JPH0677341A - Circuit board - Google Patents

Abstract

PURPOSE:To match the impedance between the metallized wiring pattern and a connection pad, in a circuit board which has microstrip line structure. CONSTITUTION:This circuit board is equipped with an insulating substrate, a metallized wiring pattern 2, which is made on the surface of the insulating substrate, a connection pad 5, which is wider than the metallized pattern 2, being so made on the surface of the insulating substrate as to connect electrically with the metallized wiring pattern 2, and an earth metallized pattern 9, which is arranged to oppose the metallized wiring pattern 2 and the connection pattern 5, with an insulating layer 1a between. For the earth metallized pattern 9, the width 13 of the section opposed to the connection pad 5 is narrower than that of the section opposed to the metallized wiring pattern 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a circuit board on which electronic parts such as semiconductor elements are mounted.

[0002]

2. Description of the Related Art Generally, a circuit board has an insulating base made of an electrically insulating material such as alumina ceramics. Then, on the surface of the insulating substrate, a mounting portion on which an electronic component is mounted and a plurality of metallized wiring patterns for connecting the electronic component mounted on the mounting portion to an external electric circuit are formed.

The circuit board has a microstrip line structure in which a ground pattern having a large area is arranged below the metallized wiring pattern with an insulating layer interposed therebetween. As a result, the characteristic impedance of the metallized wiring pattern can be made constant. In the circuit board as described above, high-density mounting is required due to the recent miniaturization of electronic devices, and as the metallized wiring pattern, a narrow pattern having a width of about 10 to 200 μm is used. On the other hand, at the end of the metallized wiring pattern, wide connection pads are formed for connecting to each electrode of the electronic component and for connecting a flat cable or a coaxial cable for connecting to an external electric circuit. . The connection pad is usually set to have a width of about 500 μm to 2000 μm in consideration of workability and certainty of adhesion.

[0004]

Particularly in a circuit board that handles a high frequency signal, it is necessary to adopt the above-described microstrip line structure for impedance matching and transmitting a signal without distortion. However, as described above, the metallized wiring pattern is 10 to 20.
0 μm, and the connection pad at the end is 500 to 200
Since the thickness is 0 μm, there is a problem in that the inductance and the capacitance between the ground pattern and the metallized wiring pattern change from the metallized wiring pattern to the connection pad, causing impedance discontinuity and signal distortion.

It is an object of the present invention to suppress impedance discontinuity in a circuit board having a microstrip line structure that is densely packaged.

[0006]

A circuit board according to the present invention is formed by an insulating base, a wiring conductor formed inside or on the surface of the insulating base, and electrically connected to the wiring conductor on the surface of the insulating base. Wider connection pads than wiring conductors,
An insulating substrate is provided with a ground conductor or a power conductor arranged so as to face the wiring conductor and the connection pad with the insulating layer interposed therebetween. The ground conductor or the power conductor is formed such that the width of the portion facing the connection pad is narrower than the width of the portion facing the wiring conductor.

[0007]

In the circuit board according to the present invention, the wiring conductor and the connection pad wider than the wiring conductor are formed inside or on the insulating base, and the wiring conductor and the connection pad are sandwiched between the insulating base and the wiring conductor. A ground conductor or a power conductor is arranged so as to face each other, and has a microstrip line structure.

At this time, the ground conductor or the power supply conductor is formed such that the width of the portion facing the connection pad is narrower than the width of the portion facing the wiring conductor. Therefore, even when a connection pad wider than the wiring conductor is formed, the impedance of the microstrip line structure formed by this connection pad and the ground conductor or the power supply conductor is The impedance of the formed microstrip line structure is almost the same as that of the microstrip line structure, and impedance discontinuity can be suppressed.

[0009]

1 is a sectional view of a circuit board according to an embodiment of the present invention. The insulating base 1 is composed of an upper insulating base 1a and a lower insulating base 1b. These insulating bases 1a and 1b are manufactured by a well-known method from an electrically insulating material such as alumina ceramics. A metallized wiring pattern 2 is formed on the surface of the insulating base 1a.
The metallized wiring pattern 2 is a pattern for transmitting a high frequency signal, and is formed of a refractory metal powder such as tungsten or molybdenum. In addition, this pattern width is 10 to 2 in order to enable high-density mounting.
The width is 00 μm. Metallized wiring pattern 2
Is formed with a pad 3 for connecting an electronic component, and an electronic component 4 such as a semiconductor element, a resistive element or a capacitive element is connected to the pad 3 for connecting an electronic component. There is. On the other hand, an external connection pad 5 is formed at the other end (right end in FIG. 1) of the metallized wiring pattern 2. One electrode of a coaxial cable 6 of an external electric circuit is connected to the external connection pad 5.

Component connection pad 3 and external connection pad 5
Have a width of about 500 to 2000 μm. By forming such a wide width, the connection with the electronic component 4 and the coaxial cable 6 becomes easy and the connection becomes strong. Ground electrode patterns 7 and 8 connected to the electronic component 4 and the coaxial cable 6 are formed on the surface of the insulating substrate 1a.

An upper insulating base 1a and a lower insulating base 1b
A wide area grounding metallization pattern 9 is formed between and. The ground metallized pattern 9 is formed of a high melting point metal powder such as tungsten or molybdenum, and faces the metallized wiring pattern 2, the component connection pad 3, and the external connection pad 5 with the insulating substrate 1a interposed therebetween. In this way, the metallized wiring pattern 2 and the pads 3 and 5 are formed into microstrip lines, and the characteristic impedance is stabilized.
Further, the ground electrode patterns 7 and 8 formed on the surface of the insulating substrate 1a are connected to the ground metallized pattern 9 through through holes 10 and 11, respectively.

The ground metallization pattern 9 has openings 12a and 12b formed in the lower portions of the component connection pad 3 and the external connection pad 5, respectively, as shown in FIG. The connecting portion 13 between the openings 12a and 12b is the connecting pad 3 and the external connecting pad 5
Is facing. Here, the width of the contact portion 13 is defined by the impedance of the metallized wiring pattern 2 portion and each pad 3,
The impedances of the five parts have almost the same value, and the impedance matching between the two is set.

In the circuit board having such a structure, although the component connection pad 3 and the external connection pad 5 are wide,
The ground metallization pattern 9 (communication portion 13) in the portion facing the pads 3 and 5 is narrowed by the openings 12a and 12b, and the impedance becomes larger than that when the openings 12a and 12b are not formed. . Therefore, the impedance formed between the metallized wiring pattern 2 having a narrow width and the grounded metallized pattern 9 is almost the same, and the characteristic impedance between the metallized wiring pattern 2 and each connection pad 3, 5 can be matched. It will be possible.

Therefore, the high frequency signal transmitted through the metallized wiring pattern 2 formed on such a circuit board has less distortion. [Other Embodiments] (a) In the above embodiments, the present invention is applied to the metallized wiring pattern 2 formed on the surface of the insulating substrate 1 and the microstrip line structure between each pad 3, 5 and the ground metallized pattern 9. Although the present invention is applied, the present invention can be similarly applied to the case where the wiring pattern and the pad are formed inside the insulating substrate 1 to have the ground pattern and the microstrip line structure.

Further, the present invention can be applied between the metallized wiring pattern 2 and each pad 3, 5 and the power supply pattern. (B) In the above-described embodiment, the present invention is applied to the microstrip line structure in which the ground pattern is formed only below the wiring pattern with the insulating layer interposed, but the ground pattern or the power supply pattern has the wiring pattern with the insulating layer interposed. The present invention can be similarly applied to a stripline structure which is arranged so as to face both above and below.

[0016]

As described above, according to the present invention, the width of the ground pattern facing the connection pad portion is narrowed to match the impedance of the wiring pattern portion with the impedance of the connection pad portion. It is possible to realize a circuit board that can transmit power with less distortion.

[Brief description of drawings]

FIG. 1 is a cross-sectional configuration diagram of a circuit board according to an embodiment of the present invention.

FIG. 2 is an exploded perspective partial view of FIG.

[Explanation of symbols]

 1a, 1b Insulating substrate 2 Metallized wiring pattern 3 Component connection pad 5 External connection pad 9 Grounded metallized pattern 12a, 12b Opening 13 Communication part

Claims (1)

[Claims] 1. An insulating base, a wiring conductor formed inside or on the surface of the insulating base, and formed on the surface of the insulating base by being electrically connected to the wiring conductor and having a wider width than the wiring conductor. Connection pad and a ground conductor or a power conductor arranged so as to face the wiring conductor and the connection pad with an insulating layer sandwiched in the insulating base, and the ground conductor or the power conductor faces the connection pad. A circuit board, wherein a width of a portion to be formed is smaller than a width of a portion facing the wiring conductor.