JP2006093325A - Wiring board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To largely suppress reflection loss of a high frequency signal in a connection part of a differential line and a differential through conductor, and to make operability of a semiconductor element to be sufficient. <P>SOLUTION: A wiring board 1 is provided with the differential line 8 formed of a pair of signal lines 8a and 8b which are formed on the main face or the inner part of an insulating substrate 2 and are mutually parallel, an identical face ground conductor 4b formed to surround the differential line 8 at a prescribed interval, land conductors 13 arranged at one end of each signal line 8a and 8b, and through conductors 9a and 9b where one end is electrically connected to the land conductors 13. In the differential line 8, one end of a land conductor 13-side is set to be a developing part 14 where an interval between a pair of signal lines 8a and 8b gradually spreads, and line width of the developing part 14 of the signal lines 8a and 8b is smaller than that of a part except for the developing part 14. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

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

  Conventionally, in a wiring board for mounting electronic components such as semiconductor elements such as IC and LSI that operate at high speed and optical semiconductor elements, as shown in FIG. 4 which is a cross-sectional view of an example of a conventional wiring board, high speed The differential line 48 is used to accurately and efficiently propagate the high frequency signal. The differential line 48 is electrically connected to the external connection electrode 411 through the differential through conductor 49 in order to input / output a high frequency signal to / from the outside. The pads 47 and the conductor bumps 46 are electrically connected to the electrodes of the semiconductor element 45.

  As shown in the partial enlarged cross-sectional view of the wiring substrate 41, the differential line 48 has insulating layers 42a to 42b on the insulating substrate 42 so that the characteristic impedance determined by the pair of signal lines 48a and 48b becomes a desired value. 42f, the cross-sectional structure of the insulating layers 42a to 42f, that is, the widths, thicknesses and intervals of the signal lines 48a and 48b, the distances between the signal lines 48a and 48b and the inner-layer ground conductors 42a to 42c, and the like. .

  As shown in the partial enlarged plan view 6 of the wiring board 41, the differential through conductor 49 has an insulating layer 42a of the wiring board 42 so that the characteristic impedance determined by the pair of through conductors 49a and 49b becomes a desired value. It is determined by changing the diameter of the material of ~ 42f, the differential through conductor 49 and the ground through conductor 410, and further changing their relative positions. Further, an inner layer ground conductor 44a having an opening 412 is formed around the differential through conductor 49 so as to surround it in a circular shape in plan view.

Further, as shown in FIG. 7 which is an enlarged plan view of the main part around the connection portion between the differential line 48 and the differential through conductor 49 formed on the wiring board 41, the differential through conductor 49 and the differential line 48 are Is connected by connecting a development portion 414 in which the distance between the signal lines 48a and 48b of the differential line 48 gradually increases via a land conductor portion 413 connected to one end thereof. In addition, an inner layer ground conductor 44b having an opening 412 formed so as to surround the connection portion in a circular shape in plan view is formed around the connection portion between the differential line 48 and the differential through conductor 49.
JP 2001-54497 A

  However, as the operation speed of the semiconductor element 45 mounted on the conventional wiring board 41 is increased to several tens GHz, the connection portion between the differential line 48 and the differential through conductor 49 is connected via the land conductor portion 413. Since the differential line 48 and the differential through conductor 49 are connected, the characteristic impedance is reduced due to the capacitance component generated between the inner layer ground conductor 44b and the land conductor portion 413, so that the reflection of the high frequency signal occurs. It was. As a result, the connection loss between the differential line 48 and the differential through conductor 49 increases the reflection loss of the high frequency signal, degrades the transmission performance of the high frequency signal, and impairs the operability of the semiconductor element 45. there were.

  The present invention has been completed in view of the above-mentioned problems, and the object thereof is to greatly suppress the reflection loss of the high-frequency signal at the connecting portion between the differential line and the differential through conductor. An object of the present invention is to provide a wiring board capable of improving the operability of a semiconductor element.

  The wiring board of the present invention includes a differential line composed of a pair of parallel signal lines formed on the main surface or inside of an insulating base, and a coplanar ground conductor formed so as to surround the differential line at a predetermined interval. And a land conductor portion provided at one end of each signal line, and a through conductor whose one end is electrically connected to the land conductor portion, and the differential line is connected to the land conductor portion side. One end of the signal line is a development part in which the distance between the pair of signal lines gradually increases, and the line width of the development part of each signal line is larger than the line width of the part other than the development part It is small.

  The wiring board according to the present invention is preferably characterized in that the line width of the developed portion of each signal line gradually decreases toward the land conductor portion.

  In the wiring board of the present invention, it is preferable that the insulating base has a main surface or an inside thereof formed with a ground conductor facing a portion other than the developed portion of the differential line and a part of the developed portion. It is characterized by.

  In the wiring board according to the present invention, the differential line has a development portion in which one end portion on the land conductor portion side is gradually widened between the pair of signal lines, and the development portion of each signal line Since the width is smaller than the line width of the part other than the development part, the inductive component of the signal line in the development part of the differential line increases, and the capacitance component generated between the land conductor part and the ground conductor on the same plane is offset. Therefore, it is possible to suppress the discontinuity of signal transmission due to the characteristic impedance drop at the connection portion between the signal line of the differential line and the differential through conductor, and to reduce the high frequency at the connection portion between the differential line and the differential through conductor. Signal reflection loss can be suppressed.

  In the wiring board of the present invention, preferably, the line width of the development part of each signal line gradually decreases toward the land conductor part, so that the line width of the development part of the differential line and the line width other than the development part are It is possible to alleviate a sudden change in characteristic impedance due to the difference in stages, and to further suppress reflection loss of high-frequency signals.

  Further, in the wiring board of the present invention, preferably, the insulating base is formed with an inner layer ground conductor facing a part other than the development part of the differential line and a part of the development part on the main surface or inside. It becomes possible to effectively shield the leakage of the high frequency signal (electromagnetic wave) from the moving line and suppress the transmission loss of the high frequency signal. As a result, 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 operability in the high-frequency region of the semiconductor element mounted on the wiring board of the present invention is very high. It can be 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 view of a main part in the periphery of a connecting portion between a differential wiring 8 and a differential through conductor 9 in the wiring board of FIG. It is a top view. 3 is an enlarged cross-sectional view of a main part of the differential wiring 8 in the wiring board of FIG.

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

  Further, by 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 inner ground conductor layers 4a and 4c, the signal wiring group 3 Therefore, it is possible to form the signal wiring group 3 having good transmission characteristics for high-frequency signals. 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, a semiconductor element 5 such as an optical semiconductor element such as a semiconductor laser (LD), a photodiode (PD), or an electronic component is formed on the upper surface of the wiring substrate 1. Is mounted on the differential line 8 via the electrode pads 7 for connecting the semiconductor bumps 6 and the conductor bumps 6 made of solder such as tin-lead (Sn—Pb) alloy solder or gold (Au). Connected. On the lower surface of the wiring substrate 1, external connection electrodes 11 for inputting / outputting signals to the semiconductor element 5 and supplying power are formed.

  The differential line 8 is composed of a pair of striped signal lines formed between the inner ground conductor layers 4a and 4c on the upper surface of the insulating layer 2c. It is electrically connected to the external connection electrode 11 through the through conductor 9, and through the differential through conductor 9, the electrode pad 7, and a conductor bump 6 made of solder such as tin-lead alloy solder or gold. Are electrically connected to the electrodes of the semiconductor element 5.

  Further, the signal wiring group 3 and the differential line 8 have a structure in addition to the microstrip line structure in which a power wiring layer or an inner ground conductor layer is formed opposite to the signal wiring group 3, A strip line structure formed by forming a power wiring layer or an inner ground conductor layer, and a single power wiring layer or a single ground conductor layer with a predetermined interval adjacent to each signal wiring of the signal wiring group 3 A coplanar line structure may be used.

  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.

  Such a wiring board 1 of the present invention 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.

  As shown in FIG. 2, the wiring board 1 of the present invention includes the through conductors 9 a and 9 b of the differential through conductor 9 and the signal lines 8 a and 8 b of the differential line 8. The development part 14 where the space | interval between them spreads gradually is electrically connected via the land conductor part 13 (13a, 13b) connected to the end. The same-surface ground conductor 4b in which an opening 12 is formed so as to surround the differential line 8 in the insulating layer 2b in which the differential line 8 is formed and to surround the connection portion with the differential through conductor 9 in a circular shape. And the inductive component of the signal lines 8a and 8b of the development part 14 increases because the signal line width of the development part 14 of the differential line 8 is smaller than the signal line width other than the development part 14. As a result, in the connection portion between the differential line 8 and the differential through conductor 9, the capacitance component generated between the land conductor portion 13 and the same plane ground conductor 4b is canceled by the increased inductive component, and the characteristic impedance is reduced. By suppressing the reflection loss of the high frequency signal at the connection portion between the differential line 8 and the differential through conductor 9 can be suppressed.

  In the present invention, preferably, the line widths of the lines 8a and 8b of the development part 14 are gradually reduced toward the land conductor part 13, so that the line widths and development parts of the signal lines 8a and 8b of the development part 14 are reduced. It is possible to alleviate a sudden change in characteristic impedance caused by stepwise differences in line widths other than 14, and to further suppress reflection loss of high-frequency signals.

  Preferably, in the present invention, the insulating base 2b is opposed to a part other than the development part 14 of the differential line 8 and a part of the development part 14 on the main surface or inside as shown in FIG. Since the inner-layer ground conductors 4a and 4c are formed so as to extend from the portion of the developing portion 14 and face a part of the developing portion 14, leakage of the high-frequency signal (electromagnetic wave) from the differential line 8 is effectively shielded. Signal transmission loss can be suppressed.

  Next, the differential line 8 according to the present invention will be described with reference to FIG. In the wiring board 1 of the present invention, 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. Made of material. The insulating layers 2a to 2f are formed by bonding a resin 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 may be made of 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, using a doctor blade method or the like to form a sheet, a ceramic green sheet is obtained. Then, a metal paste for forming the signal wiring group 3 and each conductor layer 4 is printed and applied to the ceramic green sheet in a predetermined pattern, and these ceramic green sheets are laminated on top and bottom, and finally, this laminate is about 1600 in a reducing atmosphere. It is manufactured by firing at a temperature of ° C.

  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. A 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 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 each 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 inner ground conductor layer 4 are formed of a metallized layer of W metal powder, the metal paste obtained by adding and mixing an appropriate organic binder or solvent to the W powder is insulated. It can be formed by printing and applying in a predetermined pattern on the ceramic green sheets to be the layers 2a to 2f, and firing this together with a laminate of ceramic green sheets.

  Further, when the signal wiring group 3 and each conductor layer 4 are formed of a metal thin film, for example, after forming the metal thin film by a sputtering method, a vacuum evaporation method or a plating method, it is formed into a predetermined wiring pattern by a photolithography method. Can be formed.

  Such a wiring board 1 has wiring widths and wirings of the signal wiring group 3 and the signal lines 8a and 8b of the differential line 8 according to the dielectric constant of the insulating layers 2a to 2f on which the signal wiring group 3 is disposed. By setting the thickness and the wiring interval to desired values, 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.

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

  The wiring board 1 having the configuration shown in FIG. 1 according to the present invention was manufactured as follows. The insulating substrate 2 was manufactured by laminating and forming the insulating layers 2a to 2f each made of an aluminum oxide sintered body having a thickness of 0.14 mm by the ceramic green sheet laminating method. At this time, the signal wiring group 3, the differential line 8, each conductor layer 4, the differential through conductor 9, and the ground through conductor 10 were formed of the metallized layer of the above-described Cu metal powder.

  In this case, as shown in FIG. 2, on the insulating substrate 2b having a relative dielectric constant of 5.2, each of the signal lines 8a and 8b has a line width of 65 μm and a distance between the signal lines 8a and 8b is 145 μm. Thus, the differential line 8 including the expanded portion 14 in which the interval between the signal lines 8a and 8b gradually increases in accordance with the interval of the land conductor portion 13 is formed. The signal lines 8 a and 8 b of the development portion 14 of the differential line 8 are developed at an angle of 30 degrees with the signal lines 8 a and 8 b in portions other than the development portion 14 and are connected to the land conductor portion 13. Further, in the developed part 14, the line widths of the signal lines 8a and 8b are gradually narrowed, and the line width of the part connected to one end of the land conductor part 13 is 35 μm.

  Further, each diameter is 50 μm and the distance between each other is 0 so as to surround the differential through conductor 9 composed of a pair of the through conductors 9 a and 9 b each having a diameter of 50 μm and a distance of 0.3 mm in a plan view. The six grounding through conductors 10 of 15 mm and the opening 12 that insulates the inner grounding conductor layer 4a from the differential through conductor 9 were formed. The shape of the opening 12 is an elliptical shape (oval shape) in which two circles each having a diameter of 150 μm centering on the through conductors 9a and 9b are connected by tangent lines of the circles. The differential line 8 and the differential through conductor 9 are connected via a land conductor portion 13 having a diameter of 100 μm.

  Further, in order to shield the high frequency signal, the same-surface ground conductor 4b surrounds the periphery of the differential line 8 and is formed so as to surround the connection portion between the differential line 8 and the differential through conductor 9 in a circular shape. Yes. The portion surrounding the connecting portion in a circular shape is formed in an elliptical shape (oval shape) in which two circles each having a diameter of 150 μm centering on the land conductor portions 13a and 13b are connected by tangent lines of the circles. Yes.

  When the high-frequency signal of 40 GHz is input to the through conductors 8a and 8b with a phase difference of 180 degrees with respect to the differential line 8 having the above configuration, the signal line discontinuity at the connection portion between the differential line 8 and the differential through conductor 9 is obtained. Therefore, the reflection loss of high frequency signals 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 −42 dB, which is a very small value.

  As a comparative example, in the wiring substrate 1 in which the line widths of the signal lines 8 a and 8 b are fixed to 65 μm in the development part 14 of the differential line 8, the connection part between the differential through conductor 9 and the differential line 8. The reflection level of the high-frequency signal was as high as about -26 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 of the wiring board of FIG. It is a principal part expanded sectional view of the wiring board of FIG. It is sectional drawing which shows an example of embodiment of the conventional wiring board. It is a partial expanded sectional view of an example of the conventional wiring board. It is a partial enlarged plan view of an example of a conventional wiring board. It is a principal part enlarged plan view of an example of the conventional wiring board.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Wiring board 2 ... Insulating board 2a-2f ... Insulating layer 5 ... Semiconductor element 8 ... Differential line 8a, 8b ... A pair of signal line 9 ... Differential penetration Conductors 9a, 9b ... through conductor 12 ... opening 13 ... land conductor 14 ... deployed part

Claims (3)

A differential line composed of a pair of parallel signal lines formed on the main surface or inside of the insulating base, a coplanar ground conductor formed so as to surround the differential line at a predetermined interval, and each of the signal lines A land conductor portion provided at one end; and a through conductor having one end electrically connected to the land conductor portion, and the differential line has one end portion on the land conductor portion side of the pair of land conductor portions. The wiring is characterized in that the interval between the signal lines is gradually expanded, and the line width of the expansion portion of each signal line is smaller than the line width of the portion other than the expansion portion. substrate. The wiring board according to claim 1, wherein a line width of the development portion of each signal line gradually decreases toward the land conductor portion. The inner surface ground conductor which opposes the site | part other than the said expansion | deployment part of the said differential line and a part of said expansion | deployment part is formed in the said insulation base | substrate or the inside, The Claim 1 or Claim characterized by the above-mentioned. 2. The wiring board according to 2.

Images