Connection Structure between Package and Transmission Line

Abstract

To provide a connection structure between a metal package and a transmission path, capable of improving high-frequency transmission characteristics.SOLUTION: A connection structure between a metal package and a transmission path includes: a metal package 40 to which a connector 50 is attached; and a transmission path substrate 10 which is housed in the package, and in which a transmission path 14 comprising a signal line pattern 12 and ground patterns 13, 13 disposed at intervals on both sides of the signal line pattern is formed on a surface of a substrate body 11 comprising a dielectric and a rear face ground pattern 15 is formed on a rear face of the substrate body, a central conductor 51 of the connector being electrically connected to an end of the signal line pattern, an external conductor 52 of the connector being electrically connected to the rear face ground pattern. A via hole 16 conducting between the ground pattern and the rear face ground pattern is formed along an end on a side facing the signal line pattern in the ground pattern 13 on the surface, and a distance between an end of the ground pattern and the via hole is equal to a lower limit of a design rule.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a connection structure between a metal package and a transmission line, and more particularly to a connection structure between a metal package and a grounded coplanar waveguide type transmission line housed in the package.

Background Art

[0002] For example, there is a demand for a high-frequency module configured by modularizing a traveling-wave amplifier capable of amplifying a high-frequency PAM4 (Pulse Amplitude Modulation 4) signal exceeding 100 Gbaud. Generally, such a high-frequency module is housed in a metal package with an input transmission line, an integrated circuit, and an output transmission line connected in sequence. A high-frequency signal input to an input connector attached to the package is amplified by the integrated circuit through the input transmission line, and the amplified signal is taken out from an output connector attached to the package through the output transmission line. In high-frequency modules for amplifying high-frequency signals, various measures are taken to suppress deterioration of transmission characteristics due to impedance mismatch, etc. (see, for example, Patent Document 1).

[0003] Patent Document 1 discloses that, in order to solve the problem of impedance mismatch, at the boundary between a substrate on which a signal pattern is formed and a metal package, the outer end of the signal pattern is moved to a position inside by a predetermined distance from the outer end of the substrate so that the cross-sectional shape of the signal transmission line is continuous.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, the conventional technology as described in Patent Document 1 is insufficient in handling high-frequency signals such as high-frequency PAM4 signals exceeding 100 Gbaud, and there is a need for further improvement in transmission characteristics such as reflection characteristics and passing characteristics at high frequencies.

[0006] The present invention has been made to solve such problems, and an object thereof is to provide a connection structure between a metal package and a transmission line capable of improving high-frequency transmission characteristics.

Means for Solving the Problems

[0007] The connection structure between the package and the transmission line of the present invention includes a metal package (40) to which a connector (50) is attached, and a transmission line (14) formed on the surface of a substrate body (11) made of a dielectric and housed in the package, the transmission line including a signal line pattern (12) and ground patterns (13, 13) arranged at intervals on both sides of the signal line pattern. A back surface ground pattern (15) is formed on the back surface of the substrate body. The center conductor (51) of the connector is electrically connected to the end of the signal line pattern, and the outer conductor (52) of the connector is electrically connected to the back surface ground pattern. A via hole (16) for connecting the ground pattern and the back surface ground pattern is formed along the edge of the ground pattern on the side facing the signal line pattern, and the distance between the edge of the ground pattern and the via hole is equal to the lower limit value of the design rule.

[0008] As described above, in the connection structure between the package and the transmission line of the present invention (hereinafter, also simply referred to as the connection structure), via holes for conducting the ground pattern and the back surface ground pattern are formed along the edge on the side facing the signal line pattern in the ground pattern, and the distance between the edge of the ground pattern and the via holes is equal to the lower limit value of the design rule. In the conventional connection structure, signals propagate through regions where there are no via holes in the ground pattern near the signal line pattern, which has caused a dip (hereinafter, also referred to as a dip) in the transmission characteristics. On the other hand, with the above configuration, by directly connecting the ground pattern and the back surface ground pattern and electrically integrating them in the region where the signal propagates, high-frequency transmission characteristics such as reflection characteristics and passing characteristics at high frequencies can be improved.

[0009] Further, in the connection structure between the package and the transmission line of the present invention, the interval between adjacent via holes may be equal to the lower limit value of the design rule.

[0010] With this configuration, in the connection structure between the package and the transmission line of the present invention, by directly connecting and further electrically integrating the ground pattern on the surface and the back surface ground pattern in the region where the signal propagates in the ground pattern near the signal line pattern, the high-frequency transmission characteristics can be further improved.

[0011] Further, the connection structure between the package and the transmission line of the present invention may be configured such that via holes for conducting the ground pattern and the back surface ground pattern are formed along the edge on the side opposite to the side facing the signal line pattern in the ground pattern.

[0012] With this configuration, the connection structure between the package and the transmission line of the present invention can improve the high-frequency transmission characteristics by connecting and electrically integrating the ground pattern on the surface and the back surface ground pattern while minimizing the number of via holes and ensuring the strength of the transmission substrate.

[0013] In addition, the connection structure between the package of the present invention and the transmission line may be configured such that a castellation (17) for metallizing the side surface of the substrate body to conduct the ground pattern and the back surface ground pattern is formed at an edge portion on the side opposite to the wall portion (43) of the package on the side where the connector is attached in the substrate body.

[0014] In the conventional connection structure, signals propagated in a region near the edge portion on the side opposite to the wall portion of the package on the side where the connector is attached in the substrate body have caused dips in transmission characteristics. On the other hand, with the above configuration, by directly connecting the surface ground pattern and the back surface ground pattern through the castellation to electrically integrate them, the high-frequency transmission characteristics can be improved.

[0015] Further, in the connection structure between the package of the present invention and the transmission line, a metal connection conductor (18) for connecting the external conductor of the connector or the package connected to the external conductor and the ground pattern on the surface may be provided.

[0016] In the conventional connection structure, in the ground pattern on the surface of the substrate body, in the region from the substrate end where via holes cannot be arranged to the via holes, the metal package and the ground pattern on the surface are not directly electrically connected. Thus, signals propagated in the region where the front and back ground patterns are not connected between the substrate end on the connector side of the substrate body and the via holes have deteriorated the high-frequency transmission characteristics. On the other hand, by directly connecting the external conductor of the connector or the package connected to the external conductor and the ground pattern on the surface with a connection conductor, the metal package and the ground pattern on the surface can be electrically integrated to improve the high-frequency transmission characteristics.

Advantages of the Invention

[0017] According to the present invention, a connection structure between a metal package and a transmission line that can improve high-frequency transmission characteristics can be provided.

Brief Description of Drawings

[0018]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Embodiments for Carrying Out the Invention

[0019] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0020] FIG. 1 is a diagram showing the configuration of a high-frequency module in which a connection structure between a metal package and a transmission line according to an embodiment of the present invention is used. The high-frequency module 1 is a high-frequency module capable of amplifying a high-frequency PAM4 signal exceeding, for example, 100 Gbaud. As shown in FIG. 1, the high-frequency module 1 includes a transmission line substrate 10 provided with an input-side transmission line 14, a transmission line substrate 20 provided with an output-side transmission line 24, an integrated circuit element 30 having an integrated circuit 31 such as an amplifier circuit, and a metal package 40 housing these components. The connection structure 100 according to the present embodiment is a connection structure between the metal package 40 to which the connector 50 is attached and the transmission line 14 formed on the transmission line substrate 10.

[0021] (Transmission line substrate) As shown in FIG. 2, the input-side transmission line substrate 10 has a linear signal line pattern 12 made of a metal foil and ground (GND) patterns 13, 13 arranged at intervals on both sides of the signal line pattern 12 on the surface 11a of a substrate body 11 made of a dielectric such as quartz. Hereinafter, the combination of the signal line pattern 12 and the GND patterns 13, 13 is referred to as a transmission line 14. A GND pattern 15 (also referred to as a back surface GND pattern) is formed on the back surface 11b or an intermediate layer. That is, a grounded coplanar line type transmission line 14 is formed on the transmission line substrate 10.

[0022] A plurality of via holes 16 penetrating from the surface 11a to the back surface 11b of the substrate body 11 are formed in the transmission line substrate 10 to conduct the GND pattern 13 on the surface 11a and the back surface GND pattern 15. The number of via holes 16 is preferably large for conducting the GND pattern 13 and the back surface GND pattern 15, but if there are too many, the strength of the transmission line substrate 10 will be weakened. Therefore, the number and arrangement are appropriately set to ensure sufficient conduction while ensuring the required strength. A silicon capacitor 19 for cutting off the DC component is provided in the middle of the signal line pattern 12 of the present embodiment, but it may be omitted if necessary.

[0023] (Output-side transmission line substrate) As shown in FIG. 1, the output-side transmission circuit board 20 has the same configuration as the input-side transmission circuit board 10.

[0024] (Integrated circuit element) The integrated circuit element 30 has, for example, an integrated circuit (IC) 31 such as an amplifier formed on a semiconductor substrate (or chip). The input side of the integrated circuit 31 is connected, for example, by a wire to one end of the signal line pattern 12 of the transmission circuit board 10, and the GND of the integrated circuit 31 is connected, for example, by a wire to the GND pattern 13 of the transmission circuit board 10. The output side of the integrated circuit 31 is connected, for example, by a wire to one end of the signal line pattern 22 of the transmission circuit board 20, and the GND of the integrated circuit 31 is connected, for example, by a wire to the GND pattern 23 of the transmission circuit board 20.

[0025] (Package) The package 40 is made of metal. Specifically, it has a metal container 41 and a metal lid. The lid is attached to the container 41 to form an internal space surrounded by metal walls, and the transmission circuit board 10, the integrated circuit element 30, and the transmission circuit board 20 are accommodated in the internal space. Through holes are formed in the opposing wall portions 43a, 43b of the container 41, and coaxial connectors 50 and 60 such as W connectors are attached to the through holes. The input connector 50 includes a center conductor 51 whose tip is connected to the signal line pattern 12 of the transmission circuit board 10, and an outer conductor 52 formed coaxially with respect to the center conductor 51 via an insulating material. The output connector 60 includes a center conductor 61 whose tip is connected to the signal line pattern 22 of the transmission circuit board 20, and an outer conductor 62 formed coaxially with respect to the center conductor 61 via an insulating material. Also, a radio wave absorber is attached to the back side of the metal lid so as to suppress spatial resonance in the formed internal space.

[0026] (Connection structure) Next, the connection structure 100 between the metal package 40 and the transmission path 14 of the transmission circuit board 10 will be described.

[0027] The central conductor 51 of the connector 50 is electrically connected to one end of the signal line pattern 12 of the transmission base board 10 by soldering or the like. The outer conductor 52 of the connector 50 is electrically connected to the wall portion 43 of the package 40, and is electrically connected to the back surface GND pattern 15 of the transmission base board 10 through the wall portion 43, an appropriate conductive member, or the like, or directly.

[0028] <Arrangement of via holes in the GND pattern> In the transmission base board 10, via holes 16 for connecting the GND pattern 13 and the back surface GND pattern 15 are formed in a row along the edge of the GND pattern 13 on the side facing the signal line pattern 12. The via holes 16 are arranged such that the distance between the edge of the GND pattern 13 (that is, the boundary or end defining the GND pattern 13) and the via holes 16 is equal to the lower limit value of the design rule which is a manufacturing limitation. Here, the distance between the edge of the GND pattern 13 and the via holes 16 refers to the shortest distance from the edge (boundary) of the GND pattern 13 on the side facing the signal line pattern 12 to the end of the via holes 16 on the signal line pattern 12 side. Also, the via holes 16 are arranged such that the interval between adjacent via holes 16, 16 is equal to the lower limit value of the design rule. Here, the interval between adjacent via holes 16, 16 refers to the interval between the ends closer to each other of the via holes 16. Specifically, in this embodiment, for example, the distance between the edge of the GND pattern 13 and the via holes 16 is 0.05 mm, and the interval between adjacent via holes 16, 16 is 0.2 mm.

[0029] Also, the more via holes 16 there are in the GND pattern 13, the more the back GND pattern 15 connected to the metal package 40 and the GND pattern 13 on the surface 11a are electrically integrated. However, the risk of the transmission base board 10 cracking increases. Therefore, it is preferable to minimize the number of via holes 16. For this reason, the via holes 16 may be arranged along the edge of the GND pattern 13. In the present embodiment, in addition to the one row of via holes 16 arranged along the edge on the side of the GND pattern 13 facing the signal line pattern 12, along the edge on the side of the GND pattern 13 opposite to the side facing the signal line pattern 12, a row of via holes 16 for connecting the GND pattern 13 and the back GND pattern 15 is formed. In the present embodiment, the via holes 16 are limited to only these two rows in one GND pattern 13. Also, in order to reduce the risk of the transmission base board 10 cracking, the diameter of the via holes 16 is set to the lower limit value of the design rules.

[0030] <Cancellation> According to the design rules, the via holes 16 cannot be arranged at the board edge of the transmission base board 10. Therefore, in the transmission base board 10, the area between the via holes 16 from the board edge on the side of the wall portion 43a of the package 40 is a region where the metal package 40 and the GND pattern 13 on the surface 11a of the transmission base board 10 are not directly connected. Therefore, by providing a cancellation 17 for metallizing the side surface 11c of the transmission base board 10 in this region, the metal package 40 and the GND pattern 13 are sufficiently electrically connected up to the board edge of the transmission base board 10.

[0031] Specifically, on the edge of the substrate body 11 of the transmission substrate 10 on the side facing the wall portion 43a of the package 40 on the side where the connector 50 is attached, a casteration 17 is formed by metallizing the side surface 11c of the substrate body 11 to connect the GND pattern 13 and the back surface GND pattern 15. The shape of the casteration 17 in plan view may be any shape such as a semicircle, semi-ellipse, rectangle, etc., and the number can also be arbitrarily set. In this embodiment, in the transmission substrate 10 that is rectangular in plan view, two casterations 17 having a rectangular shape with rounded corners in plan view are provided on one side facing the wall portion 43a of the package 40, and two casterations 17 having the same shape are also provided on the side opposite to this side.

[0032] Also, in the GND pattern 13 on the surface 11a of the transmission substrate 10, in the region between the via holes 16 from the substrate end where the via holes 16 cannot be arranged, the metal package 40 and the GND pattern 13 on the surface 11a are not directly connected. Therefore, a connection conductor 18 made of a metal (for example, gold) for connecting the external conductor 52 of the connector 50 or the package 40 connected to the external conductor 52 and the GND pattern 13 on the surface 11a is provided.

[0033] <Simulation results> FIG. 3(a) shows a simulation model of the transmission substrate 10A used in the connection structure 100 according to this embodiment, and (b) shows the simulation results of the reflection characteristics, and (c) shows the simulation results of the transmission characteristics. In FIGS. 3(b) and (c), the broken line shows the case (Configuration Example 1) where the distance d1 between the edge of the GND pattern 13 and the via hole 16 is set to 168 μm, and the solid line shows the case (Configuration Example 2) where the distance d1 between the edge of the GND pattern 13 and the via hole 16 is set to 50 μm, which is the lower limit value of the design rule. As shown in FIGS. 3(b) and (c), in Configuration Example 1, it was confirmed that a dip in the reflection characteristics occurs near 120 GHz, and when the distance d1 between the edge of the GND pattern 13 and the via hole 16 is reduced in Configuration Example 2, the transmission performance is improved.

[0034] FIG. 4(a) shows a simulation model of the transmission substrate 10B used in the connection structure 100 according to the present embodiment, (b) shows the simulation results of the reflection characteristics, and (c) shows the simulation results of the transmission characteristics. In FIGS. 4(b) and (c), the solid line indicates the case (Configuration Example 3) where the castellations 17 are formed, and the dashed line indicates the case (the above Configuration Example 1) where the castellations are not formed for comparison. As shown in FIGS. 4(b) and (c), in Configuration Example 3, it was confirmed that the band with good transmission characteristics extends by forming the castellations 17.

[0035] FIG. 5(a) shows a simulation model of the transmission substrate 10C used in the connection structure 100 according to the present embodiment, (b) shows the simulation results of the reflection characteristics, and (c) shows the simulation results of the transmission characteristics. In this case (Configuration Example 4), the distance d1 between the edge of the GND pattern 13 and the via hole 16 is set to 50 μm, which is the lower limit value of the design rule, and eight castellations 17 are formed. Further, in order to prevent the substrate from cracking, the via holes 16 are arranged along the edge of the GND pattern 13, and the number of via holes 16 is reduced compared to Configuration Example 3 in FIG. 4. As shown in FIGS. 5(b) and (c), in Configuration Example 4, even if the number of via holes 16 is suppressed to this extent, by setting the distance d1 between the edge of the GND pattern 13 and the via hole 16 to 50 μm, which is the lower limit value of the design rule, and forming the castellations 17, it was confirmed that the transmission characteristics can be improved.

[0036] Fig. 6(a) shows the simulation model of the transmission substrate 10 used in the connection structure 100 according to this embodiment, (b) shows the simulation result of the reflection characteristics, and (c) shows the simulation result of the transmission characteristics. In this case (example), via holes 16 are formed only along the edges on the side of the GND pattern 13 facing the signal line pattern 12 and the edges on the opposite side, reducing the number of via holes 16 compared to Configuration Example 4 in Fig. 5 and minimizing the number. In this example, the distance d1 between the edge of the GND pattern 13 and the via hole 16 is set to 50 μm, which is the lower limit of the design rule, and four castellations 17 are formed. As shown in Figs. 6(b) and (c), even when the number of via holes 16 is minimized in this example, by setting the distance d1 between the edge of the GND pattern 13 and the via hole 16 to 50 μm, which is the lower limit of the design rule, and forming the castellations 17, it was confirmed that the transmission characteristics can be improved.

[0037] Although the connection structure between the transmission substrate 10 and the package 40 has been described, the same applies to the connection structure between the transmission substrate 20 and the package 40.

[0038] <Function and Effect> As described above, in the connection structure 100 between the metal package 40 and the transmission line 14 of this embodiment, via holes 16 for electrically connecting the GND pattern 13 and the back GND pattern 15 are formed along the edge on the side of the GND pattern 13 facing the signal line pattern 12, and the distance between the edge of the GND pattern 13 and the via hole 16 is equal to the lower limit of the design rule. In the conventional connection structure, the signal propagates through the region where there are no via holes 16 in the GND pattern 13 near the signal line pattern 12, which causes a dip in the transmission characteristics. In contrast, with the above configuration, by directly connecting the GND pattern 13 and the back GND pattern 15 and electrically integrating them in the region where the signal propagates, the high-frequency transmission characteristics such as the reflection characteristics and the passing characteristics at high frequencies can be improved.

[0039] In addition, in the connection structure 100 between the package 40 and the transmission line 14 of the present embodiment, the interval between adjacent via holes 16, 16 is equal to the lower limit value of the design rule. With this configuration, in the region where the signal propagates in the GND pattern 13 near the signal line pattern 12, the GND pattern 13 and the back surface GND pattern 15 are directly connected and further integrated electrically, so that the high-frequency transmission characteristics can be further improved.

[0040] In addition, the connection structure 100 between the package 40 and the transmission line 14 of the present embodiment, in addition to the one row of via holes 16 arranged along the edge on the side of the GND pattern 13 facing the signal line pattern 12, along the edge on the side of the GND pattern 13 opposite to the side facing the signal line pattern 12, a row of via holes 16 for connecting the GND pattern 13 and the back surface GND pattern 15 is formed. With this configuration, while minimizing the number of via holes 16 and ensuring the strength of the transmission substrate 10, the GND pattern 13 and the back surface GND pattern 15 are connected and integrated electrically, so that the high-frequency transmission characteristics can be improved.

[0041] In addition, in the connection structure 100 between the package 40 and the transmission line 14 of the present embodiment, on the edge of the substrate body 11 on the side facing the wall portion 43a of the package 40 on the side where the connector 50 is attached, a castellation 17 is formed by metallizing the side surface 11c of the substrate body 11 to connect the GND pattern 13 and the back surface GND pattern 15. In the conventional connection structure, the signal propagated in the region near the edge on the side of the package 40 on the side where the connector 50 is attached to the substrate body 11 has caused a dip in the transmission characteristics. However, with the above configuration, the castellation 17 directly connects the GND pattern 13 and the back surface GND pattern 15 and integrates them electrically, so that the high-frequency transmission characteristics can be improved.

[0042] In the conventional connection structure, in the GND pattern 13 on the surface 11a of the substrate body 11, in the region from the substrate end where the via hole 16 cannot be disposed to the via hole 16, the metal package 40 and the GND pattern 13 on the surface 11a are not directly electrically connected. As signals propagate through this region, the high-frequency transmission characteristics deteriorate. In the connection structure 100 of the present embodiment, by providing a metal connection conductor 18 that connects the external conductor 52 of the connector 50 or the package 40 connected to the external conductor 52 and the GND pattern 13 on the surface 11a, the metal package 40 and the GND pattern 13 on the surface 11a are electrically integrated, and the high-frequency transmission characteristics can be improved.

Industrial Applicability

[0043] As described above, the present invention has the effect of improving high-frequency transmission characteristics and is useful for the entire connection structure of the metal package and the transmission path.

Explanation of Reference Numerals

[0044] 1 High-frequency module 10, 10A, 10B, 10C, 20 Transmission path substrate 11 Substrate body 11a Surface 11b Back surface 11c Side surface 12, 22 Signal line pattern 13, 23 GND pattern 14, 24 Transmission path 15 Back surface GND pattern 16 Via hole 17 Cancellation 18 Connection conductor 19 Silicon capacitor 30 Integrated circuit element 31 Integrated circuit 40 Package 41 Container 43, 43a, 43b Wall portion 50, 60 Connector 51, 61 Center conductor 52 and 62 External Conductors 100 Connection Structure

Claims

1. A metal package (40) to which a connector (50) is attached, and a transmission line substrate (10) housed in the package, having a signal line pattern (12) formed on the surface of a substrate body (11) made of a dielectric, and ground patterns (13, 13) arranged at intervals on both sides of the signal line pattern, a back surface ground pattern (15) formed on the back surface of the substrate body, a center conductor (51) of the connector electrically connected to an end of the signal line pattern, and an outer conductor (52) of the connector electrically connected to the back surface ground pattern, comprising: Via holes (16) for connecting the ground pattern and the back surface ground pattern are formed along an edge of the ground pattern on the side facing the signal line pattern, and the distance between the edge of the ground pattern and the via holes is equal to the lower limit value of the design rule. The distance between adjacent via holes is equal to the lower limit value of the design rule. Via holes for connecting the ground pattern and the back surface ground pattern are formed along an edge of the ground pattern on the side opposite to the side facing the signal line pattern. A casteration (17) for connecting the ground pattern and the back surface ground pattern is formed by metallizing a side surface of the substrate body at an edge on the side of the substrate body facing a wall portion (43) of the package on the side where the connector is attached. A connection structure between the package and the transmission line is characterized by this.

2. The connection structure between the package and the transmission line according to claim 1, further comprising a metal connection conductor (18) for connecting the outer conductor of the connector or the package connected to the outer conductor and the ground pattern on the surface.

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