JP2013165202A - Heat dissipation structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat dissipation structure which is easy to transmit heat of a heating element to a case, being suitable for manufacturing a case.SOLUTION: A heat dissipation structure 2 of an inverter 3 disclosed in a present specification includes a case 5 to which semiconductor modules 20 and 30 housing a heating element are fixed, and an undercover 4 fixed to the case 5. The semiconductor modules 20 and 30 are fixed to the case 5 at a plurality of fixing points 22 and 32 with grease held in between. The undercover 4 is made from a material whose thermal expansion coefficient is different from the case 5, and is fixed to the 5 so as to face the semiconductor modules 20 and 30 across a wall of the case 5. The fixing points 22 and 32 are provided to surround the heating element. Further, in a region surrounded with the fixing points, and on a case surface facing the semiconductor modules 20 and 30, a plurality of parallel linear grooves 8 and 9 are provided in which the grease enters. Between adjoining linear grooves, a flat surface which is wider than a groove width is provided.

Description

  The technology disclosed in this specification relates to a heat dissipation structure for an electronic device having a heating element, and relates to a heat dissipation structure that transfers heat from a member containing the heating element to a housing.

  In electronic devices such as inverters and voltage converters for high-power motors, a large number of elements (heating elements) that generate a large amount of heat, such as IGBTs and diodes for switching circuits, are used. Therefore, the heat dissipation structure of the element is important. For element heat dissipation, there are cases where a cooler that flows refrigerant is used and such a cooler is not used.In either case, increasing the heat transfer efficiency to the housing improves the cooling capacity of the element. Connected.

  As a technique for improving the heat transfer efficiency to the housing, for example, there are techniques disclosed in Patent Document 1 and Patent Document 2. In any of the literature techniques, grease having high heat conductivity is interposed between an element module containing a semiconductor element that is a heating element and the casing. However, in order to prevent grease from becoming uneven, A groove is provided so that grease accumulates on the opposite surface of the. In the technique of Patent Document 1, a groove is provided in a region surrounded by a fixing hole provided in the element module so as to follow the outer peripheral line of the region. The technique of Patent Document 1 eliminates the non-uniformity of grease caused by the deformation of the element module due to the force at the time of element module fastening. In the technique of Patent Document 2, a plurality of grooves are provided on the surface of the housing facing the element module.

JP 2006-196576 A JP 2010-92999 A

  The present specification provides a further improved technique for eliminating unevenness of grease applied between an element module containing a heating element and a housing. In particular, when a plate member having a coefficient of thermal expansion different from that of the case is fixed to the surface of the case opposite to the element module fixing surface, the case is deformed and returned to its original state due to the difference in coefficient of thermal expansion. Even if it exists, while preventing a grease defect | deletion area | region between an element module and a housing | casing, the technique suitable for manufacture of the housing | casing made by casting is provided.

  The heat dissipation structure disclosed in this specification includes an element module that stores a heating element, a casing of an electronic device that stores the element module, and a plate member fixed to the casing. The element module is fixed to the housing at a plurality of fixing points with the grease interposed therebetween. The plate member is made of a material having a coefficient of thermal expansion different from that of the casing, and is fixed to the casing so as to face the element module with the wall of the casing interposed therebetween. The fixing location of the element module is provided so as to surround the heating element. In the technology disclosed in this specification, a plurality of parallel linear grooves into which grease enters are provided in a region surrounded by the above-mentioned fixing portion on the housing surface facing the element module, and a line is provided between adjacent linear grooves. A flat surface wider than the groove width is provided. Here, the linear groove means a groove extending straight from end to end. In the following, a region where the linear groove and the flat surface are provided may be referred to as a heat radiating portion.

  The heating element is a semiconductor element such as an IGBT or a diode, a resistance element, or a capacitor. The element module including the heating element may be a package in which a semiconductor element is molded, or a unit in which the package and the cooler are integrated. Further, the plate member may be an iron plate that reinforces the casing, or a bracket for attaching the casing to another device. The casing is typically made of aluminum die casting, and the plate member is an iron undercover (lower shielding plate).

  In the above heat dissipation structure, the heat dissipation portion is provided with a plurality of linear grooves and a flat surface wider than these groove widths. With such a structure, the grease interposed between the heat radiating portion and the cooler is stored in the plurality of linear grooves, and the heat of the heating element is easily transmitted to the casing by the wide flat surface. In particular, due to the difference in thermal expansion coefficient between the case and the plate member, the case and the element are deformed into a convex shape (the case is concave toward the plate member side) due to the heat of the heating element. Even if the gap between the modules becomes uneven, grease remains in the linear groove. For this reason, when the deformation of the casing is restored, the grease remaining in the linear groove returns to the gap, thereby preventing the occurrence of a grease deficient region.

  In the above heat dissipation structure, a plurality of linear grooves parallel to each other are provided. By making the extending direction of the linear groove coincide with the direction of the molten metal flow in the casting of the casing, the molten metal can easily flow into the linear groove. That is, a housing employing the above heat dissipation structure is easy to manufacture. The technology of the present specification provides a structure that prevents a grease defect region and is easy to cast. The technique disclosed in this specification is suitable for a casing made of cast, and particularly suitable for a casing made of die casting.

  The above heat dissipation structure may be configured such that the region (heat dissipating part) where the linear groove is provided is one step higher than the surrounding part. Thereby, since a heat radiating part becomes a base shape, the heat by a heat generating body concentrates and the concentrated heat can be efficiently transmitted to a case. Moreover, even if the heat radiating portion has a pedestal shape, the plurality of linear grooves formed in the heat radiating portion extend in parallel so that the molten metal flows easily at the time of casting, so that the housing can be easily manufactured.

  In the above heat dissipation structure, the surface of the flat surface is preferably smoother than the surface inside the groove of the linear groove. The smooth flat surface reduces the thickness of the grease, so that heat is easily transferred to the housing. On the other hand, it becomes easy to hold | maintain grease in a groove | channel by the surface in a linear groove | channel coarser than the surface of a flat surface.

  In the above heat dissipation structure, it is preferable that the plurality of linear grooves have a narrower groove interval (that is, a flat surface width) at the center in the alignment direction of the linear grooves than a groove interval at the end in the alignment direction. This is to make it easier for grease to collect in the center where heat tends to concentrate. Moreover, it is preferable that the linear groove is provided at a position overlapping the heating element when viewed from the stacking direction of the housing and the element module. This is to prevent the grease from being lost directly under the heating element.

  Details of the technology disclosed in this specification and further improvements will be described in the embodiments of the present invention.

It is a top view of the bottom part of the housing | casing of an inverter. It is a top view of the bottom part of the inverter housing | casing which removed the semiconductor module. It is sectional drawing along the III-III line | wire shown in FIG. It is sectional drawing along the IV-IV line shown in FIG. It is an expanded sectional view of a groove part. It is a top view of the die-casting type | mold which makes a housing | casing. It is sectional drawing which shows the thermal radiation structure of 2nd Example.

  The heat dissipation structure of the embodiment will be described with reference to the drawings. The device targeted by the heat dissipation structure 2 of the embodiment is an inverter 3 of an electric vehicle. FIG. 1 is a plan view of the bottom of the casing 5 of the inverter 3. Two semiconductor modules 20 and 30 are fixed to the upper surface of the bottom of the housing 5. Although the housing 5 has a box shape, the bottom of the housing to which the semiconductor modules 20 and 30 are fixed will be described below, and the description of the entire housing will be omitted.

  The semiconductor module 20 includes therein semiconductor chips 21a, 21b, and 21c in which a plurality of semiconductor elements such as IGBTs are molded with resin. The semiconductor module 30 contains therein a semiconductor chip 31 in which a plurality of semiconductor elements such as IGBTs are molded with resin. In FIG. 1, the semiconductor chip built in the semiconductor module is shown in gray. Further, in FIG. 1, the wiring of the semiconductor element is omitted. Semiconductor elements such as IGBTs housed in the semiconductor modules 20 and 30 are elements constituting a switching circuit in a converter circuit or an inverter circuit for converting battery power into AC power suitable for motor driving. Since a large current flows through the elements housed in the semiconductor modules 20 and 30, the amount of heat generated is large. In the inverter 3, such elements that generate a large amount of heat are integrated and cooled intensively.

  The semiconductor module 20 is fixed to the bottom of the housing 5 with four bolts 22. Six linear grooves 8 (linear grooves) are formed in a region on the bottom surface of the housing 5 and facing the semiconductor module 20. The semiconductor module 30 is fixed to the bottom of the housing 5 with four bolts 32. In the region facing the semiconductor module 30 on the bottom surface of the housing 5, five linear grooves 9 (linear grooves) are formed. “Line groove” means a straight groove from end to end. A group of grooves indicated by reference numeral 9 extend parallel to each other. A group of grooves indicated by reference numeral 8 also extend parallel to each other. The overall arrangement of the plurality of grooves is determined so that there are many portions where the grooves overlap with the semiconductor chip as seen in the plan view of FIG.

  Grease with high thermal conductivity is applied between the semiconductor module 20 and the bottom of the housing 5. Grease is also applied between the semiconductor module 30 and the bottom of the housing 5. The grease is applied to diffuse the heat of the semiconductor element well from the semiconductor module to the housing 5. Grease also collects in the grooves 8 and 9. The grooves 8 and 9 will be described in detail later.

  An under cover 4 is attached to the outside of the bottom of the inverter 3 (the lower surface of the inverter 3). Although the inverter 3 is fixed to the engine compartment of the vehicle, the under cover 4 is attached for the purpose of protecting the inverter 3 from pebbles that jump up from the road surface. The under cover 4 is fixed to the inverter 3 with bolts 6 from below. The housing 5 is manufactured by aluminum die casting, and the under cover 4 is made of iron. The casing 5 and the under cover 4 are fixed to each other by bolts 6. Since the casing 5 and the under cover 4 have different coefficients of thermal expansion, the casing 5 deforms due to the difference in coefficient of thermal expansion when the temperature rises. . When the housing 5 is deformed and the bottom surface of the housing 5 is curved, the gap between the bottom surface and the semiconductor modules 20 and 30 becomes non-uniform, and the grease is pushed out from a narrow area to a wide area. However, when the temperature is lowered and the deformation is restored, the grease accumulated in the grooves 8 and 9 comes out on the surface of the housing, so that there is a grease defect region between the bottom surface and the semiconductor modules 20 and 30. Not likely to occur. Next, the structure of the grooves 8 and 9 will be described in detail.

  FIG. 2 shows a plan view of the bottom of the inverter 3 with the semiconductor modules 20 and 30 removed. FIG. 3 is a sectional view taken along line III-III in FIG. FIG. 4 is a sectional view taken along line IV-IV in FIG. The cross-sectional view of FIG. 4 corresponds to the cross-sectional view of FIG. 3 with the semiconductor module 30 removed. In addition, the code | symbol G in FIG. 3 has shown the grease.

  As shown in FIG. 1, a group of grooves positioned below the semiconductor module 20 are collectively referred to as “grooves 8”. However, when individual grooves are shown, the grooves 8a are formed from the left side of the drawing as shown in FIG. , 8b, 8c, 8d, 8e, 8f. A group of grooves positioned below the semiconductor module 30 are collectively referred to as “grooves 9”. However, when individual grooves are illustrated, they are referred to as grooves 9 a, 9 b, 9 c, 9 d, and 9 e from the left side of FIG. 2. The flat surface between the groove 8a and the groove 8b is referred to as an inter-groove plane 12a. Similarly, the flat surface between the groove 8b and the groove 8c is referred to as an inter-groove plane 12b, the flat surface between the groove 8c and the groove 8d is referred to as an inter-groove plane 12c, and the flat surface between the groove 8d and the groove 8e. The flat surface between the grooves 8e and 8f is referred to as an inter-groove plane 12e. Similarly, the flat surface between the groove 9a and the groove 9b is referred to as an inter-groove plane 13a, the flat surface between the groove 9b and the groove 9c is referred to as an inter-groove plane 13b, and the flat surface between the groove 9c and the groove 9d. This is referred to as an inter-groove plane 13c, and the flat surface between the grooves 9d and 9e is referred to as an inter-groove plane 13d. The inter-groove planes 12 a to 12 e may be collectively referred to as the inter-groove plane 12, and the inter-groove planes 13 a to 13 d may be collectively referred to as the inter-groove plane 13.

  As described above, the semiconductor module 20 is fixed to the casing 5 of the inverter 3 with the four bolts 22. Fixing holes 7a for passing bolts are provided at four locations on the bottom of the housing 5. The fixing hole 7a is disposed so as to surround the semiconductor chips 21a, 21b, and 21c (semiconductor element) (see also FIG. 1). The six grooves 8 are formed in a region surrounded by the four fixed holes 7a (region surrounded by a broken line 14 in FIG. 2). The same applies to the semiconductor module 30 side, and the five grooves 9 are formed in a region surrounded by four fixing holes 7b (a region surrounded by a broken line 15 in FIG. 2). A region in which the six grooves 8 and the inter-groove plane 12 are formed may be referred to as a heat dissipation portion 14, and a region in which the five grooves 9 and the inter-groove plane 13 are formed may be referred to as a heat dissipation portion 15. The heat radiating portion 14 corresponds to a surface that contacts the semiconductor module 20 in the housing 5, and the heat radiating portion 15 corresponds to a surface that contacts the semiconductor module 30.

  Five grooves 9 (wire grooves) extend in parallel to each other. As well shown in FIG. 4, the width of the groove is constant at W1. However, the width of the inter-groove plane 13 is narrow at the center in the direction in which the plurality of grooves 9 are arranged and wide at the ends. That is, the width Lb of the outermost inter-groove planes 13a and 13d is larger than the width La of the inter-groove planes 13b and 13c close to the center. Further, the widths La and Lb of the planes between the grooves are larger than the groove width W1.

  The same applies to the six grooves 8. The six grooves 8 extend in parallel to each other, and any groove width is smaller than the width of the inter-groove plane. The width of the inter-groove plane 12 becomes narrower as it approaches the center from the outside in the direction in which the plurality of grooves 8 are arranged. The outermost inter-groove planes 12a and 12e are the widest, and the inter-groove plane 12c closest to the center is the narrowest. The width of the inter-groove planes 12b and 12d located in the middle is smaller than the width of the inter-groove plane 12a and larger than the width of the inter-groove plane 12c.

  As shown well in FIG. 3, the semiconductor module 30, the bottom of the housing 5, and the under cover 4 are in a stacked state, and the groove 9 is a semiconductor chip 31 (semiconductor in the semiconductor module 30 when viewed from the stacking direction). (See also FIG. 1).

  As well shown in FIG. 3, grease G is applied between the bottom of the housing 5 and the semiconductor module 30, and the grease G also enters the grooves 9 of the parallel filaments. After the bottom of the housing 5 is deformed and the gap between the semiconductor module 30 becomes non-uniform and the gap returns to the original state, the grease in the groove 9 is supplied between the housing 5 and the semiconductor module 30. This prevents the formation of a grease-deficient region. In particular, since the groove 9 is closer to the center of the semiconductor module 30 because the groove interval is narrower (because the width of the plane between the grooves is narrower), the groove area per unit area increases and the gap becomes narrower. When the grease is saved, the number of places for saving increases. As such, the groove 9 contributes to prevention of occurrence of a grease defect region. The same effect can be expected for the groove 8.

  FIG. 5 shows an enlarged cross-sectional view near the grooves 9c and 9d. In FIG. 4, the grease is not shown. As well shown in FIG. 5, the cross-sectional shape of the groove is generally U-shaped so that grease easily flows. Further, the width W1 of the groove 9 is smaller than the width La of the inter-groove plane 13c. As shown in FIG. 4, since the width La of the inter-groove plane 13 c is the narrowest in the heat radiating portion 15, the width W <b> 1 of the groove 9 is smaller than the width of all the inter-groove planes in the heat radiating portion 15. Further, the depth D1 of the groove is 1/5 or less of the thickness H1 of the housing 5. By not increasing the depth of the groove, the strength reduction of the housing 5 is suppressed. The same applies to the groove 8.

  Further, the surface of the inter-groove flat surface 13 c is smoother than the surface inside the groove 9. In other words, the surface roughness of the surface of the inter-groove plane 13 c is finer than the surface roughness of the surface inside the groove 9. Since the surface roughness of the plane between the grooves is fine, the grease thickness is reduced, and heat is easily transmitted from the semiconductor chip to the housing. On the other hand, since the surface roughness in the groove is rough, it is easy to hold the grease.

  The fact that the grooves 8 and 9 are parallel to each other has the following advantage. The housing 5 is made by die casting. FIG. 6 shows a plan view of a die casting mold 101 for making the housing 5. The die casting mold of FIG. 6 is a mold that forms the inner bottom surface of the housing 5. The inside of the bottom surface of the housing 5 corresponds to the shape shown in FIG. The cavity surface 105 of the die-cast die 101 has a shape in which the shape of the bottom surface shown in FIG. 2 is reversed left and right, and the projections and depressions 103 and 104 corresponding to the grooves 8 and 9 are formed. Yes. That is, in FIG. 6, the extending direction of the protrusions 103 and 104 corresponds to the extending direction of the grooves 8 and 9. The die casting mold 101 is formed with a gate 102 for pouring molten metal into the cavity. The gate 102 is provided in a direction in which the protrusions 103 and 104 are extended. When the casing 5 is cast by the die casting mold 101, the molten metal injected from the gate 102 into the cavity flows along the protrusions 103 and 104 corresponding to the grooves 8 and 9 (see arrow A in FIG. 6). When the casing 5 having a large number of grooves on the bottom surface is formed by die casting, when the molten metal flows in a direction intersecting the longitudinal direction of the elongated ridges 103 and 104, the elongated ridges 103 and 104 inhibit the flow of the molten metal. When the molten metal flows along the protrusions 103 and 104, the protrusions 103 and 104 do not hinder the flow of the molten metal. The housing 5 having the linear grooves 8 and 9 parallel to each other can be easily manufactured by preparing a die casting mold so that the molten metal flows along the grooves.

  The heat dissipation structure 2 is constituted by the linear groove 8 (9) provided in the region surrounded by the fixing portion 7a (7b) on the housing surface facing the semiconductor module 20 (30). The linear groove 8 (9) is a groove into which the grease G enters and is parallel to each other. Further, between adjacent linear grooves 8 (9), flat surfaces (inter-groove planes 12, 13) wider than the linear groove width are provided. The heat dissipation structure 2 is suitable for a housing in which a member having a coefficient of thermal expansion different from that of the housing is fixed outside the housing with the element module interposed therebetween.

  With reference to FIG. 7, the modification (heat dissipation structure 2a) of the heat dissipation structure 2 is demonstrated. In the heat dissipation structure 2a, the housing 5 has a terrace 115 that is one step higher than the surroundings on the surface on which the semiconductor module 30 is attached. The terrace 115 corresponds to a heat radiating portion, and is provided with parallel grooves 9a to 9e. The semiconductor module 30 is fixed to the upper surface of the terrace 115 with bolts 32. In order to manufacture a terrace by die casting, it is necessary to form a depression corresponding to the terrace in a die-cast type. Further, a protrusion corresponding to the groove 9 is formed in the recess. Molding with a die-casting die having a plurality of protrusions in the recess is relatively difficult, but it is difficult to cause poor hot water flow by matching the direction in which the protrusions (that is, the grooves of the housing) extend with the direction of hot water flow. can do.

  Points to be noted regarding the technology of the embodiment will be described. The semiconductor modules 20 and 30 of the embodiment correspond to an example of an element module. The semiconductor chips 21a, 21b, 21c, and 31 correspond to an example of a heating element. The heating element is not limited to a semiconductor chip, and may be an electronic component such as a resistor, a capacitor, or a coil. That is, the element module is not limited to a package in which a semiconductor chip is molded. The under cover 4 corresponds to an example of a plate member. The bottom of the housing 5 corresponds to an example of a wall of the housing. The bolt fixing holes 7a and 7b correspond to an example of a fixing portion.

  In the example, there were six grooves 8 and five grooves 9. There is no limit to the number of grooves. In the embodiment, the example in which the semiconductor modules 20 and 30 are fixed to the bottom of the housing 5 has been shown. However, the places where the semiconductor modules 20 and 30 (element modules) are fixed are the side surface and the top surface of the housing. Also good. Although the heat dissipation structure 2 in the inverter has been described in the embodiments, the technology disclosed in the present specification can be applied to electronic devices other than the inverter.

  The semiconductor modules 20 and 30 as an example of the element module are packages in which a semiconductor chip is molded with a resin. The element module may be a cooler-integrated type having a coolant channel therein.

  Specific examples of the present invention have been described in detail above, but these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples illustrated above. Further, the technical elements described in the present specification or drawings exhibit technical usefulness alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. Moreover, the technique illustrated in this specification or the drawings achieves a plurality of objects at the same time, and has technical usefulness by achieving one of the objects.

2, 2a: heat dissipation structure 3: inverter 4: under cover 5: housings 6, 22, 32: bolts 7a, 7b: fixing holes 8, 9: grooves (wire grooves)
12, 13: Inter-groove plane 14, 15: Heat radiation part 20, 30: Semiconductor modules 21a, 21b, 21c, 31: Semiconductor chip 32: Bolt 101: Die casting mold 102: Gate 103: Projection 105: Cavity surface 115: Terrace (Heat dissipation part)
G: Grease

Claims (7)

An element module including a heating element;
A casing made of a casting of an electronic device in which the element module is fixed at a plurality of fixing points with the grease interposed therebetween;
A plate member having a coefficient of thermal expansion different from that of the casing, fixed to the casing so as to face the element module across the wall of the casing,
With
The fixed part is provided so as to surround the heating element,
A plurality of parallel linear grooves into which grease enters are provided in a region surrounded by the fixed portion of the housing surface facing the element module, and the width between the adjacent linear grooves is wider than the linear groove width. A heat dissipating structure provided with a flat surface.   The heat dissipation structure according to claim 1, wherein the region where the linear groove is provided is one step higher than the surrounding portion.   The heat dissipation structure according to claim 1 or 2, wherein the surface of the flat surface is smoother than the surface inside the groove of the linear groove.   The heat dissipation structure according to any one of claims 1 to 3, wherein the plurality of linear grooves have a groove interval at the center in the alignment direction of the linear grooves that is narrower than a groove interval at an end in the alignment direction.   The heat dissipation structure according to any one of claims 1 to 4, wherein the linear groove is provided at a position overlapping the heating element when viewed from the stacking direction of the housing and the element module.   The heat dissipation structure according to any one of claims 1 to 5, wherein the casing is made of aluminum die casting, and a direction in which the linear groove extends coincides with a hot water flow direction during casing casting. .   The heat dissipation structure according to any one of claims 1 to 6, wherein the plate member is made of iron.

Images