JP4377725B2 - High frequency wiring board - Google Patents

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 adjacent signal line, and the through conductor exists. In the case of a differential signal line, the total characteristic impedance of each signal line that forms a pair becomes the characteristic impedance of the differential signal line. There is a problem that a minute mismatch in the characteristic impedance of the line causes a large mismatch as a characteristic impedance of the differential signal 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 through conductor on one side of the differential signal line is connected to the line in the upper surface of the dielectric substrate. Other in the direction orthogonal to the direction Is characterized in that the located between the through conductors each other side.

  In the high-frequency wiring board according to the present invention, preferably, the through conductor on one side of the differential signal line has the through hole on the other side in a direction orthogonal to the line direction in the upper surface of the dielectric substrate. It is located in the middle between conductors.

  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 of the electric field generated between the differential signal line and another adjacent signal line can be suppressed, noise due to electromagnetic interference can be reduced.

  Furthermore, since the through conductor on one side of the differential signal line is located between the through conductors on the other side in the direction perpendicular to the line direction in the upper surface of the dielectric substrate, the through conductor and the signal The location where the characteristic impedance is reduced due to the unnecessary capacitance component between the lines can be placed at different positions between the signal lines forming the differential signal line, thus avoiding overlapping of the locations where the characteristic impedance is reduced As a result, the characteristic signal impedance can be prevented from greatly decreasing as a differential signal line.

  According to the high frequency wiring board of the present invention, preferably, the through conductor on one side of the differential signal line is formed between the through conductors on the other side in the direction orthogonal to the line direction in the upper surface of the dielectric substrate. Because it is located in the middle, the characteristic impedance drop due to the unnecessary capacitance component between the through conductor and the signal line is evenly distributed between the signal lines that make up the differential signal line. Since it is possible to avoid overlapping of places where the characteristic impedance is reduced, it is possible to prevent a large reduction in characteristic impedance as a differential signal line and to uniformly control the characteristic impedance of the differential signal line It becomes.

  In addition, according to the high-frequency wiring board of the present invention, it is possible to suppress coupling of an electric field generated between a differential signal line and another adjacent signal line, and to reduce noise due to electromagnetic interference. Therefore, by forming a plurality of differential signal lines in parallel, it is possible to design with the most efficient wiring density, and to cope with the increase in the number of input / output terminals of communication devices such as MUX, DEMUX, NPU, etc. It is.

  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 the high-frequency substrate of 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 through conductor 7 on one side of the differential signal line 8 is not more than a quarter of the wavelength, and the through conductors 7 on the other side in the direction orthogonal to the line direction in the upper surface of the dielectric substrate 2 Is located. That is, the high-frequency substrate 1 of the present invention basically forms a coplanar line with the differential signal line 8 and the same-surface ground conductor layer 5 and the lower surface side conductor layer 6.

  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, the high frequency substrate 1 of the present invention is such that the through conductor 7 on one side of the differential signal line 8 is between the through conductors 7 on the other side in the direction perpendicular to the line direction in the upper surface of the dielectric substrate 2. Therefore, it is possible to avoid overlapping of a portion where the characteristic impedance is reduced due to an unnecessary capacitance component between the through conductor 7 and the first signal line 3 and the second signal line 4, 8 minutes of the wavelength of the high-frequency signal transmitted through the differential signal line 8 at the point where the characteristic impedance is reduced between the first signal line 3 and the second signal line 4 forming a pair forming the differential signal line 8 Can be uniformly distributed to 1 or less. Therefore, since the interval between the discontinuous portions of the characteristic impedance is sufficiently short with respect to the high-frequency signal transmitted through the differential signal line 8, it can be regarded as a transmission line having a uniform characteristic impedance. As a result, there is little deterioration in the transmission performance of the high frequency signal due to the mismatch of characteristic impedance, and good high frequency characteristics can be obtained.

  Further, the distance between the first signal line 3 and the second signal line 4 should be less than or equal to ¼ of the wavelength λ of the high-frequency signal. The signal line 4 is electromagnetically coupled 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

  Further, in the high-frequency substrate 1 of the present invention, the pseudo conductor walls are formed on both sides of the differential signal line 8 by the through conductors 7 formed on both sides of the differential signal line 8. Coupling of the electric field generated between the line 8 and another adjacent signal line can be suppressed, and noise due to electromagnetic interference can be reduced. Therefore, by forming a plurality of differential signal lines in parallel Therefore, it is possible to design the wiring density most efficiently, and to cope with the increase in the number of input / output terminals of communication devices such as MUX, DEMUX, NPU and the like.

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), a resin material such as glass epoxy resin, polyphenylene ether resin, liquid crystal polyester, and polyimide 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 Ni plating layer and Au plating layer deposited thereon, with Ni plating layer and Au plating layer deposited on W metallized layer, Cr-Cu alloy layer, Ni plating layer on 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 lower surface conductor layer 6 is 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 lower conductor layer 6 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.

(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 the high frequency wiring board of (a), (c) is It is sectional drawing in the BB 'line | wire of the high frequency wiring board of (a).

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. The through conductor on one side of the differential signal line is on the other side in a direction perpendicular to the line direction in the upper surface of the dielectric substrate. Between the through conductors High frequency wiring board, characterized by being located. The through conductor on one side of the differential signal line is located in the middle between the through conductors on the other side in a direction orthogonal to the line direction in the upper surface of the dielectric substrate. The high-frequency wiring board according to claim 1, wherein: 3. The high-frequency wiring board according to claim 1, wherein a plurality of differential signal lines are formed in parallel.

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