JP2005286436A - High frequency wiring board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problems wherein unneeded capacitance components are generated between a through conductor formed at a prescribed interval along a signal transmission direction and the adjacent signal line, and the minute mismatching of the characteristic impedance of respective paired signal lines at a part in which the through conductor is present causes large mismatching as the characteristic impedance of a differential signal line. <P>SOLUTION: A plurality of through conductors 7 formed in a row are formed in parallel with the direction of a line are formed at both the sides of the differential signal line 8 comprising a pair of signal lines formed in parallel on the upper surface of a dielectric substrate 2, the arrangement interval of the through conductors 7 is 1/4 or smaller of the wavelength of a high-frequency signal transmitted by the differential signal line 8, and a cutout is formed at a part positioned between the differential signal line 8 and the through conductor 7 at a side opposite to the differential signa line 8 in an identical plane grounding conductor layer 5. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a high-frequency circuit board provided for the purpose of impedance matching or the like between a high-frequency circuit component such as an IC or LSI or a high-frequency circuit device used in a high-frequency band in the GHz band and an input / output unit. The present invention relates to a high-frequency wiring board having a differential signal line structure with improved transmission characteristics.

  With recent increases in communication technology with higher frequencies and larger capacities, communication devices such as ICs, LSIs, and semiconductor lasers (PDs: Photo Diodes) are operating at higher frequencies, and these communication devices are mounted. Also in a signal line formed on a package or a circuit board on which the package is mounted, it is necessary to transmit a higher frequency high frequency signal with low loss. For this reason, the signal line in the package of the communication device and the signal line of the circuit board must be manufactured as a transmission line for high frequency. As the number of input / output terminals of communication devices such as MUX (Multiplexer), DEMUX (Demultiplexer), and NPU (Network Processor Unit) increases, the number of signal lines on the package and circuit board jumps. Is increasing. Therefore, the signal lines must be formed with high density, and the interval between the signal lines is naturally narrowed. However, if signal lines that transmit high-frequency signals are placed close to each other, noise is generated due to parasitic components generated between the signal lines, particularly electrical capacitance (stray capacitance) between the signal lines and mutual inductance. There has been a problem that transmission loss increases due to deterioration of the transmission and occurrence of crosstalk.

Therefore, as shown in Patent Document 1, in a high-frequency wiring board in which a differential signal line composed of two signal lines is provided in parallel to the upper surface of a dielectric substrate, between adjacent differential signal lines, It has been proposed to reduce noise caused by electromagnetic interference between adjacent differential signal lines by forming through conductors connected to the ground conductor layer or power supply conductor layer at predetermined intervals along the signal transmission direction. Yes.
JP 2003-224408 A

  However, in the conventional high-frequency wiring board, an unnecessary capacitance component is generated between the through conductor formed at a predetermined interval along the signal transmission direction and the signal line adjacent to the through conductor, and the through conductor exists. The characteristic impedance of the signal line is lowered at the location where the signal is applied. In the case of a differential signal line, the sum of the characteristic impedances of each signal line forming a pair becomes the characteristic impedance of the differential signal line. There is a problem that a minute mismatch in the characteristic impedance of each signal line causes a large mismatch as a characteristic impedance of the differential line.

  The present invention has been completed in order to solve the above problems, and its purpose is to reduce noise due to electrical interference between differential signal lines, and to match the characteristic impedance of the differential signal lines, It is to reduce reflection loss and transmission loss of high-frequency signals.

  The high-frequency wiring board of the present invention includes a differential signal line composed of a pair of signal lines formed in parallel with each other between the upper surface of a dielectric substrate formed by laminating a plurality of dielectric layers or between the dielectric layers; The same-surface ground conductor layer formed on both sides of the differential signal line with a predetermined interval; the lower-surface conductor layer formed on the entire lower surface of the dielectric substrate; the same-surface ground conductor layer and the lower-surface conductor layer; A plurality of through conductors that are electrically connected and formed in rows on both sides of the differential signal line in parallel with the line direction, and the plurality of through conductors are arranged in the line direction. The interval is equal to or less than a quarter of the wavelength of the high-frequency signal transmitted through the differential signal line, and the coplanar ground conductor layer includes the through conductor on the side facing the differential signal line and the differential. Parts located between signal lines Wherein the notch is formed.

  The high-frequency wiring board of the present invention is preferably characterized in that the notch has an arc shape.

  The high-frequency wiring board of the present invention is preferably characterized in that a plurality of the differential signal lines are formed in parallel.

  The high-frequency wiring board of the present invention is formed in rows on both sides of a differential signal line composed of a pair of signal lines formed in parallel with each other on the upper surface or between layers of the dielectric substrate in parallel with the line direction. A plurality of through conductors are formed, and the arrangement interval of these through conductors is set to ¼ or less of the wavelength of the high-frequency signal transmitted through the differential signal line. Since the conductor wall is formed and the coupling (coupling) of the electric field generated between the differential signal line and other adjacent signal lines can be suppressed, the noise due to electromagnetic interference is reduced. Can do. Furthermore, since the notched portion is formed in a portion located between the through conductor on the side facing the differential signal line and the differential signal line, the same-surface ground conductor layer is formed between the through conductor and the signal line. The decrease in characteristic impedance due to the unnecessary capacitance component between the two can be offset by the increase in characteristic impedance due to the decrease in the capacitance component between the notch on the ground conductor layer and the differential signal line. The characteristic impedance of the line can be made uniform.

  Further, in the case of the high frequency wiring board of the present invention, when the cutout portion has an arc shape, the traveling direction of the signal transmitted to the differential signal line on the side facing the differential signal line of the same-surface ground conductor layer The flow of the return current flowing in the opposite direction can be made smooth, and unnecessary electromagnetic radiation can be suppressed.

  The high-frequency wiring board of the present invention can cope with an increase in the number of input / output terminals of communication devices such as MUX, DEMUX, NPU, etc., when a plurality of differential signal lines are formed in parallel.

  The high-frequency wiring board of the present invention (hereinafter also referred to as a high-frequency board) will be described in detail below. 1A, 1B, and 1C are a plan view and a cross-sectional view showing an example of an embodiment of a high-frequency substrate according to the present invention. In these figures, 1 is a high-frequency substrate, 2 is a dielectric substrate, 3 is a first signal line forming a differential signal line 8, 4 is a second signal line forming a differential signal line 8, and 5 is the same surface contact. A ground conductor layer, 6 is a bottom conductor layer, and 7 is a through conductor.

  The high-frequency substrate 1 of the present invention includes a differential signal line 8 formed of two parallel signal lines 3 and 4 formed on the upper surface of a dielectric substrate 2, and the same surface contact formed on both sides of the differential signal line 8. The ground conductor layer 5, the lower conductor layer 6 formed on the entire lower surface of the dielectric substrate 2, the same-surface ground conductor layer 5 and the lower conductor layer 6 are electrically connected and the line direction of the differential signal line 8 A plurality of through conductors 7 formed in rows in parallel to each other, and the arrangement interval of the through conductors 7 in the line direction of the differential signal line 8 is a high-frequency signal transmitted through the differential signal line 8. The same-surface ground conductor layer 5 has a notch portion at a portion located between the through conductor 7 on the side facing the differential signal line 8 and the differential signal line 8. Has been. Thus, the differential signal line 8 and the same-surface ground conductor layer 5 and the lower conductor layer 6 constitute a coplanar line.

  And since the arrangement | positioning space | interval of the penetration conductor 7 in the line direction of the differential signal track | line 8 is below 1/4 of wavelength (lambda) of the high frequency signal transmitted with the differential signal track | line 8, A pseudo conductor wall is formed, and the capacitive coupling between the adjacent differential signal lines 8 can be reduced. As a result, crosstalk noise between the adjacent differential signal lines 8 is reduced.

  Further, in the high-frequency substrate 1 of the present invention, specifically, the same-surface ground conductor layer 5 is a portion located between the through conductor 7 on the side facing the differential signal line 8 and the differential signal line 8. A notch is formed in a portion that is orthogonal to the line direction and is located on a line passing through the through conductor 7. As a result, the decrease in characteristic impedance due to an unnecessary capacitance component between the through conductor 7 and the differential signal line 8 is reduced by the capacitance component between the notch portion of the ground conductor layer 5 and the differential signal line 8. It can be offset by the increase in characteristic impedance due to the decrease. As a result, there is little signal degradation due to characteristic impedance mismatch, and good high frequency characteristics can be obtained.

  Further, the distance between the first signal line 3 and the second signal line 4 is equal to or less than a quarter of the wavelength λ of the high-frequency signal, and the first signal line 3 and the second signal line 4 and electromagnetically couple to function as the differential signal line 8.

  The distance between the left and right through conductors 7 that connect the left and right same-surface ground conductor layers 5 and the lower conductor layer 6 formed with the differential signal line 8 interposed therebetween is preferably equal to or less than the wavelength λ of the high-frequency signal. In this case, the coupling of the electric field between the first signal line 3 and the second signal line 4 is further strengthened, and better transmission characteristics of high-frequency signals are realized in the differential signal line 8 having a coplanar line structure. The

Examples of the material of the dielectric substrate 2 in the high-frequency substrate 1 of the present invention include ceramics such as alumina (Al ₂ O ₃ ) ceramics and mullite (3Al ₂ O ₃ · 2SiO ₂ ) ceramics, inorganic materials such as glass ceramics, and tetrafluoride. Ethylene resin (polytetrafluoroethylene; PTFE), tetrafluoroethylene-ethylene copolymer resin (tetrafluoroethylene-ethylene copolymer resin; ETFE), tetrafluoroethylene-perfluoroalkoxyethylene copolymer resin (tetrafluoroethylene- A fluorocarbon resin such as perfluoroalkyl vinyl ether copolymer resin (PFA) or the like, a glass epoxy resin, a polyphenylene ether resin, a liquid crystal polyester, a resin material such as polyimide, or the like is used. The shape and dimensions (thickness, width, length) of the dielectric substrate 2 are appropriately set according to the frequency of the high-frequency signal, the characteristic impedance, and the like.

The first signal line 3 and the second signal line 4 of the present invention are made of a metal conductor layer suitable for high-frequency signal transmission, for example, on a Cu layer, a Mo—Mn layer, a W layer, or a Mo—Mn metallized layer. With a Ni plating layer and an Au plating layer deposited thereon, a W metallized layer with a Ni plating layer and an Au plating layer deposited thereon, a Cr—Cu alloy layer, a Ni plating layer on a Cr—Cu alloy layer And an Au plated layer deposited, a Ni—Cr alloy layer and an Au plated layer deposited on a Ta ₂ N layer, a Pt layer and an Au plated layer deposited on a Ti layer, Or it consists of what deposited Pt layer and Au plating layer on the Ni-Cr alloy layer, and is formed by the thick film printing method or various thin film formation methods, plating methods, etc. The thickness and width are also set according to the frequency and characteristic impedance of the transmitted high frequency signal.

  The same-surface ground conductor layer 5 and the lower conductor layer 6 may be formed of the same material as that of the first signal line 3 and the second signal line 4 by the same method and the same as the differential signal line 8. The distance between the surface ground conductor layer 5 and the distance between the differential signal line 8 and the lower surface conductor layer 6 are appropriately set according to the frequency of the high frequency signal, the characteristic impedance of the differential signal line 8, and the like.

  The plurality of through conductors 7 that electrically connect the same-surface ground conductor layer 5 and the lower conductor layer 6 are made of through-hole conductors or via-hole conductors, or are embedded with a metal plate, metal rod, metal pipe, or the like. Is provided.

  The high frequency substrate 1 of the present invention is manufactured as follows. When the dielectric substrate 2 is made of alumina ceramic, first, an alumina ceramic green sheet to be the dielectric substrate 2 is prepared, and a predetermined punching process is performed on the green sheet to form a through hole to be the through conductor 7. After that, a conductive paste such as W or Mo is filled in the through holes by screen printing, and a conductor pattern that becomes the first signal line 3 or the second signal line 4 and a conductor pattern that becomes another conductor layer are printed. Apply. Next, baking is performed at 1600 ° C., and finally, Ni plating and Au plating may be performed on each conductor layer.

  When the differential signal line 8 and the same-surface ground conductor layer 5 are formed between the dielectric layers of the dielectric substrate 2, the upper and lower surface conductor layers are formed on the upper and lower main surfaces of the dielectric substrate 2, and the through conductor 7 is the same. A structure in which the surface ground conductor layer 5 and the upper and lower surface conductor layers are electrically connected is preferable.

  Note that the present invention is not limited to the above-described embodiment, and various modifications may be made without departing from the scope of the present invention. For example, the notch formed in the ground contact conductor layer 5 is not limited to a rectangular shape or an arc shape, but may be a trapezoidal shape, a triangular shape, or the like.

  Moreover, it is preferable that the length in the line direction of a notch part is the same as the width | variety (diameter) of the penetration conductor 7, or is larger than the width | variety of a penetration conductor. In this case, the capacitance component generated between the through conductor and the signal line can be more reliably reduced.

  Furthermore, when the cutout portion has an arc shape and the cross-sectional shape of the through conductor 7 is circular, the radius of curvature of the cutout portion is preferably larger than the diameter of the through conductor 7. In this case, the density of electric lines of force generated between the signal line and the edge of the notch can be reduced, and the coupling between the notch and the signal line is weakened and generated between them. The capacitance component can be reduced more reliably.

(A) is a top view which shows an example of embodiment about the high frequency wiring board of this invention, (b) is sectional drawing in the AA 'line of (a), (c) is B of (a) It is sectional drawing in the -B 'line. It is a top view which shows the other example of embodiment about the wiring board for high frequencies of this invention.

Explanation of symbols

1: High-frequency wiring board 2: Dielectric substrate 3: First signal line 4: Second signal line 5: Coplanar ground conductor layer 6: Bottom conductor layer 7: Through conductor 8: Differential signal line

Claims (3)

A differential signal line composed of a pair of signal lines formed in parallel with each other between the upper surface of the dielectric substrate formed by laminating a plurality of dielectric layers or between the layers of the dielectric layers, and predetermined on both sides of the differential signal line The differential ground conductor layer formed at intervals, the lower conductor layer formed on the entire lower surface of the dielectric substrate, and the differential ground conductor layer and the lower conductor layer are electrically connected and the differential A plurality of through conductors formed in rows on both sides of the signal line in parallel with the line direction, and the plurality of through conductors are transmitted in the differential signal line at an arrangement interval in the line direction. Is equal to or less than a quarter of the wavelength of the high-frequency signal, and the coplanar ground conductor layer is located at a portion located between the through conductor on the side facing the differential signal line and the differential signal line. Features a notch High-frequency wiring board. 2. The high frequency wiring board according to claim 1, wherein the notch has an arc shape. 3. The high-frequency wiring board according to claim 1, wherein a plurality of differential signal lines are formed in parallel.

Images