JP2004304205A - Optical module - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the heat resistance of an optical module by enhancing the heat conduction in the optical module having an insulation layer in which an optical element is mounted on a substrate having a waveguide. <P>SOLUTION: In the optical module having an insulation layer 5 in which an optical element 7 is mounted on the substrate 1 having the waveguide, the heat generated from the optical element 7 is effectively and widely dissipated by using a transparent resin layer 8 and a high heat conductive resin 9. The optical element 7, mounted on the silicon substrate 1 with the insulation layer 5 therebetween, and the periphery of a part or all of electric wiring for driving the optical element are covered with the transparent (in the wavelength of the optical element) resin 8, and further it is covered with the resin 9 of a higher coefficient of heat conductivity by applying, etc. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an optical circuit component using a planar optical waveguide circuit, and more particularly to an optical module having a structure that facilitates manufacturing of a substrate on which an optical element is mounted.

  It is extremely important to consider a heat dissipation structure in an optical element such as a laser diode that flows a large current. In a conventional optical module in which an optical hybrid is integrated on a substrate plane using an optical waveguide substrate, a heat dissipation structure has been adopted in which an optical element is flip-chip mounted on the surface of silicon to release heat to the silicon substrate (for example, non-patented). Reference 1).

  FIG. 3 shows the structure of the conventional example. As shown in FIG. 3 (a), a quartz waveguide is formed on a silicon substrate 1 processed into irregularities, and the claddings 2-1 and 2-2 of the optical waveguide and the glass of the optical waveguide core 3 are removed. The convex surface 1-1 of the silicon substrate is exposed. By forming the solder film 6-1 and the electric wiring 6-2 on the convex surface 1-1, an optical waveguide substrate having the optical element mounting portion 4 is obtained. The optical element 7 is mounted on the optical element mounting section 4 by flip chip bonding. Thereby, the heat generated in the optical element 7 is efficiently diffused into the silicon substrate 1, and the temperature rise of the optical element 7 is suppressed.

  FIG. 3B shows a cross-sectional structure of the above-described conventional optical module, in which the flow of heat from the optical element 7 to the silicon substrate 1 is indicated by an arrow 30. The heat generated by the optical element 7 flows to the silicon substrate 1 via the solder film 6-1 and the passivation film (glass) 5.

Hashimoto et al., "Mounting LD and Monitor PD by Passive Alignment on PLC Platform", 1996 IEICE General Conference C-206, p206 (1996)

  As described above, in the conventional technology, the optical waveguide is formed on the concavo-convex silicon substrate 1 and the optical element 7 is flip-chip mounted to release the heat of the optical element 7. Since the passivation film 5 interposed between the optical element 7 and the optical waveguide substrate 1 is made of a material such as glass, a non-negligible thermal resistance occurs. Thus, in the related art, there is a problem to be solved in that the insulating layer 5 on the silicon substrate 1 increases the thermal resistance.

  An object of the present invention is to solve the above-described problems and to improve the thermal resistance of an optical module having an insulating layer in which an optical element is mounted on a substrate having a waveguide.

  In order to achieve the above object, the invention of an optical module according to claim 1 is an optical module in which an optical element is mounted on a silicon substrate having a waveguide via an insulating layer, wherein the optical element has a high heat via a transparent resin layer. It is characterized by being covered with a conductive resin.

  Here, the transparent resin layer covers a part or the entire periphery of the optical element and electric wiring for driving the optical element, and further covers the high thermal conductive resin on the transparent resin layer. can do.

  In the present invention, in an optical module having an insulating layer in which an optical element is mounted on a substrate having a waveguide, the heat generated from the optical element is diffused efficiently and widely using a transparent resin layer and a high thermal conductive resin. Therefore, the heat radiation of the optical module can be improved.

  Further, according to the present invention, the optical element mounted on the silicon substrate via the insulating layer, and a resin (at the wavelength of the optical element) around part or all of the electric wiring for driving the optical element , And further coated thereon with a resin having a high thermal conductivity by coating or the like, so that the heat radiation of the optical module can be improved.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[Reference example]
FIG. 1A shows a sectional structure of a conventional example for comparison, and FIGS. 1B and 1C show sectional structures of an optical module of a reference example of the present invention. FIG. 1 shows a state where the optical element is mounted on the optical element mounting section.

  As shown in FIGS. 1B and 1C, the optical waveguide used in this embodiment is a quartz optical waveguide formed on a silicon substrate 1. The optical element mounting portion 4 was manufactured by removing a part of the clad portions 2-1 and 2-1 of the optical waveguide that covered the entire surface of the silicon substrate 1 by etching. At this time, the silicon surface used for the optical element mounting part 4 is exposed, and the optical element 7 and the silicon substrate 1 cannot be insulated. In this embodiment, a glass film 5 of about 2 μm is deposited as a passivation film on the entire surface of the optical waveguide substrate as a structure for obtaining the insulation.

  In the conventional structure shown in FIG. 1A, the area of the solder film 6 on the side to be bonded to each other and the area of the electrode of the optical element 7 are almost the same. Considering × 250 μm, a thermal resistance of about 20 ° C./W will occur at this junction. The optical element 7 used here was a laser diode (LD). Due to this thermal resistance, when driven by an injection current of 100 mA, the heat of the active layer portion 7-1 increased by about 2 ° C.

  Therefore, in this embodiment, as shown in FIG. 1B, the area of the solder film 6 used is increased 1.5 times while the size of the optical element 7 is kept as it is. Conventionally, the area of the solder film 6 and the area of the electrode of the optical element 7 are almost the same, so that the area of the solder film 6 of the present embodiment is sufficiently larger than the electrode pad of the optical element 7 as compared with the related art. .

  Since the solder film 6 used was AuSn solder having a thickness of 4 μm, the cross-sectional area of the solder film 6 was about 250 μm × 4 μm × 4 sides, but the thermal conductivity of the solder film 6 was Since it is about 300 times, the value of the thermal resistance of the glass 5 immediately below the optical element 7 is about 1/20, and as shown in FIG. Is diffused, and is radiated to the silicon substrate 1 through the glass 5 having a sectional area (in this case, 1.5 times the original area) to which the solder expanded portion 21 is added, in addition to the portion 20 immediately below the element. You. When the thermal resistance after mounting the optical element 7 was measured, the thermal resistance of the insulating layer portion 5 was reduced by about 20%.

  As described above, in the present reference example, the area of the solder film 6, which is a part of the electric wiring, is set to be sufficiently larger than the electrode area of the optical element 7 and is arranged in the optical element mounting section 4. It is possible to improve the thermal resistance by the layer 5.

[First Embodiment]
FIG. 2 shows a cross-sectional structure of the optical module according to the first embodiment of the present invention, and shows a state where the optical element 7 is mounted on the optical element mounting section 4. The optical waveguide used in the present embodiment is a quartz optical waveguide formed on a silicon substrate.

  The embodiment of FIG. 2 was manufactured in the same manner as the above-described reference example, and a glass film 5 of about 2 μm was deposited on the entire surface of the optical waveguide substrate 1. For this reason, considering the area of the junction of the laser diode (LD) 7 as the optical element used in the present embodiment, about 250 μm × 250 μm, a thermal resistance of about 20 ° C./W occurs in this part. . Therefore, as shown in FIG. 2A, in the present embodiment, a transparent silicone resin 8 is thinly applied to the periphery of the optical element 7 to about 2 μm, and about 4 W / (M · ° C.) resin 9 having a higher thermal conductivity than that of glass was applied. Here, the gap between the optical element 7 and the end face 2-3 of the optical waveguide is about 20 μm. Instead, the light enters the optical element active layer 7-1. Since the thermal resistance of the high thermal conductive resin 9 is about 1/4 of that of glass, when the optical element 7 is covered with the high thermal conductive resin 9, the heat generated from the optical element 7 is reduced by the arrow shown in FIG. The heat flows to the high thermal conductive resin 9 through the path indicated by reference numeral 30, thereby improving heat radiation.

  When the thermal resistance of this optical module was measured, the thermal resistance from the optical element 7 to the silicon substrate 1 was reduced by about 20%.

  Here, the periphery of the optical element 7 is covered with the resin 9 having high thermal conductivity. However, the optical element 7 and the electric wiring may be covered with the transparent resin 8 and a metal layer (not shown) may be provided thereon by vapor deposition or the like. Similar effects can be obtained.

  As described above, according to the present embodiment, the periphery of the optical element 7 is covered with the transparent resin 8 and the outside thereof is covered with the resin 9 having high thermal conductivity, so that the thermal resistance of the optical module can be easily and easily achieved. It becomes possible to lower efficiently.

[Other embodiments]
The present invention is not limited to the above-described embodiment. For example, the present embodiment and the above-described reference example may be freely combined as needed. Further, specific materials such as the above-described insulating film, transparent resin, and high heat conductive resin are not limited to the above-described embodiments. Further, the optical element constituting the optical module of the present invention is not limited to a laser diode, and the present invention is suitable for an optical module having an optical element that requires heat radiation due to a heat generating action.

7A and 7B are diagrams for explaining the principle of a reference example of the present invention, in which FIG. 7A is a longitudinal sectional view showing the structure of a conventional optical element mounting part, and FIG. FIG. 4C is a longitudinal sectional view on the front side showing the structure, and FIG. 4C is a longitudinal sectional view on the side shown by a wavy arrow showing a path when heat generated in the optical element in the optical element mounting portion of the present invention is radiated to the silicon substrate. FIG. FIGS. 2A and 2B are diagrams showing an optical element mounting portion and a heat dissipation structure in the optical module according to the first embodiment of the present invention, wherein FIG. 1A is a front vertical sectional view showing the structure of the optical element mounting portion, and FIG. FIG. 6 is a vertical cross-sectional view of a side surface of the mounting section, in which heat generated by the optical element is dissipated to the silicon substrate by a wavy arrow. FIGS. 2A and 2B are diagrams showing a configuration example of an optical module according to a conventional technique, wherein FIG. 1A is a perspective view showing the structure of an optical element mounting portion, and FIG. 2B is a path through which heat generated by the optical element is radiated to a silicon substrate. Is a longitudinal sectional view on the front side, which is indicated by a wavy arrow.

Explanation of reference numerals

DESCRIPTION OF SYMBOLS 1 Silicon substrate 1-1 Silicon substrate convex part 2 Cladding 2-1 Under cladding 2-2 Over cladding 2-3 Optical waveguide end surface 3 Optical waveguide core 4 Optical element mounting part 5 Glass (passivation) film, insulating layer 6 Solder film or Electrical wiring 6-1 AuSn solder film 6-2 Electrical wiring 7 Optical element 7-1 Optical element active layer 7-2 Optical element surface 8 Transparent resin 9 High heat conductive resin 10 Optical axis 20 Optical element direct portion 21 Solder expansion portion 30 Heat Flow of

Claims (2)

  An optical module comprising an optical element mounted on a silicon substrate having a waveguide via an insulating layer, wherein the optical element is covered with a high thermal conductive resin via a transparent resin layer.   The transparent resin layer covers a part or all of the optical element and electric wiring for driving the optical element, and further covers the high thermal conductive resin on the transparent resin layer. 2. The optical module according to 1.

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