Thick film heaters have emerged as a versatile and efficient solution for a myriad of applications. These remarkable heating elements have been designed with a unique manufacturing process that not only offers exceptional heating capabilities but also provides the flexibility required for a range of industries.
Those heaters are renowned for their ability to achieve rapid temperature rise, low thermal capacity, and minimal temperature fluctuations. The fabrication process ensures a high degree of precision and control over the heater's resistance, wattage, watt density, and uniformity, making them ideal for a wide range of applications.
The fabrication of thick film heaters is a multi-step process that combines advanced technology and craftsmanship. The steps involved are as follows:
1. Substrate Cutting: Depending on the desired shape and dimensions, the substrate is cut using laser or a diamond saw. The cutting process adheres to the engineering drawing of the heater's shape.
2. Dielectric or Insulation Layer: An emulsion of dielectric material is prepared and applied to the substrate. In cases where the substrate is non-metallic, surface activation treatment may be necessary to enhance bonding.
3. Ink Development or Formulation: Paste or ink for resistive traces is prepared by mixing metal or metal oxides with a solvent. The mixing process must achieve a high degree of homogeneity to eliminate hot spots and burnout in the final product.
4. Stencil or Mask Fabrication for Screen Printing: Stencils are created to determine the arrangement of heating traces. By using a squeegee, paste or ink is forced through these stencils onto the substrate, creating heating traces. The stencil design influences the pattern of heat distribution.
5. Printing: The resistive and conductor traces are printed onto the substrate using screen printing technology. This technology is cost-effective and widely used for thick film heaters.
6. Curing or Firing: In this crucial step, the printed heater undergoes heat treatment to strengthen the bonds between layers. The firing process also forms a network of electrically conductive pathways, creating the permanent heating elements. Glass particles are melted to bond the entire structure while maintaining a degree of flexibility.
7. Protective Layer: A protective dielectric layer is applied over the heating traces, insulating them.
8. Electric Termination: Various metals and alloys, such as silver, platinum, gold, and their alloys, can be used for electric termination, which is essential for connecting the heater to the power source.
Traditional far-infrared lamp heating, which primarily relies on radiation for heat transfer, is highly efficient. However, in cases where the paste layer is relatively thick, a significant temperature difference between the inside and outside of the paste layer over a short period can lead to cracking.
Solution:
Depending on the thickness of the paste layer, our furnace offers two heating methods: far-infrared lamp heating or ceramic fiber heating board.
Pursuing higher production capacity, coupled with the use of stainless steel tube substrates with greater heights, results in a wider belt and higher effective furnace height. Achieving uniform temperature within the furnace space becomes challenging.
Solution:
Our furnace has temperature uniformity of ±1.5°C -> ±3°C, up to belt width of 36 inches (915mm) and effective furnace height of 10 inches (254mm).
Apart from factors related to the paste and furnace temperature uniformity, the furnace's exhaust capacity is crucial for proper curing.
Solution:
Effective solutions include well-designed airflow, robust exhaust capacity, and ensuring there are no dead spots in the drying section of the furnace, along with anti-drip design in the exhaust.
Learn more about our belt furnaces (Thick Film, GTMS, LTCC and more) and Screen Printing line!