JP2001326444A - Chip component mounting board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a chip component mounting board, by which characteristics of a chip component can be achieved reliably by reducing capacitance in a gap between micro strip lines, and a frequency range used by the chip component can be widened by making a self resonant frequency higher when the chip component is mounted. SOLUTION: There is provided a planar shaped dielectric substrate 1. A ground layer 2 and micro strip lines 3 are formed on the lower surface and the upper surface, respectively, of the dielectric substrate 1. A rectangular parallelepiped shaped through hole 7 is provided from the dielectric substrate 1 through the ground layer 2 in a gap 4 between the micro strip lines 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technology for mounting a chip component using a microstrip line.
The present invention relates to a chip component mounting board for reducing capacitance.

[0002]

2. Description of the Related Art In recent years, in the field of electronic equipment having a high-frequency integrated circuit such as a portable telephone and a digital still camera, miniaturization and weight reduction are rapidly progressing. Therefore, there is also a strong demand for miniaturization and improvement of high-frequency characteristics of mounting boards for chip components used in these components. Conventionally, when a high-frequency integrated circuit is formed on a substrate, a substrate on which chip components are mounted on a microstrip line has been widely used. The microstrip line may be considered to be a flat coaxial cable used for high-frequency transmission and developed in a plane.

Here, a mounting board for chip components using a microstrip line will be specifically described with reference to FIGS. FIG. 4 is a perspective view of a conventional mounting board for chip components, FIG. 5 is a sectional view of the same, and FIG. 6 is an equivalent circuit diagram of the same. As shown in FIGS. 4 and 5, a flat dielectric substrate 1 made of alumina ceramic or the like is provided. A ground layer 2 made of a conductor is formed on the lower surface of the dielectric substrate 1, and a microstrip line 3 serving as a strip-shaped conductor line is formed on the upper surface.
The microstrip line 3 is generally formed by laminating an electroless Cu plating layer on a thick-film conductor formed of an Ag paste or the like. The microstrip line 3 forms a predetermined land pattern while including a gap 4 between the lines 3. A chip component 5 such as a chip capacitor is placed above the gap 4 and mounted on the microstrip line 3 by solder 6.

In a mounting board for chip components having such a configuration, the characteristic impedance is determined by the relative permittivity and the thickness of the dielectric substrate 1 or the width and the thickness of the microstrip line 3. Generally, when a high frequency propagates in a conductor line, current does not flow much at the center of the conductor and concentrates near the surface of the conductor (skin effect). The higher the frequency, the stronger the tendency. When the frequency is on the order of GHz, the skin depth becomes several microns, and the current almost flows only on the surface of the conductor line. As described above, since the surface of the microstrip line 3 is an electroless Cu plating layer, the conductivity of the skin portion is high. Therefore, even if current concentrates on the conductor surface due to the skin effect, transmission loss is relatively small, and excellent transmission efficiency can be secured.

[0005]

However, the above prior art has the following problems. That is, the leading end of the microstrip line 3 is an electrode plate, and the gap 4 as a space between the lines 3 is a capacitor in which a dielectric having a dielectric constant is half filled between the electrode plates. For this reason, as shown in FIG. 6, the gap 4 between the microstrip lines 3 functions as a capacitor and has a capacitance C.

The relational expression between the capacitance C due to the gap 4 and the surface area S of the electrode plate, the distance d between the electrode plates, and the dielectric constant ε between the electrode plates is as shown in equation (1).

(Equation 1)

At present, the size of the chip component 5 is 1005
Type (Chip size L: 1.0mm x W: 0.5m
m) to 0603 type (chip size L: 0.6mm)
× W: 0.3 mm), and the gap 4 has been narrowed accordingly. As can be seen from the above equation (1), when the interval between the gaps 4, that is, the interval d between the electrode plates becomes smaller, the capacitance C due to the gap 4 becomes larger. Such an increase in the capacitance C may cause a problem that the characteristics of the chip component 5 cannot be realized on the substrate.

When the capacitance C increases, the self-resonant frequency f at the time of mounting the chip component 5 decreases. In the chip component 5, as the frequency increases, parasitic components such as the conductor resistance of the electrodes and the capacitance between the electrodes appear, and the reactance component, the capacitance component, and the inductance component become impure and exhibit different characteristics.

For example, the inductance component L of the chip component 5 does not become a pure inductance component L at a high frequency, but has a capacitance component C as a parasitic component. At this time, the inductance component L and the capacitance component C, which is a parasitic component, form a resonator and cause resonance, and a resonance frequency (referred to as a self-resonance frequency f) is generated between the two components L and C.

The self-resonant frequency f can be obtained from the following equation (2).

(Equation 2)

For a frequency signal higher than the self-resonant frequency f, the inductance component of the chip component 5 acts as a capacitance component. In other words, the self-resonance frequency is the limit of use in the original characteristics of the chip component 5, and the lower self-resonance frequency is nothing less than the narrower frequency range in which the chip component 5 can be used.

As described above, when the gap 4 between the microstrip lines 3 becomes smaller as the chip component 5 becomes smaller, the capacitance C increases. As a result, not only is it difficult to realize the characteristics of the chip component 5, but also the self-resonant frequency at the time of mounting the chip
However, there is a problem that the range of usable frequencies is narrowed.

The present invention has been proposed to solve such a problem, and an object of the present invention is to reduce the capacitance in the gap between the microstrip lines and reliably realize the characteristics of the chip component. At the same time, it is an object of the present invention to provide a chip component mounting substrate capable of increasing the self-resonant frequency at the time of mounting the chip component and expanding the usable frequency range of the chip component.

[0014]

In order to achieve the above object, the present invention provides a flat dielectric substrate, a ground layer on one surface of the dielectric substrate, and a microstrip on the other surface. A chip component mounting board in which lines are formed and chip components are mounted on the microstrip line has the following technical features.

The invention according to claim 1 is characterized in that the dielectric substrate corresponding to a gap between the microstrip lines includes:
An opening is provided.

According to the first aspect of the present invention, since the opening is provided in the dielectric substrate itself corresponding to the gap between the microstrip lines, the dielectric constant of the dielectric substrate between the gaps is significantly lower than that. Can be changed to the dielectric constant of air. Therefore, the capacitance due to the gap can be reduced. As a result, it is possible to reliably realize the characteristics of the chip component. Further, since the self-resonant frequency at the time of mounting the chip component increases due to the decrease in the capacitance, the frequency range in which the chip component can be used is widened. Moreover, in the present invention, since the opening is formed only in the portion of the dielectric substrate corresponding to the gap instead of providing the hollow layer entirely below the dielectric substrate, the thickness dimension of the entire mounting substrate increases. And can contribute to downsizing.

According to a second aspect of the present invention, in the chip component mounting substrate according to the first aspect, the opening is provided so as to penetrate from the dielectric substrate to the ground layer.

According to the second aspect of the present invention, since the opening penetrates from the dielectric substrate to the ground layer, the weight of the substrate is reduced, and the contact area with air is increased to improve heat radiation. .

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be specifically described below with reference to FIGS. The same members as those in the prior art shown in FIGS. 4 to 6 are denoted by the same reference numerals, and description thereof will be omitted.

(1) Representative Embodiment [Structure] This embodiment includes claims 1 and 2, FIG. 1 is a perspective view of this embodiment, and FIG. 2 is a sectional view of the same. is there. As shown in FIGS. 1 and 2, a rectangular parallelepiped through hole 7 is provided from the dielectric substrate 1 corresponding to the gap 4 between the microstrip lines 3 to the ground layer 2.

[Effects] In the present embodiment having such a structure, the dielectric substrate 1 itself corresponding to the gap 4 between the microstrip lines 3 is formed with the through hole 7 so that the dielectric substrate between the gaps 4 can be formed. The dielectric constant of 1 can be changed to the dielectric constant of air. The dielectric constant of air is 1, which is smaller than the dielectric constant of the dielectric substrate 1.
Therefore, the dielectric constant in the gap 4 decreases, and the capacitance C due to the gap 4 decreases as is apparent from the above equation (1). As a result, the characteristics of the chip component 5 are easily realized.

Further, the self-resonant frequency at the time of mounting the chip component 5 is increased by the reduction of the capacitance C due to the gap 4. Therefore, it is possible to widen the range of frequencies in which the chip component 5 can be used. Further, since the through hole 7 penetrates from the dielectric substrate 1 to the ground layer 2, the weight and the heat dissipation of the dielectric substrate 1 are improved. Moreover, in the present embodiment, there is no need to provide a hollow layer containing air below the dielectric substrate 1, and the through hole 7 is formed only in the portion of the dielectric substrate 1 corresponding to the gap 4. Therefore, the entire mounting substrate is not thickened by the hollow layer, and does not hinder miniaturization.

(2) Other Embodiments The present invention is not limited to the above embodiments,
The shape, size, quantity, material, etc. of each member can be appropriately changed, and the types of chip components to be mounted are also chip capacitors,
A chip inductor or the like can be appropriately selected. For example, in the embodiment shown in the cross-sectional view of FIG. 3, the dielectric substrate 1 corresponding to the gap 4 is cut into a certain depth to form the opening 8.
Are formed. In such an embodiment,
The same operation and effect as described above can be obtained.

Furthermore, if the opening 8 is formed beyond the width of the microstrip line 3, the capacitance C due to the gap 4 can be further reduced. In addition, the soldering method of the chip component 5 can be formed by any known method. Further, in each of the above embodiments, a two-layer board is used, but a multi-layer board may be used.

[0025]

As described above, according to the chip component mounting board of the present invention, the microstrip line is formed by a very simple structure such as providing an opening in the dielectric substrate itself corresponding to the gap between the microstrip lines. Capacitance in the gap between them can be reduced, thereby facilitating the realization of the characteristics of the chip component, and at the same time, increasing the self-resonant frequency at the time of mounting the chip component and expanding the usable frequency range of the chip component. .

[Brief description of the drawings]

FIG. 1 is a perspective view of a typical embodiment of the present invention.

FIG. 2 is a cross-sectional view of a typical embodiment of the present invention.

FIG. 3 is a sectional view of another embodiment of the present invention.

FIG. 4 is a perspective view of a conventional mounting board for chip components.

FIG. 5 is a cross-sectional view of a conventional mounting board for chip components.

FIG. 6 is an equivalent circuit diagram of a conventional mounting board for chip components.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Dielectric substrate 2 ... Ground layer 3 ... Microstrip line 4 ... Gap 5 ... Chip component 6 ... Solder 7 ... Through-hole 8 ... Opening

Claims (2)

[Claims] 1. A planar dielectric substrate is provided, a ground layer is formed on one surface of the dielectric substrate, and a microstrip line is formed on the other surface, and a chip component is mounted on the microstrip line. A chip component mounting board according to claim 1, wherein an opening is provided in said dielectric substrate corresponding to a gap between said microstrip lines. 2. The mounting board according to claim 1, wherein the opening is provided so as to penetrate from the dielectric substrate to the ground layer.