Optical Module

Abstract

The present invention provides an optical module, the purpose of which is to improve the high-frequency characteristics brought about by stable wire bonding. The optical module (100) has: a mounting substrate (28) on which a photoelectric element (24) is mounted; a support block (36) on which the mounting substrate is mounted; a tube seat (10) having a support surface (16) for supporting the support block and having a base portion (18) protruding integrally from the support surface; a connecting block (60) fixed to the front end surface (20) of the base portion; and a plurality of leads (72) connecting at least one of the supporting block and the mounting substrate to the connecting block. The connecting block has a first bonding surface (68) facing the same direction as the front end surface of the base portion and a second bonding surface (70) facing the same direction as the upper surface (22). The plurality of leads include a first lead (74) having one end bonded to the first bonding surface and a second lead (76) having one end bonded to the second bonding surface.

Description

Technical Field

[0001] The invention relates to an optical module. Background Art

[0002] Small optical modules require improved heat dissipation and high-frequency characteristics. The TO-CAN (Transistor Outline Can) package uses pins that penetrate holes at ground potential to transmit electrical signals to semiconductor optical elements (Patent Document 1). The substrate on which the semiconductor optical element is mounted is mounted on a support block.

[0003] Prior art literature

[0004] Patent Document 1: Japanese Patent Application Publication No. 2011-108939

[0005] If the grounding of the support block is strengthened, the high frequency characteristics can be improved. For example, the base protruding from the eyelet as a whole can be electrically connected to the support block by a lead wire. However, it is difficult to process the base into a shape suitable for bonding. Summary of the invention

[0006] An object of the present invention is to improve high frequency characteristics by stable wire bonding.

[0007] The optical module comprises: a photoelectric element, which converts an optical signal and an electrical signal from at least one of them to the other; a mounting substrate, on which the photoelectric element is mounted; a support block, on which the mounting substrate is mounted, and at least the surface of which is composed of a conductor; a stem, which has a support surface for supporting the support block and has a base portion protruding integrally from the support surface, the base portion having a front end surface in a protruding direction and an upper surface extending along the protruding direction; a relay substrate, which is mounted on the upper surface of the base portion; a connecting block, which is fixed to the front end surface of the base portion; and a plurality of leads, which respectively connect one of the support block and the mounting substrate to the connecting block, at least a portion of the surface of the connecting block is composed of a conductor, and has a first bonding surface facing the same direction as the front end surface of the base portion and a second bonding surface facing the same direction as the upper surface, the plurality of leads including: at least one first lead having one end bonded to the first bonding surface and at least one second lead having one end bonded to the second bonding surface.

[0008] The connection block ensures a surface for wire bonding, thereby enabling stable wire bonding. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 It is a perspective view of the optical module according to the first embodiment.

[0010] Figure 2This is a perspective view of a stem and electronic components mounted on the stem.

[0011] Figure 3 This is a top view of a stem and electronic components mounted on the stem.

[0012] Figure 4 It is a three-dimensional diagram of the connection block.

[0013] Figure 5 It is a perspective view of a stem according to a second embodiment and an electronic component mounted on the stem.

[0014] Figure 6 This is a side view of a stem and an electronic component mounted on the stem.

[0015] Figure 7 This is a bottom view of a stem and electronic components mounted on the stem.

[0016] Figure 8 It is a diagram showing the frequency characteristics of the conventional example, the first embodiment, and the second embodiment calculated by the three-dimensional electromagnetic field simulator HFSS (High Frequency Structure Simulator).

[0017] In the figure: 10—tube seat, 12—eyelet, 14—through hole, 16—support surface, 18—base portion, 20—front end surface, 22—upper surface, 24—photoelectric element, 26—semiconductor laser, 27—optical modulator, 28—mounting substrate, 30—first ground pattern, 32—first signal pattern, 34—first side electrode, 36—support block, 42—bypass capacitor, 44—thermoelectric cooler, 46—metal layer, 48—thermistor, 50—relay substrate, 52—second signal pattern, 54—filling material, 56—second ground pattern, 58—second side electrode, 60—connection block, 62—conductive adhesive, 63—second side electrode, 64—second side electrode, 65—second side electrode, 66—second side electrode, 67—second side electrode, 68—second side electrode, 69—second side electrode, 70—second side electrode, 71—second side electrode, 72—second side electrode, 73—second side electrode, 74—second side electrode, 75—second side electrode, 76—second side electrode, 77—second side electrode, 78—second side electrode, 79—second side electrode, 80—second side electrode, 81—second side electrode, 82—second side electrode, 83—second side electrode, 84—second side electrode, 85—second side electrode, 86—second side electrode, 87—second side electrode, 88—second side electrode, 89—second side electrode, 90—second side electrode, 91—second side electrode, 92—second side electrode, 93—second side electrode, 94—second side electrode, 95—second side electrode, 96—second side electrode, 97—second side electrode, 98—second side electrode, 99—second side electrode, 100 4—main body, 66—conductive film, 68—first bonding surface, 70—second bonding surface, 72—lead, 74—first lead, 76—second lead, 100—optical module, 102—flexible substrate, 104—printed substrate, 218—base portion, 228—mounting substrate, 236—support block, 260—connecting block, 270—second bonding surface, 272—lead, 278—third bonding surface, 280—third lead, L—pin, L1—pin, L2—pin, L3—pin, L4—pin, W1—lead, W2—lead, W3—lead, W4—lead, W5—lead, W6—lead, W7—lead. DETAILED DESCRIPTION

[0018] Hereinafter, the embodiments of the present invention will be specifically and in detail described with reference to the accompanying drawings. In all the drawings, the components with the same reference numerals have the same or equivalent functions, and their repeated descriptions are omitted. In addition, the size of the figure is not necessarily consistent with the magnification.

[0019] [First embodiment]

[0020] Figure 1 It is a stereoscopic diagram of the optical module involved in the first embodiment. The optical module 100 is a TO-CAN (Transistor Outline-Can) type optical module, and may also include any one of an optical transmitting subassembly (TOSA: Transmitter Optical Sub-Assembly) having a light-emitting element, an optical receiving subassembly (ROSA: Receiver Optical Sub-Assembly) having a light-receiving element, and a bidirectional module (BOSA; Bidirectional Optical Sub-Assembly) having both a light-emitting element and a light-receiving element. The optical module 100 has a flexible substrate (FPC) 102, which is connected to a printed circuit board (PCB) 104. The optical module 100 has a stem 10.

[0021] [Tube seat and base]

[0022] Figure 2 It is a perspective view of the stem 10 and the electronic components mounted on the stem 10 . Figure 3 1 is a top view of a stem 10 and an electronic component mounted on the stem 10. The stem 10 is made of a conductive material such as metal. The stem 10 includes a hole 12. The hole 12 has a plurality of through holes 14 that penetrate between the front surface and the back surface in the thickness direction. In addition, the stem 10 may have a portion of another shape such as a quadrilateral instead of the hole 12 that suggests a disc shape. The stem 10 is connected to a reference potential (for example, ground).

[0023] The stem 10 (hole 12) has a support surface 16 for supporting the electronic component. The stem 10 has a base portion 18 that protrudes integrally from the support surface 16. The base portion 18 is also made of a conductor. The surface of the base portion 18 is plated with metal. The base portion 18 has a front end surface 20 in the protruding direction. The base portion 18 has an upper surface 22 that expands along the protruding direction. Since the base portion 18 is formed by stamping, the corners are easily rounded and it is difficult to form a wide flat surface.

[0024] [Pin]

[0025] like Figure 1As shown, the optical module 100 has a plurality of pins L. The plurality of pins L are fixed to the inner side of the plurality of through holes 14 by dielectrics (insulators) such as glass to be insulated from the stem 10. The pins L and the dielectric constitute a feedthrough. The plurality of pins L are connected to the flexible substrate 102 ( Figure 1 ).

[0026] [Photoelectric components]

[0027] The optical module 100 has a photoelectric element 24. The photoelectric element 24 converts at least one of an optical signal and an electrical signal into the other. A semiconductor laser 26 and an optical modulator 27 are integrated in the photoelectric element 24. A lead W1 is bonded to the semiconductor laser 26, and a DC voltage is applied. The optical modulator 27 is driven by a single end. The photoelectric element 24 is mounted on a mounting substrate 28.

[0028] [Mounting substrate]

[0029] The mounting substrate 28 has a mounting surface on which the photoelectric element 24 is mounted. The photoelectric element 24 is arranged so that the optical axis is oriented in a direction parallel to the mounting surface. Figure 3 As shown, the mounting substrate 28 has a first ground pattern 30 and a first signal pattern 32 on the mounting surface.

[0030] The back side of the photoelectric element 24 (the electrode shared by the semiconductor laser 26 and the optical modulator 27) is joined to the first ground pattern 30. The first ground pattern 30 is integrated with the first side electrode 34 and can be electrically connected on the side opposite to the mounting surface. The first signal pattern 32 is electrically connected to the photoelectric element 24 (optical modulator 27) through the lead W2, so that a high-frequency signal is input. In addition, a terminal resistor not shown in the figure can also be set on the mounting substrate 28 to suppress the reflected wave of the modulated electrical signal with a high-frequency component from being reflected back to the driver IC (not shown). The mounting substrate 28 is mounted on the support block 36.

[0031] [Support block]

[0032] The support block 36 is composed of a main body and a conductive film covering the surface of the main body. The main body is composed of a material (ceramic) with excellent thermal conductivity such as aluminum nitride, which can improve heat dissipation. At least the surface of the support block 36 is composed of a conductor. Alternatively, the support block 36 can also be composed of a conductor as a whole as a metal block. The mounting substrate 28 is opposite to the conductive film of the support block 36, and the two are electrically connected.

[0033] A bypass capacitor 42 is mounted on the support block 36. The back side (one electrode) of the bypass capacitor 42 is connected to the support block 36 (conductive film) and is connected to a reference potential (e.g., ground). The other electrode of the bypass capacitor 42 is connected to the pin L1 via the lead wire W3 and a voltage is applied. The voltage is also connected to the photoelectric element 24 (semiconductor laser 26) via the lead wire W1 and a DC voltage is supplied. The high-frequency signal superimposed on the DC signal is separated by the bypass capacitor 42.

[0034] [Thermoelectric Cooler]

[0035] The optical module 100 has a thermoelectric cooler 44. The thermoelectric cooler 44 has an upper surface and a lower surface. The upper surface and the lower surface are made of an insulator such as ceramic. The lower surface is fixed to the support surface 16 of the tube seat 10 (hole 12). A thermally conductive adhesive can also be used for fixing. Figure 2 As shown, the upper surface and the mounting surface of the mounting substrate 28 face in directions that intersect each other (e.g., orthogonal). The thermoelectric cooler 44 has a Peltier element (not shown) inside for transferring heat between the upper surface and the lower surface. For example, the upper surface becomes a heat absorbing surface and the lower surface becomes a heat dissipating surface, but they are switched in the opposite direction. The electrode of the thermoelectric cooler 44 is connected to the pin L2 through the lead wire W4.

[0036] A metal layer 46 ( Figure 2 The metal layer 46 serves as a reference potential plane (for example, a ground plane). The thermistor 48 is placed on the metal layer 46 and electrically connected to the thermistor 48, and can measure the temperature. The thermistor 48 is connected to the pin L3 via the lead wire W5, and a voltage is applied to the thermistor 48.

[0037] Thermoelectric cooler 44 is fixed between support surface 16 of stem 10 and support block 36 to transfer heat therebetween. Support block 36 is supported on support surface 16 of stem 10 via thermoelectric cooler 44. Support block 36 is fixed to the upper surface of thermoelectric cooler 44 and electrically connected to metal layer 46.

[0038] [Relay board]

[0039] Interconnect substrate 50 is mounted on upper surface 22 of base portion 18 of stem 10. Solder (not shown) is used to fix the two together, and may overflow from below interconnect substrate 50. Base portion 18 protrudes from interconnect substrate 50 in a protruding direction.

[0040] like Figure 3 As shown, the relay substrate 50 has a second signal pattern 52. The second signal pattern 52 is electrically connected to the lead L4. Specifically, a filler 54 (solder, solder) is interposed between the end of the lead L4 and the terminal of the second signal pattern 52 to electrically connect the two.

[0041] The second signal pattern 52 is connected to the first signal pattern 32 via the lead wire W6. The relay substrate 50 has a second ground pattern 56. The second ground pattern 56 is integrated with the second side electrode 58, and can be electrically connected to the back surface and the base portion 18. In addition, the second ground pattern 56 is connected to the support block 36 via the lead wire W7.

[0042] [Connection block]

[0043] Figure 4 : is a three-dimensional view of the connection block 60. The connection block 60 is fixed to the front end surface 20 of the base portion 18. A conductive adhesive 62 or a filling material is used for fixing. At least a part of the surface of the connection block 60 is made of a conductor. The connection block 60 includes a main body 64 made of ceramic and a conductive film 66 covering the main body 64. The connection block 60 has a lower thermal conductivity than the tube seat 10. The connection block 60 can be formed of metal as a whole, but when the main body 64 is formed of ceramic, processing is simple and cost-effective.

[0044] The connection block 60 has a first joint surface 68. The first joint surface 68 faces the same direction as the front end surface 20 of the base portion 18. The first joint surface 68 is a flat surface. The longitudinal direction ( Figure 2 The length in the up-down direction) is greater than the width perpendicular to it.

[0045] The connecting block 60 has a second joint surface 70. The second joint surface 70 faces the same direction as the upper surface 22 of the base portion 18. The second joint surface 70 is a flat surface. The second joint surface 70 is located at a position higher than the upper surface 22 of the base portion 18. The length of the second joint surface 70 in the longitudinal direction (the protruding direction of the base portion 18) is greater than the width perpendicular thereto.

[0046] [lead]

[0047] The optical module 100 includes a plurality of leads 72 in addition to the leads W1 to W7 described above. Each lead 72 connects the support block 36 or the mounting substrate 28 to the connection block 60 .

[0048] One end of at least one first lead 74 is bonded to the first bonding surface 68. The other end of at least one first lead 74 is bonded to the support block 36. Figure 2 As shown, the plurality of first leads 74 are bonded to a plurality of first positions arranged in a row on the first bonding surface 68. The direction in which the plurality of first positions are arranged is the longitudinal direction of the first bonding surface 68.

[0049] One end of at least one second lead 76 is bonded to the second bonding surface 70. The other end of at least one second lead 76 is bonded to the mounting substrate 28 (first ground pattern 30). Figure 2As shown, the plurality of second leads 76 are bonded to a plurality of second positions arranged in a row on the second bonding surface 70. The direction in which the plurality of second positions are arranged is the longitudinal direction of the second bonding surface 70.

[0050] If the solder (not shown) fixing the relay substrate 50 to the upper surface 22 of the base portion 18 overflows, the wire bonding area of ​​the base portion 18 becomes narrow. However, in this embodiment, by providing the connection block 60, the wire bonding area can be ensured, and stable wire bonding can be performed. In addition, the protruding length of the base portion 18 can be shortened, and there is no need to ensure a wide flat surface, so there is no need to improve the processing accuracy.

[0051] [Second embodiment]

[0052] Figure 5 It is a perspective view of a stem according to a second embodiment and an electronic component mounted on the stem. Figure 6 This is a side view of a stem and an electronic component mounted on the stem. Figure 7 This is a bottom view of a stem and electronic components mounted on the stem.

[0053] The connection block 260 has a third joint surface 278 opposite to the second joint surface 270. The third joint surface 278 is a flat surface. The length of the third joint surface 278 in the longitudinal direction (the protruding direction of the base portion 218) is greater than the width perpendicular thereto.

[0054] The plurality of leads 272 include at least one third lead 280 having one end bonded to the third bonding surface 278. The other end of the at least one third lead 280 is bonded to the support block 236 (e.g., the back surface thereof). The plurality of third leads 280 are bonded to a plurality of third positions arranged in a row on the third bonding surface 278. The direction in which the plurality of third positions are arranged is the longitudinal direction of the third bonding surface 278.

[0055] The base portion 218 and the support block 236 (or the mounting substrate 228 as a modified example) are connected by the third lead 280. Thus, the grounding of the support block 236 (or the mounting substrate 228 as a modified example) can be strengthened, and high-frequency signal transmission can be performed. Other contents can be applied to the contents described in the first embodiment.

[0056] Figure 8 The diagram shows the frequency characteristics of the conventional example, the first embodiment, and the second embodiment calculated by the 3D electromagnetic field simulator HFSS (High Frequency Structure Simulator). In the conventional example, no connection block is provided.

[0057] Compared with the conventional example, the first embodiment, which ensures a wider bonding area, improves the transmission characteristics particularly at 40 GHz or higher. The second embodiment further improves the transmission characteristics.

[0058] [Overview of Embodiments]

[0059] (1) The optical module 100 comprises: a photoelectric element 24 that converts at least one of an optical signal and an electrical signal into the other; a mounting substrate 28 that mounts the photoelectric element 24; a support block 36 that mounts the mounting substrate 28 and has at least a surface formed of a conductor; a stem 10 that has a support surface 16 that supports the support block 36 and a base portion 18 that protrudes integrally from the support surface 16, the base portion 18 having a front end surface 20 in a protruding direction and an upper surface 22 that extends along the protruding direction; and a relay substrate 50 that is mounted on the upper surface 22 of the base portion 18. ; a connecting block 60, which is fixed to the front end surface 20 of the base portion 18; and a plurality of leads 72, which respectively connect the support block 36 and one of the mounting substrate 28 to the connecting block 60, at least a portion of the surface of the connecting block 60 is composed of a conductor, having a first bonding surface 68 facing the same direction as the front end surface 20 of the base portion 18 and a second bonding surface 70 facing the same direction as the upper surface 22, and the plurality of leads 72 include at least one first lead 74 having one end bonded to the first bonding surface 68 and at least one second lead 76 having one end bonded to the second bonding surface 70.

[0060] (2) In the optical module 100 described in (1), the other end of at least one first lead 74 is bonded to the support block 36 , and the other end of at least one second lead 76 is bonded to the mounting substrate 28 .

[0061] (3) In the optical module 100 described in (1) or (2), the at least one first lead 74 is a plurality of first leads 74 , and the plurality of first leads 74 are bonded to a plurality of first positions arranged in a row on the first bonding surface 68 .

[0062] (4) In the optical module 100 described in (3), the length of the first joint surface 68 in the direction in which the plurality of first positions are arranged is larger than the width perpendicular to the length.

[0063] (5) In the optical module 100 according to any one of (1) to (4), the at least one second lead 76 is a plurality of second leads 76 , and the plurality of second leads 76 are bonded to a plurality of second positions arranged in a row on the second bonding surface 70 .

[0064] (6) In the optical module 100 described in (5), the length of the second joint surface 70 in the direction in which the plurality of second positions are arranged is larger than the width perpendicular to the length.

[0065] (7) In the optical module 100 according to any one of (1) to (6), the base portion 18 protrudes from the relay substrate 50 in the protruding direction.

[0066] (8) In the optical module 100 according to any one of (1) to (7), the second joint surface 70 of the connection block 60 is located higher than the upper surface 22 of the base portion 18 .

[0067] (9) In the optical module 100 according to any one of (1) to (8), the first bonding surface 68 and the second bonding surface 70 are flat surfaces.

[0068] (10) According to the optical module 100 described in any one of (1) to (9), the connection block 60 includes a main body 64 made of ceramic and a conductive film 66 covering the main body 64 .

[0069] (11) According to the optical module 100 described in any one of (1) to (10), the support block 36 includes a main body made of ceramic and a conductive film covering the main body.

[0070] (12) In the optical module 100 according to any one of (1) to (11), the connection block 60 has a lower thermal conductivity than the stem 10 .

[0071] (13) The optical module 100 according to any one of (1) to (12), further comprising a conductive adhesive 62 or a filler material for fixing the connection block 60 and the base portion 18 .

[0072] (14) The optical module 100 according to any one of (1) to (13) further includes a thermoelectric cooler 44 fixed between the support surface 16 of the stem 10 and the support block 36 to transfer heat.

[0073] (15) In the optical module according to any one of (1) to (14), the connection block 260 has a third bonding surface 278 opposite to the second bonding surface 270 , and the plurality of leads 272 include at least one third lead 280 having one end bonded to the third bonding surface 278 .

[0074] (16) In the optical module described in (15), the other end of at least one third lead 280 is bonded to the supporting block 236 .

[0075] (17) In the optical module described in (15) or (16), the third bonding surface 278 is a flat surface.

[0076] (18) In the optical module described in (16) or (17), the at least one third lead 280 is a plurality of third leads 280 , and the plurality of third leads 280 are bonded to a plurality of third positions arranged in a row on the third bonding surface 278 .

[0077] (19) According to the optical module described in (18), the length of the third joint surface 278 in the direction in which the plurality of third positions are arranged is larger than the width perpendicular to the length.

[0078] The present invention is not limited to the above-described embodiments, and various modifications are possible. For example, the structure described in the embodiments may be replaced with a substantially identical structure, a structure having the same function and effect, or a structure capable of achieving the same purpose.

Claims

1. An optical module, characterized in that: have: Optoelectronic components that convert optical signals as well as electrical signals from at least one to the other; A mounting substrate, which carries the photoelectric element; A support block, which carries the mounting substrate and has at least a surface made of a conductor; A pipe seat having a support surface for supporting the support block and a base portion integrally protruding from the support surface, wherein the base portion has a front end surface in a protruding direction and an upper surface extending along the protruding direction; a relay substrate mounted on the upper surface of the base portion; a connecting block fixed to the front end surface of the base portion; as well as a plurality of leads, each of which connects one of the support block and the mounting substrate to the connection block; The connection block has at least a portion of its surface formed of a conductor and has a first joint surface facing the same direction as the front end surface of the base portion and a second joint surface facing the same direction as the upper surface. The plurality of leads include at least one first lead having one end bonded to the first bonding surface and at least one second lead having one end bonded to the second bonding surface.

2. The optical module according to claim 1, characterized in that: The other end of the at least one first lead is connected to the support block. The other end of the at least one second lead is bonded to the mounting substrate.

3. The optical module according to claim 1, characterized in that: The at least one first lead is a plurality of first leads, The plurality of first lead wires are bonded to a plurality of first positions arranged in a row on the first bonding surface.

4. The optical module according to claim 3, characterized in that: The length of the first joint surface in the direction in which the plurality of first positions are arranged is greater than a width perpendicular to the length.

5. The optical module according to claim 1, characterized in that: The at least one second lead is a plurality of second leads, The plurality of second lead wires are bonded to a plurality of second positions arranged in a row on the second bonding surface.

6. The optical module according to claim 5, characterized in that: The length of the second joint surface in the direction in which the plurality of second positions are arranged is greater than a width perpendicular to the length.

7. The optical module according to any one of claims 1 to 6, characterized in that: The base portion protrudes from the relay substrate in the protruding direction.

8. The optical module according to any one of claims 1 to 6, characterized in that: The second joint surface of the connection block is located at a position higher than the upper surface of the base portion.

9. The optical module according to any one of claims 1 to 6, characterized in that: The first joint surface and the second joint surface are flat surfaces.

10. The optical module according to any one of claims 1 to 6, characterized in that: The connection block includes a main body composed of ceramic and a conductive film covering the main body.

11. The optical module according to any one of claims 1 to 6, characterized in that: The supporting block includes a main body composed of ceramic and a conductive film covering the main body.

12. The optical module according to any one of claims 1 to 6, characterized in that: The connection block has a lower thermal conductivity than the tube seat.

13. The optical module according to any one of claims 1 to 6, characterized in that: The invention also comprises a conductive adhesive or a filling material for fixing the connection block and the base portion.

14. The optical module according to any one of claims 1 to 6, characterized in that: A thermoelectric cooler is also provided, which is fixed between the support surface of the tube holder and the support block to transfer heat.

15. The optical module according to any one of claims 1 to 6, characterized in that: The connecting block has a third joint surface opposite to the second joint surface, The plurality of leads include at least one third lead having one end bonded to the third bonding surface.

16. The optical module according to claim 15, characterized in that: The other end of the at least one third lead is bonded to the support block.

17. The optical module according to claim 15, characterized in that: The third joint surface is a flat surface.

18. The optical module according to claim 16, characterized in that: The at least one third lead is a plurality of third leads, The plurality of third leads are bonded to a plurality of third positions arranged in a row on the third bonding surface.

19. The optical module according to claim 18, characterized in that: The length of the third joint surface in the direction in which the plurality of third positions are arranged is greater than a width perpendicular to the length.

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