Square-resistance-gradient internal parallel metallized safety film

Abstract

The invention provides a square-resistance-gradient internal parallel metallized safety film, which comprises a base film (1); a clad layer thickening band (2) evaporated along the longitudinal centeraxis of an evaporation surface of the base film (1); electrode plate units (3) distributed symmetrically at the two sides of the clad layer thickening band (2), wherein the electrode plate units (3)are separated into the continuously distributed electrode plate units (3) by blank separation belts (4) in longitudinal continuous distribution; and blank margin bands (5) distributed symmetrically atthe other sides of the electrode plate units (3). The plating thickness of the electrode plate units (3) is in trapezium distribution transversely, is largest at the place adjacent to the clad layerthickening band (2), and is smallest at the place adjacent to the blank margin bands (5), and thus a square-resistance-gradient electrode structure is formed. The thin-film capacitor is good in self-healing performance, high in utilization rate of the electrode coating effective area and low in total equivalent series resistance of the metalized coating electrode, and can effectively reduce the size of the capacitor and reduce production cost.

Description

technical field [0001] The invention relates to a metallized thin film material for the production and manufacture of thin film capacitors, in particular to a parallel-connected metallized safety film with a gradual change in square resistance. Background technique [0002] Film capacitors are widely used because of their good pressure resistance and self-healing properties. Metallized films are important materials for the production of film capacitors. High-purity metals (such as Al, ZN) are melted, evaporated, and precipitated in a high vacuum state. On the dielectric base film, the film after forming a very thin metal coating on the surface of the dielectric base film is the metallized film; the resistance value of the unit square area of ​​the metal coating on the metallized film is called square resistance (ie square resistance, Expressed in Ω / □), this kind of capacitor made of metallized film has the same withstand voltage performance as the self-healing of the metal c...

AI Technical Summary

Problems solved by technology

[0002] Film capacitors are widely used because of their good pressure resistance and self-healing properties. Metallized films are important materials for the production of film capacitors. High-purity metals (such as Al, ZN) are melted, evaporated, and precipitated in a high vacuum state. On the dielectric base film, the film after forming a very thin metal coating on the surface of the dielectric base film is the metallized film; the resistance value of the unit square area of ​​the metal coating on the metallized film is called square resistance (ie square resistance, Expressed in Ω / □), this kind of capacitor made of metallized film has the same withstand voltage performance as the self-healing of the metal coating (that is, if there is an electric weak point in the dielectric base film, the breakdown discharge current will break the point The surrounding metal coating is ablated and evaporated, so that the electrical weakness is related to the ability of the overall capacitor plate to form an isolation state). The stronger the self-healing ability of the metal coating, the better the pressure resistance, and the self-healing ability of the metal coating is related to the thickness of the coating. Thin metal coating requires less energy for self-healing and is easy to self-heal, but because the thickness of the metal coating is thinner, its square resistance increases, its current carrying capacity decreases, and the capacitor is prone to heat and eventually fails; on the contrary, the thicker the metal coating, the square resistance Although the current carrying capacity is increased, the self-healing energy required by the metal coating is large, and self-healing is difficult. When there is a self-healing point (electrical weakness), the heat generated by the self-healing current will not be able to quickly self-heal. It will cause heat generation in the adjacent layer of the point, and the dielectric strength of the thin film dielectric will decrease, thereby causing electrical breakdown of the capacitor, which will easily lead to early failure of the capacitor; A metallized safety film, which separates the metallized coating evaporated on the base film into many small coating units with narrow gaps, and each small coating unit has a function of a fuse (fuse) The metal filaments are connected. If there is an electroweak point on the thin film of this structure, the breakdown discharge current will burn off the metal filaments connected to the small coating unit block where the point is located, so that the small coating at the electroweak point The unit is isolated from the overall capacitor electrode plate to form an insulating area to achieve self-healing, which can reduce the self-healing time of the film capacitor and reduce the damage to the medium. Although the overall capacitor loses the capacitance of the isolated small plating unit, it can continue Maintain normal operation, so that the capacitor can increase the working voltage and service life, and the effectiveness of using metallized safety film technology to improve the self-healing effect of the electric weak point of the film capacitor has been well known

However, there are disadvantages in the metallized safety film: 1. When breakdown and self-healing occur, although the area of ​​the isolated small coating unit is small, it is very different from the normal breakdown self-healing point coating area, so The capacity loss value is many times larger than the standard index value of ordinary metallized film capacitors, and there is a defect of low utilization rate of the effective area of ​​the electrode coating, which will inevitably increase the volume of the capacitor; 2. Many metal filaments under normal operation have relatively low square resistance The large current carrying capacity is small. When the capacitor is charging and discharging, the metal filaments become a heating point. Due to the huge number of metal filaments, the overall equivalent series resistance of the metallized plating electrode increases, and its heat generation will inevitably reduce the dielectric withstand voltage of the overall capacitor. , thereby reducing the dielectric working field strength of the overall capacitor. In order to increase the dielectric working field strength, it is usually achieved by increasing the thickness of the dielectric film, which will also increase the volume of the capacitor and increase the manufacturing cost of the capacitor.

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