JP2006093324A - Wiring board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wiring board where operability of a semiconductor element can be made sufficient by suppressing reflection loss of a high frequency signal which occurs from impedance discontinuity of a signal line in a developing part of a differential line, to be very small. <P>SOLUTION: In the wiring board, the differential line 8 formed of a pair of mutually parallel signal lines 8a and 8b is formed on an upper face of an insulating substrate 2. In the differential line 8, one end is set to be the developing part 8d where an interval between a pair of signal lines 8a and 8b gradually spreads, and thickness of the developing part 8d becomes thicker than that of a part except for the developing part 8d. <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 and optical semiconductor elements that operate at high speed, as shown in FIG. 4 which is a sectional view of a conventional example, in order to propagate high-speed signals accurately and efficiently A differential line 48 is used. As shown in FIG. 5, which is a partial sectional view of a conventional example, the differential line 48 is interposed between the signal lines 48a and 48b and the inner ground conductor layer 44a. Since the differential impedance value in the differential line 48 can be set to an arbitrary value by adjusting and setting the thickness of the insulating layer 42a to be formed, the differential line 48 having good transmission characteristics can be formed. it can. In general, the differential impedance of the differential line 48 is often set to 100Ω.

The differential line 48 is electrically connected to the semiconductor element 45 via the conductor bump 46 and the semiconductor element connection electrode 47, and electrically connected to the external input / output electrode 410 via the signal through conductor 49. Has been.
JP 2002-9511 A

  However, in the differential line 48 formed on the conventional wiring substrate 41, as shown in FIG. 6, the distance between the pair of signal lines 48a and 48b designed so that the differential impedance is about 100Ω, for example. In contrast to the constant portion 48c having a constant width, a development portion 48d is formed in which the interval between the pair of signal lines 48a and 48b gradually increases in accordance with the arrangement interval of the external input / output electrodes 410 as the secondary mounting portion. In the expanded portion 48d, the differential impedance increases from 100Ω because the line spacing of the differential line 48 changes, and impedance mismatch occurs between the constant portion 48c and the expanded portion 48d, resulting in a large reflection loss. As a result, the transmission of high-frequency signals is hindered, and the operability of the semiconductor element 45 is impaired.

  The present invention has been completed in view of the above problems, and its purpose is to suppress the reflection loss of the high-frequency signal generated in the expanded portion where the line spacing of the differential line is widened to a very small value. Accordingly, an object of the present invention is to provide a wiring board capable of improving the operability of the semiconductor element.

  The wiring board of the present invention is a wiring board in which a differential line composed of a pair of signal lines parallel to each other is formed on an upper surface of an insulating base, and the differential line has one end portion between the pair of signal lines. The width of the developed portion of the signal line is larger than the thickness of the portion other than the developed portion.

  The wiring board according to the present invention is preferably characterized in that the signal line is embedded in the insulating substrate under the development portion.

  In the wiring board of the present invention, it is preferable that the signal line has a lower thickness embedded in the insulating substrate of the development portion than an upper thickness exposed from the insulating substrate. And

  The wiring board of the present invention is preferably characterized in that a ground conductor is formed on the lower surface or inside of the insulating substrate so as to face the differential line.

  In the wiring board of the present invention, with respect to the differential lines formed on the wiring board, the thickness of each signal line is a part other than the developed part in the developed part where the distance between the signal lines of the differential line gradually increases. Therefore, in the expanded portion, the differential impedance decreases due to a decrease in the inductive component and an increase in the capacitance component of the pair of signal lines. As a result, it is possible to suppress the reflection loss of the high frequency signal due to the mismatch of the differential impedance in the development part.

  In the wiring board of the present invention, preferably, since the lower side of the development part is embedded in the insulating substrate, the embedded parts can be easily capacitively coupled through an insulator constituting the wiring board, and a pair of parts are provided in the development part. The differential impedance decreases due to an increase in the capacitance component of the signal line. As a result, it is possible to suppress the reflection loss of the high-frequency signal due to the mismatch of the differential impedance due to the change in the line spacing of the differential lines in the development part.

  Further, in the wiring board of the present invention, preferably, the signal line of the development portion is thicker on the lower side embedded in the insulating substrate than on the upper side exposed from the insulating substrate. Capacitive coupling is facilitated through an insulator forming the wiring board, the distance from the ground conductor formed on the lower surface side of the signal line is shortened, and the differential impedance is reduced by increasing the capacitance component of the pair of signal lines. Become. As a result, it is possible to suppress the reflection loss of the high-frequency signal due to the mismatch of the differential impedance due to the change in the line spacing of the differential lines in the development part.

  In the wiring board of the present invention, preferably, since the grounding conductor is formed on the lower surface or inside of the insulating board so as to face the differential line, the grounding conductor shields leakage of high-frequency signals (electromagnetic waves). Transmission loss can be suppressed.

  As a result, according to the wiring board of the present invention, the reflection loss and transmission loss of the high-frequency signal in the expanded portion where the line spacing of the differential lines is widened can be extremely reduced, so that the semiconductor element mounted on the wiring board The operability in the high frequency region can be improved.

  The wiring board of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a cross-sectional view showing an example of an embodiment of a wiring board according to the present invention, FIG. 2 is an enlarged plan view of a main part of the periphery of a differential line in the wiring board shown in FIG. 1, and FIG. It is a principal part expanded sectional view in the wiring board shown.

  In this wiring substrate 1, the insulating layers 2a to 2d constituting the 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 a large-area power wiring layer 4a and a ground wiring layer 4b are formed on the insulating layers 2b and 2d so as to face the signal wiring group 3, and the signal wiring Each signal wiring of group 3 has a stripline structure. The power supply wiring layer 4a and the ground wiring layer 4b may be interchanged and arranged 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 power wiring layer 4a or the ground wiring layer 4b, Since the characteristic impedance of the wiring group 3 can be set to an arbitrary value, the signal wiring group 3 having good transmission characteristics can be formed. In many cases, 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 this example, 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 is mounted on the upper surface of the wiring substrate 1, and solder such as tin-lead (Sn—Pb) alloy solder, It is electrically connected to the differential line 8 via a conductor bump 6 made of gold (Au) or the like and a semiconductor element connection electrode 7 for connecting the semiconductor element 5. An external input / output electrode 10 for inputting / outputting signals and supplying power to the semiconductor element 5 is formed on the lower surface of the wiring board 1 opposite to the upper surface on which the semiconductor element 5 is mounted.

  The differential line 8 is formed of a pair of microstrip signal lines formed between the power wiring layer 4a or the ground wiring layer 4b on the upper surface of the insulating layer 2a. -It is electrically connected to the electrodes of the semiconductor element 5 through conductor bumps 6 made of solder such as lead alloy solder, gold, etc., and externally input through the through conductors 9 in order to input / output signals to / from the outside. The output electrode 10 is electrically connected. A grounding through conductor 11 is formed around the signal through conductor 9 concentrically around the signal through conductor 9.

  FIG. 2 is an enlarged plan view of a main part showing a peripheral portion of the differential line 8 in an example of the embodiment of the wiring board of the present invention. In FIG. 2, the insulating layer 2 corresponds to the insulating layer 2a of FIG.

  The pair of signal lines 8 a and 8 b constituting the differential line 8 are electrically connected to the semiconductor element 5 via the conductor bump 6 and the semiconductor element connection electrode 7, and externally input via the signal through conductor 9. It is electrically connected to the output electrode 10. The differential line 8 is formed by a constant part 8c in which the distance between the pair of signal lines 8a and 8b is constant, and a development part 8d in which the distance between the pair of signal lines 8a and 8b gradually increases. The thickness of the signal lines 8a and 8b of the expanded portion 8d is larger than the thickness of the fixed portion 8c. The signal lines 8a and 8b are electrically connected to the external input / output electrode 10 through the signal through conductors 9a and 9b, respectively, at the end of the expanded portion 8d.

  Further, in FIG. 3, the signal lines 8a and 8b of the differential line 8 are embedded in the insulating layer 2a on the lower side, and are formed thicker than the upper side where the thickness of the embedded part is exposed. By adjusting and setting the thickness of the signal lines 8a and 8b and the thickness embedded in the insulating layer 2a in the expanding portion 8d as the distance between the signal lines 8a and 8b gradually increases, the differential impedance in the expanding portion 8d is set. Can be controlled. Therefore, it is possible to form the differential line 8 having good transmission characteristics for high-frequency signals.

  The signal wiring group 3 and the differential line 8 are structured in addition to the microstrip line structure having the power wiring layer 4a and the ground wiring layer 4b formed to face the signal wiring group 3, as well as the signal wiring group 3 A strip line structure having a power wiring layer 4a and a ground wiring layer 4b above and below, and a coplanar line structure in which a power wiring layer 4a and a ground wiring layer 4b are formed adjacent to each signal wiring of the signal wiring group 3. In other words, the wiring board 1 can be appropriately selected and used according to the specifications required for the wiring board 1.

  Further, an electronic circuit module or the like may be configured by mounting a chip resistor, a thin film resistor, a coil inductor, a cross inductor, a chip capacitor, an electrolytic capacitor, or the like on the wiring board 1.

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

  The wiring board 1 of the present invention is 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 a motherboard. used.

  In the wiring board 1 of the present invention, each of the insulating layers 2a to 2d is formed of, for example, a ceramic green sheet lamination method, an aluminum oxide sintered body, an aluminum nitride sintered body, a silicon carbide sintered body, or a silicon nitride sintered body. Body, mullite sintered body or glass ceramic sintered body and other inorganic insulating materials. The insulating layers 2a to 2d are made of an organic insulating material such as polyimide, epoxy resin, fluororesin, polynorbornene or benzocyclobutene, or inorganic insulating powder such as ceramic powder is thermosetting such as epoxy resin. You may consist of electrical insulation materials, such as a composite insulation material couple | bonded with resin.

  The insulating layers 2a to 2d are produced as follows. For example, in the case of an aluminum oxide sintered body, first, a suitable 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, which is then doctor blade. A ceramic green sheet is obtained by using a method or the like to form a sheet. Then, a metal paste to be used for each signal wiring group 3 and each conductor layer 4 is printed and applied in a predetermined pattern and laminated vertically, and finally the laminated body is fired at a temperature of about 1600 ° C. in a reducing atmosphere. Produced by.

  When the insulating layers 2a to 2d are made of, for example, an epoxy resin, an insulating layer made of glass epoxy resin or the like generally formed by impregnating an epoxy resin into a cloth woven with ceramics or glass fibers made of an aluminum oxide sintered body. An insulating layer made of a resin such as an epoxy resin formed by applying a resin precursor to the upper surface of the substrate by spin coating or curtain coating and thermosetting the copper, and electroless plating or copper It is manufactured by alternately laminating thin film wiring conductor layers formed by thin film formation technology such as vapor deposition and photolithography technology, and heat-curing at a temperature of about 170 ° C.

  The thicknesses of these insulating layers 2a to 2d are appropriately 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.

  In addition, as a method for obtaining the insulating layers 2a to 2d having different dielectric constants, for example, inorganic insulating materials such as aluminum oxide, aluminum nitride, silicon carbide, silicon nitride, mullite, or glass ceramics, polyimide, epoxy resin, Add and mix powder of high dielectric material such as barium titanate, strontium titanate, calcium titanate or magnesium titanate into insulating material such as fluororesin, polynorbornene or benzocyclobutene, and heat cure at appropriate temperature Thus, a desired dielectric constant can be obtained.

  At this time, the particle size of the high dielectric material added to and mixed with the inorganic insulating material or the organic insulating material is the dielectric in the insulating layers 2a to 2d caused by adding and mixing the high dielectric material to the inorganic insulating material or the organic insulating material. In order to reduce a decrease in the rate variation and a decrease in workability due to a change in the viscosity of the insulating layer, the range of 0.5 to 50 μm is preferable.

  The content of the high dielectric material added to and mixed with the inorganic insulating material or the organic insulating material is to increase the dielectric constant of the insulating layers 2a to 2d, and the inorganic insulating material, the organic insulating material, and the high dielectric material. In order to prevent a decrease in the adhesive strength, it is preferably 5 to 75% by weight.

  The signal wiring group 3, the differential line 8, the power supply wiring layer 4a and the ground wiring layer 4b are made of, for example, tungsten (W), molybdenum (Mo), molybdenum manganese (Mo—Mn), copper (Cu), silver (Ag). ) Or metal powder metallization such as silver palladium (Ag-Pd), or copper (Cu), silver (Ag), nickel (Ni), chromium (Cr), titanium (Ti), gold (Au) or niobium (Nb) Or a thin film of a metal material such as an alloy thereof.

  Specifically, when the signal wiring group 3 or the like is formed of a metal powder metallization of Cu and W, a metal paste obtained by adding and mixing an appropriate organic binder or solvent to the W powder is combined with the insulating layers 2a to 2d. It can be formed by printing and applying to a ceramic green sheet to be formed in a predetermined pattern and firing it together with a laminate of ceramic green sheets.

  Further, when the signal wiring group 3 or the like is formed of a metal thin film, it can be formed by forming a metal thin film by, for example, a sputtering method, a vacuum evaporation method or a plating method and then forming a predetermined wiring pattern by a photolithography method.

  Such a wiring board 1 has a wiring width of each 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 2d on which the signal wiring group 3 is disposed. By setting the wiring thickness and the wiring interval, the characteristic impedance value of each signal wiring of the signal wiring group 3 and the differential 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 may be formed in the inner layer of the wiring board 1, and the secondary mounting portion to which the differential line 8 is electrically connected may be a connector, a wire bonding pad, or the like. In addition, the thickness of the signal lines 8a and 8b may be gradually increased toward the end in the expanded portion 8d of the working line 8.

  The wiring board 1 of FIG. 1 of the present invention was produced as follows. The insulating substrate 2 was produced by laminating and forming the insulating layers 2a to 2d each having a thickness of 0.1 mm made of the aluminum oxide sintered body by the ceramic green sheet laminating method described above. At this time, the signal wiring group 3, the differential line 8, the power supply wiring layer 4a, the ground wiring layer 4b, the signal through conductor 9, and the ground through conductor 11 were formed of the metallized layer using Cu metal powder as described above. .

  As shown in FIG. 2, the insulating substrate 2 having a relative dielectric constant of 5.2 has a signal line width of 75 .mu.m for the signal lines 8a and 8b, a thickness of 12 .mu.m for each of the signal lines 8a and 8b in the fixed portion 8c, and a developed portion 8d. A differential line 8 having a microstrip structure in which the thickness of each signal line 8a, 8b is 30 μm and the interval between the signal lines 8a, 8b in the fixed portion 8c is 75 μm is formed.

  The signal lines 8a and 8b of the development part 8d were formed with an angle of 30 degrees with the signal lines 8a and 8b of the fixed part 8c in accordance with the arrangement interval of the external input / output electrodes 11 of 1.0 mm.

  When the high-frequency signal of 40 GHz is input to the signal lines 8a and 8b with a phase difference of 180 degrees with respect to the differential line 8 having the above-described configuration, the signal lines 8a and 8a at the connection part between the constant part 8c and the development part 8d of the differential line 8 Since the discontinuity of the differential impedance of 8b can be reduced, the reflection loss of the high frequency signal can be suppressed. That is, the reflection level of the high-frequency signal in the differential line 8 is -18 dB in the comparative example in which the thickness of the developed portion 8d is 12 μm, which is the same as the constant portion 8c, whereas it is about -23 dB in this embodiment. It was a very small value.

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 the conventional wiring board. It is a principal part expanded sectional view of the wiring board of FIG. It is a principal part enlarged plan view of the wiring board of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Wiring board 2 ... Insulating board 2a-2d ... Insulating layer 3 ... Signal wiring group 4 ... Inner layer grounding conductor layer 5 ... Semiconductor element 8 ... Differential line 8a, 8b ... Pair of signal lines 8d ... Expanding part

Claims (4)

In the wiring substrate in which a differential line composed of a pair of signal lines parallel to each other is formed on the upper surface of the insulating substrate, the differential line is developed such that one end portion of the differential line is gradually widened. And a thickness of the developed portion of the signal line is thicker than a thickness of a portion other than the developed portion. The wiring board according to claim 1, wherein a lower side of the development portion of the signal line is embedded in the insulating substrate. The wiring board according to claim 2, wherein the signal line has a lower thickness embedded in the insulating substrate of the development portion than an upper thickness exposed from the insulating substrate. The wiring board according to claim 1, wherein a ground conductor is formed on the lower surface or inside of the insulating substrate so as to face the differential line.

Images