JP2004266180A - Wiring board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable accurate propagation of a predetermined signal to a signal wiring conductor by relaxing the occurrence of reflection noise, the mismatch of characteristic impedance, or self resonance caused by the unwanted reflection of electromagnetic wave. <P>SOLUTION: Land conductors 3 and pads 7 for external connection, which are provided on the lower side to be electrically connected with each other by signal wiring conductors 5, are located in an upper and lower positional relationship so as not to be overlapped with each other. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a wiring board for mounting electronic components such as semiconductor elements.
[0002]
[Prior art]
In general, modern electronic devices are required to be small, thin, lightweight, high-performance, high-performance, high-quality, and high-reliable, as represented by mobile communication devices. Electronic devices to be used are also required to be smaller and higher in density. For this reason, there is a demand for smaller, thinner, and more multi-terminal wiring boards that constitute electronic devices. To achieve this, the wiring width of signal wiring conductors and the like on the wiring board has been reduced and the wiring width has been reduced. Higher-density wiring has been achieved by reducing the spacing and further increasing the number of wiring layers by interposing an insulating layer therebetween.
[0003]
As a wiring board capable of such high-density wiring, a wiring board manufactured by employing a build-up method is known. The wiring board manufactured by this build-up method is, for example, as shown in FIG. 2, formed by impregnating a thermosetting resin such as an epoxy resin into a reinforcing material such as glass cloth or aramid non-woven fabric, and extending from the upper surface to the lower surface. An insulating substrate 11 having a plurality of through holes 11a formed therein, a through conductor 12 formed of a plated conductor layer such as copper plating adhered in the through holes 11a of the insulating substrate 11, Land conductors 13 respectively attached to the upper and lower surfaces of the insulating substrate 11 so as to be connected to the insulating substrate 11, and a plurality of insulating layers 14 made of a thermosetting resin such as epoxy resin laminated on the upper and lower surfaces of the insulating substrate 11. A wiring conductor 15 which is electrically connected to the land conductors 13 on the upper and lower surfaces of the insulating substrate 11 and is led out to the upper surface of the insulating layer 14 on the upper surface side and the lower surface of the insulating layer 14 on the lower surface side; An electronic component connection pad 16 attached to the upper surface of the edge layer 14 and electrically connected to the wiring conductor 15, and an electronic component connection pad 16 attached to the lower surface of the lower insulating layer 14 and electrically connected to the wiring conductor 15. And an external connection pad 17.
[0004]
In this wiring board, a plurality of through holes 11a are formed from the upper surface to the lower surface of the insulating substrate 11 by drilling or laser processing, and the through conductors 12 are formed on the inner surfaces of the through holes 11a by electroless plating and electrolytic plating. Then, the inside of the through-hole 11a is filled with a filler such as a thermosetting resin, and the land conductor 13 is formed on the upper and lower sides by electroless plating and electrolytic plating. A first insulating layer 14 is laminated, a through hole is formed in the insulating layer 14, and a wiring conductor 15 is formed on the upper and lower surfaces of the insulating layer 14 and the inner surface of the through hole by electroless plating and electrolytic plating. Next, the next insulating layer 14 and the wiring conductor 15 are formed on the upper and lower sides, and finally, electronic components are connected to the upper surface of the insulating layer 14 by electroless plating and electrolytic plating. The use pad 16 are fabricated by forming an external connection pad 17 on the lower surface.
[0005]
The wiring conductors 15 in such a wiring board are functionalized as signal, ground, and power wiring conductors depending on the application.
Of these, the signal wiring conductor functions as a conductive path for transmitting an electric signal between an electronic component such as a semiconductor element and an external electric circuit board, and the grounding wiring conductor and the power supply wiring conductor are It has a function as a supply path for supplying a ground potential and a power supply potential to the electronic components mounted on the wiring board, and also has an electromagnetic shielding function for a signal wiring conductor and a characteristic impedance adjusting function.
[0006]
Then, the electronic component is mounted such that its electrode is connected to the electronic component connection pad 16 via solder, and the external connection pad 17 is connected to the wiring conductor of the external electric circuit board via solder. The mounted electronic components are electrically connected to the external electric circuit.
[0007]
[Patent Document 1]
Japanese Patent Application Laid-Open No. 2002-359469
[Problems to be solved by the invention]
However, in such a conventional wiring board, when a signal propagated to the signal wiring conductor is a high-frequency signal of, for example, 10 GHz or more, unnecessary reflection noise generated in the signal wiring conductor becomes large, and therefore, it is mounted. There is a problem that a malfunction occurs in the electronic component.
[0009]
The inventor of the present application has conducted intensive research and has found that an external connection pad having a large area for mounting on an external electric circuit board and a land conductor connected thereto via a signal wiring conductor are connected. Electromagnetic waves are reflected between them to form a capacitance, and a parallel resonance circuit is formed by the capacitance and an inductance of a signal wiring conductor connecting the external connection pad and the land conductor, thereby causing self-resonance. As a result, unnecessary reflection noise generated in the signal wiring conductor is increased, and the present invention has been devised.
An object of the present invention is to provide a wiring board capable of suppressing unnecessary reflection noise generated in a signal wiring conductor and allowing a mounted electronic component to operate normally.
[0010]
[Means for Solving the Problems]
The wiring board of the present invention includes an insulating substrate having a plurality of through holes formed from an upper surface to a lower surface, a through conductor formed in the through hole of the insulating substrate, Land conductors respectively attached to the upper surface and the lower surface of the insulating substrate so as to cover the holes, an insulating layer laminated at least one each on the upper surface side and the lower surface side of the insulating substrate, An electronic component connection pad attached to the upper surface of the insulating layer, an external connection pad attached to the lower surface of the lower insulating layer, and the upper and lower insulating layers, respectively. A signal, a ground, and a power supply for electrically connecting the land conductor on the upper surface and the pad for connecting electronic components, and the land conductor on the lower surface and the pad for external connection to each other. Wherein the land conductor on the lower surface side and the external connection pad electrically connected to each other via the signal wiring conductor overlap each other vertically. It is characterized in that it is arranged at a position where it is not necessary.
[0011]
According to the wiring board of the present invention, the land conductor on the lower surface side and the external connection pad, which are electrically connected to each other via the signal wiring conductor, are arranged at positions that do not vertically overlap each other. The capacitance formed between the land conductor and the external connection pad, which are electrically connected to each other via the wiring conductor, is reduced, and unnecessary reflection noise generated by self-resonance in the signal wiring conductor is suppressed. As a result, the mounted electronic components can operate normally.
[0012]
In the above configuration, the wiring board of the present invention may be arranged in parallel with the upper and lower surfaces between the land conductors on the lower surface side and the external connection pads that are electrically connected to each other via the signal wiring conductors. A distance in an appropriate direction is equal to or less than a diameter of the land conductor.
[0013]
According to the wiring board of the present invention, in the above configuration, a distance in a direction parallel to the upper and lower surfaces between the land connection on the lower surface side and the external connection pad electrically connected to each other via the signal wiring conductor. Is smaller than or equal to the diameter of the land conductor, the signal wiring conductor for connecting the land conductor on the lower surface side and the external connection pad can be shortened to reduce the inductance between the two. Can be transmitted very well.
[0014]
Further, in the wiring board according to the present invention, in the above configuration, the signal wiring conductor for electrically connecting the land conductor on the lower surface side and the external connection pad to each other is connected to an outer peripheral end of the land conductor. It is characterized by having been done.
[0015]
According to the wiring board of the present invention, in the above configuration, the signal wiring conductor that electrically connects the land conductor on the lower surface side and the external connection pad to each other is connected to the outer peripheral end of the land conductor. Can further reduce the reflection of signals on the land conductor on the lower surface side.
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
Next, the wiring board of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a sectional view showing an example of an embodiment of a wiring board of the present invention. In FIG. 1, 1 is an insulating substrate, 2 is a through conductor, 3 is a land conductor, 4 is an insulating layer, 5 is a wiring conductor, 6 is an electronic component connection pad, and 7 is an external connection pad. The wiring board of the present invention is configured. In this example, four insulating layers 4 are respectively stacked on the upper and lower surfaces of the insulating substrate 1, and a solder resist layer 8 is provided on the upper surface of the upper insulating layer 4 and the lower surface of the lower insulating layer 4. Further, an example is shown in which solder bumps 9 are joined to the electronic component connection pads 6 and the external connection pads 7.
[0017]
The insulating substrate 1 serves as a core member of the wiring board of the present invention, and is made of a resin material such as glass cloth-epoxy resin or glass cloth-bismaleimide triazine resin / glass cloth-polyphenylene ether resin / aramid fiber-epoxy resin. And has a plurality of through holes 1a from the upper surface to the lower surface. Such an insulating substrate 1 is obtained by thermosetting an insulating sheet obtained by impregnating a glass cloth or aramid fiber with an uncured thermosetting resin, and then forming a through hole 1a on the insulating sheet by drilling or laser processing from the upper surface to the lower surface. Manufactured by drilling.
[0018]
The through-hole 1a is provided with a through conductor 2 made of a copper plating layer on its inner surface and filled with a resin or the like. The through conductor 2 is a conductive path for obtaining electrical continuity between the upper and lower surfaces of the insulating substrate 1, and a copper plating layer is applied to the inner surface of the through hole 1a by a known electroless copper plating method and electrolytic plating method. It is formed by this. The inside of the through hole 1a is filled with a resin by filling the inside of the through hole 1a with the through conductor 2 attached thereto with a resin paste such as an epoxy resin and thermally curing the same.
[0019]
Further, a land conductor 3 made of a copper plating layer electrically connected to the through conductor 2 is attached to the upper and lower surfaces of the insulating substrate 1 so as to cover the through hole 1a. The land conductor 3 functions as a relay member for satisfactorily electrically connecting the through conductor 2 and a later-described wiring conductor 5, and after filling the through hole 1 a of the insulating substrate 1 with resin, the upper and lower surfaces thereof are electroless. A copper plating film is deposited by a plating method and an electrolytic plating method, and is formed by etching it into a predetermined pattern.
[0020]
The insulating layers 4 stacked on the upper and lower surfaces of the insulating substrate 1 function as insulating supporting members for supporting the plurality of wiring conductors 5 above and below the insulating substrate 1 while maintaining insulation therebetween. For example, epoxy resin, bismaleimide triazine resin, polyphenylene It is composed of a thermosetting resin such as an ether resin, an elastomer, and an inorganic insulating filler, and is located vertically from the upper surface to the lower surface of each layer on the upper surface side of the insulating substrate 1 and from the lower surface to the upper surface of each layer on the lower surface side of the insulating substrate 1. A plurality of through holes 4a for connecting the wiring conductors 5 are formed. The insulating layer 4 may contain a thermoplastic resin component capable of roughening the surface in order to improve the adhesion to the wiring conductor 5.
[0021]
Such an insulating layer 4 is formed by attaching an uncured thermosetting resin insulating film containing a solvent or the like to an epoxy resin, a thermoplastic resin, an elastomer, an inorganic insulating filler, or the like on the upper and lower surfaces of the insulating substrate 1. This is formed by thermally curing the material, drilling a through hole 4a by laser processing, and sequentially stacking the next insulating layer 4 in the same manner above and below the through hole 4a.
[0022]
A wiring conductor 5 made of a copper plating layer is formed on the upper and lower surfaces of each insulating layer 4 and on the inner surface of the through hole 4a. The wiring conductor 5 functions as a conductive path for electrically connecting a desired land conductor 3 to an electronic component connection pad 6 and an external connection pad 7 to be described later. It is divided into a signal for transmitting a signal to and from an external electric circuit (not shown), and a ground and a power supply for supplying a ground potential or a power supply potential to the electronic component.
[0023]
Each time the insulating layer 4 is formed by employing a semi-additive method or a subtractive method using an electroless plating method and an electrolytic plating method, such a wiring conductor 5 is formed on the surface of the insulating layer 4 and the through hole 4a. It is formed by depositing a copper plating layer on the inner surface in a predetermined pattern.
[0024]
If the signal wiring conductor 5 is connected to the center of the land conductor 3, an electric field spreads in the land conductor 3, whereby the outer periphery of the land conductor 3 acts as a stub to reflect the signal. Is more likely to occur. Therefore, it is preferable that the signal wiring conductor 5 be connected to the outer peripheral end of the land conductor 3, that is, the vicinity of the outer periphery including the outer periphery.
[0025]
Further, on the exposed surface of the insulating layer 4 on the upper surface, an electronic component connection pad 6 to which electrodes of the electronic component are connected via solder 9 is formed, and on the exposed surface of the insulating layer 4 on the lower surface, an external surface is formed. External connection pads 7 connected to the wiring conductors of the electric circuit board via solder 9 are formed. These electronic component connection pads 6 and external connection pads 7 are made of the same copper plating layer as the wiring conductor 5, and are formed on the upper and lower surfaces of the outermost insulating layer 4 by the same method as the wiring conductor 5, respectively. Are electrically connected to the corresponding land conductors 3 via wiring conductors 5 for power, ground, or power.
[0026]
In the wiring board of the present invention, the land conductors 3 and the external connection pads 7 which are electrically connected to each other via the signal wiring conductors 5 are arranged at positions which do not vertically overlap each other. And that is important. As described above, since the land conductors 3 and the external connection pads 7 electrically connected to each other via the signal wiring conductors 5 are arranged so as not to vertically overlap each other, the land conductors 3 and the external Since the coupling of the electromagnetic wave with the connection pad 7 is reduced and a large capacitance is not formed between the two, unnecessary reflection noise can be reduced. Therefore, even if the signal propagating through the signal wiring conductor 5 is a high-frequency signal of 10 GHz or more, it is possible to normally operate the mounted electronic component.
[0027]
Further, the distance in the direction parallel to the upper and lower surfaces of the insulating substrate 1 between the land conductor 3 on the lower surface side and the external connection pad 7 electrically connected to each other via the signal wiring conductor 5 is set to the distance of the land conductor 3. When the diameter is equal to or less than the diameter, the signal wiring conductor 5 connecting the two can be shortened to reduce the inductance, thereby increasing the characteristic impedance between the land conductor 3 and the external connection pad 7. The signal can be transmitted very well between the two. Therefore, it is preferable that the distance between the land conductors 3 connected to each other by the signal wiring conductors 5 and the external connection pads 7 in the direction parallel to the upper and lower surfaces of the insulating substrate 1 be equal to or less than the diameter of the land conductors 3. Here, the distance means not the distance between the centers of the land conductors 3 and the external connection pads 7 but the distance between the land conductors 3 and the external connection pads 7 in a direction parallel to the upper and lower surfaces of the insulating substrate 1.
[0028]
The distance between the land conductor 3 and the external connection pad 7 electrically connected to each other via the signal wiring conductor 5 in the direction parallel to the upper and lower surfaces of the insulating base 1 exceeds the diameter of the land conductor 3. Then, the line length of the signal wiring conductor 5 connecting between the two becomes long, and the inductance between them increases, so that the characteristic impedance becomes large and signal reflection easily occurs.
[0029]
The solder resist layer 8 laminated on the surface of the insulating layer 4 on the upper surface side and the lower surface side is made of, for example, an insulating material in which about 30 to 70% by mass of an inorganic powder filler such as silica or talc is dispersed in an acrylic-modified epoxy resin. Thus, it functions as a protective layer for protecting the insulating layer 4 and preventing an electrical short circuit between the electronic component connection pads 6 and between the external connection pads 7. Such a solder resist layer 8 is formed by applying a photosensitive uncured resin paste for the solder resist layer 8 to the surface of the outermost insulating layer 4 by using a roll coater method or a screen printing method. After drying, exposure and development are performed using photolithography technology to form openings for exposing the electronic component connection pads 6 and the external connection pads 7, and then these are cured by ultraviolet light and heat. It is formed. Alternatively, after an uncured resin film for the solder resist layer 8 is adhered to the surface of the outermost insulating layer 4, this is thermally cured, and then the electronic component connecting pad 6 and the external connecting pad 7 are applied. A corresponding position is irradiated with a laser beam, and the cured resin film is partially removed to form an opening for exposing the electronic component connection pad 6 and the external connection pad 7.
[0030]
Furthermore, on the surfaces of the electronic component connection pads 6 and the external connection pads 7, the electrodes of the electronic component are connected to the electronic component connection pads 6, and the external connection pads 7 are connected to the wiring conductors of the external electric circuit board. Solder bumps 9 for connection are joined, and through these solder bumps 9, the electrodes of the electronic component are electrically connected to the electronic component connection pads 6 and the external connection pads 7 and the wiring conductors of the external electric circuit board. Connected to. Such solder bumps 9 are formed by printing solder paste on the surfaces of the electronic component connection pads 6 and the external connection pads 7 and reflowing and melting the solder paste.
[0031]
Thus, according to the wiring board of the present invention, the electronic component is mounted such that its electrode is connected to the electronic component connection pad via the solder bump 9, and the external connection pad 7 is connected to the wiring of the external electric circuit board. By connecting to the conductor via the solder bump 9, the mounted electronic component is electrically connected to the external electric circuit.
[0032]
It should be noted that the present invention is not limited to the above embodiment, and various changes may be made without departing from the scope of the present invention.
[0033]
【The invention's effect】
According to the wiring board of the present invention, the land conductor on the lower surface side and the external connection pad, which are electrically connected to each other via the signal wiring conductor, are arranged at positions that do not vertically overlap each other. The capacitance formed between the land conductor and the external connection pad, which are electrically connected to each other via the wiring conductor, is reduced, and unnecessary reflection noise generated by self-resonance in the signal wiring conductor is suppressed. As a result, the mounted electronic components can operate normally.
[0034]
According to the wiring board of the present invention, the distance in the direction parallel to the upper and lower surfaces between the land conductor on the lower surface side and the external connection pad electrically connected to each other via the signal wiring conductor is set to the land. When the diameter is smaller than the diameter of the conductor, the signal wiring conductor for connecting the land conductor on the lower surface side and the external connection pad can be shortened to reduce the inductance between the two. It can be transmitted well.
[0035]
Furthermore, according to the wiring board of the present invention, when the signal wiring conductor for electrically connecting the land conductor on the lower surface side and the external connection pad to each other is connected to the outer peripheral end of the land conductor, The signal reflection on the land conductor on the lower surface side can be further reduced.
[Brief description of the drawings]
FIG. 1 is a sectional view showing an example of an embodiment of a wiring board of the present invention.
FIG. 2 is a cross-sectional view illustrating an example of a conventional wiring board.
[Explanation of symbols]
1 ... Insulating substrate 2 ... Through conductor 3 ... Land conductor 4 ... Insulating layer 5 ... Wiring conductor 6 Pad for connecting electronic components 7 Pad for connecting external

Claims (3)

An insulating substrate having a plurality of through holes formed from an upper surface to a lower surface, a through conductor formed in the through hole of the insulating substrate, and connected to the through conductor and covering the through hole. Land conductors respectively attached to the upper surface and the lower surface of the insulating substrate; insulating layers laminated at least one each on the upper surface side and the lower surface side of the insulating substrate; Electronic component connection pads, external connection pads adhered to the lower surface of the lower surface side insulating layer, and the upper surface side lands disposed on the upper surface side and the lower surface side insulating layer, respectively. A signal conductor, a ground conductor and a power conductor for electrically connecting the conductor and the electronic component connection pad, and the land conductor on the lower surface side and the external connection pad to each other. Wherein the land conductor on the lower surface side and the external connection pad electrically connected to each other via the signal wiring conductor are arranged at positions not overlapping with each other vertically. A wiring board characterized by the above-mentioned. A distance between the land conductor on the lower surface side and the external connection pad, which are electrically connected to each other via the signal wiring conductor, in a direction parallel to the upper and lower surfaces is equal to or less than a diameter of the land conductor. The wiring board according to claim 1, wherein: The signal wiring conductor that electrically connects the land conductor on the lower surface side and the external connection pad to each other is connected to an outer peripheral end of the land conductor. Item 3. The wiring board according to Item 2.

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