Capacitors and circuit board molds using them

Abstract

This invention relates to a capacitor and a circuit board molded body using the same, and aims to avoid a decrease in mounting density on the circuit board and inefficiencies in resin molding work. [Solution] Noticing that strong pressure from the molded resin is applied to the first top surface 6 of the main body case 2 during resin molding, a cap 3 is placed over the surface of the first top surface 6 of the main body case 2. This cap 3 prevents damage to the capacitor 1 due to resin molding. Furthermore, the cap 3 is placed over the surface of the first top surface 6 of the main body case 2 in advance. This eliminates the need to place the cap 3 during the molding process, improving the efficiency of the molding process. In addition, the thickness of the second side surface 16 of the cap 3 is made thinner than the thickness of the second top surface 15 of the cap 3. This suppresses the need to increase the diameter of the capacitor 1 itself. As a result, a decrease in mounting density on the circuit board and inefficiency in the resin molding process can be avoided.

Description

Technical Field

[0001] The present invention relates to a capacitor and a circuit board molded body using the same.

Background Art

[0002] When covering a circuit board on which a capacitor is mounted with a molding resin, in order to prevent the capacitor from being damaged by the pressure of the flowing molding resin, a structure has been proposed in which the capacitor after being mounted on the circuit board is completely covered with a case (for a similar one, for example, Patent Document 1 below). Specifically, a case provided with a gel member inside is completely covered on the capacitor, and when pressure by the molding resin is applied, the case is pushed and the gel substance flows out from the opening of the case.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The problem in the above prior art is that since the case houses the gel member interposed between the outer periphery of the capacitor, the case itself has a large diameter and may not be able to be mounted on the capacitor on the circuit board.

[0005] That is, on the circuit board, many components including the capacitor are mounted in a close state to increase the mounting density, so there are many cases where there is no space to cover the capacitor after mounting with the above large-diameter case.

[0006] Therefore, if the circuit board design is to ensure a large space around the capacitor on the circuit board so that the large-diameter case can be easily placed over the capacitor after it has been mounted, the circuit board will have to be larger, which presents a challenge.

[0007] Furthermore, when capacitors encased in large-diameter cases are placed on a circuit board, the flow resistance of the molding resin increases, which can affect the efficiency of the resin molding process.

[0008] The present invention aims to avoid a decrease in mounting density on circuit boards and inefficiencies in resin molding work. [Means for solving the problem]

[0009] To achieve this objective, the capacitor of the present invention comprises a cylindrical main body case having a first opening at one end, a first top surface on the portion opposite to the first opening, and a first side surface connecting the first top surface and the first opening; a capacitor element housed within the main body case; a sealing body mounted within the main body case on the side of the capacitor element closer to the first opening; a base plate provided outside the first opening of the main body case; a connection terminal positioned on the side of the base plate opposite to the capacitor element, with a portion of the terminal electrically connected to the capacitor element via a conductive portion penetrating the sealing body; and a cap fitted over the surface side of the first top surface of the main body case. The cap is cylindrical, having a second opening on the first top surface side of the main body case, a second top surface on the portion opposite to the second opening, and a second side surface connecting the second top surface and the second opening. The back side of the second top surface is fixed to the surface side of the first top surface of the main body case with a thermo-softening adhesive. The thickness of the second side panel is thinner than the thickness of the second top panel.

[0010] In the capacitor configuration described above, the second radius of curvature, which is the radius of curvature of the second corner portion where the second top surface and the second side portion of the cap meet, is larger than the first radius of curvature, which is the radius of curvature of the first corner portion where the first top surface and the first side portion of the main case meet. The front surface of the first corner portion of the cap is in contact with the back surface of the second corner portion.

[0011] The capacitor with the above configuration has a cap with an obtuse-angled inclined surface at the end of the cap on the second opening side, extending from the back side end of the cap to the front side end.

[0012] The capacitor in the above configuration has a pressure receiving plate placed on the side of the sealing body opposite to the capacitor element.

[0013] The circuit board molded body has a configuration in which one of the above-described capacitors mounted on the board is covered with molding resin on the board, at least around the capacitor. [Effects of the Invention]

[0014] As described above, the capacitor of the present invention has a cap placed over the surface of the first top surface of the main body case. This cap is fixed to the surface of the first top surface of the main body case with a heat-softening adhesive. Furthermore, the thickness of the second side of the cap is thinner than the thickness of the second top surface of the cap. This avoids a decrease in mounting density on the circuit board and inefficiencies in resin molding work.

[0015] In other words, the present invention focuses on the fact that strong pressure from the molded resin is applied to the first top surface of the main body case during resin molding, and therefore places a cap on the surface side of the first top surface of the main body case. This cap prevents damage to the capacitor due to resin molding.

[0016] In addition, since the cap is pre - placed on the surface side of the first top surface of the main body case, during the molding operation, the operation of placing the cap is not required, and the efficiency of the molding operation can be improved. Furthermore, in the present invention, since the plate thickness of the second side surface of the cap is made thinner than the plate thickness of the second top surface of the cap, it is possible to suppress the increase in the outer diameter of the capacitor itself. As a result, it is possible to avoid a decrease in the mounting density on the circuit board and inefficiency in the resin molding operation.

Brief Description of the Drawings

[0017] [Figure 1] Front view of the capacitor according to an embodiment of the present invention [Figure 2] Exploded front view showing a part of the capacitor in cross - section [Figure 3] Cross - sectional view showing the manufacturing method of the capacitor [Figure 4] Enlarged cross - sectional view of a part of the capacitor [Figure 5] Enlarged cross - sectional view of a part of the capacitor [Figure 6] Plan view of the capacitor

Mode for Carrying Out the Invention

[0018] (Embodiment 1) As shown in FIGS. 1 and 2, the capacitor 1 of the present embodiment includes a main body case 2, a cap 3 placed on the main body case 2, and a seat plate 4 provided on the opposite side of the cap 3.

[0019] The main body case 2 is made of aluminum and has a cylindrical shape as shown in FIG. 3, with a first opening 5 on one end side, a first top surface 6 on the part facing the first opening 5, and a first side surface 7 connecting the first top surface 6 and the first opening 5 side.

[0020] A capacitor element 8 is housed inside the main body case 2.

[0021] A rubber sealing body 9 is provided inside the main body case 2 on the side of the first opening 5 that is closer to the capacitor element 8, and its outer circumference is fixed by the constricted portion 10 of the main body case 2.

[0022] A pressure receiving plate 11 made of resin is positioned on the side of the sealing body 9 opposite to the capacitor element 8.

[0023] In this state, the first opening 5 of the main case 2 becomes a bent portion 12 that is folded inward, and by having the bent portion 12 cover the outer periphery of the pressure receiving plate 11 and the sealing body 9, the pressure receiving plate 11 and the sealing body 9 are prevented from coming out of the main case 2.

[0024] The capacitor element 8 is provided with two connection terminals 13, which penetrate the sealing body 9, the pressure receiving plate 11, and the base plate 4, and are bent to the left and right on the side of the base plate 4 opposite to the capacitor element 8. In this embodiment, the middle part of the two connection terminals 13 (the part that penetrates the sealing body 9 and the pressure receiving plate 11) is a conductive part.

[0025] The two connector terminals 13 shown in Figure 3 are of different lengths to distinguish between the positive and negative sides, but their lengths will be adjusted (cut) after they are attached to the base plate 4.

[0026] As shown in Figure 6, the two connection terminals 13 extend beyond the outer circumference of the base plate 4 in a plan view, allowing the soldering condition to be checked.

[0027] The following describes the features of this embodiment.

[0028] (1) The cap 3 is made of aluminum and, as shown in Figures 2 to 5, is cylindrical in shape with a second opening 14 on the first top surface 6 side of the main body case 2, a second top surface 15 on the part opposite to the second opening 14, and a second side surface 16 connecting the second top surface 15 to the side of the second opening 14. The back side of the second top surface 15 is fixed to the front side of the first top surface 6 of the main body case 2 with a thermoplastic adhesive 17. The thermoplastic adhesive 17 can be made of a resin whose glass transition temperature is lower than or equal to the reflow temperature (250°C) at the time of mounting. Examples of thermoplastic adhesives 17 include epoxy resin, silicone resin, polycarbonate resin, PET resin, and polyamide resin. A thermoplastic resin is preferable because it softens more easily with heat.

[0029] (2) The thickness of the second side surface 16 is thinner than that of the second top surface 15, as shown in Figure 5. Therefore, even when the cap 3 is placed over the main case 2, the increase in the outer diameter of the capacitor 1 can be suppressed, and as a result, as shown in Figure 6, the condition of the connection terminals 13 on the outer circumference of the cap 3 can be checked in a plan view of the capacitor 1, and the quality of the soldering can be easily checked.

[0030] (3) As shown in Figure 5, the radius of curvature of the second corner 19 portion where the second top surface 15 and the second side surface 16 of the cap 3 meet is larger than the radius of curvature of the first corner 18 portion where the first top surface 6 and the first side surface 7 of the main case 2 meet (first radius of curvature), and the front surface of the first corner 18 portion of the main case 2 is in contact with the back surface of the second corner 19 portion of the cap 3.

[0031] (4) As shown in Figure 4, the end of the cap 3 on the side of the second opening 14 is provided with an obtuse angled inclined surface 20 extending from the back side end to the front side end.

[0032] The assembly of the main case 2 and cap 3 in the above configuration will now be explained.

[0033] For example, as shown in Figure 3, first, the cap 3 is placed with its second opening 14 facing upwards. Next, adhesive 17 is dripped from the dispenser onto the center of the back side of the second top surface 15. Then, as shown in Figure 3, the main body case 2 is inserted from the first top surface 6 side of the main body case 2 into the second opening 14 of the cap 3.

[0034] At this time, as described in feature point (4) above, in this embodiment, the end of the cap 3 on the second opening 14 side has an obtuse angled inclined surface 20 from the back side end to the front side end, making it easier to insert the main body case 2 into the cap 3.

[0035] In other words, by providing an obtuse-angled inclined surface 20, the second opening 14 of the cap 3 is widened, making it easier to insert the main body case 2 into the cap 3.

[0036] Furthermore, in this embodiment, as described in feature point (3), the radius of curvature of the second corner 19 portion of the cap 3 (second radius of curvature) is made larger than the radius of curvature of the first corner 18 portion of the main body case 2 (first radius of curvature), and the front surface of the first corner 18 portion of the main body case 2 is brought into contact with the back surface of the second corner 19 portion of the cap 3.

[0037] Therefore, as shown in Figure 5, a gap 21 is formed between the back side of the second top surface 15 of the cap 3 and the front side of the first top surface 6 of the main body case 2, and the main body case 2 and the cap 3 are attached and fixed together by the heat-softening adhesive 17 present in this gap 21.

[0038] This is extremely important because when capacitor 1 is mounted to the circuit board using reflow solder, the solder atmosphere causes the inside of the capacitor 1's main case 2 to reach a high temperature, for example, 250°C, and the main case 1 also expands.

[0039] In this embodiment, a pressure receiving plate 11 made of resin is provided on the side of the sealing body 9 opposite to the capacitor element 8, so that it receives expansion pressure and the first top surface 6 of the main body case 2 bulges outwards from the main body case 2.

[0040] At this time, a gap 21 is formed between the main body case 2 and the cap 3 as described above, and since the adhesive 17 present in this gap 21 is heat-softening, the adhesive 17 softens at high temperatures, and as a result, the first top surface 6 of the main body case 2 can expand outward appropriately, preventing damage to the capacitor 1.

[0041] Next, the circuit board with capacitor 1 mounted on it is placed inside the mold, and the molding resin is poured in.

[0042] At this time, the pressure of the molding resin flowing inside the mold is high, and it is necessary to reduce the flow resistance of the molding resin inside the mold as much as possible.

[0043] In this embodiment, as described in feature point (2) above, the thickness of the second side surface 16 of the cap 3 is made thinner than the thickness of the second top surface 15.

[0044] In other words, even when the cap 3 is placed over the main case 2, the increase in the outer diameter of the capacitor 1 is suppressed, so the flow resistance of the molded resin inside the mold does not increase easily, resulting in better work efficiency.

[0045] Furthermore, if the thickness of the second side surface 16 of the cap 3 is made thinner than the thickness of the second top surface 15, the second side surface 16 will bend more easily when the flowing mold resin comes into contact with it, which also contributes to reducing the flow resistance of the mold resin.

[0046] In this case, as described in feature point (4) above, in this embodiment, the end of the cap 3 on the second opening 14 side has an obtuse angled inclined surface 20 from the back side end to the front side end, so that the inclined surface 20 is less likely to come into contact with the main body case 2, which in turn makes the second side surface 16 of the cap 3 more flexible, and this also reduces the flow resistance of the molded resin.

[0047] In the above embodiment, adhesive 17 was provided inside the cap 3 as shown in Figure 3 to bond and fix it to the main body case 2. However, conversely, the first top surface 6 of the main body case 2 may be positioned with the top surface 6 facing upwards, adhesive 17 may be provided on the surface side of the first top surface 6, the cap 3 may be lowered towards the main body case 2 with the second opening 14 facing downwards, and the two may be bonded and fixed together with adhesive 17.

[0048] As described above, this embodiment focuses on the fact that during resin molding, strong pressure from the molded resin is applied to the first top surface 6 of the main body case 2. Therefore, a cap 3 is placed over the surface of the first top surface 6 of the main body case 2. This cap 3 prevents damage to the capacitor 1 caused by resin molding.

[0049] Furthermore, since the cap 3 is already placed on the surface of the first top surface 6 of the main case 2, the process of placing the cap 3 during the molding process is unnecessary, thus improving the efficiency of the molding process.

[0050] Furthermore, since the thickness of the second side surface 16 of the cap 3 is made thinner than the thickness of the second top surface 15 of the cap 3, it is possible to suppress the increase in diameter of the capacitor 1 itself, and as a result, a decrease in mounting density on the circuit board and inefficiency in resin molding work can be avoided. [Explanation of Symbols]

[0051] 1 Capacitor 2. Main unit case 3 caps 4 Seat board 5. First opening 6. First top surface 7. First Aspect 8 Capacitor elements 9 Sealing body 10 Aperture section 11 Pressure receiving plate 12 Folding section 13 Connection terminals 14 Seat board 15. Second top surface 16. Second Aspect 17 Adhesives 18. Corner 1 19. Second Corner 20 Slope 21 gaps

Claims

1. A cylindrical main body case having a first opening at one end, a first top surface on the portion opposite to the first opening, and a first side surface connecting the first top surface to the side of the first opening, The capacitor element housed inside this main case, A sealing body is installed inside the main body case, on the side of the first opening that is closer to the capacitor element, A seat plate provided outside the first opening of the main body case, This seat plate is positioned on the side opposite to the capacitor element, and a portion of it is electrically connected to the capacitor element via a conductive portion that penetrates the sealing body, and a connection terminal is provided. The main body case comprises a cap placed over the surface of the first top surface, The cap is cylindrical in shape, having a second opening on the first top surface side of the main body case, a second top surface on the portion opposite to the second opening, and a second side surface connecting the second top surface to the second opening side. The underside of the second top surface is fixed to the front surface of the first top surface of the main body case with a heat-softening adhesive. A capacitor in which the thickness of the second side plate is thinner than the thickness of the second top plate.

2. The second radius of curvature, which is the radius of curvature of the second corner portion of the cap where the second top surface and the second side portion meet, is made larger than the first radius of curvature, which is the radius of curvature of the first corner portion of the main body case where the first top surface and the first side portion meet. The capacitor according to claim 1, wherein the front surface of the first corner portion of the cap is in contact with the back surface of the second corner portion of the cap.

3. The capacitor according to claim 2, wherein the end of the cap on the second opening side is provided with an obtuse angled inclined surface extending from the back side end of the cap to the front side end.

4. The capacitor according to claim 3, wherein a pressure receiving plate is arranged on the side of the sealing body opposite to the capacitor element.

5. A circuit board mold in which a capacitor according to any one of claims 1 to 4, mounted on a substrate, is covered with a molding resin on the substrate, at least around the capacitor.

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