JP4998183B2 - Electronic equipment - Google Patents

Description

  The present invention relates to an electronic device in which an electronic component is mounted on the front surface and a heat sink is provided on the back surface of a substrate on which a thick film resistor is mounted on the back surface.

  This type of electronic device is used, for example, as an electronic device such as an automobile ECU. In recent years, an ECU in a conventional vehicle compartment is installed in an engine room where the use environment is severe due to a demand for a large vehicle compartment space. It has become so.

  This type of electronic device generally has a laminated substrate formed by laminating a plurality of ceramic layers, and an electronic component such as a semiconductor chip is provided on the surface which is one plate surface of the substrate, and the back surface which is the other plate surface. Furthermore, in order to protect the thick film resistance on the back surface side, the entire back surface including the thick film resistance is covered with a protective resin (for example, see Patent Document 1).

In general, for such a substrate, a heat sink is attached to the back side of the substrate via an adhesive having high thermal conductivity, and the heat of the substrate is radiated from the back side via the heat sink. Yes.
JP 2003-59962 A

  By the way, in the above-described conventional electronic device, the main heat dissipation function depends on the path from the back surface of the substrate to the heat sink, but the protective resin with poor heat dissipation covers the entire back surface of the substrate. There is a problem that heat generated in the substrate is not efficiently discharged to the heat sink.

  The present invention has been made in view of the above-described problems. An electronic component is mounted on the surface of the substrate, a thick film resistor coated with a protective resin is mounted on the back surface, and a heat sink is provided on the back surface of the substrate. An object of the present invention is to reduce the protective resin interposed between the back surface of the substrate and the heat sink as much as possible.

  In order to achieve the above object, according to the present invention, the back surface (12) of the substrate (10) is provided with a recess (40) recessed from the back surface (12), and the thick film resistor (30) is provided with a recess ( 40), and the protective resin (32) seals the thick film resistor (30) in the recess (40) and remains in the recess (40).

  According to this, since the thick film resistor (30) and the protective resin (32) covering the thick film resistor (32) remain in the recess (40), it is between the back surface (12) of the substrate (10) and the heat sink (50). The intervening protective resin (32) can be reduced as much as possible.

  As a result, heat dissipation through the heat sink (50) is improved, or the protective resin (32) is reduced on the back surface (12) of the substrate (10), and other electronic components are arranged. This also makes it possible to improve the mounting density.

  Here, a conductor layer (14) that is not electrically connected to other parts is provided in a part on the inner side of the thick film resistor (30) in the substrate (10). 14) may be configured to be drawn to the back surface (12) of the substrate (10) and to dissipate the heat of the thick film resistor (30) to the heat sink (50) (FIGS. 1 and 2 described later). reference). According to this, it becomes easy to secure a heat dissipation path for the thick film resistor (30) located in the recess (40).

  Further, if the side surface of the recess (40) is a tapered surface inclined so as to expand from the bottom side toward the opening side (see FIG. 6 described later), the bottom surface of the recess (40) It is preferable to ease the stress concentration at the corner formed by the side surface and to increase the contact area between the protective resin (32) and the inner surface of the recess (40).

  Moreover, if the surface roughness of the inner surface of the recess (40) is larger than the surface roughness of the back surface (12) of the substrate (10) located outside the recess (40), the thickness in the recess (40) will be increased. The adhesion of the membrane resistance (30) and the protective resin (32) is improved.

  In addition to the electronic components (20-22) on the front surface (11) side, other electronic components (25, 26, 27) are mounted on the recesses (40) on the back surface (12) of the substrate (10). (See FIGS. 8 to 11 to be described later). Thus, you may mount another electronic component (25-27) using the space on a recessed part (40) in the back surface (12) of a board | substrate (10).

  In addition, the code | symbol in the bracket | parenthesis of each means described in the claim and this column is an example which shows a corresponding relationship with the specific means as described in embodiment mentioned later.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following embodiments, parts that are the same or equivalent to each other are given the same reference numerals in the drawings in order to simplify the description.

(First embodiment)
FIG. 1 is a diagram showing a schematic cross-sectional configuration of an electronic device 100 according to the first embodiment of the present invention, and FIG. 2 is an enlarged view showing a thick film resistor 30 and its vicinity in the electronic device 100. (A) is a schematic sectional view, and (b) is a schematic plan view.

The substrate 10 is a ceramic laminated substrate in this example, and this substrate 10 is formed by laminating a plurality of ceramic layers 10a. Each ceramic layer 10a is, for example, a sheet body made of particles mainly composed of AlN, SiC, SiN, Al ₂ O ₃ , or a glass component (for example, SiO ₂ , MgO, CaO, etc.) for fusing these particles. ).

  Here, in the substrate 10 which is a laminated substrate, the upper plate surface 11 in FIG. 1 is the front surface 11 of the substrate 10, and the lower plate surface 12 is the rear surface 12 of the substrate 10. In addition, on the front and back surfaces 11 and 12 of the substrate 10 and inside, electrical wirings 13 constituting the circuit of the substrate 10 are formed. Here, in FIG. 1, in order to distinguish the electric wiring 13 from the heat radiation wiring 14 described later, the electric wiring 13 is indicated by hatching, and the heat radiation wiring 14 is indicated by dot hatching.

  The electrical wiring 13 is made of an alloy layer mainly composed of at least one of Au, Ag, Cu, Pt, Pd, Mo, W, and Ni, or a single metal layer, and a paste or foil of these materials is used. Is formed.

  The electrical wiring 13 formed on the front and back surfaces 11 and 12 of the substrate 10 is formed on the outer surface of the ceramic layer 10 a constituting the front surface 11 and the back surface 12 of the substrate 10. Moreover, what is formed in the board | substrate 10 among the electrical wiring 13 is comprised as a via layer formed in each ceramic layer 10a, and a conductor layer formed between each ceramic layer 10a. The front and back surfaces 11 and 12 of the substrate 10 and the internal electric wirings 13 are electrically connected to each other.

  Here, a surface wiring layer 13 a is provided on the outermost surface of the electrical wiring 13 formed on the front and back surfaces 11 and 12 of the substrate 10. The surface wiring layer 13a is made of a multilayer conductor or alloy layer mainly composed of at least one of Cu, Ni, Au, Ag, Pt, and Pd. For example, plating, thick film printing, sputtering, vapor deposition Or by etching or the like.

  As shown in FIG. 1, various electronic components 20, 21, and 22 are mounted on the surface 11 of the substrate 10. These electronic components 20 to 22 are surface mount components such as flip chips and IC chips.

  And these electronic components 20-22 are electrically connected with respect to the electric wiring 13 formed in the surface 11 of the board | substrate 10 via electroconductive connection materials 21a and 22a, such as bump 20a, solder, or an electroconductive adhesive agent. It is connected to the. Although not shown, these electronic components may be connected to the electrical wiring 13 with bonding wires.

A thick film resistor 30 is provided on the back surface 12 side of the substrate 10. The thick film resistor 30 is a resistor including LaB ₆ , SnO ₂ , CuNi, RuO ₂ , Bi ₂ Ru ₂ O ₇ , and one or more of these components among carbon.

  Here, in this embodiment, as shown in FIGS. 1 and 2, the back surface 12 of the substrate 10 is provided with a recess 40 that is recessed from the back surface 12. The recess 40 is provided in the ceramic layer 10 a constituting the back surface 12 of the substrate 10. The thick film resistor 30 is accommodated in the recess 40.

  The thick film resistor 30 is electrically connected to the electrical wiring 13 located in the recess 40 on the back surface 12 side of the substrate 10. In the recess 40, the thick film resistor 30 is sequentially covered and protected by a protective glass 31 and a protective resin 32.

Here, the protective glass 31 is made of an insulating sheet having as a main component at least one of glass components (SiO ₂ , MgO, CaO), and the protective resin 32 is made of epoxy, urethane, acrylic, phenolic. It consists of a thermosetting type, UV curable type, heat drying type resist film, etc. in which a resin component such as an imide type, an amide type, or a silicone type is mixed with a filler mainly for heat dissipation.

  As shown in FIGS. 1 and 2, the protective resin 32 seals the thick film resistor 30 and the protective glass 31 in the recess 40, and does not protrude from the back surface 12 of the substrate 10. Stays.

  Further, in the portion of the substrate 10 on the inner side of the thick film resistor 30, that is, the portion on the inner side of the substrate 10 than the recess 40, the heat radiation wiring 14 as a conductor layer that is not electrically connected to other portions. Is provided.

  The heat dissipation wiring 14 is made of the same material as the electrical wiring 13 and is formed on the front and back surfaces 11 and 12 of the substrate 10 and the inside of the substrate 10 by the same method as the electrical wiring 13. Of the heat radiating wires 14, those located on the inner side of the thick film resistor 30 are drawn to the front surface 11 and the back surface 12 of the substrate 10.

  Here, the surface wiring layer 13a similar to the above is provided on the outermost surface of the heat radiation wiring 14 located on the front and back surfaces 11 and 12 of the substrate 10. In addition, about the thermal radiation wiring 14, this surface wiring layer 13a may not exist.

  A heat sink 50 is provided on the back surface 12 side of the substrate 10 to receive heat from the back surface 12 and dissipate heat. The heat sink 50 is made of Cu, Al, or the like, and is thermally connected to the back surface 12 of the substrate 10 through the heat radiating gel 60. The heat dissipating gel 60 is a gel having excellent thermal conductivity such as a silicone gel.

  Furthermore, in this embodiment, the heat radiation wiring 14 and the heat sink 50 located on the back surface 12 of the substrate 10 are thermally connected via the heat conductive connection member 61 having excellent heat conductivity. The thermally conductive connecting member 61 is, for example, solder, Ag paste, silicone grease, silicone adhesive, gel, or the like.

  As a result, the heat of the thick film resistor 30 passes through the heat radiation wiring 14 drawn from the heat radiation wiring 14 provided on the inner side of the thick film resistance 30 in the substrate 10 to the back surface 12 of the substrate 10. The heat sink 50 is configured to dissipate heat. In addition, in order to relieve the stress applied to the connection portion between the heat radiation wiring 14 and the heat sink 50, it is desirable that the metal materials of the both 14 and 50 are the same material.

  By the way, according to the present embodiment, the recess 40 is provided on the back surface 12 of the substrate 10, and the thick film resistor 30 and the protective resin 32 covering the thick film resistor 30 are retained in the recess 40. The protective resin 32 interposed between the two can be reduced as much as possible. Therefore, the heat dissipation through the heat sink 50 is improved.

  This will be specifically described with reference to FIG. 2A and FIG. FIG. 3 is a schematic cross-sectional view showing the main part of an electronic device as a comparative example, which was prototyped by the present inventor based on the prior art.

  In the comparative example shown in FIG. 3, the thick film resistor 30 is electrically connected between the electrical wirings 13 located on the back surface 12 of the substrate 10, and the protective glass 31 and the protective resin 32 are formed thereon. . In this case, the heat dissipation path to the heat sink 50 is substrate 10 → protective resin 32 → heat dissipating gel 60 → heat sink 50, and since the protective resin 32 is interposed, the thermal conductivity of the ceramic substrate 10 that should be good is fully utilized. I can't.

  In the present embodiment, the concave portion 40 is provided on the back surface 12 of the substrate 10 and the thick film resistor 30, the protective glass 31, and the protective resin 32 are embedded therein, so that the heat radiation path of the substrate 10 → the heat radiation gel 60 → the heat sink 50. Exists.

  In other words, by removing the protective resin 32 from the back surface 12 of the substrate 10, a blank is generated on the back surface 12 of the substrate 10, and a heat sink directly from the substrate 10 having good heat dissipation, apart from the heat dissipation path through the protective resin 32 in the comparative example. 50 can be dissipated. For this reason, in the present embodiment, heat radiation to the heat sink 50 can be performed efficiently.

  Further, in the present embodiment, as shown in FIG. 1, since the heat radiation wiring 14 drawn from the inside of the substrate 10 to the front and back surfaces 11 and 12 is provided, the heat radiation of the substrate 10 by the heat radiation wiring 14 is also possible. Become. Further, the heat radiation wiring 14 is routed from the vicinity of the thick film resistor 30 to the back surface 12 of the substrate 10 inside the substrate 10, whereby the heat of the thick film resistor 30 can be efficiently radiated to the heat sink 50. ing.

  Next, a specific example of a method for manufacturing the electronic device 100 shown in FIG. 1 will be described. First, the green sheet used as each ceramic layer 10a is prepared, the said electrical wiring 13 and the heat dissipation wiring 14 are formed with respect to this green sheet, Then, each green sheet is laminated | stacked.

  At this time, the method for forming the recess 40 specifically includes the first example shown in FIG. 4 and the second example shown in FIG. In FIGS. 4 and 5, each green sheet is denoted by reference numeral 10 a as the ceramic layer 10 a before firing.

  First, in the first example shown in FIG. 4, the recess 40 is formed by the press die K. At this time, using a press die K having a convex portion for forming the concave portion 40, the green sheets are laminated and the concave portion 40 is formed in a lump. Although this method is the simplest method of forming, since a large load is applied to the green sheet portion near the recess 40, large shrinkage force variation (dimensional variation) is likely to occur during firing.

  Therefore, the pressing may be performed twice. Specifically, after the green sheets are stacked and pressed as in the conventional case, only the concave portion 40 is partially pressed by the press die K. By doing so, it is possible to reduce the partial shrinkage variation described above. It should be noted that both of the method of performing the press once and the method of performing the press may be performed before or after the press for forming the electric wiring 13 in the recess 40.

  Moreover, the 2nd example shown by FIG. 5 is a lamination | stacking system. As in the conventional method, the green sheets are stacked and pressed after each green sheet is formed, but the hole 40a for forming the recess 40 is provided only in the lowermost green sheet, and then the green sheets are stacked. . This is considered to be a method that can reduce the effect of shrinkage most.

In this way, a laminated body formed by laminating the green sheets in which the electric wiring 13, the heat radiation wiring 14, and the recess 40 are formed is completed. Thereafter, this laminate is fired to form the substrate 10. At this time, the laminate contracts somewhat like a general one. Moreover, when each wiring 13 and 14 is formed with a paste, it is sintered together with firing of the laminate.
Next, the surface wiring layer 13a is formed on the surfaces of the wirings 13 and 14 located on the front and back surfaces 11 and 12 of the substrate 10 by plating or the like. Next, the thick film resistor 30, the protective glass 31, and the protective resin 32 are sequentially formed in the concave portion 40 on the back surface 12 of the substrate 10 by printing and baking. Subsequently, by mounting the electronic components 20 to 22 on the surface 11 of the substrate 10, the electronic device 100 of the present embodiment is completed.

  Here, with reference to FIG. 2, the dimensional configuration and the like of the thick film resistor 30, the recess 40, and the peripheral portion thereof will be described. First, the depth Tc of the recess 40 will be described with reference to FIG. The thickness Tb of each ceramic layer 10a constituting the substrate 10 is usually adjusted to 0.15 to 0.25 mm in consideration of the conductor paste filling in the through hole.

  Accordingly, the recess 40 formed therein is shallower than the thickness Tb of the ceramic layer 10a. However, when considering the depth Tc of the recess 40, the following two things must be considered.

  One is that the thickness (Tb-Tc) between the thick film resistor 30 provided in the recess 40 and the electrical wiring 13 in the ceramic layer 10a on the upper side thereof is 0.05 mm or more. desirable. Second, in order to ensure the printability of the electrical wiring 13 and the thick film resistor 30 in the recess 40, it is desirable that the thickness (Tb−Tc) be 0.15 mm or less.

  Next, description will be made with reference to FIG. The thick film resistor 30 is connected so as to straddle between the pair of electric wirings 13, but the dimensions L and W of the portion that substantially functions as the thick film resistor 30 are both 0.5 mm or more and L ≧ W is required. There is. If possible, these dimensions L and W are preferably 1.0 mm or more.

  Further, with respect to the margin S1 where the electric wiring 13 and the thick film resistor 30 do not overlap and the overlap S2 between the electric wiring 13 and the thick film resistor 30, the printed thick film resistor 30 is not thinned by the electric wiring 13. Therefore, it is necessary to secure a length obtained by adding 0.1 m to the shrinkage dimension deviation of the substrate 10 during firing.

  Further, the overlap between the thick film resistor 30 and the protective glass 31 and the protective resin 32 needs to overlap by 0.1 mm or more from the viewpoint of preventing the resistance value deterioration due to the pressure resistance and water absorption. Furthermore, in view of quality, an overlap of 0.1 mm or more including the electric wiring 13 is desirable. This means that in FIG. 2B, the opening shape of the recess 40 is indicated by a broken line 40, and the distance S3 between the broken line 40 and the thick film resistor 30 and the electric wiring 13 is 0.1 mm or more. .

(Second Embodiment)
FIG. 6 is a diagram showing a schematic cross-sectional configuration of the main part of the electronic device according to the second embodiment of the present invention, and is an enlarged view showing the thick film resistor 30 and its vicinity in the electronic device. The present embodiment is a modification of the recess 40 in the first embodiment, and can be applied in combination with the first embodiment.

  As shown in FIG. 6, in this embodiment, the side surface of the recess 40 is a tapered surface that is inclined so as to expand from the bottom side toward the opening side. Here, the angle of the corner formed by the bottom surface and the side surface of the recess 40 is defined as θ.

  According to this, the stress concentration at the corner portion formed by the bottom surface and the side surface of the concave portion 40 can be easily relaxed, and cracking or disconnection of the electric wiring 13 positioned at the corner portion can be prevented. In the first embodiment, the angle θ is 90 °. However, in this embodiment, the contact area between the protective resin 32 and the protective glass 31 and the inner surface of the recess 40 can be increased. The sealing by the protective resin 32 and the protective glass 31 can be ensured.

  However, if the angle θ of the recess 40 is large, there is a greater concern about cracks and disconnection of the electrical wiring 13 described above. If the angle θ is small, the back surface 12 of the substrate 10 has a large area in the recess 40. The effect of embedding the thick film resistor 30 in the recess 40 is reduced. Therefore, it is desirable to adjust the angle θ by 30 to 70 °.

  FIG. 7 is a schematic cross-sectional view showing another example of the second embodiment, and is a view showing a cross-sectional shape of the recess 40 alone. The recess 40 does not want to be large, but when it is desired to increase the contact area between the protective resin 32 and the protective glass 31 and the inner surface of the recess 40, as shown in FIG. What is necessary is just to R process a part. The size of the radius of curvature R of the corner may be the same as the depth t of the recess 40.

  For improving the adhesion between the thick film resistor 30, the protective resin 32 and the protective glass 31 and the inner surface of the recess 40, the surface roughness of the inner surface of the recess 40 may be increased. Specifically, the surface roughness of the inner surface of the recess 40 may be made larger than the surface roughness of the back surface 12 of the substrate 10 located outside the recess 40.

  By doing so, the area of the thick film resistor 30 in contact with the inner surface of the recess 40 is increased and heat dissipation is improved, and the areas of the protective resin 32 and the protective glass 31 that are also in contact with the inner surface of the recess 40 are increased. It is expected that adhesion will be improved.

  As an index of the surface roughness, since the ceramic particle diameter constituting the conventional substrate 10 is about several μm, the conventional surface roughness is about 0.5 μm in average roughness Ra, but this is doubled. A large effect can be expected by making the roughness as large as possible.

  As a method for increasing the surface roughness, the surface of a press mold that presses the recess 40 is roughened, or a portion of the ceramic layer 10a that forms the recess 40 has a coarse alumina powder (for example, a particle size of several to 20 μm). What is necessary is just to add.

(Third embodiment)
By the way, according to each of the above embodiments, by storing the thick film resistor 30, the protective glass 31, and the protective resin 32 in the recess 40, the area occupied by the protective resin 32 in the back surface 12 of the substrate 10 is reduced. It is also possible to arrange other electronic components on the back surface 12 of the substrate 10. Then, it leads to the improvement of the packaging density.

  8, 9, and 10 are schematic cross-sectional views illustrating the main part of the electronic device according to the third embodiment of the present invention. FIG. 8 is a first example, FIG. 9 is a second example, and FIG. Is a third example. In any example, other electronic components 25, 26, and 27 are mounted on the recess 40 on the back surface 12 of the substrate 10.

  The first example shown in FIG. 8 is an example of wire connection, in which another electronic component 25 made of an IC chip and the like and the protective resin 32 are fixed with an adhesive 25b, and the other electronic component 25 and the recess 40 are fixed. The electrical wiring 13 provided in the vicinity is connected by a bonding wire 25a such as Al or Au.

  At this time, since a large stress is generated between the protective resin 32 and the other electronic component 25, the adhesive 25b has a thermal expansion close to both 25 and 32, and is as low as about 0.5 to several tens of MPa. It is desirable to use a Young's modulus material such as a silicone adhesive.

  The second example shown in FIG. 9 is an example in which a semiconductor chip is mounted as a bare chip via bumps 26a such as solder or Au as another electronic component 26. Since the electrical wiring 13 cannot be provided on the recess 40, the flip chip mounting is mainly used.

  Further, the third example shown in FIG. 10 is an example in which a chip component is connected as another electronic component 27 with an adhesive 27a such as solder or a conductive adhesive. Since the concave portion 40 is at least about 1 mm in width from the size of the thick film resistor 30, it is limited to a component having a size of 1608 or more.

  As described above, since the protective resin 32 is stored in the recess 40 on the back surface 12 of the substrate 10, by mounting other electronic components 25 to 27 using the empty space on the recess 40, The back surface 12 enables component mounting with a higher density than in the past.

  FIG. 11 is a schematic cross-sectional view showing an electronic device as an application example of the present embodiment. On the back surface 12 of the substrate 10, another electronic component 25 is mounted on the recess 40 and is mounted by a bonding wire 25 a.

  Here, since it is difficult to directly connect the other electronic component 25 provided on the back surface 12 of the substrate 10 to the heat sink 50, the concave portion 51 is provided in a portion of the heat sink 50 facing the other electronic component 25. Then, the same heat dissipating gel 60 and heat dissipating grease are filled therein. By doing so, higher heat dissipation can be realized.

  In addition, the depth of the recessed part 51 of the heat sink 50 is set to a depth at which the other electronic components 25 do not directly hit. Further, the present embodiment can be applied to each of the above embodiments.

(Fourth embodiment)
In the fourth embodiment of the present invention, the heat radiation wiring 14 is improved in consideration of the relationship between the electrical wiring 13 and the heat radiation wiring 14 provided in the substrate 10, and the above corner implementation is performed. Applicable in combination with form.

  FIG. 12 is a partial schematic cross-sectional view showing an internal configuration of the substrate 10 at a site where the electrical wiring 13 and the heat radiation wiring 14 are adjacent to each other. The heat radiation wiring 14 is desirably as large as possible if there is a free space for the electrical wiring 13 in the substrate 10, but is substantially defined by the electrical breakdown voltage and mechanical strength.

  If the electrical wiring 13 and the heat radiating wiring 14 are close to each other, it is difficult to secure an electric withstand voltage between the end A of the electrical wiring 13 and the end A of the heat radiating wiring 14, and between the both ends A-A. The mechanical strength between the ceramic layers 10a decreases, and it becomes easy to peel off.

  Therefore, the fourth embodiment provides a method for improving the electric withstand voltage and mechanical strength between the electric wiring 13 and the heat radiation wiring 14, and reducing the wiring area to reduce the cost. FIG. 13 is a plan view showing the main part of the fourth embodiment of the present invention, and shows a schematic plan configuration of the electrical wiring 13 and the heat radiation wiring 14 adjacent in the substrate 10.

  As shown in FIG. 13, in the present embodiment, the planar shape of the heat dissipation wiring 14 having the wiring width W is made to be a fish bone shape. According to this, since the distance from the electrical wiring 13 can be substantially increased as compared with the heat radiation wiring 14 having a uniform wiring width W, the electrical withstand voltage and mechanical strength can be improved, and the number of wirings can be reduced. Costs are reduced because only materials are required.

  At this time, the width of the bone portion 14a extending to the outer periphery and the width of the middle bone portion 14b are preferably equal. However, in order to have a heat dissipation function equivalent to that of the heat dissipation wiring 14 having the uniform wiring width W, the relationship between the length W1 of the bone portion 14b and the interval W2 between the adjacent bone portions 14a is W1 ≧ W2. Is desirable.

  Furthermore, a void is generated at the interface of the ceramic layer 10a at the tip of the bone portion 14a, and the ceramic layers 10a may be easily separated from each other by the void. FIG. 14 considers this point. FIG. 14 is a schematic plan view showing a heat radiation wiring 14 as another example of the present embodiment.

  As shown in FIG. 14, in the heat radiation wiring 14 having a fish-bone shape, the distal end portion of the bone portion 14 a and the root portion of the adjacent bone portion 14 a are 90 ° as shown in the upper portion in FIG. 14. The following sharp edges are used, or R processing is performed as shown in the lower part of FIG. By doing so, the peeling suppression effect of the said ceramic layers 10a is anticipated.

(Other embodiments)
In each of the above embodiments, the substrate 10 is a laminated substrate formed by laminating a plurality of ceramic layers 10a. However, if the electronic component is provided on the front side and the thick film resistor and the protective resin are provided on the back side, the substrate 10 is a single substrate. It may be a layered substrate.

  Further, even when there is no heat dissipation wiring 14, the effect of improving heat dissipation by exhibiting the thick film resistor 30 and the protective resin 32 in the recess 40 described above is exhibited. For example, in the electronic device 100 shown in FIG. The heat radiation wiring 14 may be omitted. Of course, if the heat dissipation wiring 14 is provided, the said effect by it will be exhibited.

  The electronic device may be entirely sealed with a mold resin. In this case, it is desirable to expose the surface of the heat sink 50 opposite to the connection side with the substrate 10 from the mold resin.

  In each of the above embodiments, as shown in FIG. 2, one thick film resistor 30 is housed in one recess 40, but a plurality of thick film resistors 30 are housed in one recess 40. It may be.

1 is a schematic cross-sectional view of an electronic device according to a first embodiment of the present invention. It is a figure which expands and shows the thick film resistance and its vicinity part in the electronic device in FIG. 1, (a) is a schematic sectional drawing, (b) is a schematic plan view. It is a schematic sectional drawing which shows the principal part of the electronic device as a comparative example which this inventor made as an experiment. It is a figure which shows the 1st example of the formation method of a recessed part. It is a figure which shows the 2nd example of the formation method of a recessed part. It is a schematic sectional drawing of the principal part of the electronic device which concerns on 2nd Embodiment of this invention. It is a schematic sectional drawing which shows another example of the said 2nd Embodiment. It is a schematic sectional drawing which shows the principal part of the electronic device as a 1st example of 3rd Embodiment of this invention. It is a schematic sectional drawing which shows the principal part of the electronic device as a 2nd example of the said 3rd Embodiment. It is a schematic sectional drawing which shows the principal part of the electronic device as a 3rd example of the said 3rd Embodiment. It is a schematic sectional drawing which shows the electronic device as an application example of the said 3rd Embodiment. It is a partial schematic sectional drawing which shows the board | substrate internal structure of the site | part which an electrical wiring and a thermal radiation wiring adjoin. It is a schematic plan view which shows the principal part of 4th Embodiment of this invention. It is a schematic plan view which shows the thermal radiation wiring as another example of the said 4th Embodiment.

Explanation of symbols

10 ... substrate, 11 ... front surface of substrate, 12 ... back surface of substrate,
14 ... Radiation wiring as a conductor layer not electrically connected to other parts,
20, 21, 22 ... electronic components, 25, 26, 27 ... other electronic components,
30 ... thick film resistor, 32 ... protective resin, 40 ... recess, 50 ... heat sink.

Claims (5)

A substrate (10) having one plate surface as a front surface (11) and the other plate surface as a back surface (12);
Electronic components (20, 21, 22) provided on the surface (11) side of the substrate (10);
A thick film resistor (30) provided on the back surface (12) side of the substrate (10);
A protective resin (32) provided on the back surface (12) side of the substrate (10) and covering the thick film resistor (30);
In an electronic device comprising a heat sink (50) provided on the back surface (12) side of the substrate (10) and receiving heat from the back surface (12) to dissipate heat.
The back surface (12) of the substrate (10) is provided with a recess (40) that is recessed from the back surface (12).
The thick film resistor (30) is housed in the recess (40);
The electronic device, wherein the protective resin (32) seals the thick film resistor (30) in the recess (40) and remains in the recess (40). A conductor layer (14) that is not electrically connected to other parts is provided in a part on the inner side of the thick film resistor (30) in the substrate (10),
The conductor layer (14) is drawn to the back surface (12) of the substrate (10) and is configured to radiate heat of the thick film resistor (30) to the heat sink (50). The electronic device according to claim 1. 3. The electronic device according to claim 1, wherein a side surface of the concave portion is a tapered surface that is inclined so as to expand from the bottom side toward the opening side. 4. The surface roughness of the inner surface of the recess (40) is greater than the surface roughness of the back surface (12) of the substrate (10) located outside the recess (40). The electronic device as described in any one. The other electronic component (25, 26, 27) is mounted on the recess (40) on the back surface (12) of the substrate (10). The electronic device described in one.

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