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.
Helium Leak Testing
Meaning
Leak detection procedures using helium as a tracer gas measure the hermeticity of sealed semiconductor and quartz crystal packages to ensure long-term reliability. This process, known as helium leak testing, is performed on components that must operate in harsh environments or maintain a vacuum. The test chamber is evacuated after the component is pressurized with helium, and a mass spectrometer measures the leakage rate.
If the leakage rate exceeds the specified threshold, the component is rejected.
Pressurization Stage
Hermetically sealed devices are placed in a pressurized helium chamber for a set period, a process called bombing. If there are any leaks in the package seal, the helium gas enters the internal cavity. The pressure and duration of the bombing stage are determined by the internal volume of the component.
Mass Spectrometry
The bomb-exposed components are transferred to a vacuum chamber connected to a helium mass spectrometer. The spectrometer detects and quantifies any helium atoms escaping from the package. This method can resolve fine leaks down to extremely low flow rates.
Coarse Leak
Helium testing is primarily used for fine leaks because the gas can escape too quickly from large holes during the vacuum stage. A separate coarse leak test, such as liquid immersion, is used to identify larger defects. This two-stage testing process ensures that all package defects are detected.