The formation and implosion of microscopic bubbles during ultrasonic cleaning provides a scrubbing action that assists the cleaning process. Unfortunately, the ultrasonic cleaning process also subjects the components being cleaned to high frequency, high energy vibrations. In the case of ultraminiature electromechanical relays, ultrasonic cleaning of an assembly or circuit board containing relays subjects the relays, and therefore the relay contacts, armature, and other mechanical components, to ultrasonic vibrations. Excessive ultrasonic cleaning can cause premature contact wear or contact sticking, and damage to the armature or the coil. Relay contacts that have been subjected to excessive ultrasonic vibrations may develop deep grooves or other wear patterns that are inconsistent with typical relay operation. This may result in relay failures during the assembly process, or reduced reliability and inconsistent performance in the field. This paper presents a brief introduction to ultrasonic cleaning, and then demonstrates through a case study that severe damage can result from ultrasonic cleaning. Using ultrasonics to clean circuit board assemblies containing ultraminiature electromechanical relays is not a recommended practice.
展开▼
