JP2007027375A - Laser module - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain the laser module of the mounting structure for effectively radiating the generated heat of a semiconductor laser without shortening of the power feeding life of the semiconductor laser. <P>SOLUTION: The laser module is constituted by mounting a semiconductor laser element 6 on a first heat radiating block 4 provided on a stem 1 with one electrode layer 68 surface placed in contact with the heat radiating block 4. In this laser module, a second heat radiating block 8 electrically insulated from the stem 1 is provided on this stem 1, and a flexible heat conductive member 20 is also provided to thermally connect the other electrode layer 69 surface of the semiconductor laser element 6 and the second heat radiating block 8. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a laser module in which a semiconductor laser element is mounted on a heat dissipation block on a stem.

  2. Description of the Related Art Conventionally, a can-type sealed laser module in which a semiconductor laser element is mounted on a heat dissipation block disposed on a stem and a cap is put on and hermetically sealed is put into practical use. In a laser module in which a semiconductor laser element is mounted, represented by a can-type laser module, in general, one electrode surface of the semiconductor laser element is fixed to a heat dissipation block with solder, and heat generated when the semiconductor laser is driven A mounting structure that dissipates heat from one electrode surface is employed.

  In recent years, semiconductor laser devices having a large output have been provided gradually, and some of them having a very large calorific value have been developed. When the amount of heat generated by the semiconductor laser increases, if the heat generated cannot be sufficiently dissipated when the semiconductor laser is driven, deterioration of the semiconductor laser is promoted by the heat generation, and long-term reliability as a laser module cannot be obtained. A heat dissipation structure that radiates heat only from one electrode surface of the semiconductor laser element may not provide sufficient heat dissipation, and improvement of the heat dissipation structure is required.

As a method for improving the heat dissipation, for example, as disclosed in Non-Patent Document 1, a groove is provided in a heat sink, a semiconductor laser is inserted into the groove, and a gap between both sides of the semiconductor laser and the groove is filled with solder. Therefore, a configuration in which heat is radiated from both sides of the semiconductor laser is considered.
Laser Physics, 1998, Vol. 8, No. 3, p. 737-740 (Laser physics, Vol. 8, No. 3, 1998, pp. 737-740)

  However, in the apparatus of Non-Patent Document 1, since the heat sink in which the groove is formed and the semiconductor laser loaded in the groove are both rigid bodies and there is a difference in thermal expansion coefficient, The semiconductor laser may be thermally strained by the influence of expansion and the like, and stress may be applied to the active layer, which may significantly shorten the energization life of the semiconductor laser.

  In view of the above circumstances, an object of the present invention is to provide a laser module that can efficiently dissipate heat generated by a semiconductor laser without shortening the energization life of the semiconductor laser.

The laser module of the present invention is a laser module in which a semiconductor laser element is mounted on a first heat dissipation block disposed on a stem so that one electrode layer surface is in contact with the heat dissipation block.
A second heat dissipating block electrically insulated from the stem is disposed on the stem;
A flexible heat conducting member is provided for thermally connecting the other electrode layer surface of the semiconductor laser element and the second heat radiation block.

  The heat conducting member is preferably in the form of a sheet or film. Here, the sheet or film shape may be not only a member having a uniform thickness, but also a wire-like heat conducting member knitted into a mesh shape and formed into a sheet shape.

  The heat conducting member is preferably in contact with the other electrode layer surface in as wide a range as possible. For example, it is preferably in contact with at least half of the other electrode layer surface, particularly with the entire surface. The heat conducting member is flexible and has any thermal conductivity higher than that of the substrate of the semiconductor laser, and any material that can conduct heat generated from the semiconductor laser to the second heat radiating block. It may be configured.

  Further, it is desirable that the heat conducting member has conductivity that can be used as a conducting wire. As the heat conducting member, for example, a graphite thin film can be used. It is desirable that the heat conducting member also serves as a drive current injection terminal for the semiconductor laser element.

  As the semiconductor laser element, for example, a GaN semiconductor laser can be used.

  According to the laser module of the present invention, one electrode layer surface of the semiconductor laser element is fixed in contact with the first heat dissipation block, and the flexible heat that thermally connects the other electrode layer and the second heat dissipation block. Compared to the conventional case where one electrode layer is soldered to the heat dissipation block and heat is radiated from only one of the electrode layers because it has a conductive member and can radiate heat from both electrode layers of the semiconductor laser element. Thus, the heat dissipation efficiency can be improved. In addition, one electrode layer of the semiconductor laser element is fixed in contact with a rigid heat dissipation block, but the other electrode layer is in contact with a flexible member. Even when the element is thermally expanded, the semiconductor laser element is not subjected to stress (thermal strain), so there is no possibility of shortening the life of the semiconductor laser element. That is, according to the laser module of the present invention, the heat radiation efficiency can be improved without causing the semiconductor laser element to deteriorate due to thermal strain.

  If the heat conducting member is in the form of a sheet or film, the contact area with the electrode layer of the semiconductor laser element can be made sufficiently large, and heat can be effectively radiated.

  Furthermore, if the heat conducting member is in contact with the entire surface of the other electrode layer surface of the semiconductor laser element, heat radiation is more efficiently performed.

  If the heat conducting member has conductivity that can be used as a conducting wire, it can also be used as a drive current injection terminal to the semiconductor laser element, and wire bonding is not required, and a simple configuration can be achieved.

  If the heat conductive member is a graphite thin film, the heat conductivity is high and the electric conductivity is high, so that the heat dissipation efficiency can be improved and it can be used as a drive current injection terminal.

  When the semiconductor laser element is a GaN-based semiconductor laser, since the amount of heat generation is particularly large, the effect of applying the present invention is great.

  Embodiments of the present invention will be described below. FIG. 1 is a schematic configuration diagram of a can-type sealed laser module according to a first embodiment of the invention, and FIG. 2 is a top view of a semiconductor laser element mounting portion of the laser module shown in FIG.

  As shown in FIGS. 1 and 2, the laser module includes a first heat radiation block 4 including a heat sink 4a and a submount 4b on a stem 1 from which three wiring pins 11, 12, and 13 protrude downward. A second heat radiation block 8 that is electrically insulated from the stem 1 and electrically connected to the wiring pin 11 is fixed, and the semiconductor laser element 6 is disposed on the surface of one electrode layer 68 on the submount 4b. Is mounted so as to be in contact with the submount 4b, and further includes a flexible heat conducting member 20 that thermally connects the other electrode layer 69 of the semiconductor laser element 6 and the second heat radiation block 8. Yes. A monitoring photodiode 10 for monitoring the output of the semiconductor laser element 6 is disposed on the stem 1, and each element disposed on the stem 1 includes a glass window 3 on which a non-reflective coating is applied. The cap 2 is covered and hermetically sealed. The cap 2 is degassed inside, and is fixed to the stem 1 by resistance welding or the like while being filled with an inert gas. In FIG. 1, the front half of the cylindrical cap 2 is not shown in order to facilitate the understanding of the configuration of each element in the cap 2.

  The wiring pin 12 is electrically connected to the stem 1 and is electrically connected to one electrode layer 68 of the semiconductor laser element 6 through the heat sink 4a and the submount 4b. The wiring pin 13 protrudes from the upper surface of the stem 1 while being electrically insulated from the stem 1, and is connected to the photodiode 10 by a wire 17. The wiring pin 11 is connected to the second heat dissipation block 8 on the stem 1 while being electrically insulated from the stem 1. The lower part of the second heat radiation block 8 may be processed into a wiring pin shape, and the heat radiation block 8 and the wiring pin 11 may be integrally formed of one member. Insulation between the wiring pins 11 and 13 and the stem 1 can be achieved by a method of filling between the through holes provided in the stem 1 and the wiring pins 11 and 13 with insulating materials 14 and 15 such as low melting point glass.

As shown in FIG. 2, the semiconductor laser device 6 includes an n-type AlGaN clad layer 62, a multiple quantum well layer (MQW layer) 63, a p-type AlGaN clad layer 64, and a p-type that are sequentially epitaxially grown on an n-type GaN substrate 61. This is a ridge type semiconductor laser including a GaN cap layer 66 and having a ridge portion provided in part of the p-type GaN cap layer 66 and the p-type AlGaN cladding layer 64. An insulating portion 65 made of SiO ₂ is formed on both sides of the ridge portion, a p-side electrode layer 69 is formed so as to cover the insulating portion 65 and the ridge portion, and an n-side electrode layer 68 is formed on the back surface of the substrate 61. Is formed. The semiconductor laser element 6 is soldered with a brazing material 31 so that the n-side electrode layer 68 contacts the submount 4b which is a part of the first heat radiation block 4, and the upper surface of the p-side electrode layer 69 is The heat conductive member 20 is disposed so as to be in contact with the entire surface of the p-side electrode layer 69 and soldered by the brazing material 32.

  As the heat conducting member 20, a sheet-like member made of graphite is used. One end of the sheet-like heat conducting member 20 is soldered to the entire surface of the electrode layer 69 of the semiconductor laser element 6, and the other end is the first. The heat radiating block 8 is soldered with a brazing material 33. The thermal conductivity of graphite is 600-800 W / m · K, which is about four times the thermal conductivity of Cu (copper) often used as a heat dissipation block. In order to solder a sheet-like heat conductive member (hereinafter referred to as a graphite sheet) 20 made of graphite to the electrode layer 69 and the second heat sink, the surface of the graphite sheet 20 is Au (gold), Au / Cr. (Chromium) or Au / Ti (titanium) is sputter deposited. Further, since graphite has conductivity that can be used as a conducting wire, the heat conducting member 20 also serves as a terminal for supplying power to the semiconductor laser element 6 (terminal for driving current injection). In general, wiring pins and electrode layers are connected by wires such as Au in order to feed power to the electrode layer 69 of the semiconductor laser element 6, but here, the graphite sheet 20 can be used as a power feeding terminal. Wire bonding is unnecessary.

  In the laser module of this embodiment, one electrode layer 68 of the semiconductor laser element 6 is fixed in contact with the first heat dissipation block 4 and the other electrode layer 69 is connected to the second heat dissipation block 8 in a flexible manner. Since the heat conductive member 20 is fixed and heat can be dissipated from both electrode layers 68 and 69, heat can be efficiently dissipated. In particular, in the case of a semiconductor laser that generates a large amount of heat, such as the GaN-based semiconductor laser mounted here, the effect of suppressing the shortening of the life of the semiconductor laser element due to efficient heat dissipation is great. In addition, one electrode layer 68 of the semiconductor laser element 6 is joined to the rigid heat dissipation block 4, but the other electrode layer 69 is joined to the flexible member 20, so that heat is generated even during heat generation. There is no risk of shortening the life of the semiconductor laser element without receiving stress such as strain.

  In addition, a laser module can be comprised at low cost by comprising the stem 1 with a Fe (iron) -based material and the first heat radiation block 4 and the second heat radiation block 8 with Cu (copper).

  In the laser module according to the present embodiment, laser light 7 which is forward emission light of the semiconductor laser element 6 is emitted from the window glass 3 coated with non-reflective coating, and the backward emission light of the semiconductor laser element 6 is emitted from the monitor photodiode. The amount of emitted light is sensed by 10 and the current is automatically controlled so that the output of the laser beam 7 is constant.

  The flexible heat conducting member 20 is not limited to the above-described graphite sheet, and the electrode layer 69 of the semiconductor laser element 6 and the second heat radiation block 8 are thermally connected, and the heat of the semiconductor laser element 6 is increased. As long as it can conduct heat to the heat radiating block 8 and radiate heat, specifically, it should have higher thermal conductivity than the substrate 61 of the semiconductor laser element 6 (GaN in the above embodiment). That's fine. In the above embodiment, the heat conducting member 20 is in contact with the entire surface of the electrode layer of the semiconductor laser. However, the heat conducting member is not necessarily in contact with the entire surface of the electrode layer, and is about half the area of the electrode layer. If it is more than it, the heat dissipation effect can fully be acquired.

  FIG. 3 is a diagram showing a schematic configuration of a laser module according to the second embodiment of the present invention. In the following, the same elements as those of the laser module of the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

  This laser module is different from the laser module of the first embodiment in that the heat conducting member 21 is made of a material that does not have conductivity that can be used as a conducting wire. Examples of the material having high thermal conductivity and low electrical conductivity include diamond, and the thermal conductive member 21 is a diamond sheet, a diamond thin film synthesized by vapor phase, or a flexible support sheet obtained by depositing diamond. Can be used. In this case, since the heat conducting member 21 does not have sufficient conductivity, it cannot be used as a drive current injection terminal. Therefore, an Au wire 16 for connecting the electrode layer 69 of the semiconductor laser element 6 and the second heat dissipation block 8 is provided, and drive current injection into the electrode layer 69 of the semiconductor laser element 6 is performed by the Au wire 16. Yes. A part of the electrode layer 69 of the semiconductor laser element 6 requires a wire bonding space, and the heat conducting member 21 is soldered to the other region.

  FIG. 4 is a diagram showing a schematic configuration of a laser module according to the third embodiment of the present invention.

  This laser module is different from the first embodiment in that the second heat dissipation block 18 is not connected to the wiring pin 11 'and is disposed on the stem 1 independently of the wiring pin 11'. The second heat dissipation block 18 is fixed on the stem 1 via an insulating sheet 19.

  The heat conducting member 22 used here may be any member that is capable of thermally connecting the electrode layer 69 of the semiconductor laser 6 and the second heat dissipating block 18 to dissipate heat generated by the semiconductor laser element. Does not matter. The heat conducting member 22 of this embodiment is used only for heat dissipation, and the heat conducting member 22 is not used as a terminal for driving current injection. Therefore, a wire 16 for connecting the wiring pin 11 ′ and the electrode layer 69 is provided for feeding power to the semiconductor laser element 6. The wiring pin 11 'penetrates the stem 1 and is protruded on the stem 1 while being electrically insulated from the stem 1 by an insulating material 14 such as low melting point glass, and a wire 16 is connected to the protruding portion. Has been.

  As described above, also in the laser module of the second or third embodiment, one electrode layer 68 of the semiconductor laser element 6 is the first heat dissipation block 4 and the other electrode layer 69 is the flexible heat conducting member 21. Alternatively, since it is connected to 22 and radiates heat from both electrode layers 68 and 69, heat can be efficiently radiated, and one electrode layer 68 is joined to the heat radiating block 4 which is a rigid body. Since the other electrode layer 69 is bonded to the flexible member 21 or 22, the semiconductor laser element 6 is not subjected to stress such as thermal strain even during heat generation, and the life of the semiconductor laser element is shortened. There is no fear.

The figure which shows schematic structure of the laser module of 1st Embodiment. 1 is a top view of a semiconductor laser element mounting portion of the laser module shown in FIG. The figure which shows schematic structure of the laser module of 2nd Embodiment. The figure which shows schematic structure of the laser module of 3rd Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Stem 2 Cap 3 Window glass 4 1st thermal radiation block 4a Heat sink 4b Submount 6 Semiconductor laser element 7 Laser beam 8 2nd thermal radiation block
10 Photodiode for monitor
11, 12, 13 Wiring pin
20, 21, 22 Thermal conductive member
31, 32 Solder material
68 n-side electrode layer (one electrode layer)
69 p-side electrode layer (the other electrode layer)

Claims (7)

In a laser module in which a semiconductor laser element is mounted on a first heat dissipation block disposed on a stem so that one electrode layer surface is in contact with the heat dissipation block,
A second heat dissipating block electrically insulated from the stem is disposed on the stem;
A laser module comprising a flexible heat conducting member for thermally connecting the other electrode layer surface of the semiconductor laser element and the second heat dissipation block.   The laser module according to claim 1, wherein the heat conducting member is in the form of a sheet or a film.   3. The laser module according to claim 1, wherein the heat conducting member is in contact with the entire surface of the other electrode layer.   The laser module according to claim 1, wherein the heat conducting member has conductivity that can be used as a conducting wire.   5. The laser module according to claim 1, wherein the heat conducting member is made of a graphite thin film.   6. The laser module according to claim 1, wherein the heat conducting member also serves as a drive current injection terminal to the semiconductor laser element.   7. The laser module according to claim 1, wherein the semiconductor laser element is a GaN semiconductor laser.

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