Purpose of PIND testing
Purpose of Particle Impact Noise Detection testing (PIND)
All modern systems for military, space and satellite applications use many electronic components that perform complex control, navigational and monitoring functions of the systems Proper functioning of these devices without interruptions is vital to the success of the missions and safety of the personnel and equipment. Towards achieving this objective, electronic components are manufactured and tested in accordance with the controls and requirements of applicable military standards, specifications and drawings. One critical factor that can cause catastrophic device failure is loose particles within the components.
The focus and importance of screening devices for particles occurred when a catastrophic system failure in the Delta Launch Vehicle Program was traced to a loose bit of wire within an electronic component. The significance of screening devices for particles was further elevated because of advances in the manned space vehicle, satellite and missile programs. As a result, space-level devices (Class S) and Class B devices that are used in flight and missile applications must be particle-tree.
The PIND Test is designed to detect small contaminants inside of those electronic packages that contain a cavity.
These particles could move in a dynamic environment and locate into a position, typical the bond wires, which could short out the part for a brief time during usage. Such a failure is critical for high dynamic stress environments.
The PIND test is somewhat unique in that the particles themselves are never measured directly. Only a very sensitive acoustic detector measures the effects of moving particles as they impact the inside of the cavity.
When these particles in motion contact the lid of the cavity part of their kinetic energy is transferred to acoustic energy in the form of a longitudinal particle wave, which propagates through the cavity lid to the ultrasonic detector below. The ultrasonic detector contains a very sensitive piezoelectric crystal, which converts the acoustic wave into electrical energy. The electrical output of the sensor is amplified and filtered, then displayed on a monitor scope, converted to a low frequency audio signal for audio interpretation, and finally compared to a threshold to provide an impartial indicator of signal.
There are three basic direct measurements, which result in the PIND TEST system measurement:
- 1. DETECTION
- 2. VIBRATION
- 3. SHOCK