JPH10145112A - Wiring board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To change the characteristic impedance of wiring, to form micro-, mill-wave band elements with a simple constitution and the provide a wide-band antenna with few losses by forming the pattern of a ground conductor layer in two areas different in opening areas per unit area and characteristic impedance. SOLUTION: Two copper first supply line patterns 3 of characteristic impedance 100Ω are branched from the copper second feed line pattern 4 of characteristic impedance 50Ω. Patch patterns 2 of a microstrip antenna are connected to the feed line patterns 3. A ground conductor layer 6 is grounded to the inner layer of the board through a dielectric layer 5, and the pattern changes the opening area per unit area in the two areas 17 and 18. Characteristic impedance forms the different areas. The ground conductor layer 11 is formed at the back plane of the board. Thus, the losses can be reduced be about 0.6dB with such a constitution, as compared to a structure where the ground conductor layer is covered by the same pattern as all the areas 17.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wiring board,
In particular, the present invention relates to a wiring board suitable for a high-frequency antenna substrate such as a microwave band or a millimeter wave band, and a transmission line substrate.

[0002]

2. Description of the Related Art In recent years, with the development of the information society, the demand for wireless lines such as high-speed wireless LANs and personal satellite communications has been increasing. In order to meet this demand, research and development for the use of a microwave band or a millimeter wave band, which has a wide communication band and a large number of channels, are being actively conducted. In a circuit using such a high-frequency band, not only the characteristics of the circuit elements but also the characteristics of the high-frequency wiring connecting the circuit elements often affect the performance of the circuit.

Conventionally, as a wiring board for a high-frequency circuit,
As shown in FIG. 6A, the ground wiring layer 102 is
6B, a microstrip line structure having a structure provided on one side of the signal wiring layer 101 via a signal line 101 or a strip line (in a narrow sense) in which the ground wiring layer 102 is disposed on both surfaces of the signal wiring 101 as shown in FIG. Structure is taken. Further, as shown in FIG. 6C, there is also a structure in which the electrodes of the ground wiring layer 102 are formed wide in a mesh shape. FIG. 6 (a),
(B) and (c) are generally referred to as strip lines in a broad sense. In such a stripline wiring structure, the characteristic impedance of the signal wiring 101 is controlled by changing the type and thickness of the dielectric (insulator) 103.

Further, an antenna using a microstrip line structure, that is, a microstrip antenna has been actively studied. In the microstrip antenna, since the radiation element and the feed line are formed on the same plane, a small antenna device can be obtained relatively easily. The problem with the microstrip antenna is that the radiating element has a narrow band and the efficiency is reduced due to the loss of the feed line.

[0005] As an attempt to solve the problem,
IEICE Transactions, Vol. J72-B-II N
o. 6 pp. 236-244 A printed antenna having a two-layer structure is proposed in "2-layer Printed Antenna for Satellite Broadcast Reception". FIG. 7 shows this two-layered printed antenna. In FIG. 7, reference numeral 51 denotes a patch pattern serving as a radiating element, 52 denotes a feed line, and these are formed on the surface of a dielectric substrate 53. On the back side of the dielectric substrate 53, a ground conductor 5 formed in contact with the dielectric substrate is provided.
4 and a ground conductor block 55 separate from the ground conductor 54 are connected to form a ground conductor surface. A gap 56 is provided below the radiating element 51. By providing this gap, the band of the antenna can be widened. On the other hand, the thickness of the dielectric substrate in the portion of the feed line 52 is constant, and the characteristic impedance of the feed line is controlled by increasing or decreasing the width of the feed line. The thickness of the dielectric substrate 53 is selected so that the loss generated in the feeder line 52, that is, the sum of the conductor loss, the radiation loss, and the dielectric loss is minimized.

By adopting the above configuration, the thickness of the dielectric substrate can be selected so as to optimize the characteristics of the radiating element and the feed line, and the antenna characteristics can be reduced over a wider band with lower loss. However, there are still problems as described below.

That is, the thickness of the dielectric is selected for the power supply line portion so as to minimize the above-mentioned loss. However, if the dielectric substrate is to be formed by a thin film process, the optimum thickness is reduced due to the process. It may not be possible. Further, when an antenna is arrayed, high-impedance wiring is required. However, if an attempt is made to reduce the width of the wiring in order to obtain it, this may not be able to be formed due to the process.

In the antenna device shown in FIG. 7, a dielectric substrate and a ground conductor block are separately formed in order to form a gap below the radiating element. Therefore, they must be finally attached. for that reason,
It also has the disadvantage that the manufacturing process becomes complicated and the manufacturing cost increases.

[0009]

As described above, the conventional wiring board has a problem that it is difficult to secure the characteristics of the wiring when the thickness of the dielectric layer constituting the strip line is reduced.

For this reason, in the application to various microwave band and millimeter wave band elements such as an antenna device using a conventional wiring board, the production cost is increased, the thin film process is difficult, and the fine patterning such as arraying is required. There is a problem that it is difficult to secure the characteristics when advanced.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to provide a high-frequency wiring board capable of freely changing the characteristic impedance of wiring without using a complicated manufacturing process. I do.

Another object of the present invention is to use a wiring board whose characteristic impedance can be easily designed so that an antenna which can be easily miniaturized, has a small loss, and can achieve wideband characteristics can be achieved without using a complicated manufacturing process. Equipment, matching circuits,
An object of the present invention is to provide a microwave band device such as a coupling line or a millimeter wave band device.

Still another object of the present invention is to provide a wiring board which can easily design and process a surface pattern and can reduce a mounting area as a whole.

[0014]

In order to achieve the above object, the present invention provides a dielectric layer, a surface conductor layer (or a center conductor layer) disposed on the surface of the dielectric layer, and a dielectric layer. A strip line structure comprising a ground conductor layer disposed on the back surface of the wiring board, wherein at least one of a pattern shape of the ground conductor layer or a thickness of the dielectric layer is different from each other so as to provide a predetermined characteristic impedance. It has two or more regions set to values. The present invention can be applied to a narrowly defined stripline structure in which the periphery of the surface conductor layer (center conductor layer) is surrounded by a dielectric layer as shown in FIG. 6B, but in practice, FIG. It is preferably used for a microstrip line structure as shown in FIG.

Here, the "ground conductor layer" means a conductor layer located closest to the surface conductor layer (center conductor layer), and even if another conductor layer exists further below the ground conductor layer. The other conductor layer is not the ground conductor layer according to the present invention. Because it is shielded by the ground conductor layer, the electric lines of force from the surface conductor layer do not reach the other conductor layer located far away, and have substantially no effect on the characteristic impedance of the microstrip line It is. The ground conductor layer may be used as a ground potential line, or may be used as a power supply line having a predetermined potential other than the ground potential. The “surface conductor layer” is a concept including various wiring patterns such as a stub of a matching circuit and a wiring near a patch pattern of an antenna device, and does not mean only a surface conductor layer of a transmission line. According to the present invention, it is possible to obtain two or more regions having different characteristic impedances with respect to the surface conductor layer having the same shape. Conversely, by changing the pattern of the surface conductor layer, it is also possible to make the characteristic impedances of the wiring boards in two adjacent regions approximately equal. That is, the design and adjustment of the desired characteristic impedance becomes extremely easy.

Therefore, in a conventional wiring board having a constant characteristic impedance, the transmission line, for which it was difficult to adjust the impedance or match the impedance due to a problem in processing technology or the like, is changed to a pattern shape of the ground conductor layer. Alternatively, by changing and setting the thickness of the dielectric layer, it is possible to easily design and manufacture.

In the present invention, it is preferable that the wiring board has two or more regions having different aperture ratios per unit area of the ground conductor layer. For example, in a mesh shape such as a square, a rectangle, or a hexagon, two regions having different opening areas may be arranged adjacent to each other. Alternatively, in a mesh pattern of the same pitch, a different aperture ratio can be realized even if the width of the wiring forming the mesh is changed. From the viewpoint of ease of pattern design, the mesh may be designed using a mesh pattern in which one has an integral multiple of the pitch of the other, but it is needless to say that the mesh need not be an integral multiple.

The present invention is preferably used for an antenna device having a microstrip line structure. That is, the patch pattern on the surface of the dielectric layer and the feed line pattern connected to this patch pattern are referred to as “surface conductor layer” of the present invention.
It is sufficient to change the pattern shapes of the ground conductor layer below the first power supply line pattern near the patch pattern and the ground conductor layer below the second power supply line pattern at a certain distance from the patch pattern. Alternatively, the thickness of the dielectric layer between the first power supply line pattern and the ground conductor layer is set so that the distance between the second power supply line pattern and the ground conductor layer is different from each other. Good. According to the present invention, when an antenna device such as an array antenna or a feed line having a different characteristic impedance such as an impedance matching circuit is formed, the loss of each line can be minimized.

The ground conductor layer of the present invention preferably has a mesh pattern. This is because the feed line can be reduced by using the slow wave effect of the mesh pattern (mesh ground), and radiation loss is reduced.

[0020]

Preferred embodiments of the present invention will be described below with reference to the accompanying drawings.

(First Embodiment) FIG. 1A is a perspective view of an antenna device according to a first embodiment of the present invention. FIG. 1A is a top view of a portion corresponding to FIG.
(B). This antenna device has a frequency of 60 GHz.
It is intended for use in the millimeter wave band.

In FIG. 1, reference numeral 2 denotes a patch pattern of the microstrip antenna. There are two patch patterns, each connected by a first feed line pattern 3. The first feed line pattern 3 has a characteristic impedance of 100Ω, and is branched into two from a second feed line pattern 4 having a characteristic impedance of 50Ω.

The ground conductor layers 6 and 11 are provided on the inner layer and the rear face of the substrate.
Are formed. The ground conductor layer 6 corresponds to the “ground conductor layer” of the present invention. The ground conductor layer 6 is provided with the dielectric layer 5 interposed therebetween, and its pattern is formed by changing the opening area per unit area between the two regions 17 and 18 to form regions having different characteristic impedances.

The size of these patterns is such that the patch pattern 2 has a size of about 1.5 mm square, and the signal wirings 3 and 4 as the first and second power supply line patterns have a wiring width of 50 μm.
m, the dielectric layer thickness H1 is 25 μm, and the dielectric layer thickness H2 is 50
0 μm. Conductor thickness T1, T2, T3 are all 3μ
m. The openings 71 and 72 of the ground conductor are
The width of the ground conductor is 50 μm in the region 18 and 90 μm in the region 17. Therefore, the opening area per unit area (1 square millimeter) is about 0.06 square millimeter in the area 17, and the area 1
8 is about 0.34 square millimeters.

The materials used were as follows: all conductor patterns were copper;
The interlayer insulating film 5 has a relative dielectric constant of 2.7 and a dielectric loss tangent of 0.0008.
And a BT resin resin having a relative dielectric constant of 4.5 and a dielectric loss tangent of 0.0075 was used for the interlayer insulating film 9 and the benzocyclobutene resin.

With this structure, the ground conductor layer covers the entire region 17.
As compared with the conventional configuration filled with the same pattern as the above, the loss could be reduced by about 0.6 dB.

FIG. 2 (a) is a perspective view of an antenna device according to a modification of the first embodiment of the present invention, and FIG. 2 (b) is a top view of FIG. 2 (a). This antenna device also has a frequency of 6
It is assumed to be used in the 0 GHz band millimeter wave band.

The antenna device of FIG. 2 is different from the antenna device of FIG. 1 in that a region 14 where the ground conductor layer is formed on the entire surface of the substrate below the second feed line 4 and the first feed line 3 And a lower mesh-shaped region 13. The region 14 is a case where the aperture ratio of the region 17 in FIG. 1 is zero. The mesh pattern in the region 13 has a wiring width of 50 μm and an aperture ratio of 10%. These values are determined by the wiring width and wiring thickness of the first and second power supply lines 3 and 4 and the thickness of the interlayer insulating film 5.

In the antenna device shown in FIG. 2, similarly to the antenna device shown in FIG. 1, the loss in the feed line can be suppressed. Further, the design and adjustment of the characteristic impedance is easy, the production period of the antenna device is shortened, and the yield is improved as in the case of FIG.

(Second Embodiment) FIG. 3 shows a wiring board according to a second embodiment of the present invention. FIG. 3 shows a matching circuit pattern at the input and output of the high-frequency amplifier. FIG. 3A is a top view thereof, and FIG.
It is sectional drawing which follows the AA line in (a). A stub wiring 22 for matching is branched from a signal wiring 21 for high frequency. The ground conductors are provided in two layers of 25 and 26. The ground conductor 25 corresponds to the “ground conductor layer” of the present invention. The ground conductor 25 has a pattern of an opening 30 below the signal wiring 21, and has a pattern of an opening 29 in other places.
As shown in FIG. 3, when the opening of the ground conductor at the portion facing the stub wiring 22 is made large and the opening area per unit area is made large, the effective relative permittivity of the stub wiring becomes large. As a result, a desired electrical length can be achieved with a shorter line length, and the mounting area can be reduced as a whole.

(Third Embodiment) FIG. 4 shows a wiring board according to a third embodiment of the present invention.

FIG. 4 shows a coupling line which is one of the high-frequency circuits.
Are arranged through. Although the ground conductor layer is not shown, two ground layers are provided below the wiring layer as in FIG.
Openings 33, 3 are formed in the ground conductor facing the wiring.
4 are provided. The opening is enlarged in a region below the coupling portion where the gap 32 exists. This allows
Good coupling characteristics can be obtained without reducing the line width of the coupling portion or reducing the gap 32 so much. That is, it is possible to obtain good coupling characteristics even with an ultra-high frequency coupling line requiring an extremely fine pattern without a problem of processing accuracy.

(Fourth Embodiment) FIG. 5A is a perspective view of an antenna device according to a fourth embodiment of the present invention. FIG. 5B is a top view of FIG. This antenna device has a frequency of 60 as in the first embodiment.
The use in the millimeter wave band of the GHz band is assumed.

In FIG. 5, reference numeral 2 denotes a patch pattern of the microstrip antenna. There are two patch patterns, each connected by a first feed line pattern 3. The first feed line pattern 3 has a characteristic impedance of 100Ω and a characteristic impedance of 50Ω.
It is branched from the second feed line pattern 4 of Ω.

In addition to these surface layer patterns, ground conductor patterns 6, 9, and 11 are formed on the inner layer and the rear surface of the substrate. The ground conductor patterns 6 and 9 correspond to the “ground conductor layer” of the present invention. These ground conductor layers are separated by interlayer insulating films 5, 8, and 10 serving as dielectric layers, but are conductive through via holes 7. A cutout pattern 12 is formed in the ground conductor layer 12 below the patch pattern. That is, the ground conductor layer 12 does not exist directly below the patch pattern 2.

The size of these patterns is about 1.5 mm square for the patch pattern 2, the wiring width of the feed line pattern 3 is 40 μm, the wiring width of the feed line 4 is 70 μm, and the dielectric layer thickness H
1 is 25 μm, H2 is 50 μm, and H3 is 500 μm. The conductor thicknesses T1, T2, T3 and T4 are all 3 μm,
The cut pattern 12 of the ground conductor layer 12 is 1.7 mm square. The conductor pattern used was copper, the interlayer insulating films 5 and 8 had a relative dielectric constant of 2.7, and a dielectric tangent of 0.000.
The benzocyclobutene resin of No. 8 and the BT resin having a dielectric constant of 4.5 and a dielectric loss tangent of 0.0075 were used for the interlayer insulating film 10.

In this configuration, when compared with the conventional configuration having a single ground conductor layer, compared to a conventional configuration in which the distance between the patch pattern / feeding pattern and the ground conductor is constant, it is approximately 0.1 mm.
The loss could be reduced by about 6 dB.

The embodiment of the present invention has been described above.
The present invention is not limited to the above embodiment.
Various modifications can be made without departing from the spirit of the present invention.
For example, in the above example, a benzocyclobutene resin and a BT resin are used for the dielectric layer, but a polyimide resin or a Teflon resin may be used. Further, the conductor material is not limited to copper. Although a rectangular pattern is used as a patch pattern of the microstrip antenna, the present invention is not limited to this.

[0039] Combinations of the above embodiments are of course possible, and various modifications can be made without departing from the spirit of the present invention.

[0040]

As described above, according to the wiring board of the present invention, it is easy to design and adjust the characteristic impedance, and various microwave band and millimeter wave band devices can be realized with a simple structure. For example, without using a complicated manufacturing process, it is possible to provide a wideband antenna with a small loss in a feeder line and a high-frequency circuit with a small mounting area.

[Brief description of the drawings]

FIG. 1 is an antenna device according to a first embodiment of the present invention.

FIG. 2 is an antenna device according to a modification of the first embodiment of the present invention.

FIG. 3 shows a matching circuit according to a second embodiment of the present invention.

FIG. 4 is a coupling line according to a third embodiment of the present invention.

FIG. 5 is an antenna device according to a fourth embodiment of the present invention.

FIG. 6 is a diagram showing a structure of a conventional wiring board.

FIG. 7 is a conventional antenna device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Antenna device 2,51 Patch pattern 3,4,52 Feeding line pattern 5,8,10,103 Interlayer insulating film (dielectric layer) 6,9,25,102 Ground conductor (ground conductor layer) 7 Via 11,26 , 54 Ground conductor 12, 57 Ground conductor removal pattern 13, 14, 17, 18 Mesh pattern 21 Signal wiring 22 Stub wiring 29, 30, 33, 34, 71, 72 Opening 31 Signal line 53 Dielectric substrate 55 Ground conductor block 56 gap 101 center conductor (signal wiring)

Claims (2)

[Claims] 1. A strip line structure comprising a dielectric layer, a surface conductor layer or a center conductor layer disposed on a surface of the dielectric layer, and a ground conductor layer disposed on a back surface of the dielectric layer. A wiring substrate having two or more regions in which at least one of a pattern shape of the ground conductor layer or a thickness of the dielectric layer is set to be different from each other so as to provide a predetermined characteristic impedance. substrate. 2. The wiring board according to claim 1, wherein the wiring board has two or more regions having different aperture ratios per unit area of the ground conductor layer.