Coaxial electrical connector

Abstract

To provide a coaxial electric connector that easily ensures good signal transmission characteristics up to a wide band.SOLUTION: A dielectric 30 includes a first dielectric 31, and a second dielectric 32 provided at a place away from the first dielectric 31 in the vertical direction to form a space 43B-1 with the first dielectric 31, and a center conductor 20 has a contact portion 23C-2 that contacts the second dielectric 32 from below, the first dielectric 31 holds the center conductor 20 in the radial direction, and the second dielectric 32 can be elastically deformed toward a space 43C formed directly above the second dielectric 32 when pressed from below by the contact portion 23C-2.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a coaxial electrical connector connected to a circuit board.

Background Art

[0002] As this type of coaxial electrical connector, a coaxial electrical connector in which a dielectric (insulating member), a center conductor and an annular fitting are provided in the inner space of an outer conductor is disclosed in, for example, Patent Document 1. The inner space of the outer conductor is formed penetrating the outer conductor in the vertical direction perpendicular to the mounting surface of the circuit board. In the inner space, a cylindrical resin dielectric is arranged at a position closer to the lower end, the center conductor extending in the vertical direction is inserted into the holding hole of the dielectric and held by the dielectric, and further, the annular fitting is attached from below, thereby preventing the dielectric and the center conductor from coming off.

[0003] The center conductor has an inclined projection protruding radially outward of the center conductor at a portion inserted and held into the holding hole of the dielectric, and is supported from above by the stepped portion in a state where the inclined projection abuts against the stepped portion (recess) formed on the inner peripheral surface of the holding hole from below. The lower end of the center conductor slightly protrudes from the lower surface of the outer conductor, and when the coaxial electrical connector is mounted on the circuit board, it comes into contact with the circuit portion on the mounting surface of the circuit board from above with contact pressure. At this time, the center conductor always receives an upward reaction force from the mounting surface of the circuit board, but the stepped portion of the dielectric supports the inclined projection of the center conductor from above to counteract the reaction force, thereby generating contact pressure between the center conductor and the circuit portion of the circuit board.

Prior Art Literature

Patent Literature

[0004]

Patent Literature 1

Summary of the Invention

Problem to be Solved by the Invention

[0005] In Patent Document 1, the dielectric is configured as a single component and has both the function of holding the central conductor as described above and the function of generating contact pressure between the central conductor and the circuit portion of the circuit board. This dielectric is cylindrical in shape and extends long in the vertical direction, and is provided so as to fill the space between the inner surface of the outer conductor and the outer surface of the central conductor in the radial direction. Therefore, in the range of the dielectric in the vertical direction, the usable frequency band is narrow because there is no air layer between the inner surface of the outer conductor and the outer surface of the central conductor in the radial direction, and as a result the signal transmission characteristics of the coaxial electrical connector in the broadband are reduced.

[0006] In view of these circumstances, the present invention aims to provide a coaxial electrical connector that can easily ensure good signal transmission characteristics up to a wide bandwidth. [Means for solving the problem]

[0007] (1) The coaxial electrical connector according to the present invention is a coaxial electrical connector connected to a circuit board, comprising: a metallic outer conductor formed by penetrating vertically through an internal space having an axis extending vertically perpendicular to the mounting surface of the circuit board; a dielectric directly or indirectly held by the outer conductor within the internal space; and a metallic central conductor extending vertically within the internal space, held by the dielectric, and in contact with the mounting surface at its lower end.

[0008] In such a coaxial electrical connector, the present invention provides that the dielectric comprises a first dielectric and a second dielectric provided to form a space between the first dielectric and the first dielectric at a position separated from the first dielectric in the vertical direction, the central conductor has a contact portion that contacts the second dielectric from below, the first dielectric holds the central conductor radially, and the second dielectric is elastically deformable toward the space formed directly above the second dielectric when pressed from below by the contact portion.

[0009] In invention (1), the dielectric comprises a first dielectric and a second dielectric, the first dielectric having the function of holding the central conductor radially, and the second dielectric having the function of supporting the contact portion of the central conductor from above. When the coaxial electrical connector is mounted on a circuit board, the lower end of the central conductor receives an upward force (reaction force) from the circuit board. At this time, the second dielectric is pressed by the contact portion of the central conductor and elastically deforms upward, and the elastic force generated in the second dielectric counteracts the above reaction force. As a result, a contact state with appropriate contact pressure is maintained between the contact portion of the central conductor and the circuit board.

[0010] In invention (1), the first dielectric and the second dielectric are spaced apart from each other in the vertical direction, and a space is formed between the first dielectric and the second dielectric. In other words, in the range where this space is formed in the vertical direction, an air layer exists between the inner surface of the outer conductor and the outer surface of the central conductor in the radial direction. Therefore, compared to the conventional case in which a single dielectric extending long in the vertical direction is provided between the outer conductor and the central conductor, the presence of the above air layer widens the usable frequency band, and as a result, good signal transmission characteristics can be ensured up to a wide bandwidth.

[0011] (2) In the invention of (1), the first dielectric material may be provided below the second dielectric material.

[0012] (3) In the invention of (1) or (2), the second dielectric material may have a higher load deflection temperature than the first dielectric material. When the load deflection temperature of the second dielectric material is higher than that of the first dielectric material, plastic deformation becomes less likely even when the operating environment of the coaxial electrical connector becomes high. Therefore, when the contact portion is supported from above by the second dielectric material, the central conductor is less likely to move above its normal position, and the elastic force of the second dielectric material can sufficiently counteract the reaction force. As a result, it becomes easier to maintain a contact state with appropriate contact pressure between the contact portion of the central conductor and the circuit board.

[0013] (4) In the inventions of (1) to (3), the first dielectric material may have a dielectric constant lower than that of the second dielectric material. By making the dielectric constant of the first dielectric material lower than that of the second dielectric material, the usable frequency band of the coaxial connector is widened compared to the case in which the dielectric material consists only of the second dielectric material, and as a result, good signal transmission characteristics can be ensured up to a wide bandwidth.

[0014] (5) In the invention of (4), the first dielectric material may be made of polytetrafluoroethylene, and the second dielectric material may be made of polyetherimide. [Effects of the Invention]

[0015] The present invention provides a coaxial electrical connector that can easily ensure good signal transmission characteristics up to a wide bandwidth. [Brief explanation of the drawing]

[0016] [Figure 1] This is a perspective view showing a coaxial electrical connector according to an embodiment of the present invention together with a circuit board, and is shown from a diagonal upward angle. [Figure 2] Figure 1 is a perspective view of a coaxial electrical connector seen from a diagonal downward angle. [Figure 3] (A) is a cross-sectional view of the coaxial electrical connector in Figure 1, showing a cross-section in a plane containing the axis of the coaxial electrical connector, and (B) is an enlarged cross-sectional view of a part of (A). [Modes for carrying out the invention]

[0017] Embodiments of the present invention will be described below with reference to the attached drawings.

[0018] FIG. 1 is a perspective view showing a coaxial electrical connector 1 (hereinafter referred to as "coaxial connector 1") according to an embodiment of the present invention together with a circuit board P, and shows a state viewed obliquely from above. In FIG. 1, only a part of the circuit board P is illustrated, and actually, the circuit board P is formed to extend further in both the X-axis direction and the Y-axis direction. FIG. 2 is a perspective view showing the coaxial connector 1 as viewed obliquely from below. FIG. 3(A) is a cross-sectional view of the coaxial connector 1, showing a cross-section along a plane including the axis of the coaxial connector 1. FIG. 3(B) is an enlarged cross-sectional view showing a part of FIG. 3(A).

[0019] The circuit board P on which the coaxial connector 1 is mounted is a so-called test board used for performance testing of electronic components (not shown) such as IC chips. The coaxial connector 1 is mounted on the circuit board P, and is a so-called test connector connected via a mating coaxial connector (not shown) and a coaxial cable (not shown) to a measuring instrument (not shown) for measuring electrical characteristics of electronic components. As shown in FIG. 1, on the mounting surface of the circuit board P, a signal pattern P1 extending in the Y-axis direction on the mounting surface and a ground pattern P2 extending so as to surround the signal pattern P1 are formed. An electronic component (not shown) to be subjected to performance testing is mounted near the end on the Y2 side of the signal pattern P1, and the coaxial connector 1 is mounted near the end on the Y1 side of the signal pattern P1 (connector pattern portion). A mating coaxial connector (not shown) connected to a coaxial cable (not shown) is fitted and connected to the coaxial connector 1 from above.

[0020] The coaxial connector 1 has an axis extending in the vertical direction (Z-axis direction) perpendicular to the mounting surface of the circuit board P, and has a symmetrical shape in the Y-axis direction. As shown in FIG. 3, the coaxial connector 1 includes a metal outer conductor 10, a metal center conductor 20 disposed concentrically with an inner space 16 of the outer conductor 10 described later in the inner space 16, a resin dielectric 30, and a metal support body 40. The dielectric 30 includes a first dielectric 31 and a second dielectric 32 formed of different materials from each other.

[0021] The outer conductor 10 has a plate-shaped base portion 11 that extends parallel to the circuit board P, and a cylindrical portion 12 that extends upward from the upper surface of the base portion 11. As shown in Figure 1, the base portion 11 is plate-shaped with its longitudinal direction being the connector width direction (X-axis direction) perpendicular to the Y-axis direction on which the signal pattern P1 extends. On both ends of the cylindrical portion 12 in the connector width direction, there is one mounting hole portion 13, which is a screw hole that penetrates the base portion 11 in the vertical direction. In this embodiment, the coaxial connector 1 is attached to the circuit board P by screwing a screw member (not shown) from below into the mounting hole portion 13 and a screw hole (not shown) provided in the circuit board P corresponding to the mounting hole portion 13.

[0022] As shown in Figure 2, a bottom groove 14 is formed on the bottom surface of the base 11, extending in the direction of the short side of the base 11 (Y-axis direction) at the center in the connector width direction (X-axis direction). As shown in Figure 3(A), the bottom groove 14 is recessed in a rectangular shape from the bottom surface of the base 11 when viewed in the Y-axis direction, and as shown in Figure 2, it extends in the Y-axis direction from the Y2 end of the base 11 to the center. The groove width dimension (dimension in the X-axis direction) of the bottom groove 14 is larger than the width dimension (dimension in the X-axis direction) of the signal pattern P1 (see Figure 1) and the outer diameter of the central conductor 20 (see Figures 1 and 3(A)). In addition, as shown in Figure 2, the side edges on both sides of the bottom groove 14 (edges extending in the Y-axis direction) are arc-shaped concentric with the central conductor 20 and the internal space 16 described later in the area located in the center of the base 11, and are straight in the other areas, extending in the Y-axis direction. Therefore, in the bottom groove 14, the groove width dimension in the range where the side edge is arc-shaped is larger than the groove width dimension in the range where the side edge is straight.

[0023] Further, as shown in Fig. 2, a protrusion 15 slightly protruding from other regions is formed in a region spreading in the center on the bottom surface of the base 11 (see also Fig. 3(A)). The protrusion 15 is formed in a circular shape with a part cut out by the bottom groove 14 when viewed from below. This protrusion 15 is concentric with the center conductor 20 when viewed from below. In the present embodiment, when the coaxial connector 1 is screwed and attached to the circuit board P, the bottom surface of the protrusion 15 is pressed against the top surface of the ground pattern P2 of the circuit board P. Therefore, by providing the protrusion 15 on the bottom surface of the base 11 in this manner, the outer conductor 10 and the ground pattern P2 can be reliably brought into contact with each other near the center conductor, making it easy to ensure a favorable electrical conduction state.

[0024] The cylindrical portion 12 has a central axis extending in the up-down direction, and is formed in a cylindrical shape standing upward from the top surface of the base 11. The cylindrical portion 12 has a larger diameter at an intermediate portion in the up-down direction than at other portions.

[0025] The outer conductor 10 has a central axis extending in the up-down direction, and as shown in Fig. 3(A), an internal space 16 penetrating the base 11 and the cylindrical portion 12 in the up-down direction is formed. The internal space 16 has a large-diameter space 16A and a small-diameter space 16B formed below the large-diameter space 16A.

[0026] The large-diameter space 16A is a cylindrical space formed in a range in the up-down direction extending from the upper end position of the cylindrical portion 12 to a position near the lower end. As shown in Fig. 3(A), the large-diameter space 16A has a slightly larger diameter in the upper space than in the lower space. As shown in Fig. 3(A), a large-diameter portion 41 of the support body 40, which will be described later, is accommodated in the lower space. Further, the upper space is a space for receiving a mating coaxial connector when the mating coaxial connector (not shown) is fitted and connected to the coaxial connector 1 from above. When the mating coaxial connector is fitted and connected, the top surface of the support body 40 supported by the outer conductor 10 comes into contact with the bottom surface of the mating outer conductor (not shown) of the mating coaxial connector, enabling electrical conduction.

[0027] The small-diameter space 16B has a smaller diameter than the large-diameter space 16A and is formed in a vertical range from the lower end of the large-diameter space 16A to the upper end of the bottom groove 14 of the base 11. As shown in Figure 3(A), the upper part of the small-diameter space 16B has a larger diameter than the lower part. The upper part is cylindrical except for the upper end portion, which is tapered, with the inner diameter gradually increasing towards the top. The inner circumferential surface of the small-diameter space 16B has a stepped surface at the boundary between the upper and lower parts in the vertical direction. As shown in Figure 3(A), the stepped portion 17 having this stepped surface is in contact with the lower surface of the support 40 and supports the support 40 from below. The stepped portion 17 may also support the first dielectric 31, which will be described later, from below, in addition to the support 40.

[0028] The central conductor 20 is pin-shaped and extends vertically, and is positioned concentric with the internal space 16 when viewed in the vertical direction. As shown in Figure 3(A), the central conductor 20 has a connection portion 21 at the top to which the mating central conductor (not shown) of the mating coaxial connector is connected, a contact portion 22 at the bottom that can contact the signal pattern P1 (see Figure 1) of the circuit board P, and a connecting portion 23 provided between the connection portion 21 and the contact portion 22 to connect the two.

[0029] As shown in Figure 3(A), the connector 21 is housed within the large-diameter space 16A of the outer conductor 10, or more specifically, within the upper space 43A of the support 40 located within the large-diameter space 16A. The upper part of the connector 21 is cylindrical, with multiple slits 21A formed at various positions in the circumferential direction, and connecting pieces 21B formed between adjacent slits 21A. The mating center conductor (not shown) of the mating coaxial connector is inserted from above into the space surrounded by the multiple connecting pieces 21B. At this time, the multiple connecting pieces 21B are stretched radially outward by the mating center conductor, becoming elastically deformed, and by contacting the outer surface of the mating center conductor with contact pressure, they become electrically conductive with the mating center conductor.

[0030] The contact portion 22 is cylindrical in shape with a smaller diameter than the connecting portion 21. As shown in Figure 3(A), its lower end protrudes into the bottom groove 14, while the rest of it is housed in the small-diameter space 16B. Furthermore, the tip (lower end) of the lower end portion of the contact portion 22 has its tip surface (lower end surface) located slightly below the lower surface of the projection 15. This slight protrusion of the lower end of the contact portion 22 below the lower surface of the projection 15 ensures that when the coaxial connector 1 is mounted on the circuit board P, this lower end reliably contacts the signal pattern P1.

[0031] As shown in Figure 3(A), the connecting portion 23 is housed in the lower space 43B and intermediate space 43C of the support 40, and has three cylindrical portions with different diameters. Specifically, the connecting portion 23 has a first mounting portion 23A located on the lower end side of the connecting portion 23, a second mounting portion 23B located on the upper end side of the connecting portion 23, and an intermediate portion 23C located vertically between the first mounting portion 23A and the second mounting portion 23B. The diameters of these cylindrical portions increase in the order of intermediate portion 23C, first mounting portion 23A, and second mounting portion 23B. The first mounting portion 23A has the same diameter as the contact portion 22, and the second mounting portion 23B has a smaller diameter than the contact portion 22. The intermediate portion 23C has a slightly larger diameter than the contact portion 22 and a smaller diameter than the connecting portion 21. The first dielectric 31 is attached to the outer circumferential surface of the first mounting portion 23A. The second mounting portion 23B has the second dielectric 32 attached to its outer surface.

[0032] As shown in Figure 3(B), a first contact portion 23C-1 is formed at the lower end of the intermediate portion 23C, creating a stepped shape at the boundary with the first mounting portion 23A. The first contact portion 23C-1 contacts the upper surface of the first dielectric 31 by contacting it from above. In other words, the first dielectric 31 supports the first contact portion 23C-1 from below. Also, as shown in Figure 3(B), a second contact portion 23C-2 is formed at the upper end of the intermediate portion 23C, creating a stepped shape at the boundary with the second mounting portion 23B. When the coaxial connector 1 is mounted on the circuit board P, the second contact portion 23C-2 contacts the lower surface of the second dielectric 32 by contacting it from below. In other words, the second dielectric 32 supports the second contact portion 23C-2 from above.

[0033] The first dielectric 31 is made of, for example, polytetrafluoroethylene (PTFE) and is formed into an annular plate shape. In this embodiment, the polytetrafluoroethylene material of the first dielectric 31 has a dielectric constant of approximately 2.1 and a load deflection temperature of approximately 55°C. As shown in Figures 3(A) and (B), the first dielectric 31 is formed to be slightly smaller in the vertical direction than the second dielectric 32, i.e., thinner.

[0034] The first dielectric 31 is formed with an outer diameter slightly larger than the inner diameter of the lower space 43B of the support 40, which will be described later, and is press-fitted and housed within this lower space 43B. As shown in Figure 3(B), the first dielectric 31 has a first through-hole 31A that penetrates the first dielectric 31 in the vertical direction. The first through-hole 31A is formed with an inner diameter that is approximately the same as the outer diameter of the first mounting portion 23A of the central conductor 20.

[0035] In this embodiment, the first dielectric 31 is a continuous annular plate shape over its entire circumferential direction, but instead, for example, a notch may be formed at one location in the circumferential direction. In this case, the notch may be formed to completely separate the first dielectric 31 in the circumferential direction, or it may be formed to partially separate only a part of it.

[0036] The second dielectric 32 is made of, for example, polyetherimide (PEI) and is formed into an annular plate shape. In this embodiment, the polyetherimide material of the second dielectric 32 has a dielectric constant higher than that of the first dielectric 31 (approximately 3.1) and a load deflection temperature higher than that of the first dielectric 31 (approximately 197-200°C). The second dielectric 32 is separate from the first dielectric 31 and is located above the first dielectric 31 and spaced apart from it. The second dielectric 32 has an outer diameter slightly smaller than that of the first dielectric 31. Furthermore, the second dielectric 32 is slightly smaller than the inner diameter of the lower space 43B of the support 40, and a small radial gap is formed between the outer surface of the second dielectric 32 and the inner surface of the lower space 43B. Note that the outer diameter of the second dielectric 32 may be the same as the inner diameter of the lower space 43B. The second dielectric 32 has a second through-hole 32A that penetrates it vertically. The second through-hole 32A has an inner diameter that is approximately the same as the outer diameter of the second mounting portion 23B of the central conductor 20.

[0037] Furthermore, the second dielectric 32 has a notch (not shown) formed at one location in the circumferential direction. Therefore, the second dielectric 32 is discontinuous at the location of the notch in the circumferential direction. The notch may be formed to completely separate the second dielectric 32 in the circumferential direction, or it may be formed to partially separate only a part of it.

[0038] The support 40 is substantially cylindrical and is housed in the internal space 16 of the outer conductor 10. As shown in Figure 3(A), the support 40 has a large-diameter portion 41 at the top and a small-diameter portion 42 at the bottom that is smaller in diameter than the large-diameter portion 41. The outer diameter of the large-diameter portion 41 is slightly smaller than the space at the bottom of the large-diameter space 16A and is housed in the large-diameter space 16A of the outer conductor 10. In this embodiment, the large-diameter portion 41 has a portion at its upper end that is slightly larger in diameter than the rest of the portion, and this portion is press-fitted into the large-diameter space 16A and held by the outer conductor 10. The small-diameter portion 42 has a shape that fits the space at the top of the small-diameter space 16B. That is, the lower part of the small-diameter portion 42 is cylindrical, and the upper part of the small-diameter portion 42, i.e., the portion connected to the large-diameter portion 41, is tapered, with the outer diameter gradually increasing as it goes upwards. The small-diameter portion 42 has an outer diameter that is slightly smaller than the space above the small-diameter space 16B, and is housed within that space.

[0039] The support 40 has an internal space 43 that has a common axis with the internal space 16 of the outer conductor 10 and penetrates the support 40. As shown in Figure 3(B), the internal space 43 has an upper space 43A formed in the vertical direction to be approximately the same as the large diameter portion 41 of the support 40, a lower space 43B formed in the vertical direction to be approximately the same as the small diameter portion 42 of the support 40, and an intermediate space 43C formed in the vertical direction near the boundary between the large diameter portion 41 and the small diameter portion 42 of the support 40. The upper space 43A is formed in the upper part of the internal space 43 and houses the connection portion 21 of the central conductor 20. The lower space 43B is formed in the lower part of the internal space 43 with a slightly smaller diameter than the upper space 43A and houses the connecting portion 23 of the central conductor 20, the first dielectric 31 and the second dielectric 32.

[0040] A support portion 44 is provided between the upper space 43A and the lower space 43B in the vertical direction, extending radially inward from the inner circumferential surface of the internal space 43. The support portion 44 is formed over the entire circumferential area of ​​the internal space 43, and the space enclosed by this support portion 44 constitutes the intermediate space 43C. The intermediate space 43C has a smaller diameter than the upper space 43A and the lower space 43B, and accommodates the upper end of the connecting portion 23 of the central conductor 20. Furthermore, as will be described later, the intermediate space 43C allows for the elastic deformation of the second dielectric 32 by receiving a portion of the second dielectric 32 that has elastically deformed upward from below. As shown in Figure 3(B), the support portion 44 supports the second dielectric 32 by contacting the upper surface of the second dielectric 32 with its lower surface.

[0041] The coaxial connector 1 is manufactured in the following manner. First, the second dielectric 32 is attached to the second mounting portion 23B by inserting the central conductor 20 through the second through-hole 32A of the second dielectric 32 from the lower end side, i.e., the contact portion 22 side. In this embodiment, the second through-hole 32A has a smaller diameter than the intermediate portion 23C of the connecting portion 23, but the second dielectric 32 has a notch formed therein, and when the intermediate portion 23C is inserted through the second through-hole 32A, the second dielectric 32 deforms so as to open circumferentially at the position of the notch, thereby allowing the insertion of the intermediate portion 23C. Then, when the second dielectric 32 passes through the range of the intermediate portion 23C and reaches the range of the second mounting portion 23B, the second dielectric 32 deforms so as to close at the position of the notch. As a result, the inner circumferential surface of the second dielectric 32 comes into contact with the outer circumferential surface of the second mounting portion 23B, and the second dielectric 32 holds the second mounting portion 23B. In this state, the notch of the second dielectric 32 may be completely closed or slightly open.

[0042] With the second dielectric 32 attached to the second mounting portion 23B, the upper surface of the second contact portion 23C-2 of the central conductor 20 is in contact with the lower surface of the second dielectric 32. At this point, it is not essential that the second contact portion 23C-2 is in contact with the second dielectric 32; the second contact portion 23C-2 may only come into contact with the second dielectric 32 and support it from below when the coaxial connector 1 is mounted on the circuit board P.

[0043] Next, the central conductor 20 with the second dielectric 32 attached is inserted into the internal space 43 of the support 40 from below. At this time, the central conductor 20 is inserted until the second dielectric 32 reaches the upper part of the lower space 43B of the internal space 43. As a result, the connecting portion 23 of the central conductor 20 is housed in the lower space 43B and the intermediate space 43C.

[0044] Next, the first dielectric 31 is attached to the first mounting portion 23A from below. At this time, the central conductor 20 is inserted from the lower end side, that is, from the contact portion side, into the first through-hole portion 31A of the first dielectric 31. When the first dielectric 31 is attached to the first mounting portion 23A, it is in contact with the first contact portion 23C-1 from below. In this embodiment, the outer diameter of the first dielectric 31 is slightly larger than the inner diameter of the intermediate space 43C, and it is pressed into the lower space 43B of the internal space 43 from below. Therefore, the first dielectric 31 is compressed by the radially inward pressing force from the inner circumferential surface of the lower space 43B, and the inner circumferential surface of the first through-hole portion 31A firmly holds the outer circumferential surface of the first mounting portion 23A.

[0045] On the other hand, in this embodiment, the outer diameter of the second dielectric 32 is slightly smaller than the inner diameter of the intermediate space 43C. Therefore, the second dielectric 32 is not subjected to pressing force from the inner circumferential surface of the lower space 43B. The second dielectric 32 may also be formed so that its outer diameter is slightly larger than the inner diameter of the intermediate space 43C. In that case, the second dielectric 32 is compressed by a radially inward pressing force from the inner circumferential surface of the lower space 43B, and the inner circumferential surface of the second through-hole 32A firmly holds the outer circumferential surface of the second mounting portion 23B. The second dielectric 32 is also supported from above by the support portion 44 of the support body 40.

[0046] With the central conductor 20 and dielectric 30 housed in the internal space 43, the second dielectric 32 is supported from below by the second contact portion 23C-2 at its radially inner portion, and from above by the support portion 44 of the support body 40 at its radially outer portion (see Figure 3(B)). It is not essential that the second dielectric 32 is supported from above by the support portion 44 at this point; the second dielectric 32 may only be supported by the support portion 44 when the coaxial connector 1 is mounted on the circuit board P.

[0047] Next, the support 40 is press-fitted into the internal space 16 of the outer conductor 10 from above. The support 40 is press-fitted until its lower surface contacts the upper surface of the stepped portion 17 of the outer conductor 10. As a result, as shown in Figure 3(B), the stepped portion 17 contacts the lower surfaces of the first dielectric 31 and the support 40, respectively, supporting the first dielectric 31 and the support 40 from below. In addition, the contact portion 22 of the central conductor 20 is housed in the small-diameter space 16B, except for the lower end portion, which protrudes downward from the small-diameter space 16B and is located in the bottom groove portion 14 of the outer conductor 10. By attaching the support 40 to the outer conductor 10 in this way, the coaxial connector 1 is completed.

[0048] Next, the procedure for using the coaxial connector 1 will be described. In this embodiment, the coaxial connector 1 is mounted on the connector pattern portion of a circuit board P (test board) on which electronic components (such as IC chips) to be subjected to performance testing are mounted. First, the coaxial connector 1 is positioned on the circuit board P with the mounting hole portion 13 of the outer conductor 10 aligned with the screw hole (not shown) of the circuit board P. The coaxial connector 1, positioned on the circuit board P in this manner, is attached to the circuit board P by screwing a screw member (not shown) into the mounting hole portion 13 and the screw hole of the circuit board P from below.

[0049] When the coaxial connector 1 is attached to the circuit board P, the lower end surface of the contact portion 22 of the central conductor 20 is pressed against the signal pattern P1 of the circuit board P from above, and the lower end surface of the projection 15 of the outer conductor 10 is pressed against the ground pattern P2 of the circuit board P from above. As a result, the central conductor 20 and the signal pattern P1, and the outer conductor 10 and the ground pattern P2, make contact with contact pressure and become electrically conductive.

[0050] As previously described, the lower end surface of the contact portion 22 of the central conductor 20 is located slightly below the lower surface of the protrusion 15 of the outer conductor 10. Therefore, when the lower end surface of the contact portion 22 is pressed against the signal pattern P1 of the circuit board P from above, the lower end of the contact portion 22 receives an upward force (reaction force) from the signal pattern P1, causing the central conductor 20 to move upward. As the central conductor 20 moves upward, the first dielectric 31 undergoes elastic deformation due to friction with the outer circumferential surface of the first mounting portion 23A, causing the inner portion in the radial direction to be displaced upward.

[0051] Furthermore, as the central conductor 20 moves upward, the second contact portion 23C-2 of the central conductor 20 presses the radial inner portion of the second dielectric 32 from below. The pressed inner portion of the second dielectric 32 elastically deforms to displace upward, and a part of this inner portion enters the intermediate space 43C of the support 40 from below. In other words, the intermediate space 43C allows for the elastic deformation of the second dielectric 32. This elastic deformation of the second dielectric 32 enables the central conductor 20 to move upward. In this embodiment, the second dielectric 32 is an annular plate shape and is relatively thin in the thickness direction, i.e., in the vertical direction, so elastic deformation in the vertical direction is easy. When the second dielectric 32 elastically deforms upward, the elastic force generated in the second dielectric 32 counteracts the reaction force. As a result of the elastic force generated in the second dielectric 32 counteracting the reaction force, a contact state with appropriate contact pressure is maintained between the contact portion 22 and the signal pattern P1.

[0052] In this embodiment, the first dielectric 31 and the second dielectric 32 are spaced apart from each other in the vertical direction, and a space 43B-1 is formed between the first dielectric 31 and the second dielectric 32 as part of the lower space 43B, as shown in Figure 3(B). In other words, in the range where this space 43B-1 is formed in the vertical direction, that is, in the range of the intermediate portion 23C of the connecting portion 23 of the central conductor 20, an air layer exists between the inner circumferential surface of the support 40 and the outer circumferential surface of the intermediate portion 23C in the radial direction. Therefore, compared to the conventional case in which a single dielectric extending long in the vertical direction is provided between the outer conductor and the central conductor, the presence of the air layer widens the usable frequency band, and as a result, good signal transmission characteristics can be ensured up to a wide bandwidth.

[0053] Furthermore, a mating coaxial connector (not shown), attached to one end of a coaxial cable (not shown), is mated to the coaxial connector 1 from above. As a result, the mating center conductor (not shown) of the mating coaxial connector is connected to the connection portion 21 of the center conductor 20 of the coaxial connector 1, and the mating outer conductor (not shown) of the mating coaxial connector is connected to the cylindrical portion 12 of the outer conductor 10 of the coaxial connector 1. The other end of the coaxial cable is connected to a measuring instrument (not shown) for measuring electrical characteristics. In performance testing of electronic components, a voltage is applied to the electronic components mounted on a test board, and their electrical characteristics are measured by the measuring instrument.

[0054] The performance tests of the aforementioned electronic components (IC chips, etc.) are conducted assuming an operating environment with a wide temperature range (e.g., -55°C to 105°C). Therefore, it is preferable that the contact state with the circuit board P in the coaxial connector 1 used in the performance test is minimized to the effect of temperature changes within the above temperature range. In this embodiment, the dielectric 30 has two members made of different materials, namely a first dielectric 31 and a second dielectric 32. The second dielectric 32, which supports the second contact portion 23C-2 of the central conductor 20 from above, is made of polyetherimide and has a higher load deflection temperature compared to the first dielectric 31, which is made of polytetrafluoroethylene. Therefore, the second dielectric 32 is less likely to undergo plastic deformation even at high temperatures, so that the central conductor 20, which is receiving a reaction force from the circuit board P, is less likely to move above its normal position, and the support force of the second dielectric 32 can sufficiently counteract the reaction force. As a result, it becomes easier to maintain a contact state with appropriate contact pressure between the contact portion 22 of the central conductor 20 and the signal pattern P1 of the circuit board P.

[0055] In this embodiment, the first dielectric 31 that holds the outer surface of the first mounting portion 23A of the central conductor 20 is made of polytetrafluoroethylene and has higher elasticity than the second dielectric 32 made of polyetherimide. Therefore, it can contact the outer surface of the first mounting portion 23A with high contact pressure, and thus can hold the central conductor 20 more firmly than when the dielectric 30 is composed only of the second dielectric 32.

[0056] Furthermore, in this embodiment, since the dielectric constant of the first dielectric 31 is lower than that of the second dielectric 32 in the dielectric 30, the usable frequency band of the coaxial connector 1 is wider compared to the case where the dielectric 30 is composed only of the second dielectric 32, and as a result, good signal transmission characteristics can be ensured up to a wide bandwidth.

[0057] In this embodiment, the dielectric 30 is directly held by the support 40, or in other words, the dielectric 30 is indirectly held by the external conductor 10 via the support 40. However, providing a support is not essential; for example, the dielectric may be directly held by the external conductor without providing a support.

[0058] In this embodiment, the coaxial connector 1 is used for the purpose of testing the performance of electronic components mounted on the circuit board P. However, the test object is not limited to this, and for example, it may be used for the purpose of testing the performance of the circuit board itself. In this case, it is not necessary to mount electronic components on the circuit board.

[0059] In this embodiment, the second dielectric 32 is provided above the first dielectric 31, but alternatively, the second dielectric may be provided below the first dielectric. In this case, the second contact portion is provided in the central conductor at a position where it can contact the second dielectric from below. Furthermore, the space (air layer) formed between the first dielectric and the second dielectric in the vertical direction, that is, below the first dielectric and above the second dielectric, allows for upward elastic deformation of the second dielectric.

[0060] In this embodiment, an example of the coaxial connector 1 being used as a so-called test connector has been described, but its use is not limited to this, and for example, it may be mounted on a circuit board provided in an electrical product.

[0061] In this embodiment, the entire signal pattern P1 and the entire ground pattern P2 are provided on the mounting surface (top surface) of the circuit board P. However, instead, for example, at least a portion of the signal pattern and the ground pattern may be provided on the back surface (bottom surface) or inner layers of the circuit board, extending along the surface of the circuit board. In this case, patterns that are located at different positions in the thickness direction of the circuit board are connected by vias or the like. [Explanation of Symbols]

[0062] 1 Coaxial connector 10 Outer conductor 16 Interior space 20 Central conductor 23C-2 Second contact part (contact part) 30 Dielectrics 31 First Dielectric 32 Second Dielectric 43B-1 Space 43C Intermediate space (space) P Circuit Board

Claims

1. A coaxial electrical connector connected to a circuit board, An external metal conductor is formed by a vertical penetration of an internal space having an axis extending vertically perpendicular to the mounting surface of the circuit board, A dielectric held directly or indirectly within the internal space of the external conductor, A coaxial electrical connector having a metal central conductor that extends vertically within the internal space, is held by the dielectric, and contacts the mounting surface from above at its lower end, The lower end of the central conductor protrudes from the lower surface of the outer conductor and contacts the mounting surface while receiving an upward reaction force from the mounting surface. The dielectric comprises a first dielectric and a second dielectric provided at a position separated from the first dielectric in the vertical direction, so as to form a space between them. The central conductor has a contact portion that contacts the second dielectric from below, The first dielectric is provided below the second dielectric and holds the central conductor in the radial direction. A coaxial electrical connector characterized in that the second dielectric material has a higher load deflection temperature than the first dielectric material, and is elastically deformable toward the space formed directly above the second dielectric material when pressed from below by the contact portion.

2. A coaxial electrical connector connected to a circuit board, An external metal conductor is formed by a vertical penetration of an internal space having an axis extending vertically perpendicular to the mounting surface of the circuit board, A dielectric held directly or indirectly within the internal space of the external conductor, A coaxial electrical connector having a metal central conductor that extends vertically within the internal space, is held by the dielectric, and contacts the mounting surface from above at its lower end, The lower end of the central conductor protrudes from the lower surface of the outer conductor and contacts the mounting surface while receiving an upward reaction force from the mounting surface. The dielectric comprises a first dielectric and a second dielectric provided at a position separated from the first dielectric in the vertical direction, so as to form a space between them. The central conductor has a contact portion that contacts the second dielectric from below, The first dielectric material has a dielectric constant lower than that of the second dielectric material, is positioned below the second dielectric material, and holds the central conductor in the radial direction. A coaxial electrical connector characterized in that the second dielectric is elastically deformable toward the space formed directly above the second dielectric when pressed from below by the contact portion.

3. The coaxial electrical connector according to claim 2, wherein the first dielectric material is made of polytetrafluoroethylene and the second dielectric material is made of polyetherimide.

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