JPH08172252A - Circuit board - Google Patents

Abstract

PURPOSE: To provide a circuit board which can display a prescribed filter characteristic and a prescribed resonance characteristic by a method wherein the attenuation of a signal propagated in an inductor line can be made extremely small. CONSTITUTION: A circuit board A is composed in such a way that an inductor line 9 which is faced with a grounding conductor 5 or a power-supply conductor 6 is applied to, and formed on, the surface of an insulating base body 1 which comprises the grounding conductor 5 and the power-supply conductor 6 at the inside. The inductor line 9 is formed of one pair of metallized lines 7a, 7b which are run in parallel so as to be mutually close and of a plated metal layer 8 which covers the insulating base body 1 between the pair of metallized lines 7a, 7b and whose electric resistivity is at 7μΩ.cm or lower.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a circuit board used for communication equipment such as a mobile phone.

[0002]

2. Description of the Related Art Recently, communication devices such as mobile phones have been rapidly reduced in size and increased in density. Therefore, circuit boards housed inside the communication devices are also required to be downsized and multifunctional. Has been done. For this reason, inside and on the surface of the circuit board,
A circuit board has been proposed in which a part of a capacitor or an inductor, which is a passive component forming a filter, a resonance circuit, or the like, is integrally formed by a metallizing technique.

In such a circuit board, a wiring conductor made of a refractory metal powder such as tungsten or molybdenum is adhered and formed inside and on an insulating base made of an electrically insulating material such as an aluminum oxide sintered body. The grounding conductor is formed by embedding a wide area grounding conductor and a power source conductor made of a high melting point metal powder such as tungsten or molybdenum in the insulating base so as to face each other with an insulating layer interposed therebetween. And a capacitor having a power supply conductor as an electrode, and an inductor line of a predetermined length made of refractory metal powder such as tungsten or molybdenum is also formed in a meandering shape or a coil shape inside the insulating base to form an inductor. Is forming.

In such a circuit board, the characteristic impedance of the inductor line is adjusted to a predetermined value by electromagnetically coupling the ground conductor or the power supply conductor and the inductor line with an insulator interposed therebetween. The structure is such that the capacitor formed by the conductor and the inductor formed by the inductor line function as a part of the filter or the resonance circuit.

[0005]

However, in this circuit board, the electrical resistivity of the inductor line made of refractory metal powder such as tungsten and molybdenum is about 15 μΩ.
-The electrical resistance of the inductor line is large due to the fact that it is relatively high at about cm and the inductor line is thin and long in order to obtain a predetermined inductance, and therefore the signal propagating through the inductor line is greatly attenuated. However, it has a drawback that the circuit board cannot sufficiently exhibit the predetermined filter characteristics and resonance characteristics.

Therefore, the inductor line is deposited on the surface of the insulating substrate, and a metal having good conductivity such as gold is deposited on the outer surface of the inductor line by a plating method, whereby the electrical resistance of the inductor line is reduced. It can be considered low.

However, when the frequency of the signal propagating through the inductor line becomes extremely high, the so-called skin effect due to the electromagnetic coupling between the inductor line and the ground conductor or the power supply conductor causes the signal to be connected to the ground conductor or the power supply conductor in the inductor line. The flow will be concentrated on the opposite side, that is, on the side where the plated metal layer is not adhered. Therefore, the effect of reducing the electric resistance due to the adhered plated metal layer on the inductor line is almost eliminated. It caused a drawback that the attenuation of the signal propagating through could not be suppressed.

[0008]

SUMMARY OF THE INVENTION The present invention has been devised in view of such drawbacks, and it is possible to exhibit predetermined filter characteristics and resonance characteristics by making the attenuation of a signal propagating through an inductor line extremely small. An object is to provide a circuit board that can be manufactured.

[0009]

DISCLOSURE OF THE INVENTION The present invention is a circuit board comprising an insulating substrate having a ground conductor and a power supply conductor therein, and an inductor line facing the ground conductor or the power supply conductor. The inductor line has a pair of metallized lines that run in close proximity to each other and an electric resistivity of 7 μm that covers the insulating substrate between the pair of metallized lines.
It is characterized in that it is formed of a plated metal layer of Ω · cm or less.

[0010]

According to the circuit board of the present invention, a pair of metallized lines in which the inductor lines run parallel to each other on the surface of the insulating substrate and the insulating substrate between the pair of metallized lines are plated with an electric resistivity of 7 μΩ · cm or less. Since it is formed of the metal layer, the signal propagating through the inductor line has an electric resistivity of 7 μm that covers the insulating base between the pair of metallized lines.
It mainly flows through the plated metal layer having good conductivity of Ω · cm or less, and as a result, the attenuation of the signal propagating through the inductor line can be reduced.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, a circuit board of the present invention will be described in detail with reference to the accompanying drawings.

1 and 2 are a sectional view showing an embodiment of a circuit board according to the present invention and an enlarged view of a main part thereof, wherein 1 is an insulating substrate and 2 is a wiring conductor. The circuit board A is formed by attaching the wiring conductor 2 to the insulating substrate 1.

The insulating base 1 has on its upper surface a mounting portion 1a on which electronic components such as semiconductor elements and SAW elements are mounted, and the mounting portion 1a is mounted with electronic components 3 such as semiconductor elements and SAW elements. It

The insulating substrate 1 is made of an aluminum oxide sintered body, an aluminum nitride sintered body, a mullite sintered body,
When it is made of an electrically insulating material such as a silicon carbide sintered body or a glass ceramics sintered body, for example, when it is made of an aluminum oxide sintered body, it is suitable as a raw material powder of aluminum oxide, silicon oxide, calcium oxide, magnesium oxide or the like. A binder and a solvent are added and mixed to form a slurry, and a ceramic green sheet is obtained by forming it into a sheet by adopting a conventionally known doctor blade method.After that, the ceramic green sheet is punched by a method such as a punching method. It is manufactured by punching into an appropriate shape, laminating a plurality of sheets as necessary, and finally firing the ceramic green sheet in a reducing atmosphere at a temperature of about 1600 ° C.

The insulating base 1 has a mounting portion 1a.
A wiring conductor 2 extending from the bottom surface to the bottom surface is adhered and formed. Each electrode of an electronic component 3 such as a semiconductor element or a SAW element is electrically connected via a bonding wire 4 to a portion around the mounting portion 1a of the wiring conductor 2. Connected to the insulating substrate 1
The part led out to the bottom surface of is connected to an external electric circuit.

The wiring conductor 2 is made of a refractory metal powder containing tungsten, molybdenum or the like as a main component, and serves to electrically connect each electrode of the electronic component 3 to an external electric circuit.

For the wiring conductor 2, a metal paste obtained by adding and mixing a suitable binder and a solvent to the refractory metal powder such as tungsten is mixed with a ceramic green sheet to be the insulating substrate 1 by a conventionally known screen printing method or the like. The thick film method is used to print and apply a predetermined pattern, so that the insulating substrate 1 is deposited and formed from the mounting portion 1a to the bottom surface of the insulating substrate 1.

Inside the insulating base 1, a large area ground conductor 5 and a power supply conductor 6 electrically connected to a part of the wiring conductor 2 are provided between the insulating base 1 and a part of the insulating base 1. It is buried so as to sandwich and face each other.

The ground conductor 5 and the power supply conductor 6 respectively act as electrodes of a parallel plate capacitor formed by using a part of the insulating substrate 1 sandwiched therebetween as a dielectric, and the ground conductor 5 and the power supply conductor 6 are connected. The capacitor formed by the conductor 6 and a part of the insulating substrate 1 constitutes a part of a filter, a resonance circuit, or the like.

The ground conductor 5 and the power supply conductor 6 are made of a refractory metal powder containing tungsten, molybdenum or the like as a main component, and the same method as that for the metallized wiring layer 2, that is,
A metal paste obtained by adding and mixing a suitable binder and a solvent to the refractory metal powder such as tungsten is applied to the ceramic green sheet serving as the insulating substrate 1 by a well-known thick film technique such as screen printing. By printing and applying the pattern, the insulating base 1 is embedded and formed so as to face each other with a part of the insulating base 1 interposed therebetween.

Further, a concave portion 1b is formed on the lower surface of the insulating substrate 1.
And the ground conductor 5 is formed on the bottom surface of the recess 1b.
A pair of metallized lines 7a and 7b facing each other
Has been formed.

The pair of metallized lines 7a and 7b are
The inductor wires 9 run side by side in close proximity to each other and are formed on the bottom surface of the recess 1b of the insulating substrate 1 in a meandering or spiral shape to form an inductor line 9 together with a plated metal layer 8 to be described later. It acts as a guide for depositing the plated metal layer 8 on the surface of the insulating substrate 1.

The pair of metallized lines 7a and 7b are provided.
When the mutual distance exceeds 30 μm, it tends to be difficult to deposit a later-described plated metal layer 8 on the insulating substrate 1 between the pair of metallized lines 7a and 7b by a plating method. Therefore, the pair of metallized lines 7a, 7a
It is preferable that the distances b are 30 μm or less.

The pair of metallized lines 7a and 7b are
The wiring conductor 2, the ground conductor 5, and the power supply conductor 6 are made of a high melting point metal powder containing tungsten, molybdenum, or the like as a main component.
The same method as described above, that is, a metal paste obtained by adding and mixing an appropriate binder and solvent to the refractory metal powder such as tungsten is applied to the ceramic green sheet serving as the insulating substrate 1 by a thick film such as a conventionally known screen printing method. By applying the method by printing and coating in a predetermined pattern, it is formed on the bottom surface of the concave portion 1b of the insulating substrate 1 in a meandering or spiral shape so as to run in parallel with each other.

On the exposed outer surfaces of the metallized lines 7a and 7b and on the surface of the insulating substrate 1 between the metallized lines 7a and 7b, a well-conductive plated metal layer 8 having an electric resistivity of 7 μΩ · cm or less is well known in the art. It is deposited by electrolytic plating or electroless plating.

As described above, the plated metal layer 8 constitutes an inductor line 9 together with the pair of metallized lines 7a and 7b, and the pair of metallized lines 7a and 7b.
The inductor line 9 composed of the plated metal layer 8 and the grounded conductor 5 is adjusted to have a predetermined characteristic impedance by forming an electromagnetic coupling with the ground conductor 5, and functions as a component forming a part of a filter, a resonator or the like. To do.

The inductor line 9 consisting of the pair of metallized lines 7a and 7b and the plated metal layer 8 has a good conductive plated metal layer 8 directly deposited on the insulating substrate 1 between the pair of metallized lines 7a and 7b. From that,
Even if a signal concentrates on the side of the insulating substrate 1 of the inductor line 9 due to the skin effect due to the electromagnetic coupling between the inductor line 9 and the ground conductor 5, the signal is insulated between the pair of metallized lines 7a and 7b. It will flow mainly through the good conductive plated metal layer 8 deposited on the substrate 1, and as a result, the signal propagating through the inductor line 9 will not be greatly attenuated, and therefore, the predetermined filter characteristic and resonance will not occur. The circuit characteristics can be exhibited.

The plated metal layer 8 has an electric resistivity of 7
If it exceeds μΩ · cm, it tends to be difficult to reduce the electric resistance of the inductor line 9, so that the plated metal layer 8 has an electric resistivity of 7 μΩ · c.
m or less.

Examples of the plated metal layer 8 having an electric resistivity of 7 μΩ · cm or less include gold, silver, copper, rhodium, nickel, aluminum, cobalt, zinc and the like, and alloys and laminates thereof. But it's okay.

In order to deposit the plating metal layer 8 having an electric resistivity of 7 μΩ · cm or less on the outer surfaces of the metallized lines 7a and 7b and the surface of the insulating substrate 1 between the metallized lines 7a and 7b, for example, the above-mentioned plating is performed. When the metal layer 8 is made of gold, the surface of the metallized lines 7a and 7b is cleaned with a cleaning solution such as acid or alkali, and then the metallized line 7 is formed.
An active metal such as tin or palladium is adhered to the surfaces of a and 7b by a conventionally known activation treatment method, and then gold is applied to the surfaces of the metallized lines 7a and 7b to which the active metal is adhered by a conventionally known displacement gold plating method. .025 μm or so is deposited,
Finally, a method of depositing a plating metal layer 8 made of gold to a predetermined thickness on the outer surfaces of the metallized lines 7a and 7b on which gold is deposited by the displacement gold plating method by a conventionally known electrolytic gold plating method or electroless gold plating method is adopted. In this case, since the pair of metallized lines 7a and 7b run in close proximity to each other, when the plated metal layer 8 is applied to the metallized lines 7a and 7b, the plated metal applied to the metallized lines 7a and 7b. The layers 8 are crystal-grown from both sides and communicate with each other, whereby the plated metal layer 8 can be deposited also on the surface of the insulating substrate 1 between the pair of metallized lines 7a and 7b.

The plated metal layer 8 has a thickness of 15
When the thickness is less than μm, it becomes difficult to deposit the plated metal layer 8 on the surface of the insulating substrate 1 between the pair of metallized lines 7a and 7b, and when it exceeds 60 μm, the plated metal layer 8 is deposited when the plated metal layer 8 is deposited. The plating stress remaining inside 8 becomes extremely large, and as a result, the plated metal layer 8 tends to be easily separated from the metallized lines 7a and 7b. Therefore, the plated metal layer 8 preferably has a thickness in the range of 15 to 60 μm.

Thus, according to the circuit board of the present invention, the electronic component 3 such as a semiconductor element or a SAW element is mounted on the mounting portion 1a of the insulating substrate 1 and each electrode of the electronic component 3 is wired via the bonding wire 4. It is electrically connected to the conductor 2, and then, if necessary, the lid body 10 made of metal or the like is joined to the upper surface of the insulating base body 1 through a sealing material such as solder, resin, or glass, whereby a filter is formed. It is housed in a communication device such as a mobile phone as a circuit board having a resonance circuit and the like.

It is needless to say that the present invention is not limited to the above-mentioned embodiments, and various modifications can be made without departing from the gist of the present invention. In the example, the pair of metallized lines 7a, 7
Although the distance b is preferably 30 μm, as shown in FIG. 3, the distance between the pair of metallized lines 7a and 7b is 30 μm.
The guide metallization layer 7 having a linear or dot shape is formed between the pair of metallized lines 7a and 7b.
When c is deposited and formed so that the distance between it and the metallized lines 7a and 7b is less than 30 μm, a wider area of the plated metal layer 8 is deposited on the insulating substrate 1 between the metallized lines 7a and 7b. Therefore, a linear or dot-shaped inductive metallization layer 7c may be deposited on the insulating substrate 1 between the pair of metallized lines 7a and 7b.

[0034]

The circuit board of the present invention includes a pair of metallized lines in which inductor lines formed on the surface of an insulating substrate having a grounding conductor and a power supply conductor inside run parallel to each other, and the pair of metallized lines. Since it is formed of a plated metal layer having an electrical resistivity of 7 μΩ · cm or less that covers the insulating substrate between, the signal propagating in the inductor line is generated by the electromagnetic coupling between the inductor line and the ground conductor or the power supply conductor. Even if the signal flows concentratedly on the insulating substrate side of the inductor line due to the skin effect, the signal is transmitted through the insulating substrate between the pair of metallized lines through the plated metal layer having a good electrical conductivity of 7 μΩ · cm or less. As a result, the signal propagating in the inductor line is not largely attenuated as a result, and the prescribed filter characteristics and resonant circuit characteristics are not It is possible to volatilization.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an embodiment of a circuit board of the present invention.

FIG. 2 is an enlarged view of a main part of the circuit board shown in FIG.

FIG. 3 is an enlarged view of a main part showing another embodiment of the present invention.

[Explanation of symbols]

 1 ... Insulating substrate 5 ... Ground conductor 6 ... Power supply conductor 7a, 7b ... Metallized line 8 ... Plating metal layer 9 ...・ Inductor line A ・ ・ ・ ・ ・ ・ Circuit board

Claims (1)

[Claims] 1. A circuit board comprising an insulating substrate having a ground conductor and a power supply conductor inside, and an inductor line facing the ground conductor or the power supply conductor.
The inductor line is formed of a pair of metallized lines that run in close proximity to each other and a plated metal layer having an electric resistivity of 7 μΩ · cm or less that covers an insulating substrate between the pair of metallized lines. Circuit board.