JPH09298347A - Printed wiring board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent stray capacitance from being formed in circuits by forming a grounded third conductor pattern layer facing the opposite surface of a second conductor pattern layer to a circuit pattern of a first conductor pattern layer; the second layer having insulation regions facing at this circuit pattern. SOLUTION: The printed wiring board 50 mounts circuit parts 6 on parts mounting faces 51, 52 of the surfaces of boards. The mounting faces 51, 52 and conductor earth layers 53, 54 are laminated through insulative epoxy resin layers inserted therebetween to form a laminate structure printed wiring board. On one parts mounting face 51 the parts 6 are connected through conductors to a circuit pattern 6A to form VCO circuits. The lower earth layer 53 facing the circuit pattern 6A through an epoxy material forms insulation regions 53A by removing the conductor pattern at areas facing the VCO circuits 22.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printed wiring board, and is preferably applied to a high-frequency oscillation circuit such as a VCO (Voltage Controlled Oscillator) circuit provided in a transmitting / receiving section of a digital cordless telephone.

[0002]

2. Description of the Related Art Conventionally, when a high frequency (RF, Radio Frequency) circuit such as a voltage controlled oscillation (VCO) circuit used in a transmitting circuit or a receiving circuit of a mobile phone is constructed on a thin multi-layer substrate, A high frequency printed wiring board 1 as shown in FIG. 3 is used. This kind of printed wiring board 1
Has, for example, four conductor pattern layers. In this case, the printed wiring board 1 has front and back surface layers on the component surfaces 2 and 3
As the high frequency circuit 6, the ground layers 4 and 5 composed of two conductor pattern layers are laminated between them by interposing an epoxy resin which is an insulating substrate material therebetween.

In this way, two ground layers are provided between the component surfaces 2 and 3 to shield electromagnetic radiation from each other between the high frequency circuits 6 mounted on the component surfaces 2 and 3, respectively (shield). Here, the ground layer has two layers because the signal line may be provided on either one of the ground layers in order to enhance the shield effect.

[0004]

By the way, in the conventional printed wiring board 1 as described above, the component surfaces 2 and 3 on which the high frequency circuit 6 is formed in order to downsize the device.
And the ground layers 4 and 5 immediately thereunder are formed very close to each other. Therefore, a large stray capacitance C _ST is generated between layers provided by inserting the epoxy resin layer between the circuit pattern 6A of the high frequency circuit 6 and the ground layer 4 or 5.

As a result, for example, VC
When forming a high frequency circuit such as an O circuit, (1) the frequency change with respect to the voltage change becomes small (that is, the VCO sensitivity becomes low), or (2) the control when the oscillation frequency is changed by changing the control voltage. There is a problem that the frequency change with respect to the voltage becomes discontinuous and the oscillation becomes discontinuous. The present invention has been made in consideration of the above points, and it is possible to prevent stray capacitance from occurring between the conductor pattern layers which are laminated in multiple layers, which causes a capacitive defect in a circuit formed on the conductor pattern layers. It is intended to propose a printed wiring board that can be prevented.

[0006]

In order to solve the above problems, according to the present invention, in a printed wiring board in which at least three or more conductor pattern layers including a surface conductor layer are laminated with insulating layers interposed therebetween, a component A first conductor pattern layer on which a circuit pattern for mounting the circuit pattern is formed, and a second conductive pattern layer having an insulating region corresponding to a portion facing the circuit pattern.
And a third conductor pattern layer facing the surface of the second conductor pattern layer opposite to the side where the first conductor pattern layer is formed and grounded. . Thereby, the third conductor pattern layer is made to face the circuit pattern of the first conductor pattern layer on which the circuit is formed, the gap between the conductor pattern layers is widened, and the circuit formed on the first conductor pattern layer. On the other hand, it is possible to prevent a stray capacitance that causes a capacitive defect from occurring between layers.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION

An embodiment of the present invention will be described in detail with reference to the drawings.

(1) Configuration of Transmitter / Receiver Circuit of Digital Cordless Telephone In FIG. 1, reference numeral 10 indicates a transmitter / receiver circuit of a mobile telephone as a whole, and a circuit is formed by a high frequency circuit such as a VCO circuit. In the transmission / reception circuit 10, the reception signal S1 received by the antenna 12 is transmitted to the band pass filter (BPF, Band).
After the band is limited through the Pass Filter, the transmission path is switched to the receiving unit 15 side by the switch (SW) 14 and is transmitted.

In the receiving unit 15, a low noise amplifier
The reception signal S1 amplified by the (LNA, Low Noise Amplifier) 16 is sent to the first mixer 18 after passing through the BPF 17. A local oscillation signal S2 is sent from the local oscillation circuit 20 to the mixer 18 via a buffer amplifier (BF, Buffer Amplifier) 21. In the mixer 18, the local oscillation signal S2 and the reception signal S1 are mixed and converted into the first intermediate frequency signal S _IF .

Here, the local oscillator circuit 20 is formed by a swallow counter, and the frequency whose voltage is controlled by the VCO circuit 22 is phase-locked by a PLL (Phase Locked Loop) circuit 23 to low-pass filter (LPF, Low). Pass Fil
ter) 24 and feed back to the PLL circuit 23 via BA 25 to generate the local oscillation signal S2. Like this VCO
Since the oscillation frequency of the circuit 22 is controlled by the signal passed through the LPF 24, it is desirable that the frequency variable range has a margin. That is, it is required to maintain stable oscillation within the required frequency range and to prevent the oscillation from jumping discontinuously when the oscillation frequency is voltage controlled.

The intermediate frequency signal S _IF is narrowed by the BPF 27 and then sent to the second mixer 28. To the mixer 28 is the reference carrier wave S3 from the local oscillation circuit 29 comprising a crystal oscillator or the like is transmitted, to generate a second intermediate frequency signal S _IF2 by being mixed with the intermediate frequency signal S _IF. By adopting such a double super heterodyne system, the selectivity of the reception frequency can be increased. The intermediate frequency signal S _IF2 is sent to the detector (DET, Detector) 31 via the BPF 30, where the phase detection is performed, and then the demodulated signal S10 is output to the subsequent stage.

On the other hand, in the transmitter 35, the input terminal IN
Transmit data S20 input from the modulator (MOD, Modulat
or) 36, and the resulting modulated signal S
21 is sent to the mixer 37. The modulation signal S21 is mixed in the mixer 37 with the local oscillation signal S2 sent from the local oscillation circuit 20 via the _{BA 38,} and converted into the intermediate frequency signal S _IF3 . The intermediate frequency signal S _IF3 is BPF3.
After the band is narrowed through 9, the power amplifier (Power Amplifier
Itier) 40 power is amplified by SW14 and BP
It is transmitted from the antenna 12 via F13.

(2) High Frequency Printed Wiring Board The VCO circuit 22 having a high frequency circuit structure forming a part of the local oscillation circuit 20 of the transmission / reception circuit 10 as described above oscillates a high frequency of approximately several GHz (gigahertz). Is formed on the high frequency printed wiring board 50 as shown in FIG. The printed wiring board 50 is a double-sided mounting type printed wiring in which circuit patterns of conductors are formed on the component surfaces 51 and 52 on both front and back surfaces of a printed circuit board, and the circuit components 6 are mounted on the component surfaces 51 and 52 on the board surface, respectively. It is a plate. This printed wiring board 50 has component surfaces 51 and 52.
And the ground layers 53 and 54 of the conductor are laminated by inserting an insulating epoxy resin layer therebetween to form a multilayer printed wiring board. In this way, the printed wiring board 50
Is provided with two layers of ground layers 53 and 54 between the component surfaces 51 and 52, and by connecting the ground layers 53 and 54 to the ground, electromagnetic waves between the circuits formed on the component surfaces 51 and 52, respectively. Shields mutual interference due to radiation.

On one component surface 51 of the printed wiring board 50, the circuit component 6 is conductor-connected to the circuit pattern 6A and VC
The O circuit 22 is formed. At this time, the ground layer 53 immediately below the VCCO circuit 22 formed on the component surface 51 by inserting an epoxy material and facing the circuit pattern 6A is VC.
The insulating pattern 53A is formed by hollowing out the conductor pattern in the portion facing the O circuit 22. As a result, the component surface 5
The gap between the insulating layer 1 and the ground layer 53 is expanded to the component surface 51 and the ground layer 54 so that the stray capacitance generated between layers in this portion is sufficiently small. This makes it possible to increase the VCO sensitivity of the VCO circuit 22 and prevent the oscillation from jumping when the oscillation frequency is changed by voltage control to realize a continuous and linear VCO characteristic.

In the above structure, the local oscillation signal S2 is supplied from the local signal oscillation circuit 20 to the receiving unit 15 or the transmitting unit 35 when receiving or transmitting a radio wave. At this time, in the local signal oscillation circuit 20, the frequency of the local oscillation signal is voltage-controlled by the VCO circuit 22 based on the signal transmitted through the LPF 24. Here, in the printed wiring board 50 on which the VCO circuit 22 is formed, the lower layer immediately facing the circuit pattern 6A on the VCO circuit 22 formed on the component surface 51 by inserting an epoxy material serving as an insulating layer. An insulating region 53A is formed by hollowing out the conductor pattern in the facing region of the ground layer 53.

As a result, for the portion where the circuit pattern 6A of the VCO circuit 22 is formed, the insulating layer and the insulating region 53A are formed.
Is inserted so that the ground layer 54 faces each other, and the space between the conductor pattern layers is widened. As a result, the inter-layer stray capacitance C _ST that causes a capacitive defect in the VCO circuit 22 formed on the printed wiring board 50 is made extremely small. Further, in this case, since the two ground layers 53 and 54 are formed by the conductor pattern layer connected to the ground, even when a part of the ground layer 53 is hollowed out, the other ground layer 54 allows the component surfaces 51 and 52. It is sufficiently shielded against electromagnetic radiation between.

As a result, in the local oscillator circuit 20, V
The oscillation frequency is controlled by the CO circuit 22, and the
In the PLL of the L circuit 23, the lock-up time until the frequency is locked is printed by the printed wiring board 5.
It is possible to prevent the delay due to the stray capacitance generated at 0 and increase the VCO sensitivity. Further, in the VCO circuit 22, when the control voltage is continuously changed to change the oscillation frequency, it is possible to construct a circuit having continuous and linear VCO characteristics with no oscillation frequency jump.

According to the above construction, in the printed wiring board 50 in which four conductor pattern layers are laminated alternately with the insulating layers, the component surface of the ground layer 53 immediately below, which faces the component surface 51 with the insulating layer interposed therebetween, VCO circuit 22 formed on 51
The conductor pattern area corresponding to the circuit pattern area of
The circuit pattern 6 is provided between the conductor pattern layers corresponding to the circuit 22.
The layer interval is widened from between A and the ground layer 53 to between the circuit pattern 6A and the ground layer 54. As a result,
The stray capacitance C _ST that causes a capacitive defect in the VCO circuit 22 is suppressed to a low level, and the VCO characteristics when the voltage is continuously changed to change the oscillation frequency are continuous without oscillation of the oscillation frequency, and It can have a linear change characteristic. In addition to this, since the influence of the stray capacitance, which is a distributed constant circuit, is reduced, there is an advantage that the VCO circuit can be easily constructed only by the theory of the lumped constant circuit.

In the above embodiment, the case where the VCO circuit of the digital cordless telephone is formed has been described, but the present invention is not limited to this, and can be applied to an amplifier circuit other than the oscillation circuit such as the VCO circuit. . Further, the circuit is not limited to a digital circuit, but may be an analog circuit, and the point is that it can be widely applied to those which generally form a high-frequency circuit, and thereby the same effect as that of the above-described embodiment can be obtained. Further, it can be widely applied to circuits other than the high frequency circuit. Further, in the above-described embodiment, the case where a part of the conductor pattern of the earth layer facing the component surface on which the high frequency circuit is formed is hollowed out to form an insulating region, but the present invention is not limited to this and, for example, a high frequency The hollowed-out portion of the ground layer facing the area where the circuit is formed may be filled with an insulating material such as an epoxy resin which is a material for the printed wiring board.

Further, in the above-mentioned embodiment, the case where the printed wiring board in which the conductor pattern layers are laminated in four layers including the front and back surfaces of the components is used is described, but the present invention is not limited to this, and the essential point is. By applying the present invention to a multi-layered substrate provided with two or more ground layers including the substrate surface layer (that is, including a single-sided mounting type), the same effects as those of the above-described embodiments can be obtained.

[0022]

As described above, according to the present invention, in a printed wiring board in which at least three or more conductor pattern layers including a surface conductor layer are laminated with insulating layers interposed therebetween,
A first conductor pattern layer on which a circuit pattern for mounting components is formed, a second conductor pattern layer having an insulating region corresponding to a portion facing the circuit pattern, and a second conductor pattern layer of the second conductor pattern layer. A first conductor pattern layer on which a circuit is formed, by including a third conductor pattern layer facing the surface opposite to the side on which the first conductor pattern layer is formed and grounded. Such that the third conductor pattern layer faces the third circuit pattern layer and the space between the conductor pattern layers is expanded to cause a capacitive defect in the circuit formed on the first conductor pattern layer. It is possible to realize a printed wiring board that can prevent generation of stray capacitance between layers.

[Brief description of drawings]

FIG. 1 is a block diagram showing a circuit configuration of a transmission / reception unit of a digital cordless telephone.

FIG. 2 is a cross-sectional view showing a configuration of a printed wiring board according to an example.

FIG. 3 is a cross-sectional view showing a configuration of a conventional printed wiring board.

[Explanation of symbols]

1, 50 ... Printed wiring board, 2, 3, 51, 52 ...
Component surface 4, 5, 53, 6 ... High-frequency circuit, 54 ... Ground layer, 6A ... Circuit pattern, 53A ... Insulation area.

Claims (3)

[Claims] 1. A printed wiring board in which at least three or more conductor pattern layers including a surface conductor layer are laminated with an insulating layer interposed therebetween, and a first circuit pattern for mounting components is formed. A conductor pattern layer, a second conductor pattern layer having an insulating region corresponding to a portion facing the circuit pattern, and a side of the second conductor pattern layer on which the first conductor pattern layer is formed. And a third conductor pattern layer facing the surface on the opposite side and grounded, the printed wiring board. 2. The printed wiring board according to claim 1, wherein the insulating layer is formed corresponding to the shape of the circuit pattern. 3. The printed wiring board according to claim 1, wherein the second conductor pattern layer is grounded.