Abstract:
In order to realize a thermistor on a base substrate without restricting the layout of a wiring layer, a thermistor mounting apparatus is provided, the thermistor mounting apparatus including a base substrate, and a thermistor component provided over the base substrate, in which the thermistor component has an insulating substrate, an electrode provided over the insulating substrate, and a thermistor provided over the insulating substrate and electrically connected to the electrode.

Description:
[0001]    The contents of the following Japanese patent application(s) are incorporated herein by reference: No. 2015-114191 filed on Jun. 4, 2015. 
       BACKGROUND 
       [0002]    1. Technical Field 
         [0003]    The present invention relates to a thermistor mounting apparatus and a thermistor component. 
         [0004]    2. Related Art 
         [0005]    An apparatus is conventionally known in which a substrate provided with an electronic component such as a semiconductor chip or the like is further provided with a thermistor (refer to, for example, Patent Document 1). 
       PRIOR ART DOCUMENT 
       [0006]    Patent Document 1: Japanese Patent Application Publication 2011-86821 
         [0007]    A wiring layer on a substrate, which is connected to an electronic component, must be electrically insulated from an electrode on the substrate, which is connected to a thermistor. Therefore, in a case where the electronic component and the thermistor are provided on the same substrate, the layout of the wiring layer is restricted. 
       SUMMARY 
       [0008]    In a first aspect of the present invention, a thermistor mounting apparatus is provided, the thermistor mounting apparatus including a base substrate, an insulating substrate provided over the base substrate, an electrode provided over the insulating substrate, and a thermistor provided over the insulating substrate and electrically connected to the electrode. 
         [0009]    In a second aspect of the present invention, a thermistor mounting apparatus is provided, the thermistor mounting apparatus including a base substrate, a wiring layer provided over the base substrate, an insulating substrate provided over the wiring layer, an electrode provided over the insulating substrate, and a thermistor provided over the insulating substrate and electrically connected to the electrode. 
         [0010]    In a third aspect of the present invention, a thermistor component is provided, the thermistor component including an insulating substrate, an electrode provided over the insulating substrate, a thermistor provided over the insulating substrate and electrically connected to the electrode, and an adhering layer provided under the insulating substrate. 
         [0011]    The summary clause does not necessarily describe all necessary features of the embodiments of the present invention. The present invention may also be a sub-combination of the features described above. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]      FIG. 1A  is a cross-sectional view showing an example of a thermistor mounting apparatus  100  according to an embodiment of the present invention. 
           [0013]      FIG. 1B  is a perspective view showing an outline of the thermistor mounting apparatus  100 . 
           [0014]      FIG. 2  is a top plan view showing an example of the thermistor mounting apparatus  100 . 
           [0015]      FIG. 3  is a top plan view showing an example of a thermistor mounting apparatus  200  as a comparative example. 
           [0016]      FIG. 4  is a cross-sectional view showing a structural example of a thermistor component  10 . 
           [0017]      FIG. 5  is a top plan view showing another example of the thermistor mounting apparatus  100 . 
       
    
    
     DESCRIPTION OF EXEMPLARY EMBODIMENTS 
       [0018]    Hereinafter, some embodiments of the present invention will be described. The embodiments do not limit the invention according to the claims, and all the combinations of the features described in the embodiments are not necessarily essential in means provided by aspects of the invention. 
         [0019]      FIG. 1A  is a cross-sectional view showing an example of a thermistor mounting apparatus  100  according to an embodiment of the present invention.  FIG. 1B  is a perspective view showing an outline of the thermistor mounting apparatus  100 . The thermistor mounting apparatus  100  is provided with a thermistor  12  on a base substrate  30 . The thermistor mounting apparatus  100  of the present embodiment includes a thermistor component  10  and the base substrate  30 . The thermistor component  10  has an insulating substrate  20 , electrodes  14 , and the thermistor  12 . The thermistor mounting apparatus  100  of the present embodiment further includes an electronic component  60 , a wiring layer  40 , and a heat radiating portion  50 . 
         [0020]    The base substrate  30  is an insulating substrate such as, for example, a ceramic substrate, a resin substrate, and the like. Alternatively, the base substrate  30  may be a metal substrate constituted of copper, aluminum, or the like. In a case where the base substrate  30  is a metal substrate, the thermistor mounting apparatus  100  can omit the heat radiating portion  50 . Moreover, in a case where the base substrate  30  is a metal substrate, the thermistor mounting apparatus  100  further includes an insulating layer between the wiring layer  40  and the base substrate  30  to electrically insulate the wiring layer  40  and the base substrate  30 . 
         [0021]    The heat radiating portion  50  is provided under the base substrate  30 . The heat radiating portion  50  of the present embodiment is arranged in contact with the lower surface of the base substrate  30 . The lower surface of the base substrate  30  refers to one of two main surfaces of the base substrate  30 . The heat radiating portion  50  is constituted of a material having thermal conductivity higher than that of the base substrate  30 . The heat radiating portion  50  of the present embodiment is formed on the entire lower surface of the base substrate  30 . As an example, the base substrate  30  is a ceramic substrate, and the heat radiating portion  50  is a copper plate. The heat radiating portion  50  of the present embodiment is bonded to, for example, the base substrate  30  by a DCB (Direct Copper Bond) method. 
         [0022]    The thermistor component  10  is provided over the base substrate  30 . In the thermistor mounting apparatus  100  of the present embodiment, the wiring layer  40  is arranged between the thermistor component  10  and the base substrate  30 . The wiring layer  40  of the present embodiment is arranged in contact with the upper surface of the base substrate  30 . The upper surface of the base substrate  30  refers to a surface on the opposite side of the above-mentioned lower surface out of the two main surfaces of the base substrate  30 . 
         [0023]    The wiring layer  40  electrically connects the electronic component  60  and other components other than the thermistor component  10 . The electronic component  60  and the thermistor component  10  are secured to the upper surface of the wiring layer  40  of the present embodiment. The wiring layer  40  is formed of a conductive material. The wiring layer  40  of the present embodiment is a copper plate, and is bonded to the base substrate  30  by the DCB method. The wiring layer  40  may be obtained by patterning a conductive layer in a predetermined shape. 
         [0024]    The thermistor component  10  is secured to the upper surface of the wiring layer  40 . The thermistor component  10  has the thermistor  12 , the insulating substrate  20 , and the electrodes  14 . The thermistor  12  is electrically insulated from the wiring layer  40  by the insulating substrate  20 . The thermistor component  10  of the present embodiment further has a thermal conductive layer  16  and an adhesive layer  18 . 
         [0025]    The insulating substrate  20  is constituted of, for example, an insulating material such as ceramic, resin, or the like. The insulating substrate  20  is provided over the base substrate  30 . An area of the insulating substrate  20  is smaller than the area of the base substrate  30 . Moreover, the area of the insulating substrate  20  is smaller than an area of the wiring layer  40 . More specifically, the area of the insulating substrate  20  is smaller than a region of the upper surface of the wiring layer  40  other than the region where the electronic component  60  is provided. 
         [0026]    This allows the thermistor component  10  to be installed in a region different from the electronic component  60  on the upper surface of the base substrate  30 . For example, the area of the insulating substrate  20  is no greater than half of the area of the base substrate  30 . Moreover, the insulating substrate  20  has a thickness capable of assuring insulation between the wiring layer  40  and the thermistor  12 . As an example, the insulating substrate  20  has a thickness identical to that of the base substrate  30 . 
         [0027]    The thermal conductive layer  16  is provided between the insulating substrate  20  and the base substrate  30 . Moreover, the thermal conductive layer  16  is formed of a material having thermal conductivity higher than that of the insulating substrate  20 . In the present embodiment, the thermal conductive layer  16  is constituted of copper, and the insulating substrate  20  is constituted of ceramic. The thermal conductive layer  16  of the present embodiment is bonded to the insulating substrate  20  by the DCB method. In the present embodiment, an area of the thermal conductive layer  16  is substantially identical to the area of the insulating substrate  20 . 
         [0028]    The adhesive layer  18  is provided between the thermal conductive layer  16  and the base substrate  30 . The adhesive layer  18  of the present embodiment secures the lower surface of the thermal conductive layer  16  to the upper surface of the wiring layer  40 . The thermal conductive layer  16  is constituted of a material in which adhesive properties of the thermal conductive layer  16  to the adhesive layer  18  are higher than adhesive properties of the insulating substrate  20  to the adhesive layer  18 . The phrase “adhesive properties . . . higher” means that in a case where a force is applied in a direction where the base substrate  30  and the insulating substrate  20  separate from each other, the force to be generated when the base substrate  30  and the insulating substrate  20  start to separate is greater. In the present embodiment, for example, the adhesive layer  18  is constituted by solder. 
         [0029]    The electrodes  14  are provided over the insulating substrate  20 . In the present embodiment, two electrodes  14  are arranged in contact with the upper surface of the insulating substrate  20 . The two electrodes  14  are provided separating from each other within a region opposite to the thermal conductive layer  16 . The distance between the two electrodes  14  is substantially the same as the length of the thermistor  12 . It is preferable that the insulating substrate  20  is as small as possible to the extent that the two electrodes  14  can be provided thereon. For example, in an array direction where the two electrodes  14  are disposed, the distance between an end of each electrode  14  and an edge of the insulating substrate  20  is shorter than a width of each electrode  14 . 
         [0030]    The thermistor  12  is provided over the insulating substrate  20  and electrically connected to the electrodes  14 . The thermistor  12  of the present embodiment has two terminals  12   a  electrically connected to the respective two electrodes  14 . The thermistor  12  has a resistor portion between the two terminals  12   a , in which electric resistance changes depending on temperature. Although  FIGS. 1A and 1B  schematically show a structure in which there is a space between that resistor portion and the insulating substrate  20 , at least a part of the resistor portion may be in contact with the insulating substrate  20 . 
         [0031]    The electronic component  60  is provided in a region different from the insulating substrate  20  over the base substrate  30 . The electronic component  60  of the present embodiment is secured to a region different from the insulating substrate  20  on the upper surface of the wiring layer  40 . The electronic component  60  is provided in a position which is at only a predetermined distance away from the thermistor component  10  so as to maintain electrical insulation against the thermistor  12 . In the present embodiment, the electronic component  60  is a power semiconductor chip such as IGBT (Insulated Gate Bipolar Transistor), power MOSFET, or the like, to which a high voltage is applied. 
         [0032]    According to the thermistor mounting apparatus  100  in the present embodiment, the electronic component  60  and the thermistor component  10  can be provided on the same base substrate  30 . Moreover, since the thermistor component  10  includes the insulating substrate  20 , the thermistor component  10  can be provided in contact with the wiring layer  40 . For this reason, the wiring layer  40  does not have to be laid out so as to avoid the thermistor component  10 , thereby improving the degree of freedom in the layout of the wiring layer  40 . 
         [0033]    Moreover, since it is not necessary to reserve a region for routing the wiring layer  40  so as to avoid the thermistor component  10 , the base substrate  30  can be miniaturized, and the thermistor mounting apparatus  100  can be miniaturized. Similarly, since a region where the electronic component  60  is provided can be widened, the electronic component  60  of large size can be easily mounted. 
         [0034]    As shown in  FIG. 1B , it is preferable that the thermistor  12  is secured to the insulating substrate  20 , and the thermistor component  10  is then secured to the base substrate  30 . In the present embodiment, the thermal conductive layer  16 , the two electrodes  14 , and the thermistor  12  are secured to the insulating substrate  20 , and the thermistor component  10  is then secured to the wiring layer  40 . That is, a finished thermistor component  10  is secured to the base substrate  30 . As an example, although the adhesive layer  18  is provided on the thermistor component  10  side, the adhesive layer  18  may also be provided on the base substrate  30  side. 
         [0035]    Further, the electronic component  60  is also secured to the wiring layer  40  using solder, or the like. As an example, the electronic component  60  and the thermistor  10  are secured to the wiring layer  40  in the same reflow step. In another example, the thermistor component  10  may be secured to the wiring layer  40  after the arrangement of the thermistor component  60 , or the electronic component  60  may be secured to the wiring layer  40  after the arrangement of the thermistor component  10 . 
         [0036]      FIG. 2  is a top plan view showing an example of the thermistor mounting apparatus  100 . The thermistor mounting apparatus  100  of the present embodiment further has an electrode  70  for the thermistor mounting apparatus  100  shown in  FIGS. 1A and 1B . The electrode  70  is electrically connected to the outside of the thermistor mounting apparatus  100  through a wire, a lead, a pin, or the like. 
         [0037]    The electrode  70  is bonded to the wiring layer  40 . The electronic component  60  and the electrode  70  are thereby electrically connected via the wiring layer  40 . In the present embodiment, a current I M1  flows from the electronic component  60  to the electrode  70 . 
         [0038]    In the present example, the thermistor component  10  is arranged between the electronic component  60  and the electrode  70  on the wiring layer  40 . Since the thermistor component  10  has the insulating substrate  20 , the thermistor component  10  can be installed on the electrode  70 . Moreover, the temperature of the electronic component  60  which performs operations while flowing the current I M1  can be measured using the thermistor component  10  arranged in its proximity. 
         [0039]      FIG. 3  is a top plan view showing an example of the thermistor mounting apparatus  200  as a comparative example. A thermistor component  210  in the thermistor mounting apparatus  200  does not have the insulating substrate  20 . For example, the thermistor component  210  directly secures the electrode  14  and the thermistor  12  to the base substrate  30 . In this case, the wiring layer  40  has an opening  22  from which the conductive material is removed in a region where the thermistor component  210  is provided. 
         [0040]    Since the thermistor component  10  in the example of  FIG. 2  has the insulating substrate  20 , the thermistor component  10  has insulating properties higher than those of the thermistor component  210  in the example of  FIG. 3 . For this reason, even if a distance D 1  between the thermistor component  10  and the electronic component  60  is made shorter than a distance D 2  between the thermistor component  210  and the electronic component  60 , insulation can be assured between the thermistor component  10  and the electronic component  60 . Therefore, the thermistor mounting apparatus  100  can be miniaturized. Furthermore, since the distance between the electronic component  60  and the thermistor  12  can be made shorter, the temperature of the electronic component  60  can be measured more accurately. 
         [0041]    Moreover, since the wiring layer  40  has the opening  22  in the example of  FIG. 3 , a current I M2  flowing from the electronic component  60  to the electrode  70  flows by bypassing the opening  22 . For this reason, the wiring layer  40  is required to have a width allowing the current I M2  to flow at low resistance, in addition to a width W 2  of the opening  22 . Meanwhile, since the current I M1  can pass below the thermistor component  10 , the thermistor mounting apparatus  100  shown in  FIG. 2  has less restriction on the layout of the wiring layer  40 . For example, a width of the wiring layer  40  of the thermistor mounting apparatus  100  can be reduced compared to that of the thermistor mounting apparatus  200 , and thus the thermistor mounting apparatus  100  can be miniaturized. 
         [0042]      FIG. 4  is a cross-sectional view showing a configurational example of the thermistor component  10 . The thermistor component  10  shown in  FIG. 4  further has a securing portion  24 , in addition to the configuration of the thermistor component  10  shown in  FIGS. 1A and 1B . 
         [0043]    The securing portion  24  secures the thermistor  12  to the electrodes  14 . The securing portion  24  is constituted of a material having a melting point higher than that of the adhesive layer  18 . For example, the securing portion  24  is a metal sintered material, and the adhesive layer  18  is solder containing tin. The securing portion  24  may also be solder. In this case, the composition of materials such as tin, copper, silver, or the like contained in the solder has only to be adjusted to make the melting point of the securing portion  24  higher than the melting point of the adhering layer  18 . By making such a constitution, the connection can be rigidly maintained between the thermistor  12  and the electrodes  14  even if the adhesive layer  18  is heated to secure the finished thermistor component  10  to the wiring layer  40 . The thermistor component  10  may also have the adhesive layer  18 . For this reason, the thermistor component  10  can be easily secured to any position on the wiring layer  40 . 
         [0044]      FIG. 5  is a top plan view showing another example of the thermistor mounting apparatus  100 . However, the base substrate  30  and the wiring layer  40  are omitted in  FIG. 5 . The thermistor mounting apparatus  100  of the present embodiment has a plurality of electronic components  60 .  FIG. 5  shows three pieces of electronic components  60 - 1 ,  60 - 2 ,  60 - 3 . The electronic components  60  of the present embodiment are semiconductor chips having the same characteristics and being provided in parallel. The “same characteristics” do not mean the very same characteristics in the strict sense. Even if there are differences in characteristics due to the manufacturing variations, such differences would be included in the concept of the above-mentioned “same characteristics.” 
         [0045]    The thermistor mounting apparatus  100  has the electrode  70  provided opposite to the respective electronic component  60 . Although the electrode  70  shown in  FIG. 5  is provided in common with the respective electronic component  60 , the electrode  70  may also be provided for each electronic component  60 . 
         [0046]    The thermistor component  10  is provided corresponding to a part of the electronic components  60  among the plurality of electronic components  60 . In the present embodiment, the thermistor component  10  is provided corresponding to the electronic component  60 - 2 , meanwhile other electronic components  60 - 1 ,  60 - 3  are not provided with the thermistor component  10 . For example, although the thermistor component  10  is provided on a straight line connecting the electronic component  60 - 2  and the electrode  70  at the shortest distance, no thermistor component  10  is provided on straight lines connecting other electronic components  60  and the electrode  70  at the shortest distance. 
         [0047]    Since the thermistor component  10  has the insulating substrate  20 , the current I M  flowing between the electronic component  60  and the electrode  70  is not affected even if the thermistor component  10  is provided on the wiring layer  40 . For this reason, even if the thermistor component  10  is provided corresponding to only a part of the electronic components  60  among the plurality of electronic components  60  having the same characteristics and being provided in parallel, characteristics variations among the electronic components  60  do not increase. For this reason, the current does not concentrate on the specific electronic component  60  even if only a part of the electronic components  60  is provided with the thermistor component  10 . 
         [0048]    In particular, in a case where the electronic components  60  are power semiconductor chips such as IGBT or the like, failures easily occur in the electronic components  60  when the current concentrates on the specific electronic component  60 . In the thermistor mounting apparatus  100  of the present embodiment, the current does not concentrate even if only a part of the electronic components  60  is provided with the thermistor component  10 , and thus the freedom degree in the arrangement of the thermistor component  10  can be improved. 
         [0049]    The expressions of a pair of “on” and “over” and a pair of “below” and “under” in the claims and the specification mutually refer to opposite directions. However, the terms “on” and “over” are not limited to a direction opposite to the gravity direction. Moreover, the terms “below” and “under” are not limited to a direction of the gravity direction. For example, with regard to the thermistor mounting apparatus  100  implemented in the electronic equipment, it is apparent that the thermistor mounting apparatus  100  may be included in the present invention even if the thermistor component  10  is arranged on the ground surface side of the base substrate  30 . 
         [0050]    While the embodiments of the present invention have been described, the technical scope of the invention is not limited to the above described embodiments. It is apparent to persons skilled in the art that various alterations and improvements can be added to the above-described embodiments. It is also apparent from the scope of the claims that the embodiments added with such alterations or improvements can be included in the technical scope of the invention. 
       DESCRIPTION OF REFERENCE NUMERALS 
       [0051]      10  . . . thermistor component,  12  . . . thermistor,  14  . . . electrode,  16  . . . thermal conductive layer,  18  . . . adhesive layer,  20  . . . insulating substrate,  22  . . . opening,  24  . . . securing portion,  30  . . . base substrate,  40  . . . wiring layer,  50  . . . heat radiating portion,  60  . . . electronic component,  70  . . . electrode,  100  . . . thermistor mounting apparatus,  200  . . . thermistor mounting apparatus,  210  . . . thermistor component