Module and method for manufacturing the same

Abstract

To allow an optical circuit chip to be equipped on a sub wiring board equipped in a main wiring substrate without reducing the connection reliability and without damaging the main wiring substrate.SOLUTION: A sub wiring board 102 is connected on a main wiring board 101 by a ball grid array of a plurality of solder balls 106, 106a, and the solder balls 106a in the region in which an optical circuit chip 103 is equipped is formed of a ball-like core made of Cu and a solder layer surrounding the core covering it.SELECTED DRAWING: Figure 1A

Description

[Technical field]

[0001] The present invention relates to a module equipped with an optical circuit chip and a method for manufacturing the same. [Background technology]

[0002] In recent years, the scope of application of optical communication modules and devices is not limited to long-distance communication, but is also used for links between data centers, between mobile phone base stations, and between edge routers, and there is an increasing demand for improved performance. Optical communication modules are equipped with electrical ICs that process electrical signals, such as digital signal processors (DSPs), drivers, and transimpedance amplifiers (TIAs), as well as optical circuit chips. For example, as shown in Non-Patent Document 1, there is a conventional technology, a module that includes a silicon photonics chip (Fig. 4 Si-Photonic IC) that combines a digital signal processing circuit chip (Fig. 4 XSR, TRX, CDR), a driver, and a transimpedance amplifier.

[0003] In addition, there is a demand for modules to be more economical, and there is a demand for lower costs and improved mass production of optical devices such as optical transmitting and receiving modules such as coherent receivers and multicast optical switches, which are components of modules. As one approach to achieving the economical development of modules, a mounting format in which each chip is integrated on a BGA (Ball Grid Arrays) package has attracted attention (Patent Document 1).

[0004] Here, a module having a general optical transmission and reception function will be described with reference to Fig. 5. The module includes a main wiring board 301, a sub-wiring board 302, an optical circuit chip 303, and an optical fiber 305. The sub-wiring board 302 is connected onto the main wiring board 301. The optical circuit chip 303 is mounted on the sub-wiring board 302. Electronic components (not shown) can also be mounted on the sub-wiring board 302. To connect to the optical fiber 305, the optical circuit chip 303 is mounted on the sub-wiring board 302 with the optical input / output end side protruding from the sub-wiring board 302. The optical fiber 305 is fixed to the end of the optical input / output end side of the optical circuit chip 303 by a fixing part 310.

[0005] The main wiring board 301 is a build-up board whose base material is resin, and can have a multi-layer wiring structure with a thickness of about 1 mm and about 10 layers. Intra-board wiring (not shown) is formed in each layer of the main wiring board 301 and between the layers, and inputs and outputs electrical signals from and to the outside via input / output electrical terminals (not shown). The intra-board wiring can be, for example, copper wiring. The input / output electrical terminals can be, for example, electrodes for a land grid array (LGA), ball grid array (BGA), or other structures.

[0006] Solder balls 306 constituting a BGA are formed on the upper part of main wiring board 301, and provide electrical connection with sub-wiring board 302. Sub-wiring board 302 is generally called an interposer. Sub-wiring board 302 can have a multi-layer wiring structure of about 8 layers with a thickness of about 0.5 mm.

[0007] The optical circuit chip 303 has an optical circuit made of an optical waveguide with a silicon core, and has a thickness of, for example, about 1 mm. The optical circuit chip 303 can also be made of a quartz-based material or a compound semiconductor such as InP. The optical circuit chip 303 is, for example, flip-chip mounted on the sub-wiring board 302 by optical circuit terminals 307 and electrically connected.

[0008] The optical circuit chip 303 can include, for example, an optical transmitter including an optical modulator, an optical waveguide, a splitter, an optical attenuator, etc., and an optical receiver including a photodiode, an optical waveguide, an optical attenuator, etc. For example, a signal from an electronic circuit chip (not shown) is input to the optical transmitter via at least the sub-wiring board 302, and a received signal from the optical receiver is output to a transimpedance amplifier circuit (TIA) of the electronic circuit chip.

[0009] A traveling-wave electrode type Mach-Zehnder modulator (MZM) is often used for the optical transmitter of the optical circuit chip 303. The transmission signal input terminal group, reception signal output terminal group, and MZM electrodes (optical circuit terminals 307) of the optical circuit chip 303 mounted face-down on the sub-wiring board 302 by flip-chip are arranged on the lower surface of the optical circuit chip 303 (the surface facing the sub-wiring board 302).

[0010] The electronic circuit chip is equipped with a digital signal processing circuit (DSP), a driver circuit (DRV), and a transimpedance amplifier circuit (TIA). The DRV amplifies the transmission signal output from the digital signal processing circuit, and the TIA amplifies the reception signal output from the optical circuit, and each has the function of connecting to the digital signal processing circuit.

[0011] The electronic components are a group of components necessary for driving the optical circuit chip 303, and may be capacitors, inductors, resistors, etc. The electronic components may also be a control microcomputer, an AD converter, a DA converter, an electric switch, etc. [Prior art documents] [Patent documents]

[0012] [Patent Document 1] JP 2019-215405 A [Non-patent literature]

[0013] [Non-Patent Document 1] R. Mahajan et al., "Co-Packaged Photonics For High Performance Computing: Status, Challenges And Opportunities", Journal of Lightwave Technology, vol. 40, no. 2, pp. 379-392, 2022. Summary of the Invention [Problem to be solved by the invention]

[0014] Generally, when manufacturing a substrate with a chip mounted thereon, the chip is first mounted on a large substrate, and then the large substrate is divided into individual pieces to obtain the substrate with the chip mounted thereon. However, when mounting an optical circuit chip on a wiring substrate, it is necessary to connect an optical fiber and a fixed component, which will be described later, to the optical circuit chip, so that the optical circuit chip is mounted so as to protrude from the outer periphery of the wiring substrate. Therefore, it is difficult to adopt the conventional method.

[0015] Furthermore, even in a conventional method of producing a sub-wiring board (interposer) equipped with an optical circuit chip by cutting a substrate equipped with an optical circuit chip into individual pieces, the cutting process requires an additional step of forming grooves in the substrate beforehand, and also requires providing extra areas such as areas for forming slits in the substrate before cutting, complicating the assembly process. In order to avoid this complexity, a manufacturing method can be considered in which the individualized sub-wiring board is mounted on the main wiring substrate, and then the optical circuit chip is mounted on the sub-wiring board.

[0016] However, in this manufacturing method, when mounting the optical circuit chip on the sub-wiring board using an existing flip-chip mounting device, the heating from the underside of the sub-wiring board is insufficient, which causes a problem of reduced connection reliability of the optical circuit chip. On the other hand, if the heating temperature during mounting is excessively high, there is a risk of damage to the main wiring board.

[0017] The present invention has been made to solve the above-mentioned problems, and has an object to enable an optical circuit chip to be mounted on a sub-wiring board mounted on a main wiring board without damaging the main wiring board and without reducing connection reliability. [Means for solving the problem]

[0018] The module of the present invention comprises a main wiring board, a sub-wiring board connected onto the main wiring board by solder balls, an optical circuit chip mounted on the sub-wiring board, an optical fiber optically connected to an optical input / output end on a side end face of the optical circuit chip, and a fixing part for fixing the optical fiber to the optical input / output end, and the solder ball in the area where the optical circuit chip is mounted is composed of a ball-shaped core made of Cu and a solder layer surrounding the core.

[0019] The manufacturing method of the module according to the present invention includes the steps of connecting an optical circuit chip onto a sub-wiring board by thermocompression bonding and connecting an optical fiber to an optical input / output terminal on a side end face of the optical circuit chip via a fixing part, and the solder ball in the area where the optical circuit chip is mounted is composed of a ball-shaped core made of Cu and a solder layer surrounding the core. Effect of the Invention

[0020] As described above, according to the present invention, the solder ball in the area where the optical circuit chip is mounted is composed of a ball-shaped core made of Cu and a solder layer surrounding the core, so that the optical circuit chip can be mounted on the sub-wiring board mounted on the main wiring board without damaging the main wiring board and without reducing the connection reliability. [Brief description of the drawings]

[0021] [Figure 1A] FIG. 1A is a configuration diagram showing the configuration of a module according to an embodiment of the present invention. [Figure 1B] FIG. 1B is a plan view showing a partial configuration of a module according to an embodiment of the present invention. [Diagram 2]FIG. 2 is a cross-sectional view showing the configuration of the solder ball 106a. [Diagram 3] FIG. 3 is a configuration diagram showing the configuration of another module according to an embodiment of the present invention. [Figure 4A] FIG. 4A is a cross-sectional view showing a state of a module in the middle of a process, illustrating a method for manufacturing a module according to an embodiment of the present invention. [Figure 4B] FIG. 4B is a cross-sectional view showing a state of the module in the middle of a process, illustrating a method for manufacturing a module according to an embodiment of the present invention. [Figure 4C] FIG. 4C is a cross-sectional view showing a state of the module in the middle of a process, illustrating a method for manufacturing a module according to an embodiment of the present invention. [Figure 4D] FIG. 4D is a cross-sectional view showing a state of the module in the middle of a process, illustrating a method for manufacturing a module according to an embodiment of the present invention. [Diagram 5] FIG. 5 is a diagram showing the configuration of a conventional module. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] A module according to an embodiment of the present invention will be described below with reference to Figures 1A and 1B. This module includes a main wiring board 101, a sub-wiring board 102, an optical circuit chip 103, electronic components 104, and an optical fiber 105. Although not shown, an optical connector such as an MPO (Multi-Fiber Push On) connector is connected to the tip of the optical fiber 105.

[0023] The sub-wiring board 102 is connected to the main wiring board 101 by a ball grid array made of multiple solder balls 106, 106a. In addition, the optical circuit chip 103 is mounted on the sub-wiring board 102. Electronic components 104 can also be mounted on the sub-wiring board 102. The optical circuit chip 103 is mounted on the sub-wiring board 102 with the optical input / output terminal 131 side protruding from the sub-wiring board 102.

[0024] The main wiring board 101 is a build-up board whose base material is resin, and can have a multi-layer wiring structure with a thickness of about 1 mm and about 10 layers. In-board wiring (not shown) is formed in each layer of the main wiring board 101 and between the layers, and input and output of electrical signals can be performed with the outside via input and output electrical terminals (not shown). The in-board wiring can be, for example, copper wiring. The input and output electrical terminals can be, for example, electrodes for a land grid array (LGA), ball grid array (BGA), or other structures.

[0025] Solder balls 106, 106a are formed on the upper part of main wiring board 101, and provide electrical connection with sub-wiring board 102. Sub-wiring board 102 is generally called an interposer. Sub-wiring board 102 can have a multi-layer wiring structure with a thickness of about 0.5 mm and about eight layers.

[0026] The optical circuit chip 103 has an optical circuit made of an optical waveguide with a silicon core, and has a thickness of, for example, about 1 mm. The optical circuit chip 103 can also be made of a quartz-based material or a compound semiconductor such as InP. The optical circuit chip 103 is, for example, flip-chip mounted on the sub-wiring board 102 by optical circuit terminals 107 and electrically connected.

[0027] The optical circuit chip 103 can include, for example, an optical transmitter including an optical modulator, an optical waveguide, a splitter, an optical attenuator, etc., and an optical receiver including a photodiode, an optical waveguide, an optical attenuator, etc. For example, a signal from an electronic circuit chip (not shown) is input to the optical transmitter via at least the sub-wiring board 102, and a received signal from the optical receiver is output to the TIA of the electronic circuit chip.

[0028] A traveling-wave electrode Mach-Zehnder modulator (MZM) is often used for the optical transmitter of the optical circuit chip 103. The transmission signal input terminal group, reception signal output terminal group, and MZM electrodes (optical circuit terminals 107) of the optical circuit chip 103 mounted face-down on the sub-wiring substrate 102 by flip-chip are disposed on the lower surface of the optical circuit chip 103 (the surface facing the sub-wiring substrate 102).

[0029] The electronic components 104 are a group of components necessary for driving the optical circuit chip 103, and may be capacitors, inductors, resistors, etc. The electronic components 104 may be a control microcomputer, an AD converter, a DA converter, an electric switch, etc. In the first embodiment, the electronic components 104 are mainly mounted (implemented) on the main wiring board 101 or the sub-wiring board 102 on the optical input / output terminal 131 side of the optical circuit chip 103.

[0030] The optical fiber 105 is connected to the optical circuit chip 103 for optical input / output. The optical fiber 105 can be an array of multiple optical fibers. In the case of 400GBASE-DR4, a minimum of eight optical fibers 105 are required: four for transmission and four for reception. Furthermore, when continuous light for optical transmission is supplied from an external source, at least one optical fiber is added to these. For ease of handling, the optical fibers 105 arranged as an array of multiple optical fibers are usually fixed to each other with adhesive or coating using a method called taping or ribbonizing.

[0031] The optical fiber 105 is fixed to one end of the optical circuit chip 103 by a fixing part 110. In order to connect the optical fiber 105 to an optical waveguide formed in a position close to the bottom surface of the optical circuit chip 103, the fixing part 110 protrudes downward from the bottom surface of the optical circuit chip 103. In order to prevent interference (contact) between the lower part of the fixing part 110 protruding downward and the sub-wiring board 102, the optical input / output terminal 131 to which the fixing part 110 of the optical circuit chip 103 is fixed protrudes outside the sub-wiring board 102 in a plan view. However, since the optical circuit chip 103 is mounted on the sub-wiring board 102, for example, even in a configuration in which the optical circuit chip 103 is disposed in the center of the main wiring board 101, there is no interference between the lower part of the fixing part 110 and the main wiring board 101.

[0032] The fixing part 110 is made of glass, which is a different material from the material of the optical fiber 105, and serves to increase the connection strength between the optical fiber 105 and the optical circuit chip 103. The optical fiber 105 and the fixing part 110 are connected to the center of the end face of the optical circuit chip 103 using an optically transparent adhesive.

[0033] According to this embodiment, since the optical circuit chip 103 is mounted on the sub-wiring board 102, the lower end of the fixing part 110 can be positioned away from the surface of the main wiring board 101. This allows for greater freedom in the arrangement of the optical circuit chip 103 on the main wiring board 101.

[0034] In addition, a reinforcing part 111 can be further provided to reinforce the fixing part 110 provided on the protruding part of the optical circuit chip 103. The reinforcing part 111 can be attached to the back surface of the optical circuit chip 103 and the side surface of the fixing part 110 to be fixed.

[0035] In the embodiment, the solder ball 106a provided in the region where the optical circuit chip 103 is mounted in plan view is a covered ball composed of a ball-shaped core 161 made of Cu and a solder layer 162 surrounding the core 161, as shown in FIG. 2. More specifically, when the module shown in FIG. 1A is viewed from the optical circuit chip 103 side, the solder ball 106 provided in the region where the optical circuit chip 103 and the sub-wiring board 102 overlap is a covered ball composed of a ball-shaped core 161 made of Cu and a solder layer 162 surrounding the core 161. Also, the solder ball 106a arranged in the region where the optical circuit terminal 107 of the optical circuit chip is provided in plan view may be a covered ball composed of a ball-shaped core 161 made of Cu and a solder layer 162 surrounding the core 161, as shown in FIG. 2. Note that the solder ball 106a can be used in all regions, as shown in FIG. 3.

[0036] Here, a method for fabricating a module according to an embodiment will be briefly described. First, as shown in Fig. 4A, a sub-wiring substrate 102 is prepared, and solder balls 106 are mounted (placed) on the underside of the sub-wiring substrate 102 in an area that does not overlap with an area where the optical circuit chip 103 is mounted. The mounting method may be a printing method, a ball transfer method, a ball mounting method, or the like (first step).

[0037] Next, solder balls 106a are mounted on the underside of sub-wiring substrate 102 in an area overlapping with the mounting area of ​​optical circuit chip 103. The mounting method used is a ball mounting method or other mounting method that does not interfere with solder balls 106 already mounted (second step). Note that solder balls 106 can also be mounted after solder balls 106a are mounted.

[0038] 4B, sub-wiring board 102 is mounted on main wiring board 101 by BGA using solder balls 106, 106a. The mounting method may be thermocompression bonding, mass reflow, or the like (third step).

[0039] 4C and 4D, the optical circuit chip 103 is mounted on the sub-wiring substrate 102 so that the optical input / output terminal 131 of the optical circuit chip 103 protrudes from the sub-wiring substrate 102. For example, the above-mentioned mounting of the optical circuit chip 103 can be performed by heating from the side of the main wiring substrate 101. More specifically, using a flip-chip mounting device or the like, the main substrate 101 is placed on a heater stage 151, and the optical circuit chip 103 is placed on the sub-wiring substrate 102 using a bonding head 152.

[0040] In this state, heater stage 151 is operated to heat the main substrate 101 from the side opposite to the side on which sub-wiring substrate 102 is mounted. The heat generated by the heating quickly reaches sub-wiring substrate 102 via core 161, which has high thermal conductivity, and the optical circuit chip 103 and sub-wiring substrate 102 can be connected. In this mounting, thermocompression bonding can also be used in which bonding head 152 is used to press optical circuit chip 103 against sub-wiring substrate 102 and heat it at the same time (fourth step).

[0041] Next, an optically transparent adhesive is used to connect and fix the optical fiber 105 and the fixed component 110 to the center of the end face of the optical circuit chip 103 (fifth step). Note that the solder balls 106, 106a may be mounted on the sub-wiring substrate 102 while the substrate is in a state prior to being singulated into the sub-wiring substrates 102, and the substrate may be singulated to form the sub-wiring substrates 102 after the solder balls 106, 106a are mounted.

[0042] By using the solder balls 106a as described above, when the optical circuit chip 103 is mounted on the sub-wiring board 102 using a flip-chip mounting device, heat applied from the lower surface side of the main wiring board 101 is transferred to the sub-wiring board 102 via the cores 161, which have high thermal conductivity. As a result, the optical circuit chip 103 can be mounted in a highly reliable state while minimizing the heating of the main wiring board 101.

[0043] As described above, according to the present invention, the solder balls in the region where the optical circuit chip is mounted are composed of a ball-shaped core made of Cu and a solder layer surrounding the core, so that the optical circuit chip can be mounted on the sub-wiring board mounted on the main wiring board without damaging the main wiring board and without reducing the connection reliability. Similar effects can be expected when pins made of Cu are used instead of the solder balls in the region where the optical circuit chip is mounted.

[0044] It should be noted that the present invention is not limited to the above-described embodiments, and it is apparent that many modifications and combinations can be made by a person having ordinary knowledge in the art within the technical concept of the present invention. [Explanation of symbols]

[0045] 101...main wiring board, 102...sub-wiring board, 103...optical circuit chip, 104...electronic component, 105...optical fiber, 106...solder ball, 106a...solder ball, 107...optical circuit terminal, 110...fixed component, 131...optical input / output terminal.

Claims

1. A main wiring board; a sub-wiring board connected to the main wiring board by solder balls; an optical circuit chip mounted on the sub-wiring board; an optical fiber optically connected to an optical input / output end of a side end surface of the optical circuit chip; a fixing part for fixing the optical fiber to the optical input / output end; Equipped with The solder ball in the region where the optical circuit chip is mounted is composed of a ball-shaped core made of Cu and a solder layer surrounding the core. Module.

2. 2. The module of claim 1, The optical circuit chip is a module mounted on the sub-wiring substrate such that the optical input / output terminal side protrudes from the sub-wiring substrate.

3. 2. The module of claim 1, The module further comprises a reinforcing part for reinforcing the fixed part provided on the protruding portion of the optical circuit chip.

4. a step of connecting a sub-wiring board to a main wiring board by solder balls; a step of connecting an optical circuit chip onto the sub-wiring board by a thermocompression bonding method; a step of connecting an optical fiber to an optical input / output end of the side end surface of the optical circuit chip via a fixing part; Equipped with The solder ball in the region where the optical circuit chip is mounted is composed of a ball-shaped core made of Cu and a solder layer surrounding the core. How the module is manufactured.

5. 5. The method for manufacturing a module according to claim 4, A method of manufacturing a module, in which, in the step of connecting the optical circuit chip onto the sub-wiring board by a thermocompression bonding method, the main wiring board is heated from the side opposite to the side to which the sub-wiring board is connected.

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