JP2013197435A - Wiring substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wiring substrate improved in high frequency characteristics.SOLUTION: A wiring substrate 10 includes a grounded coplanar line having: a substrate 1 having a front surface and a back surface which are made from dielectric bodies; a high frequency signal line 2 formed on the front surface; first ground conductors 3 arranged on both sides of the high frequency signal line 2 at an interval; and a second ground conductor 4 formed on the back surface. The high frequency signal line 2 has width widely formed at an end portion 1b including a terminal end, and the second ground conductor 4 has an opening 5 at a part corresponding to the end portion 1b of the high frequency signal line 2. At a position corresponding to the terminal end 1a of the high frequency signal line 2, a short circuit portion 6 by a conductor around the opening 5 is provided. The short circuit portion 6 can suppress excitation generated at both ends of the opening 5, and improve high frequency characteristics.

Description

  The present invention relates to a high-frequency signal wiring board such as a printed board, a circuit board, or a flexible wiring board having a connection end connected to an electrode terminal or wiring.

  One of the high frequency wiring boards is a wiring board using a coplanar type high frequency line. In the coplanar wiring board, ground conductors are formed on both sides of a high-frequency signal line arranged on the surface. Some coplanar type wiring boards use a grounded coplanar type high frequency line having a ground conductor on the back surface. These high-frequency wiring boards have connection ends for conducting signals with electrodes of electronic components and other wiring boards.

  FIG. 5 is a perspective view showing an example of a connection end portion of a wiring board having a conventional grounded coplanar type line. FIG. 5A shows an example of the front surface of the wiring board 100, and FIG. 5B shows an example of the back surface of the wiring board 100 (for example, Patent Document 1).

  As shown in FIGS. 5A and 5B, ground conductors 103 are formed on both sides of the high-frequency signal line 102 disposed on the surface of the substrate 101, and the high-frequency signal line 102 is disposed on the back surface. A ground conductor 104 is formed in the corresponding portion.

  In the terminal end 101a of the wiring board 100, the line width of the high-frequency signal line 102 is increased in accordance with the width of a conductor such as a lead terminal of an external circuit to be connected and for easy connection. Sometimes. However, when the line width of the high-frequency signal line 102 is widened in this way, it is necessary to match the high-frequency impedance of the widened high-frequency signal line 102 with the high-frequency impedance of the other part. For this reason, if the width of the ground conductor 103 is increased in accordance with the widened portion of the high-frequency signal line 102 at the end portion 101a, and the substrate 101 is very thin, it is not sufficient. A non-forming portion 105 of the ground conductor 104 is provided at a portion corresponding to the connection end of the high-frequency signal line 102 of 104.

  In Patent Document 1, when connecting the terminal of the circuit board and the high-frequency signal line with a metal bump, an island-like wiring pad 106 is formed on the non-formed portion 105 of the ground conductor 104 for the purpose of applying sufficient pressure to the metal bump. Is provided.

JP 2000-151039 A

  As in the example of Patent Document 1, the non-forming portion 105 of the ground conductor 104 provided at the end portion of the conventional wiring board is formed so as to open toward the end face of the wiring substrate. When a conductor is connected to the high-frequency signal line 102 of such a wiring board and a high-frequency signal of about several tens of GHz is conducted, there is a problem that reflection loss and insertion loss occur and sufficient performance cannot be obtained.

  This invention is made | formed in view of said subject, The objective is to provide the wiring board excellent in a high frequency characteristic.

  A wiring board according to an aspect of the present invention includes a substrate made of a dielectric material and having a front surface and a back surface, a high-frequency signal line formed on the front surface, and a space on both sides of the high-frequency signal line on the front surface. In the wiring board having a grounded coplanar line provided with the first ground conductor formed and the second ground conductor formed on the back surface, the high-frequency signal line is formed to have a wide width at the end including the termination. The second ground conductor has an opening at a portion corresponding to the end of the high-frequency signal line.

  In the wiring board of one aspect of the present invention, it is preferable that the opening of the second ground conductor has a widened portion with a wide width on the terminal end side of the high-frequency signal line.

  Moreover, it is preferable that the said termination | terminus of the said high frequency signal track | line is located in the peripheral part of the said board | substrate.

  Moreover, it is preferable that the length of the widened portion is a length that resonates with respect to at least a part of frequencies within a frequency range of a high-frequency signal propagating through the high-frequency signal line.

  It is preferable that the characteristic impedance at the end of the high-frequency signal line is a low impedance of 5% to 20% with respect to the characteristic impedance of the high-frequency signal line.

  It is preferable that the characteristic impedance in the widened portion of the high-frequency signal line is a high impedance of 5% to 20% with respect to the characteristic impedance of the high-frequency signal line.

  According to the wiring substrate of one aspect of the present invention, the second grounding conductor formed on the back surface has an opening in a portion corresponding to the end of the high-frequency signal line and corresponds to the connection end of the high-frequency signal line. Since it has a conductor that is short-circuited to connect both ends of the non-formed portion of the second ground conductor at the position, excitation generated between the second ground conductors at both ends of the non-formed portion is suppressed, and high frequency characteristics are improved. can do.

  In addition, if there is a widened portion with a wide opening width of the second ground conductor on the terminal side of the high-frequency signal line, the change in high-frequency impedance caused by short-circuiting both ends of the non-formed portion is mitigated, and the high-frequency characteristics Can be further improved.

  When the end of the high-frequency signal line is located at the peripheral edge of the board, use the space outside the board to mitigate changes in the high-frequency impedance caused by short-circuiting both ends of the non-formed part. Can do.

  If the length of the widened portion is a length that resonates with respect to at least a part of the frequency within the frequency range of the high-frequency signal propagating through the high-frequency signal line, the high-frequency characteristic is dropped and the high-frequency characteristic is improved. be able to.

  Further, when the characteristic impedance at the end of the high-frequency signal line is set to a low impedance of 5% to 20% with respect to the characteristic impedance of the high-frequency signal line, the high frequency by short-circuiting both ends of the non-formed part and connecting them The relaxation of the change in impedance is optimized, and the high frequency characteristics can be improved.

When the characteristic impedance in the widened portion of the high-frequency signal line is high impedance of 5% to 20% with respect to the characteristic impedance of the high-frequency signal line, the high-frequency impedance is obtained by short-circuiting both ends of the non-formed portion The relaxation of the change is optimized and the high frequency characteristics can be improved.

The wiring board of one Embodiment of this invention is shown, (a) is the top view seen from the surface of the wiring board, (b) is the top view which looked at the wiring board from the back surface. The wiring board of other embodiment of this invention is shown, (a) is the top view seen from the surface of the wiring board, (b) is the top view which looked at the wiring board from the back surface. It is a diagram which shows the high frequency characteristic of the example of embodiment of the wiring board of this invention. It is a perspective view which shows the example of a connection with the electronic device using the wiring board of this invention. An example of a conventional wiring board is shown, (a) is a plan view seen from the front surface of the wiring board, and (b) is a plan view seen from the back surface of the wiring board.

  Hereinafter, a wiring board 10 according to an embodiment of the present invention will be described with reference to the drawings. In addition, all the figures are schematic and may differ from an actual dimensional relationship. Further, in the following description, the terms “upper, lower, left, and right” are merely used for explaining the positional relationship on the drawings, and do not mean the positional relationship in actual use.

  FIG. 1 is a plan view showing a wiring board 10 according to an embodiment of the present invention. FIG. 1 (a) shows the front surface of the wiring board 10, and FIG. 1 (b) shows the opposite surface. In the figure, the conductor portions are hatched for easy understanding. These hatches do not indicate a cross section. Moreover, in each figure, the conductor shape of the opposite surface is shown with the broken line. The figure shows an example of one end, which is a main part of the wiring board, and the other end and both sides are omitted. Usually, a circuit is formed by further extending conductors on the upper and left and right sides of the figure. In the figure, an example in which a differential signal line is used as the high-frequency signal line is shown, but the present invention is not limited to this, and a grounded coplanar line using a single normal high-frequency signal line may be used. These also apply to the wiring board diagrams in the other embodiments.

  As shown in FIG. 1, a pair of high-frequency signal lines 2 (2a, 2b) is formed on the surface of a substrate 1 made of a dielectric material on the wiring board 10, and on both sides of the high-frequency signal line 2 The first ground conductor 3 is formed at a predetermined interval. A second ground conductor 4 is formed on the back surface of the portion of the wiring board 10 where the high-frequency signal line 2 is formed. One end (the lower end in FIG. 1) side of the substrate 1 is the terminal end 1a of the high-frequency signal line. A portion where a connection process with a terminal or wiring of another wiring board on the terminal end 1a side is performed is referred to as an end portion 1b or a connecting end portion 1b.

  The high-frequency signal line 2 is formed so as to widen the line width at the connection end 1b including the termination 1a immediately before the termination 1a. In order to gradually change the high-frequency impedance and avoid reflection of the high-frequency signal, the width between the wide-width portion and the narrow-width portion is gradually increased toward the wide-width portion. Another high-frequency circuit is connected to the wide portion of the line through a lead terminal or the like.

  The first ground conductor 3 is formed on both sides of the high-frequency signal line 2 with a predetermined interval. In the present embodiment, the first ground conductor 3 has the same interval as the other portions even at the connection end 1b where the line of the high-frequency signal line 2 is widely formed. However, depending on the convenience of high-frequency impedance matching, there may be a wider interval at the connection end 1b.

The second ground conductor 4 is provided with an opening 5 at the connection end 1b. The opening 5 is formed by providing a conductor for short-circuiting both sides of the second ground conductor 4 on the end 1a side of a portion provided as a non-forming portion of the second ground conductor 4. A conductor that short-circuits both sides of the second ground conductor 4 is also referred to as a short-circuit portion 6.

  The width W1 of the opening 5 in the direction orthogonal to the line direction of the high-frequency signal line 2 is determined according to the high-frequency impedance. Although FIG. 1 shows a case where the width W1 of the opening 5 is wider than the width W2 of both ends of the high-frequency signal line 2, it may be formed narrowly. The side opposite to the terminal end 1a side of the opening 5 is formed such that the width gradually decreases from the terminal end 1a side to the back in order to gradually change the high-frequency impedance.

  In the opening 5, a short-circuit portion 6 that short-circuits the left and right second ground conductors 4 is formed so as to close the non-formation portion of the second ground conductor 4 at the terminal end 1 a, thereby forming the opening 5. The short-circuit portion 6 is integrally formed at the same time when the second ground conductor 4 is formed, but may be formed so as to be connected to the second ground conductor 4 after the second ground conductor 4 is formed. Unlike the terminal 1a side of the opening 5 opposite to the terminal 1a side, the short-circuit portion 6 is not designed to gradually change the high-frequency impedance. That is, for example, as shown in the figure, it is formed so as to cross the high-frequency signal line 2 with a constant width.

  By forming the short-circuit portion 6 in this way, an increase in reflection loss of high-frequency signals, an increase in insertion loss, and the like are suppressed. This is presumably because excitation that occurs between the second ground conductors 4 on both sides at the terminal end 1 a is suppressed by the short-circuit portion 6.

  Due to the short-circuit portion 6, the high-frequency impedance of the high-frequency signal line 2 in this part is lower than the characteristic impedance in other parts of the high-frequency signal line 2. Preferably, the high-frequency impedance in this part is in a range that is 5% to 20% lower than the characteristic impedance in other parts. For example, when the characteristic impedance of the high-frequency signal lines 2a and 2b is 100Ω, the high-frequency impedance in the short-circuit portion 6 is preferably 80Ω to 95Ω. Impedance mismatch can be made moderate, and improvement in high frequency characteristics can be prevented from deteriorating.

  Next, FIG. 2 is a plan view showing a wiring board 11 according to another embodiment of the present invention. FIG. 2 (a) shows the front surface of the wiring board 11, and FIG. 2 (b) shows the back surface which is the opposite surface. . FIG. 2 is also shown in the same format as FIG. Moreover, the same code | symbol is shown to the site | part corresponding to FIG.

  In contrast to FIG. 1, in the embodiment shown in FIG. 2, a widened portion 7 is provided in which the width W <b> 1 of the opening 5 is widened at the end 1 a side of the opening 5 and adjacent to the short-circuit portion 6. It is preferable to provide the widened portion 7 in which the width W4 in the direction perpendicular to the line direction of the high-frequency signal line 2 is formed wider than the width W1 of the opening 5. By providing the widened portion 7, the high-frequency impedance that is lowered at the terminal end 1 a can be increased in the widened portion 7, and the change in the high-frequency impedance at the short-circuit portion 6 can be compensated.

  The surface of the widened portion 7 on the side opposite to the short-circuited portion 6 becomes narrower toward the back and becomes the same as the width W1 of the opening 5 in the same manner as the surface of the opening 5 opposite to the short-circuited portion 6. Connected. It should be noted that the second ground conductor 4 is naturally not arranged outside the terminal end 1a of the wiring boards 10 and 11, and therefore it is necessary to consider that it becomes a high impedance region.

  The width W4 of the widened portion 7 is preferably set to a high impedance of 5% to 20% with respect to the characteristic impedance in other parts of the high-frequency signal line 2. For example, when the characteristic impedance of the high-frequency signal lines 2a and 2b is 100Ω, the high-frequency impedance in the widened portion 7 is preferably set to 105Ω to 120Ω. Thus, it is preferable that the high-frequency impedance of the high-frequency signal line is low impedance in the short-circuit portion 6 and high impedance in the widened portion 7.

  Further, it is preferable that the length L1 of the widened portion 7 in the direction parallel to the high-frequency signal line 2 is a length at which at least a part of the frequencies in the frequency band of the high-frequency signal line 2 resonate. As a result, a dip due to resonance is generated in the frequency band, and the peak of the high frequency characteristic is lowered to improve the high frequency characteristic.

  FIG. 3 shows a simulation of reflection loss when the high-frequency line 2a is viewed from the termination 1a. A solid line A indicates the reflection loss when there is no conventional short-circuit portion 6 as shown in FIG. As shown by the solid line A, the conventional one has a local maximum exceeding −5 dB in the vicinity of 36 GHz.

  The alternate long and short dash line B is a simulation of the embodiment shown in FIG. It can be seen that the local maximum portion appearing in the solid line A disappears, and in a frequency region higher than 25 GHz, the reflection loss is improved to be approximately −15 dB.

  A two-dot difference line C is a simulation of the embodiment shown in FIG. It can be seen that the reflection loss is smaller than that indicated by the alternate long and short dash line B, and further improved.

  The broken line D is a reflection when the length L of the widened portion 7 in FIG. 2 is made to resonate near a frequency of 42 GHz, the high frequency impedance in the short-circuit portion 6 is optimized to 85Ω, and the high frequency impedance in the widened portion 7 is optimized to 115Ω. Show properties. It can be seen that a minimum point appears in the vicinity of 42 GHz, and that the reflection loss is -20 dB or less in a frequency region of 50 GHz or less. In addition to the reflection characteristics, high-frequency characteristics such as insertion loss are also improved.

  A dielectric material, that is, an electrical insulating material is used for the substrate 1. Specifically, electric circuits generally used for circuit boards, such as flexible boards using polyimide resins, organic boards using resins such as epoxy resins, rigid circuit boards using inorganic materials such as ceramics or glass, etc. Insulating material can be used.

  By plating, printing, vapor deposition, sintering, etc., a metal conductor made of copper, silver, manganese, molybdenum, or other metals or alloys on the surface of the substrate 1, the high-frequency signal line 2, the first ground conductor 3, A second grounding conductor 4 having an opening 5 having a short-circuit portion 6 and / or a widened portion 7 is formed.

  A high-frequency line of the external circuit board is connected to the connection end 1a of the wiring boards 10 and 11. As an example, FIG. 4 shows a connection example between the semiconductor device 20 in which the high frequency semiconductor is sealed in the semiconductor package 21 and the wiring board 10. In FIG. 4, illustration of semiconductor elements and the like inside the semiconductor package 21 is omitted.

  In the semiconductor package 21, for example, the casing is formed of a metal such as iron-nickel-cobalt alloy or a ceramic material such as alumina ceramic. An input / output terminal 22 made of a ceramic such as alumina ceramic and having a connection conductor for connecting the inside and the outside of the semiconductor package 21 is fitted so as to penetrate one side wall of the housing.

As shown in FIG. 4, the wiring boards 10 and 11 are connected to the high-frequency input / output terminals 22 of the semiconductor package 21 by solder or the like via lead terminals 23. The lead terminals 23 electrically connect the high-frequency lines of the input / output terminals 22 and the high-frequency signal lines 2 of the wiring boards 10 and 11, and the ground conductor and the first ground conductors 3 of the wiring boards 10 and 11, respectively. Since the first grounding conductor 3 and the second grounding conductor 4 of the wiring boards 10 and 11 are connected to each other through the via conductors inside the wiring boards 10 and 11, the semiconductor device 20 is connected by such connection. And the wiring boards 10 and 11 can be connected.

  In addition to the example shown in FIG. 4, the wiring boards 10, 11 may be arranged upside down, and the high-frequency signal line 2 and the first ground conductor 3 of the wiring boards 10, 11 may be connected to the upper surface of the lead terminal 22. Good. Alternatively, the lead terminal 22 may be omitted, and the high-frequency signal line 2 and the first ground conductor 3 of the wiring boards 10 and 11 may be directly connected to the line conductor of the input / output terminal 22 via solder bumps or the like.

  As described above, by connecting the high-frequency semiconductor inside the semiconductor package 21 and the external circuit using the wiring boards 10 and 11, the high-frequency characteristics at the connection end of the high-frequency input / output signal are improved. The semiconductor device 20 can be obtained.

  In addition, this invention is not limited to the above-mentioned embodiment, A various change, improvement, etc. are possible in the range which does not deviate from the summary of this invention.

  For example, in the present embodiment, the wiring boards 10 and 11 in which the high-frequency signal line 2 and the first ground conductor 3 are formed on the front surface of the substrate 1 and the second ground conductor 4 is formed on the back surface are shown. Another circuit wiring may be further laminated on the lower layer to form a multilayer wiring board.

  Further, in the present embodiment, one grounded coplanar wiring composed of one high-frequency signal line 2 (or a pair of high-frequency signal lines 2), the first ground conductor 3 and the second ground conductor 4 is used. Although an example has been shown, it goes without saying that a plurality of high-frequency wirings may be arranged in parallel to form wiring boards 10 and 11 having a plurality of grounded coplanar wirings.

1: Substrate 1a: Termination 1b: Connection end 2 (2a, 2b): High-frequency signal line 3: First ground conductor 4: Second ground conductor 5: Opening 6: Short-circuit portion 7: Widening portion 10, 11: Wiring substrate

Claims (6)

A substrate made of a dielectric material and having a front surface and a back surface, a high-frequency signal line formed on the front surface, a first ground conductor disposed on both sides of the high-frequency signal line on the front surface, and the back surface In a wiring board having a grounded coplanar line with a second ground conductor formed in
The high-frequency signal line is formed to have a wide width at an end including a termination, and the second ground conductor has an opening at a portion corresponding to the end of the high-frequency signal line. Wiring board. 2. The wiring board according to claim 1, wherein the opening of the second ground conductor has a widened portion having a wider width on the end side of the high-frequency signal line. The wiring board according to claim 1, wherein the end of the high-frequency signal line is located at a peripheral edge of the board. 3. The wiring board according to claim 2, wherein the width of the widened portion is a length that resonates with respect to at least a part of frequencies within a frequency range of a high-frequency signal propagating through the high-frequency signal line. 5. The characteristic impedance at the end of the high-frequency signal line is a low impedance of 5% to 20% with respect to the characteristic impedance of the high-frequency signal line. The wiring board described. 6. The characteristic impedance in the widened portion of the high frequency signal line is set to a high impedance of 5% to 20% with respect to the characteristic impedance of the high frequency signal line. Wiring board as described in.