HEM Sealed Heater™ - Bench Test to 250°C

In addition to optimizing liquid flow in space launches, more research and design facilities require a heater that will work in vacuum without outgassing the internal resistor and insulating materials.  Materials such as chromium and particles from the magnesium oxide begin to outgas.  Placing a vacuum barrier that keeps these particles in place and allows the operator to process without consistently replacing heaters, should increase productivity.

HEM Sealed Heater™/ Vacuum Chambers:

• Temperature range of -55⁰C to +200⁰C Sheath Temperatures
• Stainless steel 321 for heated zone, 304 Hem Sealed Cap   
• 18AWG to 32AWG Kapton®/polyimide Lead wires 
• 500Watt (± 10%) , 240 Volt, 1-phase   
• He Leak Tested = 5 x 10¯⁹ ATM, CC/sec or better 
• Hi-Pot Test 1K*2E 1 2 seconds (1500-2250VDC 0.5mA) 
• Meg-Ohm 20 to 4,000+ @ 500VDC 

OUTCOME:

This test was performed in atmosphere within a 3.5 hour time frame.  The temperature was held each hour after the initial ramp to sheath temperature as noted in the graph below.

The temperature of 200°C was held for the 2nd hour and then the heater was powered ~250°C and held until the test was complete after about 3.5 hours.  

At lower temperatures of ~200°C, the Hem Sealed™ Cap reached 60°C keeping the vacuum integrity as per the maximum heater transition temp of 70°C.  The maximum temperature on the sheath tested was to 250°C with the Hem Sealed™ Cap at 79°C.

Special note; if a heater block or other device being heated, the optimal bore diameter vs heater diameter for the best heat transfer should be +.0020” to +.0025”.

Drawing and more information here.

BCE

https://bcemfg.com

+1 510-274-1990

BCE’s Vacuum Ring Heater: Defying Boundaries in Degassing Chambers

BCE Vacuum Ring Heater

Providing uniform heat to semiconductor devices in degassing chambers is essential in extracting impurities. This can only be achieved if a heating device has the proper fit and temperature uniformity for a given chamber. It is for this very application that BCE was approached by a large semiconductor company from Silicon Valley. In order to heat this company’s semiconductor wafers, it was critical that the heating device be manufactured to fit precisely into a large and circular degassing chamber posing manufacturing challenges due to dimensional and application parameters. BCE was able to provide extensive design consultations, 3D CAD modeling and lean manufacturing capabilities to this semiconductor giant at a competitive price. All these services were rendered while catering to all requirements needed to successfully manufacture their products.

SCOPE

The heating apparatus needed to satisfy the following criteria:

• Vacuum compatibility to 10^-8 Torr 
• Maximum Operating Temperature: 200°C 
• Temperature uniformity of ±4% at 150°C 
• Operate at 1500W, 240V 
• All epoxies used needed to meet NASA’s Low Outgassing Spec (ASTM E595) 
• Reduced contamination from components inside chamber 
• Temperature sensing capability 
• Circular configuration between 34 and 36 inches in diameter 
• Height of part was not to exceed 1 ft. 
• Effective heat transfer from heating device with reduced machining cost 

OUTCOME

BCE’s Vacuum Ring Heater proved to be the ideal product for this application. Its strong aluminum ring construction ensured effective heat transfer to the circular wafers while keeping manufacturing costs low. Furthermore, its strategically embedded heater with stainless steel sheath allowed the device’s temperature uniformity to remain at ±2% at 150°C, greatly exceeding customer requirements. Moreover, BCE’s proprietary epoxy meeting NASA’s low outgassing spec was used as the primary sealant and KAPTON insulated leads were provided for the heater and integrated thermocouple to reduce contamination. In fact, the integrated thermocouple type K further served to monitor the temperature supplied to the chamber. Finally, all electrical, vacuum and dimensional requirements were met to provide the most optimal thermal environment.

Visit this link for more information on the Vacuum Ring Heater, or call (510) 274-1990.