JP2008103870A - Portable radio equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide portable radio equipment having taken measures against unwanted radiation noise. <P>SOLUTION: The portable radio equipment (mobile phone) 100 comprises a mounting board (circuit board) 10 made of a dielectric material 10a, a plurality of semiconductor chips (20, 22) mounted on the mounting board (circuit board) 10, a radio circuit unit 30 provided on the mounting board (circuit board) 10, and an antenna element 40 connected to the radio circuit unit 30. Then semiconductor chips 20 (20a, 20b, 20c) generating unwanted radiation noise among the plurality of semiconductor chips (20, 22) are disposed while enclosed with a low-dielectric-constant material 10b having a lower dielectric constant than the dielectric material 10a forming the mounting board (circuit board) 10. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a portable wireless device, and more particularly to a portable wireless device (for example, a mobile phone) in which a transmission / reception failure may occur due to unwanted radiation noise from a digital component that wraps around from an antenna.

  In recent years, electronic devices typified by digital AV devices and portable information terminals have been reduced in size and functionality. As electronic devices have become smaller and higher in performance, the mounting density of printed circuit boards constituting electronic devices has increased, and the operating frequency of ICs (semiconductor integrated circuits) mounted on printed circuit boards has become faster. As a result, electromagnetic waves radiated from the printed circuit board, that is, electromagnetic interference (EMI) such as malfunctions of electronic devices and transmission / reception failures caused by unnecessary radiation noise are increasing (for example, Patent Document 1) reference).

Specifically, with the increase in operating frequency of an IC mounted on a circuit board, unnecessary radiation noise generated from the circuit board cannot be ignored in the electromagnetic wave transmission / reception function of electronic devices. As countermeasures against unwanted radiation noise (radiation noise countermeasures), noise countermeasure parts are often mounted or shielded.
JP 2000-19204 A JP 2004-56426 A

  However, in a portable wireless device such as a mobile phone, as disclosed in Patent Document 2, since an antenna is formed near the circuit board, unnecessary radiation noise from digital components mounted on the circuit board is obtained. When the antenna goes around from the antenna, a transmission / reception failure is likely to occur. In particular, in the case of a built-in antenna, the position of the antenna and the circuit board becomes extremely close to each other, so the influence becomes large. This countermeasure against unwanted radiation noise is one of the main causes that lead to an increase in the development lead time of portable wireless devices (for example, mobile phones).

  This measure against unwanted radiation noise is handled by the design of the circuit board, but this measure is basically based on empirical rules, and in reality it is actually solved by trial and error. . However, this approach is not a fundamental solution that prevents the development lead time from being prolonged, and currently, only a countermeasure is taken by a circuit board design method without a fundamental solution.

  The present invention has been made in view of such a point, and a main object of the present invention is to provide a portable wireless device (for example, a mobile phone) having a structure in which unnecessary radiation noise is suppressed or reduced from wrapping around from an antenna. is there.

  A portable wireless device of the present invention is a portable wireless device including a plurality of semiconductor chips, and is provided on a mounting substrate made of a dielectric material, a plurality of semiconductor chips mounted on the mounting substrate, and the mounting substrate. A first semiconductor chip that generates unnecessary radiation noise among the plurality of semiconductor chips is the dielectric that constitutes the mounting substrate. Surrounded by a low dielectric constant material having a lower dielectric constant than the material.

  In a preferred embodiment, the first semiconductor chip is an LSI chip having a digital circuit portion.

  In a preferred embodiment, the first semiconductor chip is surrounded by the low dielectric constant material so that an antenna current distribution in a region where the first semiconductor chip is located is lowered.

  In a preferred embodiment, the wireless circuit unit includes a second semiconductor chip constituting a high-frequency circuit unit, and the second semiconductor chip is mounted on the mounting substrate other than a region where the low dielectric constant material is located. Is provided.

  In a preferred embodiment, the first semiconductor chip is embedded in the mounting substrate in a state covered with the low dielectric constant material.

  In a preferred embodiment, the first semiconductor chip is disposed on a layer made of the low dielectric constant material, and at least above the first semiconductor chip, the dielectric material constituting the mounting substrate It is covered with a housing made of a low dielectric constant material having a lower dielectric constant.

  In a preferred embodiment, the portable radio is a mobile phone.

  The method for manufacturing a portable wireless device of the present invention includes a step of preparing a mounting substrate composed of a plurality of dielectric materials having different dielectric constants, and a low dielectric constant having a lower dielectric constant than other portions of the mounting substrate. Mounting a semiconductor chip that generates unnecessary radiation noise in a region where the material is located.

  According to the portable wireless device of the present invention, among the plurality of semiconductor chips mounted on the mounting substrate, the first semiconductor chip that generates unnecessary radiation noise has a low dielectric constant lower than that of the dielectric material constituting the mounting substrate. Since it is surrounded by the dielectric constant material, the antenna current distribution in the region where the first semiconductor chip of the noise generation source is located can be reduced, and as a result, unwanted radiation noise can be prevented from wrapping around from the antenna. It can be mitigated.

  The inventor of the present application, for example, generates unnecessary radiation noise 1300 from a digital component (digital circuit unit) 1100 built in a cellular phone 1000 (or a portable wireless device or a portable mobile communication device) as shown in FIG. In order to suppress the transmission / reception failure caused by wrapping around, we aimed at fundamental solution rather than coping therapy approach by circuit board design change. Specifically, an attempt was made to develop a mobile phone that is resistant to noise by modifying the near-field characteristics while maintaining the original characteristics (far-field characteristics) of the antenna without deterioration. FIG. 1 also shows a wireless circuit unit (RF circuit unit) 1400 connected to an antenna 1200, a liquid crystal display unit 1500, and an image sensor (CCD camera) 1600. The image sensor 1600 is not limited to a CCD camera but may be a CMOS camera.

  Further, a transmission / reception failure caused by unnecessary radiation noise 1300 wrapping around the antenna 1200 will be briefly described with reference to FIG. FIG. 2 is a block diagram showing a basic configuration of the mobile phone 1000.

  As shown in FIG. 2, in addition to a communication function having a radio circuit unit (RF circuit unit) 1400 and a demodulation circuit 1450 (receiving circuit) connected to a high-sensitivity antenna 1200, a liquid crystal display unit 1500 (LCD panel) In addition, a display function configured by the LCD controller 1100a and a camera function configured by the imaging device (CCD) 1600 and the image signal processing circuit 1100b are mounted. Here, the LCD controller 1100a and the image signal processing circuit 1100b are formed of an LSI chip (digital component (digital circuit unit) 1100) having a digital circuit unit, and emit unnecessary radiation noise 1300 (1300a, 1300b) during operation.

  As the unnecessary radiation noise 1300 radiated from the circuit board, there is noise 1300b picked up by the antenna 1200 in addition to the noise 1300a radiated outside the mobile phone 1000. This type of noise 1300b cannot be shielded even if the casing of the mobile phone 1000 is shielded, and if it is mixed into the radio circuit unit (RF circuit unit) 1400 via the antenna 1200, it is a factor that degrades reception characteristics. Become.

  The inventor of the present application can use a high-sensitivity antenna 1200 as long as the antenna current distribution is reduced in a portion where an LSI chip (controller 1100a, image signal processing circuit 1100b) serving as a noise source is mounted. The inventors considered that the unnecessary radiation noise 1300b from the source LSI chip (controller 1100a, image signal processing circuit 1100b) can hardly enter the antenna 1200, and have intensively studied such a structure to arrive at the present invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following drawings, components having substantially the same function are denoted by the same reference numerals for the sake of brevity. In addition, this invention is not limited to the following embodiment.

  First, an example of an antenna structure applied to a mobile phone according to the present embodiment will be described with reference to FIG. 3 before describing a specific structure of a portable wireless device (for example, a mobile phone) according to the embodiment of the present invention. Is briefly explained.

  A portable wireless device (mobile phone) 100 shown in FIG. 3 is a foldable mobile phone, and the upper housing 101, the lower housing 102, and the upper housing 101 and the lower housing 102 can be bent. It is comprised from the hinge part 103 to connect. Each of the upper casing 101 and the lower casing 102 incorporates plate-like conductors 104 and 105 as upper antenna elements and a plate-like conductor (ground plate) as the lower antenna element 106.

  Feeding points 110 and 111 are provided below the plate conductors 104 and 105 of the upper casing 101, respectively. These feeding points 110 and 111 are connected to a wireless circuit unit (RF unit) 144 disposed on a printed circuit board 142 (mounting board) provided in the lower housing 102 via feeding lines 112 and 113. Yes. The feeding points (110, 111) of the antenna element may be referred to as impedance matching points between the antenna element and the RF unit (RF circuit).

  In this example, the printed circuit board 142 is composed of a multilayer wiring board, one of which is a ground pattern 143, and the ground pattern 143 functions as the lower antenna element 106. Although not shown in this figure, the printed circuit board 142 is mounted with semiconductor chips and electronic components necessary for realizing the function of the mobile phone.

  Next, the structure of the portable wireless device (mobile phone) 100 according to the embodiment of the present invention will be described with reference to FIGS. 4 (a) and 4 (b). 4A and 4B are a top view and a cross-sectional view, respectively, for explaining the outline of the configuration of the portable wireless device (mobile phone) 100 of the present embodiment.

  A portable wireless device (mobile phone) 100 according to the present embodiment includes a mounting substrate (circuit board) 10 made of a dielectric material and a semiconductor that generates a plurality of unnecessary radiation noises mounted on the mounting substrate (circuit board) 10. The chip 20 and the semiconductor chip 22, a radio circuit unit 30 provided on the mounting substrate (circuit board) 10, and an antenna element 40 connected to the radio circuit unit 30 are configured. The mounting board (circuit board) 10 includes a multilayer wiring board, and in this embodiment, one layer of the multilayer wiring board functions as the antenna element 40. The radio circuit unit 30 is electrically connected to the antenna element 40 through a feeding point 35 of the antenna element 40.

  The semiconductor chip 20 and the semiconductor chip 22 that generate unnecessary radiation noise mounted on the mounting substrate (circuit board) 10 include the semiconductor chips 20 (20a, 20b, and 20c) that generate unnecessary radiation noise. Here, “unnecessary radiation noise” refers to noise having an intensity that may adversely affect the communication of the portable wireless device (mobile phone) 100. Therefore, even if the noise is generated due to the operation of the semiconductor chip, it is “unnecessary radiation noise” as used in the present specification as long as it does not adversely affect the communication of the portable wireless device (mobile phone) 100. Not applicable.

  The semiconductor chip that generates unnecessary radiation noise is, for example, an LSI chip (for example, DSP: digital signal processor) having a digital circuit unit. As an example, as shown in FIG. 2, there are an LSI for an LCD controller, an LSI for an image signal processing circuit, and the like. The radio circuit unit (RF circuit unit) is a circuit composed of high-frequency components that operate at a reception frequency, and is composed of an analog high-frequency circuit unit. The wireless circuit unit 30 does not radiate unnecessary radiation noise.

  In the configuration of the present embodiment, the semiconductor chip 20 (20a, 20b, 20c) that generates unnecessary radiation noise is a low dielectric constant material whose dielectric constant is lower than that of the dielectric material 10a constituting the mounting substrate (circuit board) 10. It is surrounded by 10b. More specifically, the semiconductor chip 20 (20a, 20b, 20c) that generates unnecessary radiation noise has a low dielectric constant material so that the antenna current distribution in the region where the semiconductor chip 20 that generates unnecessary radiation noise is reduced. It is surrounded by 10b. The “antenna current distribution” refers to a current distribution in the antenna element 40 at a frequency when the portable wireless device (mobile phone) 100 receives a radio wave from a base station. In general, it means that the sensitivity of the antenna element 40 is better in the region where the antenna current distribution is higher. In particular, since the region where the antenna current distribution is high is a dominant part that determines the antenna characteristics, it is easy to pick up unnecessary radiation noise.

  The semiconductor chip 20a in the illustrated example is disposed on the layer of the low dielectric constant material 10b in the substrate in which the dielectric material 10a and the low dielectric constant material 10b constituting the mounting substrate (circuit board) 10 are laminated. The semiconductor chip 20b is disposed on the layer of the low dielectric constant material 10b formed on a part of the surface of the substrate made of the dielectric material 10a. The semiconductor chip 20c is built in a mounting board (circuit board) 10 made of a dielectric material 10a. Specifically, the mounting board (circuit board) 10 is covered with a low dielectric constant material 10b. It is embedded in (dielectric material 10a).

  Semiconductor chips 22 other than the semiconductor chip 20 (20a, 20b, 20c) that generate unnecessary radiation noise can be disposed on the dielectric material 10a. Further, when the radio circuit unit 30 is configured by a module (RF module) including a semiconductor chip that configures the high frequency circuit unit, the module can be disposed on the dielectric material 10a. Examples of the semiconductor chip 22 that does not generate unnecessary radiation noise include a semiconductor chip such as a transmission IC or a reception IC.

  The mounting board (circuit board) 10 is set in the housing 60. In the present embodiment, the semiconductor chip 20 (20a, 20b) that generates unnecessary radiation noise is disposed on the low dielectric constant material 10b, and above the semiconductor chip 20 (20a, 20b) that generates unnecessary radiation noise, The low dielectric constant material 60b having a lower dielectric constant than that of the dielectric material 10a (the portion of the low dielectric constant material 60b in the housing 60) is covered.

  The intensity of the antenna current distribution in the antenna element 40 (antenna ground pattern) shown in FIG. 3 is small because the end of the antenna element 40 is an open end, and tends to increase toward the center. A current concentration portion (maximum area of the antenna current) 50 is located in the central portion of the portable wireless device (cellular phone) 100 (or the central portion of the mounting substrate (circuit board) 10). Since the “current” of the antenna current distribution and the noise current distribution cannot be directly measured, the antenna magnetic field distribution is measured using a measuring instrument having a loop antenna, and the current is calculated from the magnetic field.

  Here, FIG. 5A shows the result of the measured value of the antenna current distribution when the mounting board (circuit board) 10 is made of the dielectric material 10a. In the result of FIG. 5A, the mounting substrate (circuit substrate) 10 has a structure in which the low dielectric constant material 10 b is not included in the measurement target. 5A corresponds to the size of the case of the mobile phone shown in FIG. 5B. As can be seen from FIG. 5A, a region (current concentration portion) where the intensity of the antenna current distribution is high exists at the approximate center of the mobile phone.

  On the other hand, FIG. 6A shows an actual measurement result of the noise current distribution in the same structure as FIG. A solid square in FIG. 6A also corresponds to the size of the casing of the mobile phone shown in FIG. As can be seen from FIG. 6A, in a part of the mounting substrate (circuit board) 10, there is a region with a high noise current distribution due to the presence of a semiconductor chip that generates unnecessary radiation noise.

  7A and 7B show the configuration of the mounting substrate (circuit board) 10 to be measured in FIGS. FIG. 7B is a cross-sectional view taken along line VIIB-B in FIG. A semiconductor chip 20 that generates unnecessary radiation noise is mounted on the surface of a mounting substrate (circuit substrate) 10 made of a dielectric material 10a. The semiconductor chip 20 that generates unnecessary radiation noise is connected to a chip component (chip capacitor or chip resistor) 25 via a coplanar line (CPW) composed of a strip conductor 52 and a ground conductor 54. Conductors constituting the antenna element 40a and the antenna ground 40b are formed on the left and right sides of the mounting board (circuit board) 10, respectively. In the mounting board (circuit board) 10, vias connecting the layers are formed. 56 is formed. A feeding point 35 is located at the center bottom of the mounting board (circuit board) 10. Although FIG. 7 shows a coplanar line structure, the present invention is not limited to this, and in constructing the antenna element 40, a microstrip line, a buried microstrip line, a strip line structure, or the like may be used. Is possible.

  As described above, since the antenna sensitivity is high in the region where the antenna current distribution is high (current concentration portion), the region is likely to react to unnecessary radiation noise. On the other hand, as a natural communication characteristic of a cellular phone, it is of course preferable that the antenna sensitivity is high. That is, it is preferable to design the antenna so that the antenna sensitivity is high at the frequency at which the mobile phone receives radio waves from the base station. Therefore, in order to modify the near-field characteristics without degrading the original characteristics (far field characteristics) of the antenna, generally, the electromagnetic field distribution is made of a material with a higher dielectric constant than a material with a low dielectric constant. In order to reduce the antenna current distribution in the region where the semiconductor chip 20 that generates unnecessary radiation noise is located, the configuration of the present embodiment generates unnecessary radiation noise. The semiconductor chip 20 is disposed so as to be surrounded by a low dielectric constant material 10b having a low dielectric constant. As shown in FIG. 4, the electrical distance between the antenna element 40 and the semiconductor chip 20 that generates unnecessary radiation noise is increased by surrounding the semiconductor chip 20 that generates unnecessary radiation noise with a low dielectric constant material 10b. As a result, the isolation between the two can be improved. That is, it is possible to suppress or mitigate the unnecessary radiation noise (see 1300b in FIG. 2) from the semiconductor chip 20 that generates unnecessary radiation noise from entering the antenna element 40.

  As shown in FIG. 4, the semiconductor chip 20 that generates unnecessary radiation noise can be surrounded by the low dielectric constant material 10b by various methods. Like the semiconductor chip 20a that generates unnecessary radiation noise, the low dielectric constant material 10b generates unnecessary radiation noise on the surface (the surface of the low dielectric constant material 10b) that is a part of the mounting substrate (circuit board) 10. The semiconductor chip 20 may be disposed, or the semiconductor chip 20 that generates unnecessary radiation noise may be disposed on the surface of the layer of the low dielectric constant material 10b, such as the semiconductor chip 20b. On the other hand, like the semiconductor chip 20c, the semiconductor chip 20 that generates unnecessary radiation noise may be embedded in the mounting substrate (circuit board) 10, and the periphery thereof may be covered with the low dielectric constant material 10b.

  In the case of the semiconductor chips 20a and 20b, the semiconductor chip 20 that generates unwanted radiation noise is covered with air (dielectric constant is about 1) except for the portion where the low dielectric constant material 10b is covered. Since the upper surface of the semiconductor chip 20 that generates unnecessary radiation noise is already covered with air (dielectric constant is about 1), the effect is achieved, but further, as shown in FIG. In addition, a part (60b) of the housing 60 can be made of a low dielectric constant material.

  Typically, a glass epoxy resin substrate (dielectric constant 4.2 to 4.6) is often used for the mounting substrate (circuit substrate) 10. Therefore, when the dielectric material 10a constituting the mounting substrate (circuit board) 10 is a glass epoxy resin, the low dielectric constant material 10b is a material having a lower dielectric constant. Furthermore, when a specific example of the dielectric material 10a (substrate material) constituting the mounting substrate (circuit board) 10 is given, the dielectric constant is 3.7 when the aramid nonwoven fabric epoxy resin substrate is used, and when the glass nonwoven fabric epoxy resin substrate is used. Has a dielectric constant of 3.7. The dielectric constant of FR-4, which is very often used as the mounting substrate (circuit substrate) 10, is 4.7.

  Examples of the low dielectric constant material 10b include those having a dielectric constant of 3 or less. As a specific example, the dielectric constant of Teflon (registered trademark) is 2.1. In addition, as a substrate using the low dielectric constant material 10b, R4737 (dielectric constant 2.56) manufactured by Matsushita Electric Works, GRL191D (dielectric constant 1.70), GRL3210D (dielectric constant 2.70) manufactured by Gore-Tex Junko Co., Ltd. Such a substrate material can be used.

In addition, if the dielectric constant of the dielectric material 10a (main material) constituting the mounting substrate (circuit board) 10 is large, the dielectric constant of the low dielectric constant material 10b may be more than 3. Therefore, the material options of the low dielectric constant material 10b are expanded. The dielectric material 10a constituting the mounting substrate (circuit board) 10 has a relatively high dielectric constant such as epoxy resin, ceramic powder, alumina (Al ₂ O ₃ ), silica (SiO ₂ ), titanic acid. Examples thereof include a mixture of barium (BaTiO ₂ ), titanium oxide (TiO ₂ ), strontium titanate (SrTiO ₂ ), BN, AlN, SiN and the like. Specific examples include R4728 (dielectric constant 10.50) manufactured by Matsushita Electric Works, MCL-HD67 (dielectric constant 6.0-6.1) manufactured by Hitachi Chemical, and CCL-HL820 manufactured by Mitsubishi Gas Chemical Company. (Dielectric constant 5.6) and the like, and such a substrate material can be used.

  When the dielectric constant of the housing 60 is desired to be adjusted, the dielectric constant can be adjusted by adding an inorganic filler to the material of the housing 60 or making the portion 60b of the housing 60 porous. The case 60 is a combination of the upper case and the lower case when the portable wireless device (mobile phone) 100 is a folding type, and the portable wireless device (mobile phone) 100 is a straight type. In this case, it can be one. In addition, a suitable configuration of the housing 60 is appropriately selected in accordance with a mobile phone type such as a slide type or a revolver type.

  When the portable wireless device (mobile phone) 100 according to the present embodiment is manufactured, the following may be performed. First, a mounting board (circuit board) 10 composed of a dielectric material 10a and a low dielectric constant material 10b is prepared, and then unnecessary in a region where the low dielectric constant material 10b is located on the mounting board (circuit board) 10. A semiconductor chip 20 that generates radiation noise is mounted. In the case of the semiconductor chip 20a, a substrate in which the dielectric material 10a and the low dielectric constant material 10b are bonded together is manufactured, and the semiconductor chip 20a may be placed on the surface of the substrate (the surface of the low dielectric constant material 10b). . In the case of the semiconductor chip 20b, a layer of the low dielectric constant material 10b is formed on the surface of the mounting substrate (circuit board) 10 made of the dielectric material 10a, and then the semiconductor chip 20b is mounted. In the case of the semiconductor chip 20c, it is mounted on the mounting substrate (circuit board) 10 in a form in which the semiconductor chip 20c is covered with the low dielectric constant material 10b by a method of forming a component built-in substrate. The semiconductor chip 20 that generates unwanted radiation noise (particularly in the case of the semiconductor chip 20c) may be mounted on or inside the mounting substrate (circuit substrate) 10 after first being covered with the low dielectric constant material 10b. It is.

  Next, effects of the configuration of the present embodiment will be described with reference to FIG. FIG. 8A shows a semiconductor chip 20 in which the dielectric material 10a constituting the mounting substrate (circuit substrate) 10 is FR-4 (dielectric constant (εr) = 4.9) and generates unnecessary radiation noise on the substrate. Shows a configuration example in which is implemented. On the other hand, FIG. 8B shows a configuration example in which Teflon (registered trademark) (dielectric constant = 2.1) is provided as a low dielectric constant material 10b in a region where the semiconductor chip 20 that generates unwanted radiation noise is mounted. Is shown.

  FIG. 8C shows the result of simulating isolation for these structures. As can be seen from FIG. 8C, an improvement in isolation of about 2 to 3 dB was confirmed in the frequency region band of 2 GHz. The structure shown in FIG. 8A, which is the analysis target of the simulation, has already shown good isolation characteristics. Therefore, the effect obtained by using the structure shown in FIG. Even an improvement in isolation of about 2-3 dB indicates that this was significant.

  Next, effects of the configuration of the present embodiment will be described with reference to FIG. In FIG. 9A, the dielectric material 10a constituting the mounting substrate (circuit substrate) 10 is FR-4 (dielectric constant = 4.9), and the semiconductor chip 20 that generates unnecessary radiation noise is mounted on the substrate. 2 shows a configuration example in which semiconductor chips 20 that generate unnecessary radiation noise are connected to each other by a strip conductor 52. On the other hand, FIG. 9B shows a Teflon (registered trademark) (dielectric constant) as a low dielectric constant material 10b in a part of a region where the semiconductor chip 20 that generates unwanted radiation noise and a region where the strip conductor 52 is located. = 2.1) is shown. Further, in the configuration shown in FIG. 9C, the dielectric material 10a is changed from FR-4 (dielectric constant = 4.9) to a virtual high dielectric constant material (dielectric constant = 20) (10a ′). A configuration example replaced with is shown.

  FIG. 9D shows a simulation result of isolation in the configuration shown in FIGS. 9A to 9C. As can be seen from FIG. 9D, when the lines (a) and (b) were compared, a great effect of improving the isolation characteristics was observed in the wavelength range of 1400 to 1800 MHz. Compared with the line (c), it was confirmed that the effect was further increased. The peak near 1560 MHz in the figure is a pole due to resonance, and even if the influence of the pole is ignored, the effect of the configuration of this embodiment (lines (b) and (c)) is 1400 to 1800 MHz. It was found that an average of about 10 dB to 20 dB can be obtained in the wavelength region band.

  In the structure shown in FIGS. 9B and 9C, the lower surface of the semiconductor chip 20 that generates unwanted radiation noise is not completely surrounded by the low dielectric constant material 10b. It turns out that there is an effect. Therefore, although it is preferable to completely cover the lower surface of the semiconductor chip 20 that generates unnecessary radiation noise with the low dielectric constant material 10b, a part of the semiconductor chip 20 that generates unnecessary radiation noise is covered with the low dielectric constant material 10b. There may be. Moreover, it is preferable to surround all of the semiconductor chips 20 that generate a plurality of unnecessary radiation noises with the low dielectric constant material 10b, but the semiconductor chip 20 that generates some of the unnecessary radiation noises among them is formed of the low dielectric constant material 10b. The effect of this embodiment can also be obtained by surrounding. In particular, it is desirable to cover each terminal for power supply, clock, and transmission, which is a source of unnecessary radiation noise, with a low dielectric constant material 10b.

  Next, the effect of applying the low dielectric constant material 60b to the housing 60 will be described with reference to FIG. FIG. 10A shows that the dielectric material 10a constituting the mounting substrate (circuit board) 10 is FR-4 (dielectric constant εr = 4.9), and the casing 60 has the same dielectric constant (εr as FR-4). = 4.9) shows an example of a configuration composed of a material. On the other hand, in FIG. 10B, a material (low dielectric constant material 60b) having the same dielectric constant as Teflon (registered trademark) (dielectric constant εr = 2.1) is provided above the region where the semiconductor chip 20 is mounted. The example of a structure provided is shown. The result is shown in FIG. As can be seen from FIG. 10 (c), by reducing the dielectric constant of the casing on the noise source side, the isolation can be improved in a predetermined frequency band (2 GHz band or 1600 to 2500 GHz). there were.

  According to the portable wireless device (cellular phone) 100 of the present embodiment, the semiconductor chip 20 and the semiconductor chip 22 that generate unnecessary radiation noise mounted on the mounting substrate (circuit board) 10 are semiconductors that generate unnecessary radiation noise. Since the chip 20 (20a, 20b, 20c) is surrounded by the low dielectric constant material 10b having a dielectric constant lower than that of the dielectric material 10a constituting the mounting substrate (circuit board) 10, unnecessary radiation noise is generated. The antenna current distribution in the region where the generated semiconductor chip 20 is located can be lowered, and as a result, it is possible to suppress or mitigate unwanted radiation noise (see 1300b in FIG. 2) from coming from the antenna element 40. Become.

  The semiconductor chip may be in the form of a semiconductor package (for example, chip size package (CSP)) in which the bare chip is packaged in addition to the bare chip, or in the form of an MCM (multi-chip module). There may be. Further, the interposer (intermediate substrate) is composed of the low dielectric constant material 10b, the semiconductor chip 20 that generates unwanted radiation noise is mounted on the interposer, and the module including the interposer is mounted on the mounting substrate (circuit board) 10. It is also possible to do.

  Further, the antenna element 40 is not limited to a ground plane (see the ground pattern 143 in FIG. 3) built in the mounting substrate (circuit board) 10, and may take other forms. For example, as shown in FIG. 11, a rod-shaped antenna element 40 extending on the tip side of one mounting board (circuit board) 10 (left side of the right mounting board (circuit board) 10 in the figure) can be used. . In this example, when the portable wireless device (mobile phone) 100 is a folding type, the antenna element 40 can be positioned at an upper position when folded. In addition, as shown in FIG. 12, a rod-shaped antenna element 40 that extends on the rear end side of one mounting board (circuit board) 10 (the right side of the right mounting board (circuit board) 10 in the figure) is used. Also good.

  The portable wireless device of this embodiment can include a mobile phone, a PDA, and a notebook computer having a communication function, and a portable wireless device mainly having a reception function, such as a portable television (particularly, one segment). Applicable to a wide range of portable TVs).

  As mentioned above, although this invention was demonstrated by suitable embodiment, such description is not a limitation matter and of course various modifications are possible.

  In addition, although the structure is fundamentally different from the technique of the embodiment of the present invention, a technique using a low dielectric constant substrate is disclosed in Japanese Patent Application Laid-Open No. 2001-351085. However, the content disclosed in this publication is that the digital circuit unit is arranged on a high dielectric constant substrate, contrary to the technique of the embodiment of the present invention. Therefore, the technique of the present embodiment is a technique. The philosophy is completely different.

  ADVANTAGE OF THE INVENTION According to this invention, the portable radio | wireless machine (for example, mobile phone) which took the countermeasure of unnecessary radiation noise can be provided.

The figure for demonstrating the problem about the unnecessary radiation noise of the mobile telephone 1000 Block diagram showing the basic configuration of the mobile phone 1000 The figure which showed an example of the antenna structure applied to a mobile phone (A) And (b) is the top view and sectional drawing which showed the outline of the structure of the portable radio | wireless machine (cellular phone) 100 which concerns on embodiment of this invention, respectively. (A) is a diagram showing the simulation result of the antenna current distribution (b) is a diagram showing the size of the case of the cellular phone corresponding to the solid line square in (a). (A) is a diagram showing a simulation result of noise current distribution (b) is a diagram showing the size of the case of the mobile phone corresponding to the solid line square in (a) (A) is sectional drawing which shows the structure of the mounting board | substrate of analysis object, (b) is sectional drawing along the VIIB-B line in (a). (A) is a plan view showing the configuration of the mounting substrate of the analysis target (comparative example), (b) is a plan view showing the configuration of the mounting substrate of the analysis target (embodiment), and (c) is about their isolation. Of simulation results (A) is a plan view showing the configuration of the mounting substrate of the analysis target (comparative example) (b) and (c) is a plan view (d) showing the configuration of the mounting substrate of the analysis target (embodiment). Of simulation results for the isolation of (A) is a cross-sectional view showing the configuration of the mounting substrate and casing of the analysis target (comparative example), (b) is a cross-sectional view (c) showing the configuration of the mounting substrate and casing of the analysis target (embodiment), , The figure which shows the simulation result about those isolation (A) And (b) is the top view and sectional drawing which showed the outline of the modification of the portable radio | wireless machine (cellular phone) 100 which concerns on embodiment of this invention, respectively. (A) And (b) is the top view and sectional drawing which showed the outline of the modification of the portable radio | wireless machine (cellular phone) 100 which concerns on embodiment of this invention, respectively.

Explanation of symbols

10 Mounting board (circuit board)
DESCRIPTION OF SYMBOLS 10a Dielectric material 10b Low dielectric constant material 20 Semiconductor chip which generate | occur | produces unnecessary radiation noise 22 Semiconductor chip 30 Radio | wireless circuit part 35 Feeding point 40 Antenna element 52 Strip conductor 54 Ground conductor 56 Via 60 Case 100 Portable radio | wireless machine (cell-phone)
DESCRIPTION OF SYMBOLS 101 Upper housing | casing 102 Lower housing | casing 103 Hinge part 104 Plate-like conductor 106 Lower antenna element 110 Feeding point 112 Feeding line 142 Printed circuit board 143 Ground pattern 1000 Mobile phone 1100 Digital component (digital circuit part)
1100a Controller 1100b Image signal processing circuit 1200 Antenna 1300 Unwanted radiation noise 1400 Radio circuit part (RF circuit part)
1450 Demodulator circuit 1500 Liquid crystal display

Claims (8)

A portable wireless device including a plurality of semiconductor chips,
A mounting substrate made of a dielectric material;
A plurality of semiconductor chips mounted on the mounting substrate;
A wireless circuit portion provided on the mounting substrate;
An antenna element connected to the wireless circuit unit,
Of the plurality of semiconductor chips, a first semiconductor chip that generates unwanted radiation noise is surrounded by a low dielectric constant material having a dielectric constant lower than that of the dielectric material constituting the mounting substrate. transceiver. The portable wireless device according to claim 1, wherein the first semiconductor chip is an LSI chip having a digital circuit unit. The portable wireless device according to claim 1 or 2, wherein the first semiconductor chip is surrounded by the low dielectric constant material so that an antenna current distribution in a region where the first semiconductor chip is located is lowered. . The wireless circuit unit includes a second semiconductor chip constituting a high-frequency circuit unit,
2. The portable wireless device according to claim 1, wherein the second semiconductor chip is provided on the mounting substrate other than a region where the low dielectric constant material is located. The portable wireless device according to claim 1, wherein the first semiconductor chip is embedded in the mounting substrate in a state of being covered with the low dielectric constant material. The first semiconductor chip is disposed on the layer made of the low dielectric constant material,
2. The portable wireless device according to claim 1, wherein at least an upper portion of the first semiconductor chip is covered with a housing made of a low dielectric constant material having a dielectric constant lower than that of the dielectric material constituting the mounting substrate. The portable wireless device according to any one of claims 1 to 6, wherein the portable wireless device is a mobile phone. Preparing a mounting substrate composed of a plurality of dielectric materials having different dielectric constants;
Mounting a semiconductor chip that generates unwanted radiation noise in a region where a low dielectric constant material having a lower dielectric constant than other portions of the mounting substrate is located.

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