JP2010182802A - Optical transmission module - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical transmission module which can achieve flip-chip mounting even when an optical element for wire bonding which is not for flip-chip mounting is used, and has a superior heat dissipation characteristics. <P>SOLUTION: In the optical transmission module in which the substrate 2 is stored in a case housing 8 and the optical element 3 having electrodes formed in an array on a surface on a side to be mounted on the substrate 2 is flip-chip mounted on the substrate 2, a module 5 for flip-chip mounting is formed by bonding the surface of the optical element 3 on the side opposite to the mounted surface to a base member 4, and the module 5 for flip-chip mounting is flip-chip mounted on the substrate 2 and is also brought into contact with the case housing 8 to form a heat dissipation path. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an optical transmission module in which an optical element is flip-chip mounted on a substrate.

  As a method for mounting an optical element such as a VCSEL (Vertical Cavity Surface Emitting LASER) on a substrate, flip chip mounting has attracted attention. Flip chip mounting is a mounting method in which an optical element and a substrate are electrically connected via bumps such as Au bumps and solder bumps.

  As shown in FIGS. 8A and 8B, the flip-chip mounting optical element 100 has two rows of electrodes (pads) 101. In the optical device 100 for flip-chip mounting, an anode electrode 101a and a cathode electrode (or dummy pad) 101b are formed for one light input / output unit (light emitting unit or light receiving unit) 102, respectively. The electrodes 101a and 101b are arranged on both sides of the part 102.

  In the optical device 100 for flip-chip mounting, the electrodes 101a and 101b on both sides of the light input / output unit 102 are bump-connected to the substrate 103, so that the optical device 100 is placed on the substrate 103 in a stable posture with the bumps 104 as legs. Implemented.

  An optical transmission module using the optical element 100 for flip chip mounting is shown in FIGS. FIG. 9A is a plan view and a side view of the optical transmission module, FIG. 9B is a plan view seen from the back surface, and FIG. 9C is an enlarged view of the A portion.

  As shown in FIGS. 9A to 9C, the optical transmission module 110 is obtained by flip-chip mounting an optical element 100 and an IC 113 for driving the optical element 100 on a substrate 112 on which a wiring pattern 111 is formed. . As the substrate 112, a substrate that is transparent to the light emitted from the optical element 100 (or the received light) is used. The anode electrode 101a of the optical element 100 is electrically connected to the IC 113 via the wiring pattern 111, and the cathode electrode 101b of the optical element 100 is electrically connected to the ground electrode 114 of the substrate 112.

  Flip chip mounting has the characteristics that the mounting area can be reduced and the electrical characteristics such as impedance matching are excellent because the wiring is short.

  On the other hand, wire bonding is known as a method for mounting an optical element on a substrate. In wire bonding, as shown in FIG. 10A, an optical element 120 for wire bonding is used, the surface of the optical element 120 on which the electrode 101 is not formed is mounted on a substrate (base) 122, and the electrode 101 is connected to a wire. It is electrically connected to the wiring pattern of the substrate 122 and other elements through 123.

  As shown in FIG. 10B, in the optical element 120 for wire bonding, electrodes 101 are formed in a line only on one side of the light input / output unit 102. Therefore, the optical element 120 for wire bonding is smaller than the optical element 100 for flip chip mounting in FIG. 8B.

  The prior art document information related to the invention of this application includes the following.

JP 2007-127796 A JP 2006-23777 A

  In general, the optical element 120 for wire bonding is less expensive than the optical element 100 for flip chip mounting because the overall size (area) of the element is smaller. This is because the price of the optical element depends on the number of wafers taken, and the smaller the area, the lower the price. Therefore, from the viewpoint of cost, it is desirable to use the optical element 120 for wire bonding as the optical element.

  However, in wire bonding, since the wire 123 has a certain length, an inductance component due to the wire 123 is generated, making it difficult to adjust the characteristic impedance, and as a result, the high-frequency characteristic is deteriorated. is there. Therefore, from the viewpoint of impedance matching, it is desirable to employ flip chip mounting that does not generate an inductance component. Therefore, there is a demand for realizing flip-chip mounting using the optical element 120 for wire bonding.

  However, as shown in FIG. 11, when the optical element 120 for wire bonding is flip-chip mounted on the substrate 131, the optical element 120 for wire bonding has only one row of electrodes 102. There is a problem that the optical axis of the optical element 120 is inclined due to the inclination with respect to 131.

  Further, since the optical element 100 (or 120) generates heat during driving, it is necessary to efficiently dissipate heat in order to suppress deterioration of characteristics due to heat of the optical element 100 (or 120).

  Accordingly, an object of the present invention is to provide an optical transmission module that solves the above-described problems and can realize flip-chip mounting even when using an optical element for wire bonding that is not for flip-chip mounting and has excellent heat dissipation. It is in.

  The present invention was devised to achieve the above object, and a substrate is housed in a case housing, and an optical element in which electrodes are formed in a row on a surface mounted on the substrate is flip-chip mounted on the substrate. An optical transmission module to be mounted, wherein a surface opposite to the mounting surface of the optical element is bonded to a base member to form a flip chip mounting module, and the flip chip mounting module is flip chip mounted on the substrate In addition, the optical transmission module has a heat dissipation path formed by bringing the flip chip mounting module into contact with the case housing.

  When the flip chip mounting module and the case housing are brought into contact with each other, the base member may be brought into contact with the case housing via a heat dissipation sheet.

  The flip chip mounting of the flip chip mounting module may be performed by bump-connecting the electrode of the optical element and the base member to the substrate.

  The optical element may be bonded to the base member, and an IC for driving the optical element may be bonded to form the flip chip mounting module, and the flip chip mounting module may be flip chip mounted.

  The optical element has a cathode electrode formed on the surface opposite to the mounting surface, the base member is made of a conductive member, and the cathode electrode of the optical element and the base member are interposed via a conductive adhesive. The base member and the ground electrode of the substrate may be electrically connected via bumps.

  The optical element is joined to the base member to form the flip chip mounting module, the electrodes of the optical element are bump-connected to the substrate, and the flip chip mounting module is flip chip mounted. May be fixed to the case housing.

  According to the present invention, it is possible to realize flip-chip mounting even with the use of an optical element for wire bonding that is not for flip-chip mounting, and it is possible to realize an optical transmission module excellent in heat dissipation.

It is a schematic sectional drawing of the optical transmission module which shows one Embodiment of this invention. FIG. 2A is a perspective view of an optical element in which one electrode is formed for each light input / output unit, and FIG. 2B is an optical element in which two electrodes are formed for each light input / output unit. FIG. In the optical element of FIG. 2A, it is a figure explaining that the surface on the opposite side to the surface in which the electrode was formed becomes a cathode electrode. FIG. 2 is a schematic cross-sectional view illustrating a structure for optically coupling an optical fiber and an optical element in the optical transmission module of FIG. 1. It is a schematic sectional drawing of the optical transmission module which shows one Embodiment of this invention. It is a schematic sectional drawing of the optical transmission module which shows one Embodiment of this invention. 7A is a plan view and a side view of the optical transmission module of FIG. 5, FIG. 7B is a plan view seen from the back side, and FIG. 7C is the flip chip mounting module. FIG. FIG. 8A is a schematic cross-sectional view of an optical element for flip chip mounting, and FIG. 8B is a perspective view thereof. FIG. 9A is a plan view and a side view of a conventional optical transmission module, FIG. 9B is a plan view seen from the back side, and FIG. 9C is an enlarged view of part A thereof. FIG. 10A is a schematic cross-sectional view of an optical transmission module on which an optical element for wire bonding is mounted, and FIG. 10B is a perspective view of the optical element for wire bonding. It is a schematic sectional drawing when the optical element of FIG.11 (b) is flip-chip mounted on the board | substrate.

  Preferred embodiments of the present invention will be described below with reference to the accompanying drawings.

  The optical transmission module of the present invention is used, for example, as an optical transceiver.

  FIG. 1 is a schematic cross-sectional view of an optical transmission module according to this embodiment.

  As shown in FIG. 1, an optical transmission module 1 is obtained by flip-chip mounting an optical element 3 having electrodes formed in a row on a mounting surface F on the side to be mounted on a substrate 2. 3 is bonded to the base member 4 to form a flip chip mounting module 5, and the flip chip mounting module 5 is flip chip mounted on the substrate 2 and the flip chip mounting module is mounted. 5 is brought into contact with the case housing 8 to form a heat radiation path.

  The optical element 3 is an optical element for wire bonding. In the present embodiment, a case where an arrayed VCSEL is used as the optical element 3 will be described. The reason why the optical elements 3 are arranged in an array is to increase the transmission capacity. The optical element 3 is not limited to this, and an optical element that is not in an array shape may be used, or a light emitting element other than a VCSEL or a light receiving element such as a photodiode may be used.

  As shown in FIGS. 2A and 2B, the optical element 3 includes a plurality of light emitting units (light input / output units) 31 formed in one row and one row on one side of the light emitting unit 31. A plurality of electrodes 32.

  2A shows the optical element 3 in which one electrode 32 is formed for each light emitting unit 31, and FIG. 2B shows an electrode 32a serving as an anode and an electrode serving as a cathode for each light emitting unit 31. An optical element 3 in which two electrodes 32 (or dummy pads) 32b are formed is shown. In the optical element 3 of FIG. 2A, as shown in FIG. 3, the electrode 32 becomes an anode, and the cathode is formed on the surface opposite to the surface on which the electrode 32 is formed (that is, the surface R opposite to the mounting surface). An electrode is formed.

  In the present invention, either of the optical elements 3 shown in FIGS. 2A and 2B can be used. In the present embodiment, a case where the optical element 3 of FIG. 2A is used will be described.

  As the substrate 2, it is preferable to use a substrate made of a transparent member with respect to the light emitted from the optical element 3 (or the received light). A predetermined wiring pattern is formed on the substrate 2, and an IC 6 for driving the optical element 3 is flip-chip mounted. The board | substrate 2 is not limited to a transparent member, For example, you may use what formed the hole for allowing the light which optical element 3 radiate | emits (or light to receive) to pass through.

  The base member 4 is for supporting the optical element 3, and includes a parallel portion 4a formed substantially parallel to the substrate 4 and a vertical portion 4b extending substantially perpendicularly from the parallel portion 4a to the substrate 2 side. It is formed in a substantially Γ shape in a sectional view. The flip chip mounting module 5 is formed by bonding the surface R opposite to the mounting surface of the optical element 3 to the surface of the parallel portion 4a of the base member 4 on the substrate 2 side. At this time, the mounting surface F of the optical element 3 and the height of the surface on the substrate 2 side of the vertical portion 4b of the base member 4 are made to coincide with each other.

  When the flip chip mounting module 5 is mounted on the substrate 2, the electrode 32 of the optical element 3 and the vertical portion 4 b of the base member 4 are bump-connected to the substrate 2. As the bump 7, an Au bump, a solder bump or the like may be used.

  Further, the flip chip mounting module 5 is brought into contact with the case housing 8 to form a heat radiation path for radiating heat generated in the optical element 3. The case housing 8 is for housing and protecting the substrate 2, the optical element 3, and the IC 6, and is formed so as to cover the substrate 2, the optical element 3, and the IC 6. The case housing 8 is made of metal, for example. In addition, the case housing 8 may be formed of a part where the flip chip mounting module 5 is in contact with metal and the other part of a material other than metal, for example, plastic.

  When the flip chip mounting module 5 and the case housing 8 are brought into contact with each other, the parallel portion 4a of the base member 4 may be brought into contact with the case housing 8 via a heat dissipation sheet (not shown). The heat radiating sheet is made of an insulating member, and the base member 4 and the case housing 8 are electrically insulated through the heat radiating sheet. Thereby, the heat generated in the optical element 3 is radiated to the outside through the heat radiation path including the base member 4, the heat radiation sheet, and the case housing 8. The base member 4 may be made of a material having high thermal conductivity.

  Further, in this embodiment, since the optical element 3 of FIG. 2A is used, it is necessary to electrically connect the cathode electrode (surface R opposite to the mounting surface) of the optical element 3 to the ground electrode of the substrate 2. is there.

  Therefore, in the present embodiment, the base member 4 is formed of a conductive member, the cathode electrode of the optical element 3 and the base member are joined via a conductive adhesive, and the vertical portion 4b of the base member 4 is further joined. Then, it was electrically connected to the ground electrode of the substrate 2 via the bump 7. As a result, the cathode electrode of the optical element 3 is electrically connected to the ground electrode of the substrate 2 via the base member 4 and the bump 7.

  As the base member 4, it is preferable to use a conductive material having high thermal conductivity. For example, Kovar (an alloy in which cobalt and nickel are mixed with iron) whose linear expansion coefficient is close to that of the optical element 3 may be used. . Moreover, in order to prevent Kovar corrosion, the surface may be plated with gold or the like. When using the optical element 3 of FIG.2 (b), it is not necessary to form the base member 4 with an electroconductive member.

  As shown in FIG. 4, in the optical transmission module 1, a lens block 41 is provided on the opposite side of the surface of the substrate 2 on which the flip chip mounting module 5 is mounted, and the optical fiber 42 is opposed to the lens block 41. And the optical fiber 42 and the optical element 3 are optically coupled via the lens block 41. The lens block 41 and the optical fiber 42 are supported by a support member (not shown) and the case housing 8.

  The operation of this embodiment will be described.

  In the optical transmission module 1 according to the present embodiment, the surface R opposite to the mounting surface of the optical element 3 is joined to the base member 4 to form the flip chip mounting module 5, and the flip chip mounting module 5 is mounted on the substrate. 2 is flip-chip mounted, and the flip-chip mounting module 5 is brought into contact with the case housing 8 to form a heat radiation path.

  Thereby, even if the optical element 3 for wire bonding which is not for flip chip mounting is used, flip chip mounting can be realized. By using the optical element 3 for wire bonding, the cost can be suppressed and the flip chip mounting can be realized, so that a good high frequency characteristic can be obtained.

  Further, by bringing the flip chip mounting module 5 into contact with the case housing 8, the heat generated in the optical element 3 can be radiated to the outside through the base member 4, the heat dissipation sheet, and the case housing 8. Thus, the optical transmission module 1 having excellent heat dissipation can be realized.

  Furthermore, since the flip chip mounting module 5 is formed by bonding the optical element 3 and the base member 4, handling becomes easy.

  In addition, the base member 4 is made of a conductive member, the optical element 3 and the base member 4 are joined via a conductive adhesive, and the base member 4 and the ground electrode of the substrate 2 are connected to the bumps 7. It is possible to use the optical element 3 (refer to FIG. 2A) in which the cathode electrode is formed on the surface R opposite to the mounting surface, and to further reduce the cost. it can.

  Next, another embodiment of the present invention will be described.

  An optical transmission module 51 shown in FIG. 5 is the same as the optical transmission module 1 shown in FIG. 1, and further, an IC 6 for driving the optical element 3 is joined to the base member 4 to form a flip chip mounting module 52. The flip chip mounting module 52 is flip-chip mounted by bump-connecting the electrodes, the base member 4 and the IC 6 to the substrate 2. In the parallel part 4a of the base member 4, a step is appropriately formed in order to make the mounting surface F of the optical element 3 and the height of the surface of the IC 6 on the substrate 2 side coincide with each other.

  According to the optical transmission module 51, since the optical element 3, the base member 4, and the IC 6 are integrally formed as the flip chip mounting module 52, handling is further facilitated, and the substrate 2 and the flip chip mounting module 52 are provided. Therefore, the optical element 3 can be mounted on the substrate 2 more stably.

  Since the IC 6 and the base member 4 are joined, not only the heat generated in the optical element 3 but also the heat generated in the IC 6 is radiated to the outside through the base member 4, the heat radiating sheet, and the case housing 8. Thus, the optical transmission module 51 having excellent heat dissipation can be realized.

  The optical transmission module 61 shown in FIG. 6 is obtained by eliminating the connection between the base member 4 and the substrate 2 except for the vertical portion 4b of the base member 4 in the optical transmission module 1 of FIG. That is, the optical transmission module 61 joins the optical element 3 to the base member 4 to form the flip chip mounting module 62, and bumps the electrodes of the optical element 3 to the substrate 2 to flip the flip chip mounting module 62. The optical device 3 is supported on the case housing 8 via the base member 4 by mounting the chip and fixing the base member 4 to the case housing 8.

  According to the light transmission module 61, similarly to the light transmission modules 1 and 51, the optical element 3 can be stably mounted on the substrate 2.

  Moreover, an example of the wiring pattern in the optical transmission module of this invention is shown to Fig.7 (a), (b). FIGS. 7A and 7B show the optical transmission module 51 of FIG. 5 as an example. FIG. 7C is a perspective view of the flip chip mounting module 52 of the optical transmission module 51.

  As shown in FIGS. 7A to 7C, a predetermined wiring pattern 91 is formed on the substrate 2, and the optical element 3 and the IC 6 are electrically connected via the wiring pattern 91. A large number of wiring patterns 91 for connecting to other elements and a power supply unit are connected to the IC 6. Further, the vertical portion 4 b of the base member 4 is connected to the ground electrode 92 of the substrate 2 through the bumps 7. Although not shown in FIGS. 7A and 7B, the flip chip mounting module 52 is configured to contact the case housing 8 through a heat dissipation sheet.

  The present invention is not limited to the above-described embodiments, but is interpreted as embodying all modifications and alternative configurations included in the scope of the basic teachings described in the present specification that can be conceived by those skilled in the art. Should be.

DESCRIPTION OF SYMBOLS 1 Optical transmission module 2 Board | substrate 3 Optical element 4 Base member 5 Flip chip mounting module 6 IC
7 Bump 8 Case housing

Claims (6)

  A substrate is housed in a case housing, and is an optical transmission module that flip-chip mounts an optical element having electrodes arranged in a row on a surface to be mounted on the substrate, opposite to the mounting surface of the optical element. A flip chip mounting module is formed by bonding a side surface to a base member, the flip chip mounting module is flip chip mounted on the substrate, and the flip chip mounting module is brought into contact with a case housing. An optical transmission module characterized in that a heat dissipation path is formed.   The optical transmission module according to claim 1, wherein the base member is brought into contact with the case casing via a heat dissipation sheet when the flip chip mounting module and the case casing are brought into contact with each other.   3. The optical transmission module according to claim 1, wherein the flip chip mounting of the flip chip mounting module is performed by bump-connecting the electrode of the optical element and the base member to the substrate.   The optical element is bonded to the base member, and further, an IC for driving the optical element is bonded to form the flip chip mounting module, and the flip chip mounting module is flip chip mounted. 3. The optical transmission module according to any one of 3.   The optical element has a cathode electrode formed on the surface opposite to the mounting surface, the base member is made of a conductive member, and the cathode electrode of the optical element and the base member are interposed via a conductive adhesive. The optical transmission module according to claim 1, wherein the base member and the ground electrode of the substrate are electrically connected via bumps.   The optical element is joined to the base member to form the flip chip mounting module, the electrodes of the optical element are bump-connected to the substrate, and the flip chip mounting module is flip chip mounted. The optical transmission module according to claim 1, wherein the optical transmission module is fixed to the case housing.

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