Abstract:
A semiconductor laser device includes: a semiconductor laser; a carrier that has a carrier side face facing with a longitudinal direction of the semiconductor laser, has a carrier edge area, and has a first bonding area that is the closest to a first end of the semiconductor laser and a second bonding area that is the closet to a second end of the semiconductor laser; a first thermal conduction portion that has a first thermal resistance and couples between the first bonding area and an outer connection terminal; and a second thermal conduction portion that has a second thermal resistance smaller than the first thermal resistance and couples between the second bonding area and an outer connection terminal, wherein the first end side of the semiconductor laser is closer to the carrier side face than the second end side of the semiconductor laser.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    The present application is a continuation of and claims priority to International Patent Application No. PCT/JP2009/071266 filed on Dec. 22, 2009, which claims priority to Japanese Patent Application No. 2008-333510 filed on Dec. 26, 2008, subject matter of these patent documents is incorporated by reference herein in its entirety. 
     
    
     BACKGROUND 
       [0002]    (i) Technical Field 
         [0003]    A certain aspect of the embodiments discussed herein is related to a semiconductor laser device. 
         [0004]    (ii) Related Art 
         [0005]    In a semiconductor laser device, a semiconductor chip and am interconnection metal are provided on a carrier, and a plurality of wirings are coupled to the semiconductor chip in order to provide a current and a voltage to the semiconductor chip. The semiconductor chip is therefore thermally coupled to an outer component through the wirings. In the semiconductor laser device, the carrier is provided on a temperature control device, and the temperature control device controls a temperature of the semiconductor chip. 
         [0006]    In the semiconductor laser device, distances between bonding areas of an interconnection metal and the semiconductor laser are hardly different from each other. Therefore, thermal flow amount through each wiring is hardly different from each other, even if outer temperature changes. Therefore, a carrier surface near the semiconductor chip is hardly subjected to the outer temperature. And temperature distribution is kept even. 
       SUMMARY 
       [0007]    According to an aspect of the present invention, there is provided a semiconductor laser device comprising: a semiconductor laser; a carrier that has a carrier side face facing with a longitudinal direction of the semiconductor laser, has a carrier edge area having a given width from the carrier side face and extending in parallel with the carrier side face, and has a first bonding area that is the closest to a first end of the semiconductor laser on the carrier edge area and a second bonding area that is the closet to a second end of the semiconductor laser on the carrier edge area, the side face being one of sides of the carrier; a first thermal conduction portion that has a first thermal resistance and couples between the first bonding area and an outer connection terminal; and a second thermal conduction portion that has a second thermal resistance smaller than the first thermal resistance and couples between the second bonding area and an outer connection terminal, wherein: the semiconductor laser is mounted on the carrier; and the first end side of the semiconductor laser is closer to the carrier side face than the second end side of the semiconductor laser. 
         [0008]    According to an aspect of the present invention, there is provided a semiconductor laser device comprising: a semiconductor laser; a carrier that has a carrier side face facing with a longitudinal direction of the semiconductor laser, has an area extending in parallel with the longitudinal direction of the semiconductor laser, and has a first bonding area that is the closest to a first end of the semiconductor laser on the area and a second bonding area that is the closet to a second end of the semiconductor laser on the area, the side face being one of sides of the carrier; a first thermal conduction portion that couples between the first bonding area and an outer connection terminal; and a second thermal conduction portion that has substantially the same thermal resistance as the first thermal conduction portion and couples between the second bonding area and an outer connection terminal, wherein: the semiconductor laser is mounted on the carrier; and the first end side of the semiconductor laser is closer to the carrier side face than the second end side of the semiconductor laser. 
         [0009]    According to an aspect of the present invention, there is provided a semiconductor laser device comprising: a semiconductor laser; a carrier that has a carrier side face facing with a longitudinal direction of the semiconductor laser, has a carrier edge area having a given width from the carrier side face and extending in parallel with the carrier side face, has a first bonding area that is the closest to a first end of the semiconductor laser on the carrier edge area and a second bonding area that is the closet to a second end of the semiconductor laser on the carrier edge area and has a third bonding area that is positioned on the semiconductor laser side compared to the carrier edge area, the side face being one of sides of the carrier; a first thermal conduction portion that has a first thermal resistance and couples between the first bonding area and an outer connection terminal; a second thermal conduction portion that has a second thermal resistance smaller than the first thermal resistance and couples between the second bonding area and an outer connection terminal; and a third thermal conduction portion that couples between the third bonding area and an outer connection terminal, wherein: the semiconductor laser is mounted on the carrier; and the first end side of the semiconductor laser is closer to the carrier side face than the second end side of the semiconductor laser. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]      FIG. 1  illustrates schematic view of a module in which a semiconductor chip is arranged to be inclined; 
           [0011]      FIG. 2  illustrates a schematic view of the problem; 
           [0012]      FIG. 3A  and  FIG. 3B  illustrate a principle of the invention; 
           [0013]      FIG. 4  illustrates a schematic view of a semiconductor laser device in accordance with a first embodiment; 
           [0014]      FIG. 5  illustrates a schematic view of a semiconductor laser device in accordance with a second embodiment; 
           [0015]      FIG. 6  illustrates a schematic view of a semiconductor laser device in accordance with a third embodiment; 
           [0016]      FIG. 7  illustrates a schematic view of a semiconductor laser device in accordance with a fourth embodiment; 
           [0017]      FIG. 8  illustrates a schematic view of a semiconductor laser device in accordance with a fifth embodiment; 
           [0018]      FIG. 9  illustrates a schematic view of a semiconductor laser device in accordance with a sixth embodiment; and 
           [0019]      FIG. 10A  and  FIG. 10B  illustrate an enlarged view of an interconnection metal provided on a carrier. 
       
    
    
     DETAILED DESCRIPTION 
       [0020]    In a semiconductor laser device in which a semiconductor chip is mounted on a carrier and is inclined with respect to the carrier, distances between the semiconductor chip and bonding areas of an interconnection metal are different from each other. Therefore, thermal flow amount between outside and near the semiconductor chip in a case where the semiconductor chip is closer to the bonding area is different from that in a case where the semiconductor chip is farther from the bonding area, even if the lengths of the wirings are equal to each other. Therefore, the surface temperature of the carrier near the semiconductor chip is distributed disproportionately if the outer temperature changes. 
         [0021]    In the semiconductor laser device, it is not possible to equalize the temperature distribution of the carrier surface near the semiconductor chip, because a temperature control device can control only an average temperature of the carrier. 
         [0022]      FIG. 1  illustrates a schematic view of a module  900  in which a semiconductor chip is arranged to be inclined. As illustrated in  FIG. 1 , in the module  900 , a carrier  920  is provided on a temperature control device  910  in a package  901 . A semiconductor laser  930  is provided on the carrier  920 . The carrier  920  has a carrier side face facing with a longitudinal direction of a semiconductor laser  930 . A first end of the semiconductor laser  930  is closer to the carrier side face of the carrier  920  than a second end of the semiconductor laser  930 . Thus, the semiconductor laser  930  is arranged to be inclined with respect to the carrier  920 . The semiconductor laser  930  is coupled to an outer device through wirings  960  to  962  and outer connection terminals  970  to  972  from interconnection metals  940  to  942  on the carrier  920 . 
         [0023]      FIG. 2  illustrates a schematic view of the problem. The carrier  920  is mounted on the temperature control device  910  in a module  990 . The semiconductor laser  930  is mounted on the carrier  920  and is arranged to be inclined with respect to the carrier  920 . The semiconductor laser  930  is coupled to an outer connection terminal through the wirings  960  and  962 . The carrier  920  has areas  950  and  952  where a wiring is bonded to a interconnection metal. The areas are hereinafter referred to as a bonding area. The bonding areas  950  and  952  have a bonding pad and so on. The temperature control device  910 , the carrier  920 , the semiconductor laser  930  and the wirings  960  and  962  are the same as those of  FIG. 1 . 
         [0024]    In the module  990  of  FIG. 2 , an area A on the first end side of the semiconductor laser  930  has a distance “a” from the bonding area  950 , and an area B on the second end side of the semiconductor laser  930  has a distance “b” from the bonding area  952 . In  FIG. 2 , the distance “a” is shorter than the distance “b”. In this case, the area A is more subjected to outer heat than the area B if thermal flow amount toward or from outside through the wirings  960  and  962  is equal to each other. For example, output wavelength may not be stable because temperature difference between the area A and the area B of the semiconductor laser is 0.1 degrees C. or more. 
         [0025]    The thermal flow toward or from outside through the wirings  960  and  962  is different from each other, when the distance from the bonding areas  950  and  952  to the outer connection terminal is different from each other, even if the distance between the area A and the bonding area  950  is the same as that between the area B and the bonding area  952 . Therefore, one of the areas A and B is subjected to the outer heat more than the other. 
         [0026]    A description will be given of a principle of the present invention. 
         [0027]      FIG. 3A  and  FIG. 3B  illustrate the principle of the invention. As illustrated in  FIG. 3A , a module  90  has a structure in which a carrier  20  is mounted on a temperature control device  10 . A semiconductor laser  30  is mounted on the carrier  20  and is arranged to be inclined with respect to the carrier  20 . The semiconductor laser  30  is coupled to an outer connection terminal through a bonding area  50  on the carrier  20  and a wiring  60 , and is coupled to another outer connection terminal through a bonding area  52  on the carrier  20  and a wiring  62 . 
         [0028]    In the module  90 , the area A on the first end side of the semiconductor laser  30  has a distance “a” from the bonding area  50 , and the area B on the second end side of the semiconductor laser  30  has a distance “b” from the bonding area  52 . In  FIG. 3A , the distance “a” is shorter than the distance “b”. In this case, the area A is more subjected to heat than the area B, if the thermal flow toward or from outside through the wirings  60  and  62  is equal to each other. 
         [0029]    And so, thermal flow through the wiring  62  coupled to the bonding area  52  is adjusted to be more than thermal flow through the wiring  60  coupled to the bonding area  50 . Alternatively, the thermal flow through the wiring  60  coupled to the bonding area  50  is adjusted to be less than the thermal from through the wiring  62  coupled to the bonding area  52 . In this case, temperature distribution of the surface of the carrier  20  near the semiconductor laser  30  caused by the difference of the distances between the semiconductor laser  30  and the bonding areas  50  and  52  may be restrained. 
         [0030]    The present invention may be applied to a case where the distances between the semiconductor laser and the bonding areas are equal to each other. As illustrated in  FIG. 3B , a module  91  has a structure in which the carrier  20  is mounted on the temperature control device  10 . The semiconductor laser  30  is mounted on the carrier  20  and is arranged to be inclined with respect to the carrier  20 . The semiconductor laser  30  is coupled to outer connection terminals through the bonding areas  50  and  52  and the wirings  60  and  62 . 
         [0031]    In the module  91 , the area A on the first end side of the semiconductor laser  30  has a distance “a 1 ” from the bonding area  50 , and the area B on the second end side of the semiconductor laser  30  has a distance “b 1 ” from the bonding area  52 . In  FIG. 3B , the distance “a 1 ” and the distance “b 1 ” are set to be substantially equal to each other. 
         [0032]    However, in this case, a wiring  72  coupling between the bonding area  52  and an outer connection terminal is longer than a wiring  70  coupling between the bonding area  50  and an outer connection terminal. In this case, thermal resistance of the wiring  70  is smaller than that of the wiring  72 . Therefore, the area A is more subjected to heat than the area B. And so, the thermal flow through the wiring  72  coupled to the bonding area  52  is adjusted to be equal to the thermal flow through the wiring  70  coupled to the bonding area  50 . Therefore, the temperature distribution of the surface of the carrier  20  near the semiconductor laser  30  is restrained. 
         [0033]    A description will be given of embodiments of the present invention. 
       First Embodiment 
       [0034]      FIG. 4  illustrates a schematic view of a semiconductor laser device  100  in accordance with a first embodiment. As illustrated in  FIG. 4 , the semiconductor laser device  100  has a structure in which a temperature control device  110  is mounted on a package  101 , a carrier  120  is provided on the temperature control device  110 , a semiconductor laser  130  is mounted on the carrier  120 . 
         [0035]    The carrier  120  has a rectangular shape and has a carrier side face facing with a longitudinal direction of the semiconductor laser  130 . In  FIG. 4 , the carrier side face is lower side of the carrier  120 . The semiconductor laser  130  is mounted on the carrier  120 . The first end side of the semiconductor laser  130  is closer to the carrier side face than the second end side of the semiconductor laser  130 . Thus, the semiconductor laser  130  is arranged to be inclined with respect to the carrier  120 . In  FIG. 4 , the first end of the semiconductor laser  130  is right end, and the second end of the semiconductor laser  130  is left end. 
         [0036]    The semiconductor laser  130  is coupled to outer connection terminals  170  to  172  through interconnection metals  140  to  142  and wirings  160  to  162 . The interconnection metals  140  to  142  respectively have bonding areas  150  to  152  on the opposite side of the semiconductor laser  130 . The bonding areas  150  to  152  have a bonding pad and so on. 
         [0037]    Here, on the carrier  120 , an area having a given width and extending from the carrier side face in parallel with the carrier side face is hereinafter referred to as a carrier edge area. In the embodiment, the bonding areas  150  to  152  are positioned on the carrier edge area. The bonding area  150  is an area of the carrier edge area that is the closest to the first end of the semiconductor laser  130 . The bonding area  152  is an area of the carrier edge area that is the closest to the second end of the semiconductor laser  130 . The bonding area  151  is positioned between the bonding area  150  and the bonding area  152  on the carrier edge area. 
         [0038]    The wirings  160  to  162  respectively couples the bonding areas  150  to  152  and the outer connection terminals  170  to  172 . In the embodiment, the wiring  160  is longer than the wiring  162 . The wiring  161  is shorter than the wiring  160  and is longer than the wiring  162 . 
         [0039]    In the embodiment, the distance “a” between the semiconductor laser  130  and the bonding area  150  is shorter than the distance “b” between the semiconductor laser  130  and the bonding area  152 . In this case, the first end side of the semiconductor laser  130  is more subjected to thermal flow through a wiring than the second end side. However, thermal resistance of the wiring  160  is larger than that of the wiring  162  because the wiring  160  is longer than the wiring  162 . In this case, thermal influence on the first end side of the semiconductor laser  130  from outside is restrained. It is therefore possible to equalize the thermal flow toward or from outside on an area near the semiconductor laser  130 . Accordingly, the temperature distribution on the surface of the carrier  120  is restrained. 
         [0040]    The temperature distribution on the surface of the carrier  120  is more restrained, because the distance “c” between the semiconductor laser  130  and the bonding area  151  is between the distance “a” and the distance “c”, and the length of the wiring  161  is between the wiring  160  and the wiring  162 . 
         [0041]    When the distances “a” to “c” are approximately 0.6 mm, 1.0 mm and 1.7 mm, the wiring  160  has a length of approximately 3.3 mm, the wiring  161  has a length of approximately 2.2 mm, the wiring  162  has a length of approximately 1.3 mm, and a cross-section area of the wirings  160  to  162  is approximately 0.00070 mm 2 . The carrier  120  is made of aluminum nitride. The interconnection metals  140 ,  141  and  142  are made of gold or the like. 
         [0042]    An optical component such as a lens may be mounted on an optical axis in front of the semiconductor laser  130  and behind the semiconductor laser  130 . 
       Second Embodiment 
       [0043]      FIG. 5  illustrates a schematic view of a semiconductor laser device  200  in accordance with a second embodiment. The semiconductor laser device  200  is different from the semiconductor laser device  100  in points that a wiring  261  is provided instead of the wiring  161 , and an outer connection terminal  271  is provided instead of the outer connection terminal  171 . In the embodiment, the outer connection terminal  271  is positioned so that the wiring  261  has the same length as the wiring  162 . 
         [0044]    In the embodiment, the thermal resistance of the wiring  160  is larger than that of the wiring  162 , because the wiring  160  is longer than the wiring  162 . It is therefore possible to equalize the thermal flow toward or from outside on the area near the semiconductor laser  130 . Accordingly, the temperature distribution of the surface of the carrier  120  is restrained. 
       Third Embodiment 
       [0045]      FIG. 6  illustrates a schematic view of a semiconductor laser device  300  in accordance with a third embodiment. As illustrated in  FIG. 6 , the semiconductor laser device  300  is different from the semiconductor laser device  100  of  FIG. 4  in points that a wiring  360  is provided instead of the wiring  160 , wirings  361  and  362  are provided instead of the wiring  161 , wirings  363  to  367  are provided instead of the wiring  162 , and outer connection terminals  370  and  371  are provided instead of the outer connection terminals  170  and  171 . Thus, in the embodiment, the bonding area  150  is coupled to the outer connection terminal  370  with a single wiring, the bonding area  151  is coupled to the outer connection terminal  371  with two wirings, and the bonding area  152  is coupled to the outer connection terminal  172  with five wirings. 
         [0046]    In this case, the thermal resistance between the bonding area  151  and the outer connection terminal  171  is larger than that between the bonding area  152  and the outer connection terminal  172 . The thermal resistance between the bonding area  150  and the outer connection terminal  170  is smaller than that between the bonding area  151  and the outer connection terminal  171 . It is therefore possible to equalize the thermal flow toward or from outside on the area near the semiconductor laser  130 . Accordingly, the temperature distribution of the surface of the carrier  120  is restrained. 
         [0047]    The positions of the outer connection terminals  370 ,  371  and  172  may be adjusted according to each thermal resistance between the bonding areas and the outer connection terminals. In this case, the temperature distribution of the surface of the carrier  120  is more restrained. 
         [0048]    For example, when the distances “a” to “c” are respectively 0.8 mm, 1.8 mm and 1.3 mm approximately, the lengths of the wirings  360  to  367  are approximately 1.9 mm, and the cross-section area of the wirings  360  to  367  is approximately 0.00070 mm 2 . 
       Fourth Embodiment 
       [0049]      FIG. 7  illustrates a schematic view of a semiconductor laser device  400  in accordance with a fourth embodiment. As illustrated in  FIG. 7 , the semiconductor laser device  400  is different from the semiconductor laser device  100  in points that wirings  460  to  462  are provided instead of the wirings  160  to  162 , and outer connection terminals  470  to  472  are provided instead of the outer connection terminals  170  to  172 . 
         [0050]    In the embodiment, the cross-section area of the wiring  461  is smaller than that of the wiring  462 , and the cross-section area of the wiring  460  is smaller than that of the wiring  461 . Thus, the thermal resistance of the wiring  461  is larger than that of the wiring  462 , and the thermal resistance of the wiring  460  is larger than that of the wiring  461 . It is therefore possible to equalize the thermal flow toward or from outside on the area near the semiconductor laser  130 . Accordingly, the temperature distribution of the carrier  120  is restrained. 
         [0051]    The positions of the outer connection terminals  470  to  472  may be adjusted according to each thermal resistance between the bonding areas and the outer connection terminals. In this case, the temperature distribution of the surface of the carrier  120  is more restrained. 
         [0052]    For example, when the distances “a” to “c” are respectively 0.8 mm, 1.8 mm and 1.3 mm approximately, the cross-section areas of the wirings  460  to  462  are respectively 0.00070 mm 2 , 0.00282 mm 2 , and 0.00125 mm 2  approximately, and the lengths of the wirings  460  to  462  are approximately 1.9 mm. 
       Fifth Embodiment 
       [0053]      FIG. 8  illustrates a schematic view of a semiconductor laser device  500  in accordance with a fifth embodiment. The semiconductor laser device  500  is different from the semiconductor laser device  100  in points that wirings  560  to  562  are provided instead of the wirings  160  to  162 , the outer connection terminals  570  to  572  are provided instead of the outer connection terminals  170  to  172 , and bonding areas  552  and  573  and wirings  563  and  564  are further provided. 
         [0054]    The bonding area  552  is positioned on the second end side of the semiconductor laser  130  between the carrier edge area and the semiconductor laser  130 . That is, the bonding area  552  is positioned on the second end side of the semiconductor laser  130 , compared to the bonding areas  150  to  152 . The bonding area  573  is positioned away from the carrier  120 . For example, the bonding area  573  is positioned on an area where the outer connection terminals  570  to  572  are provided in the package  101 . The bonding areas  552  and  573  may not be electrically coupled to the semiconductor laser  130 . 
         [0055]    In the embodiment, heat flows toward or from outside through the bonding areas  552  and  573  and the wirings  563  and  564 . In this case, the area on the second end side of the semiconductor laser  130  is more subjected to the heat of outside. It is therefore possible to equalize the thermal flow toward or from outside on the area near the semiconductor laser  130 . Accordingly, the temperature distribution of the surface of the carrier  120  is restrained. 
         [0056]    For example, when the distances “a” to “c” are respectively 0.8 mm, 1.8 mm and 1.3 mm approximately, the lengths of the wirings  560  to  564  are respectively 1.9 mm, 1.9 mm, 1.9 mm, 3.2 mm and 3.2 mm approximately, and the cross-section area of the wirings  560  to  564  is approximately 0.00070 mm 2 . 
       Sixth Embodiment 
       [0057]      FIG. 9  illustrates a schematic view of a semiconductor laser device  600  in accordance with a sixth embodiment. The semiconductor laser device  600  is different from the semiconductor laser device  100  of  FIG. 4  in points that the interconnection metals  640  to  642  are provided instead of the interconnection metals  140  to  142 , wirings  660  to  665  are provided instead of the wirings  160  to  162 , and outer connection terminals  670  to  672  are provided instead of the outer connection terminals  170  to  172 . The interconnection metals  640  to  642  respectively have the bonding areas  650  to  652  on the opposite side of the semiconductor laser  130 . 
         [0058]    In the semiconductor laser device  600 , the bonding area  650  is positioned on the carrier edge area, the bonding area  651  is on the semiconductor laser  130  side compared to the carrier edge area, and the bonding area  652  is on the semiconductor laser  130  side compared to the bonding area  651 . In this case, the distance difference between the bonding areas and the semiconductor laser  130  is smaller than the semiconductor laser device  100  of  FIG. 4 . On the other hand, the distance difference between the bonding areas and the outer connection terminals is larger than the semiconductor laser device  100 . 
         [0059]    And so, the thermal resistance between the bonding area  651  and the outer connection terminal  671  is adjusted to be larger than that between the bonding area  652  and the outer connection terminal  672 , and the thermal resistance between the bonding area  650  and the outer connection terminal  670  is adjusted to be larger than that between the boding area  651  and the outer connection terminal  671 . For example, the thermal flow toward or from outside is equalized on the area near the semiconductor laser  130  when each thermal resistance is adjusted according to the number of the wirings as illustrated in  FIG. 9 . Accordingly, the temperature distribution of the surface of the carrier  120  is restrained. 
         [0060]    A description will be given of details of the interconnection metal.  FIG. 10A  and  FIG. 10B  illustrate an enlarged view of the interconnection metal provided on the carrier.  FIG. 10A  illustrates the interconnection metal  740 , the bonding area  750  and the wirings  760  to  762 .  FIG. 10B  illustrates the interconnection metals  745  and  746 , the bonding area  750  and the wirings  765  to  767 . 
         [0061]    The thermal flow amount through the bonding area hardly depends on a layout (division or connection) of the interconnection metal. The thermal influence from outside of a case where the bonding area  750  is included in the interconnection metal  740  and the wirings  760  to  762  are coupled to the bonding area  750  as illustrated in  FIG. 10A  is substantially the same as that of a case where the bonding area  750  extends from the interconnection metal  745  to the interconnection metal  746 , the wirings  765  and  766  are coupled to the interconnection metal  745 , and the wiring  767  is coupled to the interconnection metal  746 , if the thermal flow through the bonding area  750  is the same in the cases. 
         [0062]    It is preferable that the length, the cross-section area, the material and so on of the wiring coupled to each bonding area are set so that the thermal flow toward or from outside is equalized on the area near the semiconductor laser  130 . However, the temperature distribution of the surface of the carrier has only to be restrained. 
         [0063]    Conventionally, wavelength was unstable because temperature difference between a first end and a second end of a semiconductor laser was 0.1 degrees C. or more, although the temperature difference may be changed according to outer temperature. In accordance with the embodiment, however, the temperature difference between the first end and the second end of the semiconductor laser was not observed in the same condition. 
         [0064]    The present invention is not limited to the specifically described embodiments and variations but other embodiments and variations may be made without departing from the scope of the claimed invention.