Composite metal thin film, method of making the same, and metallized film capacitor comprising the same

Abstract

The application discloses a composite metal film, a preparation method thereof and a metallized film capacitor comprising the same. The preparation method of the composite metal film comprises the following steps: forming a gradient sheet resistance layer on a base film by an evaporation method, and forming a reserved edge on the base film; then forming a filling layer on the gradient sheet resistance layer by the evaporation method, so that the outer surface of the filling layer is parallel to the surface of the base film, to obtain the composite metal film; wherein the thickness of the gradient sheet resistance layer gradually increases in the direction from the reserved edge end to the gold spraying end, and the thickness of the filling layer gradually decreases. The composite metal film prepared by the application has a smooth plating layer, greatly reduces the interlayer air gap, that is, greatly reduces the occurrence of interlayer air gap ionization, and also reduces the problem of capacity attenuation caused by the peeling of the plating layer due to air gap ionization; meanwhile, the overcurrent capacity and self-healing performance are improved.

Description

Technical Field

[0001] This invention relates to the field of metallization film technology, specifically to composite metal thin films, methods for their preparation, and metallization film capacitors containing the same. Background Technology

[0002] Among the three major passive components, capacitors are the most widely used, and their main characteristic is "blocking DC and passing AC". Their basic structure consists of two metal plates with an insulating dielectric in between. Metallized film capacitors are widely used due to their non-polarity and self-healing properties.

[0003] Metallized film capacitors are made by depositing a metal coating (on the order of nanometers) onto a plastic film. The plastic film acts as the dielectric (on the order of micrometers), and the metal coating on the film acts as the electrode for storing charge. Two metallized films are wound together to form the core of the capacitor. Gold is then sputtered onto both ends of the core to bring out two electrodes, thus forming a basic metallized film capacitor.

[0004] Existing graded sheet resistance metallization films, such as Figure 8 As shown, its gradient sheet resistance structure solves the shortcomings of weak overcurrent capability in the high sheet resistance region and easy breakdown in the low sheet resistance region due to weak self-healing. However, since there are different sheet resistances on the same plate, even with the same plating material, there will inevitably be differences in the thickness of the metal plating, resulting in unevenness of the plate. Therefore, when two metallized films are stacked, there will inevitably be a certain air gap between the layers. Under an applied electric field, the air gap between the layers is prone to ionization, which generates heat. The accumulation of heat damages the molecular structure of the thin film dielectric, reducing its performance. Therefore, excessive air gap ionization will eventually lead to the breakdown of the thin film dielectric, causing the capacitor to fail. At the same time, the occurrence of air gap ionization will also cause the metal plating in the area where the air gap is located to peel off, resulting in a decrease in capacitance and accelerating the failure of the capacitor. Summary of the Invention

[0005] The purpose of this invention is to overcome the problem of interlayer air gap ionization under an applied electric field in existing technologies, and to provide a composite metal thin film, a method for preparing the same, and a metallized film capacitor containing the same. This composite metal thin film avoids the problem of interlayer air gap ionization under an applied electric field, thus improving the voltage withstand level of the capacitor; simultaneously, its gradient sheet resistance structure enhances overcurrent capability and self-healing properties.

[0006] To achieve the above objectives, the first aspect of the present invention provides a method for preparing a composite metal thin film, the method comprising the following steps:

[0007] The gradient square resistance layer is formed on the base film by an evaporation method, and a reserved edge is formed on the base film; then the filling layer is formed on the gradient square resistance layer by an evaporation method, so that the outer surface of the filling layer is parallel to the surface of the base film, and the composite metal film is obtained; wherein, in the direction from the reserved edge end to the gold spraying end, the thickness of the gradient square resistance layer gradually increases, and the thickness of the filling layer gradually decreases.

[0008] Further, the longitudinal section structure of the base film is rectangular; and / or, the longitudinal section structure of the gradient square resistance layer is trapezoidal or triangular; and / or, the longitudinal section structure of the filling layer is trapezoidal or triangular.

[0009] Further, the material of the gradient square resistance layer is silver, aluminum, copper or gold.

[0010] Further, before the gradient square resistance layer is formed on the base film, the preparation method further comprises:

[0011] The substrate layer is formed on the base film by an evaporation method, and a reserved edge is formed on the base film; then the gradient square resistance layer is formed on the substrate layer; wherein, in the direction from the reserved edge end to the gold spraying end, the thickness of the substrate layer gradually increases.

[0012] Further, the material of the base film is polypropylene or polyester; and / or, the material of the filling layer is zinc, tin, tungsten or platinum.

[0013] Further, the resistivity of the material of the gradient square resistance layer is a, the resistivity of the material of the filling layer is b, and a and b satisfy the relationship: b>a.

[0014] Further, a and b satisfy the relationship: b>2a.

[0015] Further, after the filling layer is formed, the preparation method further comprises:

[0016] The protective layer is formed on the filling layer by an evaporation method; wherein, the longitudinal section structure of the protective layer is rectangular.

[0017] Further, after the protective layer is formed on the filling layer, the preparation method further comprises:

[0018] The oxidation-resistant oil layer is formed on the outer surface of the protective layer by a coating method.

[0019] Further, the material of the oxidation-resistant oil layer is one or more of silicone oil, epoxy soybean oil, palm oil, castor oil and paraffin oil.

[0020] The second aspect of the present application provides a composite metal film prepared by the aforementioned preparation method.

[0021] The third aspect of the present application provides a metallized film capacitor, which comprises the aforementioned composite metal film.

[0022] By the technical scheme, the application has the following beneficial technical effects:

[0023] The application forms a gradient sheet resistance layer and a filling layer on the base film by the evaporation method, forms a composite metal film with a smooth plating layer, fully overlaps the two smooth films, greatly reduces the interlayer air gap, greatly reduces the occurrence of interlayer air gap ionization, and reduces the problem of capacity attenuation caused by the peeling of the plating layer due to air gap ionization; meanwhile, the gradient sheet resistance of the plating layer is adapted to the distribution of the current on the plate (i.e., the plating layer), enhances the current-carrying capacity and voltage resistance, improves the overcurrent capacity and self-healing performance. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 The preparation flowchart of the composite metal film of one embodiment of the application;

[0025] Figure 2 The structure schematic diagram of the composite metal film of one embodiment of the application;

[0026] Figure 3 The structure schematic diagram of the composite metal film of another embodiment of the application;

[0027] Figure 4 The structure schematic diagram of the composite metal film of another embodiment of the application;

[0028] Figure 5 The structure schematic diagram of the composite metal film of another embodiment of the application;

[0029] Figure 6 The structure schematic diagram of the composite metal film of another embodiment of the application;

[0030] Figure 7 The longitudinal section structure schematic diagram of the gradient sheet resistance metalized film of Comparative Example 1 of the application;

[0031] Figure 8 The longitudinal section structure schematic diagram of the gradient sheet resistance metalized film of Comparative Example 2 of the application.

[0032] REFERENCE SIGNS

[0033] 1: composite metal film; 11: base film; 12: gradient sheet resistance layer; 13: filling layer;

[0034] 14: substrate layer; 15: protective layer; 111: first region; 112: second region;

[0035] 1A: edge remaining end; 1B: gold spraying end. DETAILED DESCRIPTION

[0036] The endpoints of the ranges and any values disclosed herein are not limited to the precise values recited as the exact dimensions are not critical to the invention. Any numeric range recited is intended to include all values from the lower value to the upper value, inclusive of both values, and to also include any value approximately or roughly between the lower value and the upper value. Numeric ranges can be expressed as including another numeric value when that other numeric value is within the range.

[0037] The first aspect of the present application provides a preparation method of a composite metal film 1, as shown in Figure 2 and Figure 3 The preparation method comprises the following steps:

[0038] The gradient sheet resistance layer 12 is formed on the base film 11 by a vapor deposition method, and a reserved edge is formed on the base film 11; the filling layer 13 is formed on the gradient sheet resistance layer 12 by a vapor deposition method, so that the outer surface of the filling layer 13 is parallel to the surface of the base film 11, to obtain the composite metal film 1; wherein the thickness of the gradient sheet resistance layer 12 gradually increases in the direction from the reserved edge end 1A to the spraying gold end 1B, and the thickness of the filling layer 13 gradually decreases.

[0039] In the present application, the gradient sheet resistance layer 12 is formed on the first area 111 of the base film 11 by a vapor deposition method, and the reserved edge is formed on the second area 112 of the base film 11.

[0040] In the present application, the outer surface of the filling layer 13 refers to the surface of the side of the filling layer 13 away from the base film 11, as shown in Figure 2 which is the upper surface of the filling layer 13.

[0041] In the present application, the gradient sheet resistance layer 12 and the filling layer 13 are sequentially stacked on the upper surface of the base film 11, the two ends of the gradient sheet resistance layer 12 and the filling layer 13 are aligned, and the lengths of the adjacent edges of any two adjacent layers are equal and combined with each other.

[0042] In the present application, the gradient sheet resistance layer and the filling layer are sequentially formed on the base film by a vapor deposition method to form a composite metal film with a flat plating layer, so that the two flat films are fully overlapped, the interlayer air gap is greatly reduced, the occurrence of interlayer air gap ionization is greatly reduced, and the problem of capacity attenuation caused by plating layer falling off due to air gap ionization is also reduced; at the same time, the gradient sheet resistance of the plating layer is adapted to the distribution of current on the electrode plate (i.e. the plating layer), the overcurrent capacity and the voltage resistance are enhanced, and the overcurrent capacity and the self-healing performance are improved.

[0043] In some embodiments of the present application, the longitudinal cross-sectional structure of the base film 11 is rectangular, preferably square or rectangular.

[0044] In the present application, the longitudinal cross-section refers to the cross-section obtained by cutting perpendicular to the base film 11 along the length direction of the base film 11.

[0045] In some embodiments of the present application, the longitudinal cross-sectional structure of the gradual square resistance layer 12 is a trapezoid or a triangle, preferably a right-angled trapezoid.

[0046] In the present application, the thickness of the gradual square resistance layer 12 gradually increases from right to left, so that the square resistance value of the layer gradually decreases from right to left. The cross-sectional structure of the layer is not limited to a "trapezoid", but can also be a "triangle". As shown in Figure 2 , the longitudinal cross-sectional structure of the gradual square resistance layer 12 is a right-angled triangle, and as shown in Figure 3 , the longitudinal cross-sectional structure of the gradual square resistance layer 12 is a right-angled trapezoid. The gradual square resistance layer 12 of the present application is made of a material with low resistivity (e.g. aluminum), which plays a dominant role in the square resistance of the entire electrode composed of multiple layers of metal in parallel.

[0047] In some embodiments of the present application, the longitudinal cross-sectional structure of the filling layer 13 is a trapezoid or a triangle, preferably a right-angled trapezoid.

[0048] In the present application, as shown in Figure 2 , the thickness of the filling layer 13 gradually increases from left to right, so that the square resistance value of the layer gradually decreases from left to right. The cross-sectional structure of the layer is not limited to a "trapezoid", but can also be a "triangle". The filling layer 13 of the present application is made of a material with relatively high resistivity (e.g. zinc), and the main role of the layer is to fill the electrode plate, so that the entire composite metal electrode plate finally becomes a flat electrode plate.

[0049] In some embodiments of the present application, the material of the gradual square resistance layer 12 is silver, aluminum, copper or gold.

[0050] In some embodiments of the present application, as shown in Figure 4 and Figure 5 , a substrate layer 14 is formed on the base film 11 by a vapor deposition method, and a reserved edge is formed on the base film 11; then the gradual square resistance layer 12 is formed on the substrate layer 14; wherein the thickness of the substrate layer 14 gradually increases from the reserved edge end 1A to the gold spraying end 1B.

[0051] In the present application, when the material of the gradual square resistance layer 12 is aluminum or copper, in order to improve the adhesion of the reinforced metal plating layer to the base film, a substrate layer 14 is formed on the base film 11 by a vapor deposition method before the gradual square resistance layer 12 is formed on the base film 11, and then the gradual square resistance layer 12 is formed on the substrate layer 14. When the material of the gradual square resistance layer 12 is silver, a substrate layer 14 can not be provided between the base film 11 and the gradual square resistance layer 12. This is because when the substrate layer 14 is silver, the material of the gradual square resistance layer 12 is the same as that of the substrate layer 14, and there is no need to separately provide a substrate layer 14 which still has good anti-oxidation and corrosion resistance.

[0052] In some embodiments of the present application, the material of the substrate layer 14 is silver or gold.

[0053] In some embodiments of the present application, the longitudinal cross-sectional structure of the substrate layer 14 is a triangle or a trapezoid, preferably a right triangle.

[0054] In the present application, as shown in Figure 4 and Figure 5 , the thickness of the substrate layer 14 gradually increases from right to left (progressively), so that the sheet resistance of the substrate layer 14 gradually decreases from right to left. The longitudinal cross-sectional structure of the silver plating layer is not limited to a "triangle", but can also be a "trapezoid". As shown in Figure 4 , the longitudinal cross-sectional structure of the substrate layer 14 is a right triangle, and as shown in Figure 5 , the longitudinal cross-sectional structure of the substrate layer 14 is a right trapezoid. The substrate layer 14 of the present application is used as a conductive substrate layer on the base film, in order to enhance the adhesion of the metal plating layer to the base film and reduce the risk of the plating layer falling off (which can cause harmful problems such as a decrease in the capacity of the capacitor). At the same time, when silver metal is used as the substrate layer 14, its activity is low, and it can also enhance the anti-oxidation corrosion ability of the entire composite metal thin film.

[0055] In some embodiments of the present application, the material of the base film 11 is plastic, preferably polypropylene or polyester.

[0056] In some embodiments of the present application, the material of the filling layer 13 is zinc, tin, tungsten or platinum.

[0057] In some embodiments of the present application, the resistivity of the material of the gradual sheet resistance layer 12 is a, and the resistivity of the material of the filling layer 13 is b, and a and b satisfy the relationship: b > a.

[0058] In some preferred embodiments of the present application, a and b satisfy the relationship: b > 2a.

[0059] In some embodiments of the present application, after the filling layer 13 is formed, as shown in Figure 5 and Figure 6 , after the protective layer 13 is formed on the gradual sheet resistance layer 12, the aforementioned preparation method further comprises:

[0060] forming a protective layer 15 on the filling layer 13 by evaporation; wherein the longitudinal cross-sectional structure of the protective layer 15 is a rectangle, preferably a square or a rectangle.

[0061] In the present application, from the reserved edge end 1A to the gold spraying end 1B, the thickness of the substrate layer 14 is constant.

[0062] In some preferred embodiments of the present application, the material of the protective layer 15 is selected from aluminum.

[0063] In the present application, as shown in Figure 5 and Figure 6As shown, the protective layer 15 is the outermost layer, the longitudinal section structure of which is "rectangular", the thickness of which is uniform, and the sheet resistance of which is consistent. The main function of this layer is to isolate air and avoid air oxidation of the filling layer 13, i.e. to protect the metal coating from oxidation. This is because the metal (e.g. aluminum) of the protective layer 15 is easy to form a very thin oxide layer when in contact with air, which can effectively prevent further oxidation inside.

[0064] The present application has a structure of multiple metal composites, which forms a flat capacitor plate on the base film. Thus, the problem of uneven thickness of the existing metalized thin film coating (i.e. the capacitor plate) is solved, and the sheet resistance is gradually changed. The purposes of enhancing the current-carrying capacity and the voltage resistance of the capacitor are achieved. Meanwhile, the anti-oxidation and corrosion resistance of the composite metal thin film is improved.

[0065] In some embodiments of the present application, after the protective layer 15 is formed on the filling layer 13, the aforementioned preparation method further comprises: forming an anti-oxidation oil layer on the outer surface of the protective layer 15 by coating.

[0066] The outer surface of the aluminum coating is coated with a certain thickness of anti-oxidation oil, and the longitudinal section structure of the anti-oxidation oil layer is rectangular, preferably rectangular or square. The anti-oxidation oil is used to isolate the metal coating from the contact with the external air, so as to avoid the oxidation of the metal coating by the oxygen in the air. When the metal coating encounters moisture or water, the anti-oxidation oil protects the coating from corrosion.

[0067] The present application does not have special requirements for the thickness of the anti-oxidation oil layer, and preferably, the thickness of the anti-oxidation oil layer is much smaller than the thickness of the base film.

[0068] In some preferred embodiments of the present application, the material of the anti-oxidation oil layer is selected from one or more of silicone oil, epoxy soybean oil, palm oil, castor oil and paraffin oil.

[0069] The present application uses a plastic base film as the medium of the capacitor, which has the advantages of high voltage resistance, good insulation, small loss, no polarity, etc. The thickness of the base film 11 is usually 2-20 μm; the specific sheet resistance of the substrate layer 14, the gradually changing sheet resistance layer 12, the filling layer 13 and the protective layer 15 needs to be calculated according to the target sheet resistance. The thickness of each coating layer is determined by the target sheet resistance value.

[0070] In the present application, the substrate layer 14 acts as a gasket, and from the aspects of cost, etc., the thickness of the substrate layer 14 should not be too thick. The gradually changing sheet resistance layer 12 determines the overall sheet resistance. The filling layer 13 fills the space (makes the plate change from "inclined" to "flat"), and the larger the sheet resistance, the better, i.e. the thinner, the better. The protective layer 15 protects, and the larger the sheet resistance, the better, i.e. the thinner, the better. The thickness of the protective layer 15 and the thickness of the anti-oxidation oil layer are both much smaller than the thickness of the base film 11.

[0071] In the present application, the evaporation is carried out in a closed space with humidity less than 50%. The evaporation method of the present application adopts the conventional evaporation method in the art, which is not described herein.

[0072] By adopting the way of multi-metal composite evaporation, the multi-metals are finally jointly accumulated to form a flat, square resistance gradually changing, and non-oxidation corrosion capacitor plate. The interlayer air gap ionization problem caused by the uneven thickness of the plate is solved, the overcurrent capacity and self-healing performance are improved, and the oxidation corrosion problem is also solved. Finally, the purposes of enhancing the overcurrent capacity and self-healing capacity of the capacitor, and enhancing the withstand voltage capacity of the capacitor are achieved, and the anti-oxidation corrosion capacity is also enhanced.

[0073] As a preferred embodiment of the present application, the present application provides a preparation method of a composite metal film 1, as shown in Figure 1 and Figure 5 , specifically comprising the following steps:

[0074] S1, forming a substrate layer 14 on the base film 11 by evaporation method, and forming a reserved edge on the base film 11;

[0075] S2, forming a gradually changing square resistance layer 12 on the substrate layer 14 by evaporation method;

[0076] S3, forming a filling layer 13 on the gradually changing square resistance layer 12 by evaporation method, so that the outer surface of the filling layer 13 is parallel to the surface of the base film 11;

[0077] S4, forming a protective layer 15 on the filling layer 13 by evaporation method;

[0078] S5, forming an anti-oxidation oil layer (not shown in the figure) on the outer surface of the protective layer 15 by coating method. Figure 5

[0079] The second aspect of the present application provides a composite metal film prepared by the above preparation method.

[0080] In some embodiments of the present application, as shown in Figure 2 and Figure 3 , the composite metal film comprises: a base film 11, and a gradually changing square resistance layer 12 and a filling layer 13 sequentially stacked on the base film 11, and having a reserved edge at one end of the base film 11; wherein, from the reserved edge end 1A to the gold spraying end 1B, the thickness of the gradually changing square resistance layer 12 gradually increases, and the thickness of the filling layer 13 gradually decreases.

[0081] In some embodiments of the present application, as shown in Figure 4 and Figure 5 ​As shown, a substrate layer 14 is further arranged between the base film 11 and the gradually changing square resistance layer 12.

[0082] In some embodiments of the present application, as shown, a protective layer 15 is further arranged on the filling layer 13; preferably, an anti-oxidation oil layer is further arranged on the outer surface of the protective layer 15. Figure 5

[0083] The present application forms a composite metal thin film with a smooth plating layer by combining different metals in the gradually changing square resistance layer and the non-gradually changing square resistance layer, so that two films are fully overlapped, the interlayer air gap is greatly reduced, the ionization of the interlayer air gap is greatly reduced, the problem of capacity attenuation caused by the peeling of the plating layer due to air gap ionization is also reduced, the gradually changing square resistance of the plating layer is adapted to the distribution of current on the electrode plate (i.e. the plating layer), the overcurrent capacity and the voltage resistance are enhanced, the overcurrent capacity and the self-healing performance are improved, and the problem of oxidation corrosion is also solved.

[0084] The third aspect of the present application provides a metalized film capacitor, which comprises the composite metal thin film described above.

[0085] The metalized film plating layer material is usually zinc, aluminum, or zinc-aluminum. The zinc film has small capacity attenuation in use, but is easily oxidized after contacting air, so it is rarely used now. The aluminum film has good oxidation resistance, but poor voltage resistance, and has large capacity attenuation in use. The zinc-aluminum film combines the advantages of zinc film and aluminum film, but is sensitive to moisture and is easily corroded in a humid environment. The present application realizes the enhancement of the adhesion and oxidation corrosion resistance of the plating layer by adding silver metal. Silver as the first conductive layer enhances the adhesion and the corrosion resistance of the plating layer. Aluminum as the outer protective layer enhances the oxidation resistance of the plating layer, reduces the loss and failure risk of the capacitor. Finally, the problems of poor self-healing caused by the thick plating layer in the thickening area, poor overcurrent capacity caused by the thin plating layer in the active area, low voltage resistance of the capacitor caused by the air gap between the layers due to the unevenness of the electrode plate, large capacity attenuation of the aluminum film, and weak oxidation corrosion resistance of the zinc / zinc-aluminum film are solved.

[0086] Air gap ionization: due to manufacturing, material, etc., there is an air gap between layers of the metalized thin film capacitor. When the applied voltage exceeds a certain value, air gap ionization occurs, which causes the metal plating layer to evaporate and release heat at the same time. The heat accumulation damages the molecular structure of the thin film dielectric, reduces the insulation performance of the dielectric, and finally leads to a decrease in the dielectric voltage level.

[0087] Square resistance: the square resistance of a square metal, i.e. the resistance of a square metal. The square resistance R = p / d, where p is the resistivity of the material and d is the thickness of the material. The higher the square resistance, the thinner the metal plating layer, the better the self-healing performance, which can improve the voltage resistance to a certain extent, but the overcurrent capacity of the plating layer will be worse. The lower the square resistance, the thicker the metal plating layer, the stronger the overcurrent capacity, but the self-healing performance is worse, which is easy to cause the dielectric to be broken down.​

[0088] In the present application, the square resistance is measured by a square resistance meter.

[0089] When the air gap ionization occurs between the layers, the metal layer of the accessory area falls off, or the dielectric is broken down due to thermal damage.

[0090] The conductor resistance is low, and the overcurrent capacity is strong (because the heat is small); the conductor resistance is high, and the overcurrent capacity is weak (because the heat is large).

[0091] The higher the voltage used to break down the capacitor, the stronger the withstand voltage capacity.

[0092] The present application also provides a square resistance parameter calculation and derivation method of a composite metal film, which is specifically as follows:

[0093] 1. Taking the square resistance of the direct-current support capacitor of the electric vehicle as an example: the low square resistance area is 2Ω-6Ω / □, and the high square resistance area is 20Ω-30Ω / □;

[0094] (1) The first metal plating layer is silver, and the left square resistance is set to 100Ω / □, and the thickness d 1左 = ρ1 / R 1左 = 1.65*10 -8 / 100 = 0.165*10 -9 m = 0.165 nm; and the right square resistance is set to 500Ω / □, and the thickness d 1右 = ρ1 / R 1右 = 1.65*10 -8 / 500 = 0.0033*10 -8 m = 0.033 nm;

[0095] (2) The second metal plating layer is aluminum, and the left square resistance is set to 5Ω / □, and the thickness d 2左 = ρ2 / R 2左 = 2.83*10 -8 / 5 = 0.566*10 -8 m = 5.66 nm; and the right square resistance is set to 25Ω / □, and the thickness d 2右 = ρ2 / R 2右 = 2.83*10 -8 / 25 = 0.1132*10 -8 m = 1.132 nm;

[0096] (3) The third metal plating layer is zinc, and the left square resistance is set to 5*10 5 Ω / □, and the thickness d 3左 = ρ3 / R 3左 = 20*10 -3 / (5*10 5) = 4*10 -8 m = 40 nm;

[0097] (4) Now the left thickness is d 左 = d 1左 + d 2左 + d 3左 = 0.165 + 5.66 + 40 = 45.825 nm; the thickness is the same, so the right thickness of the third zinc plating layer is d 3右 = d 左 - d 2右- d 1右 = 44.66 nm = 4.466*10 -8 m.

[0098] Therefore: the right zinc plating layer sheet resistance R 3右 = p3 / d 3右 = 20*10 -3 / (4.466*10 -8 m) = 4.478*10 5 Ω.

[0099] It is concluded that the left comprehensive sheet resistance R 左 = R 1左 / / R 2左 / / R 3左 = 4.762 Ω / □;

[0100] The right comprehensive sheet resistance Rright = R 1右 / / R 2右 / / R 3右 = 23.81 Ω / □;

[0101] (5) The fourth metal plating layer, i.e. the fifth plating layer, is aluminum, which is very thin and flat, has very small sheet resistance, and has little effect on the comprehensive sheet resistance value, only for protection, so its sheet resistance value can not be calculated.

[0102] 2. Taking the sheet resistance commonly used for motor starting / running capacitors in the household appliance industry as an example: low sheet resistance area 2Ω-4Ω / □, high sheet resistance area 10Ω-15Ω / □;

[0103] (1) The first metal plating layer is silver, and its left sheet resistance is set to 100Ω / □, and its thickness d 1左 = p1 / R 1左 = 1.65*10 -8 / 100 = 0.165*10 -9 m = 0.165 nm; similarly, its right sheet resistance is set to 500Ω / □, and its thickness is d 1右 = p1 / R 1右 = 1.65*10 -8 / 500 = 0.0033*10 -8m = 0.033 nm;

[0104] (2) The second metal plating layer is aluminum, and the left sheet resistance is set to 3 Ω / D, and the thickness d 2左 = p2 / R 2左 = 2.83 * 10 -8 / 3 = 0.943 * 10 -8 m = 9.43 nm; similarly, the right sheet resistance is set to 12.5 Ω / D, and the thickness d 2右 = p2 / R 2右 = 2.83 * 10 -8 / 12.5 = 0.2264 * 10 -8 m = 2.264 nm;

[0105] (3) The third metal plating layer is zinc, and the left sheet resistance is set to 5 * 10 5 Ω / D, and the thickness d 3左 = p3 / R 3左 = 20 * 10 -3 / (5 * 10 5 ) = 4 * 10 -8 m = 40 nm;

[0106] (4) The left thickness is now d 左 = d 1左 + d 2左 + d 3左 = 0.165 + 9.43 + 40 = 49.595 nm; the thickness of the third zinc plating layer on the right is d 3右 = d 左 - d 2右- d 1右 = 47.298 nm = 4.7298 * 10 -8 m.

[0107] Therefore: the right zinc plating layer sheet resistance R 3右 = p3 / d 3右 = 20 * 10 -3 / (4.7298 * 10 -8 m) = 4.2285 * 10 5 Ω.

[0108] It is obtained that: the left comprehensive sheet resistance R 左 = R 1左 / / R 2左 / / R 3左 = 2.913 Ω / D;

[0109] The right comprehensive sheet resistance R 右 = R 1右 / / R 2右 / / R 3右 = 12.2 Ω / D.

[0110] The other parameter requirements of the square resistance and the derivation principle are the same as above.

[0111] The present application is described in detail below by way of examples, but the scope of protection of the present application is not limited to the following description.

[0112] In the following examples and comparative examples, the specific conditions not specified are carried out according to the conventional conditions or the conditions recommended by the manufacturer. The reagents or instruments used are conventional products that can be obtained by commercial means.

[0113] Example 1

[0114] A method for preparing a composite metal thin film, as shown in Figure 1 and 5 , specifically comprising the following steps:

[0115] (1) The plastic film is used as the base film 11 of the metallized film;

[0116] (2) The silver plating layer 14 is evaporated on the base film 11. After the evaporation of the silver metal is completed, the silver plating layer on the base film 11 accumulates into a "trapezoidal" cross-sectional structure, i.e. from the edge retention end to the gold spraying end (as shown in Figure 5 from right to left), and the thickness of the silver plating layer gradually increases from thin to thick, i.e. thin on the right and thick on the left;

[0117] (3) The aluminum plating layer 12 is continuously evaporated on the silver plating layer 14. After the evaporation of the aluminum metal is completed, the aluminum plating layer 12 on the silver plating layer 14 accumulates into a "triangular" cross-sectional structure, i.e. from the edge retention end to the gold spraying end (as shown in Figure 5 from right to left), and the thickness of the aluminum plating layer gradually increases from thin to thick, i.e. thin on the right and thick on the left;

[0118] (4) The zinc plating layer 13 is continuously evaporated on the aluminum plating layer 12. After the evaporation of the zinc metal is completed, the zinc plating layer 13 on the aluminum plating layer 12 accumulates into a "triangular" cross-sectional structure, i.e. from the gold spraying end to the edge retention end (as shown in Figure 5 from left to right), and the thickness of the zinc plating layer gradually increases from thin to thick, i.e. thin on the left and thick on the right;

[0119] (5) The aluminum plating layer 15 is continuously evaporated on the zinc plating layer 13. After the evaporation of the aluminum metal is completed, the aluminum plating layer 15 on the zinc plating layer 13 accumulates into a "rectangular" cross-sectional structure, i.e. the thickness of the aluminum plating layer 15 is uniform, and the square resistance is consistent;

[0120] After the evaporation of the silver, aluminum, zinc and aluminum metals according to the above steps is completed, the aluminum, silver and zinc metals are jointly compounded to form a flat metal plating layer structure with the plastic film as the base film. The cross-sectional structure of the metal plating layer structure is "rectangular" shape, and the results are shown in Table 1.

[0121] Comparative Example 1

[0122] A gradually varying sheet resistance metalized film, such as Figure 7 As shown, the base film is the same as that of Example 1, and the plated layer on the base film is divided into a low sheet resistance area (also referred to as a thickened area) and a high sheet resistance area (also referred to as an active area), the plated layer in the low sheet resistance area is thicker, and the plated layer in the active area is thin. The thickened area and the active area are divided into two areas of different thicknesses. The plated layer is generally aluminum, zinc, or zinc-aluminum, and the results are shown in Table 1.

[0123] Comparative Example 2

[0124] A gradually varying sheet resistance metalized film, such as Figure 8 As shown, the base film is the same as that of Example 1, and the plated layer on the base film is a gradually varying thickness plated electrode plate based on Comparative Example 1, and the results are shown in Table 1.

[0125] Table 1

[0126] Example number Air gap ionization Overcurrent capacity Capacitor voltage withstand capability Example 1 None Strong High Comparative Example 1 High risk Weak Weak Comparative Example 2 High risk Strong Weak

[0127] As can be seen from the results in Table 1, the present application uses the existing metalized film evaporation process to evaporate silver on the base film as the first layer of electrode plate material, which plays a role in enhancing adhesion and enhancing resistance to oxidation and corrosion; evaporate aluminum on the first layer of silver plated layer as the second layer of electrode plate material, which plays a role in determining the sheet resistance at different positions; evaporate zinc on the second layer of aluminum plated layer as the third layer of electrode plate material, which plays a role in filling the entire electrode plate, so that the entire electrode plate composed of three different metal materials in parallel becomes a flat electrode plate with uniform thickness; evaporate a thin aluminum plated layer on the third layer of zinc plated layer as the outermost layer, which plays a role in protecting the metal plated layer from oxidation; and finally obtain a flat, sheet resistance gradually varying, and not easily oxidized and corroded capacitor electrode plate. The flat capacitor electrode plate is conducive to the full overlap of two or more metalized films, avoiding the problem of air gap between layers caused by uneven electrode plates, further avoiding the problem of ionization of interlayer air gap under an applied electric field, and improving the withstand voltage level of the capacitor. At the same time, the gradually varying sheet resistance structure also achieves the purpose of enhancing the overcurrent capacity and self-healing.

[0128] The preferred embodiments of the present application are described in detail above, but the present application is not limited thereto. Within the technical concept of the present application, various simple modifications can be made to the technical solutions of the present application, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be considered as disclosed by the present application and fall within the protection scope of the present application.

Claims

1. A method for producing a composite metal thin film, characterized by, The preparation method comprises the following steps: forming a gradient sheet resistance layer (12) on a base film (11) by an evaporation method, and forming a reserved edge on the base film (11); then forming a filling layer (13) on the gradient sheet resistance layer (12) by the evaporation method, so that the outer surface of the filling layer (13) is parallel to the surface of the base film (11), to obtain a composite metal film; wherein the thickness of the gradient sheet resistance layer (12) gradually increases from the reserved edge end (1A) to the gold spraying end (1B), and the thickness of the filling layer (13) gradually decreases. The resistivity of the material of the gradient sheet resistance layer (12) is a, and the resistivity of the material of the filling layer (13) is b, and a and b satisfy the relationship: b>a.

2. The production method according to claim 1, characterized by, The longitudinal cross-sectional structure of the base film (11) is rectangular. And / or, the longitudinal cross-sectional structure of the gradient sheet resistance layer (12) is trapezoidal or triangular. And / or, the longitudinal cross-sectional structure of the filling layer (13) is trapezoidal or triangular.

3. The production method according to claim 1 or 2, characterized by, The material of the gradient sheet resistance layer (12) is silver, aluminum, copper or gold.

4. The method of claim 1, wherein, Before forming the gradient sheet resistance layer (12) on the base film (11), the preparation method further comprises: forming a substrate layer (14) on the base film (11) by an evaporation method, and forming a reserved edge on the base film (11); then forming a gradient sheet resistance layer (12) on the substrate layer (14); wherein the thickness of the substrate layer (14) gradually increases from the reserved edge end (1A) to the gold spraying end (1B).

5. The preparation method according to claim 1, characterized in that, The material of the base film (11) is polypropylene or polyester. And / or, the material of the filling layer (13) is zinc, tin, tungsten or platinum.

6. The method of claim 1, wherein, a and b satisfy the relationship: b>2a.

7. The preparation method according to claim 1, characterized in that, After forming the filling layer (13), the preparation method further comprises: forming a protective layer (15) on the filling layer (13) by an evaporation method; wherein the longitudinal cross-sectional structure of the protective layer (15) is rectangular.

8. The preparation method according to claim 7, characterized in that, After forming the protective layer (15) on the filling layer (13), the preparation method further comprises: forming an antioxidant oil layer on the outer surface of the protective layer (15) by a coating method.

9. The production method according to claim 8, characterized by, The material of the antioxidant oil layer is one or more of silicone oil, epoxy soybean oil, palm oil, castor oil and paraffin oil.

10. A composite metal film, characterized by, The composite metal film is prepared by the preparation method of any one of claims 1-9.

11. A metallized film capacitor characterized by, The metallized film capacitor comprises the composite metal film of claim 10.

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