Optical module

Abstract

To solve the problem in which in a prior art optical module, an adhesive protruding around a TIA mounted with a spacer reduces product yield and increases cost for an inspection process.SOLUTION: An optical module of the present disclosure comprises an optical circuit and one or more electronic circuit chips, and one electronic circuit chip is bonded to a lid of the optical module by using an adhesive with a spacer therebetween. The spacer has edges extending toward adjacent components on a side of the lid in a thickness direction, and has a surface having a wide width exceeding the size of the electronic circuit chip. The lid has recesses for storing an excess adhesive at positions substantially matching the extending edges on an adhesive surface to the spacer. The excess adhesive between the spacer and the lid is guided into the recesses, thereby preventing contact of the adhesive with the adjacent components.SELECTED DRAWING: Figure 4

Description

[Background technology]

[0001] The present invention relates to an optical module, and more particularly to a structure for controlling an adhesive in an optical module.

[0002] With the increasing number of services via optical communication networks, the development of devices that densely integrate a large number of optical functional elements is progressing. For optical transmission devices, specifications have been defined for removable digital coherent transceivers (hereafter referred to as transceivers for simplicity), which are capable of processing optical signals of multiple channels. The power consumption and size of transceivers are determined by standardization organizations such as the Optical Internetworking Forum (OIF). In order to meet the demands for faster transceiver operation, higher capacity, smaller size, and lower power consumption, the development of optical transmitting and receiving modules with new configurations that utilize silicon photonics technology is progressing.

[0003] FIG. 1 is a diagram showing the configuration of an optical transceiver module including a silicon chip. FIG. 1(a) is a top view (xy plane) of the chip mounting surface of the optical transceiver module 20 with the lid removed. The optical transceiver module 20 receives an optical signal that has been modulated in a predetermined manner, outputs an electrical baseband signal, and generates and outputs modulated light using the electrical baseband signal. The optical transceiver module is mounted on the transceiver based on the OIF described above, and has an interface with one or more optical fibers (not shown) and an electrical signal. In the following explanation, the optical transceiver module is simply called an optical module.

[0004] In the optical module 20, a silicon photonics (SiP) chip 2 and electronic components for optical-electrical conversion and external interface are integrated on a package (substrate) 1. The SiP chip 2 integrates optical functions of an optical receiver and an optical modulator, such as a polarization splitter, a coherent mixer, a plurality of photodetectors (PDs), a polarization rotator, a polarization combiner, and an optical modulator, on a single chip on a Si substrate. The electronic components include a driver IC 3 for driving a modulated signal and transimpedance amplifiers (TIA) 4a and 4b for converting a current output from the PD into a voltage signal. Other electronic components such as chip capacitors 5-1a to 5-2b are also mounted. For example, in the TIA 4a, bypass chip capacitors may be arranged as capacitor groups 5-1a and 5-2a on each of the DC lines in correspondence with the four signal lines included in the TIA chip.

[0005] FIG. 1B shows a lid 8 that covers the entire optical module 20. As shown in FIG. 1A, the SiP chip 2 has the largest size in both area and height in the optical module 20. The driver IC 3 is smaller than the SiP chip 2, and the TIAs 4a and 4b have the smallest size. In the optical module 20, the lid 8 is mounted so as to cover the entire package in order to protect the components mounted inside and to dissipate heat generated by the components to the outside. As shown in FIG. 1B, the outer shape of the lid 8 corresponds to the outer shape of the package 1. The dotted line area 8a is formed by carving into the inside of the lid, as described later, and indicates a shallow adhesive surface that houses the driver IC 3 and the TIA 4. The dotted line area 8b is formed by carving more deeply than the shallow adhesive surface and indicates a deep adhesive surface that houses the SiP chip 2. The component arrangement and adhesive surface area shown in FIG. 1 are exemplary.

[0006] FIG. 2 is a diagram showing the cross-sectional structure of an optical module including a TIA and cut perpendicular to the substrate surface. The cross section (yz plane) shown in FIG. 1 includes the line II-II passing through the driver IC 3 and the TIA 4a with the lid 8 mounted, and is cut perpendicular to the substrate surface. The optical module 20 is mounted on the transceiver by a ball grid array (BGA) 9. The lid 8 has two different depths on one plate-like surface made of a material such as aluminum. A space 21 is formed by the deep adhesive surface in the area corresponding to the highest SiP chip 2 and the shallow adhesive surface 22 shown in FIG. 2 that houses the lower driver IC 3 and TIA 4. The two adhesive surfaces with different heights partition a space that houses the chips, ICs, and electronic components mounted on the surface of the package 1. As long as the internal components are protected and heat is dissipated, the shape of the space 21 formed by the adhesive surface may be arbitrary depending on the component arrangement on the package 1.

[0007] Although it is possible to form three adhesive surfaces on the lid with corresponding depths for the three types of chips with different heights, there are limitations to the processing accuracy of the adhesive surfaces and the assembly accuracy, so adhesive surfaces with two different depths are formed. Referring to the cross-sectional view of Figure 2, the driver IC 3 is directly fixed to the adhesive surface 22 of the lid 8 with an adhesive, while the thinner TIA 4 is fixed to the adhesive surface 22 with an adhesive via the spacer 7.

[0008] Figure 3 is an enlarged view of the optical module cross-sectional structure perpendicular to the substrate surface, showing the TIA periphery. Region III in Figure 2 is enlarged, and the lid 8 and part of the package 1 are cut away to show the TIA 4. Since the TIA 4 is very thin compared to the other two chips, a spacer 7 is inserted between the TIA 4 and the adhesive surface 22 of the lid to adjust its height. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] JP 2001-230274 A [Patent Document 2] JP 2012-146363 A [Patent Document 3] JP 2015-204356 A [Non-patent literature]

[0010] [Non-Patent Document 1] OIF, Implementation Agreement for the High Bandwidth Coherent Driver Modulator (HB-CDM), [online], July 15, 2021, [Retrieved March 20, 2023], Internet<URL: https: / / www.oiforum.com / wp-content / uploads / OIF-HB-CDM-02.0.pdf> Summary of the Invention [Problem to be solved by the invention]

[0011] However, when fixing the TIA and the lid via a spacer, it is difficult to control the adhesive between the spacer and the adhesive surface, and there is a problem that the adhesive overflows around the spacer. The spacer 7 is made of a highly heat-conductive material such as aluminum nitride, and dissipates heat to the adhesive surface 22 via a highly heat-conductive conductive adhesive, and functions as a heat sink together with the lid 8. The element that generates the most heat in the optical module is the driver IC 3, and it is necessary to bring the driver IC 3 into close contact with the adhesive surface 22 to dissipate heat efficiently to the lid 8. Therefore, when mounting the lid 8 on the optical module, the driver IC 3 and the adhesive surface 22 are fixed with an optimal amount of adhesive. In the assembly process, the height position of the lid 8 relative to the package 1 is determined by the driver IC 3 and the adhesive surface 22.

[0012] Although the amount of heat generated by the TIA 4 is less than that of the driver IC, sufficient heat dissipation is also required for the TIA 4. First, the spacer 7 and the TIA 4 are bonded with adhesive 12, and then the lid 8 is mounted on the driver IC 3, and at the same time, the top surface of the spacer 7 and the adhesive surface 22 are fixed with adhesive 11. When assembling the optical module 20, the cumulative error in the height direction (z direction) of the BGA 10 height, the thicknesses of the two adhesive layers above and below, the TIA, and the spacer thickness must be taken into consideration. Taking into account the variation in the cumulative error, the distance between the lid 8 and the adhesive surface 22 is set wider than the distance between the driver IC 3 and the adhesive surface 22.

[0013] In the optical module, a conductive adhesive with high thermal conductivity is used that has a fairly high viscosity. Specifically, the viscosity of the adhesive used is 8 to 350 Pa·s (23°C). Since the viscosity of the adhesive is high, it is difficult to control the amount of adhesive applied onto the bonding surface, and the amount of adhesive applied may vary. In order to ensure heat dissipation, the adhesive needs to spread over a certain percentage (e.g., 80%) or more of the bonding area. Even if the gap between the spacer 7 and the lid bonding surface 22 is biased toward the wider side during the process of mounting the lid 8, a sufficient amount of adhesive is applied so that the adhesive overflows from the bonding surface (100% or more). It is necessary to reliably fill the gap between the spacer 7 and the bonding surface 22 of the lid 8 with adhesive, and the amount of adhesive must be set to be large.

[0014] Since the spacer 7 is slightly smaller than the external area (xy plane) of the TIA, the excess adhesive 12 on the lower surface of the spacer 7 remains around the spacer on the upper surface of the TIA. Meanwhile, the excess adhesive 11 on the upper surface of the spacer 7 protrudes around the spacer 7 along the adhesive surface 22. If the distance between the spacer 7 and the adhesive surface 22 becomes narrower and the amount of adhesive is biased to the larger side due to the accumulated error during assembly described above, the amount of adhesive 12 that protrudes increases. In this state, there is a possibility that contact points 13 will occur between the electrodes of the chip capacitor 5a arranged around the TIA 4 and the adhesive 12. If the electrodes of the chip capacitor 5a come into contact with the adhesive 12, the adhesive is conductive and may induce a short circuit of the chip capacitor 5a.

[0015] As shown in Figures 1 and 3, the TIA 4 performs current-voltage conversion of the differential current signal (I signal, Q signal) from the PD on the SiP chip, and a chip capacitor is provided as a bypass capacitor. An X-ray inspection process is essential to detect contact between the adhesive 12 that protrudes from the top surface of the spacer 7 and adjacent components. In optical modules of the prior art, contact between the adhesive that protrudes around the TIA mounted via the spacer and electronic components causes problems such as reduced product yield and high costs of the inspection process.

[0016] The present invention has been made in consideration of such problems, and its purpose is to control the adhesive used in an optical module to improve the yield of optical modules and reduce manufacturing costs. [Means for solving the problem]

[0017] One embodiment of the present invention is an optical module comprising a package, an optical circuit mounted in the package, one or more electronic circuits mounted in the package, and a lid covering the optical circuit and the one or more electronic circuits, wherein one chip of the one or more electronic circuits is fixed to an adhesive surface of the lid in the thickness direction in the following order: a first adhesive layer, a spacer, and a second adhesive layer, the spacer having a first surface on the lid side having a width wider than the width of the chip, and a second surface having a width narrower than the first surface, and the lid has a recess continuing from the adhesive surface in an area including an edge of the spacer extending in the width direction of the first surface for storing adhesive of the second adhesive layer. Effect of the Invention

[0018] According to the present invention, it is possible to improve the yield and provide a low-cost optical module. [Brief description of the drawings]

[0019] [Figure 1]FIG. 1 is a diagram showing a configuration of an optical transceiver module including a silicon chip. [Diagram 2] FIG. 1 is a cross-sectional view of an optical module including a TIA, cut perpendicular to a substrate surface. [Diagram 3] FIG. 1 is an enlarged cross-section of an optical module perpendicular to the substrate surface, showing the TIA periphery. [Figure 4] 1 is an enlarged view showing a cross-sectional structure around a TIA of an optical module according to the present disclosure. [Diagram 5] FIG. 2 is a perspective view of a spacer in the optical module of the present disclosure, as viewed from the TIA side. [Figure 6] 13 is a diagram showing the positional relationship between the TIA and a recess formed on the lid bonding surface. FIG. [Figure 7] 1A to 1C are diagrams illustrating a manufacturing process of a spacer for an optical module according to the present disclosure. [Figure 8] 1A and 1B are diagrams illustrating the relationship between the spacer shape and a recess in the optical module according to the present disclosure. [Figure 9] 13 is a diagram showing a cross-sectional structure around a TIA of an optical module according to a second embodiment. FIG. [Figure 10] 13 is a diagram showing a cross-sectional structure around a TIA of an optical module according to a third embodiment. FIG. [Figure 11] 13 is a diagram showing a cross-sectional structure around a TIA of an optical module according to a fourth embodiment. FIG. [Figure 12] 13 is a diagram showing a cross-sectional structure around a TIA of an optical module according to a fifth embodiment. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] The optical module of the present disclosure includes an optical circuit and one or more electronic circuit chips, and one electronic circuit chip is bonded to the lid of the optical module by adhesive via a spacer. The spacer has an edge extending toward an adjacent component on the lid side in the thickness direction, and has a wide surface exceeding the size of the electronic circuit chip. Furthermore, the lid has a recess for storing excess adhesive at a position roughly corresponding to the extended edge of the bonding surface with the spacer. Excess adhesive between the spacer and the bonding surface of the lid is guided into the recess of the lid, preventing the adhesive from coming into contact with the adjacent component. Hereinafter, the structure of the optical module of the present disclosure, the effect of improving the manufacturing process, and various embodiments will be described.

[0021] [Embodiment 1] 4 is a diagram showing an enlarged cross-sectional structure of the TIA periphery of the optical module of the present disclosure, taken perpendicular to the substrate surface. The optical module 100 of the first embodiment having a typical configuration is characterized by a structure in which the TIA 4 and the lid 8 are fixed via a spacer 101, and the overall configuration of the optical module and the internal component configuration and arrangement are the same as those of the conventional optical module described with reference to FIGS.

[0022] As an example, the optical module 100 is also assumed to have the SiP chip 2, driver IC 3, and TIAs 4a and 4b mounted on a package 1 in the component arrangement shown in FIG. 1, and details will be omitted. Adjacent electronic components such as chip capacitors are also arranged around the TIA. The optical module 100 is mounted with a lid 8 so as to cover the entire package and internal components. Also, as shown in FIG. 2, when looking at a cross section (yz plane) passing through the driver IC 3 and the TIA 4, the driver IC 3 is directly bonded to the bonding surface 22 of the lid 8. The TIA 4 is fixed to the bonding surface 22 of the lid 8 via a spacer 101 sandwiched between two upper and lower adhesive layers, the first adhesive layer 12 and the second adhesive layer 11, as in the configuration of FIG. 3. On the other hand, the spacer 101 has a different shape from the spacer 7 in the conventional technology. The following will focus on the structure around the TIA, which is different from the optical module of the conventional technology, and will be described.

[0023] The TIA 4 is fixed to the adhesive surface 22 of the lid 8 via a spacer 101 sandwiched between two adhesive layers above and below, similar to the configuration in FIG.

[0024] 4 again, in the optical module 100, the spacer 101 fixed on the TIA 4 by the adhesive 12 has an edge extending toward the side where the chip capacitors 5a, 5b adjacent to the TIA are located, and has a T-shaped cross section when viewed in a cross section (yz plane) including adjacent components. The spacer 7 of the prior art shown in FIG. 3 has a simple rectangular cross section, whereas in the optical module 100 of the present disclosure, the portion of the spacer 101 on the lid 8 side in the thickness direction (z axis) extends beyond the area of ​​the TIA 4 toward the side of the adjacent components 5a, 5b (y axis direction). The portion of the spacer 101 on the TIA 4 side in the thickness direction (z axis) is located inside the area of ​​the outer shape of the TIA 4, as in the configuration of the prior art.

[0025] Therefore, when the spacer 101 is viewed in a cross section including the adjacent components, it can be seen as having an edge extending toward the adjacent components on the lid side in the height direction. Due to the existence of this extended edge, the spacer has a width exceeding the width of the TIA4. When the spacer 101 is viewed in a cross section including the adjacent electronic components, it can also be seen as having a "first surface" on the lid side that is wider than the TIA, and a "second surface" on the TIA side that is narrower than the first surface. A manufacturing method of the spacer, a more detailed configuration, and modified examples will be described later with reference to Figures 7 and 8. When viewed in a cross section including the adjacent components, the wider part of the spacer 101 on the lid side is called the extension part, and the narrower part of the spacer 101 on the TIA side is called the base part. The extension part and the base part may be integral or may be separate parts.

[0026] In addition to the spacer 101 having the above-mentioned extended edge, the optical module 100 has groove-shaped recesses 102-1 and 102-2 on the adhesive surface 22 of the lid 8 at positions that include the extended edge of the spacer. The extended edge of the spacer 101 guides the excess adhesive 11 between the adhesive surface 22 and the spacer 101 along the upper surface of the spacer 101 into the recesses 102-1 and 102-2. Therefore, the overflowing adhesive 11 does not come into contact with the adjacent chip capacitors 5a and 5b. It is possible to prevent the adhesive from overflowing from the lid side of the spacer toward adjacent components without being affected by variations in the amount of adhesive or accumulated errors during assembly of the optical module.

[0027] Fig. 4 is an enlarged view of the periphery of TIA 4a in a cross section taken along line II-II in the optical module with the exemplary component arrangement shown in Fig. 1. A cross section taken along a line perpendicular to line II-II and passing through another TIA 4b in Fig. 1 is similar to Fig. 4. Therefore, it should be noted that in the optical module 100 of the present disclosure, the shape of the spacer can be flexibly modified according to the positional relationship of adjacent components with respect to an electronic component chip (e.g., a TIA) connected via the spacer.

[0028] Fig. 5 is a perspective view of a spacer in an optical module of the present disclosure, seen from the TIA side. Fig. 5(a) shows the spacer 101-1, whose cross section is T-shaped as shown in Fig. 4, together with the adjacent chip capacitor groups 5-1 and 5-2. The spacer 101-1 has edges extending toward the adjacent components on the upper side of the drawing, which will be bonded to the lid, on the two sides where the adjacent chip capacitors are arranged. That is, when viewed in a cross section (yz plane) including the adjacent chip capacitor groups, the spacer 101-1 has a wide first surface 103-1 and a second surface 103-2 narrower than the first surface.

[0029] As described in FIG. 4, the edge of the spacer 101 extending toward the adjacent components functions to prevent excess adhesive from spilling out from the lid side. The configuration of the spacer is not limited to the case where adjacent components 5-1a, 5-2a are arranged on two sides of the TIA 4 as illustrated in FIG. 1. For example, when adjacent components are arranged on the four sides around the TIA, the spacer 101-2 shown in FIG. 5(b) may have edges extending toward the adjacent components on the four sides where the chip capacitor groups 5-1 to 5-4 are located. That is, the spacer 101-2 has edges extending toward the adjacent components around the entire periphery.

[0030] FIG. 6 is a diagram showing the positional relationship between the TIA and the recess formed on the adhesive surface of the lid. FIG. 6 is a perspective view of the top surface (xy plane) of the optical module with the lid mounted, where the dotted line 4 indicates the outer shape of the TIA, and the two-dot chain lines 5-1 to 5-4 indicate the positions of the chip capacitor group adjacent to the TIA. Furthermore, the hatched areas 102-1 and 102-2 indicate the recess formed on the lid. FIG. 6(a) corresponds to the case of the spacer 101-1 in FIG. 5(a) in which adjacent components are arranged along two sides of the TIA 4. The recess is formed as two grooves 102-1 and 102-2 formed on the adhesive surface 22 of the lid 8. FIG. 6(b) corresponds to the case of the spacer 101-2 in FIG. 5(b) in which adjacent components are arranged along the four sides of the entire circumference of the TIA 4. In this case, the recess is a rectangular groove 102 formed on the adhesive surface 22 of the lid 8 and coincides with the outer circumference of the TIA 4.

[0031] Referring again to FIG. 4, the spacer 101 has an edge extending beyond the TIA outward, i.e., toward the adjacent component, on the lid 8 side in the height direction, so that the overflowing adhesive 11 can be guided into the recesses 102-1 and 102-2. The overflowing adhesive is unlikely to cause a short circuit with adjacent components such as chip capacitors, so that the troublesome X-ray inspection that was previously required is no longer necessary. The yield of the optical module can also be improved. By slightly changing the spacer shape and forming a recess on the adhesive surface of the lid, the controllability of the adhesive can be improved significantly compared to the conventional optical module shown in FIG. 3.

[0032] Therefore, the optical module of the present disclosure can be implemented as comprising a package 1, an optical circuit 2 mounted in the package, one or more electronic circuits 3, 4 mounted in the package, and a lid 8 covering the optical circuit and the one or more electronic circuits, wherein one chip 4 of the one or more electronic circuits is fixed to an adhesive surface 22 of the lid in the thickness direction in the following order: first adhesive layer 12, spacer 101, second adhesive layer 11, the spacer having a first surface 103-1 on the lid side having a width wider than the width of the chip and a second surface 103-2 having a width narrower than the first surface, and the lid can be implemented as having recesses 102-1, 102-2 that are continuous with the adhesive surface and that store adhesive of the second adhesive layer in an area including an edge of the spacer extending in the width direction of the first surface.

[0033] In the optical module of FIG. 4, the adhesive surface 22 of the lid 8 is the shallower of two adhesive surfaces of different depths formed by carving (by countersinking) one side of the lid 8. However, if the number, configuration, and size of electronic circuit chips in the optical module are different, the adhesive surface 22 is not limited to the configuration of FIG. 4. It is also possible to have only one adhesive surface formed by carving one side of the lid, and to bond a TIA via a spacer 101 to the outermost surface of the lid as the other adhesive surface for an electronic component chip that requires heat dissipation. The relationship between the TIA 4 and the spacer 101 and the adhesive surface 22 of the lid does not depend on the position of the adhesive surface on the inner surface of the lid 8.

[0034] FIG. 7 is a diagram for explaining the manufacturing process of the spacer of the TIA in the optical module of the present disclosure. Each figure shows the configuration of two surfaces corresponding to the top and side of the completed spacer. In step 1 shown in (a), a highly heat-conductive material such as AlN is processed into a rectangular plate 110. Next, in step 2 shown in (b), a part 111 of the broken line on one side of the rectangular plate 110 is removed by cutting to form equally spaced grooves 112. Next, in step 3 shown in (c), the spacer is cut by dicing or the like along the broken line 113 at the center position of the formed groove 112. Finally, as shown in step 4 in (d), a cut spacer 101 having the same shape as that shown in FIG. 5(a) is obtained.

[0035] By modifying the above-mentioned manufacturing procedure, it is also possible to make a spacer with edges extending toward adjacent components on all four sides, as shown in Fig. 5(b). In the above-mentioned manufacturing process, the spacer is obtained by cutting a plate material that serves as the base material, but it is also possible to manufacture the spacer by gluing two plates together. Therefore, it should be noted that the manufacturing method of the spacer based on the cutting process in Fig. 7 is only one example.

[0036] FIG. 8 is a diagram for explaining the relationship between the spacer shape and the recess formed in the lid in the optical module of the present disclosure. FIG. 8(a) corresponds to the configuration of the optical module 100 of the first embodiment of FIG. 4. As already explained, the spacer 101 can be considered to be composed of an extension part 101a on the lid 8 side in the thickness direction and a base part 101b on the TIA side. As explained in FIG. 4, the width of the first surface (upper surface) of the spacer, which is wider than the TIA when viewing a cross section including adjacent components, is defined as L1. The width of the second surface (lower surface) which is narrower than the first surface is defined as L2.

[0037] The edge of the extension part 101a of the spacer on the lid side is preferably positioned so as to be contained within the two recesses 102-1, 102-2 formed in the lid 8. Specifically, the width L1 between both ends of the extended edge of the spacer should be between the shortest distance d2 and the maximum distance d1 between the two recesses. If the width L1 of the spacer is narrower than the minimum distance d2 between the recesses, the adhesive will overflow from the adhesive surface of the lid 8 toward the TIA and the adjacent components. Also, if the width L1 of the spacer is wider than the maximum distance d1 between the recesses, the edge and the adjacent components will be significantly closer. Taking into consideration the heat dissipation effect, the spacer and the recesses should be configured so that the end of the spacer is positioned approximately in the center of the recess, as shown in FIG. 8(a).

[0038] The minimum distance d2 between the recesses is preferably slightly narrower than the width of the TIA (not shown) in order to ensure a sufficient contact area with the spacer 101. As shown in Fig. 4, the width L2 of the portion of the spacer on the TIA side (base portion 101b in Fig. 8) is slightly narrower than the width of the TIA in order to allow the periphery of the TIA to be a pool of adhesive. From the viewpoint of forming a smooth heat dissipation path from the TIA 4, it is preferable to set the width L2 of the base portion 101b of the spacer and the minimum distance d2 between the recesses to be approximately the same length.

[0039] Fig. 8(b) shows another example of the spacer configuration for preventing the adhesive from squeezing out. Spacer 101-3 in Fig. 8(b) has protrusion 101c extending from the extended edge of the spacer's extended portion toward the inside of the recess in the thickness direction. This protrusion 101c makes it possible to guide adhesive that squels out from between the spacer and adhesive surface 22 toward the back of the recess. Protrusion 101c of spacer 101-3 can be manufactured by adding or modifying the manufacturing process of the spacer shown in Fig. 7.

[0040] In the above description, the adjacent components that should be considered for mounting are on both sides of the TIA when viewed in cross section, and the cross-sectional shape of the spacer and the configuration of the recess in the lid are also symmetrical with respect to the center line of the TIA. However, in the case of a different circuit arrangement in a TIA chip or an electronic component chip that is not a TIA, there may be adjacent components on only one side of the chip. In such cases, an asymmetric spacer configuration with an extension on only one side is also possible. Considering the predictability of adhesive behavior, assembly problems caused by asymmetry, and the spacer manufacturing process, the above-mentioned symmetric configuration is more preferable.

[0041] In the following, another embodiment in which the optical module of the first embodiment shown in FIG. 4 is modified will be described.

[0042] [Embodiment 2] Fig. 9 is a diagram showing an enlarged cross-sectional structure perpendicular to the substrate surface around the TIA of the optical module of embodiment 2. The basic structure of optical module 200 is similar to the cross-sectional structure around the TIA of conventional optical module 20 of Figs. 1 to 3 and embodiment 1 of Fig. 4, and only the structure of spacer 201 differs from optical module 100 of embodiment 1.

[0043] The spacer 201 corresponds to the spacer 101-3 having a protrusion shown in FIG. 8(b). That is, the spacer 201 has a wide extension part on the lid 8 side and a base part on the TIA 4 side in the thickness direction (z axis), and has a generally T-shaped cross section (yz plane). The extension part has an edge part extending toward the side where the adjacent components, the chip capacitors 5a and 5b, are located. The spacer 201 further has a protrusion part 202 formed from the edge part of the extension part toward the inside of the recesses 102-1 and 102-2 formed in the lid. The presence of the protrusion part 202 guides the adhesive 11 that protrudes from the adhesive surface on the lid side of the spacer 201 to the back of the recess. The adhesive controllability is further improved compared to the T-shaped spacer 101 of the first embodiment.

[0044] [Embodiment 3] 10 is a diagram showing a cross-sectional structure perpendicular to the substrate surface, enlarging the TIA periphery of the optical module of the third embodiment. In the optical module 300, only the spacer 301 is different from the spacer 101 in the first embodiment and the spacer 201 in the second embodiment. The above-mentioned spacers 101 and 201 included two parts in the thickness direction (z axis): a wide extension part on the lid side and a narrow base part on the TIA 4 side. That is, they had a first surface wider than the TIA and a second surface narrower than the first surface. The wide extension part including the surface wider than the TIA could prevent the adhesive from overflowing from the adhesive surface on the lid side toward the adjacent components.

[0045] The spacer 301 of the optical module 300 has an inverted trapezoid shape in a cross section (yz plane) including adjacent components, and has a first surface that is wider than the TIA on the lid side, and a second surface that is narrower than the first surface on the TIA side. Even if the width increases from the TIA 4 to the lid 8 in the thickness direction (z axis), the first surface on the lid side that is wider than the TIA prevents the adhesive from overflowing from the adhesive surface on the lid side toward the adjacent components. In FIG. 10, the cross-sectional shape of the spacer 301 increases in width linearly from the TIA 4 to the lid 8, but the rate of change in width is arbitrary and may be a curved change.

[0046] [Embodiment 4] 11 is an enlarged cross-sectional view perpendicular to the substrate surface of the optical module of embodiment 4, showing the TIA periphery of the optical module of embodiment 4. A spacer 401 in the optical module 400 is the same as the spacer 101 in embodiment 1, which has a T-shaped cross section.

[0047] In the optical module 400 of the fourth embodiment, in addition to the recesses 402-1 and 402-5 corresponding to the positions of the extended edge of the spacer, additional recesses 402-2 to 402-4 are formed above the spacer 401 in the lid 8. By adding the recesses, the excess adhesive is stored in the added recesses, and the overflow to the adjacent components is reduced. However, the area of ​​the heat dissipation surface is reduced, so consideration must be given to this point.

[0048] [Embodiment 5] 12 is a diagram showing an enlarged cross-sectional structure perpendicular to the substrate surface of the optical module of embodiment 5 around the TIA. In the optical module 500, the recess in the lid 8 of the other embodiments is omitted. Instead, a recess is provided on the front side of the extended edge of the spacer 501, and excess adhesive can be accommodated in this recess. Since no processing for the recess in the lid is required, costs can be reduced and the controllability of the adhesive can be improved.

[0049] In the above-mentioned embodiments, the optical module includes two types of electronic circuit chips, a driver IC and a TIA, and the TIA, which has the lowest height, dissipates heat through a spacer. However, if the integration of electronic circuit chips changes, the TIA and the driver IC may be integrated into one chip, or the TIA or the driver IC may be integrated with other electrical signal processing functions. Even in such cases, the effect of improving the controllability of the adhesive around the electronic circuit chip that requires heat dissipation through the spacer remains the same.

[0050] As described above in detail, the optical module of the present disclosure improves controllability of the adhesive used in the optical module, and prevents short circuit defects caused by the adhesive protruding out. This increases the manufacturing yield of the optical module, simplifies the inspection process, and reduces costs. [Industrial Applicability]

[0051] The present invention can be generally applied to optical communications. [Explanation of symbols]

[0052] 2. SiP chip 3 Driver IC 4, 4a, 4b TIA 5a, 5b Chip capacitors 7, 101, 201, 301, 401, 501 Spacer 8 Lid 9, 10 BGA 11, 12 Adhesive 20, 100, 200, 300, 400, 500 Optical Modules 22 Adhesive surface 102, 102-1, 102-2, 402-1 to 402-5 recess 112 Groove

Claims

1. Package and an optical circuit mounted in the package; one or more electronic circuits mounted in the package; a lid covering the optical circuit and the one or more electronic circuits; Equipped with one chip of the one or more electronic circuits is fixed to an adhesive surface of the lid in the following order in a thickness direction: a first adhesive layer, a spacer, and a second adhesive layer; the spacer has a first surface on the lid side, the first surface having a width greater than a width of the chip, and a second surface on the lid side, the second surface having a width smaller than that of the first surface; The lid has a recess that is continuous with the adhesive surface and that contains the adhesive of the second adhesive layer in a region including an edge of the spacer that extends in a width direction of the first surface. An optical module comprising:

2. The optical module of claim 1, wherein the spacer has an approximately T-shape in vertical cross section, includes an extended portion that includes the first surface and has an edge extending in the width direction of the chip, and a base portion that includes the second surface that is narrower than the width of the chip.

3. The optical module according to claim 1, wherein the spacer has a generally trapezoidal shape in a vertical cross section, the width of which gradually increases in a thickness direction from the second surface, which is narrower than the width of the chip, toward the first surface.

4. 4. The optical module according to claim 2, further comprising a protrusion extending from the edge portion toward the inside of the recess.

5. 2. The optical module of claim 1, wherein the optical circuit is a silicon photonics chip, and the one chip of the one or more electronic circuits is a transimpedance amplifier (TIA).

6. 2. The optical module according to claim 1, wherein the adhesive of the adhesive layer is a highly thermally conductive adhesive having a viscosity of 8 to 350 Pa·s (at 23° C.).

7. the optical circuit is fixed by an adhesive to an adhesive surface at a first depth formed below the outermost surface of the lid; 2. The optical module according to claim 1, wherein the adhesive surface to which the chip is fixed is an adhesive surface having a second depth that is formed lower than the adhesive surface having the first depth.

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