JP2011096953A - Wiring substrate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wiring substrate that has a pad for external connection to which a signal wiring conductor is connected through a signal through conductor, and can successfully transmit a high-frequency signal exceeding 25 GHz. <P>SOLUTION: At least one of an upper conductor layer 8 for grounding or power supply and a lower conductor layer 9 for grounding or power supply has a strip-shaped protrusion 8b or 9b that extends toward the inside of a first opening 8a or a second opening 9a so as to be opposed to the signal wiring conductor 5. Since a capacitance component is formed between the signal wiring conductor 5, and the conductor layers 8 and 9 for grounding or power supply also in portions which correspond to the first opening 8a and the second opening 9a of the signal wiring conductor 5, the characteristic impedance of the signal wiring conductor 5 may be not increased rapidly. Consequently, the wiring substrate is capable of extremely efficiently transmitting the high-frequency signal exceeding 25 GHz. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a wiring board.

  In general, high speed and large capacity transmission are becoming prominent in current electronic devices. Accordingly, wiring boards used in electronic devices are required to have a form with less electrical loss in high-frequency transmission. Therefore, as shown in FIG. 4, the wiring board having a transmission path for transmitting a high-frequency signal has insulating layers 102 and 103 of an insulating substrate 104 formed by laminating a plurality of insulating layers 102 and 103 on the lower surface of the insulating plate 101, for example. A band-shaped signal wiring conductor 105 for propagating a high-frequency signal is provided between the signal wiring conductor 105 and the signal wiring conductor 105 with the insulating layer 102 and the insulating layer 103 sandwiched between the ground and the signal wiring conductor 105. Power supply conductor layers 106 and 107 are provided. Further, a ground or power supply conductor layer 108 is provided between the insulating layers 102 and 103 so as to surround the signal wiring conductor 105, and the signal wiring conductor 105 is grounded on the top, bottom, left and right. Alternatively, the characteristic impedance of the signal wiring conductor 105 is set to a predetermined value by surrounding the power supply conductor layers 106, 107, 108 at a predetermined interval. To have. Then, the signal wiring conductor 105 is connected by connecting the end of the signal wiring conductor 105 to the signal external connection pad 110 formed on the lower surface of the insulating layer 103 by the signal through conductor 109 penetrating the insulating layer 103. Is electrically led to the lower surface of the insulating substrate 104 through the signal through conductor 109 and the signal external connection pad 110. In an actual wiring board, an insulating layer and a conductor layer are also laminated on the upper surface side of the insulating plate 101, but they are omitted for simplification of description.

  As shown in FIGS. 5A and 5B, the grounding or power supply conductor layers 106, 107, and 108 have a circular shape larger than the signal external connection pad 110 at a position corresponding to the signal external connection pad 110. Openings 106a, 107a, and 108a are formed. The opening 107 a is for maintaining electrical insulation between the grounding or power supply conductor layer 107 and the signal external connection pad 110. Further, the openings 106a and 108a suppress signal reflection at the external connection pad 110 by reducing the electrostatic capacitance between the ground or power supply conductor layers 106 and 108 and the signal external connection pad 110. This is for efficiently transmitting a high-frequency signal to the outside.

  However, according to such a conventional wiring board, the signal wiring conductor 105 has no ground or power conductor layers 106 and 107 above and below the portions corresponding to the openings 106a and 107a. Alternatively, since the capacitance component with the power supply conductor layers 106 and 107 decreases, the characteristic impedance increases rapidly. As a result, for example, when a high-frequency signal exceeding 25 GHz is propagated to the signal wiring conductor 105, signal reflection loss and insertion loss increase due to characteristic impedance mismatch in the portions corresponding to the openings 106a and 107a. This causes a problem that it is difficult to transmit the signal satisfactorily.

JP-A-5-343554

  The present invention relates to a wiring board in which a signal wiring conductor disposed between insulating layers in an insulating board is connected to a signal external connection pad formed on the lower surface of the insulating board through a signal through conductor. An object of the present invention is to provide a wiring board capable of satisfactorily transmitting a high frequency signal exceeding 25 GHz to a wiring conductor for use.

  The wiring board of the present invention includes an insulating substrate formed by laminating a plurality of insulating layers including an upper insulating layer and a lower insulating layer laminated on the lower surface of the upper insulating layer, and is attached to the lower surface of the insulating substrate. An upper layer having a first opening larger than the signal external connection pad at a position corresponding to the signal external connection pad. A lower layer having a second opening larger than the signal external connection pad at a position corresponding to the signal external connection pad. Between the upper-layer insulating layer and the lower-layer insulating layer so as to face the upper-layer ground or power-conductor layer and the lower-layer ground or power-conductor layer. And one end is said A strip-shaped signal wiring conductor extending to a position corresponding to the signal external connection pad and at least the lower insulating layer, the one end of the signal wiring conductor and the signal external In the wiring board having a signal through conductor for connecting to the connection pad, at least one of the upper layer ground or power source conductor layer and the lower layer ground or power source conductor layer is opposed to the signal wiring conductor. It has a strip-shaped projection extending inside the first opening or the second opening.

  According to the wiring board of the present invention, at least one of the upper layer ground or power source conductor layer and the lower layer ground or power source conductor layer of the signal wiring conductor faces the signal wiring conductor and the first opening or By having the band-shaped protrusion extending inside the second opening, the portion corresponding to the first and second openings in the signal wiring conductor is also between the signal wiring conductor and the ground or power supply conductor layer. As a result, even if a high-frequency signal exceeding 25 GHz is propagated to the signal wiring conductor, the signal reflection does not occur. Loss and insertion loss are reduced, whereby high frequency signals can be transmitted very efficiently.

FIG. 1 is a schematic cross-sectional view of an essential part showing an example of an embodiment of a wiring board according to the present invention. (A) is the principal part schematic perspective view which abbreviate | omitted the insulating board 2 of the wiring board shown in FIG. 1, and the insulating layers 3 and 4, (b) is a partial cross section perspective view of (a). 3A and 3B are graphs showing simulation results of an example of an embodiment of the present invention and a conventional wiring board. FIG. 4 is a schematic cross-sectional view of a main part of a conventional wiring board. (A) is the principal part schematic perspective view which abbreviate | omitted the insulating board 101 of the wiring board shown in FIG. 4, and the insulating layers 102 and 103, (b) is a partial cross section perspective view of (a).

  Next, an example of an embodiment of the wiring board of the present invention will be described. As shown in FIG. 1, the wiring board of this example is arranged between, for example, an insulating plate 2 forming an insulating substrate 1, insulating layers 3 and 4 stacked on the lower surface thereof, and insulating layers 3 and 4. A strip-shaped signal wiring conductor 5 for propagating the provided high-frequency signal, and a circular signal external connection pad 6 formed on the lower surface of the insulating substrate 1 corresponding to an end of the signal wiring conductor 5; A signal through conductor 7 that penetrates the insulating layer 4 to connect the end of the signal wiring conductor 5 and the signal external connection pad 6, and the insulating plate 2 and the insulating layer 3 so as to face the signal wiring conductor 5. And a grounding or power supply conductor layer 8 having an opening 8a larger than the signal external connection pad 6 at a position corresponding to the signal external connection pad 6 and the signal wiring conductor 5. Formed on the lower surface of the insulating substrate 1 and the signal external Corresponding to the signal external connection pad 6 and formed between the grounding or power supply conductor layer 9 having the opening 9a surrounding the connection pad 6 and the insulating layers 3 and 4 so as to surround the signal wiring conductor 5 And a grounding or power supply conductor layer 10 having an opening 10 a larger than the signal external connection pad 6. In an actual wiring board, an insulating layer and a conductor layer are also laminated on the upper surface side of the insulating plate 2, but the description is omitted for the sake of simplicity.

  The insulating plate 2 has a thickness of about 50 to 1000 μm, and the insulating layers 3 and 4 have a thickness of, for example, 5 to 50 μm. The insulating plate 2 and the insulating layers 3 and 4 can be formed of various resin-based insulating materials and ceramic-based insulating materials. The signal wiring conductor 5, the signal external connection pad 6, the ground or power supply conductor layers 8, 9, and 10 each have a thickness of about 10 to 30 μm, and the signal through conductor 7 has a diameter of 30 to 200 μm. Degree. These signal wiring conductor 5, signal external connection pad 6, grounding or power supply conductor layers 8, 9, 10 and signal through conductor 7 are made of various conductive materials such as metal foil, metal plating, metal paste and the like. Can be formed.

  As shown in FIGS. 2A and 2B, the signal wiring conductor 5 extends between the insulations 3 and 4 in a thin strip pattern having a width of about 10 to 50 μm. For example, a high frequency signal exceeding 25 GHz is propagated to the signal wiring conductor 5. A circular land 5 a for connecting to the signal through conductor 7 is formed at the end of the signal wiring conductor 5.

  The signal external connection pad 6 is a circle having a diameter of 400 to 800 μm, and is formed on the lower surface of the insulating substrate 1 so that the outer peripheral portion thereof is located at a position corresponding to the end of the signal wiring conductor 5. .

  The signal through conductor 7 electrically connects the end of the signal wiring conductor 5 and the outer periphery of the signal external connection pad 6, whereby the signal wiring conductor 5 is connected to the signal through conductor 7 and the signal. Electrically led to the lower surface of the insulating substrate 1 through the external connection pads 6.

  The ground or power supply conductor layer 8 positioned above the signal wiring conductor 5 is opposed to the signal wiring conductor 5 with the insulating layer 3 interposed therebetween, and is connected to the signal external connection pad 6 at a position corresponding to the signal external connection pad 6. A so-called solid pattern is formed between the insulating plate 2 and the insulating layer 3 so as to have a circular opening 8a having a diameter larger than the pad 6 by about 100 to 300 μm. The opening 8a is for preventing an unnecessary capacitance component from being formed between the grounding or power supply conductor layer 8 and the signal external connection pad 6. By providing the opening 8a, a signal is provided. It is possible to reduce signal reflection at the external connection pad 6.

  The grounding or power supply conductor layer 9 located below the signal conductor layer 5 is opposed to the signal wiring conductor 5 with the insulating layer 4 interposed therebetween, and at a position corresponding to the signal external connection pad 6. A so-called solid pattern is formed on the lower surface of the insulating substrate 1 so as to have a circular opening 9 a having a diameter larger than the external connection pad 6 by about 100 to 300 μm. The opening 9 a is for maintaining good electrical insulation between the signal external connection pad 6 and the ground or power source conductor layer 9. A so-called stripline structure is formed by the signal wiring conductor 5 and the upper and lower grounding or power supply conductor layers 8 and 9 so that the signal wiring conductor 5 is electromagnetically shielded from above and below and the characteristic impedance is a predetermined value. Adjusted to

  The ground or power source conductor layer 10 located in the same layer as the signal wiring conductor 5 surrounds both sides of the signal wiring conductor 5 with a predetermined width of 10 to 50 μm and is located at a position corresponding to the signal external connection pad 6. A so-called solid pattern is formed between the insulating layers 3 and 4 so as to have a circular opening 10a having a diameter larger than the signal external connection pad 6 by about 100 to 300 μm. The opening 10a is for preventing an unnecessary capacitance component from being formed between the grounding or power supply conductor layer 10 and the signal external connection pad 6. By providing the opening 10a, a signal is provided. It is possible to reduce signal reflection at the external connection pad 6. The ground or power conductor layer 10 and the signal wiring conductor 5 form a so-called coplanar line structure, and the signal wiring conductor 5 is also electromagnetically shielded from the left and right, and the characteristic impedance is a predetermined value. Adjusted to

  In the wiring board of this example, the signal wiring conductor 5 is grounded on the upper and lower layers or the power supply conductor layers 8 and 9 so as to face the signal wiring conductor 5 and extend inside the opening 8a or 9a. Band-shaped protrusions 8b and 9b are formed. These projecting portions 8b and 9b face the signal wiring conductor 5 with the insulating layer 3 or 4 interposed therebetween, so that the characteristic impedance in the portion extending into the openings 8a and 9a of the signal wiring conductor 5 increases rapidly. This is a portion that extends into the openings 8a and 9a of the signal wiring conductor 5 by forming a capacitance component between the projections 8b and 9b and the signal wiring conductor 5. A sudden increase in characteristic impedance at is prevented. Therefore, according to the wiring board of this example, even if a high-frequency signal exceeding 25 GHz is propagated to the signal wiring conductor 5, the reflection loss and insertion loss of the signal are reduced, whereby the high-frequency signal is extremely efficiently transmitted. Can be transmitted.

  The protrusion 8b of the upper grounding or power supply conductor layer 8 preferably has a width in the range of 20 to 60 μm, which is about 10 μm wider than the width of the signal wiring conductor 5, and there is no signal in the opening 8 a. It is preferable that it extends to a position 100 to 200 μm before the end of the through-conductor 7 for use. On the other hand, the protrusion 9b of the grounding or power supply conductor layer 9 in the lower layer preferably has a width in the range of 20 to 60 μm, which is about 10 μm wider than the width of the signal wiring conductor 5. It is preferable that the external connection pad 6 extends to a position approaching about 20 to 50 μm.

  Here, FIGS. 5A and 5B are graphs showing frequency characteristics with respect to signal reflection and transmission in a simulation when an example of the embodiment of the present invention and the related art corresponding thereto are modeled. In the model according to an example of the embodiment of the present invention, in the wiring board shown in FIG. 1, the thickness of the insulating plate 2 is 400 μm, the relative dielectric constant of each of the insulating layers 3 and 4 is 3.34, the thickness is 33 μm, the signal The wiring conductor 5 has a width of 28 μm, a thickness of 15 μm, the diameter of the land 5a at the tip portion is 120 μm, the diameter of the signal external connection pad 6 is 620 μm, the thickness is 15 μm, and the thickness of the upper grounding or power supply conductor layer 8 21 μm, the width of the protrusion 8 b is 40 μm, the length is 200 μm, the thickness of the underlying ground or power supply conductor layer 9 is 15 μm, the width of the protrusion 9 a is 40 μm, the length is 50 μm, and the openings 8 a, 9 a, 10 a The case where the diameter was 820 μm was modeled. Moreover, as a model of a prior art, the case where the protrusions 8b and 9b in the model according to the example of the embodiment of the present invention described above were deleted was modeled, and each was simulated by an electromagnetic simulator.

  FIG. 3A shows a graph of the frequency characteristic of the reflection loss viewed from the signal external connection pad 6, and FIG. 3B shows a graph of the frequency characteristic of the insertion loss viewed from the signal wiring conductor 5. In these graphs, the frequency characteristic indicated by a solid line is a result of simulating a model according to an example of the embodiment of the present invention, and the frequency characteristic indicated by a broken line is a result of simulating a model according to the prior art. As shown in FIGS. 3A and 3B, the reflection loss and the transmission loss of the model according to the example of the embodiment of the present invention are the same as the model according to the prior art since the frequency of the signal exceeds 25 GHz. It has decreased compared to. Therefore, according to an example of the embodiment of the present invention, even if a high frequency signal exceeding 25 GHz is propagated to the signal wiring conductor, the reflection loss and insertion loss of the signal are reduced, thereby making the high frequency signal extremely efficient. It turns out that it can transmit well.

  As mentioned above, although an example of embodiment in the wiring board of this invention was demonstrated, the wiring board of this invention is not limited to the example of embodiment mentioned above, If it is a range which does not deviate from the summary of this invention, it will be various. Can be changed. For example, in the above-described embodiment, the protrusions 8b and 9b are provided on both the upper and lower grounds of the signal wiring conductor 5 and the power supply conductor layers 8 and 9, but only one of the protrusions 8b or 9b is provided. May be provided.

DESCRIPTION OF SYMBOLS 1 Insulating substrate 2 Insulating board 3 Upper insulating layer 4 Lower insulating layer 5 Signal wiring conductor 6 Signal external connection pad 7 Signal through conductor 8 Upper layer ground or power source conductor layer 8a Upper layer ground or power source conductor layer Opening 8b of the upper layer Ground or protrusion 9 of the power conductor layer 9 Lower ground or power conductor layer 9a Opening 9b of the upper layer or power conductor layer Upper ground or protrusion of the power conductor layer

Claims (1)

An insulating substrate formed by laminating a plurality of insulating layers including an upper insulating layer and a lower insulating layer stacked on the lower surface of the upper insulating layer, and a signal external connection pad deposited on the lower surface of the insulating substrate And an upper grounding or power source conductor layer having a first opening larger than the signal external connection pad at a position corresponding to the signal external connection pad. And a lower grounding or power supply conductor layer having a second opening larger than the signal external connection pad at a position corresponding to the signal external connection pad. And between the upper insulating layer and the lower insulating layer so as to face the upper ground or power conductor layer and the lower ground or power conductor layer, and one end thereof External connection pad for signal A strip-shaped signal wiring conductor extending to a corresponding position and at least the lower insulating layer are provided so as to connect the one end of the signal wiring conductor and the signal external connection pad. In the wiring board having a signal through conductor, at least one of the upper-layer ground or power-supply conductor layer and the lower-layer ground or power-supply conductor layer faces the signal wiring conductor and the first opening Alternatively, a wiring board having a band-shaped protrusion extending inside the second opening.

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