JP5455216B2 - Wiring board - Google Patents

Description

  The present invention relates to a wiring substrate in which a conductor pattern constituting an inductor is formed on the surface or inside of an insulating substrate.

  Conventionally, as shown in FIGS. 2 (a) and 2 (b), a high-frequency wiring board in which an inductor 12 as a passive element is built in an insulating substrate 11 formed by laminating a plurality of insulating layers. Are known. As the inductor 12, an inductor 12 </ b> A having a coil pattern in which an elongated strip-like conductor pattern is spirally wound between the insulating layers of the insulating substrate 11 in a plan view, or a thin strip-shaped conductor pattern in plan view between the insulating layers of the insulating substrate 11. A meander pattern inductor 12B arranged in a zigzag pattern is used.

  However, the coil pattern and the meander pattern constituting the inductor 12 occupy a large area in a plan view inside the insulating substrate 11 in order to obtain a large inductance. This hinders downsizing of the wiring board. In addition, since the coil patterns and meander patterns constituting the inductor 12 are arranged in close proximity to each other, a large amount of excess capacitance component is formed between the adjacent patterns. If a large amount of excess capacitance component is formed between the patterns constituting the inductor 12, the self-resonant frequency of the inductor 12 is lowered. When the self-resonant frequency of the inductor 12 decreases, the frequency band in which the inductor 12 functions as an inductor element also decreases. This is due to the property that the inductor 12 functions not as an inductor element but as a capacitive element in a frequency band exceeding the self-resonant frequency of the inductor 12. As a result, the high-frequency active element mounted on the wiring board cannot be operated normally. Therefore, in order to be able to use the wiring board in which the inductor is built in a high frequency band, it is necessary to increase the self-resonance frequency of the inductor.

JP-A-9-139573

  An object of the present invention is that, in a wiring board in which an inductor composed of a strip-like conductor pattern is formed on the surface or inside of an insulating substrate, the conductor pattern forming the inductor occupies a large area on the surface or inside of the insulating substrate. The size of the wiring board can be reduced, and the capacitance component formed between the self-patterns in the inductor is small, so that the self-resonance frequency of the inductor is high, and the mounted active elements are normal up to a high frequency band. An object of the present invention is to provide a wiring board that can be operated in a simple manner.

In the wiring board of the present invention, a plurality of wiring conductors are formed on the surface and inside of an insulating board formed by laminating a plurality of insulating layers, and connected to a part of the wiring conductor on or inside the insulating board. In the wiring board formed by forming an inductor composed of the elongated strip-shaped conductor pattern, the conductor pattern is wound with a number of turns of one turn or less so that the outer peripheral portion of the insulating substrate does not overlap the wiring conductor vertically. It is characterized by being formed by only one pattern .

According to the wiring board of the present invention, the inductor is composed of an elongated strip-like conductor pattern provided so that the outer peripheral portion of the insulating substrate is wound with a number of turns of one turn or less. Therefore, the conductor pattern constituting the inductor is insulated. It does not occupy a large area on the surface or inside of the substrate, and it is possible to secure a wide space for the magnetic flux to pass inside the wound pattern, so that a large inductance can be obtained accordingly. In addition, the conductor pattern that constitutes the inductor is formed by only one pattern that is wound with the number of turns of one turn or less so that the outer peripheral portion of the insulating substrate does not overlap with the wiring conductor. Since the extra capacitance component formed between them and the capacitance component between the self pattern and the wiring conductor connected thereto are small, the self-resonance frequency of the inductor can be increased. Therefore, according to the wiring board of the present invention, it is possible to provide a small-sized wiring board capable of normally operating the mounted active element up to a high frequency band.

(A) is a simplified sectional view showing an example of an embodiment of a wiring board of the present invention, and (b) is a simplified plan view showing the inside of the wiring board shown in (a). (A) is a simplified sectional view showing an example of a conventional wiring board, and (b) is a simplified plan view showing the inside of the wiring board shown in (a).

  Next, an example of an embodiment of the wiring board according to the present invention will be described with reference to FIGS. The wiring board of this example includes an insulating substrate 1 having a mounting portion 1a for mounting a semiconductor element in the center of the upper surface, and a lower surface of the insulating substrate 1 from the mounting portion 1a of the insulating substrate 1 through the inside of the insulating substrate 1. A wiring conductor 2 to be led out and an inductor 3 formed between insulating layers in the outer peripheral portion of the insulating substrate 1 are provided.

  The insulating substrate 1 has a thickness of 10 to 10 made of a ceramic material such as alumina, aluminum nitride, mullite, or glass ceramic, or a resin material containing a thermosetting resin such as an epoxy resin, a bismaleimide triazine resin, or an allyl-modified polyphenylene ether resin. The external electric circuit board is formed by laminating several to several tens of insulating layers of 1000 μm, the semiconductor element is mounted on the mounting part 1a on the upper surface side, and the lower surface is opposed to the mounting surface of the external electric circuit board. Implemented above. The insulating substrate 1 has a size of several to several tens of mm on one side and a thickness of several hundred to several thousand μm.

  The wiring conductor 2 is a conductive path for electrically connecting a semiconductor element mounted on the insulating substrate 1 to an external electric circuit board, and an electrode terminal of the semiconductor element is connected to a portion led to the mounting portion 1a of the insulating substrate 1 A semiconductor element connection pad 2a to be electrically connected is formed, and an external connection pad 2b to be electrically connected to a wiring conductor of the external electric circuit board is formed at a portion led out to the lower surface of the insulating substrate 1. Yes. Such a wiring conductor 2 is made of a sintered metal powder such as tungsten, molybdenum, or copper if the insulating substrate 1 is made of a ceramic material, and is made of copper if the insulating substrate 1 is made of a resin material. Consists of foil and copper plating layer. The thickness of the wiring conductor 2 is several to several tens of μm. In FIG. 1A, only a part of the wiring conductor 2 is schematically shown.

  As shown in FIG. 1B, the inductor 3 is formed in an elongated strip-like conductor pattern so that the outer peripheral portion of the insulating substrate 1 is wound with a number of turns equal to or less than one turn. It is electrically connected to a part. The inductor 3 is made of the same material with the same thickness as that of the wiring conductor 2, and by providing such an inductor 3, a filter, an impedance matching circuit, a DC-DC converter, or the like can be formed in the wiring board. In FIG. 1B, only the inductor 3 is schematically shown, and the wiring conductor 2 is formed in a necessary pattern in the central portion of the insulating substrate 1 surrounded by the inductor 3.

  In the present invention, the conductor pattern of the inductor 3 is provided so that the outer peripheral portion of the insulating substrate 1 does not overlap with the wiring conductor 2 so as to be wound with a number of turns equal to or less than one turn. The conductor pattern of the inductor 3 and the wiring conductor 2 are connected in a layer different from the pattern, which is important. Thus, since the elongated strip-like conductor pattern of the inductor 3 is provided so as to wind the outer peripheral portion of the insulating substrate 1, the inductor 3 does not occupy a large area inside the insulating substrate 1, Accordingly, a small wiring board can be obtained. In addition, since a large space for the magnetic flux to pass inside the winding pattern can be secured, a large inductance can be obtained accordingly. Further, the conductor pattern constituting the inductor 3 is wound with a number of turns equal to or less than one turn so that the outer peripheral portion of the insulating substrate 1 does not overlap with the wiring conductor 2 and is wired in a layer different from the conductor pattern of the inductor 3. Since it is connected to a part of the conductor 2, an extra capacitance component formed between its own conductor patterns and a capacitance component between its own conductor pattern and the wiring conductor 2 connected thereto are small. Therefore, the self-resonant frequency of the inductor 3 can be increased. If the self-resonant frequency of the inductor 3 is high, the inductor 3 can function as an inductor up to the higher frequency. Therefore, according to the wiring board of the present invention, it is possible to provide a small-sized wiring board capable of normally operating the mounted active element up to a high frequency band.

  By the way, as an analysis model corresponding to the present invention, the inventor of the present invention has an elongated strip shape having a width of 25 μm, a thickness of 15 μm, and a length of 13.3 mm in an insulating substrate having a size of 2 mm × 6 mm, a thickness of 81 μm, and a relative dielectric constant of 3.38. An analysis model modeling the case where the conductor pattern is provided in a pattern in which the outer periphery of the insulating substrate is wound only once so that the distance from the outer periphery of the insulating substrate is 250 μm, and the same insulating substrate as in this analysis model A conventional technique that models a case where a strip-shaped conductor pattern having the same width, thickness and length is provided as a coiled pattern wound four times in a square spiral shape so that the distance between the patterns is 25 μm. According to the simulation result by the electromagnetic simulator using the corresponding analysis model, the solution corresponding to the present invention is used in the frequency band of 0.1 to 2 GHz. It is possible to better model get about 2nH high inductance, self-resonance frequency also become a approximately 1.2GHz high.

  By the way, when the conductor pattern forming the inductor 3 is formed so as to wrap around a range outside 500 μm from the outer periphery of the insulating substrate 1, the moisture penetrates from the insulating layer at the outer peripheral edge of the insulating substrate 1 to the inductor 3. When the risk of corrosion is increased and the inner periphery of the insulating substrate 1 is wound more than 1000 μm, a wasteful area is widely formed on the insulating substrate 1 on the outer peripheral side of the inductor 3. Therefore, it is difficult to reduce the size of the wiring board. Therefore, the conductor pattern forming the inductor 3 is preferably provided so as to wind in the range of 500 to 1000 μm from the outer periphery of the insulating substrate 1. Further, if the width of the thin strip-shaped conductor pattern forming the inductor 3 is less than 10 μm, there is a high risk of disconnection of the conductor pattern, and if it exceeds 100 μm, it is difficult to obtain a high inductance. . Therefore, the elongated strip-shaped conductor pattern forming the inductor 3 preferably has a width in the range of 10 to 100 μm. Furthermore, if the length of the thin strip-shaped conductor pattern forming the inductor 3 is less than 1 mm, it is difficult to obtain sufficient inductance, and if it exceeds 50 mm, the self-resonant frequency is low. Therefore, the elongated strip-shaped conductor pattern forming the inductor 3 preferably has a length in the range of 1 to 50 mm.

  The present invention is not limited to an example of the above-described embodiment, and it goes without saying that various modifications can be made without departing from the gist of the present invention. For example, in the above-described embodiment, the elongated strip-shaped conductor pattern that forms the inductor 3 is formed inside the insulating substrate 1. However, the strip-shaped conductor pattern that forms the inductor 3 is formed on the surface of the insulating substrate 1. It may be.

1 Insulating board 2 Wiring conductor 3 Inductor

Claims (1)

A plurality of wiring conductors are formed on the surface and inside of an insulating substrate formed by laminating a plurality of insulating layers, and a strip-like conductor pattern connected to a part of the wiring conductor on the surface or inside of the insulating substrate. In the wiring board formed by forming the inductor, the conductor pattern is only one pattern in which the outer peripheral portion of the insulating substrate is wound with the number of turns of one turn or less so as not to overlap the wiring conductor. A wiring board which is formed .

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