JP2758321B2 - Circuit board - Google Patents

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 components 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. A mounting portion on which the 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 on the surface of the insulating base.

Further, the circuit board has a microstrip line structure by arranging a ground pattern having a large area under an insulating layer below a metallized wiring pattern. Thereby, the characteristic impedance of the metallized wiring pattern can be made constant. In such a circuit board, high-density mounting is required in accordance with recent miniaturization of electronic devices, and a thin pattern having a width of about 10 to 200 μm is used as a metallized wiring pattern. On the other hand, at the end of the metallized wiring pattern, wide connection pads are formed to connect to each electrode of the electronic component and to connect a flat cable or a coaxial cable for connecting to an external electric circuit. . This connection pad is usually set to a width of about 500 μm to 2000 μm in consideration of simplification of work and reliability of adhesion.

[0004]

In particular, a circuit board for handling high-frequency signals must employ the microstrip line structure as described above to match impedances and transmit signals without distortion. However, as described above, the metallized wiring pattern is 10-20.
0 μm, and the connection pad at the end is 500 to 200 μm.
Since it is 0 μm, there is a problem that inductance and capacitance between the metallized wiring pattern and the connection pattern change at a portion where the metallized wiring pattern is transferred to the connection pad, and the impedance becomes discontinuous, thereby causing signal distortion.

An object of the present invention is to suppress impedance discontinuity in a circuit board having a microstrip line structure mounted at high density.

[0006]

A circuit board according to the present invention is formed by electrically connecting an insulating base, a wiring conductor formed inside or on the surface of the insulating base, and a wiring conductor on the surface of the insulating base. Connection pads wider than the wiring conductors,
A ground conductor or a power supply conductor is provided on the insulating base so as to face the wiring conductor and the connection pad with the insulating layer interposed therebetween. The ground conductor or the power supply conductor is formed so that the width of the portion facing the connection pad is smaller 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 surface of the insulating base, and the wiring conductor and the connection pad are interposed between the insulating base and the insulating layer. Ground conductors or power supply conductors are arranged to face each other, forming a microstrip line structure.

At this time, the ground conductor or the power supply conductor is formed so that the width of the portion facing the connection pad is smaller 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 increased by the wiring conductor and the ground conductor or the power supply conductor. The impedance is substantially equal to the impedance of the formed microstrip line structure, and the discontinuity of the impedance 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, and these insulating bases 1a and 1b are manufactured by a known method using 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 high melting point metal powder such as tungsten or molybdenum. The pattern width is 10 to 2 to enable high-density mounting.
The width is 00 μm. Metallized wiring pattern 2
At one end (the left end in FIG. 1), a pad 3 for connecting an electronic component is formed. The component connecting pad 3 is connected to an electronic component 4 such as a semiconductor element, a resistance element or a capacitance element. I have. On the other hand, an external connection pad 5 is formed at the other end (the 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
Are formed to have a width of about 500 to 2000 μm. By forming such a wide width, connection with the electronic component 4 and the coaxial cable 6 becomes easy and the connection becomes strong. In addition, 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 base 1a.

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

As shown in FIG. 2, the ground metallized pattern 9 has openings 12a and 12b formed in the lower portions of the component connection pads 3 and the external connection pads 5, respectively. The connection portion 13 between the openings 12a and 12b is used as the component connection pad 3 and the external connection pad 5
And is facing. Here, the width of the contact portion 13 is determined by the impedance of the metallized wiring pattern 2 portion and each pad 3,
The impedances of the five parts are set to values that are substantially equal to each other so that impedance matching between the two can be achieved.

In the circuit board having such a configuration, although the component connection pads 3 and the external connection pads 5 are wide,
The ground metallized pattern 9 (communication portion 13) at the portion facing these pads 3 and 5 is narrowed by openings 12a and 12b, and the impedance is increased as compared with the case where openings 12a and 12b are not formed. . Therefore, the impedance is substantially the same as the impedance formed between the narrow metallized wiring pattern 2 and the ground metallized pattern 9, and the characteristic impedance between the metallized wiring pattern 2 and each of the connection pads 3 and 5 can be matched. It becomes possible.

Therefore, the distortion of the high-frequency signal transmitted through the metallized wiring pattern 2 formed on such a circuit board becomes small. [Other Embodiments] (a) In the above embodiment, 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 of the pads 3, 5 and the ground metallized pattern 9. Although the present invention has been applied, the present invention can be similarly applied to a case where a wiring pattern and a pad are formed inside the insulating base 1 to form a ground pattern and a microstrip line structure.

The present invention can also be applied between the metallized wiring pattern 2 and each of the pads 3 and 5 and the power supply pattern. (B) In the above 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 therebetween. The present invention can be similarly applied to a strip line structure arranged so as to face both upper and lower sides.

[0016]

As described above, according to the present invention, the width of the ground pattern facing the connection pad portion is reduced, and the impedance of the wiring pattern portion is matched with the impedance of the connection pad portion. Can be realized with a circuit board capable of transmitting the signal with little distortion.

[Brief description of the 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. 1;

[Explanation of symbols]

 1a, 1b Insulating base 2 Metallized wiring pattern 3 Component connection pad 5 External connection pad 9 Ground metallized pattern 12a, 12b Opening 13 Connection

Claims (1)

(57) [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 so as to be electrically connected to the wiring conductor, and wider than the wiring conductor. A connection pad, and a ground conductor or a power supply conductor arranged to face the wiring conductor and the connection pad with an insulating layer interposed between the insulating base, and the ground conductor or the power supply conductor faces the connection pad. A circuit board, wherein a width of a portion to be formed is narrower than a width of a portion facing the wiring conductor.