I. Ambient temperature
1. The high temperature
The highest working environment temperature around the capacitor is very important for its application. The rise of temperature accelerates all chemical and electrochemical reactions, and the dielectric material is easy to age. The service life of the capacitor decreases with the increase of temperature. The capacitance changes with the increase of temperature depends on the relationship between dielectric constant and temperature, with positive temperature coefficient that is, the capacity increases with temperature, with negative temperature coefficient capacity decreases with temperature.
As the temperature rises, the electrical activity increases, so the insulation resistance decreases with increasing temperature. The dielectric strength also decreases with the increase of temperature, so the operating voltage must be reduced when the upper service temperature is increased. High temperature makes metal oxidation, contact resistance increases, resistance increases and loss increases.
2. The low temperature
The material becomes brittle, the epoxy resin cracks and loses its protective effect. The electrical performance of the capacitor is degraded by moisture infiltration.
3. High and low temperature impact
Rapid thermal expansion and contraction produce internal stress, produce alternating condensation, freezing and evaporation, so that the encapsulation layer cracking, cracking lead to water vapor infiltration, accelerate the performance of the capacitor deteriorates.
II. Humid environment
1. The high humidity
Water vapor condenses on the surface of the capacitor, and is absorbed, so that the insulation resistance of the capacitor decreases, and there is leakage and arc flying. The dielectric constant increases and the dielectric loss increases. When water vapor enters the inner metallized layer of the capacitor, the capacity will decrease and the loss will increase.
2. Alternating hot and humid
The water vapor is absorbed and diffused on the surface of the capacitor. Respiration and condensation of heating can accelerate the water vapor to penetrate into the inside of the capacitor and make the performance of the capacitor deteriorate as mentioned above.
At the same relative humidity, when the temperature rises, the number of water molecules increases and the formation of molecular gaps is accelerated. Water molecules can enter these gaps from the surrounding air and thus penetrate into the medium.
At the same absolute humidity, the lower the temperature, the higher the relative humidity, the more moisture the capacitor absorbs.
III. Dynamic environment
Vibration, impact and acceleration are the main dynamic environment, which can cause the capacitor to be damaged or damaged by the SMT machine and other machinery, and the capacitance changes due to the small change of capacitor structure. In addition, it may cause lead breakage, bad contact and other phenomena.
IV. Low pressure environment
Capacitors are used in high-altitude environments. With the increase of altitude, the air pressure decreases and the electrical resistance of the air decreases. The capacitor will produce arc and corona phenomenon, and the voltage strength of the capacitor will decrease. In addition, the thin air is difficult to heat. The temperature rise of the capacitor will increase.
Zhejiang NeoDen Technology Co., LTD., founded in 2010, is a professional manufacturer specialized in SMT pick and place machine, reflow oven, stencil printing machine, SMT production line and other SMT Products. We have our own R & D team and own factory, taking advantage of our own rich experienced R&D, well trained production, won great reputation from the world wide customers.We believe that great people and partners make NeoDen a great company and that our commitment to Innovation, Diversity and Sustainability ensures that SMT automation is accessible to every hobbyist on everywhere.
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Phone: +86-18167133317
Post time: Sep-28-2021