JP7531666B2 - Optical module and manufacturing method thereof - Google Patents

Description

This application relates to an optical module and a manufacturing method thereof.

Optical transceivers, which contain built-in optical modules, are essential components in optical communication systems, but there is a demand for optical communication networks to be faster and have higher capacity to accommodate the increasing data traffic every year. Transmission capacity can be increased by improving the mounting density and characteristics of optical modules, but to increase the mounting density, miniaturization of components within the optical module and high-density mounting technology are required.

Conventionally, wire bonding has been used to assemble optical semiconductor elements. However, because wire bonding connects the optical semiconductor element and the insulating substrate with wires, it is not possible to stack other components on the surface on which the electrode pads are formed. In addition, there is a problem that backward waves are generated between the optical semiconductor element and the insulating substrate, causing significant deterioration of characteristics.

To solve this problem, for example, Patent Document 1 discloses flip-chip mounting technology in which an optical semiconductor element is inverted and connected to an insulating substrate by terminals on protrusions called bumps, and among these, a technology using ultrasonic bonding is disclosed, which is a comprehensively superior method in terms of cost, connection reliability, bonding load, connection pitch accuracy, etc. In flip-chip mounting using ultrasonic bonding, the reverse side of an inverted optical semiconductor element is generally attracted by a suction collet, and the element is mounted on the surface of an insulating substrate with a larger projected area than the optical semiconductor element.

JP 2012-009599 A (paragraphs 0026 to 0029, FIG. 2)

However, because conventional wire bonding is used for wiring to electrically connect the insulating substrate to an external electronic circuit of the optical module, there is a problem in that it is necessary to secure an area for forming electrode pads for wire bonding to other surrounding components on the same surface of the insulating substrate, in addition to the electrode pads connected to the optical semiconductor element. Also, in order to fix the optical semiconductor element in the optical module, it is necessary to bond it to a submount or other component with solder, which increases thermal stress caused by the difference in linear expansion coefficient with the surrounding components due to preheating during flip-chip mounting, heat generation due to operation of the optical semiconductor element, and cooling, resulting in a problem of impaired reliability of the bump joint. Another problem is that the pressure and vibration generated when wire bonding is performed on the surface of the insulating substrate mounted on the optical semiconductor element generates stress in the bump joint, making the joint more susceptible to destruction.

This application has been made to solve the above problems, and aims to provide an optical module that is compact, highly dense, high speed, large capacity, and highly reliable, as well as a manufacturing method thereof.

The optical module disclosed in the present application comprises a semiconductor element made of InP with electrode pads formed on its surface, an insulating substrate with electrode pads formed on its front and back surfaces, and bumps for joining the electrode pads on the back surface of the insulating substrate to the electrode pads of the semiconductor element , the back surface of the insulating substrate being disposed opposite the front surface of the semiconductor element, the electrode pads on the back surface of the insulating substrate being connected to the electrode pads on the front surface of the insulating substrate via through holes, and the area of the surface of the insulating substrate on which the electrode pads are formed is smaller than the area of the surface on which the electrode pads of the semiconductor element are formed .
The optical module disclosed in the present application comprises a semiconductor element made of InP with an electrode pad formed on its surface, an insulating substrate with electrode pads formed on its front and back surfaces, and bumps for joining the electrode pads on the back surface of the insulating substrate to the electrode pads of the semiconductor element, the back surface of the insulating substrate being disposed opposite the front surface of the semiconductor element, the electrode pads on the back surface of the insulating substrate being connected to the electrode pads on the front surface of the insulating substrate via through holes, and the bumps being disposed on an edge of one end of the insulating substrate that is connected to the outside, and on an edge of the other end opposite the one end.

The method for manufacturing an optical module disclosed in the present application includes the steps of providing bumps on the surfaces of electrode pads formed on the surface of a semiconductor element made of InP or on the surfaces of electrode pads formed on the back surface of an insulating substrate, placing the insulating substrate on the semiconductor element in a position where the electrode pads of the semiconductor element and the electrode pads of the insulating substrate face each other, heating the bumps while the insulating substrate is placed on the semiconductor element, and ultrasonically bonding the electrode pads of the insulating substrate or the electrode pads of the semiconductor element to the bumps while applying pressure , wherein the insulating substrate is characterized in that the area of the surface on which the electrode pads are formed is smaller than the area of the surface on which the electrode pads of the semiconductor element are formed .
In addition, the manufacturing method of an optical module disclosed in the present application includes the steps of providing bumps on the surfaces of electrode pads formed on the surface of a semiconductor element made of InP or on the surfaces of electrode pads formed on the back surface of an insulating substrate, placing the insulating substrate on the semiconductor element in a position where the electrode pads of the semiconductor element and the electrode pads of the insulating substrate face each other, heating the bumps while the insulating substrate is placed on the semiconductor element, and ultrasonically bonding the electrode pads of the insulating substrate or the electrode pads of the semiconductor element to the bumps while applying pressure, and is characterized in that the bumps are disposed on an edge portion of one end of the insulating substrate that is connected to the outside and on an edge portion of the other end opposite the one end.

This application makes it possible to achieve miniaturization and high density, and to obtain a high-speed, large-capacity, and highly reliable optical module.

1 is a cross-sectional view showing a configuration of an optical module according to a first embodiment. 1 is an enlarged cross-sectional view showing a configuration of an optical module according to a first embodiment; FIG. 1 is a top view showing a configuration of a conventional optical module. FIG. 11 is a top view showing another configuration of a conventional optical module. 1 is a top view showing a configuration of an optical module according to a first embodiment; FIG. 11 is a top view showing a configuration of an optical module according to a second embodiment. 13 is a top view showing the arrangement of bumps of the optical module according to the second embodiment and another optical module. FIG. 13A and 13B are diagrams illustrating the relationship between the arrangement of bumps and stress in an optical module according to a second embodiment. 11A to 11C are cross-sectional views showing a manufacturing method of an optical module according to a third embodiment. 13A to 13C are top views showing an optical module manufacturing method according to a fourth embodiment.

The optical module according to the embodiment will be described below with reference to the drawings. Note that the same or similar components in each drawing are given the same reference numerals. Also, to avoid the following description becoming insufficiently redundant and to facilitate understanding by those skilled in the art, detailed descriptions of already well-known matters and duplicate descriptions of substantially identical configurations may be omitted. Also, the contents of the following description and drawings are not intended to limit the subject matter described in the claims.

The size or scale of each corresponding component part is independent between the figures. For example, the size or scale of the same component part may differ between a figure in which a part of the configuration has been changed and a figure in which the configuration has not been changed. Furthermore, although the configuration of the optical module is actually provided with multiple additional components, to simplify the explanation, only the parts necessary for the explanation are shown, and explanations of the other parts are omitted.

In the following explanation, an optical module is used as an example, but each embodiment can also be applied to semiconductor devices that handle power and normal currents, which have similar issues rather than light.

Embodiment 1.
Fig. 1 is a cross-sectional view showing the configuration of an optical module 1001 according to a first embodiment of the present invention. Fig. 1(a) is a cross-sectional view of the optical module 1001, and Fig. 1(b) is a cross-sectional view of the optical module 1001 taken along the line AA in Fig. 1(a). Fig. 2 is an enlarged cross-sectional view of a region B in Fig. 1(a).

As shown in Figures 1(a) and 1(b), the optical module 1001 has, as its basic components, an optical semiconductor element 10, a submount 20, and an insulating substrate 30. The back surface of the optical semiconductor element 10 is joined to the electrode pad 20b on the surface of the submount 20 by solder 70 via electrode pad 10c, and the back surface of the insulating substrate 30 is ultrasonically joined to the surface of the optical semiconductor element 10 opposite to the back surface to which the submount 20 is joined by Au bumps 50 via electrode pads 10b and 30b, respectively. The surface of the insulating substrate 30 is electrically connected to the outside via an IC 110, which is joined to the case 100 by solder 70, with Au wires 60 wired via electrode pads 30c.

The electrode pad 20c of the submount 20 is bonded to the surface of the thermo module 40 via the metallization 40a using Ag paste 80, and on the same surface of the thermo module 40 to which the submount 20 is bonded, a lens 120 and a multiplexer 130 are each bonded with a resin adhesive 90 at positions corresponding to the laser output direction of the optical semiconductor element 10.

The thermo module 40 is housed in the case 100, and the back surface of the thermo module 40 opposite the surface on which the submount 20 and lens 120 are provided is bonded to the case 100 by Ag paste 80 via the metallization 40b.

This will be explained in more detail below. Note that FIG. 1 illustrates only the basic components of the optical module 1001, and does not illustrate other components such as optical semiconductor elements, ICs, Au wires, capacitors, FPCs, etc.

The optical semiconductor element 10 is, for example, an LD (Laser Diode) or PD (Photo Diode) that converts an electrical signal into an optical signal and vice versa, and is made of, for example, InP, GaAs, GaN, InGaAs, Ge, or Si. In this embodiment, a Mach-Zehnder modulator (hereinafter, MZ modulator) made of InP is used. Note that the number of laser light generating parts in the optical semiconductor element 10 is not limited, but in this embodiment, multiple laser light generating parts are formed, which makes the effect of the present application more effective.

The optical semiconductor element 10 is electrically and mechanically bonded to the insulating substrate 30 by Au bumps 50, so electrode pads 10b that can be electrically connected to the insulating substrate 30 and dummy pads for mechanically fixing the insulating substrate 30 are formed by Au metallization.

In the first embodiment, the optical module 1001 is equipped with one MZ modulator, but other optical semiconductor elements, which are not described because they are not necessary for the explanation of this application, are also equipped in the optical module 1001, and the number of optical semiconductor elements 10 is not limited to one.

1B, the submount 20 has a ceramic substrate 20a, electrode pads 20b formed on the front surface of the ceramic substrate 20a, and electrode pads 20c formed on the back surface. The ceramic substrate 20a is an electrical insulator, and is preferably made of a material with high thermal conductivity to effectively cool the optical _{semiconductor} element 10. Generally, a ceramic plate such as AlN or _Al2O3 is used.

In the first embodiment, the number of submounts 20 mounted on the optical module 1001 is one, but the number of submounts 20 is not limited to one. Multiple optical semiconductor elements may be bonded to one submount.

The electrode pads 20b and 20c are generally made of the same material. The optical semiconductor element 10 is soldered to the electrode pad 20b on the surface formed on the circuit side with solder 70, and the electrode pad 20b is electrically connected to the surrounding members and the surface of the optical semiconductor element 10 by forming a joint with an Au wire 60 or the like. Since such electrode pads 20b are wiring members for electrically connecting the optical semiconductor element 10 to an external circuit, a metal with low electrical resistance is preferable.

The electrode pads 20b and 20c are generally metallized with Au or the like to a thickness of, for example, 3.0 μm or less. In the present embodiment 1, the electrode pads 20b made of Au and having a thickness of 1.0 μm are metallized on the ceramic substrate 20a made of AlN and having a thickness of 0.5 mm, and a submount 20 is used in which the electrode pads 20b are pre-coated with AuSn solder 70 having a thickness of 5 μm at the locations where the optical semiconductor element 10 is soldered.

The electrode pad 20c on the back surface, which corresponds to the heat dissipation surface, is mechanically and thermally connected to the inner wall of the case 100 via solder or Ag paste, etc. In the present embodiment 1, it is connected with Ag paste 80.

2, the insulating substrate 30 has a ceramic base material 30a, an electrode pad 30b formed on the back surface of the ceramic base material 30a, and an electrode pad 30c formed on the front surface, similar to the submount 20. The ceramic base material 30a is an electrical insulator, and generally a ceramic plate such as _AlN or _Al2O3 is used. In the first embodiment, the insulating substrate 30 mounted on the optical module 1001 is ultrasonically bonded to the optical semiconductor element 10 by Au bumps 50, but the number of insulating substrates 30 is not limited and may be one or more.

The electrode pads 30b and 30c are generally made of the same material. The electrode pads 30b formed on the back surface of the ceramic substrate 30a are joined to the electrode pads 10b on the front surface of the optical semiconductor element 10 by Au bumps 50, and the electrode pads 30b joined to the optical semiconductor element 10 are electrically connected to the electrode pads 30c on the front surface by through holes 30d and side metallization, etc. The electrode pads 30c electrically connected to the electrode pads 30b are further electrically connected to the surrounding members by forming a joint with an Au wire 60, etc. Such electrode pads 30b and 30c are wiring members for electrically connecting the optical semiconductor element 10 to an external circuit, so a metal with low electrical resistance is preferable.

The electrode pads 30b and 30c are generally metallized with Au or the like to a thickness of, for example, 3.0 μm or less. In this embodiment 1, the electrode pads 30b and 30c made of Au and having a thickness of 1.0 μm are metallized on the ceramic substrate 30a made of AlN and having a thickness of 0.25 mm, and the electrode pads 30b and 30c are electrically connected by a through hole 30d provided in the ceramic substrate 30a. Furthermore, the electrode pad 30c is electrically connected to the IC 110 by an Au wire 60.

The thermo module 40 transfers the heat received by the heat absorption section to the heat dissipation section via the Peltier element, and releases the heat from the heat dissipation section, for example, to the case 100. In this way, the temperature of the optical semiconductor element 10 is controlled by the thermo module 40. This allows the optical semiconductor element 10 to continue to operate stably.

As shown in FIG. 1, the thermo module 40 is bonded to the case 100 with Ag paste 80 so that the surface to which the submount 20 is bonded is the main surface and the main surface faces the positive direction of the Z axis. Therefore, metallization 40a is formed on the bonding surfaces of the thermo module 40 with the submount 20, the lens 120, and the multiplexer 130, and metallization 40b is formed on the bonding surface with the case 100 by the Ag paste 80.

The metallizations 40a and 40b are generally made of the same material. For example, the metallizations 40a and 40b are made of Au with a thickness of about 3.0 μm or less.

The Au bumps 50 electrically and mechanically connect the electrode pads 10b and dummy pads formed on the front surface of the optical semiconductor element 10 to the electrode pads 30b formed on the rear surface of the insulating substrate 30, or mechanically connect the electrode pads 10b and dummy pads formed on the front surface of the optical semiconductor element 10 to the electrode pads 30b formed on the rear surface of the insulating substrate 30. Metals with high thermal conductivity are preferred as the material for the Au bumps 50. For this reason, Au, Cu, Al, solder, etc. are generally used alone or in combination, and are bonded by methods such as heating, pressure, ultrasonic waves, and soldering.

In the first embodiment, stud bumps are formed by cutting the wire after the first bonding of Au wire bonding (ball bonding) to the electrode pads 30b formed on the insulating substrate 30, and are ultrasonically bonded to the electrode pads 10b and dummy pads of the optical semiconductor element 10. In addition, an Au wire with a diameter of φ25 μm is used, and the bump size is about φ45 μm, with a height to the tip of about 45 μm.

The Au wire 60 electrically connects the electrode pad 30c formed on the surface of the insulating substrate 30 to the electrode pads 20b formed on the surfaces of the IC 110 and the submount 20. A metal with low electrical resistance is preferable for the material of the Au wire 60. For this reason, Au, Cu, Al, etc. are generally used alone or in combination, and are mainly bonded by ultrasonic waves.

In FIG. 1 of the first embodiment, Au wire bonding (ball bonding) is used to bond the electrode pad 30c formed on the insulating substrate 30 to the IC 110, and to bond the IC 110 to the case 100. However, Au wire 60 is also used to connect other components whose description is omitted because it is not necessary for the explanation of this application, and the number of locations where Au wire 60 is used is not limited to two.

The solder 70 joins the electrode pad 20b formed on the surface of the submount 20 to the electrode pad 10c formed on the back surface of the optical semiconductor element 10. When the optical semiconductor element 10 is joined to the submount 20 by the solder 70, the submount 20 is not yet bonded by the thermo module 40 and the Ag paste 80. Therefore, the material of the solder 70 is preferably a metal with a melting point higher than the hardening temperature of the Ag paste 80 and a high thermal conductivity so that the solder 70 does not remelt when joined with the Ag paste 80. Therefore, the solder 70 generally uses an alloy containing Sn, Pb, Au, Ag, Cu, Zn, Ni, Sb, Bi, In, Ge, etc. and having a melting point of less than 450°C, but it is preferable to use an alloy containing mainly Sn, Au, Ag, Cu, etc. and having a melting point of 200°C or more. In addition, the thickness of the solder 70 is preferably 0.1 mm or less in terms of the inclination and warping of the element. In this embodiment 1, a eutectic solder of Sn and Au is used.

The Ag paste 80 bonds the electrode pads 20c formed on the back surface of the submount 20 to the metallization 40a formed on the surface of the thermo module 40, and the metallization 40b formed on the back surface of the thermo module 40 to the case 100. When the submount 20 is bonded to the thermo module 40 by the Ag paste 80, the optical semiconductor element 10 is joined to the submount 20 by the solder 70. Therefore, it is desirable for the material of the Ag paste 80 to have a hardening temperature lower than the melting point of the solder 70 and a high thermal conductivity so that the solder 70 does not remelt when the Ag paste 80 is bonded. For this reason, Ag paste 80 generally uses a conductive adhesive that combines an organic binder such as epoxy or phenol with conductive fillers that are spherical or flaky metals such as Au, Ag, or Cu, but as long as it can bond or join at a temperature at which solder 70 does not remelt and has a high thermal conductivity, it may also be a bonding material that uses a metal material such as solder or a sintered material, or an insulating adhesive that does not contain metal. In this embodiment 1, Ag paste 80 is used that combines flake-shaped Ag particles with an epoxy binder.

The resin adhesive 90 bonds the lens 120 and the metallization 40a formed on the surface of the thermo module 40, and the multiplexer 130 and the metallization 40a, respectively. When the resin adhesive 90 bonds the respective components, the optical semiconductor element 10 is bonded to the submount 20 by the solder 70. Therefore, it is desirable that the material of the resin adhesive 90 has a hardening temperature lower than the melting point of the solder 70 so that the solder 70 does not remelt when the resin adhesive 90 is bonded, a viscosity that does not wet and spread to the surroundings, and a tackiness that does not move the mounted lens 120 and the multiplexer 130. It is more preferable if the resin can be hardened and bonded by a method other than heating, such as irradiation with ultraviolet rays. In addition, in this embodiment 1, the metallization 40a and the lens 120 bonded by the resin adhesive 90, and the metallization 40a and the multiplexer 130 are not conductive paths, so the resin adhesive 90 does not need to be conductive.

The case 100 is a flat box having a flat bottom to which the metallization 40b formed on the back surface of the thermo module 40 is adhered by Ag paste 80, multiple sides connected to the outer edge of the bottom, and an opening surrounded by the multiple sides. As shown in FIG. 1, one side of the case 100 is provided with an emission section for guiding the wavelength-multiplexed laser light multiplexed by the multiplexer 130 to an optical fiber (not shown).

Lens 120 is made of glass or transparent resin, and focuses the laser light emitted from optical semiconductor element 10. In this embodiment 1, only one lens 120 is shown, but multiple lenses are mounted in the depth direction of FIG. 1 according to the number of light sources of optical semiconductor element 10, and the number is not limited to one.

The multiplexer 130 multiplexes the light emitted from the optical semiconductor elements 10 and outputs the multiplexed light. The multiplexed light output from the multiplexer 130 is transmitted as a wavelength multiplexed signal through a lens 120 provided in the case 100 and along an optical waveguide such as an optical fiber.

Figure 3 is a top view showing the configuration of a conventional optical module. Conventional optical modules are equipped with multiple optical semiconductor elements 10 to increase transmission capacity, and many components must be installed, such as lenses and multiplexers. However, because the outer diameter dimensions of the optical module case are fixed, high-density mounting technology is required to mount all of the components inside the case.

In conventional optical modules, wire bonding using Au wires 60 was used to connect the optical semiconductor element 10 and submount 20 to the insulating substrate 30. However, it is difficult to stack components using wire bonding, and in addition, there is a concern that a backward wave will occur between the optical semiconductor element 10 and the insulating substrate 30, which may cause significant degradation of characteristics.

To prevent the occurrence of these backward waves and improve the characteristics while stacking the components, flip-chip mounting technology is used to connect the inverted optical semiconductor element 10 and the insulating substrate 30 with Au bumps 50. Among these, ultrasonic bonding is used, which is a method that is comprehensively superior in terms of cost, connection reliability, bonding load, connection pitch accuracy, etc.

Figure 4 is a top view showing the configuration of a conventional optical module that uses ultrasonic bonding flip-chip mounting technology. In ultrasonic bonding flip-chip mounting, the optical semiconductor element 10 is generally inverted and its back surface is attracted by a collet, and mounted on the surface of a submount 20 that has a larger projected area than the optical semiconductor element 10. However, for example, wiring from the submount 20 and insulating substrate 30 to feedthroughs and the like for electrically connecting to an external electronic circuit provided in the case is conventionally performed by wire bonding using Au wires 60.

Therefore, it is necessary to form electrode pads 20b for wire bonding to other surrounding components on the same surface of the submount 20 in addition to the electrode pads 20b connected to the optical semiconductor element 10, and since these electrode pads 20b must be formed outside the projected area of the optical semiconductor element 10, it is necessary for the submount 20 to be larger than the optical semiconductor element 10 by at least the area of the electrode pads 20b for wire bonding to other components. In addition, other components cannot be mounted on the back surface of the inverted optical semiconductor element 10, that is, on the surface of the optical semiconductor element 10 shown in Figure 4.

Figure 5 is a top view showing the configuration of the basic components of the optical module according to the first embodiment of the present application. As shown in Figures 5 and 2, the optical module 1001 is provided with an optical semiconductor element 10 having electrode pads 30b and 30c formed on both sides of the basic components and electrically connected to each other by through holes 30d.

This configuration not only allows the optical semiconductor element 10 to be miniaturized by eliminating the electrode pads for wire bond mounting from the optical semiconductor element 10 as in conventional flip chip mounting, but also allows the insulating substrate 30, which is smaller than the optical semiconductor element 10, to be mounted on the optical semiconductor element 10, and allows the optical semiconductor element 10 and insulating substrate 30, which could only be mounted in the XY directions shown in Figures 3 and 4 in the conventional method, to be mounted all in the Z direction, thereby enabling high-density mounting of components. In addition, electrode pads 30c for wire bonding to other surrounding components can be formed on the surface of the insulating substrate 30 mounted on the optical semiconductor element 10, allowing the components to be densified and miniaturized more than in conventional flip chip mounting. In addition, the surface of the insulating substrate 30, which has a smaller projected area than the optical semiconductor element 10, can be adsorbed by a collet and mounted on the surface of the optical semiconductor element 10.

As described above, the optical module 1001 according to the first embodiment includes an optical semiconductor element 10 having an electrode pad 10b formed on its surface, an insulating substrate 30 having electrode pads 30c, 30b formed on its front and back surfaces, and Au bumps 50 for connecting the electrode pads 30b on the back surface of the insulating substrate 30 to the electrode pads 10b of the semiconductor element 10. The back surface of the insulating substrate 30 is disposed opposite the front surface of the semiconductor element 10, and the electrode pads 30b on the back surface of the insulating substrate 30 are connected to the electrode pads 30c on the front surface of the insulating substrate 30 via through holes 30d. This eliminates the electrode pads for wire-bond mounting from the optical semiconductor element, thereby reducing the size of the optical semiconductor element. Furthermore, by electrically and mechanically connecting the optical semiconductor element and the insulating substrate using Au bumps, rather than the conventional wire bonding using Au wires, the frequency characteristics can be improved compared to the case of connecting by wire bonding. In addition, by mounting the insulating substrate in the thickness direction of the optical semiconductor element, the area required for mounting the optical semiconductor element, submount, and insulating substrate can be reduced, allowing for a high density optical module. This makes it possible to obtain a high speed, high capacity optical module compared to conventional methods.

Embodiment 2.
In the first embodiment, the Au bumps 50 are evenly arranged on the surface of the insulating substrate 30, but in the second embodiment, a case where the Au bumps 50 are arranged on both ends of the insulating substrate 30 will be described.

Figure 6 is a top view showing the configuration of an optical module 1001 according to embodiment 2 of the present application. As shown in Figure 6, in the optical module 1001 according to embodiment 2, the Au bumps 50 are concentratedly arranged along both ends of the insulating substrate 30.

The basic configuration of the optical module 1001 in the second embodiment is the same as that of the optical module 1001 in the first embodiment, but differs only in the arrangement of the Au bumps 50 shown in FIG. 6. Therefore, the differences will be mainly described here, and the description of the same components will be omitted. Note that FIG. 6 illustrates only the optical semiconductor element 10, submount 20, insulating substrate 30, and Au bumps 50 in the optical module 1001 according to the second embodiment, and the description of the other components will be omitted.

In the optical module 1001 of the first and second embodiments, thermal stress occurs due to heating when the submount 20 and the solder 70 are joined, preheating during flip-chip mounting, and heat generation accompanying operation of the optical semiconductor element 10. Thermal stress may also occur due to differences in the linear expansion coefficient with the surrounding materials caused by cooling. Possible methods for reducing thermal stress occurring at the joints of the Au bumps 50 include increasing the number of Au bumps 50 or arranging the Au bumps 50 evenly on the surface of the insulating substrate 30 as shown in the first embodiment.

When multiple laser light generating units are formed in the optical semiconductor element 10 to increase the capacity of the optical module 1001, the multiple laser lights output from the optical semiconductor element 10 are collected by the lens 120 and combined by the combiner 130 as shown in FIG. 1. Therefore, in order to stably output the combined light, it is preferable to align the electrode pads 10b formed on the optical semiconductor element 10 in a row with respect to the laser light generating units as shown in FIG. 6.

Figure 7 is a top view showing another arrangement of bumps in an optical module. When multiple laser light generating units are formed on a single optical semiconductor element 10 to increase the capacity of the optical module 1001, if dummy electrodes for mechanically fixing the insulating substrate 30 to the optical semiconductor element 10 while stably outputting the combined light are to be arranged evenly on the surface of the insulating substrate 30, the electrodes on the surface of the insulating substrate 30 are, for example, arranged in a row of Au bumps 50 at the end of one side of the insulating substrate 30, and the other Au bumps 50 are arranged evenly on the surface of the insulating substrate 30, as shown in Figure 7 (a).

When the Au bumps 50 are arranged in this manner, if thermal stress occurs at the joints of the Au bumps 50, there is a concern that the thermal stress occurring at the joints of the Au bumps 50 arranged within the surface of the insulating substrate 30 will be uneven, and the joints of the Au bumps 50 that are subject to the highest thermal stress will be more likely to peel off.

As a countermeasure, it is possible to increase the number of Au bumps 50, but the load required for flip-chip mounting increases according to the increased number of Au bumps 50. In the configuration of the second embodiment, vibration occurs between the electrode pads 30c on the surface of the insulating substrate 30 and the surface of the suction collet, and the increased load may cause problems such as deformation of the electrode pads 30c, which may come into contact with adjacent electrode pads 30c and cause a short circuit. In addition, dummy electrode pads 10b are required on the optical semiconductor element 10 according to the increased number of Au bumps 50, which increases the size of the optical semiconductor element 10.

Therefore, in this second embodiment, as shown in FIG. 6, the Au bumps 50 are concentrated on both ends of the insulating substrate 30 as a method for ensuring the reliability required for the product by evenly distributing the stress generated at the joints of the Au bumps 50 while stably outputting multiplexed light to multiple laser light generating units on the optical semiconductor element 10 and miniaturizing the optical semiconductor element 10 without increasing the number of dummy pads.

This makes it possible to suppress the increase in thermal stress that occurs at the junction of a particular Au bump 50 during cooling after flip-chip mounting, compared to when the Au bumps 50 are evenly arranged within the substrate as shown in FIG. 7(a) and when the Au bumps 50 are arranged along the outer periphery of the substrate as shown in FIG. 7(b). Figure 8 shows the results of a stress analysis of the bump arrangement of the optical module according to embodiment 2 and other bump arrangements.

Regarding the number and arrangement of the Au bumps 50, in the case where the optical semiconductor element 10 has a plurality of laser light generating units formed thereon as in the second embodiment, and the electrode pads 10b are formed in a row, there is no problem in arranging the Au bumps 50 at other positions on the insulating substrate 30, as long as the Au bumps 50 are arranged so as to face both ends of the insulating substrate 30. However, as described above, if the number of Au bumps 50 increases, problems such as shorts between the electrode pads 30c formed on the insulating substrate 30 during flip-chip mounting and an increase in the size of the optical semiconductor element 10 may occur. Therefore, it is preferable to arrange the Au bumps 50 as dummy electrodes on the opposing sides in a number equal to the number of electrode pads 10b arranged in a row according to the number of laser light generating units formed on the optical semiconductor element 10.

In addition, as shown in FIG. 1, the insulating substrate 30 mounted on the optical semiconductor element 10 is connected to the IC 110 and the like by the Au wire 60 from the electrode pad 30c formed on its surface. At this time, in order to shorten the Au wire 60, it is preferable to form the electrode pad 30c for bonding the Au wire 60 at the end of the insulating substrate 30. In addition, since the Au wire 60 is wire-bonded after the insulating substrate 30 is mounted on the optical semiconductor element 10, stress is generated at the joint of the Au bump 50 due to pressure applied by the tool during wire bonding. Therefore, by concentrating the Au bumps 50 on both ends of the insulating substrate 30 as in the present embodiment 2, it is possible to suppress the joint from peeling off due to stress generated at the joint of a specific Au bump 50 during wire bonding onto the electrode pad 30c of the insulating substrate 30.

As described above, the optical module 1001 according to the second embodiment includes an optical semiconductor element 10 having electrode pads 10b formed on its surface, an insulating substrate 30 having electrode pads 30c, 30b formed on its front and rear surfaces, and Au bumps 50 that connect the electrode pads 30b on the rear surface of the insulating substrate 30 to the electrode pads 10b of the semiconductor element 10. The rear surface of the insulating substrate 30 is disposed opposite the front surface of the semiconductor element 10, and the electrode pads 30b on the rear surface of the insulating substrate 30 are connected to the electrode pads 30c on the front surface of the insulating substrate 30 via through holes 30d. Since the Au bumps 50 are arranged near one end of the insulating substrate 30 and near the other end opposite to the one end, compared with the case where the Au bumps are arranged evenly on the surface of the insulating substrate and the case where the Au bumps are arranged all around the periphery of the plate, the thermal stress generated during cooling after flip-chip mounting and the stress generated during wire bonding on the electrode pads of the insulating substrate after flip-chip mounting are suppressed from becoming large at the joints of specific Au bumps, causing the joints to peel off, thereby improving the yield and reliability of the optical module. In addition, since it is not necessary to arrange the Au bumps in the center of the insulating substrate, the number of Au bumps required to ensure the reliability of the product can be reduced, and the load required for flip-chip mounting can be reduced. This suppresses the electrode pads on the surface of the insulating substrate from deforming due to friction with the tip of the suction collet caused by ultrasonic vibration and coming into contact with adjacent electrode pads, causing a short circuit. In addition, by reducing the number of required Au bumps, the number of dummy electrode pads that are formed on the optical semiconductor element solely for mechanically fixing the insulating substrate can also be reduced, allowing the optical semiconductor element to be made smaller. This makes it possible to obtain a more reliable optical module that is less expensive and has improved yields.

Embodiment 3.
In the third embodiment, a method for manufacturing the optical semiconductor element 10, the submount 20, and the insulating substrate 30 of the optical module 1001 according to the first embodiment will be described.

Figure 9 is a cross-sectional view showing a manufacturing method of an optical module according to embodiment 3. Note that FIG. 9 illustrates only the manufacturing method of the optical semiconductor element 10, submount 20, and insulating substrate 30 in the optical module 1001 of embodiment 3, and does not illustrate other assembly steps of the optical module 1001, such as the process of fixing the thermo module 40 to the case 100, the process of mounting the assembled optical semiconductor element 10, submount 20, and insulating substrate 30 on the thermo module 40 fixed to the case 100, the process of wire bonding from the electrode pad 30c of the insulating substrate 30 mounted on the thermo module 40 to the IC 110, and the process of mounting the lens 120 and the multiplexer 130 between the laser light generating part formed in the optical semiconductor element 10 and the emission part of the case 100, because they are the same as those of conventional optical modules.

First, as shown in FIG. 9(a), the submount 20 is placed on a hot plate 200 that is heated to 280°C or higher, which is the melting point of the AuSn solder 70, and the AuSn solder 70 that has been pre-coated on the electrode pads 20b of the submount 20 is melted to solder the submount 20 to the optical semiconductor element 10.

At this time, the optical semiconductor element 10 may be placed on the submount 20 after it is confirmed that the AuSn solder 70 has melted, or before the AuSn solder 70 has melted. However, in order to miniaturize the submount 20, it is preferable to pre-coat the AuSn solder 70 so that its dimensions are approximately the same as those of the optical semiconductor element 10. Therefore, if the dimensions of the pre-coated AuSn solder 70 are not larger than those of the optical semiconductor element 10, it is preferable to place the optical semiconductor element 10 after confirming that the AuSn solder 70 has melted. In this third embodiment, the heating temperature of the hot plate 200 is set to 340°C.

Next, as shown in FIG. 9(b), the submount 20 with the optical semiconductor element 10 die-bonded thereto is placed on the stage 300 of an ultrasonic mounting machine. At this time, the stage 300 of the ultrasonic mounting machine is preheated to 200°C, which is a temperature lower than the melting point of the AuSn solder 70, in order to improve the bonding of the Au bumps 50. The submount 20 placed on the stage 300 is vacuumed and adsorbed onto the stage 300, and both sides of the submount 20 in the direction in which ultrasonic vibration is applied are mechanically clamped using jigs 300a and 300b to fix the submount 20 so that it does not move in the direction of ultrasonic vibration.

Furthermore, as shown in FIG. 9(c), Au bumps 50 are formed in advance on the electrode pads 30b of the insulating substrate 30 at positions corresponding to the electrode pads 10b on the optical semiconductor element 10, and the surface on which the electrode pads 30c of the insulating substrate 30 are formed is adsorbed by the adsorption collet 400 of the ultrasonic mounting machine and transported to a predetermined position on the optical semiconductor element 10 preheated to 200°C. The insulating substrate 30 is placed on the optical semiconductor element 10 at a position where the electrode pads 30b on which the Au bumps 50 of the insulating substrate 30 are formed face each other, corresponding to the electrode pads 30b of the optical semiconductor element 10. Note that, although the Au bumps 50 are formed on the electrode pads 30b in this embodiment 3, the Au bumps 50 may be formed in advance on the electrode pads 10b of the optical semiconductor element 10.

Then, as shown in FIG. 9(d), the insulating substrate 30 adsorbed by the adsorption collet 400 is placed on the optical semiconductor element 10 and pressure is applied. At this time, while it is a common process to apply ultrasonic vibrations immediately after pressure application to bond the optical semiconductor element 10 and the Au bumps 50, in this embodiment 3, the adsorption collet 400 is preheated in advance, or the insulating substrate 30 is continuously pressed against the optical semiconductor element 10 via the Au bumps 50, and the Au bumps 50 are also heated to 200°C, which is the same temperature as the optical semiconductor element 10.

Finally, as shown in FIG. 9(e), while the Au bumps 50 are heated to about 200°C, like the optical semiconductor element 10, ultrasonic vibrations are applied by an ultrasonic mounting machine in the direction (direction C) in which the submount 20 is mechanically fixed using jigs 300a and 300b, to ultrasonically bond the optical semiconductor element 10 and the Au bumps 50.

In this way, by heating the Au bumps 50 to the same temperature as the optical semiconductor element 10 and ultrasonically bonding them, good bonding can be obtained with a lower load, lower amplitude, and shorter time than bonding at room temperature, so that the optical semiconductor element 10 can be prevented from being destroyed by ultrasonic waves applied during bonding. In addition, when the assembled optical semiconductor element 10, submount 20, and insulating substrate 30 are removed from the stage 300 of the ultrasonic mounting machine and cooled, the thermal stress generated at the bonding portion of the Au bumps 50 can be reduced compared to when the Au bumps 50 are not heated and bonded at room temperature, so that the bonding portion of the Au bumps 50 is prevented from peeling off due to heating and cooling applied after flip-chip mounting, which causes the optical module 1001 to break. In addition, by die-bonding the optical semiconductor element 10 to the submount 20 in the process prior to flip-chip mounting, it is not necessary to directly mechanically fix the optical semiconductor element 10 during flip-chip mounting, so that the element can be prevented from coming into contact with a fixing jig or the like and being destroyed during flip-chip mounting.

In the third embodiment, the optical semiconductor element 10 is die-bonded to the submount 20, then placed on the stage of an ultrasonic mounting machine, and the insulating substrate 30 is flip-chip mounted with the submount 20 fixed. However, the order in which the optical semiconductor element 10, the submount 20, and the insulating substrate 30 are assembled is not limited to this. For example, the optical semiconductor element 10 may be placed on the stage of an ultrasonic mounting machine, directly fixed, the insulating substrate 30 may be flip-chip mounted, and then the optical semiconductor element 10 with the insulating substrate 30 flip-chip mounted may be die-bonded to the submount 20. However, when the side surface of the optical semiconductor element 10 is mechanically fixed using a jig or the like, it is necessary to set the ultrasonic vibration and the direction of fixing with the jig so that the jig does not touch the laser light generating portion of the optical semiconductor element 10, so that the laser light generating portion of the optical semiconductor element 10 is not destroyed by the ultrasonic vibration applied during flip-chip mounting. For example, if a laser beam generating section is formed on the side of the short side of the optical semiconductor element 10, both long side surfaces of the optical semiconductor element 10 must be fixed with a jig, and the insulating substrate 30 must be flip-chip mounted so that it vibrates relative to the long side of the optical semiconductor element 10 that is fixed with the jig.

When the insulating substrate 30 is flip-chip mounted before the optical semiconductor element 10 is die-bonded to the submount 20, the joints of the Au bumps 50 are subjected to thermal stress due to heating and cooling during die-bonding to the submount 20. However, when the insulating substrate 30 is flip-chip mounted before the optical semiconductor element 10 is die-bonded to the submount 20, the optical semiconductor element 10 can be free from the effects of tilt due to differences in thickness of the AuSn solder 70 pre-coated on the submount 20 and warping due to thermal stress during die-bonding. As a result, ultrasonic waves are applied with only specific Au bumps 50 in contact with the optical semiconductor element 10, which prevents the insulating substrate 30 from rotating during flip-chip mounting and prevents the specific Au bumps 50 from being crushed too much after flip-chip mounting, destroying the optical semiconductor element 10.

As described above, according to the manufacturing method of the optical module 1001 of the third embodiment, the Au bump 50 is provided on the surface of the electrode pad 10b formed on the surface of the optical semiconductor element 10 or on the surface of the electrode pad 30b formed on the back surface of the insulating substrate 30, and includes the steps of placing the insulating substrate 30 on the optical semiconductor element 10 so that the electrode pad 10b of the optical semiconductor element 10 and the electrode pad 30b of the insulating substrate 30 face each other, heating the Au bump 50 while the insulating substrate 30 is placed on the optical semiconductor element 10, and ultrasonically bonding the electrode pad 30b of the insulating substrate 30 or the electrode pad 10b of the optical semiconductor element 10 to the Au bump 50 while applying pressure. This makes it possible to obtain a good bonding state with a lower load, lower amplitude, and in a shorter time than bonding at room temperature, and prevents the optical semiconductor element from being destroyed by the load and amplitude applied during ultrasonic bonding. In addition, when the assembled optical semiconductor element, submount, and insulating substrate are removed from the stage of the ultrasonic mounting machine and cooled, the stress generated at the Au bump joint can be reduced compared to when the optical semiconductor element and the Au bump are bonded under a temperature difference, so that the Au bump joint can be prevented from peeling off due to heating and cooling applied after flip-chip mounting, which would cause the optical module to break. This makes it possible to obtain a highly reliable optical module with improved yield.

Embodiment 4.
In the fourth embodiment, a method for manufacturing the optical semiconductor element 10, the submount 20, and the insulating substrate 30 of the optical module 1001 according to the second embodiment will be described.

Figure 10 is a top view showing a manufacturing method of an optical module according to embodiment 4. The basic manufacturing process of the optical module 1001 in this embodiment 4 is the same as the manufacturing method of the optical module 1001 in embodiment 3, but differs in the flip-chip mounting process of the insulating substrate 30 shown in Figure 10. Therefore, here, the differences will be mainly described, and the same manufacturing processes will not be described. Note that Figure 10 only illustrates the method of flip-chip mounting the insulating substrate 30 to the optical semiconductor element 10 die-bonded to the submount 20 in the optical module 1001 using an ultrasonic mounter, and the other assembly processes are not illustrated or described.

In the third embodiment, the Au bumps 50 are evenly arranged on the surface of the insulating substrate 30, so ultrasonic vibration during flip-chip mounting of the Au bumps 50 can be applied in any direction without any problems. In contrast, in the fourth embodiment, the Au bumps 50 are arranged in a concentrated manner so that they form a row on each of the two sides of the insulating substrate 30, so this embodiment differs from the third embodiment in that ultrasonic vibration is applied in a direction perpendicular to the row of the Au bumps 50.

In the optical module 1001 of the fourth embodiment, the Au bumps 50 are arranged in a row on each of the two sides of the insulating substrate 30. Therefore, when ultrasonic waves are applied in the same direction as the row of the Au bumps 50, the Au bumps 50 arranged at both ends of the row are bonded first, which suppresses the vibration caused by the ultrasonic waves and reduces the bondability of the Au bumps 50 arranged on the inside of the row. As a result, if stress is generated in the joints of the Au bumps 50, there is a concern that the joints of the Au bumps 50 arranged in the center of the row, which have lower bondability compared to the two ends of the row, will peel off, causing the optical module 1001 to break.

Therefore, in the fourth embodiment, as shown in FIG. 10, the Au bumps 50 arranged in a row on each of both ends of the insulating substrate 30 are uniformly and favorably bonded, and ultrasonic waves are applied in a direction perpendicular to the row of the arranged Au bumps 50 (direction D) as a method for ensuring the reliability required for the product when the optical semiconductor element 10 is miniaturized. In this way, all the Au bumps 50 arranged in the direction of vibration by the ultrasonic waves are located at both ends, so that a specific Au bump 50 is bonded first, which can prevent the bondability of the other Au bumps 50 from decreasing, and compared to the case where ultrasonic waves are applied in the same direction as the row of the Au bumps 50, the bonded portions of the Au bumps 50 are prevented from peeling off and the optical module 1001 is damaged, thereby improving the reliability of the product.

In the third embodiment, the order of assembling the optical semiconductor element 10, the submount 20, and the insulating substrate 30 may be to first flip-chip mount the insulating substrate 30 to the optical semiconductor element 10, and then die-bond the optical semiconductor element 10 with the insulating substrate 30 flip-chip mounted to the submount 20. However, in the fourth embodiment, the order of assembling the optical semiconductor element 10, the submount 20, and the insulating substrate 30 is preferably to first die-bond the optical semiconductor element 10 to the submount 20, then place it on the stage of an ultrasonic mounter, and flip-chip mount the insulating substrate 30 with the submount 20 fixed.

For example, when the side of the optical semiconductor element 10 is mechanically fixed using a jig or the like, it is necessary to fix the optical semiconductor element 10 so that it does not move in the direction of ultrasonic vibration by mechanically clamping both sides in the direction of applying ultrasonic vibration. Then, ultrasonic vibration is applied in the direction in which the optical semiconductor element 10 is mechanically fixed, that is, in the fourth embodiment, in the direction perpendicular to the row in which the Au bumps 50 are arranged, to ultrasonically bond the optical semiconductor element 10 and the Au bumps 50. At this time, as shown in the second embodiment, it is preferable that the optical semiconductor element 10 having multiple laser light generating units is arranged such that the electrode pads 10b formed on the optical semiconductor element 10 are arranged in a row relative to the laser light generating units, and one of the rows of Au bumps 50 arranged on the insulating substrate 30 is arranged in a place where it can be bonded to this electrode pad 10b. Therefore, it is preferable that the multiple laser light generating units are formed on the side of the electrode pads 10b of the optical semiconductor element 10, that is, the side perpendicular to the row in which the Au bumps 50 are arranged.

Therefore, if the insulating substrate 30 is flip-chip mounted before the optical semiconductor element 10 is die-bonded to the submount 20, the optical module manufacturing method according to the fourth embodiment requires that the side of the optical semiconductor element 10 on which the laser light generating portion is formed be clamped and fixed with a jig or the like during flip-chip mounting, and there is a concern that the ultrasonic vibration applied during flip-chip mounting may destroy the laser light generating portion of the optical semiconductor element 10.

For the above reasons, in this fourth embodiment, it is preferable to die-bond the optical semiconductor element 10 to the submount 20, place it on the stage of an ultrasonic mounting machine, and mechanically fix the side of the submount 20 in the direction in which the laser light generating portion of the optical semiconductor element 10 is formed with a jig, and then apply ultrasonic vibrations in the direction in which the submount 20 is mechanically fixed, ultrasonically bonding the optical semiconductor element 10 and the Au bumps 50, and flip-chip mounting the insulating substrate 30.

As described above, according to the manufacturing method of the optical module 1001 according to the fourth embodiment, the Au bumps 50 are provided on the surfaces of the electrode pads 10b formed on the surface of the optical semiconductor element 10 or on the surfaces of the electrode pads 30b formed on the back surface of the insulating substrate 30, and the steps include a step of placing the insulating substrate 30 on the optical semiconductor element 10 in a position where the electrode pads 10b of the optical semiconductor element 10 and the electrode pads 30b of the insulating substrate 30 face each other, a step of heating the Au bumps 50 while the insulating substrate 30 is placed on the optical semiconductor element 10, and a step of heating the electrode pads 30b of the insulating substrate 30 or the electrode pads 10b of the optical semiconductor element 10. The method includes a step of ultrasonically bonding the Au bumps 50 and the insulating substrate 30 while applying pressure to the Au bumps 50, and the Au bumps 50 are arranged near one end of the insulating substrate 30 and near the other end opposite to the one end, and ultrasonic vibration is applied in a direction perpendicular to one end of the insulating substrate 30 during ultrasonic bonding, so that a specific Au bump is bonded first with a lower load, a lower amplitude, and a shorter time than bonding at room temperature, and the bondability of the other Au bumps is suppressed from decreasing, and a good bonded state can be obtained for all the arranged Au bumps, and the optical semiconductor element can be prevented from being destroyed by the load and amplitude applied during ultrasonic bonding. In addition, the thermal stress generated at the bonded portion of the Au bumps by heating and cooling the optical module described in the third embodiment can be made smaller than when the optical semiconductor element and the Au bumps are bonded under a temperature difference, so that the effect of preventing the Au bumps from peeling off after flip-chip mounting and the optical module from being destroyed can be obtained. Furthermore, since the number of Au bumps required to ensure the reliability of the product described in the second embodiment can be reduced, it is possible to prevent the electrode pads on the surface of the insulating substrate from deforming due to friction with the tip of the suction collet caused by ultrasonic vibration and coming into contact with adjacent electrode pads, thereby preventing short circuits. It is also possible to reduce the number of dummy electrode pads that are merely used to mechanically fix the insulating substrate formed on the optical semiconductor element, thereby achieving the effect of miniaturizing the dispersive semiconductor element. Therefore, it is possible to obtain a more reliable optical module that is less expensive and has improved yields.

Although various exemplary embodiments and examples are described in this application, the various features, aspects, and functions described in one or more embodiments are not limited to the application of a particular embodiment, but may be applied to the embodiments alone or in various combinations. Thus, countless variations not illustrated are anticipated within the scope of the technology disclosed in this specification. For example, this includes cases in which at least one component is modified, added, or omitted, and even cases in which at least one component is extracted and combined with components of another embodiment.

10 Optical semiconductor element, 10b Electrode pad, 30 Insulating substrate, 30b, 30c Electrode pad, 30d Through hole, 50 Au bump, 1001 Optical module.

Claims (13)

The semiconductor device comprises an InP semiconductor element having an electrode pad formed on a surface thereof, an insulating substrate having electrode pads formed on a surface and a back surface thereof, and a bump for joining the electrode pad on the back surface of the insulating substrate to the electrode pad of the semiconductor element ;
The back surface of the insulating substrate is disposed opposite to the front surface of the semiconductor element,
the electrode pads on the back surface of the insulating substrate are connected to the electrode pads on the front surface of the insulating substrate via through holes ;
an insulating substrate having a surface area on which the electrode pads are formed that is smaller than a surface area on which the electrode pads of the semiconductor element are formed; The semiconductor device comprises an InP semiconductor element having an electrode pad formed on a surface thereof, an insulating substrate having electrode pads formed on a surface and a back surface thereof, and a bump for joining the electrode pad on the back surface of the insulating substrate to the electrode pad of the semiconductor element ;
The back surface of the insulating substrate is disposed opposite to the front surface of the semiconductor element,
the electrode pads on the back surface of the insulating substrate are connected to the electrode pads on the front surface of the insulating substrate via through holes ;
The optical module is characterized in that the bumps are disposed on an edge of one end of the insulating substrate that is connected to an outside, and on an edge of the other end opposite the one end. The optical module according to claim 1, characterized in that the semiconductor element is joined to the surface of the submount via solder. 2. The optical module according to claim 1 , wherein the bumps are evenly arranged within a surface of the insulating substrate. 3. The optical module according to claim 2, wherein the bump disposed on the edge of the other end is a dummy bump. the semiconductor element includes a laser light generating unit,
6. The optical module according to claim 2, wherein the laser light generating portion is provided on a side surface of the semiconductor element located toward the other end opposite to the one end. a step of providing bumps on a surface of an electrode pad formed on a surface of a semiconductor element made of InP or on a surface of an electrode pad formed on a back surface of an insulating substrate, and placing the insulating substrate on the semiconductor element in a position where the electrode pads of the semiconductor element and the electrode pads of the insulating substrate face each other;
heating the bumps while the insulating substrate is placed on the semiconductor element;
a step of ultrasonically bonding the bump to an electrode pad of the insulating substrate or an electrode pad of the semiconductor element while applying pressure;
Including,
2. The method for manufacturing an optical module, wherein the insulating substrate has a surface area on which the electrode pads are formed that is smaller than a surface area on which the electrode pads of the semiconductor element are formed . a step of providing bumps on a surface of an electrode pad formed on a surface of a semiconductor element made of InP or on a surface of an electrode pad formed on a back surface of an insulating substrate, and placing the insulating substrate on the semiconductor element in a position where the electrode pads of the semiconductor element and the electrode pads of the insulating substrate face each other;
heating the bumps while the insulating substrate is placed on the semiconductor element;
a step of ultrasonically bonding the bump to an electrode pad of the insulating substrate or an electrode pad of the semiconductor element while applying pressure;
Including,
A method for manufacturing an optical module , wherein the bumps are disposed on an edge of one end of the insulating substrate that is connected to the outside, and on an edge of the other end opposite the one end. The back surface of the insulating substrate is disposed opposite to the front surface of the semiconductor element,
8. The method for manufacturing an optical module according to claim 7 , wherein the electrode pads on the back surface of the insulating substrate are connected to the electrode pads on the front surface of the insulating substrate via through holes. 10. The method for manufacturing an optical module according to claim 7, wherein the bumps are evenly arranged within a surface of the insulating substrate. 9. The method for manufacturing an optical module according to claim 8 , wherein the bumps arranged on the edge of the other end are dummy bumps. 9. The method for manufacturing an optical module according to claim 8 , wherein, when bonding with ultrasonic waves, the ultrasonic vibration is applied in a direction perpendicular to the one end. the semiconductor element includes a laser light generating unit,
9. The method for manufacturing an optical module according to claim 8 , wherein the laser light generating portion is provided on a side surface of the semiconductor element located toward the other end opposite to the one end.

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