The embodiment described herein relates to a power module and a fabrication method for such a power module.
Conventionally, there have been known power modules in which a power chip including a semiconductor device such as Insulated Gate Bipolar Transistor (IGBT) is mounted on a leadframe therein, and of which the whole system thereof is molded with resin. Since such a semiconductor device produces heat during an operating state, it is common to dispose a heat sink via an insulating layer on a back side surface of the leadframe in order to cool the semiconductor device.
In conventional power modules, an insulating layer and a leadframe (metal layer) are contacted with each other on a flat surface. If external force is applied thereon in such a state where the insulating layer and the metal layer are contacted with each other on the flat surface, the insulating layer and the metal layer may be deviated (displaced) from each other, thereby causing insulation failure. Moreover, if the insulating layer and the metal layer are deviated from each other and thereby a gap is formed therebetween, a thermal resistance of the module may be increased. Thereby, since it becomes impossible to cool the semiconductor device as designed, there will be generated thermal run away of the semiconductor device, thermal deterioration of bonding layers, e.g. a solder layer, and fusing of bonding wires.
The embodiment provides: a power module with improved reliability so that an insulating layer and a metal layer may be hardly deviated from each other even if external force is applied thereon; and a fabrication method for such a power module.
According to one aspect of the embodiment, there is provided a power module comprising: an insulating layer; a metal layer disposed on the insulating layer; a semiconductor chip disposed on the metal layer; and a mold resin formed so as to cover the semiconductor chip and at least a part of the metal layer, wherein a groove into which apart of the insulating layer is inserted is formed on a surface of the metal layer facing the insulating layer.
According to another aspect of the embodiment, there is provided a fabrication method for a power module comprising: forming a groove on a bottom surface of a leadframe; bonding a semiconductor chip to the leadframe with a conductive bonding material; electrically connecting the semiconductor chip and the leadframe to each other using a connecting member; disposing the leadframe on a metallic mold and then forming an insulating layer on a bottom surface of the leadframe, the insulating layer formed so as to be inserted into the bottom surface of the leadframe; and after curing the insulating layer, closing the metallic mold, and then pouring a mold resin therein in order to mold the leadframe, the conductive bonding material, the semiconductor chip, and the connecting member.
According to still another aspect of the embodiment, there is provided a fabrication method for a power module comprising: forming a groove on a bottom surface of a leadframe; bonding a semiconductor chip to the leadframe with a conductive bonding material; electrically connecting the semiconductor chip and the leadframe to each other using a connecting member; disposing the leadframe on a metallic mold and then forming an insulating layer on a bottom surface of the leadframe; and after curing the insulating layer, closing the metallic mold, and then pouring a mold resin therein in order to mold the leadframe, the conductive bonding material, the semiconductor chip, and the connecting member, wherein the step of forming the insulating layer on the bottom surface of the leadframe comprises forming so that a surface of the mold resin and a surface of the leadframe are flush with each other at a corner portion of the leadframe, and then forming the insulating layer on the surface of the mold resin and the surface of the leadframe which are flush with each other.
According to the embodiment, there can be provided a power module with improved reliability so that the insulating layer and the metal layer may be hardly deviated from each other even if external force is applied thereon; and a fabrication method for such a power module.
Next, a certain embodiment will be described with reference to drawings. In the description of the following drawings, the identical or similar reference numeral is attached to the identical or similar part. However, it should be noted that the drawings are schematic and the relation between thickness and the plane size and the ratio of the thickness of each component part differs from an actual thing. Therefore, detailed thickness and size should be determined in consideration of the following explanation. Of course, the part from which the relation and ratio of a mutual size differ also in mutually drawings is included.
Moreover, the embodiment described hereinafter merely exemplifies the device and method for materializing the technical idea; and the embodiment does not specify the material, shape, structure, placement, etc. of each component part as the following. The embodiment may be changed without departing from the spirit or scope of claims.
(Comparative Example)
A schematic cross-sectional structure of a power module 20a according to a comparative example is illustrated as shown in
A schematic cross-sectional structure of another power module 20b according to the comparative example is illustrated as shown in
A schematic cross-sectional structure showing a usage example of the power module 20a shown in
In this case, in the power modules 20a and 20b according to the comparative example, the insulating layer 7 and the leadframes (metal layers) 1, 5 are contacted with each other on a flat surface. If external force is applied thereon in such a state where the insulating layer 7 and the metal layers 1, 5 are contacted with each other on a flat surface, the insulating layer 7 and the metal layers 1, 5 may be deviated (displaced) from each other, thereby causing insulation failure. Moreover, if the insulating layer 7 and the metal layers 1, 5 are deviated from each other and thereby a gap is formed therebetween, a thermal resistance of the power module (20a, 20b) may be increased. Thereby, since it becomes impossible to cool the semiconductor device as designed, there will be generated thermal run away of the semiconductor device, thermal deterioration of bonding layers, e.g. a solder 2, and fusing of the aluminum wire 4.
Since the thermal compound 9 is liquid, time and effort are required in work for coating. Moreover, the thermal compound 9 is also hardly treated since it is necessary to be coated uniformly and thinly. Furthermore, the whole of the power module (20a, 20b) becomes deformed by warping and restoring in a repetition of cooling and heating due to operating environments, and thereby the liquid thermal compound 9 may be gradually pushed out (pumped out) therefrom. If the thermal compound 9 is pumped out therefrom, a gap may be generated between a bottom surface of the power module (20a, 20b) and the heat sink 10, and thereby a thermal resistance of the portion where the gap is generated will be increased. As a result, since the semiconductor device cannot fully be cooled, it becomes a cause of the thermal run away of the semiconductor device, the thermal deterioration of bonding layers, e.g. a solder 2, and the fusing of the aluminum wire 4 as previously explained.
(Embodiment)
As shown in
In the embodiment, the groove 11 may also be formed outside a region to which a heat generated from the semiconductor chip 3 is conducted.
Moreover, an angle between the semiconductor chip 3 and the groove 11 may be equal to or less than 45 degrees.
Moreover, the groove 11 may be formed only outside the region to which the heat generated from the semiconductor chip 3 is conducted.
Moreover, a cross-sectional shape of the groove 11 may be at least one shape selected from the group consist of a rectangle shape, a semicircle shape, a semi-ellipse shape, triangular shape, and a wedge shape.
Moreover, the groove 11 may be formed along in one direction or may be formed in a lattice-like shape.
Moreover, a surface roughening process may be applied on a surface of the leadframes 1, 5 facing the insulating layer 7.
Moreover, the insulating layer 7 may be formed of a material(s) softer than the leadframes 1, 5.
Moreover, a hardness of the insulating layer 7 may be softer than A40 in durometer hardness.
Moreover, the insulating layer 7 may be formed of an organic material(s).
Moreover, the insulating layer 7 may be formed of a silicone based resin(s).
Moreover, the insulating layer 7 may be filled up with a high thermally-conductive filler.
Moreover, the filler may be at least one selected from the group consist of aluminium oxide, silicon oxide, aluminum nitride, silicon nitride, boron nitride, beryllia, and magnesia.
Moreover, the insulating layer 7 may be formed before the semiconductor chip 3 is molded with a mold resin 6.
Moreover, an edge part of the insulating layer 7 may be intervened between the mold resin 6 and the leadframes 1, 5.
Moreover, the insulating layer 7 may be formed after the semiconductor chip 3 is molded with the mold resin 6.
Moreover, the mold resin 6 and the leadframes 1, 5 may be formed so as to be flush with each other.
(Power Module)
Hereinafter, there will now be explained a configuration of the power module 20 according to the embodiment in more detail, with reference to
A flexible resin (organic material) is used for the insulating layer 7. The flexible resin is preferably a material(s) softer than the leadframes 1, 5, and is also preferably a resin softer than A40 in durometer hardness (e.g., silicone resin, etc.). Moreover, the resin used for the insulating layer 7 is filled up with a high thermally-conductive filler of approximately 1 to 20 W/mK degrees, for example. As such a filler, aluminium oxide, silicon oxide, aluminum nitride, silicon nitride, boron nitride, beryllia, magnesia, etc. can be used.
Thus, since the insulating layer 7 is tightly insert in the groove 11 by using the flexible resin for the insulating layer 7, the insulating layer 7 can be strongly bonded to the leadframes 1 and 5 without increasing the thermal resistance (anchor effect). Moreover, since the insulating layer 7 is sufficiently compatible with the surface of the heat sink 10 due to the flexibility thereof, it becomes unnecessary to coat the liquid thermal compound 9 between the bottom surface of the power module 20 and the heat sink 10 as in the case of the comparative example.
As shown in the principal part B in
(Usage Example)
A schematic planar structure showing a usage example of the power module 20 according to the embodiment is illustrated as shown in
(Formed Direction of Groove)
A schematic cross-sectional structure taken in the line I-I shown in
Another schematic cross-sectional structure taken in the line I-I shown in
Still another schematic cross-sectional structure taken in the line I-I shown in
Although the case where the groove 11 is formed in a vertical or direction, or in a lattice-like shape has been exemplified herein, the formed direction of the groove 11 is not limited to the above-mentioned examples. For example, the groove 11 may be obliquely formed in one direction with respect to the semiconductor chip 3, or may be obliquely formed in a lattice-like shape.
(Cross-Sectional Shape of Groove)
An enlarged schematic cross-sectional structure showing a part of the leadframe 5 in the power module 20 according to the embodiment is illustrated as shown in
Another enlarged schematic cross-sectional structure showing a part of the leadframe 5 in the power module 20 according to the embodiment is illustrated as shown in
Yet another enlarged schematic cross-sectional structure showing a part of the leadframe 5 in the power module 20 according to the embodiment is illustrated as shown in
Yet another enlarged schematic cross-sectional structure showing a part of the leadframe 5 in the power module 20 according to the embodiment is illustrated as shown in
Yet another enlarged schematic cross-sectional structure showing a part of the leadframe 5 in the power module 20 according to the embodiment is illustrated as shown in
In the embodiment, although there have been exemplified the case where the respective grooves 12-15 are formed in a rectangle shape, a semicircle shape, a semi-ellipse shape, a triangular shape, and a wedge shape, and the case where the groove 16 is formed by applying the surface roughening process, these cases may be combined with one another. Although not specifically mentioned in the embodiment, the grooves 12-16 are, of course, formed outside a region extended in downward direction by only the angle C from the bottom head of the solder 2, as shown in the principal part B in
(Fabrication Method 1)
A process showing a fabrication method of the power module 20 according to the embodiment is illustrated as shown in
Firstly, the groove 11 is formed in the bottom surface of the leadframes 1, 5 formed of Cu, AL, or an alloy thereof, as shown in
Next, as shown in
Next, as shown in
Next, as shown in
Finally, after curing the insulating layer 7, the metallic mold is closed, and then the mold resin 6 is poured therein in order to mold the leadframe 1, the solder 2, the semiconductor chip 3, the aluminum wire 4, and the leadframe 5, as shown in
According to such a fabrication method, an edge part of the insulating layer 7 is intervened between the mold resin 6 and the leadframes 1, 5. Accordingly, a possibility of short-circuiting at the corner portion P of the leadframes 1, 5 can be reduced.
(Fabrication Method 2)
A process showing another fabrication method of the power module 20 according to the embodiment is illustrated as shown in
The respective processes of
As mentioned above, the power module 20 according to the embodiment is a resin-sealed semiconductor module having a vertical structure of the semiconductor chip/the metal layer/the insulating layer. In such a structure, the groove 11 into which a part of the insulating layer 7 is inserted is formed in the surface of the metal layers 1, 5 facing the insulating layer 7. Thereby, even if external force is applied thereon, since the bonding strength between the insulating layer 7 and the metal layers 1, 5 is improved, the insulating layer 7 and the metal layers 1, 5 are hardly deviated from each other, thereby preventing inferior insulation. Moreover, since the insulating layer 7 and the metal layers 1, 5 are hardly deviated from each other and thereby a gap is hardly formed therebetween, a thermal resistance of the power module (20a, 20b) is hardly increased. Accordingly, since it becomes possible to cool the semiconductor device as designed, there are hardly generated thermal run away of the semiconductor device, thermal deterioration of bonding layers, e.g. a solder 2, and fusing of the aluminum wire 4, thereby improving the reliability thereof. Moreover, since the groove 11 is arranged in consideration of spreading of heat so that conduction of the heat generated from the semiconductor chip 3 may be hardly obstructed by the groove 11, the cooling capability is not inhibited. In addition, since the flexible resin is used for the insulating layer 7, the liquid thermal compound 9 becomes unnecessary, and therefore it becomes possible to provide the power module 20 easy to handle.
(Examples of Module)
Hereinafter, there will now be explained examples of the power module 20 according to the embodiment. Needless to say, the groove 11 can be formed also in the leadframes 1, 5 of the power module 20 explained below. A formed direction, a cross-sectional shape, and other details configuration of the groove 11 are the same as described above.
The power module 20 according to the embodiment has a configuration of 1-in-1 module. More specifically, one MOSFETQ is included in one module. As an example, five chips (MOS transistor×5) can be mounted thereon, and a maximum of five pieces of the MOSFETs respectively can be connected to one another in parallel. Note that it is also possible to mount a part of five pieces of the chips for the diode DI thereon.
The diode DI connected to the MOSFETQ inversely in parallel is shown in
More particularly, as shown in
Moreover,
(Configuration Example of Semiconductor Device)
As shown in
In
Moreover, a GaN based FET etc. instead of SiC MOSFET are also applicable to the semiconductor device 100 (Q) applied to the power module 20 according to the embodiment.
Any one of an SiC based power device, a GaN based power device, and an AlN based power device is applicable to the semiconductor device 100 applied to the power module 20 according to the embodiment.
Furthermore, a semiconductor of which the bandgap energy is from 1.1 eV to 8 eV, for example, can be used for the semiconductor device 100 applied to the power module 20 according to the embodiment.
Moreover, as shown in
Furthermore, as shown in
In the power module 20 according to the embodiment,
(Application Examples for Applying Power Module)
Next, there will now be explained a three-phase AC inverter 40 composed by using the power module 20 according to the embodiment with reference to
As shown in
In the power module unit 52, the SiC MOSFETs Q1, Q4, and Q2, Q5, and Q3, Q6 having inverter configurations are connected between a positive terminal (+) and a negative terminal (−) to which the converter 48 in a storage battery (E) 46 is connected. Furthermore, diodes D1-D6 are connected inversely in parallel to one another between the source and the drain of the SiC-MOSFETs Q1 to Q6.
Although the structure of the single phase inverter corresponding to U phase portion of
The power module according to the embodiment can be formed as any one of 1-in-1, 2-in-1, 4-in-1, or 6-in-1 module.
As explained above, according to the embodiment, there can be provided the power module with improved reliability so that the insulating layer and the metal layer may be hardly deviated from each other even if external force is applied thereon; and the fabrication method for such a power module.
[Other Embodiments]
As explained above, the embodiment has been described, as a disclosure including associated description and drawings to be construed as illustrative, not restrictive. This disclosure makes clear a variety of alternative embodiment, working examples, and operational techniques for those skilled in the art.
Such being the case, the embodiment covers a variety of embodiments, whether described or not.
Although the insulating layer 7 is formed also between the leadframes 1 and 5 in
The power module according to the embodiment can be used for semiconductor modules, e.g. IGBT modules, diode modules, MOS modules (Si, SiC, GaN), etc. The power module according to the embodiment can also be used for structures which do not use insulating substrates, e.g. Direct Copper Bond (DBC) in case type modules.
Number | Date | Country | Kind |
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2013-151685 | Jul 2013 | JP | national |
This is a continuation application (CA) of PCT Application No. PCT/JP2014/068978, filed on Jul. 17, 2014, which claims priority to Japan Patent Application No. P2013-151685 filed on Jul. 22, 2013 and is based upon and claims the benefit of priority from prior Japanese Patent Applications P2013-151685 filed on Jul. 22, 2013 and PCT Application No. PCT/JP2014/068978, filed on Jul. 17, 2014, the entire contents of each of which are incorporated herein by reference.
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Number | Date | Country | |
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Parent | PCT/JP2014/068978 | Jul 2014 | US |
Child | 15003156 | US |