JP2009004809A - Wiring substrate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wiring substrate in which high-frequency signal reflection loss caused by discontinuity of a transmission line in a connection portion between a differential line and a differential through-conductor can be made very small. <P>SOLUTION: The differential line 8 of the wiring substrate 1 has a pair of connection lines 12 to connect a pair of line conductors 8a, 8b and a pair of signal through-conductors 9a, 9b respectively, and the pair of the connection lines 12 are at an angle more than 90° with the line conductor respectively in a plane view, and at least one of a pair of ground conductor layers includes an opening which has a circular surrounding portion enclosing the pair of the signal through-conductors 9a, 9b inside in a plane view, and the differential lines 8 are formed in such a manner that the length from the circular surrounding to the connection portion with the signal through-conductors 9a, 9b is the minimum in a plane view. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a wiring board having a differential transmission line suitable for mounting electronic components such as semiconductor elements and optical semiconductor elements that operate at high speed.

  Conventionally, in a wiring board for mounting electronic components such as semiconductor elements and optical semiconductor elements that operate at high speed, as shown in FIG. 4 which is a cross-sectional view of an example of a conventional wiring board, high-speed high-frequency signals are accurately transmitted. In order to propagate efficiently, a differential through conductor 49 is used to connect the differential line 48 and the external input / output electrode 411. The structure of the differential line 48 is such that the material of the insulating layers 42a to 42f of the insulating substrate 42 and the cross-sectional structure of the insulating layers 42a to 42f, that is, the characteristic impedance determined by the pair of signal lines is a desired value. It is determined by controlling the width and thickness of the wiring conductor 43, the distance between the wiring conductor 43 and the ground layer or the ground conductor, and the like.

  Further, as shown in FIG. 5 which is an enlarged plan view of the main part around the connection portion between the differential line and the differential through conductor formed on the wiring board of FIG. 4, the differential through conductor connected to the differential line 48. 49, the material of the insulating layers 42a to 42f of the wiring board 42 and the diameters of the differential through conductor 49 and the ground conductor 410 so that the characteristic impedance determined by the pair of signal through conductors 49a and 49b has a desired value. Or by changing their relative positions to each other.

  Further, since the distance between the pair of line conductors 48a and 48b of the differential line 48 is smaller than the distance between the pair of signal through conductors 49a and 49b, the line conductor 48a (48b) of the differential line 48 and the connection line portion 512 are connected. The formed angle 513 is 90 °, and the line conductors 48 a and 48 b are connected to the signal through conductors 49 a and 49 b through the connection line portion 512.

In FIG. 4, 41 is a wiring board, 43 is a signal wiring group, 44 (44a, 44b, 44c) is a grounding conductor layer, 45 is a semiconductor element, 46 is a conductor bump, 47 is an electrode pad, and 410 is a grounding through conductor. It is.
JP 2001-53397 A JP 2000-138433 A

  However, as the operating speed of the semiconductor element 45 mounted on the conventional wiring board 41 is increased to several tens GHz, the line conductors 48 and 48b are connected to the signal conductors 48 and 48b at the connection portion between the differential line 48 and the differential through conductor 49. Since the through conductors 49a and 49b are connected via the connection line portion 512 having an angle 513 formed by the line conductor 48a (48b) of 90 °, the line conductors 48 and 48b and the connection line portion 512 are connected to each other. A sudden change in direction due to the bent portion causes discontinuity of the transmission line, and high-frequency signals are reflected at the bent portion. As a result, there is a problem in that the high frequency signal reflection loss is increased at the connecting portion between the differential line 48 and the differential through conductor 49, the transmission performance of the high frequency signal is deteriorated, and the operability of the semiconductor element 45 is impaired. Had.

  The present invention has been completed in view of the above problems, and an object of the present invention is to provide a connection portion between a differential line and a differential through conductor in a wiring board having a differential line and a differential through conductor connected thereto. Therefore, it is possible to greatly suppress the reflection loss of the high-frequency signal in the semiconductor device, and as a result, to improve the operability of the semiconductor element.

  The wiring board of the present invention is formed on the insulating substrate, a differential line having a pair of line conductors formed in parallel to the insulating substrate, and the insulating substrate, and electrically connected to the pair of line conductors. A differential through conductor having a pair of connected signal through conductors, wherein the gap between the pair of signal through conductors is larger than the gap between the pair of line conductors, and the differential line in the insulating substrate. A pair of ground conductor layers disposed on the upper and lower sides of the differential line, and the differential line is connected to the pair of line conductors and the pair of signal through conductors. Each of the pair of connection line portions has an angle of more than 90 degrees with the line conductor, and at least one of the pair of ground conductor layers has a plan view. An annular outer periphery that surrounds the pair of signal through conductors on the inside. The differential line is formed so that the length from the annular outer peripheral portion to the connection portion with the signal through conductor is minimized in plan view. .

  In the wiring board of the present invention, preferably, the length of the connection line portion is ¼ or less of the wavelength of the upper limit frequency of the use frequency band. The wiring board according to the present invention is preferably provided along the outer peripheral portion of the insulating substrate, and includes a grounding conductor portion that connects the pair of grounding conductor layers, and the grounding conductor portion includes: A part thereof is formed along a circle centered on the signal through conductor.

  The wiring board of the present invention includes an insulating substrate, a differential line having a pair of line conductors formed in parallel to the insulating substrate, and a pair of signals formed on the insulating substrate and electrically connected to the pair of line conductors. A differential through conductor having a through conductor, wherein the distance between the pair of signal through conductors is larger than the distance between the pair of line conductors, and arranged above and below the differential line on the insulating substrate and spaced apart from the differential line. The differential line has a pair of connection line portions that connect the pair of line conductors and the pair of signal through conductors, and the pair of connection line portions are viewed in plan view. Each of the pair of ground conductor layers includes an opening having an annular outer peripheral portion that surrounds the pair of signal penetration conductors when viewed in a plan view. The differential line has a signal penetration from the annular outer periphery in plan view. Since the length to the connection with the conductor is minimized, the discontinuity of the transmission line at the connection between the connection line of the differential line and the signal through conductor of the differential through conductor is reduced. Since it can be made small, it is possible to suppress the reflection loss of the high-frequency signal at the connection portion between the differential line and the differential through conductor.

  As described above, according to the wiring board of the present invention, the reflection loss of the high-frequency signal at the connection portion between the differential line and the differential through conductor can be extremely reduced, so that the semiconductor element mounted on the wiring board of the present invention The operability in the high frequency region can be made very good.

  The wiring board of the present invention will be described in detail below. FIG. 1 is a cross-sectional view showing an example of an embodiment of a wiring board according to the present invention, and FIG. 2 is an enlarged plan view of a main part of the periphery of a differential through conductor in the wiring board of FIG.

  In wiring substrate 1 according to the present embodiment, insulating layers 2a to 2f constituting insulating substrate 2 are basically formed of an insulating material having the same relative dielectric constant. A signal wiring group 3 is formed on the insulating layer 2c, and ground conductor layers 4a and 4b having large areas are formed on the insulating layers 2b and 2d so as to face the signal wiring group 3. Each signal wiring has a stripline structure. The ground conductor layers 4a and 4b may be interchanged depending on the specifications of the wiring board 1.

  Further, by appropriately setting the wiring width of each signal wiring of the signal wiring group 3 and the thickness of the insulating layers 2b and 2c interposed between the signal wiring group 3 and the ground conductor layers 4a and 4b, Since the characteristic impedance can be set to an arbitrary value, the signal wiring group 3 having good transmission characteristics can be formed. The characteristic impedance of the signal wiring group 3 is generally set to 50Ω. The plurality of signal wirings included in the signal wiring group 3 may transmit different electrical signals.

  In the example of FIG. 1, a semiconductor integrated circuit element such as an IC or LSI that operates at high speed or a semiconductor element 5 such as an optical semiconductor element such as a semiconductor laser (LD) or photodiode (PD) is mounted on the upper surface of the wiring substrate 1. And electrically connected to the differential line 8 via a conductor bump 6 made of solder such as tin-lead (Sn—Pb) alloy or gold (Au) and an electrode pad 7 for connecting the semiconductor element 5. ing. Further, on the lower surface of the wiring substrate 1, external connection electrodes 11 for inputting / outputting signals and supplying power to the semiconductor element 5 are formed.

  The differential line 8 is composed of a pair of signal lines having a strip structure formed between the ground conductor layers 4a and 4b on the upper surface of the insulating layer 2c. It is electrically connected to the external connection electrode 11 through the conductor 9, and from the differential through conductor 9, the electrode pad 7, solder such as tin-lead (Sn—Pb) alloy, gold (Au), or the like. The conductor bump 6 is electrically connected to the electrode of the semiconductor element 5.

  The differential through conductor 9 includes a pair of signal through conductors 9a and 9b formed in parallel with each other, and a ground through conductor 10 is formed around the signal through conductors 9a and 9b. The other end is electrically connected to the external connection electrode 11.

  The connection line portion 12 according to the present embodiment will be described in detail with reference to FIG. The signal through conductors 9a and 9b of the differential through conductor 9 and the line conductors 8a and 8b of the differential line 8 are connected via a connection line portion 12 where an angle 13 formed by the line conductors 8a and 8b exceeds 90 °. Since it is connected, the discontinuity of the transmission line at the connection portion between the connection line portion 12 of the differential line 8 and the signal through conductors 9a and 9b of the differential through conductor 9 can be reduced. It becomes possible to suppress the reflection loss of the high-frequency signal at the connection portion with the moving through conductor 9.

  In the present invention, preferably, the length of the connection line portion 12 is equal to or less than ¼ of the wavelength of the upper limit frequency of the use frequency band. The influence of discontinuity at the connection portion between the through conductor 9 and the signal through conductors 9a and 9b can be further reduced, and the reflection loss of the high frequency signal can be further suppressed.

  Next, the differential line 8 according to the present invention will be described with reference to FIG. FIG. 3 is an enlarged cross-sectional view of the main part showing the peripheral part of the differential line 8 in an example of the embodiment of the wiring board 1 according to the present embodiment. In FIG. 3, the differential line 8 comprises a pair of line conductors 8a and 8b formed in parallel to each other. In the differential line 8, the width, interval, and thickness of the line conductors 8a and 8b and the thicknesses of the insulating layers 2b and 2c interposed between the line conductors 8a and 8b and the ground conductor layers 4a and 4b are set as appropriate. Thus, the characteristic impedance of the differential line 8 can be set to a desired value. As a result, the differential line 8 having good transmission characteristics can be formed. The characteristic impedance of the differential line 8 is generally set to 100Ω.

  The signal wiring group 3 and the differential line 8 are structured above and below the signal wiring group 3 in addition to the microstrip line structure formed by forming a power wiring layer or a ground conductor layer so as to face the signal wiring group 3. A strip line structure formed by forming a power supply wiring layer or a ground conductor layer, and a coplanar line formed by forming the same plane power supply wiring layer or the same plane ground conductor layer adjacent to each signal wiring of the signal wiring group 3 with a predetermined interval. It may be a structure.

  Moreover, a chip resistor, a thin film resistor, a coil inductor, a cross inductor, a chip capacitor, an electrolytic capacitor, or the like may be mounted on the wiring board 1 to constitute an electronic circuit module or the like.

  Further, the shape of each of the insulating layers 2a to 2f in a plan view may be a rhombus shape, a hexagonal shape, an octagonal shape, or the like in addition to a square shape or a rectangular shape.

  The wiring board 1 according to this embodiment includes an electronic component storage package such as a semiconductor element storage package, an electronic component mounting substrate, a so-called multichip module or multichip package on which a large number of semiconductor elements are mounted. Or used as a motherboard.

  In the wiring substrate 1 according to the present embodiment, the insulating layers 2a to 2f are formed by, for example, a ceramic green sheet lamination method. In this case, the insulating layers 2a to 2f are made of an inorganic insulating material such as an aluminum oxide sintered body, an aluminum nitride sintered body, a silicon carbide sintered body, a silicon nitride sintered body, a mullite sintered body, or a glass ceramic. Formed using materials. The insulating layers 2a to 2f are formed by bonding an organic insulating material such as polyimide, epoxy resin, fluororesin, polynorbornene or benzocyclobutene, or inorganic insulating powder such as ceramic powder with a thermosetting resin such as epoxy resin. It is formed using an electrically insulating material such as a composite insulating material.

  These insulating layers 2a to 2f are manufactured as follows. When the insulating layers 2a to 2f are made of, for example, an aluminum oxide sintered body, first, an appropriate organic binder or solvent is added to and mixed with raw material powders such as aluminum oxide, silicon oxide, calcium oxide or magnesium oxide to form a slurry. None, by adopting a doctor blade method or the like to form a sheet, a ceramic green sheet is obtained. Then, the signal paste group 3 and the metal paste which becomes each conductor layer are printed and applied in a predetermined pattern on the ceramic green sheet, and these are laminated up and down, and finally the laminated body is heated to a temperature of about 1600 ° C. in a reducing atmosphere. It is manufactured by firing at

  When the insulating layers 2a to 2f are made of an epoxy resin, first, a glass made by impregnating an epoxy resin into a thermosetting epoxy resin mixed with ceramics made of an aluminum oxide sintered body or a cloth woven with glass fibers. An organic resin precursor is deposited on the upper surface of an insulating layer made of an epoxy resin or the like by a spin coating method or a curtain coating method, and the insulating layer is formed by heat-curing the organic resin precursor. This insulating layer and a thin film wiring conductor layer formed by adopting a copper layer by employing a thin film forming technique such as an electroless plating method or a vapor deposition method and a photolithography technique are alternately laminated, and a temperature of about 170 ° C. It is manufactured by heating and curing.

  The thicknesses of these insulating layers 2a to 2f are set so as to satisfy the conditions such as mechanical strength and electrical characteristics corresponding to the required specifications according to the characteristics of the materials used.

  The signal wiring group 3, the differential line 8, and the ground conductor layer 4 are made of, for example, tungsten (W), molybdenum (Mo), molybdenum-manganese (Mo-Mn), copper (Cu), silver (Ag), or silver- Metal powder metallization such as palladium (Ag-Pd), or copper (Cu), silver (Ag), nickel (Ni), chromium (Cr), titanium (Ti), gold (Au) or niobium (Nb) and their What is necessary is just to form by the thin film etc. of metal materials, such as an alloy.

  Specifically, when the signal wiring group 3 and the power supply wiring layer 4 are formed by metal powder metallization of W, a metal paste obtained by adding and mixing an appropriate organic binder or solvent to the W powder is used for the insulating layers 2a to 2f. It can be formed by printing and applying a predetermined pattern on the ceramic green sheet to be fired together with a laminate of ceramic green sheets.

  Further, when the signal wiring group 3 and the power supply wiring layer 4 are formed of a thin film of a metal material, a metal film is formed by, for example, a sputtering method, a vacuum evaporation method or a plating method, and then formed into a predetermined wiring pattern by a photolithography method. be able to.

  Such a wiring board 1 has a wiring width and a wiring thickness of each signal wiring of the signal wiring group 3 and the differential line 8 according to the relative dielectric constant of the insulating layers 2a to 2f on which the signal wiring group 3 is disposed. By setting the wiring interval to a desired value, the characteristic impedance value of each signal wiring of the signal wiring group 3 and the characteristic impedance value of the differential line 8 can be set to desired values.

  Note that the present invention is not limited to the above-described embodiments, and various modifications may be made without departing from the scope of the present invention. For example, the differential line 8 to which the differential through conductor 9 is connected may be formed on the surface layer of the wiring board 1. Further, the secondary mounting portion to which the differential through conductor 9 is electrically connected may be a connector or a wire bonding pad. Further, the differential through conductor 9 may be used to connect the differential lines 8 formed on different insulating layers on the wiring board 1.

  The wiring board 1 having the configuration shown in FIG. 1 according to this example was manufactured as follows. The insulating substrate 2 was produced by laminating and forming the insulating layers 2a to 2f each made of an aluminum oxide sintered body having a thickness of 0.2 mm by the ceramic green sheet laminating method described above. At this time, the signal wiring group 3, the differential line 8, the ground conductor layer 4, the differential through conductor 9, and the ground through conductor 10 were formed of the above-described metal powder metallization of W.

  In this case, as shown in FIG. 2, the wiring width of each of the line conductors 8a and 8b is 50 μm and the line interval between the line conductors 8a and 8b is 100 μm on the insulating substrate 2d having a relative dielectric constant of 5.2. A differential line 8 was formed. Further, each diameter is 75 μm and the distance between each other is 0 so as to concentrically surround the differential penetration conductor 9 composed of a pair of signal penetration conductors 9 a and 9 b each having a diameter of 75 μm and a distance of 0.31 mm. 11 grounding through conductors 10 of 31 mm were formed.

  Furthermore, the angle between the signal through conductor 9a of the differential through conductor 9 and the line conductor 8a of the differential line 8 and the signal through conductor 9b and the line conductor 8b from the line conductors 8a and 8b is 158.5 °, respectively. The length is 0.215 mm (a length equal to or less than ¼ (0.82 mm) of the wavelength of a high-frequency signal of 40 GHz).

  When the high-frequency signal of 40 GHz is input to the signal through conductors 8a and 8b with a phase difference of 180 degrees with respect to the differential line 8 having the above configuration, the connection line portion 12 of the differential line 8 and the signal through conductor 9a of the differential through conductor 9 are obtained. , 9b, the discontinuity of the transmission line can be reduced, and the reflection loss of the high frequency signal can be suppressed. That is, the reflection level of the high-frequency signal at the connection portion between the differential line 8 and the differential through conductor 9 is about −33.5 dB, which is a very small value.

  Further, as Comparative Example 1, the signal through conductors 9a and 9b of the differential through conductor 9 and the line conductors 8a and 8b of the differential line 8 are connected line portions having an angle of 90 ° with the line conductors 8a and 8b. In the wiring board formed so as to be connected through the high frequency signal, the reflection level of the high frequency signal at the connection portion between the differential through conductor 9 and the differential line 8 is as high as about −20.2 dB.

It is sectional drawing which shows an example of embodiment of the wiring board of this invention. It is a principal part enlarged plan view which shows an example of embodiment of the wiring board of this invention. It is a partial expanded sectional view which shows an example of embodiment of the wiring board of this invention. It is sectional drawing which shows an example of the conventional wiring board. It is a principal part enlarged plan view which shows an example of the conventional wiring board.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Wiring board 2 ... Insulating board 2a-2f ... Insulating layer 3 ... Signal wiring group 4 ... Grounding conductor layer 5 ... Semiconductor element 6 ... Conductor bump 7 ... Electrode pads 8... Differential lines 8 a and 8 b... Line conductor 9. Differential through conductors 9 a and 9 b... Signal through conductor 10. ..An angle formed by the differential line and the connecting line part

Claims (3)

An insulating substrate;
A differential line having a pair of line conductors formed in parallel to the insulating substrate;
A differential having a pair of signal through conductors formed on the insulating substrate and electrically connected to the pair of line conductors, wherein a distance between the pair of signal through conductors is larger than a distance between the pair of line conductors. A through conductor,
A pair of ground conductor layers disposed above and below the differential line in the insulating substrate and spaced apart from the differential line;
The differential line has a pair of connection line portions that connect the pair of line conductors and the pair of signal penetration conductors, and the pair of connection line portions are each in plan view, Make an angle of over 90 degrees,
At least one of the pair of ground conductor layers includes an opening having an annular outer peripheral portion that surrounds the pair of signal penetration conductors in a plan view,
The differential line is a wiring board formed to have a minimum length from the annular outer peripheral portion to the connection portion with the signal through conductor in plan view.   The wiring board according to claim 1, wherein the connection line portion has a length that is ¼ or less of a wavelength of an upper limit frequency of a use frequency band. Provided along the outer peripheral portion on the insulating substrate, and having a grounding conductor portion for connecting the pair of ground conductor layers,
The wiring substrate according to claim 1, wherein a part of the grounding conductor portion is formed along a circle centered on the signal through conductor.

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