Abstract:
An electrical circuit device includes an electrical circuit that includes a plurality of electrically connected components including a component that necessitates heat measures, a substrate that physically connects main components among the plural components of the electrical circuit, and a package that hermetically seals the substrate. The component that necessitates heat measures is arranged outside the package.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to an electrical circuit device of which at least a portion is hermetically sealed by a package, and, more particularly to an electrical circuit device that necessitates heat dissipation. 
         [0003]    2. Description of the Related Art 
         [0004]    For avoiding incorrect operations occurring due to dust or dirt that is entered into an existing electrical circuit, the existing electrical circuit is physically hermetically sealed by a package. However, upon hermetically sealing the electrical circuit, heat generated by electrical elements is internally retained, thus increasing internal atmospheric temperature. 
         [0005]    Various existing technologies have been suggested for dissipating outside, heat generated by the electrical elements. For example, in the technology disclosed in Japanese Patent Application Laid-open No. H10-44657, by causing electronic components to contact a metallic casing, heat generated by the electronic components is emitted outside via the metallic casing. 
         [0006]    In the technology disclosed in Japanese Patent Application Laid-open No. 2000-332171, heat generated by heating elements is emitted by sequentially transmitting to a through-hole for heat-dissipating fins, a heat-dissipating block, and a casing. Furthermore, in the technology disclosed in Japanese Patent Application Laid-open No. 2001-274574, a heating element package is arranged in an upper portion of an electrical enclosure and by causing a heat dissipation bottom portion to extend in a bottom wall direction of a lower casing, generated heat is emitted from the heating element package. 
         [0007]    However, in the technologies mentioned above, if heat generated inside the package exceeds a heat dissipation capacity, generated heat is retained inside the package, thus increasing the atmospheric temperature. Due to this, radiation heat warms up components on a resin substrate to a temperature higher than an allowable temperature limit of the components, thereby degrading and damaging the components. Due to this, heat dissipation properties of heating components are worsened. 
         [0008]    To be specific, because an in-vehicle electronic control unit (ECU) needs to be safely and reliably operated in a high temperature and in a highly dusty environment, hermetically sealing the in-vehicle electronic control unit (ECU) by using the package and heat dissipation are very important in the in-vehicle electronic control unit (ECU). However, in an electronic control unit that drives a motor such as an electric power steering motor, a heating value of metal-oxide-semiconductor field-effect transistor (MOSFET) is high. Due to this, other electronic components are significantly affected. 
         [0009]    Upon assuming that the temperature inside the package will increase, using an expensive component having high heat resistance properties is necessary, whereby a cost of an entire device increases. Furthermore, because a heat dissipation path from inside to outside of the package is to be built, a size of the entire device increases. 
       SUMMARY OF THE INVENTION 
       [0010]    It is an object of the present invention to at least partially solve the problems in the conventional technology. 
         [0011]    According to one aspect of the present invention, an electrical circuit device includes an electrical circuit that includes a plurality of electrically connected components including a component that necessitates heat measures, a substrate that physically connects main components among the plural components of the electrical circuit, and a package that hermetically seals the substrate, and the component that necessitates heat measures is arranged outside the package. 
         [0012]    The above and other objects, features, advantages and technical and industrial significance of this invention will be better understood by reading the following detailed description of presently preferred embodiments of the invention, when considered in connection with the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]      FIG. 1  is a schematic of an electronic control unit according to an embodiment of the present invention; 
           [0014]      FIG. 2  is a schematic of an electronic control unit when a heating component is arranged inside a radiator plate; 
           [0015]      FIG. 3  is a schematic for explaining a fixing method of a MOSFET; 
           [0016]      FIG. 4  is a schematic for explaining how heat conduction from the MOSFET to a package is restrained by through-holes on the radiator plate; 
           [0017]      FIG. 5  is a schematic for explaining how heat conduction from the MOSFET to the package is restrained by a transverse groove on the radiator plate; 
           [0018]      FIG. 6  is a schematic for explaining how heat conduction from the MOSFET to the package is restrained by a spacer or a sheet of heat insulating material; 
           [0019]      FIG. 7  is a schematic for explaining a structure in which the MOSFET is connected to a lead wire that is pulled out from a resin substrate; 
           [0020]      FIG. 8  is a schematic for explaining a structure in which a plurality of components necessitating heat dissipation is pulled out outside the package as a module; 
           [0021]      FIG. 9  is a schematic for explaining an example when a heat sink is not provided; 
           [0022]      FIG. 10  is a schematic for explaining an example when an component necessitating heat dissipation is arranged outside by selectively forming the package with respect to a portion of a substrate; 
           [0023]      FIG. 11  is a schematic for explaining an example when the component necessitating heat dissipation that is pulled out from the package is connected to another product, an electrical enclosure, or a vehicle; and 
           [0024]      FIG. 12  is a schematic for explaining an example when a component that needs to be maintained at a low temperature is pulled out outside the package. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0025]    Exemplary embodiments of the electrical circuit device according to the present invention are explained in detail below with reference to the accompanying drawings. 
         [0026]      FIG. 1  is a schematic for explaining an electronic control unit (ECU)  1  for an electric power steering (EPS) according to an embodiment of the present invention in comparison with an existing electronic control unit  100 . An electrical circuit of the existing electronic control unit  100  is formed of a metal-oxide-semiconductor field-effect transistor (MOSFET)  40  mounted on a metallic substrate  31  and components  41  to  43  mounted on a resin substrate  30 . 
         [0027]    The resin substrate  30  and the metallic substrate  31  are connected by a bus bar  32  and the entire electrical circuit is hermetically sealed by a package  110 . By arranging a radiator plate  120 , which is a type of a heat sink, in the package  110 , heat dissipation of the electrical circuit is carried out. 
         [0028]    In the ECU  100  for the EPS, heat generated by the MOSFET  40  affects other components most, thereby damaging and degrading the other components. In the electronic control unit  100 , the MOSFET  40  is mounted on the metallic substrate  31  and is separated from the resin substrate  30 . The radiator plate  120  is arranged in the vicinity of the metallic substrate  31 . Thus, by using the structure mentioned earlier, from the heat generated by the MOSFET  40 , an amount of heat emitted outside the package  110  is increased and an amount of heat within the package  110  is decreased. 
         [0029]    In the existing structure, the heat dissipation path towards inside the package  110  exists because the MOSFET  40 , which is a heating component, is arranged within the package  110 . Hence, radiation heat warms up the components  41  to  43  mounted on the resin substrate  30  sometimes to a temperature higher than the allowable temperature limit of the components  41  to  43 , thereby causing degradation of the components  41  to  43 . To be specific, the life of an electrolyte capacitor that is weak in heat generation is shortened. 
         [0030]    However, in the ECU  1  according to the embodiment of the present invention, the MOSFET  40  is pulled out outside a package  10  by a lead wire and is arranged in a radiator plate  20 . Due to this, the MOSFET  40 , which is the heating component, can be cooled by the external air. 
         [0031]    An opening, which is arranged in the package  10  and the radiator plate  20  for pulling out the lead wire, is filled-in by a resin  33  (or sealing gel, high heat dissipation bond, etc.). Due to this, sealing properties of the package  10  are secured and insertion of outside dust is prevented. 
         [0032]    Thus, without impairing functions of the package  10 , heat generated by the MOSFET  40  is emitted outside the package  10 . Due to this, increase in the internal atmospheric temperature can be avoided and heat dissipation properties of a heating component can be enhanced. 
         [0033]    Because the components on the resin substrate are not affected by the radiation heat, the allowable temperature limit of the components can be lowered thus spec down of the components and reduction in a cost can be realized. In addition, a space inside the package is increased because the heating component, which is usually large in size, is arranged outside the package  10 . Because the heating component is affected by the wind and the surrounding temperature is reduced, the heat dissipation properties of the heating component can be enhanced and the entire ECU  1  can be downsized. 
         [0034]    The MOSFET  40  need not be always arranged outside a radiator plate. For example, in an electronic control unit  2   a  shown in  FIG. 2 , the MOSFET  40  is arranged in a space provided inside a radiator plate  21   a . Thus, even if the heating component is arranged inside the radiator plate  21   a , heat generated by the heating component is emitted outside the electronic control unit  2   a  via the radiator plate  21   a  because the heat conductivity of the radiator plate  21   a  is high. 
         [0035]    In the electronic control unit  2   a , the package  10  is sealed by closing the opening between an arrangement location of the MOSFET  40  and the package  10  by the resin  33 . However, the arrangement location of the MOSFET  40  is separately arranged with respect to outside. When the MOSFET  40  is connected to the package  10  and the sealing properties inside the package  10  can be secured, the opening of the package  10  can be kept open, as shown in an electronic control unit  2   b.    
         [0036]    Any fixing method can be used for fixing the MOSFET  40  to the radiator plate. As shown in an electronic control unit  3  in  FIG. 3 , instead of screws, a retainer plate  34  that is provided in the radiator plate  20  can be used for fixing the MOSFET  40  to the radiator plate  20 . 
         [0037]    When the MOSFET  40  is fixed to the radiator plate  20 , although most of the heat generated by the MOSFET  40  is emitted outside the electronic control unit  3 , in other words, in the surrounding air, a heat conducting path from the radiator plate  20  to the package  10  exists. 
         [0038]    Providing a heat transfer restraining structure for restraining heat conduction from a component necessitating heat dissipation (for example, the MOSFET  40 ) to the package  10  is desirable. In a specific example of an electronic control unit  4   a  shown in  FIG. 4 , through holes  22   a  are drilled between the arrangement location of the MOSFET  40  of a radiator plate  22  and a package connecting surface. Due to this, the heat conductivity from the MOSFET  40  to the package  10  is reduced. 
         [0039]    Similarly, in an electronic control unit  4   b  shown in  FIG. 5 , a transverse groove  23   a  is arranged between the arrangement location of the MOSFET  40  of a radiator plate  23  and the package connecting surface. Due to this, the heat conductivity from the MOSFET  40  to the package  10  is reduced. 
         [0040]    In an electronic control unit  4   c  shown in  FIG. 6 , the heat sink is divided into radiator plates  24   a  and  24   b . By arranging a spacer or a sheet of a heat insulating material between the arrangement location of the MOSFET  40  of the radiator plate  24   b  and the package connecting surface, the heat conductivity from the MOSFET  40  to the package  10  is reduced. 
         [0041]    In an electronic control unit  4   c , the heat sink is divided and the spacer or the sheet of the heat insulating material is arranged. However, the spacer or the sheet of the heat insulating material can be arranged between the package and the heat sink. 
         [0042]    Modifications in the structure of the electronic control unit are explained herein. In an electronic control unit  5  shown in  FIG. 7 , the metallic substrate  31  and the bus bar is not included and the MOSFET  40  is pulled out from the resin substrate  30  by a lead wire  35 . Furthermore, instead of the lead wire  35 , a wire or the bus bar can be used. 
         [0043]    In  FIG. 8 , a plurality of components necessitating heat dissipation including a MOSFET are arranged inside a module  40   a . The module  40   a  is pulled out from the package  10  and is arranged on the radiator plate  20 . 
         [0044]    In an electronic control unit  7  shown in  FIG. 9 , the heat sink is not provided and the MOSFET  40 , which is pulled out from a package  11 , is arranged outside the package  11 . In this structure, the heat sink is not provided, and a member necessitating heat dissipation is exposed in the external air. Due to this, heat dissipation is effectively carried out as compared to the MOSFET  40  that is arranged inside the package  10 . 
         [0045]    In an electronic control unit  8  shown in  FIG. 10 , similarly to the other components  41  to  43 , the MOSFET  40  is mounted on the resin substrate  30 . When forming a package  12 , a formation location of the package  12  is controlled and the MOSFET  40  is mounted such that the MOSFET  40  is outside the package  12 . In  FIG. 10 , although a radiator plate  25  is arranged separately from the MOSFET  40 , the heat sink can be arranged such that the heat sink touches the MOSFET  40 . 
         [0046]    In an electronic control unit  9  shown in  FIG. 11 , the MOSFET  40  is pulled out by a long lead wire  35   a . The MOSFET  40  is arranged at any position separately from the package  10  or the radiator plate  20 . For example, the MOSFET  40  can be connected to another product, an electrical enclosure, or a vehicle. 
         [0047]    In an electronic control unit  9   a  shown in  FIG. 12 , the heating component is arranged on the metallic substrate  31  in the vicinity of the radiator plate  20 . An electrolyte capacitor  44  that needs to be maintained at a low temperature can be pulled out outside the package  10 . In  FIG. 12 , the resin substrate  30  and the electrolyte capacitor  44  are separated by spacers  36 . Due to this, the electrolyte capacitor  44  is not affected by the radiation heat of heat inside the package  10 . 
         [0048]    In the embodiments mentioned above, an example where the MOSFET in the ECU for the EPS is pulled out outside is explained. However, the present invention is not to be thus limited. The present invention can be widely applied for arranging the component necessitating heat dissipation in an electrical circuit device in which at least a portion of the electrical circuit device is hermetically sealed by the package. 
         [0049]    The components necessitating heat dissipation are the heating elements having a high heating value at the time of operation as compared with other components and elements for which the surrounding temperature needs to be maintained at the low temperature as compared with other components. 
         [0050]    For example, in the ECU for the EPS, apart from the MOSFET, a shunt resistance, a power smoothing coil or the electrolyte capacitor, and a relay are preferably pulled out outside as the components necessitating heat dissipation. 
         [0051]    In a booster circuit, the MOSFET, the power smoothing coil or the electrolyte capacitor, and similarly, a boosting coil or the electrolyte capacitor, and rectifying diodes are the components necessitating heat dissipation. 
         [0052]    In a pre-crash ECU, diodes used in a supplied current carrier for break lamp are preferably pulled out as the components necessitating heat dissipation. 
         [0053]    Moreover, in a general ECU, transistor (for example, a supply circuit portion such as 5 volts (V) power supply), diodes (for example, the supply circuit portion such as 5 V power supply), a motor driving product, and heating components in a current supplying line (lamp, etc.) are the components necessitating heat dissipation. 
         [0054]    In the electronic control unit according to the embodiment mentioned above, the MOSFET  40 , which is the component necessitating heat dissipation, is pulled out outside the package  10  by the lead wire. Due to this, heat generated by the MOSFET  40  is emitted outside the package  10 , thus increase in the internal atmospheric temperature is avoided and the heat dissipation properties of the heating component are enhanced. 
         [0055]    Thus, the spec down of the component can be carried out and the cost can be reduced. By arranging the heating component, which is usually large in size, outside, the space inside the package is increased. Furthermore, due to the enhanced heat dissipation properties of the component necessitating heat dissipation, the electronic circuit unit can be downsized. 
         [0056]    According to an embodiment of the present invention, a component that necessitates heat dissipation is arranged by pulling out outside a package. Due to this, increase in atmospheric temperature inside the package can be avoided and degradation or break down of an electrical circuit device can be prevented. Due to this, a cost can be reduced and an electrical enclosure of the electrical circuit device can be downsized. 
         [0057]    Although the invention has been described with respect to specific embodiments for a complete and clear disclosure, the appended claims are not to be thus limited but are to be construed as embodying all modifications and alternative constructions that may occur to one skilled in the art that fairly fall within the basic teaching herein set forth.