Abstract:
A power module of the present invention mounts electronic components and comprises a circuit board that constitutes an electric power conversion circuit along with the above-mentioned electronic components; a heat sink; and a member with insulation characteristics and high thermal conductivity, which is disposed between plural devices with high heating value among the above-mentioned electronic components and the above-mentioned heat sink, embeds at least part of each of the above-mentioned plural devices with high heating value therein and transfers heat from the above-mentioned plural devices with high heating value to the above-mentioned heat sink.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    The present invention relates to an on-board type power module.  
           [0002]    Recently, in developing electronic equipment that meets demand toward miniaturization in the market, measures for heat dissipation of heating components mounted on a board at high density (ex. electronic components such as semiconductor device) have increasingly become important. Especially in a power module, since insufficient heat dissipation of components can impair reliability of the components, measures for heat dissipation are extremely important in order to suppress temperature rise due to heat generation of power conversion devices mounted at high density and the like.  
           [0003]    As measures for heat dissipation, prior art power modules have adopted a forced air-cooling system with fan or a heat transfer cooling system wherein a high thermal conductive heat sink is pressed onto heating components, thereby to efficiently transfer heat from the heating components to the heat sink for cooling them.  
           [0004]    Various electronic components requiring heat dissipation such as MOSFET (MOS (metal-oxide semiconductor) field-effect transistor), transformer, choke, IC for power supply circuit and the like are mounted on a circuit board of a power module. These electronic components vary in shape and height, thereby to generate difference in level among them. There are variations in heights of the components themselves as well as mounted heights of the components on the circuit board. For that reason, even if a heat sink is pressed onto plural heating components, it is difficult to bring all components into coherent with the heat sink evenly. Therefore, it is necessary to accommodate difference in level and height among the heating components and bring the electronic components requiring heat dissipation into coherent with the heat sink so as to ensure heat transfer between them.  
           [0005]    In order to solve this problem, Patent Publication No. 2536657 describes a prior art electronic apparatus that comprises a heat sink having depressed portions for accommodating components mounted on a multi-layer board depending on positions and heights of the components. The prior art electronic apparatus disclosed in Patent Publication No. 2536657 will be described below. FIG. 19 is a sectional view of the circuit board disclosed in the above-mentioned Patent Publication.  
           [0006]    In FIG. 19, conductors  21   a  are provided with a circuit board  21  in a predetermined pattern. A resistance  22  as an electronic component with high heating value, a cement resistance  23  with especially high heating value, an electrolytic capacitor  26  as an electronic component with low heating value, a power module  27  with high heating value and the like are fixed to the circuit board  21  by soldering  25 . A reference numeral  20  denotes a base made of aluminum die cast. The base  20  has depressed portions  20   a  for inserting the components  22 ,  23 ,  26 ,  27 , respectively, depending on position, height and shape thereof so as to make space between the base  20  and each component substantially same.  
           [0007]    A copper cover  28  having the same shape as outline of the cement resistance  23  lies between the cement resistance  23  and the depressed portion  20   a . A high thermal conductive resin  29  is filled in each space (depressed portion  20   a ) between the resistance  22 , cement resistance  23  and power module  27 , respectively, all of which have a high heating value, and the base  20 . A heat-insulating resin  30  is filled in the space (depressed portion  20   a ) between the electrolytic capacitor  26  with low heating value and the base  20 .  
           [0008]    A reference numeral  31  denotes a terminal part of each component, a reference numeral  32  denotes a nut for electrically bonding the terminal part  31  to the conductor  21   a  of the circuit board  21 , a reference numeral  33  denotes a fastening screw for electrically connecting the terminal part  31  to the conductor  21   a  of the circuit board  21 , and a reference numeral  34  denotes a holding member for holding the circuit board  21  on the base  20 .  
           [0009]    In other words, the prior art electronic apparatus enables efficient heat transfer, since both the tall and short components with high heating value are adhered to the heat sink evenly.  
           [0010]    In the prior art example, however, there causes a problem of complicating configuration of the heat sink. The heat sink must be designed so as to have convexocancave that correspond to any difference in level ranging from large to minute differences in response to the components of various heights that are mounted on the circuit board. A mold for the heat sink with complicated shape is expensive. In the case of highly complicated shaped heat sink, aluminum die cast drawn from the mold needs to be processed thereafter. Thus, it is impossible to design the heat sink until the pattern of the circuit board and components attached thereto have been determined, and production of the mold for the complicated heat sink takes a long time, thereby to cause delay in going on the market. Moreover, once the shape of heat sink has been established, it becomes difficult to change electronic components on the multi-layer board or their positions. These problems have resulted in prolongation of development period and increase in production cost.  
           [0011]    An object of the present invention is to provide a power module that has structural characteristics including good heat dissipation, high thermal resistance reliability, low-cost and high productivity.  
           [0012]    Another object of the present invention is to provide a power module that efficiently takes heat generated from components of various heights, which are mounted on the circuit board, by use of a multipurpose heat sink or a simple-shaped heat sink.  
           [0013]    Another object of the present invention is to provide a lightweight power module due to miniaturization and weight saving of heat dissipation member.  
         BRIEF SUMMARY OF THE INVENTION  
         [0014]    In order to solve the problem, the present invention has a following configuration. A power module in accordance with the present invention from one aspect is a power module that comprises a circuit board that mounts electronic components and constitutes an electric power conversion circuit along with the above-mentioned electronic components; a heat sink; and a member with insulation characteristics and high thermal conductivity, which is disposed between plural devices with high heating value among the above-mentioned electronic components and the above-mentioned heat sink, embeds at least part of each of the above-mentioned plural devices with high heating value therein and transfers heat from the above-mentioned plural devices with high heating value to the above-mentioned heat sink.  
           [0015]    The present invention has the effect of achieving a power module that efficiently transfers heat generated from the mounted electronic components requiring heat dissipation to the heat sink via the high heat conductive member (such as resin material). Hence, temperature rise of the components can be suppressed.  
           [0016]    According to the present invention, since there is no need to form convexoconcave on the surface of the heat sink depending on shape of the components mounted to the multi-layer board, a cheap multipurpose heat sink (for example, one side has a heat radiating fin and the opposite side is flat) or a simple-shaped heat sink (for example, a shape of folded aluminum plate) can be utilized. Since it is unnecessary to subject the heat sink to any special process, a cheap power module with high productivity can be achieved.  
           [0017]    By fixing the cheap heat sink to the heating components having various heights via the high thermal conductive member (such as resin material), heat generated from the components having various heights can be transferred to the heat sink efficiently with high reliability (the components and the high thermal conductive member, as well as the high thermal conductive member and the heat sink are brought into coherent with each other certainly).  
           [0018]    There is no need to change shape of the heat sink depending on location, shape and size of the components mounted to the circuit board. Since heat sink design or mold manufacturing do not take long time, development of power module can be facilitated.  
           [0019]    The present invention has the effect of achieving a power module that has constitutional characteristics including good heat dissipation, high thermal resistance reliability, low cost and high productivity.  
           [0020]    The present invention has the effect of achieving a power module that efficiently takes heat occurring in the components having various heights mounted to the circuit board by use of a multipurpose heat sink or a simple-shaped heat sink.  
           [0021]    A power module in accordance with the present invention from another aspect is a power module wherein the above-mentioned member provides space with respect to the above-mentioned circuit board at the part that is not adhered to the above-mentioned electronic components and remains substantially uniform in thickness at the part.  
           [0022]    As the electronic components become miniaturized and their mounting becomes densified, there can cause a problem that voids remain at the boundary area between the member and the board, and the electronic components with high heating value do not stick fast to the member adequately due to the voids. According to the present invention, space between the member and the circuit board exists and therefore there is no fear of leaving voids. The present invention has the effect of ensuring adhesiveness between the electronic components with high heating value and the member, thereby to achieve a power module with high reliability.  
           [0023]    A power module in accordance with the present invention from another aspect is a power module wherein the above-mentioned heat sink has a depressed portion and the above-mentioned member is filled in the above-mentioned depressed portion.  
           [0024]    By flowing the unhardened member (such as resin) into the depressed portion, the heating components can be embedded in the member, while preventing the member from flowing out.  
           [0025]    A power module in accordance with the present invention from another aspect is a power module wherein the above-mentioned member has thermosetting resin and inorganic filler as chief ingredients.  
           [0026]    By bringing a thermosetting resin composition with high thermal conductivity as the member into coherent with the electronic components, thermal resistance of the electronic components requiring heat dissipation can be reduced. Adhering the high thermal conductive member to the heat sink and unifying them can reduce contact thermal resistance between the member and the heat sink. Hence, it is possible to provide a power module that is excellent in heat dissipation.  
           [0027]    A power module in accordance with the present invention from another aspect is a power module wherein a short component in height is mounted to the side of the above-mentioned circuit board, which is opposed to the above-mentioned heat sink.  
           [0028]    Hence, it is possible to achieve a thin power module having good heat radiating characteristic. Reducing variation of the components in height makes interval between each component and the heat sink substantially uniform, thereby to enable eliminating deviation in heat dissipation.  
           [0029]    A power module in accordance with the present invention from another aspect is a power module wherein both sides of the above-mentioned circuit board have the above-mentioned heat sink and the above-mentioned member respectively. The present invention has the effect of achieving a power module with good heat dissipation at both sides.  
           [0030]    A production method of a power module in accordance with the present invention from another aspect is a production method that comprises a mounting step of mounting electronic components to at least a first side; a laminating step of forming a laminated body wherein an unhardened member with insulation characteristics and high thermal conductivity and a heat sink are laminated on the above-mentioned first side of the above-mentioned circuit board; and an adhering step of pressurizing and heating the above-mentioned laminated body, hardening the above-mentioned member and adhering the above-mentioned circuit board, the above-mentioned member and the above-mentioned heat sink to each other.  
           [0031]    The present invention has the effect of achieving a power module that has constitutional characteristics including good heat dissipation, high thermal resistance reliability, low cost and high productivity.  
           [0032]    The present invention has the effect of achieving a power module that efficiently takes heat occurring in the components having various heights mounted to the circuit board by use of a multipurpose heat sink or a simple-shaped heat sink.  
           [0033]    A production method of a power module in accordance with the present invention from another aspect is a production method that comprises a mounting step of mounting electronic components to both sides of a circuit board; a laminating step of forming a laminated body wherein an unhardened member with insulation characteristics and high thermal conductivity and a heat sink are laminated on both sides of the above-mentioned circuit board simultaneously; and an adhering step of pressurizing and heating the above-mentioned laminated body, hardening the above-mentioned member and adhering the above-mentioned circuit board, the above-mentioned member and the above-mentioned heat sink to each other.  
           [0034]    The present invention has the effect of achieving a method for producing the power module with good heat dissipation characteristic and high thermal resistance reliability, in which the electronic components are mounted to both sides of the circuit board, at low cost and less steps.  
           [0035]    A production method of a power module in accordance with the present invention from another aspect is a production method wherein, in the above-mentioned adhering step, the above-mentioned member provides space with respect to the above-mentioned circuit board at the part that is not adhered to the above-mentioned electronic components and remains uniform in thickness at the part.  
           [0036]    Since air remaining within the thermal conductive member comes out of the space between the thermal conductive member and the surface of the circuit board absolutely, no void remains within the member and the electronic components and the thermal conductive member stick fast to each other evenly. The present invention has the effect of achieving a production method with high reliability of power module that efficiently takes heat occurring in the components having various heights, which are mounted to the circuit board.  
           [0037]    By applying the present invention to both sides of the circuit board, simultaneous lamination on both sides of the circuit board can be carried out with high reliability.  
           [0038]    A production method of a power module in accordance with the present invention from another aspect is a production method, in which the above-mentioned circuit board is a multi-layer board, further comprising a second adhering step of adhering an adhesive thin film to a second side of the above-mentioned circuit board before the above-mentioned adhering step, and a removing step of removing the above-mentioned thin film after the above-mentioned adhering step.  
           [0039]    The unhardened member (such as resin) can be prevented from flowing out through the through hole of the multi-layer board.  
           [0040]    A production method of a power module in accordance with the present invention from another aspect is a production method that further comprises a second mounting step of mounting a component to the above-mentioned second side of the above-mentioned circuit board after the above-mentioned removing step.  
           [0041]    A production method of a power module in accordance with the present invention from another aspect is a production method wherein the above-mentioned heat sink has a depressed portion in the side opposed to the above-mentioned circuit board, and in the above-mentioned laminating step, the above-mentioned unhardened member is filled in the above-mentioned depressed portion and a laminated body wherein the above-mentioned member and the above-mentioned heat sink are laminated is formed on the above-mentioned first side of the above-mentioned circuit board.  
           [0042]    The heating components can be embedded in the member, while preventing the member from flowing out.  
           [0043]    The novel features of the invention are set forth with particularity in the appended claims. The invention as to both structure and content, and other objects and features thereof will best be understood from the detailed description when considered in connection with the accompanying drawings. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0044]    [0044]FIG. 1 is a sectional view showing configuration of a power module in accordance with a first embodiment of the present invention.  
         [0045]    [0045]FIG. 2 is a sectional view showing configuration of a power module in accordance with a second embodiment of the present invention.  
         [0046]    [0046]FIG. 3 is a sectional view showing configuration of a power module in accordance with a third embodiment of the present invention.  
         [0047]    [0047]FIG. 4 is a sectional view by step showing a production method of a power module in accordance with a fourth embodiment of the present invention.  
         [0048]    [0048]FIG. 5 is a sectional view by step showing a production method of a power module in accordance with a fifth embodiment of the present invention.  
         [0049]    [0049]FIG. 6 is a sectional view by step showing a production method of a power module in accordance with a sixth embodiment of the present invention.  
         [0050]    [0050]FIG. 7 is a sectional view by step showing a production method of a power module in accordance with a seventh embodiment of the present invention.  
         [0051]    [0051]FIG. 8 is a sectional view showing configuration of a power module in accordance with an eighth embodiment of the present invention.  
         [0052]    [0052]FIG. 9 is a sectional view showing configuration of a power module in accordance with a ninth embodiment of the present invention.  
         [0053]    [0053]FIG. 10 is a sectional view showing configuration of a power module in accordance with a tenth embodiment of the present invention.  
         [0054]    [0054]FIG. 11 is a sectional view showing configuration of a power module in accordance with an eleventh embodiment of the present invention.  
         [0055]    [0055]FIG. 12 is a sectional view showing configuration of a power module in accordance with a twelfth embodiment of the present invention.  
         [0056]    [0056]FIG. 13 is a sectional view by step showing a production method of a power module in accordance with a thirteenth embodiment of the present invention.  
         [0057]    [0057]FIG. 14 is a sectional view by step showing a production method of a power module in accordance with a fourteenth embodiment of the present invention.  
         [0058]    [0058]FIG. 15 is a sectional view by step showing a production method of a power module in accordance with a fifteenth embodiment of the present invention.  
         [0059]    [0059]FIG. 16 is a sectional view by step showing a production method of a power module in accordance with a sixteenth embodiment of the present invention.  
         [0060]    [0060]FIG. 17 is a sectional view by step showing a production method of a power module in accordance with a seventeenth embodiment of the present invention.  
         [0061]    [0061]FIG. 18 is a sectional view by step showing a production method of a power module in accordance with an eighteenth embodiment of the present invention.  
         [0062]    [0062]FIG. 19 is a sectional view of a circuit board in accordance with a conventional example. 
     
    
       [0063]    Part or All of the drawings are drawn schematically for diagrammatic representation and it should be considered that they do not necessarily reflect relative size and position of components shown therein.  
       DETAILED DESCRIPTION OF THE INVENTION  
       [0064]    Embodiments that specifically show the best mode for conducting the present invention will be described below with reference to figures.  
         [0065]    &lt;&lt;First Embodiment&gt;&gt; 
         [0066]    A power module in accordance with a first embodiment will be described referring to FIG. 1.  
         [0067]    [0067]FIG. 1 is a sectional view showing configuration of the power module in accordance with the first embodiment of the present invention. In FIG. 1, a reference numeral  107  denotes the power module in accordance with the first embodiment of the present invention. The power module  107  comprises a multi-layer board  101  with a through hole  102 , electronic components requiring heat dissipation  103  (each having an arbitrary different height), a heat sink  104 , a high thermal conductive member  105  and electronic components  106 .  
         [0068]    The power module of this embodiment consists of three members including the multi-layer board  101 , the high thermal conductive member  105  and the heat sink  104 . The electronic components  103  and  106  are mounted to an insulating board  101   b  of the multi-layer board  101 . The electronic components requiring heat dissipation  103  such as an electric power conversion circuit with power semiconductor device and a control circuit for driving it are disposed on one side of the multi-layer board  101 . The high thermal conductive member  105  envelops (embeds) the electronic components requiring heat dissipation  103  therein. The heat sink  104  liberates heat generated from the electronic components requiring heat dissipation  103  to the outside.  
         [0069]    Heat occurring in the electronic components requiring heat dissipation  103  is diffused into the high thermal conductive member  105  and after that, the heat is transferred to the heat sink  104  and released from the heat sink  104  into the air.  
         [0070]    With the configuration of this embodiment, the heat sink  104  is firmly fixed to one side of the multi-layer board  101 , to which the electronic components requiring heat dissipation  103  are mounted, sandwiching the high thermal conductive member  105  therebetween. Heat generated from the electronic components requiring heat dissipation  103  can be thus transferred to the heat sink  104  efficiently.  
         [0071]    The multi-layer board  101  comprises the insulating board  101   b  and a conductive circuit pattern  101   a  formed on both sides of the insulating board  101   b . The conductive circuit pattern  101   a  formed on both sides of the insulating board  101   b  is electrically connected by the through hole  102 . The insulating board  101   b  is a, for example, glass-epoxy board in which glass fabric is impregnated with epoxy resin or ceramic board. The multi-layer board  101  of this embodiment is a double-sided board wherein the conductive circuit pattern  101   a  is formed on both sides of the insulating board  101   b  as shown in FIG. 1. The multi-layer board  101  may be a board having more layers or a one-sided board. Electrical connection of the insulating board  101   b  in the thickness direction is achieved by adopting all-layer IVH structure (interstitial via hole structure), not limited to the through hole.  
         [0072]    The electronic components requiring heat dissipation  103  are, for example, MOSFET, IGBT (insulated gate bipolar transistor), power semiconductor device such as shot key barrier diode, and passive device such as transistor and resistor.  
         [0073]    Preferably, the heat sink is made of aluminum or copper with high thermal conductivity. Copper, in particular, is excellent in thermal conductivity, thereby to obtain a good heat dissipation characteristic. Aluminum is cheap and lightweight, and has high thermal conductivity.  
         [0074]    The high thermal conductive member  105  is formed of insulating material that has unhardened thermosetting resin and inorganic filler as chief ingredients. Hence, heat transfer from the heating components  103  to the heat sink  104  can be achieved satisfactorily, resulting in good heat dissipation.  
         [0075]    Preferably, the thermosetting resin included in the high thermal conductive member  105  has at least one of epoxy resin, phenolic resin and cyanate resin, all of which have an excellent electrical insulating property even in high temperature. As understood by the fact that epoxy resin, in particular, is widely used as semiconductor sealing material in a circuit board and the like, it is excellent in electrical insulating property as well as chemical resistance and mechanical properties (strength).  
         [0076]    Preferably, the inorganic filler has at least one type of-powder selected from alumina, silica, magnesia, aluminum nitride and boron nitride. In the case where alumina or aluminum nitride is used as the inorganic filler, thermal conductivity of the high thermal conductive member  105  is further improved. The use of magnesia can increase thermal conductivity and thermal expansion coefficient of the high thermal conductive member  105 . And the use of silica (especially amorphous silica) enables the member  105  to save weight and decrease dielectric constant and thermal expansion coefficient. It is preferred that added amount of the inorganic filler makes up about 70 to 95 weight percent of the whole insulating sheet material (high thermal conductive member  105 ). In the circuit board requiring a good thermal conductivity, it is more preferred that the filled amount of the inorganic filler occupies as high as 88 weight percent or more of the whole member  105 . The insulating sheet material  105  is manufactured by technique including, but not limited to, doctor blade method or extrusion method.  
         [0077]    In the power module  107 , it is preferred that all components mounted to the side of the circuit board, which faces to the heat sink  104 , are short in height. By making all components short so as to suppress variation among components in vertical interval, thickness of the high thermal conductive member  105  disposed between the multi-layer board  101  and the heat sink  104  can be reduced. This prevents imposing excessive load on the heating components, and damaging the conductive circuit pattern  101   a  of the multi-layer board  101  to which the heating components  103  are mounted or generating crack in the conductive circuit pattern  101   a . Furthermore, since the thickness between the multi-layer board  101  and the heat sink  104  can be reduced, a lighter and slimmer power module can be realized.  
         [0078]    In the power module  107  of this embodiment, heat generated from the electronic components requiring heat dissipation  103  which are mounted to the multi-layer board  101  can be transferred to the heat sink  104  via the high thermal conductive member  105 . Strong bonding between the heat sink  104  and the high thermal conductive member  105  can reduce contact thermal resistance of the heat sink  104  and the high thermal conductive member  105 . The high thermal conductive member  105  can transfer heat generated from the power semiconductor to the heat sink  104  efficiently, thereby to suppress temperature rise of the components.  
         [0079]    In the power module  107  of this embodiment, since air in voids occurring within the high thermal conductive member  105  during production (as mentioned later) comes out of the through hole  102  and sides of the high thermal conductive member  105 , the electronic components requiring heat dissipation  103  and the high thermal conductive member  105  stick fast to each other evenly.  
         [0080]    Furthermore, by filling the high thermal conductive member  105  in part of the through hole  102  formed in the multi-layer board  101  so as to unify the multi-layer board  101  and the high thermal conductive member  105 , the high thermal conductive member  105  and the multi-layer board  101  are adhered to each other. Such a fixing method as to secure the heat sink  104  to the multi-layer board  101  by screws is unnecessary.  
         [0081]    &lt;&lt;Second Embodiment&gt;&gt; 
         [0082]    A power module in accordance with a second embodiment will be described referring to FIG. 2.  
         [0083]    [0083]FIG. 2 is a sectional view showing configuration of the power module in accordance with the second embodiment of the present invention. In FIG. 2, a reference numeral  207  denotes the power module in accordance with the second embodiment. The power module  207  of this embodiment comprises the multi-layer board  101  with the through hole  102 , the electronic components requiring heat dissipation  103  (each having an arbitrary different height), the heat sink  104 , the high thermal conductive member  105  and the electronic components  106 .  
         [0084]    The power module of the second embodiment is different from the power module of the first embodiment in that the high thermal conductive member  105  is formed so as to embed only a part of the electronic components  103  therein, thereby to provide space between the high thermal conductive member  105  and the surface of the multi-layer board  101 . The high thermal conductive member  105  remains substantially uniform in thickness at the part to which the electronic components requiring heat dissipation  103  are not mounted. Except for this, the power module of the second embodiment is the same as the power module of the first embodiment.  
         [0085]    In the case the electronic components  103  and  106  become miniaturized and their mounting becomes densified, small voids occurring within the high thermal conductive member  105  must be removed absolutely. In the power module  207  of this embodiment, since air in voids occurring within the high thermal conductive member  105  during production (as described later) comes out of the through hole  102  and space between the high thermal conductive member  105  and the surface of the multi-layer board  101  absolutely, the electronic components requiring heat dissipation  103  and the high thermal conductive member  105  stick fast to each other certainly and evenly.  
         [0086]    With the configuration as shown in FIG. 2, in the power module of the second embodiment, heat can be efficiently transferred from the surfaces of the electronic components requiring heat dissipation  103  to the heat sink  104  via the high thermal conductive member  105 . Since the power module of the second embodiment has less amount of the high thermal conductive member  105  than that of the first embodiment, cost reduction and weight saving can be achieved.  
         [0087]    In the power module  207  of this embodiment, the high thermal conductive member  105  does not flow from one side of the multi-layer board  101  to other side thereof through the through hole  102  during production (as described later).  
         [0088]    The apparatus that builds the power module  207  of this embodiment therein may be configured so that air is fed into the space between the high thermal conductive member  105  and the surface of the multi-layer board  101  along the high thermal conductive member  105  from a fan (not shown), thereby to liberate heat released from the electronic components requiring heat dissipation  103 .  
         [0089]    &lt;&lt;Third Embodiment&gt;&gt; 
         [0090]    A power module in accordance with a third embodiment will be described referring to FIG. 3.  
         [0091]    [0091]FIG. 3 is a sectional view showing configuration of the power module in accordance with the third embodiment of the present invention. In FIG. 3, a reference numeral  307  denotes the power module in accordance with this embodiment. The power module  307  of the third embodiment comprises the multi-layer board  101  with the through hole  102 , the electronic components requiring heat dissipation  103  (each having an arbitrary different height), the heat sink  104 , the high thermal conductive member  105  and the electronic components  106 .  
         [0092]    The power module of this embodiment is different from that of the first embodiment in that the heat sink  104  is of recessed shape, and the high thermal conductive member  105  that envelops (embeds) the electronic component requiring heat dissipation  103  therein is enclosed with the heat sink  104 . With such configuration, heat generated from the electronic components requiring heat dissipation  103  is transferred to the heat sink  104  efficiently. By filling the unhardened member  105  in the depressed portion of the heat sink  104  during production (as described later), the member  105  can be prevented from flowing out.  
         [0093]    In the case where the through hole  102  is formed in the multi-layer board  101 , by partially filling the unhardened member  105  in the through hole  102  formed in the multi-layer board  101  and unifying them, the high thermal conductive member  105  and the multi-layer board  101  can be adhered to each other and therefore such a fixing method as to secure the heat sink  104  to the multi-layer board  101  by screws becomes unnecessary.  
         [0094]    &lt;&lt;Fourth Embodiment&gt;&gt; 
         [0095]    A production method of the power module  107  of the first embodiment shown in FIG. 1 will be described referring to FIG. 4. FIG. 4 is a process chart showing a production method of the power module  107  shown in FIG. 1 in accordance with a fourth embodiment.  
         [0096]    In a first step shown in FIG. 4( a ), electronic components including the electronic components requiring heat dissipation  103  are mounted to one side of the multi-layer board  101 . The electronic components requiring heat dissipation  103  are, for example, MOSFET, IGBT, power semiconductor device such as shot key barrier diode, or passive device such as transistor and resistor. An adhesive organic film  108  is adhered to the other side of the multi-layer board  101  (the side to which the electronic components  103  are not mounted). This prevents the unhardened high thermal conductive member  105  from passing through the through hole and flowing out from the other side of the multi-layer board  101  when the high thermal conductive member  105  is disposed in a subsequent step.  
         [0097]    Next, in a second step shown in FIG. 4( b ), the sheet-like unhardened high thermal conductive member  105  and the heat sink  104  of uniform thickness are disposed on the side of the multi-layer board  101 , to which the electronic components requiring heat dissipation  103  are mounted. In this step, the high thermal conductive member  105  is separated from the heat sink  104 , and the heat sink  104 , the sheet-like unhardened high thermal conductive member  105  and the multi-layer board  101  are vertically arranged in this order. Material for the high thermal conductive member  105  has been described in detail in the first embodiment.  
         [0098]    As described in the first embodiment, the heat sink  104  is, for example, an aluminum or copper plate. Preferably, the heat sink  104  is subjected to surface roughening. Surface roughening methods includes the method of spraying aluminum oxide powder and compressed air on the surface of the heat sink. Roughening the surface of the heat sink  104  can increase adhesive strength between the high thermal conductive member  105  and the heat sink  104 . The reason for that is because surface area of the heat sink  104  is increased by means of surface roughening and adhesive strength is improved due to the anchor effect. This allows reducing contact thermal resistance of the heat sink  104  and the high thermal conductive member  105  so that heat generated from the power semiconductor can be transferred to the heat sink  104  via the high thermal conductive member  105  efficiently.  
         [0099]    Next, in a third step shown in FIG. 4( c ), the multi-layer board  101 , the high thermal conductive member  105  and the heat sink  104  are laminated to form a laminated body  401 . After that, the laminated body  401  is pressurized in the direction of surface (vertical direction in FIG. 4) and heated, thereby that the high thermal conductive member  105  becomes hardened, and the high thermal conductive member  105  and the heat sink  104  are adhered to each other. At this time, the electronic components requiring heat dissipation  103  mounted to the multi-layer board  101  are made to be embedded in the high thermal conductive member  105 .  
         [0100]    Finally, in a fourth step shown in FIG. 4( d ), the organic film  108  is removed and the electronic component  106  is mounted on the side of the multi-layer board  101  to which the organic film  108  is adhered to complete the power module  107 .  
         [0101]    Since the laminated body  401  is pressurized in the direction of surface and heated in the third step of the fourth embodiment (FIG. 4( c )), air in voids occurring within the unhardened member  105  comes out of the through hole  102  and the sides of the member  105  (direction orthogonal to the pressurizing direction), thereby to bring the electronic components  103  into coherent with the member  105  with reliability.  
         [0102]    &lt;&lt;Fifth Embodiment&gt;&gt; 
         [0103]    A production method of the power module  107  of the first embodiment shown in FIG. 1 will be described referring to FIG. 5. FIG. 5 is a step chart showing a production method of the power module  107  shown in FIG. 1 in accordance with a fourth embodiment.  
         [0104]    In a first step shown in FIG. 5( a ), electronic components including the electronic components requiring heat dissipation  103  are mounted to one side of the multi-layer board  101 . The electronic components requiring heat dissipation  103  are, for example, MOSFET, IGBT, power semiconductor device such as shot key barrier diode, or passive device such as transistor and resistor. The adhesive organic film  108  is adhered to other side of the multi-layer board  101  (the side to which the electronic components  103  are not mounted).  
         [0105]    Next, in a second step shown in FIG. 5( b ), the paste-like unhardened high thermal conductive member  105  formed of at least inorganic filler and thermosetting resin is printed to the heat sink  104  of uniform thickness so as to have a certain thickness.  
         [0106]    The high thermal conductive member  105  is made to be paste-like by mixing the organic filler and the liquid thermosetting resin with a triple roller. When this high thermal conductive member  105  has an appropriate viscosity to be applied over the heat sink  104 , it can be used a paste as it is. When the high thermal conductive member  105  has a higher viscosity than desired, it is possible to adjust the viscosity to an appropriate value by mixing a solvent capable of being evaporated a later step. A solvent having a boiling point lower than a cure temperature of the thermosetting resin is used as the solvent. Printing methods of printing the high thermal conductive member  105  includes metal mask printing method, screen-printing method and so on.  
         [0107]    Next, in a third step shown in FIG. 5( c ), the heat sink  104  on which the high thermal conductive member  105  is formed and the multi-layer board  101  to which the electronic component requiring heat dissipation  103  are mounted are laminated so as to sandwich the high thermal conductive member  105  and the electronic component requiring heat dissipation  103  therebetween. After a laminated body  501  is formed so as to laminate the heat sink  104 , the high thermal conductive member  105  and the multi-layer board  101  in this order, the laminated body  501  is pressurized in the direction of surface (vertical direction in FIG. 5) and heated, thereby that the high thermal conductive member  105  becomes hardened, and the electronic components requiring heat dissipation  103 , the high thermal conductive member  105  and the heat sink  104  are adhered to each other.  
         [0108]    Finally, in a fourth step shown in FIG. 5( d ), the organic film  108  is removed and the electronic component  106  is mounted on the side of the multi-layer board  101 , to which the organic film  108  is adhered, to complete the power module  107 .  
         [0109]    Since the laminated body  501  is pressurized in the direction of surface and heated in the third step of the fifth embodiment (FIG. 5( c )), air in voids occurring within the unhardened member  105  comes out of the through hole  102  and the sides of the member  105  (the direction orthogonal to the pressurizing direction), thereby to bring the electronic components  103  into coherent with the member  105  with reliability.  
         [0110]    &lt;&lt;Sixth Embodiment&gt;&gt; 
         [0111]    A production method of the power module  207  of the second embodiment shown in FIG. 2 will be described referring to FIG. 6. FIG. 6 is a process chart showing a production method of the power module  207  shown in FIG. 2 in accordance with a sixth embodiment.  
         [0112]    In a first step shown in FIG. 6( a ), electronic components including the electronic components requiring heat dissipation  103  are mounted to one side of the multi-layer board  101 . The electronic components requiring heat dissipation  103  are, for example, MOSFET, IGBT, power semiconductor device such as shot key barrier diode, or passive device such as transistor and resistor. The adhesive organic film  108  needs not be adhered in the sixth embodiment.  
         [0113]    Next, in a second step shown in FIG. 6( b ), the paste-like unhardened high thermal conductive member  105  formed of at least inorganic filler and thermosetting resin is printed to the heat sink  104  of uniform thickness so as to have a certain thickness. The production method of the unhardened high thermal conductive member  105  has been described in detail in the fifth embodiment.  
         [0114]    Next, in a third step shown in FIG. 6( c ), the heat sink  104  on which the high thermal conductive member  105  is formed and the multi-layer board  101  to which the electronic components requiring heat dissipation  103  are mounted are laminated so as to sandwich the high thermal conductive member  105  and the electronic components requiring heat dissipation  103  therebetween. After a laminated body  601  is formed so as to laminate the heat sink  104 , the high thermal conductive member  105  and the multi-layer board  101  in this order, the laminated body  601  is pressurized in the direction of surface (vertical direction in FIG. 6) and heated, thereby that the high thermal conductive member  105  becomes hardened, and the electronic components requiring heat dissipation  103 , the high thermal conductive member  105  and the heat sink  104  are adhered to each other.  
         [0115]    The laminated body  601  of this embodiment is formed so that the high thermal conductive member  105  coats the surfaces of the electronic components mounted to the multi-layer board  101  (or embeds part of the electronic components therein), thereby generating space between the high thermal conductive member  105  and the multi-layer board  101 . The production method of the present embodiment is different from that of the fifth embodiment wherein the whole of the electronic components is embedded in the high thermal conductive member  105  in this respect.  
         [0116]    Finally, in a fourth step shown in FIG. 6( d ), the electronic component  106  is mounted on the side of the multi-layer board  101 , to which the electronic components  103  are not mounted, to complete the power module  207 .  
         [0117]    Since air in voids occurring within the unhardened member  105  comes out of the through hole  102  and the space between the high thermal conductive member  105  and the multi-layer board  101  when the laminated body  501  is pressurized in the direction of surface and heated in the third step of the sixth embodiment (FIG. 6( c )), the electronic components  103  can be brought into coherent with the member  105  with reliability.  
         [0118]    In the sixth embodiment, the paste-like unhardened high thermal conductive member  105  is printed to the heat sink  104  of uniform thickness so as to have a certain thickness in the second step shown in FIG. 6( b ). Needless to say, it is also possible that the sheet-like unhardened high thermal conductive member  105  and the sheet-like heat sink  104  are disposed on the side of the multi-layer board  101 , to which the electronic components requiring heat dissipation are mounted (FIG. 4( b )), and the laminated body (with a predetermined space between the high thermal conductive member  105  and the multi-layer board  101  provided) is pressurized and heated (FIG. 4( c )).  
         [0119]    &lt;&lt;Seventh Embodiment&gt;&gt; 
         [0120]    A production method of the power module  307  of the third embodiment shown in FIG. 3 will be described referring to FIG. 7. FIG. 7 is a process chart showing the production method of the power module  307  shown in FIG. 3 in accordance with a seventh embodiment.  
         [0121]    In a first step shown in FIG. 7( a ), electronic components including the electronic components requiring heat dissipation  103  are mounted to one side of the multi-layer board  101 . The electronic components requiring heat dissipation  103  are, for example, MOSFET, IGBT, power semiconductor device such as shot key barrier diode, or passive device such as transistor and resistor. The adhesive organic film  108  is adhered to other side of the multi-layer board  101  (the side to which the electronic components  103  are not mounted).  
         [0122]    Next, in a second step shown in FIG. 7( b ), the heat sink  104  is formed so as to be recessed shape. The paste-like unhardened high thermal conductive member  105  formed of at least inorganic filler and thermosetting resin is produced. The production method of the unhardened high thermal conductive member  105  has been described in detail in the fifth embodiment. The paste-like unhardened high thermal conductive member  105  is filled in a depressed portion  702  of the heat sink  104 .  
         [0123]    Alternatively, it is also possible that the sheet-like unhardened high thermal conductive member  105  is cut to be recessed shape and the member thus cut is filled in the depressed portion  702  (a similar method as in FIG. 4 (the fourth embodiment)).  
         [0124]    Next, in a third step shown in FIG. 7( c ), the heat sink  104 , the high thermal conductive member  105  and the multi-layer board  101  are laminated in this order so as to set the side of the multi-layer board  101  to which the electronic components requiring heat dissipation  103  are mounted as opposed to the high thermal conductive member  105  filled in the depressed portion  702  of the heat sink  104 .  
         [0125]    Next, in a fourth step shown in FIG. 7( d ), the high thermal conductive member  105  is hardened by use of a heating oven, thereby that the whole of the electronic components requiring heat dissipation  103  is coated with the high thermal conductive member  105  (embedded in the high thermal conductive member  105 ) to form a laminated body  701 .  
         [0126]    Finally, in a fifth step shown in FIG. 7( e ), the organic film  108  is removed and the electronic component  106  is mounted on the side of the multi-layer board  101 , to which the organic film  108  is adhered, to complete the power module  307 .  
         [0127]    As a substitute for the fourth step shown in FIG. 7( d ), it is also possible, of course, that part of the electronic components requiring heat dissipation  103  is coated with the high thermal conductive member  105  (embedded in the high thermal conductive member  105 ) to form the laminated body  701  with space between the high thermal conductive member  105  and the multi-layer board  101  provided. A power module  807  of an eighth embodiment (as described later) can be produced by use of this production method.  
         [0128]    &lt;&lt;Eighth Embodiment&gt;&gt; 
         [0129]    A power module in accordance with an eighth embodiment will be described referring to FIG. 8.  
         [0130]    [0130]FIG. 8 is a sectional view showing configuration of the power module in accordance with the eighth embodiment of the present invention. The power module  807  of this embodiment comprises the multi-layer board  101  with the through hole  102 , the electronic components requiring heat dissipation  103  (each having an arbitrary different height), the heat sink  104 , the high thermal conductive member  105  and the electronic components  106 .  
         [0131]    The power module of the eighth embodiment is different from that of the third embodiment in that the high thermal conductive member  105  is formed so as to embed only a part of the surfaces of the electronic components  103  therein, thereby to provide space between the high thermal conductive member  105  and the multi-layer board  101 . The high thermal conductive member  105  remains uniform in thickness at the part to which the electronic components requiring heat dissipation  103  are not mounted. Except for this, the power module of the eighth embodiment is the same as that of the third embodiment.  
         [0132]    In the case where the electronic components  103  and  106  become miniaturized, small voids occurring within the high thermal conductive member  105  must be removed absolutely. In the power module  807  of this embodiment, since air in voids occurring within the high thermal conductive member  105  during production (as described later) comes out of the through hole  102  and space between the high thermal conductive member  105  and the surface of the multi-layer board  101  with reliability, the electronic components requiring heat dissipation  103  and the high thermal conductive member  105  stick fast to each other evenly.  
         [0133]    In the power module  807  of this embodiment, the heat sink  104  is formed to recessed shape and the high thermal conductive member  105  that envelops (embeds) the electronic components requiring heat dissipation  103  therein is enclosed with the heat sink  104 . The high thermal conductive member  105  remains substantially uniform in thickness at the part to which the electronic components requiring heat dissipation  103  are not mounted. With such configuration, heat generated from the electronic components requiring heat dissipation  103  can be transferred to the heat sink  104  efficiently. By filling the unhardened member  105  in the depressed portion of the heat sink  104  during production (as described later), the member  105  is prevented from flowing out. Since the power module of this embodiment has less amount of the high thermal conductive member  105  than the power module of the third embodiment, cost reduction and weight saving can be achieved.  
         [0134]    In the power module  807  of this embodiment, the high thermal conductive member  105  does not flow from one side of the multi-layer board  101  to other side thereof through the through hole  102  during production (as described later).  
         [0135]    The apparatus that builds the power module  807  therein may be configured so that air is fed into the space between the high thermal conductive member  105  and the surface of the multi-layer board  101  along the high thermal conductive member  105  from a fan (not shown), thereby to liberate heat released from the electronic components requiring heat dissipation  103 .  
         [0136]    &lt;&lt;Ninth Embodiment&gt;&gt; 
         [0137]    A power module in accordance with a ninth embodiment will be described referring to FIG. 9.  
         [0138]    [0138]FIG. 9 is a sectional view showing configuration of the power module in accordance with the ninth embodiment of the present invention. In FIG. 9, a reference numeral  907  denotes the power module of the ninth embodiment. The power module  907  of this embodiment comprises the multi-layer board  101  with the through hole  102 , the electronic components requiring heat dissipation  103  and  109  (each having an arbitrary different height), the heat sink  104 , the high thermal conductive member  105  and the electronic components  106 .  
         [0139]    Similar to the electronic component  103 , an electronic component requiring heat dissipation  109  is a, for example, MOSFET, IGBT, power semiconductor device such as shot key barrier diode, or passive device such as transistor and resistor.  
         [0140]    The power module  907  of the ninth embodiment is different from that of the first embodiment in that, the electronic components requiring heat dissipation  103  and  109  are mounted and the high thermal conductive member  105  and the heat sink  104  are formed on the both sides of the multi-layer board  101 . Except for this, the power module  907  of the ninth embodiment is the same as that of the first embodiment.  
         [0141]    The power module of this embodiment consists of five layers of the heat sink  104 , the high thermal conductive member  105 , the multi-layer board  101 , the high thermal conductive member  105  and the heat sink  104 , which are vertically arranged in this order. The electronic components  103 ,  106  and  109  are mounted to the insulating board  101   b  of the multi-layer board  101 . The electronic components requiring heat dissipation  103  and  109 , respectively, are disposed on both sides of the multi-layer board  101 . The high thermal conductive member  105  envelops (embeds) the electronic components requiring heat dissipation  103  and  109  therein. The heat sink  104  releases heat generated from the electronic components requiring heat dissipation  103  and  109  to the outside.  
         [0142]    After heat occurring from the electronic components requiring heat dissipation  103  and  109  is diffused into the high thermal conductive member  105 , it is transferred to the heat sink  104  and released from the heat sink  104  into the air.  
         [0143]    In the power module of this embodiment, heat generated from the electronic components requiring heat dissipation  103  and  109  mounted to both sides of the multi-layer board  101  can be efficiently transferred to the heat sink  104  via the high thermal conductive member  105 . By adhering the high thermal conductive member  105  to the heat sink strongly, it is possible to reduce contact thermal resistance of the heat sink  104  and the high thermal conductive member  105 . The high thermal conductive member  105  is capable of transferring heat from the power semiconductor to the heat sink  104  efficiently. This enables suppressing temperature rise of components at low level.  
         [0144]    &lt;&lt;Tenth Embodiment&gt;&gt; 
         [0145]    A power module in accordance with a tenth embodiment will be described referring to FIG. 10.  
         [0146]    [0146]FIG. 10 is a sectional view showing configuration of the power module in accordance with the tenth embodiment of the present invention. In FIG. 10, a reference numeral  1007  denotes the power module of the tenth embodiment. The power module  1007  of this embodiment comprises the multi-layer board  101  with the through hole  102 , the electronic components requiring heat dissipation  103  and  109  (each having an arbitrary different height), the heat sink  104 , the high thermal conductive member  105  and the electronic components  106 .  
         [0147]    The power module of the tenth embodiment is different from that of the ninth embodiment in that the high thermal conductive member  105  is formed so as to embed only a part of the surfaces of the electronic components  103  and  109  therein, thereby to provide space between the high thermal conductive member  105  and the multi-layer board  101 . The high thermal conductive member  105  remains substantially uniform in thickness at the part to which the electronic components requiring heat dissipation  103  and  109  are not mounted. Except for this, the power module of the tenth embodiment is the same as that of the ninth embodiment.  
         [0148]    In the case where the through hole  102 , and the electronic components  103  and  109  become miniaturized, small voids occurring within the high thermal conductive member  105  must be removed absolutely. In the power module  1007  of this embodiment, since air in voids occurring within the high thermal conductive member  105  during production (as described later) comes out of the through hole  102  and space between the high thermal conductive member  105  and the surface of the multi-layer board  101  with reliability, the electronic components requiring heat dissipation  103  and  109 , and the high thermal conductive member  105  stick fast to each other evenly.  
         [0149]    With the configuration shown in FIG. 10, the power module of the tenth embodiment can transfer heat from the surfaces of the electronic components requiring heat dissipation  103  and  109  to the heat sink  104  via the high thermal conductive member  105  efficiently. Furthermore, since the power module of this embodiment has less amount of the high thermal conductive member  105  than that of the ninth embodiment, cost reduction and weight saving can be realized.  
         [0150]    In the power module  1007  of this embodiment, the high thermal conductive member  105  does not flow from one side of the multi-layer board  101  to other side thereof through the through hole  102  during production (as described later).  
         [0151]    The apparatus that builds the power module  1007  therein may be configured so that air is fed into the space between the high thermal conductive member  105  and the surface of the multi-layer board  101  along the high thermal conductive member  105  from a fan (not shown), thereby to liberate heat released from the electronic components requiring heat dissipation  103  and  109 .  
         [0152]    &lt;&lt;Eleventh Embodiment&gt;&gt; 
         [0153]    A power module in accordance with an eleventh embodiment will be described referring to FIG. 11.  
         [0154]    [0154]FIG. 11 is a sectional view showing configuration of the power module in accordance with the eleventh embodiment of the present invention. In FIG. 11, a reference numeral  1107  denotes the power module of this embodiment. The power module  1107  of the eleventh embodiment comprises the multi-layer board  101  with the through hole  102 , the electronic components requiring heat dissipation  103  and  109  (each having an arbitrary different height), the heat sink  104 , the high thermal conductive member  105  and the electronic components  106 .  
         [0155]    The power module of this embodiment is different from that of tenth embodiment in that the heat sink  104  is formed to recessed shape and the high thermal conductive member  105  that envelops (embeds) the electronic components requiring heat dissipation  103  and  109  therein is enclosed with the heat sink  104 . With such configuration, heat generated from the electronic components requiring heat dissipation  103  can be transferred to the heat sink  104  efficiently. By filling the unhardened member  105  in the depressed portion of the heat sink  104  during production (as described later), the member  105  can be prevented from flowing out.  
         [0156]    &lt;&lt;Twelfth Embodiment&gt;&gt; 
         [0157]    A power module in accordance with a twelfth embodiment will be described referring to FIG. 12.  
         [0158]    [0158]FIG. 12 is a sectional view showing configuration of the power module in accordance with the twelfth embodiment of the present invention. In FIG. 12, a reference numeral  1207  denotes the power module of this embodiment. The power module  1207  of the twelfth embodiment comprises the multi-layer board  101  with the through hole  102 , the electronic components requiring heat dissipation  103  and  109  (each having an arbitrary different height), the heat sink  104 , the high thermal conductive member  105  and the electronic components  106 .  
         [0159]    The power module of the twelfth embodiment is different from that of the eleventh embodiment in that the high thermal conductive member  105  is formed so as to embed only a part of the surfaces of the electronic components  103  and  109  therein, thereby to provide space between the high thermal conductive member  105  and the multi-layer board  101 . The high thermal conductive member  105  remains substantially uniform in thickness at the part to which the electronic components requiring heat dissipation  103  and  109  are not mounted. Except for this, the power module of the twelfth embodiment is the same as that of the eleventh embodiment.  
         [0160]    In the case where the electronic components  103  and  109  become miniaturized, small voids occurring within the high thermal conductive member  105  must be removed absolutely. In the power module  1207  of this embodiment, since air in voids occurring within the high thermal conductive member  105  during production (as described later) comes out of the through hole  102  and space between the high thermal conductive member  105  and the surface of the multi-layer board  101  with reliability, the high thermal conductive member  105  and the electronic components requiring heat dissipation  103  and  109 , respectively, stick fast to each other evenly.  
         [0161]    In the power module  1207  of this embodiment, the heat sink  104  is formed to recessed shape and the high thermal conductive member  105  that envelops (embeds) the electronic components requiring heat dissipation  103  and  109  therein is enclosed with the heat sink  104 . With such configuration, heat generated from the electronic components requiring heat dissipation  103  and  109  can be transferred to the heat sink  104  efficiently. By filling the unhardened member  105  in the depressed portion of the heat sink  104  during production (as described later), the member  105  can be prevented from flowing out. Since the power module of this embodiment has less amount of the high thermal conductive member  105  than that of the third embodiment, cost reduction and weight saving can be achieved.  
         [0162]    The apparatus that builds the power module  1207  therein may be configured so that air is fed into the space between the high thermal conductive member  105  and the surface of the multi-layer board  101  along the high thermal conductive member  105  from a fan (not shown), thereby to liberate heat released from the electronic components requiring heat dissipation  103 .  
         [0163]    &lt;&lt;Thirteenth Embodiment&gt;&gt; 
         [0164]    A production method of the power module  907  shown in FIG. 9 will be described referring to FIG. 13. FIG. 13 is a process chart showing a production method of the power module  907  shown in FIG. 9 in accordance with a thirteenth embodiment.  
         [0165]    In a first step shown in FIG. 13( a ), the electronic components requiring heat dissipation  103  and the electronic component  106  are mounted to one side of the multi-layer board  101 , and the electronic component requiring heat dissipation  109  is mounted to other side thereof.  
         [0166]    Next, in a second step shown in FIG. 13( b ), the paste-like unhardened high thermal conductive member  105  formed of at least inorganic filler and thermosetting resin is printed to the heat sink  104  of uniform thickness so as to have a certain thickness. The production method of the unhardened high thermal conductive member  105  has been described in detail in the fifth embodiment.  
         [0167]    Next, in a third step shown in FIG. 13( c ), a laminated body wherein the multi-layer board  101  and the heat sink  104  are laminated so that the high thermal conductive member  105  printed to the heat sink  104  faces to each side of the multi-layer board  101  is formed at both sides simultaneously or one by one. At this time, the electronic components requiring heat dissipation  103  and  109  are made to be embedded in the high thermal conductive member  105 . The laminated body is pressurized in the direction of surface (vertical direction in FIG. 13) and heated, thereby that the high thermal conductive member  105  becomes hardened, and the high thermal conductive member  105 , and the electronic components requiring heat dissipation  103  and  109 , respectively, are adhered to each other to complete the power module  907 . Impletion of the third step under reduced pressure can further prevent voids from occurring.  
         [0168]    &lt;&lt;Fourteenth Embodiment&gt;&gt; 
         [0169]    A production method of the power module  1007  shown in FIG. 10 will be described referring to FIG. 14. FIG. 14 is a step chart showing a production method of the power module  1007  shown in FIG. 10 in accordance with a fourteenth embodiment.  
         [0170]    In a first step shown in FIG. 14( a ), the electronic components requiring heat dissipation  103  and the electronic component  106  are mounted to one side of the multi-layer board  101 . The paste-like unhardened high thermal conductive member  105  formed of at least inorganic filler and thermosetting resin is printed to the heat sink  104  of uniform thickness so as to have a certain thickness. The production method of the unhardened high thermal conductive member  105  has been described in detail in the fifth embodiment.  
         [0171]    Next, in a second step shown in FIG. 14( b ), the heat sink  104  on which the high thermal conductive member  105  is formed and the multi-layer board  101  to which the electronic component requiring heat dissipation  103  are mounted are laminated so as to sandwich the high thermal conductive member  105  and the electronic component requiring heat dissipation  103  therebetween. After a laminated body  1401  is formed so as to laminate the heat sink  104 , the high thermal conductive member  105  and the multi-layer board  101  in this order, the laminated body  1401  is pressurized in the direction of surface (vertical direction in FIG. 14) and heated, thereby that the high thermal conductive member  105  becomes hardened, and the electronic components requiring heat dissipation  103 , the high thermal conductive member  105  and the heat sink  104  are adhered to each other. The laminated body  1401  is formed so that the high thermal conductive member  105  coats the surfaces of the electronic components mounted to the multi-layer board  101  (or embeds part of the electronic components therein), thereby to provide space the high thermal conductive member  105  and the multi-layer board  101 . The high thermal conductive member  105  remains substantially uniform in thickness at the part to which the electronic components requiring heat dissipation  103  are not mounted.  
         [0172]    Next, in a third step shown in FIG. 14( c ), the electronic component requiring heat dissipation  109  is mounted to the side of the multi-layer board  101 , to which the electronic components  103  and  106  are not mounted in the first step. The paste-like unhardened high thermal conductive member  105  formed of at least inorganic filler and thermosetting resin is printed to the heat sink  104  of uniform thickness so as to have a certain thickness.  
         [0173]    Finally, in a fourth step shown in FIG. 14( d ), the heat sink  104  on which the high thermal conductive member  105  is formed and the multi-layer board  101  to which the electronic component requiring heat dissipation  109  is mounted are laminated so as to sandwich the high thermal conductive member  105  and the electronic component requiring heat dissipation  109  therebetween. After that, the laminated body is pressurized in the direction of surface (vertical direction in FIG. 14) and heated, thereby that the high thermal conductive member  105  becomes hardened, and the electronic components requiring heat dissipation  109 , the high thermal conductive member  105  and the heat sink  104  are adhered to each other to complete the power module  1007 .  
         [0174]    The power module  1007  is formed so that the high thermal conductive member  105  coats the surfaces of the electronic components mounted to the multi-layer board  101  (or embeds part of the electronic components therein), thereby to provide space the high thermal conductive member  105  and the multi-layer board  101 .  
         [0175]    Since air in voids occurring within the unhardened high thermal conductive member  105  comes out of the through hole  102  and space between the high thermal conductive member  105  and the multi-layer board  101  when the laminated body is pressurized in the direction of surface and heated in the second step (FIG. 14( b )) and the fourth step (FIG. 14( d )), and the electronic components requiring heat dissipation  103  and  109 , respectively, can be stuck fast to the high thermal conductive member  105  with reliability.  
         [0176]    &lt;&lt;Fifteenth Embodiment&gt;&gt; 
         [0177]    Another production method of the power module  1007  shown in FIG. 10 will be described referring to FIG. 15. FIG. 15 is a process chart showing a production method of the power module  1007  shown in FIG. 10 in accordance with a fifteenth embodiment.  
         [0178]    Since a first step (FIG. 15( a )) and a second step (FIG. 15( b )) of the fifteenth embodiment are the same as the first step (FIG. 13( a )) and the second step (FIG. 13( b )) of the thirteenth embodiment, explanations thereof are omitted.  
         [0179]    Next, in a third step shown in FIG. 15( c ), a laminated body wherein the multi-layer board  101  and the heat sink  104  are laminated so that the high thermal conductive member  105  formed on the heat sink  104  faces to each side of the multi-layer board  101  is formed on each side of the multi-layer board  101  simultaneously. The laminated body is formed so that the high thermal conductive member  105  coats the surfaces of the electronic components (or embeds part of the electronic components therein), thereby to provide space between the high thermal conductive member  105  and the multi-layer board  101 . The high thermal conductive member  105  remains substantially uniform in thickness at the part to which the electronic components requiring heat dissipation  103  and  109  are not mounted. Next, the laminated body is pressurized in the direction of surface (vertical direction in FIG. 15) and heated, thereby that the high thermal conductive member  105  becomes hardened, and the high thermal conductive member  105 , and the electronic components requiring heat dissipation  103  and  109 , respectively, are adhered to each other to complete the power module  1007 .  
         [0180]    In the production method of the fifteenth embodiment, the heat sink  104  and the high thermal conductive member  105  are adhered to both sides of the multi-layer board  101  simultaneously. As the production method of the fifteenth embodiment has less number of steps than the production method of the thirteenth embodiment, the power module  1007  of the tenth embodiment can be produced at a lower cost.  
         [0181]    &lt;&lt;Sixteenth Embodiment&gt;&gt; 
         [0182]    A production method of the power module  1107  shown in FIG. 11 will be described referring to FIG. 16. FIG. 16 is a process chart showing a production method of the power module  1107  shown in FIG. 11 in accordance with a sixteenth embodiment.  
         [0183]    In a first step shown in FIG. 16( a ), the electronic components requiring heat dissipation  103  and the electronic component  106  are mounted to one side of the multi-layer board  101 , and the electronic component requiring heat dissipation  109  is mounted to other side thereof.  
         [0184]    Next, in a second step shown in FIG. 16( b ), the heat sink  104  is formed so as to be recessed shape. The paste-like unhardened high thermal conductive member  105  formed of at least inorganic filler and thermosetting resin is produced. The production method of the unhardened high thermal conductive member  105  has been described in detail in the fifth embodiment. The paste-like unhardened high thermal conductive member  105  is filled in a depressed portion of the heat sink  104 .  
         [0185]    Alternatively, it is also possible that the sheet-like unhardened high thermal conductive member  105  is cut to be recessed shape and the member thus cut is filled in the depressed portion  702  (a similar method as in FIG. 4 (the fourth embodiment)).  
         [0186]    Next, the multi-layer board  101  and a heat sink  104  are laminated so as to set each side of the multi-layer board  101  as opposed to the high thermal conductive member  105  filled in the depressed portion of the heat sink  104 .  
         [0187]    Finally, in a third step shown in FIG. 16( c ), the high thermal conductive member  105  is hardened by use of a heating oven at both sides simultaneously (or one by one), thereby that the whole of the electronic components requiring heat dissipation  103  mounted to the multi-layer board  101  is coated with the high thermal conductive member  105  (embedded in the high thermal conductive member  105 ) to form a laminated body  1107 .  
         [0188]    All steps in the production method of the sixteenth embodiment are carried out in a vacuum chamber. Hence, no void remains within the high thermal conductive member  105  and therefore, the electronic components  103  and  109  can be brought into coherent with the member  105  with reliability.  
         [0189]    &lt;&lt;Seventeenth Embodiment&gt;&gt; 
         [0190]    A production method of the power module  1207  shown in FIG. 12 will be described referring to FIG. 17. FIG. 17 is a process chart showing a production method of the power module  1207  shown in FIG. 12 in accordance with a seventeenth embodiment.  
         [0191]    In a first step shown in FIG. 17( a ), the electronic components requiring heat dissipation  103  and the electronic component  106  are mounted to one side of the multi-layer board  101 .  
         [0192]    Next, the heat sink  104  is formed so as to be recessed shape. The paste-like unhardened high thermal conductive member  105  formed of at least inorganic filler and thermosetting resin is produced. The production method of the unhardened high thermal conductive member  105  has been described in detail in the fifth embodiment. The paste-like unhardened high thermal conductive member  105  is filled in a depressed portion of the heat sink  104 .  
         [0193]    Alternatively, it is also possible that the sheet-like unhardened high thermal conductive member  105  is cut to be recessed shape and the member thus cut is filled in the depressed portion (a similar method as in FIG. 4 (the fourth embodiment)).  
         [0194]    Next, in a second step shown in FIG. 17( b ), the multi-layer board  101  and a heat sink  104  are laminated so that the side of the multi-layer board  101  to which the electronic components  103  are mounted is set as opposed to the high thermal conductive member  105  filled in the depressed portion of the heat sink  104 . The high thermal conductive member  105  remains substantially uniform in thickness at the part to which the electronic components requiring heat dissipation  103  are not mounted. The high thermal conductive member  105  is hardened by use of a heating oven, thereby that the surfaces of the electronic components requiring heat dissipation  103  mounted to the multi-layer board  101  are coated with the high thermal conductive member  105  (embedded in the high thermal conductive member  105 ).  
         [0195]    In a third step shown in FIG. 17( c ), the electronic component requiring heat dissipation  109  is mounted to the side of the multi-layer board  101  to which the electronic components are mounted in the first step.  
         [0196]    Next, the heat sink  104  is formed so as to be recessed shape. The paste-like unhardened high thermal conductive member  105  formed of at least inorganic filler and thermosetting resin is produced. The paste-like unhardened high thermal conductive member  105  is filled in a depressed portion of the heat sink  104 .  
         [0197]    Finally, the multi-layer board  101  and a heat sink  104  are laminated so that the side of the multi-layer board  101  to which the electronic components  109  is mounted is set as opposed to the high thermal conductive member  105  filled in the depressed portion of the heat sink  104 . The high thermal conductive member  105  remains substantially uniform in thickness at the part to which the electronic component requiring heat dissipation  109  is not mounted. The high thermal conductive member  105  is hardened by use of a heating oven, thereby that the surfaces of the electronic component requiring heat dissipation  109  mounted to the multi-layer board  101  are coated with the high thermal conductive member  105  (embedded in the high thermal conductive member  105 ) to complete the power module  1207 .  
         [0198]    &lt;&lt;Eighteenth Embodiment&gt;&gt; 
         [0199]    A production method of the power module  1207  shown in FIG. 12 will be described referring to FIG. 18. FIG. 18 is a process chart showing a production method of the power module  1207  shown in FIG. 12 in accordance with a eighteenth embodiment.  
         [0200]    Since a first step (FIG. 18( a )) and a second step (FIG. 18( b )) of the eighteenth embodiment are the same as the first step (FIG. 16( a )) and the second step (FIG. 16( b )) of the sixteenth embodiment, explanations thereof are omitted.  
         [0201]    Next, in a third step shown in FIG. 18( c ), the multi-layer board  101  and the heat sink  104  are disposed so that each side of the multi-layer board  101  faces to the high thermal conductive member  105  filled in the depressed portion of the heat sink  104 . The high thermal conductive member  105  remains substantially uniform in thickness at the part to which the electronic components requiring heat dissipation  103  and  109  are not mounted. The high thermal conductive member  105  is hardened by use of a heating oven, thereby that the high thermal conductive member  105  coats the surfaces of the electronic components requiring heat dissipation  103  and  109  mounted to the multi-layer board  101  (or embeds part of the electronic components therein) to complete the power module  1207 .  
         [0202]    In the production method of the eighteenth embodiment, the heat sink  104  and the high thermal conductive member  105  are adhered to both sides of the multi-layer board  101  simultaneously. As the production method of this embodiment has less number of steps than the production method of the seventeenth embodiment, the power module  1007  of the twelfth embodiment can be produced at a lower cost.  
         [0203]    All steps in the production method of the eighteenth embodiment are carried out at normal pressures. Since air in the voids within the unhardened member  105  comes out of the through hole  102  and space between the high thermal conductive member  105  and the multi-layer board  101 , the electronic components  103  and  109  can be brought into coherent with the member  105  with reliability.  
         [0204]    By producing the power module with the methods in accordance with the fourth to seventh embodiments and the thirteenth to eighteenth embodiment, heat generated from the electronic components  103  (or  103  and  109 ), each of which has an arbitrary different height, can be transferred to the heat sink  104  via the high thermal conductive member  105 . Hence, the method of producing the power module with a good heat dissipation characteristic can be achieved. Furthermore, by adhering the high thermal conductive member  105  to the heat sink  104  and unifying them, it is possible to reduce contact thermal resistance and to achieve the method of producing the power module with a good heat dissipation characteristic.  
         [0205]    In the power module of the ninth to twelfth embodiment, needless to say, the electronic component  106  may be mounted to the side of the multi-layer board  101 , to which the electronic component requiring heat dissipation  109 , is mounted.  
         [0206]    In the thirteenth to fifteenth embodiment, the paste-like unhardened high thermal conductive member  105  is printed to the heat sink  104  of uniform thickness so as to have a certain thickness, the heat sink  104  to which the high thermal conductive member  105  is printed is disposed on the side of the multi-layer board  101 , to which the electronic component is mounted, and the laminated body is pressurized and heated. Alternatively, it is possible, of course, that the sheet-like high thermal conductive member  105  and the heat sink  104  are disposed on the side of the multi-layer board  101  to which the electronic component is mounted and the laminated body is pressurized and heated (the method in FIG. 4 (fourth embodiment)).  
         [0207]    According to the present invention, the advantageous effect of achieving a power module that has a constitutional characteristics including good heat dissipation characteristic, high thermal resistance reliability, low cost and high productivity can be obtained.  
         [0208]    According to the present invention, the advantageous effect of achieving a power module that efficiently takes heat occurring in the parts of various heights mounted to the circuit board by use of a multipurpose heat sink or a simple-shaped heat sink can be obtained.  
         [0209]    According to the present invention, the advantageous effect of achieving a lightweight power module due to miniaturization and weight saving of heat radiating member.  
         [0210]    Although the invention has been described in its preferred form with a certain degree of particularity, it is understood that the present disclosure of the preferred form has been changed in the details of construction and the combination and arrangement of parts may be resorted to without departing from the spirit and the scope of the invention as hereinafter claimed.