Capacitor and method for manufacturing same

Abstract

A capacitor (1) comprises a body (10) in which dielectric layers (13) and electrode layers (11) are laminated, and an external electrode (20) that is connected via a metal plating to at least a portion of the body. The dielectric layers have a thickness Dt at a connection boundary with the external electrode of the body, the electrode layers have a thickness Et at the connection boundary, and the ratio DE between the thickness Dt and the thickness Et is at least a first value DEmin. The first value DE may satisfy the conditions below with respect to a minimum set value Dt1 of the thickness Dt. DEmin ≥ a × Dt1 + b, and 0.1 μm ≤ Dt1 ≤ Dt ≤ 1.5 μm, where a and b are coefficients

Description

Capacitor and manufacturing method thereof

[0001] The present invention relates to a capacitor and a method for manufacturing the same.

[0002] The thin-film polymer laminate capacitor described in Japanese Patent Application Laid-Open No. 2021-19133 has a chip-shaped laminate formed by alternately stacking and bonding dielectric layers and internal electrode layers including a first metal layer formed by vapor-depositing a first metal on the dielectric layer and a second metal layer formed by vapor-depositing a second metal on the first metal layer, and external electrodes formed on one end and the other end of the laminate, and the laminate has a first region in which the first metal is formed and alternately stacked on the dielectric layers, and an edge region in which a second metal layer is formed and alternately stacked on the layers of the first metal layer connected to the one end and the layers connected to the other end, and the first region has a capacitor functional region, and the edge region has a heavy edge.

[0003] Compared to film capacitors, thin-film polymer multilayer capacitors can have dielectric layers as thin as 1.5 μm or less, providing small capacitors with high withstand voltage and low ESR. Furthermore, it is important to obtain good connectivity with the external electrodes and good withstand voltage characteristics.

[0004] In recent years, there has been a demand for capacitors with even higher withstand voltages and lower ESRs. Accordingly, heavy-edge structures have been adopted, in which the electrode portions (internal electrode portions) of the capacitor are thinned to ensure a sufficiently high surface resistivity (sheet resistivity) in order to increase the withstand voltage, and the connection portions with the external electrodes are thickened. Furthermore, there is a trend toward thicker electrode connection portions in order to further reduce the connection resistance of the connection portions and sufficiently reduce ESR.

[0005] In response to this, the present inventors discovered that if the edge portions are made even thicker, excessive thickness can cause unstable connections with external electrodes formed by metallikon, making it difficult to provide capacitors with stable performance at low cost. While it has been thought that thicker electrode layers at the connection portions are preferable for achieving good connection performance with external electrodes, the present inventors discovered that in thin-film multilayer capacitors, to achieve the desired connection performance, there is a limit to the thickness of the electrode layer at the connection boundary relative to the thickness of the dielectric layer, and that a dielectric layer of a predetermined thickness relative to the thickness of the electrode layer is required. Furthermore, the inventors discovered that when the ratio DE of the thickness Dt of the dielectric layer to the thickness Et of the electrode layer (DE = Dt / Et) is set as an index, the ratio DE has a minimum value, and that the ratio DE is at least a predetermined value (first value, minimum value) DEmin. This means that when the ratio ED (ED = Et / Dt) of the thickness Et of the electrode layer to the thickness Dt of the dielectric layer is set, the ratio ED has a maximum value and does not exceed a predetermined value (maximum value) EDmax.

[0006] That is, one aspect of the present invention is a capacitor having a main body portion in which a dielectric layer and an electrode layer are laminated, and an external electrode (metallicon layer) connected to at least a portion of the main body portion by metallicon, wherein the dielectric layer includes a thickness Dt at the connection boundary with the external electrode of the main body portion, the electrode layer includes a thickness Et at the connection boundary, and the ratio of thickness Dt to thickness Et is at least a first value DEmin.

[0007] Furthermore, the inventors of the present application have found that when a minimum value Dt1 is set for the thickness Dt of the dielectric layer at the connection boundary, the first value DEmin has a correlation that can be expressed by a linear equation with respect to the minimum set value Dt1. The minimum value DEmin of the ratio DE of the thickness Dt of the dielectric layer at the connection boundary with the external electrode of the main body to the thickness Et of the electrode layer may satisfy the following conditions (1) and (2): DEmin≧a×Dt1+b (1) 0.1 μm≦Dt1≦Dt≦1.5 μm (2) where a and b are coefficients.

[0008] In this capacitor, the thickness Et of the electrode layer at the connection boundary may satisfy the following condition (7): Et≦Dt / DEmin (7) Also, in this capacitor, the thickness Dt of the dielectric layer at the connection boundary may satisfy the following condition (8): Dt≧DEmin×Et (8)

[0009] The first value DEmin may satisfy the following condition (3a): DEmin≧5.0Dt1+1.7 (3a)

[0010] The electrode layer may contain at least one of aluminum, zinc, copper, gold, silver, or an alloy containing any of these. The electrode layer may also include a heavy edge portion where the connection portion with the external electrode is thicker than the internal electrode portion, and the heavy edge portion may contain aluminum, zinc, or an alloy thereof. The electrode layer may also include a dummy edge portion where the connection portion with the external electrode is separated from the internal electrode portion. The dielectric layer may contain a thermosetting resin. The external electrode formed by metallikon may contain at least one of aluminum, zinc, copper, or an alloy containing any of these.

[0011] Another aspect of the present invention is a method for manufacturing a capacitor having a body portion formed by laminating dielectric layers and electrode layers, and an external electrode connected to at least a portion of the body portion, the method comprising laminating the dielectric layers and the electrode layers so that a ratio of a thickness Dt of the dielectric layer at a connection boundary between the body portion and the external electrode and a thickness Et of the electrode layer at the connection boundary is at least a first value DEmin.

[0012] 1 is a diagram showing an overview of a capacitor; 2 is a cross-sectional view showing an overview of an active layer (laminate); 3 is a flowchart showing an overview of a manufacturing process of a capacitor; 4 is a diagram showing evaluation results of Example 1; 5 is a diagram showing evaluation criteria; 6 is a diagram showing a summary of the evaluation results of Example 1; 7 is a diagram showing correlations based on the evaluation results of Example 1; 8 is a diagram showing evaluation results of Example 2; 9 is a diagram showing a summary of the evaluation results of Example 2; 10 is a diagram showing correlations based on the evaluation results of Example 2; 11 is a diagram showing evaluation results of Example 3; 12 is a diagram showing a summary of the evaluation results of Example 3; 13 is a diagram showing correlations based on the evaluation results of Example 3. MODE FOR CARRYING OUT THE INVENTION

[0013] FIG. 1 shows an example of a capacitor according to the present invention. A thin-film polymer multilayer capacitor is known as a capacitor 1 having a main body (main body, laminate) 10 in which dielectric layers and electrode layers are laminated together, and external electrodes 20 connected to the main body 10. The capacitor 1 shown in FIG. 1( a) is an example of a thin-film polymer multilayer capacitor. As shown in the cross-sectional view of FIG. 1( b), the main body 10 includes an active layer 7 that exhibits capacitance and is located at the center in the thickness direction, dummy layers 8 that do not exhibit capacitance and are located above and below the active layer 7, and protective layers 9 that are located above and below the active layer 7. The active layer 7 and dummy layer 8 are configured by laminating a resin layer (dielectric layer) 13 and an electrode layer 11, and the protective layer 9 is composed solely of resin. The external electrode 20 is formed of metallikon so as to join the electrode layer 11 and resin layer 13 of the active layer 7 and the dummy layer 8, and includes an inner metallikon layer (e.g., brass metallikon) 21, a copper plating layer 22 covering the periphery thereof, and a tin plating layer 23 covering the outside.

[0014] FIG. 2 shows an enlarged cross section of a portion of the active layer 7 of the main body 10. The active layer 7 of the main body 10 is a laminated portion of a dielectric layer 13 and an electrode layer 11. The end sides (side surfaces, edges, connection portions, connection regions, connection boundaries) 18 of the dielectric layer 13 and the electrode layer 11 are joined to a metallikon layer 21 of an external electrode 20. The electrode layer 11 is also electrically connected to the metallikon layer 21. The electrode layer 11 includes a thin-film internal electrode portion 15 that widely contacts the dielectric layer 13 inside the active layer 7 and forms a capacitance, and an edge portion 16 that connects to the external electrode 20 (metallikon layer 21). An example of an edge portion is a heavy edge portion 16 in which the connection portion (connection boundary) 18 that connects to the external electrode 20 is thicker than the internal electrode portion 15. In this example, the heavy edge portion 16 that forms the electrode layer thickness at the connection boundary 18 of the electrode layer 11 is composed of the electrode layer 11 and a layer 12 laminated on the electrode layer 11. When providing a capacitor 1 with a high withstand voltage, it is desirable that the thickness of the internal electrode layer (internal electrode portion) 15 is thin. The thickness of the internal electrode layer 15 may be, for example, 0.01 μm, or even thinner, 0.005 μm (5 nm). On the other hand, considering the connection with the external electrode 20, a thickness of about 0.01 μm or more is considered necessary, and a capacitor 1 having a thin-film type internal electrode portion 15 may be provided with a heavy edge portion 16. Note that if the internal electrode portion 15 has a sufficient thickness, the heavy edge portion 16 may not be provided.

[0015] An example of the resin constituting the dielectric layer 13 is a thermosetting resin, including an acrylic polymer. An example of a resin that can be used in the thin-film polymer multilayer capacitor 1 is a polymerized version of one or more of tricyclodecane dimethanol dimethacrylate or tricyclodecane dimethanol diacrylate, but the resin constituting the dielectric layer 13 is not limited to these. To provide a small, thin, and high-capacity capacitor, the dielectric layer 13 may be sufficiently thin and have a sufficient number of layers. For example, the thickness of the dielectric layer 13 may be 0.1 to 1.5 μm or 0.2 to 1.2 μm, and the number of layers may be 1,000 or more. The thin-film dielectric layer 13 can be formed by depositing a thermosetting resin as a monomer under a reduced pressure (vacuum) and curing it by irradiation with an electron beam or the like, thereby achieving a dielectric layer 13 of a predetermined thickness. Capacitors 1 with a dielectric layer 13 made of a thermosetting resin have a higher heat resistance temperature and are reflow-compatible compared to those with a thermoplastic resin, making them more suitable for surface mounting.

[0016] The electrode layer 11 may be formed of at least one conductive metal, such as aluminum, zinc, copper, gold, silver, or an alloy containing any of these. For a high-voltage capacitor 1, the withstand voltage can be improved by reducing the thickness of the electrodes that function as a capacitor, i.e., the internal electrode portion 15. For example, the withstand voltage may be 400 V or more, and the thickness of the internal electrode portion 15 may be approximately 10 to 160 nm, or approximately 15 to 150 nm. The thickness of the thin-film electrode may be controlled using surface resistivity, and the surface resistivity of the internal electrode portion 15 may be 5 to 80 Ω / □ (Ω / sq.), 15 to 80 Ω / □, or 20 to 80 Ω / □.

[0017] The electrode layer 11 of the capacitor 1 may further include a dummy heavy edge portion (dummy edge portion) 17 separated from the internal electrode portion 15 by a gap 19. Because the dummy edge portion 17 is separated from the internal electrode portion 15, it does not contribute to the capacitance of the capacitor 1. However, it is useful for obtaining mechanical connection strength between the external electrode 20 and the metallikon layer 21, and by cooperating with the heavy edge portion 16 integrated with the internal electrode portion 15, it maintains or strengthens the connection with the metallikon layer 21. In this example, the layer 12 constituting the heavy edge portion 16 may be laminated above or below the electrode layer 11, or may be laminated on both the top and bottom surfaces. The heavy edge portion 16 is not limited to a two-layer structure, and may be a single-layer structure or a three- or more-layer structure.

[0018] Although the withstand voltage can be increased by making the electrode layer 11 thin, the loss factor (tan δ) and equivalent series resistance (ESR) also increase, which tends to reduce the performance of the capacitor. For this reason, the configuration of the connection portion 18 between the electrode layer 11 and the external electrode 20 is important. Conventionally, it was thought that even if the internal electrode portion 15 was thin, by ensuring a sufficient thickness of the connection portion 18 with the external electrode 20, in this example, the metallikon layer 21, the tan δ and ESR would decrease, the frequency characteristics would improve, and the capacitor would be able to handle high currents.

[0019] In multilayer capacitors such as film capacitors and thin-film polymer multilayer capacitors, metallicon is the method used to connect the laminate (main body) 10 and the external electrodes 20 to the extent that they are commercially available. It is currently difficult to ensure the mechanical strength required for a capacitor with methods other than metallicon. In the case of conventional film capacitors, the thickness of the dielectric layer is several micrometers or more, and this is thought to be due to the film being offset. However, there is no indication that there is a limit to the thickness of the electrode layer (metal layer) when connecting with the metallicon layer. Therefore, even in film capacitors, a heavy edge structure is sometimes adopted to ensure the electrode thickness at the connection portion.

[0020] In contrast, as will be described in detail below, research by the inventors of the present application has revealed that if the thickness Et of the electrode layer 11 (in this example, the thickness of the heavy edge portion 16) at the connection portion (connection boundary) 18 between the main body 10 and the external electrode 20 is too thick, connection by the metallikon layer 21 may not be possible or the connection resistance may become high. In particular, it has been found that this tendency is clearly evident in products such as the capacitor 1 described in the following embodiment, in which the thickness Dt of the dielectric resin layer (dielectric layer) 13 is thinner than 1.5 μm, and even thinner than 1.0 μm.

[0021] One of the reasons why a connection using the metallikon layer 21 cannot be made or the connection resistance becomes high when the thickness Et of the electrode layer 11 is too thick is thought to be that if the thickness Dt of the dielectric layer 13 is insufficient relative to the thickness Et of the electrode layer 11 at the connection boundary 18, the metal layer of the electrode layer 11 exposed by electrode extraction (ashing) will be spaced closely and thick, resulting in high density. For this reason, the semi-molten metal injected by the metallikon device to create the metallikon layer 21 stops midway before reaching the dielectric layer 13, and is unable to penetrate into the laminate 7 of the main body 10, making it impossible to ensure connection strength. For example, this can be thought to be because the metal of the electrode layer 11 exposed at the connection boundary 18 acts like a cushion. Furthermore, even if the metal portion of the exposed electrode layer 11, for example, the heavy edge portion 16, is thick, it is only about several tens to several hundreds of nanometers thick. With this thickness, the electrode layer 11 exposed at the connection boundary 18 alone is not strong enough to be connected to the metallikon metal, and it may break easily, making it difficult to maintain electrical connection and connection strength.

[0022] Therefore, in order to obtain good electrical connection and connection strength between the main body 10 and the external electrode 20, it is considered necessary to make the metal of the metallikon layer 21 penetrate into the entire laminate 7, i.e., including the dielectric layer 13.

[0023] FIG. 3 shows an example of a manufacturing method for the capacitor 1. In this manufacturing method 40, in step 41, a laminate that serves as the base of the main body (main body portion) 10 is manufactured. One example of a method for manufacturing the laminate is a method of forming each layer by vapor deposition. A known apparatus manufactures the laminate that serves as the base of the main body portion 10 by alternately depositing a dielectric layer 13 and an electrode layer 11 by vapor deposition on a drum rotating in a reduced-pressure environment (vacuum environment) in a vacuum chamber. The laminate may also be manufactured using other methods, such as coating or printing. The thermosetting resin vapor-deposited as the dielectric layer 13 may be cured using an electron beam irradiation device or the like to form the dielectric layer 13. Furthermore, the surface of the dielectric layer 13 may be plasma-treated in a plasma processing device for the next process. Before forming the electrode layer 11, an inner margin may be formed by applying an oil margin to the dielectric layer 13 using a patterning unit to pattern the electrode layer 11.

[0024] When the electrode layer 11 is formed in step 41, the heavy edge portion 16 and the dummy edge portion 17 are formed. Therefore, in step 41, the dielectric layer 13 and the electrode layer 11 are laminated so that the film thickness Dt at the connection boundary 18 of the dielectric layer 13 and the film thickness Et at the connection boundary of the electrode layer 11 are predetermined values, thereby manufacturing the main body 10. Instead of forming an inner margin using an oil margin, a method of forming a margin at the edge can also be adopted. However, since the contact portion (connection boundary) is affected by the margin oil, there is a high possibility of unstable quality. Furthermore, the dummy edge portion (dummy heavy edge portion) 17 is a portion that is cut off from the required heavy edge portion 16 on the opposite side during line cutting in the next process. The heavy edge portion 16 connected to the electrode layer 11 by line cutting and the dummy edge portion 17 separated from the electrode layer 11 by the margin are simultaneously formed. This prevents the creation of unnecessary portions and the need for additional cutting processes. Therefore, forming an inner margin using an oil margin and providing a dummy edge portion 17 as in this example is effective for manufacturing a capacitor 1 with stable performance and contributes to improving production efficiency. For this reason, it is useful to consider the dummy edge portion 17 in each of the following examples.

[0025] In step 42, the laminate is cut into strips to form the main body 10 in a strip state (stick state). The main body 10 in a strip state may be formed directly from the laminate, or the main body 10 in a strip state may be manufactured by performing other processes such as a flattening press process or a card cutting process. In step 43, the cut strip surface is subjected to plasma ashing as a connection portion (connection boundary, connection surface) 18 with the external electrode 20. As an example, plasma ashing may be performed using a mixed gas of oxygen and carbon tetrafluoride.

[0026] In step 44, a metallikon layer 21 of the external electrode 20 is formed by metallikon (metal spraying) on ​​the plasma-ashed connection boundary 18. The metallikon layer 21 is produced by a method in which, for example, zinc, copper, aluminum, or an alloy containing these, such as brass, is melted and arc-sprayed onto the connection boundary 18 from a distance of 50 to 200 mm (metallikon distance) at an air pressure of about 0.2 to 0.8 MPa.

[0027] In step 45, a copper plating layer 22 and a tin plating layer 23 are formed in this order by electrolytic plating or the like. The tin plating layer 23 is effective in improving the solder wettability of the external electrodes 20. Then, the required treatment for the external electrodes 20, such as heat treatment, is performed. Furthermore, in step 46, the strip-like body 10 on which the external electrodes 20 have been formed is cut into chips together with the external electrodes 20, thereby producing a capacitor 1 in which the external electrodes 20 are connected to the body 10. The steps shown in FIG. 3 are representative of the process, and other processes may also be performed.

[0028] Figure 4 shows an example of the results of evaluating the performance of capacitors 1 manufactured with different thicknesses Dt of the dielectric layer 13 at the connection boundary 18 and Et of the electrode layer 11 at the connection boundary 18. In this experiment (Example 1), the internal electrode portion 15 of the electrode layer 11 was made of aluminum with a thickness of 5 nm, and the heavy edge portion 16 was formed by laminating (depositing) an aluminum layer as layer 12. The heavy edge portion was formed with a total thickness Et as shown in Figure 4. The dielectric layer 13 was made of resin, using tricyclodecane dimethanol diacrylate. The body 10 was 1.4 mm thick, and the metallikon layer 21 of the external electrode 20 was a zinc metallikon layer. Furthermore, before forming the metallikon layer 21 at the boundary portion 18, the heavy edge portion 16 at the end of the electrode layer 11 was extracted by plasma treatment to form a 20-50 μm roughness on the external electrode bonding surface of the body 10. Thereafter, zinc was arc sprayed at a metallikon distance of 125 mm and an air pressure of 0.5 MPa to form a metallikon layer 21 .

[0029] Figure 5 shows the criteria (evaluation criteria) for determining characteristics. The characteristics of each manufactured capacitor 1 were evaluated based on the capacitance when a 1 kHz AC current was applied and the loss factor (tan δ). When the connection with the metallikon layer 21 deteriorates, the electrical characteristics deteriorate, followed by a deterioration in the physical connection strength. Among the electrical characteristics, tan δ deteriorates first, followed by a decrease in the capacitance appearance rate. As shown in Figure 4, when the thickness Et of the electrode layer 11 exceeds a predetermined value relative to the thickness Dt of the dielectric layer 13, the characteristics of the capacitor 1 deteriorate. Therefore, if the thickness Et of the electrode layer 11 is too thick relative to the thickness Dt of the dielectric layer 13, the characteristics deteriorate, and it is clear that there is an upper limit (maximum value) for the thickness Et of the electrode layer 11. Conversely, if the thickness Dt of the dielectric layer 13 is too small relative to the thickness Et of the electrode layer 11, the characteristics deteriorate, and it is clear that there is a lower limit (minimum value) for the thickness Dt of the dielectric layer 13 relative to the thickness Et of the electrode layer 11.

[0030] The evaluation results of Example 1 are summarized in Fig. 6. Fig. 6 shows the upper limit Etmax1 of the thickness Et of the electrode layer 11 in the boundary region 18 that satisfies the evaluations of ◎, ◯, and △, the upper limit Etmax2 of the thickness Et of the electrode layer 11 in the boundary region 18 that satisfies the evaluations of ◎ and ◯, the lower limit Etmin1 of the thickness Et of the electrode layer 11 in the boundary region 18 that satisfies the evaluations of ◎, ◯, and △, and the lower limit Etmin2 of the thickness Et of the electrode layer 11 in the boundary region 18 that satisfies the evaluations of ◎ and ◯, relative to the thickness Dt of the dielectric layer 13 in the boundary region 18.

[0031] According to the evaluation results, it was found that the lower limits Etmin1 and Etmin2 of the thickness Et of the electrode layer 11 are each constant and do not depend on changes in the thickness of the dielectric layer 13. On the other hand, the upper limits Etmax1 and Etmax2 of the thickness Et of the electrode layer 11 each increase as the thickness Dt of the dielectric layer 13 increases. However, it was found that the ratio between them is not constant, and although the upper limit of the thickness Et of the electrode layer 11 increases as the thickness Dt of the dielectric layer 13 increases, no proportional correlation is observed.

[0032] 6 further shows a value DE1 (DE1=Dt / Etmax1) that allows for evaluations up to △ and a value DE2 (DE2=Dt / Etmax2) that allows for evaluations up to ◯ of the ratio DE (DE=Dt / Et) of the thickness Dt of the dielectric layer 13 to the thickness Et of the electrode layer 11 at the connection boundary 18 with the external electrode 20 of the main body 10. The evaluations △ and ◯ are evaluations that indicate the minimum value Dt1 of the thickness Dt of the dielectric layer 13, and the values ​​DE1 and DE2 are the minimum value DEmin for each evaluation. Also shown are the reciprocals of these, the value ED1 (ED1 = Etmax1 / Dt) that allows for evaluations up to △ of the ratio ED (ED = Et / Dt) of the thickness Et of the electrode layer 11 at the connection boundary 18 to the thickness Dt of the dielectric layer 13, and the value ED2 (ED2 = Etmax2 / Dt) that allows for evaluations up to ◯. The values ​​ED1 and ED2 are the maximum values ​​EDmax in the respective evaluations.

[0033] 7(a) shows the value DE1 versus the minimum value of the thickness Dt of the dielectric layer 13 (minimum set value Dt1, the thickness for which a rating of △ or ◯ was obtained), FIG. 7(b) shows the value DE2 versus the minimum set value Dt1 of the thickness Dt of the dielectric layer 13, FIG. 7(c) shows the value ED1 versus the maximum value Etmax1 (maximum set value Et1) of the electrode layer 11, and FIG. 7(d) shows the value ED2 versus the maximum value Etmax2 (maximum set value Et1) of the electrode layer 11. As can be seen from these figures, the values ​​DE1 and DE2 show a strong correlation, expressed by a linear equation, with the minimum set value Dt1 of the thickness Dt of the dielectric layer 13, and it can also be seen that the values ​​ED1 and ED2 show a correlation, expressed by a linear equation, with the maximum value Et1 of the thickness Et of the electrode layer 11. Therefore, by setting the minimum value Dt1, i.e., by determining the minimum set value Dt1, the minimum value of the values ​​DE1 and DE2 can be obtained, and by setting the maximum value Et1, i.e., by determining the maximum set value Et1, the maximum value of the values ​​ED1 and ED2 can be obtained.

[0034] The correlation function between the value DE1 shown in Figure 7(a) and the minimum set value Dt1 (μm) of the thickness of the dielectric layer 13 is given by the following equation (ex1a), and its correlation coefficient R2 is 0.9994: DE1 = 5.0602Dt1 + 1.732 ... (ex1a) The correlation function between the value DE2 shown in Figure 7(b) and the minimum set value Dt1 (μm) of the thickness of the dielectric layer 13 is given by the following equation (ex1b), and its correlation coefficient R2 is 0.9967: DE2 = 5.0985Dt1 + 2.2198 ... (ex1b) The correlation function between the value ED1 shown in Figure 7(c) and the maximum set value Et1 (μm) of the thickness of the electrode layer 11 is given by the following equation (ex1c), and its correlation coefficient R2 is 0.9935. 7D and the maximum set value Et1 (μm) of the thickness of the electrode layer 11 is expressed by the following equation (ex1d), and its correlation coefficient R2 is 0.9783: ED2=-2.2667Et1+0.4479... (ex1d)

[0035] As a different example, Figure 8 shows the results of evaluating the performance of capacitors 1 manufactured with different thicknesses Dt of the dielectric layer 13 in the boundary region 18 and different thicknesses Et of the electrode layer 11 in the boundary region 18. In this example (Example 2), the internal electrode portion 15 of the electrode layer 11 was made of aluminum with a thickness of 5 nm, and a zinc layer 12 was formed to form the heavy edge portion 16, resulting in a heavy edge portion 16 with a total thickness Et, as shown in Figure 8. The other conditions were the same as in Example 1, and the metallikon layer 21 was also formed under the same conditions. In this example, the characteristics of each capacitor 1 were evaluated using the evaluation criteria shown in Figure 5, with ◎, ◯, △, and ×.

[0036] The evaluation results are summarized in FIG. 9 . In this example, too, the lower limits Etmin1 and Etmin2 of the thickness Et of the electrode layer 11 were constant and independent of the change in the thickness of the dielectric layer 13. Meanwhile, the upper limits Etmax1 and Etmax2 of the thickness Et of the electrode layer 11 increased as the thickness Dt of the dielectric layer 13 increased. However, in this example, the ratio between them was not constant. As the thickness Dt of the dielectric layer 13 increased, the upper limit of the thickness Et of the electrode layer 11 increased, but no proportional correlation was observed. Therefore, as in Example 1 above, FIG. 9 shows the values ​​DE1, DE2, ED1, and ED2, and FIGS. 10(a) to 10(d) show their correlations.

[0037] 10(a) to 10(d), in this example as well, the values ​​DE1 and DE2 show a strong correlation, as expressed by a linear equation, with the minimum value Dt1 of the thickness Dt of the dielectric layer 13, and the values ​​ED1 and ED2 also show a correlation, as expressed by a linear equation, with the maximum value Et1 of the thickness Et of the electrode layer 11. That is, the correlation function between the value DE1 shown in FIG. 10(a) and the minimum set value Dt1 (μm) of the thickness of the dielectric layer 13 is given by the following equation (ex2a), with a correlation coefficient R2 of 0.9981: DE1 = 4.9501Dt1 + 1.8391 ... (ex2a) The correlation function between the value DE2 shown in FIG. 10(b) and the minimum set value Dt1 (μm) of the thickness of the dielectric layer 13 is given by the following equation (ex2b), with a correlation coefficient R2 of 0.9995. 10(c) is the correlation function between the value ED1 and the maximum set value Et1 (μm) of the thickness of the electrode layer 11 as shown in (c) of FIG. 10, and the correlation coefficient R2 is 0.9802. ED1 = -2.4654Et1 + 0.5173 ... (ex2c) ED2 = -2.1761Et1 + 0.4237 ... (ex2d) ED2 = -2.1761Et1 + 0.4237 ... (ex2d)

[0038] As a further different example, Figure 11 shows the results of evaluating the performance of a capacitor 1 manufactured by forming an aluminum metallikon layer 21 on a main body 10 having a boundary region 18 under the same conditions as in Example 2. In this example (Example 3), the metallikon layer 21 was formed by arc spraying aluminum at a metallikon distance of 125 mm and an air pressure of 0.5 MPa. In this example, too, the characteristics of each capacitor 1 were evaluated using the evaluation criteria shown in Figure 5, with ◎, ◯, △, and ×.

[0039] The evaluation results are summarized in FIG. 12 . In this example, too, the lower limits Etmin1 and Etmin2 of the thickness Et of the electrode layer 11 were constant and independent of the change in the thickness of the dielectric layer 13. Meanwhile, the upper limits Etmax1 and Etmax2 of the thickness Et of the electrode layer 11 increased as the thickness Dt of the dielectric layer 13 increased. However, in this example, the ratio between them was not constant. As the thickness Dt of the dielectric layer 13 increased, the upper limit of the thickness Et of the electrode layer 11 increased, but no proportional correlation was observed. Therefore, as in Example 1 above, FIG. 12 shows the values ​​DE1, DE2, ED1, and ED2, and FIGS. 13(a) to 13(d) show the correlations among them.

[0040] 13(a) to 13(d), in this example as well, the values ​​DE1 and DE2 show a strong correlation, as expressed by a linear equation, with the minimum value Dt1 of the thickness Dt of the dielectric layer 13, and the values ​​ED1 and ED2 also show a correlation, as expressed by a linear equation, with the maximum value Et1 of the thickness Et of the electrode layer 11. That is, the correlation function between the value DE1 shown in FIG. 13(a) and the minimum set value Dt1 (μm) of the thickness of the dielectric layer 13 is given by the following equation (ex3a), and its correlation coefficient R2 is 0.9963: DE1 = 5.2073Dt1 + 1.7485 ... (ex3a) The correlation function between the value DE2 shown in FIG. 13(b) and the minimum set value Dt1 (μm) of the thickness of the dielectric layer 13 is given by the following equation (ex3b), and its correlation coefficient R2 is 0.9988. 13(c) is the correlation function between the value ED1 and the maximum set value Et1 (μm) of the thickness of the electrode layer 11 as shown in FIG. 13(c) and the correlation coefficient R2 is 0.9609. ED1 = -2.5799Et1 + 0.5261 ... (ex3c) 13(d) is the correlation function between the value ED2 and the maximum set value Et1 (μm) of the thickness of the electrode layer 11 as shown in FIG. 13(d) and the correlation coefficient R2 is 0.991. ED2 = -2.2163Et1 + 0.4365 ... (ex3d)

[0041] From these examples, it was found that, as a condition for obtaining good connection characteristics, there is a lower limit to the ratio DE of the thickness Dt of the dielectric layer 13 to the thickness Et of the electrode layer 11 at the connection boundary 18. It was also found that, as a condition for obtaining good connection characteristics, there is an upper limit to the ratio ED of the thickness Et of the electrode layer 11 to the thickness Dt of the dielectric layer 13 at the connection boundary 18. It was also found that, as a condition for obtaining good connection characteristics, there is a correlation expressed by a linear equation between the minimum value DEmin of the ratio DE and the minimum value Dt1 of the thickness of the dielectric layer 13, and that there is a correlation expressed by a linear equation between the maximum value EDmax of the ratio ED and the maximum value Et1 of the thickness of the electrode layer 11.

[0042] In particular, it was found that within the range of the following condition (2), the correlations obtained for each evaluation were very similar regardless of the structure of the electrode layer 11 or the composition of the metallikon, and the coefficients of the linear equation showing the correlation could be calculated as follows. Therefore, by manufacturing a capacitor so that the following condition is satisfied, it is possible to provide a capacitor with good connection characteristics. It was also found that within the range of the following condition (2), where the thickness Dt of the dielectric layer 13 was covered in these examples, there are upper and lower limits to the thickness Et of the electrode layer 11 that provides good connection characteristics at the connection boundary 18. Furthermore, the lower limit Etmin of the thickness Et of the electrode layer 11 is considered to be constant relative to the thickness Dt of the dielectric layer 13, and it is desirable to satisfy the following condition (4). The lower limit of condition (4) may be 0.015 μm, which would result in more stable connection characteristics. This relationship may also be used as the upper limit Dtmax of the thickness Dt of the dielectric layer 13 relative to the thickness Et of the connection portion of the electrode layer 11. That is, the upper limit Dtmax may be the following condition (4'). 0.1μm≦Dt1≦Dt≦1.5μm...(2) Etmin≧0.010μm...(4) Dtmax≦1.5μm...(4')

[0043] If the thickness Dt of the dielectric layer 13 is thinner than 0.1 μm, it becomes difficult to form a margin for manufacturing the capacitor, and the laminate itself becomes hard and brittle. This makes it difficult to consistently manufacture capacitors with good characteristics. On the other hand, if the thickness Dt of the dielectric layer 13 is thicker than 1.5 μm, it becomes difficult to uniformly cure the monomer by electron beam irradiation, and curing takes a long time. Therefore, if the range of condition (2) is exceeded, it becomes difficult to achieve stable quality and realistic mass productivity in the thin-film polymer multilayer capacitor 1.

[0044] In the above example, it was found that the upper limit Etmax (Et1) of the thickness Et of the electrode layer 11 in the boundary region 18 increases as the thickness Dt of the dielectric layer 13 increases. Furthermore, when focusing on the values ​​DE1 and DE2, which are the ratios of the upper limit Etmax to the minimum value (minimum set value) Dt1 of the thickness Dt, i.e., the minimum value DEmin of the value DE, it was found that there is a linear correlation with the minimum set value Dt1 of the thickness of the dielectric layer 13. Therefore, in order to provide a capacitor 1 with good connection characteristics, it is desirable for the range of the following condition (5) to be satisfied. Note that DEmin is expressed by condition (1), and DEmax is expressed by condition (6) because Etmin is constant. DEmin≦Dt / Et≦DEmax (5) DEmin≧a×Dt1+b (1) DEmax≦c×Dt1 (6) where a, b, and c are coefficients, and the units of the coefficients a and c are μm −1.

[0045] Within the range of condition (2), the coefficients of conditions (1) and (6) can be determined as follows from the results of Examples 1 to 3 above. That is, condition (1) may satisfy the following condition (3a) or condition (3b): DEmin≧5.0Dt1+1.7 (3a) DEmin≧5.1Dt1+2.2 (3b) Furthermore, condition (6) may be the following condition (6a) or condition (6b): DEmax≦100Dt1 (6a) DEmax≦66.7Dt1 (6b)

[0046] The ranges of the coefficients a, b, and c may be the following condition (12): 4.9<a<5.2 1.7<b<2.4 60<c<110 (12)

[0047] 3, when the dielectric layer 13 and the electrode layer 11 are laminated to manufacture the main body 10, it is desirable to set the thickness Dt of the dielectric layer 13 and the thickness Et of the electrode layer 11 at the connection boundary 18 so that the ratio DE therebetween is at least a minimum value (first value) DEmin. The first value DEmin can be derived from the minimum set value Dt1 of the thickness Dt, as described above.

[0048] Furthermore, in the capacitor 1, it is desirable that the thickness Et of the electrode layer 11 at the connection boundary 18 relative to the thickness Dt of the dielectric layer 13 satisfy the following condition (7): Et≦Dt / DEmin (7)

[0049] On the other hand, when focusing on the thickness Dt of the dielectric layer 13 at the connection boundary 18, it is desirable that the thickness Et of the electrode layer 11 satisfy the following condition (8): Dt≧DEmin×Et (8)

[0050] Furthermore, based on the above examples, it is believed that a capacitor 1 with excellent connection characteristics under the above conditions can be provided even if the electrode layer 11 contains at least one of zinc, copper, gold, silver, or an alloy containing these metals in addition to aluminum. Furthermore, the electrode layer 11 may include heavy edge portions 16 and dummy edge portions 17, in which the connection boundary 18 with the external electrode 20 is thicker than the internal electrode portion 15, as in this example, or may not include these. Furthermore, the heavy edge portions 16 and dummy edge portions 17 may contain aluminum, zinc, or an alloy thereof. Furthermore, the dielectric layer 13 may or may not contain a thermosetting resin. Furthermore, the metallikon layer 21 is not limited to zinc or aluminum, but may also be copper or an alloy containing zinc or aluminum, such as brass.

[0051] Furthermore, the value ED (ED = Etmax / Dt), which is the ratio of the thickness Dt of the dielectric layer 13 to the upper limit Etmax of the thickness of the electrode layer 11, is the maximum value EDmax of the ratio ED. Focusing on this value, it has been found that there is a correlation expressed by a linear function with the maximum value (maximum set value) Etmax (Et1) of the thickness Et of the electrode layer 11. Focusing on this value ED, within the range of (2) above, the range in which the connection characteristics are good can be expressed by the following condition (9). Note that EDmax is expressed by condition (10), and since Etmin is constant, it is desirable that EDmin satisfy condition (11). EDmin≦Et / Dt≦EDmax (9) EDmax≦d×Et1+e (10) EDmin≧f×Et1 (11) where d, e, and f are coefficients, and the units of the coefficients d and f are μm-1.

[0052] From the results of Example 1 shown in FIGS. 7(c) and (d), the results of Example 2 shown in FIGS. 10(c) and (d), and the results of Example 3 shown in FIGS. 13(c) and (d), it can be seen that condition (10) may be the following condition (10a) or condition (10b): EDmax≦−3.0Et1+0.6 (10a) EDmax≦−2.3Et1+0.5 (10b) Furthermore, condition (11) may be the following condition (11a) or condition (11b): EDmin≧0.007Et1 (11a) EDmin≧0.01Et1 (11b)

[0053] The ranges of the coefficients d, e, and f may satisfy the following condition (13): −3.0<d<−2.2, 0.4<e<0.6, 0.006<f<0.02 (13).

[0054] Therefore, when manufacturing the main body 10 by stacking the dielectric layer 13 and the electrode layer 11 in step 41 of the manufacturing method 40 shown in Figure 3, the thickness Et of the electrode layer 11 and the thickness Dt of the dielectric layer 13 at the connection boundary 18 may be set so that the ratio ED between them does not exceed the maximum value EDmax.

[0055] In multilayer capacitors, such as film capacitors and thin-film polymer multilayer capacitors, metallicon is the only established method for connecting the laminate 7 of the main body 10 to the external electrodes 20, and it has not yet been commercialized. This is because, at present, any method other than metallicon cannot ensure the mechanical strength required for a capacitor. Film capacitors sometimes employ heavy-edge technology to improve voltage resistance and reduce the connection resistance between the laminate and the metallicon external electrodes. In conventional film capacitors, the dielectric resin layer is thicker than 1.5 μm, and the film is offset, making it easy to connect with metallicon even if the metal layer in the heavy-edge area is thick. On the other hand, in thin-film polymer multilayer capacitors 1 that include a thin-film dielectric layer 13, the dielectric resin layer 13 is thinner than 1.5 μm, with most products being thinner than 1.0 μm. For this reason, when the connection characteristics were checked in several examples, it was found that if the thickness of the metal layer in the heavy edge portion 16 (electrode layer 11 at the connection boundary 18) was too thick, connection with the metallikon layer 21 of the external electrode 20 could not be made or the connection resistance would be high. Also, in the case of a laminate in which the mother element (main body) 10 is integrated, as in the thin-film polymer laminate type capacitor 1, it is not possible to shift the layers of the connection portion as in conventional film capacitors, and therefore it is difficult to improve the connection characteristics by such a method.

[0056] In contrast to this, in the present invention, as described above, it has been discovered that by appropriately controlling the thickness Et of the electrode layer 11 at the connection boundary 18 relative to the thickness Dt of the dielectric layer 13, it is possible to provide a capacitor 1 that has good electrical and mechanical connection with the metallikon layer 21 even in a thin-film polymer multilayer capacitor in which the thickness of the dielectric layer 13 is thinner than 1.5 μm.

[0057] It should be noted that, although particular embodiments of the present invention have been described above, various other embodiments and modifications may be devised by those skilled in the art without departing from the scope and spirit of the present invention, and such other embodiments and modifications are within the scope of the following claims, which define the present invention.

Claims

1. A capacitor having a main body in which dielectric layers and electrode layers are alternately laminated, and an external electrode connected to at least a part of the main body by metallikon, each of the dielectric layers has a thickness Dt at a connection boundary between the main body portion and the external electrode; A capacitor, wherein each of the electrode layers includes a thickness Et at the connection boundary, and a ratio of the thickness Dt to the thickness Et and a first value DEmin satisfies the following condition with respect to a minimum set value Dt1 of the thickness Dt. Dt / Et≧DEmin DEmin≧a×Dt1+b 0.1μm≦Dt1≦Dt≦1.5μm 4.9<a<5.2 1.7<b<2.4 where a and b are coefficients.

2. In claim 1, A capacitor, wherein the first value DEmin satisfies the following condition: DEmin≧5.0Dt1+1.7

3. In claim 1, A capacitor, wherein the first value DEmin satisfies the following condition: DEmin≧5.1Dt1+2.2

4. In claim 1, The capacitor, wherein the electrode layer contains at least one of aluminum, zinc, copper, gold, silver, or an alloy containing any of these.

5. In claim 1, The electrode layer includes a heavy edge portion where the portion connecting with the external electrode is thicker than the internal electrode portion.

6. In claim 5, A capacitor, wherein the heavy edge portion includes aluminum, zinc, or an alloy thereof.

7. In claim 1, The electrode layer includes a dummy edge portion where a connection portion with the external electrode is separated from the internal electrode portion.

8. In claim 1, The capacitor, wherein the dielectric layer comprises a thermosetting resin.

9. In claim 1, The capacitor, wherein the external electrodes contain at least one of aluminum, zinc, copper, or an alloy containing any of these.

10. 1. A method for manufacturing a capacitor having a body portion in which dielectric layers and electrode layers are alternately stacked, and external electrodes connected to at least a portion of the body portion, comprising: A method for manufacturing a capacitor, comprising stacking the dielectric layers and the electrode layers so that a ratio of a thickness Dt of each of the dielectric layers at a connection boundary with the external electrode of the main body portion to a thickness Et of each of the electrode layers at the connection boundary, and a first value DEmin, satisfies the following condition with respect to a minimum set value Dt1 of the thickness Dt. Dt / Et≧DEmin DEmin≧a×Dt1+b 0.1μm≦Dt1≦Dt≦1.5μm 4.9<a<5.2 1.7<b<2.4 where a and b are coefficients.

11. In claim 1, Each of the electrode layers has an internal thickness of less than 0.01 μm.

12. In claim 10, Each of the electrode layers has an internal thickness of less than 0.01 μm.

13. In claim 1, A capacitor, wherein the value Dt1 of the thickness Dt satisfies the following condition: 0.1μm≦Dt1≦Dt≦0.5μm

14. In claim 10, A method for manufacturing a capacitor, wherein the value Dt1 of the thickness Dt satisfies the following condition. 0.1μm≦Dt1≦Dt≦0.5μm