1. High-frequency components and antennas: Ultrasonic vibration may damage the packaging of high-frequency components and antennas, resulting in performance degradation.
2. Varistor: Ultrasonic vibration may damage the pressure-sensitive material inside the varistor and reduce its efficacy.
3. Electrolytic capacitors: Electrolytic capacitors usually have liquid electrolyte, and the vibration of ultrasonic waves may lead to leakage or damage of the electrolyte.
4. Thermistors (PTC, NTC): Ultrasonic vibration may cause physical deformation of thermistors and affect their temperature sensing characteristics.
5. Fragile micro-components: Ultrasonic cleaning may cause physical damage to some fragile micro-components, such as small sensors and microswitches.
6. Some precision instruments and equipment: The vibration of ultrasonic wave may interfere with the positioning and calibration of some precision instruments and equipment.
In the manufacturing process of PCBA, if the above components are involved, ultrasonic cleaning should be avoided, and other suitable cleaning methods should be selected, such as spray cleaning, brushing and airflow purging. In order to ensure the safety and effectiveness of cleaning, it is suggested to choose an appropriate cleaning method according to the characteristics of components and the suggestions of manufacturers.