JP2009016631A - Semiconductor laser device and image forming device using it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a semiconductor laser device wherein the deterioration of an optical output and the thermal cross talk of a semiconductor laser element are improved by improving the heat dissipation efficiency of the semiconductor laser device. <P>SOLUTION: The semiconductor laser device includes the semiconductor laser element 1, a first submount 2 bonded to the substrate side of the semiconductor laser element 1 and a first heat sink 7 bonded to the backside of the first submount 2. A second submount 10 is bonded to a second heat sink 12, the second submount 10 is bonded to the semiconductor laser element 1, and the second heat sink 12 is bonded to the first heat sink 7. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a semiconductor laser device and an image forming apparatus using the same, and by using the semiconductor laser device that improves the heat dissipation effect of the semiconductor laser element and suppresses the output decrease due to thermal influence, and the semiconductor laser device. The present invention relates to an image forming apparatus that suppresses a decrease in image density caused by a decrease in output of laser light.

  In the semiconductor laser element, when electrical energy is converted into light energy, energy loss occurs and the energy is converted into thermal energy. When the temperature of the semiconductor laser element rises due to the generated thermal energy, an unfavorable effect on the laser characteristics occurs. Therefore, in order to dissipate heat generated in the semiconductor laser element and reinforce the strength of the semiconductor laser element, the substrate side of the semiconductor laser element is usually joined to the heat sink via a submount with a solder layer.

  The configuration of a conventional semiconductor laser device will be described with reference to FIGS. FIG. 1 is a perspective view of a first submount in the semiconductor laser device, FIG. 2 is a perspective view showing a state in which a semiconductor laser element is bonded to the first submount, and FIG. 3 shows a configuration of a main part of the semiconductor laser device. FIG. 4 is a side view showing the configuration of the main part of the semiconductor laser device.

  The conventional semiconductor laser device includes a semiconductor laser element 1, a submount 2 bonded to the substrate side of the semiconductor laser via a first solder layer 4, and a submount 2 via a second solder layer 8. And a heat sink 7 bonded to the back side. The electrode of the semiconductor laser element 1 and the electrode of the submount 2 are joined via the first solder layer 4, and the electrode of the submount 2 and the electrode pad 6 are wire bonded by a wire 5. Is connected to an external device via an electrode pad 6.

  The semiconductor laser element 1 is not limited to one semiconductor laser element, and a plurality of semiconductor laser elements may be arranged in an array. As the material of the submount 2, usually, copper tungsten (CuW), silicon carbide (SiC), or the like having a thermal expansion coefficient close to that of the semiconductor laser element is used.

  When manufacturing the semiconductor laser device, first, the semiconductor laser element 1 is placed on the solder layer 4 such as gold tin (AuSn) formed on the bonding surface of the submount 2 and the melting temperature of gold tin is 280 ° C. For example, the solder layer 4 is melted by heating at 300 ° C. or higher. Next, when the submount 2 is allowed to cool with the semiconductor laser element 1 mounted, the solder layer is solidified to become the first solder layer 4, and the submount 2 and the semiconductor laser element 1 can be joined. Subsequently, a thin plate of silver tin antimony (AgSnSb) is placed on the joining surface of the heat sink 7, and the submount 2 to which the semiconductor laser element 1 is joined is placed thereon, and the melting temperature of silver tin antimony is 233 ° C. or higher. For example, by heating at 250 ° C., gold tin antimony is melted. Next, when allowed to cool, the gold tin antimony is solidified to form the second solder layer 8, and the heat sink 7 and the submount 2 can be joined.

JP 2002-299744 A

  However, in the conventional semiconductor laser device, the heat generated in the semiconductor laser element is almost radiated through one surface where the semiconductor laser element and the submount are joined, and there is a limit to the reduction of the thermal resistance. A decrease in light output (droop) due to heat generated in the element has been a problem.

  In particular, in a semiconductor laser array in which a plurality of semiconductor lasers are arranged in an array, the amount of heat generated is large, and the heat generated by droop or one channel semiconductor laser element affects the optical output of other channels. Talk was a problem. In particular, when a semiconductor laser device is used as a writing light source for an electrophotographic image forming apparatus, a decrease in light output leads to a decrease in image density, which is one of the causes of image quality degradation.

  An object of the present invention is to greatly improve the heat dissipation efficiency of a semiconductor laser device, and to greatly improve the problems of optical output drop (droop) and thermal crosstalk of a semiconductor laser device, and droop and heat It is an object of the present invention to provide an image forming apparatus in which image quality is not deteriorated due to a decrease in image density caused by static crosstalk.

  In order to achieve the above object, a first means of the present invention includes a semiconductor laser element, a first submount bonded to the substrate side of the semiconductor laser element, and a back side of the first submount. In the semiconductor laser device having the first heat sink, the second submount is bonded onto the second heat sink, the second submount is bonded onto the semiconductor laser element, and the second heat sink is bonded to the second heat sink. A heat sink is bonded onto the first heat sink.

  According to a second means of the present invention, in the first means, the surface on which the second submount is bonded onto the semiconductor laser element, and the second heat sink are bonded onto the first heat sink. The surface is perpendicular to the surface.

  According to a third means of the present invention, in the first or second means, the semiconductor laser element is bonded onto the first submount via a first solder layer, and the first submount is The second submount is bonded to the first heat sink via the second solder layer, and the second submount is bonded to the second heat sink via the first or second solder layer. A submount is bonded to the semiconductor laser element via a third solder layer, and the second heat sink is bonded to the first heat sink via the third solder layer. To do.

  According to a fourth means of the present invention, in the third means, the melting point of the first solder layer is higher than the melting point of the second solder layer, and the melting point of the second solder layer is the third solder. It is characterized by being higher than the melting point of the layer.

  According to a fifth means of the present invention, in the first to fourth means, the first heat sink and the second heat sink are joined by laser welding.

  According to a sixth means of the present invention, in the first to fifth means, the semiconductor laser element is a semiconductor laser array.

  According to a seventh aspect of the present invention, a photosensitive member, an optical system that scans the photosensitive member with a beam emitted from a semiconductor laser device, and a latent image formed on the photosensitive member by scanning the beam are developed. A developing device that forms a toner image, a transfer device that transfers the developed toner image onto a recording medium, and a fixing device that fixes the toner image transferred onto the recording medium onto the recording medium; The semiconductor laser device is a semiconductor laser device of any one of the first to sixth means.

  The present invention has the configuration as described above, and greatly improves the heat dissipation efficiency of the semiconductor laser device, and greatly improves the problems of the optical output drop (droop) and thermal crosstalk of the semiconductor laser element. It is possible to provide a laser device and an image forming apparatus that does not deteriorate image quality due to a decrease in image density caused by droop or thermal crosstalk.

  In this embodiment, a case where a semiconductor laser array in which a plurality of semiconductor laser elements are arranged in an array is used as the semiconductor laser element 1 will be described.

  Bonding between the semiconductor laser element 1 and the first submount 2 will be described with reference to FIGS. The material of the submount 2 is silicon carbide (SiC), which is larger than the semiconductor laser element 1, and has 10 electrodes 3 equal to the sum of the electrodes of each element of the semiconductor laser element and the electrodes of the dummy element on one mounting surface. Is provided. Among the ten electrodes 3, four electrodes 3, which are each element, extend in parallel from one end of the submount 2, and the four electrodes 3 correspond to the elements of the semiconductor laser element 1. It faces the electrode. And the solder layer 4 is formed in the part facing each element and a dummy element. The solder layer 4 is made of, for example, gold tin (AuSn).

  The semiconductor laser element 1 is fixed by face-down bonding. In this face-down bonding, the electrodes of the semiconductor laser element 1 are positioned and overlapped on the solder layer, and the semiconductor laser element 1 is temporarily melted by heating at a temperature of 280 ° C. or higher, for example, 300 ° C., at which the gold-tin solder melts. Join to the submount 2.

  The electrode that supports the solder layer on which the electrodes of the respective elements of the semiconductor laser element 1 are overlapped is used as a wiring, and the wire 5 is connected. Therefore, this electrode extends outside the chip fixing region.

  The joining of the first submount 2 to which the semiconductor laser element 1 is joined to the first heat sink 7 will be described with reference to FIGS.

  The first heat sink 7 is made of copper (Cu) having a high thermal conductivity. A thin plate of silver tin antimony (AgSnSb) is placed on the surface where the first submount 2 of the first heat sink 7 is joined, and the first submount 2 is stacked thereon to dissolve the silver tin antimony (AgSnSb). The first submount 2 is bonded onto the first heat sink 7 by heating at 250 ° C., which is equal to or higher than 233 ° C., and temporarily melting and cooling.

  The electrode of the first submount 2 and the electrode pad 6 are wire-bonded by a wire 5, and the semiconductor laser element 1 is connected to an external device via the electrode pad 6.

  The joining between the second submount 10 and the upper surface of the semiconductor laser device 1 and the joining between the second heat sink 12 and the first heat sink 7 will be described with reference to FIGS. FIG. 5 is a front view showing the configuration of the main part of the semiconductor laser device according to the embodiment of the present invention, and FIG. 6 is a side view showing the configuration of the main part of the semiconductor laser device.

  The second heat sink 12 is made of copper, which is the same material as the first heat sink 7. A thin plate of gold tin (AuSn) is placed on the fixing position of the second submount 10 on the second heat sink 12, and the second submount 10 made of silicon carbide (SiC) is stacked thereon, It melts by heating at 280 ° C. or higher, for example, 300 ° C., at which tin (AuSn) dissolves. Thereafter, the second submount 10 and the second heat sink 12 are joined by cooling.

  Next, a silver indium film is deposited on the joint surface of the second heat sink 12 with the first heat sink 7. Thereafter, a silver indium thin plate is placed on the upper surface of the semiconductor laser element 1, and the surface on which the first heat sink 7 and the second heat sink 12 are in contact is slid to place the second submount 10 surface and the silver indium thin plate. The semiconductor laser element 1 is moved and fixed so as to be in contact with the upper surface of the semiconductor laser element 1. Then, by heating at 143 ° C. or higher, which is a temperature at which silver indium dissolves, for example, 200 ° C., silver indium is dissolved and cooled, the semiconductor laser element 1, the second submount 10, the second heat sink 12, 1 heat sink 7 is joined. Here, the second heat sink 12 and the first heat sink 7 may be joined by laser welding. Thereby, the effort which vapor-deposits silver indium on the joint surface with the 1st heat sink of a 2nd heat sink can be saved.

  As described above, the second heat sink 12 and the first heat sink 7 and the second submount 10 and the semiconductor laser device 1 have a structure in which the joint surface is perpendicular to the second heat sink 12 and the first heat sink 7. The bonding surface between the submount 10 and the semiconductor laser element 1 can be accurately overlapped, and the stress applied to the semiconductor laser element 1 due to thermal expansion can be relaxed. Further, by adopting such a structure, the heat capacity of the heat sink can be dispersed in the vertical direction of the semiconductor laser element 1, and the degree of freedom in designing the semiconductor laser device is increased, so that the semiconductor laser device can be reduced in size. .

Here, the thermal conductivity of GaAs, which is the material of the semiconductor laser element, is 54 (W / m · k), the thermal expansion coefficient is 6.5 (× 10 ⁻⁶ / ° C.), and the first and second submounts The thermal conductivity of SiC as the material is 270 (W / m · k), the thermal expansion coefficient is 3.7 (× 10 ⁻⁶ / ° C.), and the thermal conductivity of Cu as the material of the first and second heat sinks Is 390 (W / m · k), and the thermal expansion coefficient is 17.7 (× 10 ⁻⁶ / ° C.). The submount plays a role of absorbing stress generated due to a difference in thermal expansion coefficient between the heat sink and the semiconductor laser element.

  As shown in FIGS. 5 and 6, by adopting a structure that dissipates heat from the vertical direction of the semiconductor laser element 1, the junction area between the semiconductor laser element 1 and the submounts 2 and 10 is doubled, and the thermal resistance is reduced. The heat dissipation efficiency can be significantly improved.

  FIG. 7 shows a schematic diagram of an optical system when the semiconductor laser device of the present invention is used as the light source of the image recording apparatus of the present invention. The multi-beams emitted from the semiconductor laser element 1 in the semiconductor laser device of the present invention are converted into parallel light by the lens 14, deflected by the rotary polygon mirror 16, and optically scanned on the photosensitive drum 18 through the Fθ lens 17. . Since the distance between the light spot rows obtained on the photosensitive drum 18 is larger than the size of the light spot, the arrangement direction of the light spot rows is set obliquely with respect to the light scanning direction, and a close light scanning line is formed. I try to do it.

  A schematic configuration of the image forming apparatus of the present invention will be described with reference to FIG. The surface of the photosensitive drum 18 is charged by the charger 21 and light corresponding to the image is applied by the exposure device 22 to drop the potential on the photosensitive drum 18. The portion reaches the developing roller 24 by the rotation of the photosensitive drum 18, and when it comes into contact with the toner layer, the charged toner adheres to the image forming position and forms a toner image. The toner image on the photosensitive drum 18 is transferred onto the intermediate transfer belt 28 at a portion where the primary transfer roll 26 presses the intermediate transfer belt 28.

  The toner image on the photosensitive drum 18 of each developing unit is transferred onto the intermediate transfer belt 28 to form a color toner image. Then, the toner image is transferred onto the conveyed continuous paper 31 at the position of the transfer drum 30 in the contact area with the continuous paper 31 by the conveyance of the intermediate transfer belt 28. The continuous paper 31 to which the toner image has been transferred is subjected to heat and pressure by a fixing device 32, and the toner is melted and fixed to form a color image.

It is a perspective view of the 1st submount in a semiconductor laser device. It is a perspective view which shows the state which joined the semiconductor laser element to the 1st submount. It is a front view which shows the structure of the principal part of a semiconductor laser apparatus. It is a side view which shows the structure of the principal part of the semiconductor laser apparatus. It is a front view which shows the structure of the principal part of the semiconductor laser apparatus which concerns on embodiment of this invention. It is a side view which shows the structure of the principal part of the semiconductor laser apparatus. 1 is a schematic configuration diagram of an optical system of an image forming apparatus according to an embodiment of the present invention. 1 is a schematic configuration diagram of an image forming apparatus according to an embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Semiconductor laser element, 2 ... Submount, 3 ... Electrode, 4 ... 1st solder layer, 5 ... Wire, 6 ... Electrode pad, 7 ... 1st heat sink, 8 ... 2nd solder layer, 9 ... Photo Detector 10 ... 2nd submount 11 ... 3rd solder layer 12 ... 2nd heat sink 13 ... 3rd solder layer 14 ... lens 15 ... cylindrical lens 16 ... polygon mirror 17 ... Fθ Lens 18, photosensitive drum 19, drum cleaner 20, static eliminator 21, charger 22, exposure device 24, developing device 26, primary transfer roller 27, sensor 28, intermediate transfer belt 29 ... belt cleaner, 30 ... secondary transfer roller, 31 ... continuous paper, 32 ... fixing device, 33 ... paper holder before printing, 34 ... paper holder after printing.

Claims (7)

  In a semiconductor laser device comprising a semiconductor laser element, a first submount bonded to the substrate side of the semiconductor laser element, and a first heat sink bonded to the back side of the first submount, The second submount is bonded onto the second heat sink, the second submount is bonded onto the semiconductor laser element, and the second heat sink is bonded onto the first heat sink. A semiconductor laser device.   2. The semiconductor laser device according to claim 1, wherein a surface where the second submount is bonded onto the semiconductor laser element and a surface where the second heat sink is bonded onto the first heat sink. A semiconductor laser device characterized by being vertical.   3. The semiconductor laser device according to claim 1, wherein the semiconductor laser element is bonded onto the first submount via a first solder layer, and the first submount is mounted on the first heat sink. Bonded via a second solder layer, the second submount is bonded onto the second heat sink via the first or second solder layer, and the second submount is bonded to the semiconductor laser. A semiconductor laser device, wherein the semiconductor laser device is bonded onto an element via a third solder layer, and the second heat sink is bonded onto the first heat sink via the third solder layer.   4. The semiconductor laser device according to claim 3, wherein the melting point of the first solder layer is higher than the melting point of the second solder layer, and the melting point of the second solder layer is higher than the melting point of the third solder layer. A semiconductor laser device characterized by being expensive.   5. The semiconductor laser device according to claim 1, wherein the first heat sink and the second heat sink are joined by laser welding.   6. The semiconductor laser device according to claim 1, wherein the semiconductor laser element is a semiconductor laser array. A photoconductor, an optical system that scans the beam emitted from the semiconductor laser device on the photoconductor, and a developer that develops a latent image formed on the photoconductor by scanning the beam to form a toner image. An image forming apparatus comprising: a transfer unit that transfers a developed toner image onto a recording medium; and a fixing unit that fixes the toner image transferred onto the recording medium onto the recording medium.
7. The image forming apparatus according to claim 1, wherein the semiconductor laser device is the semiconductor laser device according to claim 1.

Images