Sub-GHz Transceiver Crystal Passivation under Extended High Current Transmit Pulses
Sub-GHz transceiver crystal passivation prevents drive-level dependency shifts and frequency pulling during extended high-current power amplifier transmit pulses.
Structural Outgassing
Meaning
Spontaneous release of vapor or gas that was previously trapped or absorbed within a solid material. In the production of sealed electronic enclosures, structural outgassing can lead to the buildup of pressure or the contamination of sensitive optical and radio components. This process is most common in plastics, adhesives and coatings that contain volatile organic compounds or moisture from the manufacturing environment.
Contamination Risk
Released molecules can settle on the surfaces of lenses, sensors or high frequency antennas and degrade their performance. Structural outgassing in a camera module might cause a thin film to form on the lens, resulting in blurry images or loss of light sensitivity. In high power radio systems, these gases can alter the dielectric properties of the air inside the enclosure and lead to electrical arcing.
Selecting low-outgassing materials is the primary way to prevent these issues in sensitive hardware.
Vacuum Exposure
Rate of gas release increases at a higher rate when the material is placed in a low pressure environment. For aerospace and satellite electronics, structural outgassing is a major concern because the vacuum of space pulls gases out of the materials at a high rate. This can cause the mechanical properties of the plastic to change or lead to the failure of nearby components.
Testing in a thermal vacuum chamber is used to measure the total mass loss and the collected volatile condensable material of a part.
Pre-Baking Process
Heating the components in a controlled environment before final assembly can drive out most of the volatile substances. This thermal treatment reduces the potential for structural outgassing once the device is in the field. The duration and temperature of the bake are determined by the thickness of the material and the specific types of chemicals it contains.
This step is a standard part of the quality control process for high reliability electronics used in medical or military applications.