ideal for UHV environments and perfect for heating small samples < Ø1" which can be placed directly onto the element. Flat elements can be made > Ø6" and cylindrical elements can also be manufactured. Element cost is high compared to ceramic topped resistance element. It is not greatly effected by deposition product. These elements can be powered by our BOC6 power supply detailed below.

High Density Graphite Heating Element (Uncoated)

High density graphite elements are brittle, inexpensive and machined conventionally from large blocks, therefore very large sized elements can be produced in a variety of shapes and sizes. This material has a low expansion coefficient and is not degraded by constant heating and cooling. Uncoated it is not suitable for UHV due to its open porosity (10-20%), and particle contamination can also be a problem. Its low resistivity means it requires high current power supplies and therefore large feedthroughs and cables which can be expensive. It can operate up to 2000 °C in an inert atmosphere, 1800°C in vacuum and <500°C if oxygen is present. Deposition product can cause electrical shorts and thus problems with supporting weak sagging element designs.

Carbon Carbon Composite Heating Element (Uncoated)

Carbon Carbon Composite has all of the properties of the high density graphite elements but it is much stronger and more robust. It can still need to be supported in larger diameters to avoid the element from sagging, and particle contamination and outgassing are still a problem. Very thin <1mm carbon carbon composite elements can be manufactured, giving the heater the benefit of low thermal mass and a higher resistance. Carbon carbon composite raw material is manufactured in square plates with a limited maximum thickness of <30mm, therefore putting constraints on element designs.

 

 

 

 

 

 

 

 

 

Silicon Carbide, Pyrolytic Graphite, Vitreous Carbon and PBN Coatings, Plus Vitreous Carbon Impregnation On Graphite

To stop the problems of outgassing, particle contamination and oxidation that occurs with high density graphite and carbon carbon composite elements, there are various coatings that can be applied as follows:

Pyrolytic Graphite Coating ( PG ): This can be applied by a CVD method to high density graphite and carbon carbon composite elements (see picture top left). It is still electrically conductive, but it totally seals the surface porosity and therefore traps any particles. Pyrolytic graphite coating is chemically the same as high density graphite and ccc and so will still react chemically in the same way and with oxygen at 500°C.

Vitreous Carbon Coating / Impregnation: Vitreous carbon surface treatment is a cheap alternative to pyrolytic graphite coating, and is produced by vitrifying a resin applied to the surface of the high density graphite component. It seals in the particles but does not totally seal the porosity, although it can be drastically reduced. Vitreous carbon coating is better at sealing the porosity than the impregnation and gives a nice black glassy appearance to the component. It is chemically the same as high density graphite and so will still react chemically in the same way and with oxygen at 500°C.

Silicon Carbide Coating ( SiC ): Is a dark grey coating applied by a CVD method to specific grades of high density graphite. This silicon carbide ( SiC ) coating is an electrical insulator and therefore can not be applied to the electrical contact points on the element (see picture middle left). We can supply a SiC pain that can be applied to connection points after connection has been made. This paint is then thermally cured. The silicon carbide coating can operate in oxygen environments up to 1400°C and can resist some chemically corrosive environments better than graphite.

Pyrolytic Boron Nitride Coating ( PBN ): This white Pyrolytic Boron Nitride coating can be applied to very specific grades of high density graphite (see picture bottom left) to seal the porosity and improve the oxidation and chemical resistance of the element. It will oxidise at 900°C if oxygen is present, but can withstand 2000°C in an inert atmosphere or vacuum (with N2 present).

Ceramic Insulated Resistance Element (used in atmosphere not vacuum)

This tubular element is used to surround and heat a quartz vacuum envelope containing the sample or wafers to be heater. Various sizes are available and can heat to temperatures of up to 900°C.

BOC6 Sample resistive heating system

  • 99 Hour timer

  • 3 KW “toggle” control system

  • Compact 2U rack mount

  • Up to 4 heaters

  • Expandable slave unit option

 

The BOC-6 is a simple yet robustly designed 6KW output sample resistive heater controller and power supply combined. A simple “toggle”system allows the user to select a permanent 3 KW of heat to maintain temperature at a user defined set point and a further 3KW of intermittent incremental power that cuts in at a user selected temperature delta to primary set point. This method of power distribution together with up to four sample heaters of 1.5KW max output each, (or slaving an additional 4 when used with the optional slave unit) enables the user to obtain a more uniform temperature than found with traditional controllers.
Cycle duration and on off is set via a 99 hour timer located on the front panel. Temperature is monitored by a K Type thermocouple input to the temperature controller. Set point and over temperature alarm can be user defined.
 

SAFETY: To ensure vacuum integrity during bake out, the unit can accept trip input from most popular vacuum gauge controller relay outputs.
The unit can be supplied in either a 2U rack mount 19" box or a 2U freestanding box as required.

Technical Specification:

Mains input 110 or 220 VAC
Maximum Power Output 6 Kilo Watt
4 Heater outputs at 1.5KW each (MAX)
99 hr multiple set timer
Thermocouple feedback loop to digital temperature controller with multi set point capability
Vacuum interlock
2U box
Back panel : Mains cable, mains fuse, thermocouple i/p, vac interlock
Front panel : Mains on, power on, timer, controller , heater output x 4

Pricing

DescriptionOrder Code£ UK$ USEuro
ControllerBOC6C9951,8201,610
Slave unitBOC6SU6501,1891,020
ThermocoupleBOC6TC467984

 

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