connector

Abstract

To provide a connector which can suppress warpage of a housing.SOLUTION: A housing 10 has: a bottom wall 11 which has a cylindrical shape opened forward, and is mounted on a circuit board 90; a top wall 15 which faces the bottom wall 11; and a back wall 19 which vertically connects rear end portions of the bottom wall 11 and the top wall 15 to each other. A terminal fitting 5 has: a terminal connection part 8 which has a shape penetrating the back wall 19 in a front-to-rear direction, and is disposed inside the housing 10; and a board connection part 9 which is disposed outside the housing. The top wall 15 has a volume larger than that of the bottom wall 11 and is formed thicker in a vertical direction as a whole. A terminal protrusion surface 23 where the board connection part 9 protrudes on a rear face of the back wall 19 is disposed forward of a rear face of the top wall 15.SELECTED DRAWING: Figure 3

Description

【Technical Field】 【0001】 This disclosure relates to a connector. 【Background Art】 【0002】 The connector disclosed in Patent Document 1 is a board connector to be mounted on a circuit board, and includes a terminal fitting and a resin housing (connector housing) on which the terminal fitting is mounted. The housing has a cylindrical shape that opens forward, and at the rear end, has a back wall (terminal holding portion) that stands on the surface of the circuit board. The terminal fitting has a terminal connection portion (connector-side connection portion) disposed inside the housing and penetrating the back wall, and a board connection portion (board-side connection portion) disposed outside the housing. The rear end portion of the board connection portion is disposed along the surface of the circuit board and is soldered and connected to the conductive portion (conductive path) of the circuit board. This type of board connector is also disclosed in Patent Documents 2-5. 【Prior Art Documents】 【Patent Documents】 【0003】 【Patent Document 1】 Japanese Unexamined Patent Application Publication No. 2005-166492 【Patent Document 2】 Japanese Unexamined Patent Application Publication No. 2010-238508 【Patent Document 3】 Japanese Unexamined Patent Application Publication No. 2012-243676 【Patent Document 4】 Japanese Unexamined Patent Application Publication No. 2015-210936 【Patent Document 5】 Japanese Unexamined Patent Application Publication No. 2021-114378 【Summary of the Invention】 【Problems to be Solved by the Invention】 【0004】 In the connector described above, the terminal fittings that connect to the circuit board are soldered to the conductive parts of the circuit board via a reflow process. In this case, the connector may deform due to the heating during the reflow process, causing the housing and the circuit board to warp. Because there is a difference in the coefficient of thermal expansion between the housing and the circuit board, if the housing warps, the terminal fittings that connect to the circuit board may lift away from the conductive parts of the circuit board, which could lead to a decrease in connection reliability. 【0005】 Therefore, the object of this disclosure is to provide a connector capable of suppressing warping of the housing. [Means for solving the problem] 【0006】 The connector of this disclosure comprises a terminal fitting and a resin housing on which the terminal fitting is mounted, wherein the housing has a cylindrical shape opening forward and has a bottom wall that rests on a circuit board, a top wall opposite the bottom wall, and a rear wall that connects the rear ends of the bottom wall and the top wall in the vertical direction, the terminal fitting has a shape that penetrates the rear wall in the front-rear direction and has a terminal connection portion disposed inside the housing and a board connection portion disposed outside the housing, the top wall has a larger volume than the bottom wall and is formed to be thicker overall in the vertical direction, and the terminal protruding surface on the rear surface of the rear wall from which the board connection portion protrudes is located in front of the rear surface of the top wall. [Effects of the Invention] 【0007】 According to this disclosure, it is possible to provide a connector that can suppress warping of the connector housing. [Brief explanation of the drawing] 【0008】 [Figure 1] Figure 1 is a perspective view of the connector in Embodiment 1 of this disclosure. [Figure 2] Figure 2 is a rear view of the connector. [Figure 3] Figure 3 is a cross-sectional view of AA in Figure 2. [Figure 4]Figure 4 is a cross-sectional view of BB in Figure 2. [Figure 5] Figure 5 is a side view of the connector. [Figure 6] Figure 6 is a plan view of the connector. [Figure 7] Figure 7 is a front view of the connector. [Modes for carrying out the invention] 【0009】 [Description of Embodiments in this Disclosure] First, the embodiments of this disclosure will be listed and described. The connector disclosed herein is (1) The device comprises a terminal fitting and a resin housing on which the terminal fitting is mounted, the housing being cylindrical in shape with an opening to the front and having a bottom wall that rests on a circuit board, a top wall opposite the bottom wall, and a rear wall connecting the rear ends of the bottom wall and the top wall in the vertical direction, the terminal fitting being shaped to penetrate the rear wall in the front-rear direction and having a terminal connection portion located inside the housing and a circuit board connection portion located outside the housing, the top wall being larger in volume than the bottom wall and thicker overall in the vertical direction, and the terminal projection surface on the rear surface of the rear wall from which the circuit board connection portion protrudes being located is positioned in front of the rear surface of the top wall. 【0010】 The connector with the above configuration has a thicker top wall with a larger volume (amount of resin) than the bottom wall, making the housing less prone to warping in high-temperature environments such as reflow soldering. In particular, increasing the volume on the rear side of the top wall effectively suppresses housing warping. Furthermore, since the terminal protrusion surface on the back wall is positioned in front of the rear surface of the top wall, there is no need to move the connection position of the board connection part to the circuit board backward in accordance with the rear surface of the top wall, thereby reducing the area occupied by the connector on the circuit board. 【0011】 (2) In the connector according to (1) above, it is preferable that a stepped surface extending in the left - right direction is formed between the terminal protruding surface of the back wall and the rear - surface side of the top wall. The connector with the above - described configuration can more effectively suppress the warping of the housing by the stepped surface. 【0012】 (3) In the connector according to (1) or (2) above, the housing includes a flange portion that protrudes outward from the outer surface of the top wall. The connector with the above - described configuration can more effectively suppress the warping of the housing by the flange portion. The flange portion can be used as an attachment structure to a case or the like. 【0013】 (4) In the connector according to any one of (1) to (3) above, the top wall has a locking portion that holds a mating housing disposed inside the housing in a fitted state. The locking portion projects in the left - right direction at the front end of the top wall. The top wall has a plurality of die - cutting holes disposed at positions facing each of the plurality of locking portions, and partition walls that partition between the plurality of die - cutting holes. The partition walls preferably extend in the front - rear direction while overlapping the top wall, and the front end portions are connected to each of the plurality of locking portions. The connector with the above - described configuration can more effectively suppress the warping of the housing by the partition walls. 【0014】 (5) In the connector according to any one of (1) to (4) above, it is preferable that a gate trace corresponding to an injection port for injecting molding resin is formed on at least one of the top surface of the rear end portion of the top wall and the bottom surface of the rear end portion of the bottom wall. According to the above - described configuration, the orientation (fiber orientation) of the resin constituting the housing can be directed in the up - down direction. Therefore, in a high - temperature environment such as reflow, the housing is less likely to deform upward, and the state in which the board - connection portion of the terminal fitting is connected to the circuit board can be properly maintained. The occurrence of warping due to anisotropic shrinkage of the housing can be suppressed by the thick - wall structure of the top wall or the like. 【0015】 [Details of Embodiments of the Present Disclosure] Specific examples of the present disclosure will be described below with reference to the drawings. Note that the present invention is not limited to this exemplification, and is shown by the claims, and is intended to include all modifications within the meaning and scope equivalent to the claims. 【0016】 [Embodiment 1] The connector 3 of Embodiment 1 of the present disclosure includes a plurality of terminal fittings 5 and a housing 10 for mounting each terminal fitting 5. The connector 3 is a connector for a circuit board to be mounted on a circuit board 90. The housing 10 is capable of being fitted to a mating housing 50. In the following description, regarding the front-rear direction, the surface side where the housing 10 is fitted to the mating housing 50 is taken as the front side. The left side in FIG. 3 is the front side. The up-down direction is based on the up-down direction in FIGS. 1-5. The left-right direction is based on the left-right direction in FIG. 2. 【0017】 In FIGS. 1, 3-6, "front side" is represented by "F", in FIGS. 1-5, 7, "upper side" is represented by "U", and in FIGS. 1, 2, 6, 7, "right side" is represented by "R". The up-down direction does not necessarily coincide with the gravitational direction in the state where the connector 3 is mounted on a vehicle or the like not shown in the drawings. 【0018】 The housing 10 will be described. As shown in FIGS. 1, 3, and 4, the housing 10 is made of synthetic resin. In the case of Embodiment 1, the housing 10 is formed of an anisotropic material such as liquid crystal polymer (LCP). The housing 10 has an elongated flat rectangular tubular hood portion 20 in the left-right direction. As shown in FIG. 4, the mating housing 50 can be fitted into the hood portion 20. 【0019】 The hood portion 20 has a flat bottom wall 11. The lower surface of the bottom wall 11 is the bottom surface to be placed on the circuit board 90. The hood portion 20 has a pair of plate-like side walls 13 rising from the left and right ends of the bottom wall 11. The hood portion 20 has a plate-like top wall 15 facing parallel to the bottom wall 11 above the bottom wall 11. The upper surface of the top wall 15 is a flat top surface along the left-right direction and the front-rear direction. The hood section 20 is provided with a rear wall 19 that connects the rear ends of the bottom wall 11 and the top wall 15 in the vertical direction. In this specification, "rear end" refers to the rear end and is a concept that includes the portion located in front of the rearmost surface of the hood section 20. The rear wall 19 is a vertical wall with thickness in the front-rear direction. The rear surface of the hood section 20 is closed by the rear wall 19. The hood section 20 is open in front of the rear wall 19. The lower edges of the pair of side walls 13 are connected perpendicularly to the left and right ends of the bottom wall 11. The upper edges of the pair of side walls 13 are connected perpendicularly to the left and right ends of the top wall 15. The rear end edges of the pair of side walls 13 are connected perpendicularly to the left and right ends of the rear wall 19. 【0020】 As shown in Figures 2 and 4, the hood portion 20 has a pair of claw-shaped locking portions 17 on the top wall 15 that protrude inward from the hood portion 20. Each locking portion 17 is arranged symmetrically in pairs on both sides of the left and right central portion of the top wall 15 (the partition wall 21, which will be described later). The locking portion 17 has an inclined surface 18 that extends diagonally downward inward from the front end of the top wall 15. The rear surface of the locking portion 17 is a locking surface 17S that intersects perpendicularly or at an acute angle with the inner lower surface of the top wall 15 (the surface facing downward inside the top wall 15). 【0021】 The top wall 15 has a die-cut hole 16 at its rear end facing the locking surface 17S, which is open to the rear. The die-cut holes 16 are arranged in pairs in the left-right direction to correspond to the locking portion 17. The die-cut holes 16 have a rectangular shape when viewed from the rear and are formed when the mold (not shown) that forms the locking surface 17S is withdrawn. The upper end of the back wall 19 faces the die-cut hole 16. 【0022】 The top wall 15 has a pair of left and right die-cut holes 16 separated by a partition wall 21 in the left and right center of the rear end. to have The bulkhead 21 extends forward from its rear end, which is sandwiched between each die-cut hole 16, and continues along the inner lower surface of the top wall 15. The front end of the bulkhead 21 is part of the opening end of the hood section 20, and its left and right ends are connected to the corresponding locking sections 17. 【0023】 The rear surface 15S of the top wall 15 is arranged along the vertical and horizontal directions. Each die-cut hole 16 opens into the rear surface 15S of the top wall 15. The rear surface of the partition wall 21 is part of the rear surface 15S of the top wall 15. The rear wall 19 has a terminal projection surface 23 on its rear surface. Each terminal fitting 5 protrudes from the terminal projection surface 23 to the outside of the housing 10. The terminal projection surface 23 is positioned to be recessed forward of the rear surface 15S of the top wall 15. A downward-facing stepped surface 25 extending in the horizontal direction is formed between the terminal projection surface 23 of the rear wall 19 and the rear surface 15S of the top wall 15. 【0024】 The back wall 19 has multiple terminal housing holes 31 that penetrate in the front-to-back direction for inserting each terminal fitting 5. Each terminal housing hole 31 is arranged in multiple rows in the vertical direction and in multiple columns in the left-to-right direction, and opens in alignment with the terminal protruding surface 23. As shown in Figure 4, each terminal housing hole 31 has a tapered portion 33 that slopes so as to narrow in diameter toward the front from the terminal protruding surface 23. 【0025】 The housing 10 has a gate mark 35 in the left-right center of the upper surface of the rear end of the top wall 15. The gate mark 35 is circular and concave, and is formed at a position corresponding to the injection port for injecting resin (molten resin) to mold the housing 10. The diameter of the gate mark 35 is smaller than the left-right width of the partition wall 21. The housing 10 has a continuous resin section 37 that extends continuously downward from the gate mark 35. The continuous resin section 37 is a resin portion that penetrates (crosses) the top wall 15, the rear wall 19, and the bottom wall 11 in the vertical direction. The upper surface of the continuous resin section 37 constitutes the gate mark 35 on the upper surface of the top wall 15. The continuous resin section 37 has a circular cross-sectional shape corresponding to the gate mark 35 and is continuous without distinction with the surrounding portion of the housing 10. The continuous resin section 37 forms the partition wall 21 in the top wall 15. The continuous resin section 37 forms the resin portion between each terminal housing hole 31 in the rear wall 19. The lower surface of the continuous resin section 37 forms part of the lower surface of the bottom wall 11. 【0026】 As shown in Figure 7, the top wall 15 has a reference wall 48 extending in the left-right direction. The lower surface of the reference wall 48 (the reference surface facing the inside of the hood portion 20) is a surface defined by the height position including the underlined portion in Figure 7. Each lock portion 17 is formed within the vertical thickness of the reference wall 48. The vertical thickness of the reference wall 48 is greater than the vertical thickness of the bottom wall 11 and also greater than the left-right thickness of the side wall 13 (excluding the mounting portion 52 of the fixing member 47, which will be described later). The top wall 15, including the reference wall 48, has a larger volume (amount of resin) than the bottom wall 11 and is formed to be thicker overall in the vertical direction than the bottom wall 11. The bulkhead 21 has a portion that protrudes downward from the left and right center of the reference wall 48. The top wall 15 has a pair of left and right protruding ribs 39 that protrude downward from the lower surface of the reference wall 48 on both sides of each locking portion 17. Each protruding rib 39 extends from the front to the rear of the top wall 15 parallel to the bulkhead 21, and its rear end is connected to the back wall 19. The top wall 15 has a first recess 40 between each protruding rib 39 into which the locking arm 51 of the mating housing 50, which will be described later, enters. 【0027】 The top wall 15 has a pair of second recesses 43 on each side, located near the left and right ends between the protruding rib 39 and the side wall 13, and recessed in the lower surface of the reference wall 48. Each second recess 43 extends in the front-rear direction, with its front end opening to the front surface of the top wall 15 and its rear end being closed at the rear end of the top wall 15. Each second recess 43 has a dovetail groove shape, widening in width from side to side towards the top. Ribs (not shown) of the mating housing 50 are fitted into each second recess 43. 【0028】 As shown in Figure 1, the housing 10 has a flange portion 45 on the outer circumference near the front end of the hood portion 20 that protrudes from the outer surfaces of the top wall 15 and the side wall 13. The flange portion 45 protrudes more from the side wall 13 than from the top wall 15. The flange portion 45 is plate-shaped and is positioned with its plate surface facing front to back. The flange portion 45 has mounting portions 52 integrally connected to the rear end faces of its left and right ends, each having grooves (not shown) for fixing fixing members 47, which will be described later. The flange portion 45 is attached to a case (not shown). 【0029】 The housing 10 has a pair of left and right protective walls 60 that project continuously to the rear from each side wall 13. Each protective wall 60 is plate-shaped and arranged with its plate surface facing left and right. Each protective wall 60 protects each terminal fitting 5 from both the left and right sides. The protective wall 60 has a thickened portion 61 that is wider on the left and right sides. As shown in Figure 5, a groove (not shown) is formed in the thickened portion 61 for attaching a fixing member 47, which will be described later. 【0030】 A pair of metal fixing members 47 are attached to the outer surfaces of both side walls 13 (the left and right end faces of the hood portion 20) of the hood portion 20. The bottom surface 47S of the fixing members is fixed to the circuit board 90 by soldering. The fixing members 47 have a pair of locking portions 49 that protrude in the front-rear direction. As shown in Figure 5, the locking portions 49 are attached to and fixed to the thick portion 61 and the mounting portion 52 of the protective wall 60. 【0031】 Each terminal fitting 5 is made of metal and, as shown in Figure 3, has a terminal connection portion 8 that extends in the front-rear direction and penetrates the terminal housing hole 31 in a press-fit state. The terminal connection portion 8 has a portion that protrudes into the hood portion 20 and is connected to the mating terminal 55. The terminal connection portion 8 has a portion that protrudes rearward from the terminal protruding surface 23. Each terminal fitting 5 has a substrate connection portion 9 that is connected to the rear end of the terminal connection portion 8 via a first bent portion 6 and extends downward from the first bent portion 6. The substrate connection portion 9 has a portion that extends rearward at its lower end via a second bent portion 7 and is connected to the circuit board 90 by soldering. 【0032】 As shown in Figure 4, the locking portion 17 of the housing 10 and the mating locking portion 53 of the mating housing 50 are locked together, holding the housing 10 and the mating housing 50 in a fitted state, and each terminal connection portion 8 is connected to the mating terminal 55 mounted on the mating housing 50. The rear end of the board connection portion 9 of each terminal fitting 5 is connected to the mounting surface 90A of the circuit board 90 by soldering. 【0033】 Next, the operation of the connector 3 of this embodiment 1 will be explained. The housing 10 is made by filling a mold (not shown) with molten resin, and after the molten resin has solidified, the mold is opened and the housing 10 is removed. On the upper surface of the rear end of the top wall 15 of the molded housing 10, a gate mark 35 is formed corresponding to the position where the molten resin was injected into the mold. The resin orientation (fiber orientation) of the housing 10 corresponds to the flow direction of the molten resin and is oriented in the direction of formation of the continuous resin portion 37 extending downward from the gate mark 35 and in the vertical direction parallel to the continuous resin portion 37 (see the direction of the arrow in Figure 2). For this reason, the housing 10 is less susceptible to thermal deformation in the vertical direction. 【0034】 In this embodiment 1, since the housing 10 has a continuous resin portion 37 that extends continuously from the gate mark 35, the resin orientation can be properly defined in the vertical direction without obstructing the flow of the molten resin. 【0035】 The connector 3 is mounted to the circuit board 90 by reflow soldering. Specifically, the board connection portion 9 of each terminal fitting 5 and each fixing member 47 are placed on the solder paste formed on the surface of the circuit board 90, and the solder is melted in a reflow oven (not shown). After cooling and solidifying, each fixing member 47 is soldered and fixed to the circuit board 90, and the board connection portion 9 of each terminal fitting 5 is soldered and connected to the conductive part of the circuit board 90. 【0036】 Generally, there is a concern that the housing will deform due to thermal expansion upward, away from the circuit board 90, when heated in a reflow oven. However, in this embodiment 1, as described above, since the resin orientation of the housing 10 is oriented in the vertical direction, deformation of the housing 10 in the vertical direction can be suppressed even in high-temperature environments such as inside a reflow oven. 【0037】 Furthermore, generally, when the housing 10 is heated in a reflow oven, there is a concern that the left and right central parts of the housing 10 may deform and curve upward. If such warping occurs in the housing, each terminal fitting 5 will be displaced upward, and in particular, the board connection portion 9 of the upper terminal fitting 5 may separate from the conductive part of the circuit board 90, potentially leading to a poor connection. However, in this embodiment 1, as mentioned above, the top wall 15 is thicker in the vertical direction than the bottom wall 11 as a whole, and has a larger volume than the bottom wall 11. Therefore, the upper end of the housing 10 is less likely to deform in the left and right direction, and warping of the housing 10 can be suppressed. In addition, even when the connector 3 is mounted on a vehicle or the like after reflow, the thick structure of the top wall 15 can suppress warping of the housing 10. In particular, since a stepped surface 25 extending in the left and right direction is formed between the rear surface of the top wall 15 and the terminal protruding surface 23, warping of the housing 10 can be effectively suppressed. 【0038】 The flange portion 45 is positioned to protrude from the outer surfaces of the top wall 15 and the side wall 13, thereby reinforcing the top wall 15 and the side wall 13 from the outside. The flange portion 45 more reliably suppresses warping of the housing 10. In addition, since the partition wall 21 extends in the front-rear direction and its front end is connected to each of the multiple locking portions 17, the top wall 15 becomes a structure that is less prone to deformation. 【0039】 The terminal protruding surface 23 is positioned in front of the rear surface of the top wall 15, which makes the top wall 15 thicker in the front-to-back direction. This also suppresses warping of the housing 10 in the front-to-back direction. Furthermore, with this configuration, the position where the terminal connection portion 8 of each terminal fitting 5 protrudes from the terminal protruding surface 23 is also positioned in front of the rear surface of the top wall 15 by the amount of the stepped surface 25. Therefore, the front-to-back dimension of the terminal connection portion 8 of each terminal fitting 5 does not become unnecessarily large. As a result, the distance from the position where the board connection portion 9 is connected to the conductive part of the circuit board 90 to the front end of the hood portion 20 is shortened. In other words, it is possible to prevent the distance from the above connection position on the circuit board 90 to the front end position of the connector 3 from becoming excessively large. 【0040】 [Other embodiments of this disclosure] Embodiment 1 disclosed herein should be considered in all respects to be illustrative and not restrictive. (1) In the first embodiment described above, the gate mark was provided on the upper surface (top surface) of the rear end of the top wall. In contrast, according to other embodiments, the gate mark may be provided on the lower surface (bottom surface) of the rear end of the bottom wall. Alternatively, the gate mark may be formed on the left and right ends of at least one of the upper and lower surfaces of the rear end of the top wall. (2) The bulkhead does not need to be connected to the locking mechanism. For example, the front end surface of the bulkhead may be positioned behind the rear end surface of the locking mechanism. (3) Multiple gate marks may be formed on either the upper or lower surface at the rear end of the top wall. (4) The continuous resin section is a resin portion that penetrates (intersects) the top wall 15, the back wall 19, and the bottom wall 11 in the vertical direction. The region forming the continuous resin section is not limited to a cylindrical shape with the gate mark as the upper surface. [Explanation of Symbols] 【0041】 3… Connector 5…Terminal fittings 6...First bending part 7...Second bending part 8…Terminal connection section 9...Board connection section 10… Housing 11...Bottom wall 13…Side wall 15...Ceiling 15S…Rear side 16…Die-cut holes 17…Rock Club 17S…Latching surface 18…Slope surface 19…Back wall 20…Food Department 21...Bulkhead 23…Terminal protruding surface 25…Step surface 31…Terminal housing hole 33...Tapered section 35...Gate remains 37...Continuous resin part 39…Protruding ribs 40…First recess 41…Lateral ribs 43…Second recess 45…Flange section 47… Fixing member 47S…Bottom surface of the fixing member 48…Reference wall 49... Locking part 50...Opponent's housing 51... Lock Arm 52... Mounting part 53...Opponent's locking mechanism 55...Mutual terminal 60…protective wall 61...Thick part 90... Circuit board 90A… Mounting surface

Claims

[Claim 1] It comprises a terminal fitting and a resin housing on which the terminal fitting is attached, The housing has a cylindrical shape that opens forward and has a bottom wall that rests on the circuit board, a top wall opposite the bottom wall, and a rear wall that connects the rear ends of the bottom wall and the top wall in the vertical direction. The terminal fitting has a shape that penetrates the back wall in the front-to-back direction and has a terminal connection portion located inside the housing and a circuit board connection portion located outside the housing. The top wall has a larger volume than the bottom wall and is formed to be thicker overall in the vertical direction, and has a locking portion within its vertical thickness that holds the mating housing, which is located inside the housing, in a fitted state. A die-cut hole corresponding to the locking part is opened on the rear surface of the top wall. A terminal protruding surface is formed on the rear surface of the aforementioned back wall. The terminal connection portion has a portion that protrudes rearward from the terminal protruding surface. Between the terminal protruding surface and the rear surface of the top wall, a stepped surface extending in the left-right direction is formed at a position lower than the die-cut hole. A connector in which the position where the terminal connection portion protrudes from the terminal protruding surface is located forward of the step difference of the stepped surface and the rear surface of the top wall. [Claim 2] The connector according to claim 1, wherein the housing is provided with a flange portion that protrudes outward from the outer surface of the top wall. [Claim 3] The locking portion is provided with multiple protrusions in the left-right direction at the front end of the top wall, The top wall has a plurality of die-cut holes positioned opposite each of the plurality of locking parts, and partition walls separating the plurality of die-cut holes. The connector according to claim 1, wherein the partition wall extends in the front-rear direction while being connected to the top wall, and its front end is connected to each of the plurality of locking parts. [Claim 4] The connector according to any one of claims 1 to 3, wherein at least one of the top surface of the rear end of the top wall and the bottom surface of the rear end of the bottom wall has a gate mark formed on it corresponding to an injection port for injecting molding resin.

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