JP2005158967A - Wiring board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wiring board wherein no resonance occurs in a dummy conductor pattern arranged adjacent to a wiring conductor for high-frequency signal transmission, a high-frequency signal is appropriately transmitted to the wiring conductor for high-frequency signal transmission, and mounted electronic components can normally be operated. <P>SOLUTION: A dummy conductor pattern 9 that is arranged adjacent to a wiring conductor 4ap for high-frequency signal transmission is made by forming a plurality of conductor pieces 9a whose length is less than one fourth of a wavelength of a signal for transmitting the wiring conductor 4ap for high-frequency signal transmission, along the wiring conductor 4ap. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a wiring board for mounting electronic components such as semiconductor elements.

  In general, along with the demand for downsizing and thinning of electronic devices such as mobile communication devices, wiring boards for mounting electronic components such as semiconductor elements used in such electronic devices are also small. There is a demand for reduction in size, thickness, and number of terminals. As a wiring board for realizing such miniaturization, thinning, and multi-terminal, for ball grid array packages (BGA) and chip scales that can be surface-mounted on the external electric circuit board via solder bumps. A wiring board for a package (CSP) has been put into practical use.

  Such wiring substrates for ball grid array packages and chip scale packages are provided with electronic component connection pads on the upper surface of an insulating substrate in which a plurality of insulating layers are stacked, to which the electrodes of the electronic components are connected via solder. In addition, an external connection pad connected to the wiring conductor of the external electric circuit board via solder is provided on the lower surface of the insulating substrate. A wiring conductor for electrically connecting the electronic component connecting pad and the external connecting pad extends vertically through the insulating layer of the insulating substrate and extends horizontally between the insulating layers. Has been.

  And according to such a wiring board, it becomes an electronic device by mounting an electronic component on an insulating substrate so that its electrode is connected to an electronic component connecting pad via solder. The external connection pads are connected to the wiring conductors of the external electric circuit board via solder to be mounted on the external electric circuit board and the electronic components to be mounted are electrically connected to the external electric circuit; Become.

  Wiring conductors in such a wiring board are functionalized into wiring conductors for signals, grounds, and power supplies depending on applications.

  Among them, the signal wiring conductor functions as a conductive path for propagating an electric signal between an electronic component such as a semiconductor element and an external electric circuit board, and is directed from the central portion of the insulating substrate to the outer peripheral portion between the insulating layers. And having a plurality of thin strip-like conductor patterns extending so as to increase the distance between each other, the upper and lower conductor patterns are connected to each other by the conductor pillars penetrating the insulating layer, and further, the conductor pillars penetrating the insulating layer It is connected to a signal electronic component connection pad and an external connection pad.

  In addition, the wiring conductor for grounding and the wiring conductor for power supply have a function as a supply path for supplying a ground potential and a power supply potential to the electronic components mounted on the wiring board, respectively. It has an electromagnetic shielding function and a characteristic impedance adjustment function, and has a conductor pattern with a wide area facing the signal conductor pattern between the insulating layers, and a conductor pillar penetrating the insulating layer for grounding and power supply respectively. It is connected to the electronic component connecting pad and the external connecting pad.

However, in such a wiring board, the signal wiring conductor has a plurality of thin strip-like conductor patterns extending between the insulating layers so that the distance from each other increases from the central part to the outer peripheral part of the insulating board. There is a large difference in the proportion of the conductor pattern between the central portion and the outer peripheral portion of the insulating substrate, and thus the insulating substrate is likely to warp. Therefore, in Patent Document 1, by arranging a dummy conductor pattern that is electrically independent between signal conductor patterns, the ratio of the conductor pattern in the central portion and the outer peripheral portion of the insulating substrate is made uniform to warp the substrate. A wiring board designed to prevent this is disclosed.
JP-A-11-135676

  However, when a dummy conductor pattern electrically independent of the signal wiring conductor is disposed between the signal conductor patterns, if a high-frequency signal having a frequency exceeding 10 GHz is propagated to the signal wiring conductor, The resonance corresponding to the signal propagating through the signal wiring conductor occurs in the dummy conductor pattern, and the normal propagation of the signal propagating through the signal wiring conductor is hindered due to the resonance, and is mounted on the wiring board. There has been a problem that electronic components such as semiconductor elements cannot be operated normally.

  The present invention has been completed in view of such conventional problems, and its purpose is to provide a signal wiring conductor even if the frequency of the signal propagating through the signal wiring conductor is higher than 10 GHz. A wiring board that does not resonate in the dummy conductor pattern placed adjacent to it, and allows high-frequency signals to propagate well to the signal wiring conductors, so that the electronic components to be mounted can be made normally. Is to provide.

  The wiring board of the present invention includes an insulating layer, a plurality of high-frequency signal transmission wiring conductors disposed on the surface of the insulating layer, the surface of the insulating layer adjacent to the wiring conductor, and the wiring In the wiring board having a dummy conductor pattern electrically independent of the conductor, the conductor pattern has a conductor piece having a length of less than a quarter of a wavelength of a signal propagating through the wiring conductor as the wiring conductor. It is characterized in that a plurality are formed along.

  According to the wiring board of the present invention, the dummy conductor pattern disposed adjacent to the wiring conductor for high-frequency signal transmission has a length less than a quarter of the wavelength of the signal propagating through the wiring conductor for high-frequency signal transmission. Since a plurality of conductor pieces are formed along the wiring conductor for high-frequency signal transmission, even when a high-frequency signal exceeding 10 GHz is propagated to the wiring conductor for high-frequency signal transmission, The dummy conductor pattern does not generate a resonance corresponding to the signal, and as a result, the high-frequency signal is satisfactorily transmitted to the wiring conductor for high-frequency signal transmission, and the mounted electronic component can be operated normally. .

  Next, the wiring board of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a cross-sectional view showing an example in which the best mode for carrying out the present invention is applied to a wiring board for mounting a semiconductor element, in which 1 is an insulating substrate, 2a, 2b, 2c is an electronic component connection pad for signal, grounding and power supply, 3a, 3b and 3c are external connection pads for signal, grounding and power supply, and 4a, 4b and 4c are for signal and grounding, respectively. Wiring conductor for power and power supply.

  In this example, the insulating substrate 1 is formed by laminating three insulating layers 1b made of thermosetting resin on the upper and lower surfaces of the insulating layer 1a made by impregnating glass fabric with thermosetting resin, The outermost insulating layer 1b is a solder resist layer. Also, signal, grounding and power supply electronic component connection pads 2a, 2b and 2c are formed on the upper surface of the insulating substrate 1, and signals, grounding and power supply are formed on the lower surface of the insulating substrate 1, respectively. External connection pads 3a, 3b, 3c are arranged in rows and columns, and corresponding electronic component connection pads 2a, 2b, 2c and external connection pads 3a, 3b are arranged from the upper surface to the lower surface of the insulating substrate 1, respectively. Wiring conductors 4a, 4b, and 4c for signal, grounding, and power supply that electrically connect 3b and 3c to each other are disposed.

  The insulating layer 1a is a member that becomes the core of the wiring board of this example, and is formed by, for example, impregnating a glass fabric in which glass fiber bundles are woven vertically and horizontally with a thermosetting resin such as an epoxy resin or a bismaleimide triazine resin, The thickness is about 0.3 to 1.5 mm, and a plurality of through holes 5 having a diameter of about 0.1 to 1 mm are provided from the upper surface to the lower surface. And on the upper and lower surfaces, there are conductor patterns constituting a part of the wiring conductors 4a, 4b, 4c, and cylindrical conductor pillars constituting a part of the wiring conductors 4a, 4b, 4c on the inner surface of each through hole 5. The conductor patterns on the upper and lower surfaces of the insulating layer 1 a are electrically connected via the conductor pillars in the through holes 5.

  Such an insulating layer 1a is manufactured by thermally curing an insulating sheet in which a glass fabric is impregnated with an uncured thermosetting resin, and then drilling the insulating sheet from the upper surface to the lower surface. The conductive patterns of the wiring conductors 4a, 4b, 4c on the upper and lower surfaces of the insulating layer 1a are made by attaching a copper foil having a thickness of about 3 to 50 μm to the entire upper and lower surfaces of the insulating sheet for the insulating layer 1a. Is formed into a predetermined pattern by etching after the sheet is cured. Further, the conductor pillars of the wiring conductors 4a, 4b, 4c on the inner surface of the through hole 5 have a thickness of 3 to 3 by electroless plating and electrolytic plating on the inner surface of the through hole 5 after the through hole 5 is provided in the insulating layer 1a. It is formed by depositing a copper plating film of about 50 μm.

  Furthermore, the insulating layer 1a is filled with a resin column 6 made of a thermosetting resin such as an epoxy resin or a bismaleimide triazine resin in the through hole 5 thereof. The resin pillar 6 is for making it possible to form each insulating layer 1b directly above and below the through-hole 5 by closing the through-hole 5, and an uncured paste-like thermosetting resin is placed in the through-hole 5 After the film is filled by screen printing and thermally cured, the upper and lower surfaces thereof are polished substantially flatly. Three insulating layers 1b are laminated on the upper and lower surfaces of the insulating layer 1a including the resin pillars 6 respectively.

  Each insulating layer 1b laminated on the upper and lower surfaces of the insulating layer 1a has a thickness of about 20 to 60 μm, and has a plurality of through holes 7 having a diameter of about 30 to 100 μm from the upper surface to the lower surface of each layer. . Each of these insulating layers 1b is for providing an insulating interval for wiring the wiring conductors 4a, 4b, 4c with high density, and on the surface of each insulating layer 1b except the outermost insulating layer 1b. A conductor pattern constituting a part of the wiring conductors 4a, 4b, 4c is deposited, and an inverted frustoconical conductor column constituting a part of the wiring conductors 4a, 4b, 4c is covered in the through hole 7. It is worn. The upper layer conductor pattern and the lower layer conductor pattern are electrically connected via the conductor pillars in the through holes 7 to enable three-dimensional high density wiring. Each of such insulating layers 1b has an insulating film made of an uncured thermosetting resin having a thickness of about 20 to 60 [mu] m attached to the upper and lower surfaces of the insulating layer 1a, thermally cured, and laser-processed through holes. 7 is drilled, and the next insulating resin layer is sequentially stacked thereon in the same manner. Note that the wiring conductors 4a, 4b, 4c deposited on the surface of each insulating layer 1b and in the through hole 7 are formed in the surface of each insulating layer 1b and in the through hole 7 every time each insulating layer 1b is formed. It is formed by depositing a copper plating film having a thickness of about 50 μm in a predetermined pattern by a known pattern forming method such as a semi-additive method or a subtractive method.

  Also, the electronic component connection pads 2a, 2b, 2c formed on the upper surface of the insulating substrate 1 and the external connection pads 3a, 3b, 3c formed on the lower surface of the insulating substrate 1 are copper having a thickness of about 3 to 50 μm. It consists of a plating film and functions as a connection electrode for electrically connecting the electrodes of the electronic component and the wiring conductor of the external electric circuit board to the wiring conductors 4a, 4b, 4c, respectively. Solder 8a, 8b is bonded to each exposed surface, and each electrode of the electronic component is connected to the electronic component connecting pads 2a, 2b, 2c via the solder 8a, and the external connecting pad 3a, A wiring conductor of an external electric circuit board is connected to 3b and 3c via solder 8b. Such electronic component connection pads 2a, 2b, 2c and external connection pads 3a, 3b, 3c are coated with a copper plating film in a predetermined pattern on the surface of the insulating layer 2b by a known semi-additive method or subtractive method. The solder 8a and 8b are joined by applying a solder paste to the surface and reflowing it.

  The signal electronic component connection pad 2a has a circular shape with a diameter of about 50 to 100 μm, and the electronic component connection pads 2b and 2c for grounding and power supply have a circular shape with a diameter of about 50 to 100 μm or a continuous wide area. It is an area pattern. The signal external connection pad 3a has a circular shape with a diameter of about 200 to 500 μm, and the ground and power supply external connection pads 3b and 3c have a circular shape with a diameter of about 200 to 500 μm or a continuous large area. It is a pattern.

  These electronic component connection pads 2a, 2b and 2c are connected to the external connection pads 3a, 3b and 3c so as to be connected from the upper surface to the lower surface of the insulating substrate 1 for signal, grounding and power supply. Each wiring conductor 4a, 4b, 4c functions as a conductive path for connecting each electrode of the electronic component to the external electric circuit board. If the wiring conductor 4a is for signal, FIG. As shown, it has a plurality of thin strip-like wiring conductors 4ap for high-frequency signal transmission that extend between the insulating layers 1b from the central portion of the insulating substrate 1 toward the outer peripheral portion so that the distance between them increases. The grounding and power supply wiring conductors 4b and 4c include a wide-area conductor pattern facing the wiring conductor 4ap for high-frequency signal transmission. The signal wiring conductor 4a functions as a conductor for inputting and outputting signals to and from the electronic component, and the grounding and power wiring conductors 4b and 4c supply the ground potential and the power supply potential to the electronic component. And also functions as a shield that electromagnetically shields the signal wiring conductor 4a. For example, when the signal conductor pattern and the ground or power supply conductor pattern face each other with the insulating layer 1b interposed therebetween, a predetermined characteristic impedance is given to the signal wiring conductor 4a.

  Furthermore, in the wiring board of this example, as shown in FIG. 2, a dummy conductor pattern 9 electrically independent from the wiring conductor 4ap for high frequency signal transmission is provided between the wiring conductors 4ap for high frequency signal transmission. It is arranged. The dummy conductor pattern 9 is formed of a conductor made of the same material as the high-frequency signal transmission wiring conductor 4ap, and has a length less than a quarter of the wavelength of the high-frequency signal propagating through the high-frequency signal transmission wiring conductor 4ap. A plurality of conductor pieces 9a are formed along the wiring conductor 4ap for high-frequency signal transmission. Such a dummy conductor pattern 9 makes the proportion of the conductor pattern in the central portion and the outer peripheral portion of the insulating substrate 1 uniform so as to prevent the warp of the substrate, and the signal conductor pattern can be used as a semi-additive method or a subtractive method. The pattern forming method has the effect of making the etching amount of the pattern uniform and is formed simultaneously with the signal conductor pattern by a pattern forming method such as a semi-additive method or a subtractive method.

  In the present invention, the dummy conductor pattern 9 has a conductor piece 9a having a length less than a quarter of the wavelength of the signal propagating through the wiring conductor 4ap for high-frequency signal transmission along the wiring conductor 4ap for high-frequency signal transmission. It is important that this is formed. In the wiring board of the present invention, the dummy conductor pattern 9 provided adjacent to the wiring conductor 4ap for high-frequency signal transmission is less than a quarter of the wavelength of the signal propagating through the wiring conductor 4ap for high-frequency signal transmission. Since a plurality of conductor pieces 9a having a length are formed along the wiring conductor 4ap for high-frequency signal transmission, even if a high-frequency signal having a frequency of 10 GHz or more propagates to the wiring conductor 4ap for high-frequency signal transmission, Since the resonance is suppressed in the conductor piece 9a having a wavelength less than ¼ of the wavelength, the dummy conductor pattern 9 does not resonate. Therefore, a high-frequency signal of 10 GHz or more can be satisfactorily transmitted to the wiring conductor 4ap for high-frequency signal transmission, and the mounted electronic component can be made normally.

  In the dummy conductor pattern 9, when the interval between the conductor pieces 9a is less than 30 μm, there is a risk that the electrical insulation between the conductor pieces 9a decreases and resonance occurs in the conductor pattern 9. growing. Therefore, the dummy conductor pattern 9 preferably has an interval between the conductor pieces 9a of 30 μm or more.

  Further, as shown in FIG. 2, it is preferable that the spacing between the wiring conductor 4ap for high-frequency signal transmission and each conductor piece 9a adjacent to the wiring conductor 4ap be the same. If the distance between the high-frequency signal transmission wiring conductor 4ap and each conductor piece 9a adjacent to the wiring conductor 4ap is not uniform, the electromagnetic field distribution is disturbed and the transmission loss characteristic is deteriorated.

  Thus, according to the wiring board of the present invention, the electronic component is mounted on the upper surface of the insulating substrate 1 so that the electrode thereof is connected to each of the electronic component connecting pads 2a, 2b, 2c via the solder 8a. The electronic device is mounted on the external electric circuit board and mounted on the electronic device by connecting the external connection pads 3a, 3b, 3c to the wiring conductor of the external electric circuit board via the solder 8b. Each electrode of the component is electrically connected to an external electric circuit.

  It should be noted that the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the gist of the present invention. For example, in the above-described embodiment, a dummy conductor pattern is used. Each of the conductor pieces 9a constituting the conductor 9 has a trapezoidal shape, but the conductor pieces 9a may have other shapes such as a circle, a quadrangle, and a triangle.

It is sectional drawing which shows the example of the best form for implementing the wiring board of this invention. It is a principal part top view of the example of a form shown in FIG.

Explanation of symbols

1a, 1b: Insulating layer 4ap: Wiring conductor for high-frequency signal transmission 9: Dummy conductor pattern 9a: Conductor piece constituting dummy conductor pattern 9

Claims (1)

An insulating layer; a plurality of high-frequency signal transmission wiring conductors disposed on a surface of the insulating layer; and disposed on the surface of the insulating layer adjacent to the wiring conductor and electrically independent of the wiring conductor. In the wiring board having a dummy conductor pattern, the conductor pattern includes a plurality of conductor pieces having a length less than a quarter of the wavelength of a high-frequency signal propagating through the wiring conductor. A wiring board characterized by comprising:

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