Patent Publication Number: US-2017365536-A1

Title: Electronic Device

Description:
TECHNICAL FIELD 
     The present invention relates to an electronic device having a function to cool electronic components included therein. 
     BACKGROUND ART 
     In recent years, offshore wind power generation effectively utilizing natural energy is focused to prevent from global warming. Wind power generation needs a semiconductor apparatus represented by a power conversion module for converting rotation of a windmill into power and a low-voltage module for such as a motor control device. A method using switching of a highly efficient power semiconductor is mainly used in a power converter, and a semiconductor device is insulation-protected by being sealed by gel and resin. The ocean atmosphere is more humid than the land atmosphere and contains much salt. Therefore, a power converter and a control device excellent in moisture proof and waterproof properties are needed. 
     Further, to promote energy saving and realize a low carbon society, motorization of vehicles such as electric vehicles and hybrid vehicles is rapidly developed. Especially, a role of an inverter which is a basic component of a motorization system is more diversified than before, and miniaturization and high output of the inverter are required at the same time. The inverter includes, as a main component, a power semiconductor module in which a power semiconductor chip using such as a transistor and a diode is sealed by resin. In a power semiconductor module for an electric vehicle and a hybrid vehicle, heat is generated by energization with an increase in a current capacity of a device and an increase in a current density by miniaturization. Therefore, a cooling unit is provided to prevent from a temperature rise in the power semiconductor module. As the cooling method, a refrigerant circulation method using water, oil, and organic solvent are mainly used, and a waterproof structure with respect to a refrigerant is needed. 
     Epoxy resin is known as resin used to cover a conductor by such as electronic components and a power cable (refer to PTL 1). PTL 1 describes that a water absorption property becomes lower, and a water resistance becomes higher than before by introducing a hydrophobic group such as an alkyl group to a branched chain of epoxy resin. 
     CITATION LIST 
     Patent Literature 
     PTL 1: JP 2004-119667 A1 
     SUMMARY OF INVENTION 
     Technical Problem 
     Epoxy resin including a hydrophobic group has poor wettability with a semiconductor device and a conductor such as a wiring and an electric wire and has poor adhesion. When such epoxy resin is used as an insulator, peeling from a conductor and a void in a molding occur by heat curing, and consequently water may accumulate, and insulation may be reduced. 
     An issue is to provide an electronic device capable of preventing entry of a refrigerant such as water, oil, and organic solvent without deteriorating reliability such as insulation. 
     Solution to Problem 
     An electronic device according to the present invention includes electronic components and an epoxy resin portion which seals the electronic components. The electronic device is disposed in a refrigerant which cools the electronic components. A first layer is formed on a surface or inside of the epoxy resin portion. The first layer has the three-dimensional crosslinking structure. The first layer is formed such that a length calculated by cube root of an average free volume in the three-dimensional crosslinking structure is shorter than a length of the longest side of molecules included in the refrigerant. 
     Advantageous Effects of Invention 
     According to the present invention, entry of a refrigerant can be prevented, and waterproof effects can be improved. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a diagram illustrating a control block of a hybrid vehicle. 
         FIG. 2  is a diagram describing a configuration of an electric circuit of an inverter circuit. 
         FIG. 3( a )  is a perspective view of a semiconductor module. 
         FIG. 3( b )  is a perspective view of the semiconductor module viewed from different viewpoint. 
         FIG. 3( c )  is a sectional schematic view of the semiconductor module cut on line IVa-IVa. 
         FIG. 4  is a circuit diagram illustrating a circuit configuration of a semiconductor module. 
         FIG. 5  is a perspective view of a conductor plate assembly excluding a sealing resin of a semiconductor module. 
         FIG. 6  is a perspective view of a conductor plate assembly excluding a first conductor plate and a third conductor plate illustrated in  FIG. 5 . 
         FIG. 7  is a sectional schematic view of a semiconductor structure  302 . 
         FIG. 8( a )  is a schematic view describing formation of a three-dimensional curing structure of a first layer. 
         FIG. 8( b )  is a schematic view describing formation of the three-dimensional curing structure of the first layer. 
         FIG. 8( c )  is a schematic view describing formation of the three-dimensional curing structure of the first layer. 
         FIG. 9  is a perspective view of a semiconductor module according to a second embodiment. 
         FIG. 10  is a sectional schematic view of the semiconductor module according to the second embodiment. 
         FIG. 11  is a sectional schematic view of a semiconductor module according to a third embodiment. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Embodiments according to the present invention will be described below with reference to drawings. 
     First Embodiment 
       FIG. 1  is a diagram illustrating a control block of a hybrid vehicle. An engine EGN and a motor generator MG 1  generate a torque for traveling of a vehicle. The motor generator MG 1  generates a rotation torque and also has a function to convert mechanical energy added from the outside to the motor generator MG 1  into electric power. 
     The motor generator MG 1  is, for example, a synchronous machine or an induction machine and operates as a motor and as a power generator according to an operation method as described above. In the case where the motor generator MG 1  is mounted in a vehicle, the motor generator MG 1  is preferably down-sized and obtains high output, and a permanent magnet-type synchronous motor using such as a neodymium magnet is suitable. A permanent magnet-type synchronous motor is suitable for a motor for a vehicle in a viewpoint that heat generation of a rotor is lower than that of an induction motor. 
     An output torque of the engine EGN is transmitted to the motor generator MG 1  via a power distribution mechanism TSM, a rotation torque from the power distribution mechanism TSM or a rotation torque generated by the motor generator MG 1  is transmitted to a wheel via a transmission TM and a differential gear DIF. On the other hand, when regenerative breaking is operated, a rotation torque is transmitted to the motor generator MG 1  from a wheel, and AC power is generated based on the supplied rotation torque. The generated AC power is converted into DC power by a power converter  200  as described below, and a high voltage battery  136  is charged, and the charged power is reused for traveling energy. 
     The power converter  200  will be described next. The power converter  200  converts DC power into AC power and AC power into DC power by a switching operation of a semiconductor device. An inverter circuit  140  is electrically connected to the battery  136  via a DC connector  138 , and power is mutually exchanged between the battery  136  and the inverter circuit  140 . In the case where the motor generator MG 1  is operated as a motor, the inverter circuit  140  generates AC power based on DC power supplied from the battery  136  via the DC connector  138  and supplies the AC power to the motor generator MG 1  via an AC terminal  188 . A configuration including the motor generator MG 1  and the inverter circuit  140  operates as an electric power generation unit. 
     In the embodiment, by operating the electric power generation unit by power of the battery  136  as an electric unit, a vehicle can be driven by power of the motor generator MG 1 . Further, in the embodiment, the battery  136  can be charged by generating power by operating the electric power generation unit as a power generation unit by power of the engine EGN or power from a wheel. 
     The power converter  200  includes a capacitor module  500  to smooth DC power supplied to the inverter circuit  140 . 
     The power converter  200  includes a connector  21  for communication to receive a command from an upper control device or to send data indicating a state to the upper control device. In the power converter  200 , a control circuit  172  calculates a control amount of the motor generator MG 1  based on a command from the connector  21 , and also the control circuit  172  calculates whether to drive as a motor or as a power generator, generates a control pulse based on a result of the calculation, and supplies the control pulse to a driver circuit  174 . The driver circuit  174  generates a driving pulse for controlling the inverter circuit  140  based on the supplied control pulse. 
     Next, a configuration of an electric circuit of the inverter circuit  140  will be described with reference to  FIG. 2 . In the embodiment, an insulated gate bipolar transistor is used as a semiconductor device and hereinafter called IGBT. 
     An IGBT  328  and a diode  156  of an upper arm and an IGBT  330  and a diode  166  of a lower arm form a series circuit  150  of the upper and lower arms. The inverter circuit  140  includes the series circuit  150  corresponding to three phases including U, V, and W phases of AC power to be output. 
     These three phases correspond to each phase winding of three phases of an armature winding of the motor generator MG 1  in the embodiment. The series circuits  150  of upper and lower arms of each of three phases output AC current from an intermediate electrode  169  which is an intermediate portion of the series circuit. This intermediate electrode  169  is connected to an AC bus bar  802  which is an AC power line to the motor generator MG 1  through AC terminals  159  and  188 . 
     A collector electrode of the IGBT  328  of an upper arm is electrically connected to a positive electrode-side capacitor terminal  506  of the capacitor module  500  via a DC positive electrode terminal  157 . An emitter electrode of the IGBT  330  of a lower arm is electrically connected to a negative electrode-side capacitor terminal  504  of the capacitor module  500  via a DC negative electrode terminal  158 . 
     As described above, the control circuit  172  receives a control command from an upper control device via the connector  21 . Based on the control command, the control circuit  172  generates a control pulse which is a control signal to control the IGBT  328  and the IGBT  330  forming an upper arm or a lower arm of the series circuit  150  of each phase forming the inverter circuit  140  and supplies the control pulse to the driver circuit  174 . 
     Based on the above-described control pulse, the driver circuit  174  supplies a drive pulse to control the IGBT  328  and the IGBT  330  forming an upper arm or a lower arm of the series circuit  150  of each phase to the IGBT  328  and the IGBT  330  of each phase. The IGBT  328  and the IGBT  330  convert DC power supplied from the battery  136  into three-phase AC power by conducting or cutting off power based on the drive pulse from the driver circuit  174 , and the converted power is supplied to the motor generator MG 1 . 
     Each of the IGBT  328  of an upper arm and the IGBT  330  of a lower arm include a collector electrode, an emitter electrode for a signal, and a gate electrode. The diode  156  of an upper arm is electrically connected between a collector electrode terminal  153  and an emitter electrode terminal  155 . The diode  166  is electrically connected between a collector electrode terminal  163  and an emitter electrode terminal  165 . 
     A metal-oxide-semiconductor field-effect transistor (hereinafter abbreviated as MOSFET) may be used as a switching power semiconductor device. In this case, the diode  156  and the diode  166  are not needed. As the switching power semiconductor device, an IGBT is suitable in the case where a DC voltage is relatively high, and a MOSFET is suitable in the case where a DC voltage is relatively low. 
     The capacitor module  500  includes the positive electrode-side capacitor terminal  506 , the negative electrode-side capacitor terminal  504 , a positive electrode-side power source terminal  509 , and a negative electrode-side power source terminal  508 . High-voltage DC power from the battery  136  is supplied to the positive electrode-side power source terminal  509  and the negative electrode-side power source terminal  508  via the DC connector  138  and supplied to the inverter circuit  140  from the positive electrode-side capacitor terminal  506  and the negative electrode-side capacitor terminal  504  of the capacitor module  500 . 
     On the other hand, DC power converted by the inverter circuit  140  from AC power is supplied to the capacitor module  500  from the positive electrode-side capacitor terminal  506  and the negative electrode-side capacitor terminal  504 , supplied to the battery  136  via the DC connector  138  from the positive electrode-side power source terminal  509  and the negative electrode-side power source terminal  508 , and stored in the battery  136 . 
     The control circuit  172  includes a microcomputer for calculating a switching timing of the IGBT  328  and the IGBT  330 . As input information, a target torque value required for the motor generator MG 1 , a value of a current to be supplied from the series circuit  150  to the motor generator MG 1 , and a magnetic pole position of a rotor of the motor generator MG 1  are input to the microcomputer. 
     The target torque value is based on a command signal output from an upper control device (not illustrated). A current value is detected based on a detection signal by a current sensor  180 . A magnetic pole position is detected based on a detection signal output from a rotation magnetic pole sensor (not illustrated) such as a resolver provided to the motor generator MG 1 . In the embodiment, a case is exemplified where the current sensor  180  detects current values of three phases. However, current values for two phases may be detected, and currents for three phases may be calculated. 
     A microcomputer in the control circuit  172  calculates a current command value of d and q axes of the motor generator MG 1  based on a target torque value. The microcomputer calculates voltage command values of the d and q axes based on a difference between the calculated current command values of the d and q axes and detected current values of the d and q axes and converts the calculated voltage command values of the d and q axes are converted into voltage command values of the U, V, and W phases based on the detected magnetic pole position. Then, the microcomputer generates pulsed modulated waves based on a comparison between a basic wave (sine wave) and a carrier wave (a triangle wave) based on the voltage command values of the U, V, and W phases and outputs the generated modulated wave to the driver circuit  174  as a pulse width modulation (PWM) signal. 
     In the case of driving a lower arm, the driver circuit  174  outputs a drive signal amplifying the PWM signal to a gate electrode of the IGBT  330  of a corresponding lower arm. In addition, in the case of driving an upper arm, the driver circuit  174  shifts a level of a reference potential of the PWM signal to a level of a reference potential of the upper arm, amplifies the PWM signal, and output the amplified signal to each gate electrode of the IGBT  328  of a corresponding upper arm as a drive signal. 
     Temperature information on the series circuit  150  is input from a temperature sensor (not illustrated) provided to the series circuit  150  to a microcomputer. Further, voltage information on a DC positive electrode side of the series circuit  150  is input to the microcomputer. The microcomputer detects an excessive voltage and an excessive voltage based on the information, and in the case where an excessive voltage or an excessive voltage is detected, switching operations of all of the IGBT  328  and the IGBT  330  are stopped. 
     Configurations of semiconductor modules  300   a  to  300   c  to be used in the inverter circuit  140  will be described with reference to  FIGS. 3 to 6 . The above-described semiconductor modules  300   a  to  300   c  (refer to  FIG. 2 ) have the same structure, and therefore a structure of the semiconductor module  300   a  (hereinafter called a semiconductor module  300 A) will be representatively described. 
       FIGS. 3( a ) and 3( b )  are perspective views of the semiconductor module  300 A.  FIG. 3( c )  is a sectional schematic view of the semiconductor module  300 A.  FIG. 3( a )  is a sectional schematic view cut on line IVa-IVa. In  FIG. 3( c ) , component members indicated on a sectional surface cut on line IVb-IVb are also denoted by reference signs.  FIG. 4  is a circuit diagram illustrating a circuit configuration of the semiconductor module  300 A.  FIG. 5  is a perspective view of a conductor plate assembly  950  excluding an epoxy resin  348  (sealing resin) of the semiconductor module  300 A for clarification.  FIG. 6  is a perspective view of the conductor plate assembly  950  excluding a first conductor plate  315  and a third conductor plate  320  illustrated in  FIG. 5 . 
     As illustrated in  FIG. 3( c ) , the semiconductor module  300 A includes power semiconductor devices (the IGBT  328 , the IGBT  330 , the diode  156 , and the diode  166 ) forming the series circuit  150  illustrated in  FIGS. 2 and 4 . These power semiconductor devices are sealed by a sealing resin including the epoxy resin  348 . 
     A circuit configuration of a semiconductor module will be described with reference to  FIG. 4 . As illustrated in  FIG. 4 , a collector electrode of the IGBT 328  on an upper arm side and a cathode electrode of the diode  156  on the upper arm side are connected via the first conductor plate  315 . Similarly, a collector electrode of the IGBT  330  on a lower arm side and a cathode electrode of the diode  166  on the lower arm side are connected via the third conductor plate  320 . An emitter electrode of the IGBT  328  on the upper arm side and an anode electrode of the diode  156  on an upper arm side are connected via the second conductor plate  318 . Similarly, an emitter electrode of the IGBT  330  on a lower arm side and an anode electrode of the diode  166  on the lower arm side are connected via a fourth conductor plate  319 . The second conductor plate  318  and the third conductor plate  320  are connected by the intermediate electrode  329 . The series circuit  150  of upper and lower arms are formed by such circuit configuration. 
     As illustrated in  FIGS. 3( c )  and  6 , a power semiconductor device (the IGBT  328 , the IGBT  330 , the diode  156 , and the diode  166 ) has a plate flat structure, and each electrode of the power semiconductor device is formed on front and back surfaces. 
     As illustrated in  FIGS. 3( c )  and  5 , each electrode of the power semiconductor device is sandwiched by the first conductor plate  315  and the second conductor plate  318  or the third conductor plate  320  and the fourth conductor plate  319 , which are disposed so as to face each electrode surface. Specifically, the first conductor plate  315  and the second conductor plate  318  are laminated so as to face in substantially parallel via the IGBT  328  and the diode  156 . Similarly, the third conductor plate  320  and the fourth conductor plate  319  are laminated so as to face in substantially parallel via the IGBT  330  and the diode  166 . As illustrated in  FIG. 5 , the third conductor plate  320  and the second conductor plate  318  are connected via the intermediate electrode  329 . By this connection, an upper arm circuit and a lower arm circuit are electrically connected, and an upper/lower arm series circuit is formed. 
     The first conductor plate  315  on a DC side and the third conductor plate  320  on an AC side are disposed on the substantially same plane. The first conductor plate  315  is fixed to a collector electrode of the IGBT 328  on an upper arm side and a cathode electrode of the diode  156  on the upper arm side. The third conductor plate  320  is fixed to a collector electrode of the IGBT  330  on a lower arm side and a cathode electrode of the diode  166  on the lower arm side. Similarly, the second conductor plate  318  on an AC side and the fourth conductor plate  319  on a DC side are disposed on the substantially same plane. The second conductor plate  318  is fixed to an emitter electrode of the IGBT  328  on an upper arm side and an anode electrode of the diode  156  on the upper arm side. The fourth conductor plate  319  is fixed to an emitter electrode of the IGBT  330  on a lower arm side and an anode electrode of the diode  166  on the lower arm side. 
     A DC positive electrode terminal  157  extends from the first conductor plate  315 . The AC terminal  159  extends from the second conductor plate  318 . A DC negative electrode terminal  158  extends from the fourth conductor plate  319 . 
     Each of the conductor plates  315 ,  318 ,  319 , and  320  according to the embodiment is a wiring for a large current circuit and includes a material having a high heat conductivity and a low electrical resistance such as pure copper or copper alloy, and the thickness is preferably equal to or greater than 0.5 mm. 
     As illustrated in  FIG. 3( c ) , a power semiconductor device is bonded to each of the conductor plates  315 ,  318 ,  319 , and  320  via a metal bonding material  160 . The metal bonding material  160  is, for example, a low-temperature sintered bonding material including a silver sheet and fine metal particles, or a lead-free solder having a high heat conductivity and excellent in environmental properties such as a Sn—Cu solder, a Sn—Ag—Cu solder, and a Sn—Ag—Cu—Bi solder. 
     Gate electrode terminals  154  and  164  and the emitter electrode terminals  155  and  165  for connecting to the driver circuit  174  are connected to a gate electrode and an emitter electrode of a power semiconductor device by such as wire bonding and ribbon bonding. Aluminum and gold are preferably used for a wire and a ribbon. Instead of the wire and the ribbon, a solder may be used for bonding. Pure copper or copper alloy is preferably used in the gate electrode terminals  154  and  164  and the emitter electrode terminals  155  and  165 . The DC positive electrode terminal  157 , the DC negative electrode terminal  158 , the AC terminal  159 , the gate electrode terminals  154  and  164 , the emitter electrode terminals  155  and  165 , and other terminals for current detection and temperature detection are arranged in a row and integrally held by being connected by a tie bar  951  including insulating resin at predetermined intervals. 
     As illustrated in  FIGS. 3( c )  and  5 , the semiconductor module  300 A includes a heat dissipating fin  371 . As illustrated in  FIG. 3( c ) , the heat dissipating fin  371  includes a fin plate  371   a  and a reinforcement plate  371   b  to enhance rigidity of the fin plate  371   a . The fin plate  371   a  includes a rectangular flat plate base and a plurality of columnar fins projected on a surface of the base. The reinforcement plate  371   b  is a rectangular flat plate. An outer shape of the reinforcement plate  371   b  is substantially same as an outer shape of the base of the fin plate  371   a . The base of the fin plate  371   a  and the reinforcement plate  371   b  are positioned and bonded so as to be flush with an outer peripheral-side surface of the base of the fin plate  371   a  and an outer peripheral-side surface of the reinforcement plate  371   b.    
     The semiconductor module  300 A is disposed in a case  122 . The heat dissipating fin  371  exchanges heat with a refrigerant  121  in the case  122 , and heat generated in the semiconductor module is radiated into the refrigerant  121 . The refrigerant  121  flows in a direction orthogonal to a projecting direction of each fin from the base and circulates in the case  122  by a circulator (not illustrated). 
     An insulating plate  389  having insulation properties is bonded on outer side surfaces of the second conductor plate  318  and the fourth conductor plate  319  (surface on an opposite side of a bonding surface of a semiconductor device), and the reinforcement plate  371   b  is bonded on an outer side surface of the insulating plate  389 . After transfer molding to be described later, the fin plate  371   a  is bonded on an exposed surface of the reinforcement plate  371   b . Specifically, a surface of the fin plate  371   a  on which a fin is formed is exposed from the epoxy resin  348  which is a sealing member. The insulating plate  389  includes an inorganic compound such as insulating ceramic and an organic compound such as insulating resin. The insulating plate  389  is disposed between the heat dissipating fin  371  and the conductor plates  318  and  319  and insulates both of them. A material having a high heat conductivity is preferably selected for a material of the insulating plate  389 . In the case where the insulating plate  389  is formed of resin, the insulating plate  389  is preferably connected to the conductor plates  318  and  319  and the reinforcement plate  371   b  in a state before resin components are completely cured, specifically in an adhesive state. In the case where the reinforcement plate  371   b  and the fin plate  371   a  forming the heat dissipating fin  371  are formed of an insulating material, the insulating plate  389  can be omitted. 
     The reinforcement plate  371   b  and the fin plate  371   a  are made of a metal material having a higher heat conductivity than the epoxy resin  348  used in a sealing resin, such as aluminum, copper, and magnesium, and a ceramic material such as alumina. A material having higher rigidity than a material of the fin plate  371   a  is preferably selected for a material of the reinforcement plate  371   b . In the embodiment, different materials are selected for the reinforcement plate  371   b  and the fin plate  371   a.    
     The second conductor plate  318  or the fourth conductor plate  319 , the insulating plate  389 , the reinforcement plate  371   b , and the fin plate  371   a  are boned by a method such as welding, soldering, and friction stir welding (FSW). If the strength of the fin plate  371   a  is sufficient, the reinforcement plate  371   b  can be omitted. 
     The second conductor plate  318  and the fourth conductor plate  319  are bonded to the heat dissipating fin  371  via an insulating plate  389  in a heat conductive manner. Heat generated in the semiconductor devices  156 ,  166 ,  328 , and  330  is transferred to the second conductor plate  318  or the fourth conductor plate  319 , transferred to the heat dissipating fin  371  via the insulating plate  389 , and radiated into the refrigerant  121  from the heat dissipating fin  371 . 
     A manufacturing method for the semiconductor module  300 A according to the first embodiment will be described. First, the semiconductor structure  302  is formed by molding the conductor plate assembly  950  illustrated in  FIG. 5  by using the insulating epoxy resin  348  by such as a transfer molding method. In the transfer molding method, the conductor plate assembly  950  is fixed in a preliminary heated mold, and molding is performed by injecting pressure in a mold while melting curable resin such as epoxy resin. Consequently, the conductor plate assembly  950  including a power semiconductor device is sealed by a sealing resin, and the semiconductor structure (module sealing body)  302  illustrated in  FIG. 7  is formed. When transfer molding is performed, an outer side surface (a surface opposite to a bonding surface with the insulating plate  389 ) of the reinforcement plate  371   b  is exposed by the sealing resin  348 . As illustrated  FIGS. 3 and 3 ( c ), the sealing resin  348  includes a terminal surface  348   a  disposed in a state in which terminals  157 ,  158 ,  159 ,  154 ,  155 ,  164 , and  165  are mutually insulated. 
     Subsequently, after the semiconductor structure  302  is set in a reaction tube, a surface of an epoxy resin portion is directly fluorinated in a fluorine gas atmosphere, and a first layer  602  in which a substitution ratio is 0.8 is formed approximately five μm (refer to  FIG. 3( c ) ). In the embodiment, the first layer  602  is formed on an outer surface of the semiconductor structure  302 . A region formed on the first layer  602  is a region including the whole of a contact region of the refrigerant  121  in the semiconductor structure  302 . Herein, the substitution ratio means C—F coupling/(C—H coupling+C—F coupling) in the main chain structure. 
     The semiconductor module  300 A manufactured in this manner is excellent in adhesion with internal electronic components sealing such as a conductor plate since epoxy resin is not fluorinated during molding. Further, 80% of hydrogen bonded to carbon of the first layer  602  is substituted with fluorine, and an average free volume in a three-dimensional crosslinking structure is sealed with fluorine to prevent entry of a refrigerant. 
     On the other hand, when the conductor plate assembly  950  is molded, if a hydrophobic group is introduced into a sealing resin, the sealing resin is easily repelled and has poor wettability and poor adhesion with internal electronic components to seal a diode, an IGBT, and a conductor plate. When such a sealing resin is used as an insulator, peeling from such as a conductor and a void in a sealing molding body are occurred when heat curing is performed. Consequently, water may accumulate, and insulation may be reduced. 
     In the present invention, epoxy resin used in an integrated molding is not especially limited as long as a curable resin component capable of sealing molding is used. However, epoxy resin components are preferably used in which an epoxy resin, a curing agent, a curing accelerator, and an inorganic filler are essential components. 
     In the embodiment, a fluorine atom is selected such that a length calculated by cube root of an average free volume in the three-dimensional crosslinking structure of the first layer  602  is shorter than a length of the longest side of molecules forming the refrigerant. However, it is not limited as long as the fluorine atom can be substituted. To prevent entry of a refrigerant, elements having water repellency when being substituted is further preferable. For example, halogen elements such as fluorine, bromine, chlorine, and iodine are used. 
     A glass transition temperature of resin having the three-dimensional crosslinking structure of the first layer  602  is preferably equal to or greater than 50° C. Although it depends on an application temperature range of an electronic device, when the three-dimensional crosslinking structure becomes movable (a rubber state) by heat at the glass transition temperature or higher. Therefore, even if an average free volume is sealed by elements such as fluorine, entry of a refrigerant may not be prevented. Ina semiconductor apparatus represented by such as a high pressure module for such as an inverter for a hybrid vehicle, a glass transition temperature of resin having a three-dimensional crosslinking structure of the first layer  602  is preferably equal to or greater than 130° C. 
     A three-dimensional curing structure of a first layer will be described with reference to  FIGS. 8( a ) to 8( c ) .  FIG. 8( a )  indicates a model of the three-dimensional crosslinking structure. As illustrated in  FIG. 8( a ) , in a three-dimensional curable resin, a main chain  600  of resin is joined at a crosslinking point  601 . In fact, although the curable resin has three-dimensional network structure like a mesh, for clarification, one curable resin is exemplified in  FIGS. 8( b ) and 8( c ) , and fluorine processing is described as an example.  FIG. 8( b )  is a schematic view of a three-dimensional curable resin before the fluorine processing. A structure of the main chain  600  of resin includes hydrogen bonded to carbon which is a main chain skeleton. A gap in a mesh structure surrounded by the main chain  600  of resin and the crosslinking point  601  is an average free volume V 0  before the fluorine processing.  FIG. 8( c )  is a schematic view of the three-dimensional curable resin after the fluorine processing. In a structure of the main chain  600  of resin, hydrogen bonded to carbon which is a main chain skeleton is substituted with fluorine which is a larger element than hydrogen. Consequently, an average free volume V 0  becomes V 1 , and the average free volume V 1  after processing becomes smaller than the average free volume V 0  before processing. 
     That is, a gap opened before the processing is sealed by fluorine. As a substitution ratio is increased, an average free volume is decreased. Therefore, it is effective to increase a level of the substitution ratio to prevent entry of a refrigerant. In addition, even if an average free volume of the first layer  602  is not completely sealed by an element such as halogen, a waterproof property can be improved if a length calculated by cube root of the average free volume in a three-dimensional crosslinking structure is not shorter than a length of the longest side of molecules forming the refrigerant. This is because, even if a refrigerant enters, when the calculated length is shorter than a length of the longest side of molecules forming the refrigerant, a freedom degree is decreased, and a pressure required for entry of the refrigerant generates, and the refrigerant cannot enter into a sealed conductor. 
     The semiconductor module  300 A according to the above-described first embodiment includes the semiconductor structure  302  and the first layer  602 . The semiconductor structure  302  includes semiconductor devices  328 ,  330 ,  156 , and  166 , the conductor plates  318  and  319 , the heat dissipating fin  371 , and the epoxy resin  348 . A semiconductor device is bonded to the conductor plates  318  and  319 . The heat dissipating fin  371  is fixed to the semiconductor device via the conductor plates  318  and  319  and the insulating plate  389  in a heat conductive manner. The epoxy resin  348  seals the semiconductor device by exposing one surface of the heat dissipating fin  371 . The first layer  602  at least covers a boundary with the epoxy resin  348  in a contact region of the refrigerant  121 . 
     The first layer  602  having a three-dimensional crosslinking structure is sealed by elements of the first layer  602  such that a length calculated by cube root of an average free volume in the three-dimensional crosslinking structure is shorter than a length of the longest side of molecules forming the refrigerant. 
     By forming the first layer  602 , it is prevented that the refrigerant  121  enters into the sealing resin  348 . Therefore, a life of the semiconductor module  300 A can be extended. Even if entry of the refrigerant cannot be completely prevented, and the refrigerant enters, if the calculated length is shorter than a length of the longest side of molecules forming the refrigerant, a freedom degree is decreased, and a pressure required for entry of the refrigerant generates, and a waterproof property is improved. 
     Second Embodiment 
     A semiconductor module  300 B according to a second embodiment will be described with reference to  FIGS. 9 and 10 .  FIG. 9  is a view similar to  FIG. 3( a )  and a perspective view of the semiconductor module  300 B according to the second embodiment.  FIG. 10  is a view similar to  FIG. 3( c )  and a sectional schematic view of the semiconductor module  300 B according to the second embodiment. In the drawings, components same as or corresponding to those in the first embodiment are denoted by the same reference sign, and a description thereof is omitted. A point difference from the first embodiment will be described in detail below. 
     In the first embodiment, an example has been described in which the heat dissipating fin  371  is provided on a surface on one side of the semiconductor module  300 A. In the second embodiment, the heat dissipating fins  371  are provided on both surfaces of the semiconductor module  300 B. 
     As illustrated in  FIG. 10 , an insulating plate  389  is bonded on an outer side surface of a first conductor plate  315  and a third conductor plate  320 . A reinforcement plate  371   b  is bonded on an outer surface of the insulating plate  389 . After transfer molding, a fin plate  371   a  is bonded on an exposed surface of the reinforcement plate  371   b . The insulating plate  389  includes inorganic compounds such as insulating ceramic and organic compounds such as insulating resin, and the insulating plate  389  is disposed between the heat dissipating fin  371  and the conductor plates  315  and  320  and insulates both of them. A material having a high heat conductivity is preferably selected for a material of the insulating plate  389 . In the case where the insulating plate  389  is formed of resin, the insulating plate  389  is preferably connected to the conductor plates  315   320  and the reinforcement plate  371   b  in a state before resin component is completely cured, in other words, in an adhesive state. In the case where the reinforcement plate  371   b  and the fin plate  371   a  forming the heat dissipating fin  371  are formed of an insulating material, the insulating plate  389  can be omitted. 
     The reinforcement plate  371   b  and the fin plate  371   a  are made of a metal material, which has a higher heat conductivity than a material used in the sealing resin  348 , such as aluminum, copper, and magnesium, and a ceramic material such as alumina. A material having higher rigidity than a material of the fin plate  371   a  is preferably selected for a material of the reinforcement plate  371   b.    
     The first conductor plate  315  or the third conductor plate  320  and the insulating plate  389 , the reinforcement plate  371   b , and the fin plate  371   a  are boned by a method such as welding, soldering, and FSW. If the strength of the fin plate  371   a  is sufficient, the reinforcement plate  371   b  can be omitted. 
     According to such the second embodiment, operation effects similar to the effects in the first embodiment are obtained. In comparison with the first embodiment, a heat radiation area of the heat dissipating fin  371  is increased, and therefore, cooling performance can be improved in comparison with the first embodiment. 
     Third Embodiment 
     A semiconductor module  300 C according to a third embodiment will be described with reference to  FIG. 11 .  FIG. 11  is a view similar to  FIG. 3( c )  and a sectional schematic view of the semiconductor module  300 C according to the third embodiment. In the drawings, components same as or corresponding to those in the first embodiment are denoted by the same reference sign, and a description thereof is omitted. A point difference from the first embodiment will be described in detail below. 
     In the first embodiment, each terminal is disposed on one terminal surface  348   a . However, in the third embodiment, a terminal is disposed on a surface opposite to the terminal surface  348   a  (hereinafter called another terminal surface  348   b ). In the third embodiment, a DC negative electrode terminal  158 , a DC positive electrode terminal  157 , and an AC terminal  159 , gate electrode terminals  154  and  164 , and emitter electrode terminals  155  and  165 , which are illustrated in  FIG. 4  extends from the terminal surface  348   a , and a current detecting terminal  190  extends from another terminal surface  348   b.    
     In the third embodiment, as illustrated in  FIG. 11 , two terminal surfaces  348   a  and  348   b  are exposed. Specifically, the first layer  602  is not formed on two terminal surfaces  348   a  and  348   b . Therefore, in comparison with the first embodiment, an area on which the first layer  602  is not formed increases. In the third embodiment, terminals and two terminal surfaces  348   a  and  348   b  are covered by a curing member, the first layer  602  is formed by coating solution, and the curing member is removed. 
     According to such the third embodiment, operation effects similar to the effects in the first embodiment can be obtained. In comparison with the first embodiment, an area in which the first layer  602  is formed is decreased, and therefore costs and a weight can be reduced. 
     A deformation to be described below is within a range of the present invention, and one or a plurality of the variations can be combined with the above-described embodiments. 
     First Variation 
     It has been exemplified in the above-described embodiments that the first layer  602  is formed by directly fluorinating an epoxy resin which is a sealing member. However, the present invention is not limited thereto. The first layer  602  can be formed by direct fluorine processing after various types of curable resin such as polyimide, polyimidazole, phenol resin, melamine resin, and epoxy resin having a different structure from a structure used in the sealing member are formed instead of the epoxy resin which is a sealing member. A region excellent in chemical resistance with respect to a refrigerant and heat resistance is preferably selected for a region in which the first layer  602  is formed while considering that the region includes the whole of a contact region of the refrigerant  121  in the semiconductor structure  302 . 
     For example, 20 weight % polyimide dimethylformamide solution is prepared, and then a surface of the semiconductor structure  302  is coated by using this coating solution. Polyimide of the first layer  602  is formed by performing heat curing for 1 hour at 100° C. and 150° C. Further, by direct fluorine processing, a part of hydrogen bonded to carbon of the first layer is substituted with fluorine such that a length calculated by cube root of an average free volume in a three-dimensional crosslinking structure is shorter than a length of the longest side of molecules forming the refrigerant. 
     It has been exemplified that the first layer  602  is formed by a dipping method to dip in the coating solution. However, the present invention is not limited thereto. A method for coating the coating solution is not limited to the dipping method. The first layer  602  may be formed by coating a coating solution on the semiconductor structure  302  by using a spray and a brush. Dipping, spraying, and brushing, ora combination thereof can be used. In the case where embedding is insufficient, it is improved by recoating. 
     Second Variation It has been exemplified in the above-described embodiments that the first layer  602  is formed in a region including the whole of a contact region of the refrigerant  121  in the semiconductor structure  302 . However, the present invention is not limited thereto. The first layer  602  may be formed in an epoxy resin portion, not on a surface of the epoxy resin portion sealing such as a conductor. 
     Third Variation 
     It has been exemplified in the above-described embodiments that the first layer  602  is formed by directly fluorinating an epoxy resin which is a sealing member by using fluorine gas. However, the present invention is not limited thereto. The first layer  602  may be formed by surface fluorine processing by a radical reaction. For example, after a solution having a fluoride radical reaction is adjusted to a constant concentration, the semiconductor structure  302  is dipped in this coating solution for coating. Then, by heating the semiconductor structure  302  at 100° C. for three hours, a part of a main chain skeleton is fluorinated. 
     Fourth Variation 
     It has been exemplified in the above-described embodiments that the first layer  602  is formed in the whole of a contact region of the refrigerant  121  in the sealing resin  348 . However, the present invention is not limited thereto. The first layer  602  may be provided at least so as to cover a boundary between the sealing resin  348  and the heat dissipating fin  371 . Consequently, by coating the boundary between different-type members, it is prevented that a refrigerant enters from the boundary between different-type members, and a waterproof property is improved. 
     Fifth Variation 
     It has been exemplified in the above-described embodiments that the first layer  602  is formed in the whole of a contact region of the refrigerant  121  in the sealing resin  348 . However, the present invention is not limited thereto. The first layer  602  may be provided in the whole of a region contacting to the refrigerant  121  in the sealing resin  348  and the heat dissipating fin  371 . Consequently, by forming the first layer  602  in the heat dissipating fin  371  in addition to the sealing resin  348 , a pinhole and a flaw of a fin portion are covered, a waterproof property is improved, and long reliability can be secured. However, it is necessary to select a coating type and a film thickness of the first layer  602  while considering a heat dissipation property of the heat dissipating fin  371 . 
     Sixth Variation 
     It has been exemplified in the above-described embodiments that, by directly fluorinating the first layer  602 , a part of hydrogen bonded to carbon of the first layer is substituted with fluorine such that a length calculated by cube root of an average free volume in a three-dimensional crosslinking structure is shorter than a length of the longest side of molecules forming the refrigerant. However, the present invention is not limited thereto. Hydrogen may be substituted with bromide and chlorine instead of fluorine. 
     Seventh Variation 
     A power converter (inverter) has been exemplified as an electronic control device in the above-described embodiments. However, the present invention is not limited thereto. The present invention can be applied to various types of electronic control devices including electronic components. 
     As long as characteristics of the present invention are not impaired, the present invention is not limited to the above-described embodiments. Other embodiments envisaged within the scope of technical ideas of the preset invention are included in the scope of the present invention. 
     REFERENCE SIGNS LIST 
     
         
           21  connector 
           121  refrigerant 
           122  case 
           136  battery 
           138  DC connector 
           140  inverter circuit 
           150  series circuit 
           153  collector electrode terminal 
           154  gate electrode terminal 
           155  emitter electrode terminal 
           156  diode 
           157  DC positive electrode terminal 
           158  DC negative electrode terminal 
           159  AC terminal 
           160  metal bonding material 
           163  collector electrode terminal 
           164  gate electrode terminal 
           165  emitter electrode terminal 
           166  diode 
           169  intermediate electrode 
           172  control circuit 
           174  driver circuit 
           180  current sensor 
           188  AC terminal 
           190  current detecting terminal 
           200  power converter 
           300 A,  300 B,  300 C,  300 D semiconductor module 
           302  semiconductor structure 
           315  first conductor plate 
           318  second conductor plate 
           319  fourth conductor plate 
           320  third conductor plate 
           328  IGBT 
           329  intermediate electrode 
           330  IGBT 
           348  epoxy resin 
           348   a ,  348   b  terminal surface 
           371  heat dissipating fin 
           371   a  fin plate 
           371   b  reinforcement plate 
           389  insulating plate 
           500  capacitor module 
           504  capacitor terminal 
           506  capacitor terminal 
           508  power source terminal 
           509  power source terminal 
           600  main chain of resin 
           601  crosslinking point 
           602  first layer 
           603  main chain of resin substituted with halogen 
           802  AC bus bar 
           950  conductor plate assembly 
           951  tie bar