When it comes to thin film deposition, various techniques and materials are available to the industry. A common choice for some industries is physical vapor deposition (PVD) using PVD materials. It is popular for producing reliable and suitable components for the electronic and optical industries. Exact application of this thin film coating involves one of several techniques. They include sputtering, ion plating and evaporation.
One of the most simple and common means of PVD is thermal evaporation. In essence, it involves the heating of the right materials in a vacuum chamber. They remain in this state until the surface atoms of the materials are energized enough to vacate the surface. They rise in something described best as a “particle cloud”.
This allows them to travel across the vacuum chamber until they reach the substrate material. They then coat it. The coating may be thin or thicker. The former is applicable to plastic coatings. Depending upon the thickness of the thin film coating, the result will be more decorative (thin) than protective (thicker). The distance between the substrate and the coating materials is crucial to the technique of applying PVD materials successfully as is the choice of heat source.
Heat Sources for Thermal Evaporation
Two principal means of heating the PVD material are:
- Filament Evaporation
- E Beam Evaporation
Each has its advantages and disadvantages yet both are simple and cost-effective sources of heat for the process.
This comes in many types or style including “boats.” A filament is an electrical resistive heat element. It works with low voltage but requires high current voltage to function as required.
E Beam Evaporation
Using an electron (e) beam as its heat source, this device is much higher tech than that of filament evaporation. It requires caution since the voltage is as high as 10,000 volts. For heating up PVD materials and completing the transfer to the substrate, an operator will use what is called an e-beam “gun.” For those who employ this method of evaporation, it is essential to pay extemely close attention to all safety measures.
PVD Materials and Thermal Evaporation
The choice of what technique a company will use to achieve the desired result will depend upon several factors including the substrate material, the purpose for the application of a thin film coating and, of course, the choice of the PVD material. Thermal evaporation, while no longer as popular as it has been in the past, still enjoys its proponents. They cite its simplicity as reasons for their choosing this method over others. In addition, using the right PVD materials as part of an environmentally friendly option, does make the technique more appealing.