JP2013069730A - Wiring board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wiring board capable of efficiently transmitting a signal of a superhigh frequency on 30 GHz and over to signal wiring.SOLUTION: A wiring board comprises: a through conductor 3S penetrating through an insulation layer 1; a belt-like signal wiring 2S having a land part L covering the through conductor 3S and arranged on a surface of the insulation layer 1; and a ground conductor 2G or a power supply conductor 2P, which is arranged on the surface of the insulation layer 1 so as to surround a circumference of the signal wiring 2S leaving a predetermined space from the circumference. The signal wiring 2S comprises: a wide part W having a width wider than a diameter of the land part L and a constant space from the ground conductor 2G or the power supply conductor 2P; and a narrow part N connecting the wide part W and the land part L and having a width narrower than the diameter of the land part L and less than one fourth of a wavelength of a signal transmitted through the signal wiring 2S.

Description

  The present invention relates to a wiring board for mounting a semiconductor element.

  A small-sized wiring board for mounting a semiconductor element has a plurality of wiring conductors disposed inside and on the surface of an insulating substrate formed by laminating a plurality of insulating layers, and has a vertical conductor formed by penetrating conductors penetrating the insulating layer. It has a multilayer wiring structure in which wiring conductors are connected to each other. A plurality of semiconductor element connection pads are formed in the central portion of the upper surface of the insulating substrate to electrically connect the electrodes of the semiconductor element via solder bumps, and the wiring conductor of the external electric circuit substrate is formed on the lower surface of the insulating substrate. External connection pads that are electrically connected via solder balls are formed. These semiconductor element connection pads and external connection pads are electrically connected to each other by wiring conductors and through conductors arranged on the surface and inside of the insulating substrate.

  The wiring conductor in such a wiring board is functionalized into a signal wiring, a ground conductor, and a power supply conductor depending on applications. Among these, the signal wiring is composed of a strip-like pattern extending from the central portion to the outer peripheral portion of the insulating substrate, and functions as a line for propagating an electric signal input / output to / from the semiconductor element. In addition, the ground conductor and the power supply conductor are configured by a solid pattern that occupies a large area on the insulating layer, and function as a supply path for supplying a ground potential and a power supply potential to a semiconductor element mounted on the wiring board. Furthermore, these ground conductors and power supply conductors are provided with a predetermined interval between the signal wirings, thereby providing a predetermined characteristic impedance to the signal wirings and a function of electromagnetically shielding the signal wirings. Have. These signal wirings, ground conductors, and power supply conductors are connected to corresponding semiconductor element connection pads and external connection pads, respectively, through through conductors penetrating each insulating layer.

  Here, FIG. 4 shows examples of signal wirings, ground conductors, and power supply conductors in a conventional wiring board. FIG. 4 is a plan view partially showing a specific layer inside the wiring board, in which 11 is an insulating layer, 12S is a signal wiring, 12G is a ground conductor, and 12P is a power supply conductor. Reference numerals 13S, 13G, and 13P denote positions of through conductors connected from the upper layer of the layer shown in FIG. In the drawing, the right side corresponds to the center side of the wiring board, and the left side corresponds to the outer peripheral side.

  As shown in FIG. 4, the signal wiring 12 </ b> S is a belt-like pattern having a width of about 100 to 350, and extends on the insulating layer 11 inside the wiring board from the center to the outer periphery of the wiring board. A through conductor 13S from the upper layer is connected to the end of the signal wiring 12S on the center side of the wiring board. A high-speed signal is propagated through the signal wiring 12S. Around the signal wiring 12S, a ground conductor 12G is disposed so as to surround the signal wiring 12S with a predetermined interval. The ground conductor 12G is a solid pattern with a large area, and a large number of through conductors 13G from the upper layer are connected. As described above, the ground conductor 12G surrounds the signal wiring 12S at a predetermined interval, so that a predetermined characteristic impedance is given to the signal wiring 12S. The power supply conductor 12P has only a circular land in this layer, and is insulated from the ground conductor 12G at a predetermined interval. A through conductor 13P from the upper layer is connected to the power supply conductor 12P.

  By the way, in the connection part of signal wiring 12S and penetration conductor 13S, there is a tendency for the capacity component formed between grounding conductors 12G to become large. When the capacitance component between the signal conductor 12S and the ground conductor 12G at the connection portion between the through conductor 13S is large and a high-speed signal having a frequency of 10 GHz or more is propagated through the signal line 12S, for example, the signal line 12S and the through conductor 13S The signal is greatly reflected at the connecting portion of the signal, and the signal transmission characteristics are greatly impaired. Accordingly, in the vicinity of the connection portion between the signal wiring 12S and the through conductor 13S, the signal transmission characteristics are improved by narrowing the width of the signal wiring 12S and narrowing the distance from the ground conductor 12G. Yes.

  However, in order to connect the signal wiring 12S and the through conductor 13S satisfactorily, it is necessary to provide a land portion L that is about 50 to 100 μm larger than the diameter of the through conductor 13S at the connection portion of the signal wiring 12S with the through conductor 13S. A large capacitance component is formed between the land portion L and the ground conductor 12G. Therefore, it is conceivable to reduce the capacitance component between the signal wiring 12S and the ground conductor 12G in the vicinity of the connection portion of the signal wiring 12S with the through conductor 13S by increasing the distance between them. However, when other through conductors 13G and 13P are arranged in the vicinity of the through conductor 13S connected to the signal wiring 12S, the signal wiring 12S in the vicinity of the connection portion of the signal wiring 12S with the through conductor 13S and The interval with the ground conductor 12G cannot be increased. As a result, when an ultrahigh-speed signal having a frequency of, for example, 30 GHz or more is propagated through the signal wiring 12S, the characteristic impedance due to the excessive capacitance component between the signal wiring 12S and the ground conductor 12G at the connection portion of the through conductor 13S. Due to the decrease, the reflection of the signal at the connection portion between the signal wiring 12S and the through conductor 13S is increased, and it is difficult to favorably propagate an ultrahigh-speed signal having a frequency of 30 GHz or more.

JP 2003-133814 A

  An object of the present invention is to provide a signal at a connection portion between a signal wiring and a through conductor in a wiring board in which a through conductor is connected to one end of a strip-shaped signal wiring surrounded by a ground conductor or a power supply conductor at a predetermined interval. It is an object of the present invention to provide a wiring board capable of reducing reflection of light and efficiently transmitting a signal of ultrahigh frequency of 30 GHz or more to a signal wiring.

  The wiring board of the present invention includes a through conductor penetrating the insulating layer, a strip-shaped signal wiring disposed with a land portion covering the through conductor on the surface of the insulating layer, and a periphery of the signal wiring on the surface of the insulating layer. And a grounding conductor or a power supply conductor disposed so as to surround the circuit board at a predetermined interval, wherein the signal wiring has a width wider than the diameter of the land portion and the grounding conductor or the power supply conductor. A wide portion having a constant distance from the conductor, a width between the wide portion and the land portion, a width smaller than the diameter of the land portion, and a length less than a quarter of the wavelength of the signal propagating through the signal wiring And having a narrow width portion.

  According to the wiring board of the present invention, the width between the wide portion of the signal wiring and the land is narrower than the land diameter and less than a quarter of the wavelength of the signal propagated through the signal wiring. Since the part is provided, it is possible to suppress the reflection of the signal by supplementing the decrease in the characteristic impedance caused by the excessive capacitance component at the connection part between the signal wiring and the through conductor with the inductance component formed by the narrow part. it can. Therefore, it is possible to efficiently transmit a signal with an ultrahigh frequency of 30 GHz or more to the signal wiring.

FIG. 1 is a schematic cross-sectional view showing an example of an embodiment of a wiring board according to the present invention. FIG. 2 is a main part schematic plan view showing an example of the embodiment of the wiring board of the present invention. FIG. 3 is a graph showing a result of simulation using an electromagnetic field simulator for an analysis model corresponding to the wiring board of the present invention and the conventional wiring board. FIG. 4 is a schematic plan view of an essential part showing an example of a conventional wiring board.

  Next, an example of an embodiment of the wiring board according to the present invention will be described with reference to FIGS. As shown in FIG. 1, the wiring board of this example has a plurality of wiring conductors 2 disposed between a surface of an insulating board 1A formed by laminating a plurality of insulating layers 1 and each insulating layer 1, and is insulated. A multilayer wiring structure is formed in which upper and lower wiring conductors 2 are connected to each other by a through conductor 3 that penetrates through the layer 1. Further, a solder resist layer 4 having an opening for exposing a part of the wiring conductor 2 is deposited on the upper and lower surfaces.

  The insulating layer 1 is made of an electrically insulating material obtained by impregnating a glass cloth with a thermosetting resin such as an allyl-modified polyphenylene ether resin, and has a thickness of about 100 to 350 μm. Such an insulating layer 1 is made of glass cloth with a cross-linking agent such as allyl-modified polyphenylene ether resin and triallyl isocyanurate and dialkyl peroxides (organic peroxide) such as perhexine 25B and perbutyl D / perbutyl P. It is formed by preparing an uncured prepreg impregnated with a thermosetting resin composition composed of a polymerization initiator and applying necessary processing to the prepreg, and then laminating a plurality of the prepregs and thermosetting them.

  The wiring conductor 2 is made of, for example, copper foil and has a thickness of about 5 to 20 μm. Such a wiring conductor 2 is bonded to the surface of a transfer base sheet made of a resin such as polyethylene terephthalate in a state where the copper foil can be peeled off, and then the copper foil is predetermined using a well-known photolithography technique. This pattern is etched, the etched copper foil is pressed and embedded on the surface of the prepreg for the insulating layer 1, and then the transfer equipment sheet is removed.

  The through conductor 3 is made of, for example, a hardened metal paste containing a metal powder made of an alloy of tin, silver, bismuth, and copper, and has a diameter of about 50 to 100 μm. Such a through conductor 3 is formed, for example, by drilling a through hole having a diameter of about 50 to 100 μm in the prepreg for the insulating layer 1 by laser processing, and made of an alloy of tin, silver, bismuth, and copper in the through hole. It is formed by filling a metal paste obtained by kneading a metal powder and a liquid crosslinking agent such as triallyl isocyanurate by a screen printing method and thermally curing it together with the prepreg for the insulating layer 1.

  The solder resist layer 4 is made of a thermosetting resin having photosensitivity such as an acrylic-modified epoxy resin, and has a thickness of about 10 to 20 μm. Such a solder resist layer 4 is formed by applying a photosensitive thermosetting resin composition paste on the upper and lower surfaces of the insulating substrate 1A on which the wiring conductor 2 is disposed to a thickness of 10 to 20 μm and the wiring conductor 2. The film is exposed and developed so as to have an opening that exposes a part of the film, and then thermally cured.

  In the central portion of the upper surface of the insulating substrate 1A, a plurality of semiconductor element connection pads 5 to which the electrodes T of the semiconductor elements S are connected via solder bumps are arranged in a grid, for example. The semiconductor element connection pad 5 is formed by exposing a part of the uppermost wiring conductor 2 in a circular shape from the opening of the solder resist layer 4 and has a diameter of about 50 to 100 μm. In addition, on the lower surface of the insulating substrate 1A, a plurality of external connection pads 6 connected to an external electric circuit board (not shown) via solder balls are arranged, for example, in a lattice pattern. The external connection pad 6 is formed by exposing a part of the lowermost wiring conductor 2 in a circular shape from the opening of the solder resist layer 4 and has a diameter of about 300 to 1000 μm. A predetermined number of these semiconductor element connection pads 5 and external connection pads 6 are electrically connected to each other via the wiring conductor 2 and the through conductor 3.

  The wiring conductor 2 is functionalized into a signal wiring, a ground conductor, and a power supply conductor depending on applications. Among these, the signal wiring is configured by a strip-like pattern extending from the central portion to the outer peripheral portion of the insulating substrate 1A, and functions as a line for propagating an electric signal input / output to / from the semiconductor element S. In addition, the ground conductor and the power supply conductor are configured by a solid pattern that occupies a large area on the insulating layer 1 and function as a supply path for supplying a ground potential and a power supply potential to the semiconductor element S mounted on the wiring board. Furthermore, these ground conductors and power supply conductors are provided with a predetermined interval between the signal wirings, thereby providing a predetermined characteristic impedance to the signal wirings and a function of electromagnetically shielding the signal wirings. Have.

  Here, FIG. 2 shows an example of the signal wiring, the ground conductor, and the power supply conductor in this example. FIG. 2 is a plan view partially showing a specific insulating layer 1 and wiring conductor 2 inside the insulating substrate 1A. 2S is a signal wiring, 2G is a ground conductor, and 2P is a power supply conductor. Reference numerals 3S, 3G, and 3P denote positions of the through conductors 3 connected from the upper layer of the layer shown in FIG. In the drawing, the right side corresponds to the center side of the wiring board, and the left side corresponds to the outer peripheral side.

  As shown in FIG. 2, the signal wiring 2 </ b> S has a generally band-like pattern, and extends on the insulating layer 1 inside the insulating substrate 1 </ b> A from the central portion to the outer peripheral portion of the wiring substrate. A high-speed signal is propagated through the signal wiring 2S. A circular land portion L is provided at an end of the signal wiring 2S on the central side of the insulating substrate 1A, and a through conductor 3S from an upper layer is connected to the land portion L. The land portion L has a diameter approximately 50 to 100 μm larger than the diameter of the through conductor 3S from the upper layer, and completely covers the lower end of the through conductor 3S from the upper layer.

  A narrow portion N is connected to the land portion L. The width of the narrow portion N is narrower than the diameter of the land portion L and is about 1/4 to 3/4 of the diameter of the land portion L. The length of the narrow portion N is the wavelength of the signal propagating through the signal wiring 2S. It is less than a quarter of the length. The narrow portion N thus acts as an inductance component because the width is as narrow as about one-fourth to three-fourths of the diameter of the land portion L.

  A wide portion W is connected to the narrow portion N. The wide portion W occupies the main part of the signal wiring 2S, and the width thereof is wider than the diameter of the land portion L and is about 100 to 350 μm. As described above, since the width of the wide portion W, which is the main part of the signal wiring 2S, is as wide as about 100 to 350 μm, an ultrahigh frequency signal having a frequency of 30 GHz or more can be propagated to the signal wiring 2 without significant attenuation.

  Around the signal wiring 2S, a ground conductor 2G is disposed so as to surround the signal wiring 2S with an interval of 50 to 350 μm. The ground conductor 2G is a solid pattern with a wide area, and a large number of through conductors 3G from the upper layer are connected. As described above, the ground conductor 2G surrounds the signal wiring 2S with a predetermined interval, so that a predetermined characteristic impedance is given to the signal wiring 2S. The distance between the ground conductor 2G and the signal wiring 2S is determined in consideration of the dielectric constant and thickness of the insulating layer 1, the width and thickness of the signal wiring 2S, the distance from the conductor layer 2 of other layers, and the like. The characteristic impedance is appropriately determined so as to have a predetermined value. The power supply conductor 2P has only a circular land in this layer, and is insulated from the ground conductor 2G with a predetermined interval. A through conductor 3P from the upper layer is connected to the power supply conductor 2P.

  In the present invention, the narrow portion N narrower than the diameter of the land portion L is between the land portion L to which the through conductor 3S is connected and the wide portion W which is the main portion of the signal wire 2S. It is important that the length of the signal propagating through 2S is less than a quarter of the wavelength. By forming such a narrow portion N, the narrow portion N reduces the characteristic impedance due to the excessive capacitance component formed between the land portion L and the through conductor 3S and the ground conductor 2G. It can be supplemented with an inductance component. Thereby, even if the frequency of the signal propagated to the signal wiring 2S is an ultrahigh frequency of 30 GHz or more, reflection of the signal can be suppressed and the signal can be efficiently propagated to the signal wiring 2S. Further, since the length of the narrow portion N is less than a quarter of the wavelength of the signal propagating through the signal wiring 2S, it is effectively prevented that the signal is reflected by the narrow portion N. The

  If the width of the narrow portion N is less than a quarter of the diameter of the land portion L, it is difficult to accurately form the narrow portion N, and the signal wiring 2S is disconnected at the narrow portion N. When the risk increases and exceeds three-quarters, a sufficient inductance component cannot be applied to the narrow portion N. Therefore, the width of the narrow portion N is preferably in the range of ¼ to ¼ of the diameter of the land portion L. Further, when the length of the narrow portion N is equal to or more than one quarter of the wavelength of the signal propagating through the signal wiring 2S, signal reflection occurs due to an increase in impedance in the narrow portion N, and the signal wiring It becomes difficult to efficiently propagate the signal to 2S. Therefore, the length of the narrow portion N is specified to be less than a quarter of the wavelength of the signal propagating through the signal wiring 2S.

  Here, an analysis model corresponding to the present invention in which the wiring board shown in FIG. 2 is modeled and an analysis model corresponding to the conventional technique in which the wiring board shown in FIG. The simulation result is shown in FIG. In FIG. 3, the graph indicated by the solid line is the reflection characteristic of the analysis model corresponding to the present invention, and the graph indicated by the broken line is the reflection characteristic of the analysis model corresponding to the prior art. As can be seen from FIG. 3, in the analysis model corresponding to the prior art, the reflection loss exceeds −15 dB at a frequency lower than 30 GHz, and it is understood that a signal of 30 GHz or higher cannot be propagated satisfactorily. On the other hand, in the analysis model corresponding to the present invention, the reflection loss is much less than −15 dB even at 30 GHz, and it is possible to propagate even a very high frequency signal of 30 GHz or higher.

  Thus, according to the wiring board of the present invention, there is provided a wiring board capable of reducing signal reflection at the connection portion between the signal wiring and the through conductor and efficiently transmitting a signal of ultrahigh frequency of 30 GHz or more to the signal wiring. Can be provided. The present invention is not limited to an example of the above-described embodiment, and various modifications can be made without departing from the gist of the present invention. For example, in the above example, the signal wiring 2S is disposed so as to be surrounded by the ground conductor 2G. However, the ground conductor 2G and the power supply conductor 2P are replaced, and the signal wiring 2S is disposed so as to be surrounded by the power supply conductor 2P. May be.

DESCRIPTION OF SYMBOLS 1 Insulation layer 2S Signal wiring 2G Ground conductor 2P Power supply conductor 3 Through conductor L Land part N Narrow part W Wide part

Claims (1)

  A penetrating conductor penetrating the insulating layer, a strip-shaped signal wiring disposed with a land portion covering the penetrating conductor on a surface of the insulating layer, and a predetermined periphery around the signal wiring on the surface of the insulating layer A wiring board comprising a grounding conductor or a power supply conductor disposed so as to surround the space, wherein the signal wiring has a width wider than the diameter of the land portion and the grounding conductor or the power supply. A wide portion having a constant distance from the conductor, and a connection between the wide portion and the land portion, a width smaller than the diameter of the land portion and a quarter of the wavelength of the signal propagating through the signal wiring A wiring board having a narrow portion having a length of less than one.

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