Electronic devices, optical waveguide elements, optical modulation devices using the same, and optical transmission devices.

Abstract

To provide an electronic device (optical waveguide element) that eliminates problems such as poor adhesion and short circuits caused by excessive adhesive when bonding electronic components to signal electrodes using conductive adhesive. [Solution] The present invention provides an electronic device (optical waveguide element) comprising a wiring board 1 equipped with a signal electrode SE and a ground electrode GE for transmitting high-frequency signals, and an electronic component EP arranged on a part of the wiring of the signal electrode, wherein the signal electrode and the electronic component are electrically connected by at least two electrode pads (PD) provided at the end of the signal electrode, the electronic component is provided with a convex terminal TE at a position corresponding to the electrode pad, the shape of the electrode pad has a first cavity (OP1) corresponding to the terminal of the electronic component, and the electrode pad of the signal electrode and the terminal of the electronic component are connected by a conductive adhesive (CA).

Description

TECHNICAL FIELD

[0001] The present invention relates to an electronic device, an optical waveguide element, an optical modulation device using the same, and an optical transmission apparatus, and in particular, relates to an electronic device including a wiring board provided with a signal electrode and a ground electrode for transmitting high-frequency signals, and an electronic component disposed on a part of the wiring of the signal electrode, and the optical waveguide element as a specific example of the electronic device, and the optical modulation device and the optical transmission apparatus using the same.

BACKGROUND ART

[0002] Among various electronic devices, electronic devices in which electronic components are arranged on a wiring board that handles high-frequency signals in the microwave band are widely used. In particular, for optical waveguide elements such as optical modulators, the modulation frequency is several tens of GHz or higher, and in response to the demand for downsizing of the entire element, various electronic components may be arranged on the optical waveguide substrate on which the optical waveguide is formed (see Patent Document 1).

[0003] The problem encountered when incorporating an electronic component using an optical waveguide element which is one of the electronic devices will be described. An optical waveguide element constituting an optical modulator includes a substrate on which an optical waveguide is formed, and in order to apply an electric field based on a modulation signal to the optical waveguide, a modulation electrode composed of a signal electrode and a ground electrode is formed on the substrate. A high-frequency signal which is a microwave is applied to the signal electrode, and a termination resistor for suppressing reflection of the high-frequency signal is provided at the terminal end of the signal electrode. Further, in order to increase the modulation efficiency of the optical modulator, the high-frequency signal which is the modulation signal is amplified by an amplifier and applied to the optical waveguide element.

[0004] Figure 1 illustrates the state of the output signal output from the drive driver DRV which is an amplifier. As shown in Figure 1(a), two positive and negative signals are output from the output terminals (Port1, Port2) of the drive driver DRV. The waveform of this output signal is shown in Figure 1(b). As shown in Figure 1(b), the modulation signal (output signal) is a modulation signal to which a DC voltage (offset) of +Δv is applied from the output terminals "Port1" and "Port2".

[0005] Figure 2 shows the wiring diagram of the electrical circuit configuration related to the driving of the optical modulator. Of the two modulation signals, positive and negative, output from the drive driver DRV, one modulation signal is used. The modulation signal is input to the input terminal (In-Port) of the optical waveguide element and applied to the modulation signal's operating part (RF) of the optical waveguide element. The modulation signal is output from the output terminal (Out-Port) of the optical waveguide element, but a termination resistor TR is placed to prevent the modulation signal from being reflected at the end of the wiring and input again to the operating part RF. However, since the modulation signal is the signal state of Port1 in Figure 1(b), a DC voltage (+Δv) is continuously applied to the termination resistor TR, which not only increases power consumption but also eventually causes the termination resistor TR to burn out. For this reason, a capacitor C is placed before the termination resistor TR. In Figure 2, only one output signal of the drive driver is used, but the same problem occurs in the case of differential voltage drive.

[0006] Furthermore, in the case of Figure 2, the modulated signal with the waveform of Port1 in Figure 1(b) is applied to the RF working part to which the modulated signal is applied, and a DC voltage (+Δv) is also applied, so a DC drift phenomenon also occurs due to the DC component of the modulated signal. Furthermore, inserting a capacitor at the termination end of the signal electrode results in a large capacitor size, which in turn increases the overall size of the element. For this reason, an output terminal (Out-Port) was provided for the optical waveguide element, and an external board incorporating a capacitor C and a termination resistor TR was placed outside the element. The output terminal of the element and the external board were then electrically connected by wiring.

[0007] On the other hand, when incorporating electronic components such as capacitors into electronic devices such as optical waveguide elements, other problems arise. Specifically, in wiring such as optical waveguide substrates on which electronic components are mounted, the height of the signal electrodes is approximately 5 μm to 50 μm, and the width of the signal electrodes is also narrow, in order to suppress impedance matching and microwave propagation loss with respect to the high-frequency signal which is the modulated signal. Therefore, an expanded electrode pad (PAD; for example, the size of the bonding surface is approximately 100 × 200 μm) is formed at the end of the signal electrode on which the electronic components are placed.

[0008] Furthermore, when it comes to the electronic components to be mounted, such as capacitors that handle high-frequency signals, it becomes essential to use materials like Si capacitors. One example of a Si capacitor is an electronic component with dimensions of 300 μm x 600 μm, making it extremely small.

[0009] Generally, electronic components are fitted to signal electrodes with flip-chip terminals, and the solder constituting the flip-chip is melted by heat and fused to the electrodes. In Si capacitors, AgSn solder is used to suppress changes in resistance due to oxidation of the flip-chip. AgSn solder has a melting point of 220°C or higher, and in order to obtain a sufficient bond, it is necessary to locally raise the temperature of the wiring substrate side, such as the optical waveguide element, by an additional 30-50°C.

[0010] Heating substrates to over 250°C not only causes deformation of narrow signal electrodes, but also leads to malfunctions such as deformation and degradation of components in optical waveguide elements using resin materials such as permanent resists.

[0011] Therefore, instead of melting the flip chip of the electronic component, a low-temperature bonding process can be considered to fix the terminals of the electronic component and the signal electrode with a conductive adhesive. However, the bonding surface between the terminals of the electronic component and the electrode pad of the signal electrode is extremely small, and it is necessary to strictly control the amount of adhesive applied. If there is not enough adhesive, it will cause a poor bond, and if there is too much adhesive, it will cause a short circuit between the terminals of the electronic component or between the wiring on the wiring board. In the case of optical waveguide elements, optical waveguides with a width and height of 1 μm or less are used, and multiple optical waveguides and multiple modulation electrodes are placed in close proximity to each other. Therefore, not only is a short circuit between modulation electrodes a problem, but if conductive adhesive containing metal adheres to the optical waveguide, it can also cause optical propagation loss. In particular, in order to miniaturize the element, the electronic component and the optical waveguide may be placed in close proximity, and this problem becomes even more pronounced. [Prior art documents] [Patent Documents]

[0012] [Patent Document 1] International release WO2023 / 053406A1 [Overview of the project] [Problems that the invention aims to solve]

[0013] The problem that this invention aims to solve is to provide electronic devices and optical waveguide elements that eliminate the problems described above and prevent defects such as poor adhesion and short circuits caused by excessive adhesive when bonding electronic components to signal electrodes using conductive adhesive. Furthermore, the invention aims to provide optical modulation devices and optical transmission devices that use such optical waveguide elements. [Means for solving the problem]

[0014] To solve the above problems, the electromagnetic device, optical waveguide element, optical modulation device and optical transmission device of the present invention have the following technical features.

[0015] (1) An electronic device comprising a wiring board having a signal electrode for transmitting a high-frequency signal and a ground electrode, and an electronic component arranged on a part of the wiring of the signal electrode, wherein the signal electrode and the electronic component are electrically connected by at least two electrode pads provided at the end of the signal electrode, the electronic component has a convex terminal at a position corresponding to the electrode pad, the shape of the electrode pad has a first cavity corresponding to the terminal of the electronic component, and the electrode pad of the signal electrode and the terminal of the electronic component are connected by a conductive adhesive.

[0016] (2) The electronic device described in (1) above is characterized in that the thickness of the wall forming the first cavity is set to a range of 5% to 45% of the vertical or horizontal length of the electrode pad when viewed in plan.

[0017] (3) In the electronic device described in (1) above, the electrode pad is formed on the wiring board via a base electrode, and the first cavity is characterized in that it is a cavity that reaches the base electrode.

[0018] (4) The electronic device described in (1) above is characterized in that the first cavity is formed continuously with the first cavity on the side where the signal electrode connected to the electrode pad is located, and has an opening area smaller than the opening area of ​​the first cavity.

[0019] (5) The electronic device described in (1) above is characterized in that the height of the electrode pad is set to be higher than that of the signal electrode.

[0020] (6) In the electronic device described in (1) above, the ground electrode is arranged so as to sandwich the electrode pad, and a mark for arranging the electronic component is formed on a part of the upper surface of the ground electrode.

[0021] (7) The electronic device according to any one of the above (1) to (6) is an optical waveguide element, the wiring board is an optical waveguide board on which an optical waveguide is formed, the signal electrode and the ground electrode are modulation electrodes for modulating a light wave propagating through the optical waveguide, and the electronic component is a capacitor for cutting a DC component contained in the high-frequency signal that is a modulation signal, the optical waveguide element being characterized in that.

[0022] (8) The optical waveguide element according to the above (7), characterized in that the electronic component is disposed so as to straddle a part of the optical waveguide.

[0023] (9) The optical waveguide element according to the above (7) is housed in a housing, and the optical modulation device is characterized by comprising an optical fiber for inputting or outputting a light wave to or from the optical waveguide.

[0024] (10) The optical modulation device according to the above (9), characterized in that an electronic circuit for amplifying the modulation signal input to the modulation electrode is provided inside the housing.

[0025] (11) An optical transmission device comprising: the optical modulation device according to the above (9); and an electronic circuit that outputs the modulation signal to the optical modulation device. Effects of the Invention

[0026] The present invention relates to an electronic device comprising a wiring board equipped with a signal electrode for transmitting a high-frequency signal and a ground electrode, and an electronic component arranged on a part of the wiring of the signal electrode, wherein the signal electrode and the electronic component are electrically connected by at least two electrode pads provided at the end of the signal electrode, the electronic component has a convex terminal at a position corresponding to the electrode pad, the shape of the electrode pad has a first cavity corresponding to the terminal of the electronic component, and the electrode pad of the signal electrode and the terminal of the electronic component are connected by a conductive adhesive, so that even if there is a slight variation in the amount of conductive adhesive applied, the excess conductive adhesive can be contained in the first cavity. This makes it possible to suppress the occurrence of problems such as poor adhesion and short circuits due to excessive adhesive when joining an electronic component to a signal electrode using a conductive adhesive. Furthermore, it becomes possible to provide optical waveguide elements with such characteristics, as well as optical modulation devices and optical transmission devices using them. [Brief explanation of the drawing]

[0027] [Figure 1] (a) A circuit diagram and (b) a voltage waveform illustrating the modulated signal amplified by the drive driver. [Figure 2] This is a circuit diagram relating to a modulation signal applied to a conventional optical waveguide element. [Figure 3] (a) a cross-sectional view and (b) a plan view illustrating the bonding state of electronic components in the electronic device of the present invention. [Figure 4] This figure illustrates an example of the application of electrode pad shape in the electronic device of the present invention. [Figure 5] This figure illustrates an example in which a mark is provided on the ground electrode near the electrode pad in the electronic device of the present invention. [Figure 6] (a) A circuit diagram and (b) A voltage waveform relating to a modulation signal applied to the optical waveguide element of the present invention. [Figure 7] This is a plan view illustrating the state of the vicinity where the electronic components of the optical waveguide element of the present invention are arranged. [Figure 8]This is a cross-sectional view illustrating the arrangement of electronic components in the optical waveguide element of the present invention. [Figure 9] This figure shows an example of the optical transmission device of the present invention. [Modes for carrying out the invention]

[0028] The electronic devices and optical waveguide elements of the present invention will be described in detail below using preferred examples. As shown in Figure 3, the present invention is an electronic device comprising a wiring board 1 having a signal electrode SE and a ground electrode GE for transmitting a high-frequency signal, and an electronic component EP disposed on a part of the wiring of the signal electrode, wherein the signal electrode and the electronic component are electrically connected by at least two electrode pads (PD) provided at the end of the signal electrode, the electronic component has a convex terminal TE at a position corresponding to the electrode pad, the shape of the electrode pad has a first cavity (OP1) corresponding to the terminal of the electronic component, and the electrode pad of the signal electrode and the terminal of the electronic component are connected by a conductive adhesive (CA).

[0029] In the electronic device of the present invention, a first cavity (OP1) is formed in the electrode pad (PD) as shown in Figures 3(a) and (b). This cavity can accommodate excess conductive adhesive CA. Furthermore, the conductive adhesive CA can enter the cavity (OP1), thereby enhancing the adhesive effect of the adhesive (anchor effect).

[0030] The thickness of the wall of the first cavity (OP1) formed in the electrode pad is set to a range of 5% to 45% of the length or width of the electrode pad when viewed from above. This ensures that when the height of the wall (height of the electrode pad) is greater than the thickness of the wall (aspect ratio: height of electrode pad / thickness of the wall constituting the cavity = 1 or more), a more sufficient amount of conductive adhesive CA can be contained in the first cavity. Furthermore, as electronic components become smaller, controlling the amount of adhesive becomes more difficult. Therefore, the wall thickness of the first cavity (OP1) is preferably 5% to 30%, more preferably 5% to 20%.

[0031] The configuration of the electronic device of the present invention is suitably used in optical waveguide elements, and in particular, in order to obtain good high-frequency characteristics such as in optical waveguide elements, the height of the signal electrode is set to 5 μm or more, preferably 10 μm or more, and more preferably 20 μm or more. Moreover, since the width of the signal electrode is narrower than the height, the mechanical strength of the electrode itself is low, and the configuration of an electrode pad is indispensable when bonding electronic components.

[0032] On the other hand, the terminal TE on the electronic component (EP) side is formed by a flip chip. Generally, it is desirable for the flip chip to be stable when placed, so the connection surface is flattened. However, when applied to the electronic device of the present invention, it is preferable to have a convex shape toward the outside of the electronic component (the direction toward connection to the electrode pad). This is because a part of the convex portion of the terminal TE fits into the cavity (OP1) of the electrode pad, making it possible to easily align the electrode pad (PD) and the electronic component (EP). Furthermore, the convex shape of such terminals can be easily formed by heating and melting the flip chip, and then cooling it again, which utilizes the surface tension during molten metal formation.

[0033] Furthermore, the first cavity (OP1) of the electrode pad can also be used for positional alignment when applying conductive adhesive to the electrode pad (PD). The second cavity (OP2), described later, can also be used for positional alignment in combination with the first cavity.

[0034] Electrode pads (PDs) can be formed together with signal electrodes SE and ground electrodes GE when placed on the wiring board 1. To increase the adhesive strength between the substrate 1 and the electrodes, it is also possible to form a base electrode layer UE on the underside of the electrodes before forming the electrode bodies. The base electrode layer can be provided at all positions where signal electrodes and ground electrodes are formed, but it can also be provided locally on a part of the electrode pad (PD), as shown in Figure 3(a).

[0035] As shown in Figure 3(a), when a base electrode layer UE is provided, the first cavity (OP1) of the electrode pad can be formed deeply enough to expose the base electrode layer UE. High-frequency signals are microwaves and have high frequencies, so when they propagate through the electrode, they concentrate on the surface of the electrode due to the skin effect. Therefore, by providing a base electrode layer UE, electrode material can also be placed on the underside of the electrode pad (PD), making it possible to suppress microwave propagation loss.

[0036] It is preferable to form a step d on the upper surface (the side to which electronic components are bonded) of the electrode pad (PD), as shown in Figure 3(a). By providing this step, the conductive adhesive CA that overflows from the upper surface of the electrode pad can easily flow to the signal electrode SE side, preventing short circuits between terminals TE, etc. Furthermore, as will be described later, it is also suppressed that adhesive adheres to optical waveguides and the like that are placed between terminals TE. One way to form such a step d is to form the electrode in two stages during the manufacturing process. However, by forming the base electrode layer with a thickness of approximately 3 μm, it becomes possible to form the step only in the area where the base electrode layer UE is placed, as shown in Figure 3(a).

[0037] Figure 4 shows an example of electrode pad application, in which a second cavity (OP2) is provided adjacent to the first cavity (OP1), and the area of ​​the opening is smaller than that of the first cavity. By providing the second cavity on the side where the signal electrode SE is located, it becomes possible to provide a function that guides excess conductive adhesive towards the signal electrode side. Furthermore, the second cavity can also be used for alignment purposes, such as determining the position for adhesive application or the position for placing electronic components (EP).

[0038] Figure 5 shows that when an electronic component (dotted line frame EP) is placed, it is also possible to form a positioning marker MK for the electronic component EP on the portion that extends beyond the outside of the electronic component. The marker may be formed by creating a convex portion on the surface of the ground electrode using the aforementioned base electrode layer. It is best not to place a ground electrode GE or the like on the underside of the electronic component to prevent a short circuit between the electronic component and the electrodes on the wiring board side. Furthermore, since the ground electrode also serves as a transmission path for high-frequency signals, no markers are formed on the surface of the ground electrode facing the signal electrode. Instead, the markers are formed on the opposite side of the ground electrode or at a position away from the surface facing the signal electrode.

[0039] Next, the optical waveguide element of the present invention will be described. Figure 6(a) is a circuit diagram relating to the modulation signal of the optical waveguide element of the present invention. As described above, in conventional optical waveguide elements like the one in Figure 2, a DC voltage (+Δv) is applied to the working part of the modulation electrode to which the high-frequency signal, which is the modulation signal, is applied, resulting in a DC drift phenomenon. To avoid this, the optical waveguide element of the present invention, as shown in Figure 6(a), configures a high-frequency transmission circuit by inserting a capacitor C into the wiring to which the output of the drive driver DRV is applied, making it possible to provide the working part (RF) of the modulation electrode with a frequency characteristic (see Figure 6(b)) that cuts out the DC voltage component included in the modulation signal. As a result, power consumption (DC component) at the termination resistor TR is suppressed, and problems such as burnout of the termination resistor can be prevented. Moreover, by inserting the capacitor at an early stage in the wiring within the optical waveguide element, a DC voltage is not applied to the modulation electrode, especially the modulation electrode at the working part that applies an electric field to the optical waveguide, and the drift phenomenon due to the electro-optic effect can also be avoided. Furthermore, by suppressing burnout of the termination resistor TR, the resistive element can be miniaturized and placed on the chip (substrate) of the optical waveguide element.

[0040] Furthermore, by using capacitors that can handle high-frequency signals, such as Si capacitors, and employing the configuration of the electronic device of the present invention described above, it becomes possible to incorporate them into an optical waveguide element. Furthermore, while inserting a capacitor between the drive driver and the operating part can cause degradation of the characteristics of the electrical signal (modulated signal), the method of mounting electronic components according to the present invention makes it possible to suppress the propagation loss of high-frequency signals.

[0041] Since the optical waveguide element of the present invention can suppress the DC drift phenomenon, it is possible to use a TO (thermo-optical effect) heater that utilizes the refractive index change due to temperature changes in the optical waveguide as a bias control means for the optical modulator, instead of conventional EO (electro-optical effect) electrodes. This makes it possible to avoid the occurrence of the drift phenomenon.

[0042] Furthermore, with the miniaturization of optical waveguide elements, the optical waveguides (WG) are bent and arranged as shown in Figures 7 and 9. By arranging the capacitors (CC) placed on the chip of the optical waveguide element so as to straddle these bent sections of the optical waveguide, it becomes possible to realize even more compact optical waveguide elements.

[0043] Figure 7 is a plan view showing an example of an optical waveguide substrate with an optical waveguide WG and modulation electrodes (signal electrodes SE and ground electrodes GE) laid out. The operational section of the optical waveguide element continues to the right of Figure 7. In the operational section, the signal electrodes SE and ground electrodes GE are arranged along the optical waveguide WG, and the system is configured to apply an electric field to the optical waveguide WG.

[0044] A capacitor element (CC), which is an electronic component EP, is placed on the signal electrode SE before it is introduced into the working section (not shown). This capacitor cuts out the DC component included in the modulated signal. Electrode pads PD are formed at the ends of each signal electrode SE, and the first cavity OP1 described above is also shown.

[0045] Figure 8 is a cross-sectional view along the signal electrode SE at the location where the electronic component EP(CC) is placed. The shapes of the electrode pad (PD) and the terminals (TE) of the electronic component are basically the same as those of the electronic device described above, so no further explanation is provided.

[0046] The optical waveguide substrate 1 on which the optical waveguide WG is formed utilizes a substrate material that exhibits electro-optical effects. Specifically, substrates such as lithium niobate (LN) and lithium tantalate (LT), substrates doped with magnesium, and even PLZT, barium titanate (BTO), and lead zirconate titanate (PZT,Pb(Zr,Ti)O3) can be used. Vapor-grown films made from these materials can also be used. In this invention, the term "optical waveguide substrate" refers not only to a thin, polished plate-like body made from an LN substrate, but also to a film formed by a vapor-growth method. Furthermore, semiconductor materials can also be used as the optical waveguide substrate 1.

[0047] To increase the mechanical strength of the optical waveguide substrate 1, a retaining substrate 3 is placed below the optical waveguide substrate 1, via an intermediate layer 2. The retaining substrate 3 can be made of materials such as silicon substrates, glass, quartz, or SiPh (silicon photonics) circuits. Furthermore, the intermediate layer 2 uses dielectric materials with low dielectric constant and refractive index, such as SiO2, Al2O3, and Ta2O5. The thickness of the holding substrate 3 is set to approximately 300 to 1000 μm to increase the overall mechanical strength of the substrate, including the optical waveguide substrate. The intermediate layer 2 is made of SiO2 or the like and has a thickness of 2 to 10 μm to suppress light absorption by the holding substrate 3.

[0048] Ridge-type and rib-type irregularities are formed on the surface of the optical waveguide substrate 1, and optical waveguides WG are formed in the convex portions. The thickness of the optical waveguide substrate 1 is set to 1 μm or less for purposes such as speed matching between the microwave and optical waves of the modulated signal. Furthermore, by setting the height and width of the optical waveguide (WG) provided on the optical waveguide substrate 1 to 1 μm or less, the confinement intensity of light can be increased and the curvature of the bending of the optical waveguide can be increased (the bending radius can be decreased), making it suitable for miniaturization of the optical waveguide element. In addition, when the size of the optical waveguide (height and width of the optical waveguide WG) is reduced, electrodes can be placed closer to the optical waveguide, which reduces the driving voltage of the modulated signal and makes it possible to shorten the length of the part of the optical waveguide that is involved in the modulation operation and DC bias, thus contributing to further miniaturization.

[0049] Furthermore, it is possible to place a buffer layer (not shown) covering the optical waveguide. Transparent materials such as SiO2 can be used as the buffer layer. The thickness of the buffer layer is set in the range of 200 nm or more and 1000 nm or less. A thickness of 200 nm or more makes it possible to suppress the effects of light scattering loss due to roughness on the sides of the optical waveguide and light absorption by the charge diffusion layer. However, if the thickness of the buffer layer becomes too thick, the film stress will increase, which can cause stress-induced drift.

[0050] Gold (Au) can be used for electrode portions such as the modulation electrode. The modulation electrode plays the role of a traveling wave electrode that propagates the microwave, which is the modulation signal. For this reason, the thickness of the electrode is set to a range of 5 μm or more, more preferably 20 μm or more and 50 μm or less. Furthermore, to increase the adhesive strength between the electrode portion and the substrate 1, etc., it is also possible to use an underlay electrode layer made of Ti or Nb.

[0051] In optical waveguide elements, the optical waveguides and electrodes are densely arranged to reduce the overall size of the element. Therefore, as shown in Figures 7 and 8, the electronic component EP(CC) provided in the optical waveguide element can be positioned to straddle the optical waveguide (excluding the working part) WG, thereby contributing to the miniaturization of the element.

[0052] Next, we will describe examples of applying the optical waveguide element of the present invention to optical modulation devices and optical transmitting devices such as high-bandwidth coherent driver modulators (HB-CDMs). While we will use an example of an HB-CDM in the following description, the present invention is not limited to this and can also be applied to optical phase modulators, optical modulators with polarization synthesis functions, optical waveguide elements integrating more or fewer Mach-Zehnder type optical waveguides, bonding devices with optical waveguide elements made of other materials such as silicon, and devices for sensor applications.

[0053] As shown in Figure 9, the optical waveguide element is housed within the housing CA. Furthermore, by providing an optical fiber (F) for inputting and outputting optical waves to the optical waveguide (WG), an optical modulation device MD can be constructed.

[0054] In Figure 9, the optical fiber F is introduced into the housing CA through a through-hole penetrating the side wall of the housing CA, and the optical fiber is directly joined to the optical component or substrate. However, the optical fiber and the optical waveguide element may also be optically coupled via an optical block equipped with an optical lens optically coupled to the optical waveguide within the optical waveguide element, a lens barrel, a polarization multiplexer, etc. Furthermore, to ensure stable bonding with the optical fiber and optical block, reinforcing members can be stacked and arranged along the end face of the optical waveguide substrate.

[0055] An optical transmitter (OTA) can be configured by connecting an electronic circuit (digital signal processor DSP) that outputs a modulation signal So to the optical modulation device MD to perform modulation operations on the optical modulation device MD. In order to obtain the modulation signal S to be applied to the optical waveguide element, it is necessary to amplify the modulation signal So output from the digital signal processor DSP. For this reason, in Figure 9, a driver circuit DRV is used to amplify the modulation signal. The driver circuit DRV and the digital signal processor DSP can be placed outside the housing CA, but they can also be placed inside the housing CA. In particular, by placing the driver circuit DRV inside the housing, it is possible to further reduce the propagation loss of the modulation signal from the driver circuit.

[0056] Figure 9 shows an example where an electronic component (capacitor element) CC is placed on a portion of the signal electrode SE. At the location where the electronic component is placed, the optical waveguide WG can be set to various shapes as shown in Figure 7.

[0057] The optical modulation device described above is shown in its assembled state within a housing, but the optical waveguide elements and individual components, which are sub-assembly products at the stage before assembly into the housing, are also included in the optical modulation device of the present invention. Furthermore, while the above-described example of a modulation electrode in an optical waveguide element illustrates a single modulation signal, it goes without saying that the present invention is not limited to this and can also be applied to differential electrode configurations using differential signals. [Industrial applicability]

[0058] As described above, the present invention makes it possible to provide electronic devices and optical waveguide elements that eliminate problems such as poor adhesion and short circuits due to excessive adhesive when bonding electronic components to signal electrodes using a conductive adhesive. Furthermore, it is possible to provide optical modulation devices and optical transmission devices using such optical waveguide elements. [Explanation of Symbols]

[0059] 1 Wiring board (optical waveguide board) 2. Middle class 3 Holding board EP electronic components CC capacitor element TE connector (flip chip) CA conductive adhesive PD electrode pads OP1 1st cavity OP2 2nd cavity SE signal electrode GE ground electrode WG optical waveguide F Optical Fiber CA cabinet MD Optical Modulation Device DRV driver circuit DSP (Digital Signal Processor) OTA Optical Transmitter

Claims

1. An electronic device comprising a wiring board equipped with a signal electrode for transmitting a high-frequency signal and a ground electrode, and an electronic component arranged on a part of the wiring of the signal electrode, The signal electrode and the electronic component are electrically connected by at least two electrode pads provided at the end of the signal electrode. The electronic component is provided with a convex terminal at a position corresponding to the electrode pad, The shape of the electrode pad has a first cavity corresponding to the terminal of the electronic component, An electronic device characterized in that the electrode pad of the signal electrode and the terminal of the electronic component are connected by a conductive adhesive.

2. In the electronic device described in claim 1, An electronic device characterized in that the thickness of the wall forming the first cavity is set to a range of 5% to 45% of the vertical or horizontal length of the electrode pad when viewed from above.

3. In the electronic device described in claim 1, The electrode pad is formed on the wiring board via a base electrode, The electronic device is characterized in that the first cavity extends to the underlying electrode.

4. In the electronic device described in claim 1, The electronic device is characterized in that the first cavity has a second cavity formed continuously with the first cavity on the side where the signal electrode connected to the electrode pad is located, and having an opening area smaller than the opening area of ​​the first cavity.

5. In the electronic device described in claim 1, An electronic device characterized in that the height of the electrode pad is set to be higher than that of the signal electrode.

6. In the electronic device described in claim 1, The grounding electrode is positioned so as to sandwich the electrode pad. An electronic device characterized in that a mark for positioning the electronic component is formed on a part of the upper surface of the ground electrode.

7. The electronic device according to any one of claims 1 to 6 is an optical waveguide element, The wiring board is an optical waveguide board in which optical waveguides are formed, The signal electrode and the ground electrode are modulation electrodes that modulate the light waves propagating through the optical waveguide. The optical waveguide element is characterized in that the electronic component is a capacitor for cutting the DC component contained in the high-frequency signal, which is a modulated signal.

8. In the optical waveguide element according to claim 7, The optical waveguide element is characterized in that the electronic component is arranged so as to straddle a portion of the optical waveguide.

9. The optical waveguide element described in claim 7 is housed within a housing, An optical modulation device characterized by comprising an optical fiber that inputs or outputs an optical wave to the optical waveguide.

10. In the optical modulation device according to claim 9, An optical modulation device characterized by having an electronic circuit inside the housing that amplifies the modulation signal input to the modulation electrode.

11. The optical modulation device according to claim 9, An optical transmitting device characterized by having an optical modulation device and an electronic circuit that outputs the modulation signal.

Images