What Makes a Hi-Rel Amplifier Hi-Rel?
The main application for High Reliability (Hi-Rel) RF/microwave amplifiers is for military, defense, aerospace, and other critical applications where device reliability is otherwise mission critical. In essence, a Hi-Rel Amplifier is just an amplifier that meets one or more military standards for reliability.
In order to ensure device and system reliability, the US military developed several military specifications (MIL-SPECs), or military standards (MIL-STDs), for manufacturers to adhere to. In the case of microelectronics, such as solid-state power amplifiers (SSPAs), the main standard is MIL-STD-883. This standard covers environmental, electrical, and mechanical performance requirements, as well as manufacturing criteria and test procedures.
Formerly, MIL-STD-883 was composed of a single part that addressed each aspect of microelectronic qualification, as of 2019, MIL-STD-883 is now 5 parts, environmental, mechanical, electrical (digital), electrical (linear), and test procedures. Additionally, each part is further divided into various test methods, which are numbered sequentially following the code for each part. For instance, the mechanical shock test method is designated 2002.5 from MIL-STD-883-2 and the Power gain and noise figure test method is designated 4006.2 in MIL-STD-883-4.
MIL-STD-883 Environmental (MIL-STD-883-1 as of 2019)
MIL-STD-883-1 covers the 34 environmental test methods for microelectronics, and includes barometric pressure, immersion, insulation resistance, temperature cycling, burn-in test, neutron irradiation, endurance life test, and more. In general, a given application will have certain aspects of environmental standards requirements and may require certain levels of performance beyond even the basic qualification of the standard. Moreover, this standard also covers accelerated test conditions, where the applied stress levels exceed the maximum operating ratings or storage stress levels of the devices, generally for a shorter amount of time. This allows for more time efficient qualification, as devices may undergo accelerated stress testing in a fraction of the time as typical testing would require.
MIL-STD-883 Mechanical (MIL-STD-883-2 as of 2019)
MIL-STD-883-2 is composed of 38 parts from mechanical shock, external visual, physical dimensions, SEM inspection of metallization, substrate attach strength, and resistance to soldering heat. Many aspects of this standard are to test the workmanship of the fabrication process for microelectronics, such as nondestructive bond pull and bond strength (destructive bond pull) testing.
MIL-STD-883 Electrical (MIL-STD-883-3 and MIL-STD-883-4 as of 2019)
MIL-STD-883-3 and 4 cover digital and linear electrical tests, specifically testing digital and analog/power/RF microelectronics. Hence, MIL-STD-883-3 covers aspects of digital devices, such as transistors, input/output voltage, delay, crosstalk, and static latch-up. Where MIL-STD-883-4 more specifically covers testing such as phase margin, slew rate, common mode rejection ratio , open loop performance, etc, which would commonly be applied to linear amplifiers.
MIL-STD-883 Test Procedures (MIL-STD-883-5 as of 2019)
Part of MIL-STD-883 touches on screening procedures, qualification and quality conformance procedures, and other methods of evaluation and analysis. This standard also includes wafer fabrication control and wafer acceptance procedures for gallium arsenide (GaAs) devices. Importantly, this is the standard that defines the procedures for custom monolithic microcircuits, which includes many monolithic microwave integrated circuit (MMIC) devices.
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