Comparing Resistive vs. IR Heaters for Liquid Heating

The ability to heat a process tank, keep the temperature controlled, and do no damage to the heating element has, like other processes in semiconductor manufacturing, improved over time. With the increased emphasis on throughput and uptime, fabs are hesitant to schedule repetitive preventative maintenance of such items as process tank inline heaters. Other equipment applications in billion dollar fabs are more worthy of maintenance time and talent.

The infrared (IR) heater – often called radiant heating – was the standard in the semi industry for many years. Reflectors to generate increased temperature typically surrounded a quartz heating lamp.

Infrared IR Heater Lamp for Liquid Heating

IR (Infrared) Heating Problems:

  • Works well for heating H2O but has limitations for other liquids a large amount of input energy is wasted in the visual spectrum.
  • IR lamps don’t last long; usually PMs are scheduled every 6-12 months.
  • It’s not easy to capture the radiant heat; often the lamp sockets and other internal components fail prematurely.
  • A “cooling” system is sometimes used to address component failure.
  • IR heating is typically flow-dependent; if there is no liquid flow, safety concerns arise.
Resistive Heater Element for Liquid Heating

Resistive Heating Advantages:

  • No maintenance: there are no seals, lamps or cooling purges needed.
  • Non-flow dependent meaning that no flow sensing device is required to meet Semi S3 requirements.
  • Heater elements are in direct contact with the outer quartz surface making heat transfer efficient.
  • Conductive heat is better absorbed by chemicals such as sulfuric, nitric, and phosphoric acids.
  • Resistive heater elements can be monitored to provide maximum heat transfer at varying flow rates and conditions.
  • Low external housing surface temperatures result, usually no higher than 50° C

In many cases, IR heaters can be replaced by Resistive heaters in existing equipment without making major modifications. By utilizing special sensors and other components Imtec can mimic the functionality of the old heater to eliminate the need for modifications to the control system. In some cases, special mounting brackets or plumbing connections can be used to simplify installation.