Patent Application
20130049186
1. Field of the Invention
The present invention relates to a semiconductor device used, e.g., for high power control, and a method of manufacture thereof.
2. Background Art
Japanese Laid-Open Patent Publication No. 2006-100327 discloses a semiconductor device in which a semiconductor module formed by encapsulating a semiconductor element with resin is secured to a cooling fin (or cooling body) by means of screws. Japanese Laid-Open Patent Publication No. 2001-250890 also discloses related art.
In order to reduce the number of parts in such a semiconductor device, it is desirable to secure the semiconductor module to the cooling body without using screws or the like. To accomplish this, the semiconductor module must be secured to the cooling body by way of some adhesive or bonding material which is disposed therebetween. It should be noted that such material must have substantial heat conductivity, as well as providing substantial bonding strength. It has been found, however, that the use of a material suitable for securing the semiconductor module to the cooling body may result in insufficient cooling of the semiconductor module. On the other hand, the use of a material suitable for cooling the semiconductor module may result in inadequate securing of the semiconductor module to the cooling body.
The present invention has been made to solve the above problems. It is, therefore, an object of the present invention to provide a semiconductor device which has a reduced number of parts, yet in which the semiconductor module is attached to a cooling body with substantial bonding strength and cooled adequately. Another object of the present invention is to provide a method of manufacturing such a semiconductor device. The features and advantages of the present invention may be summarized as follows.
According to one aspect of the present invention, a semiconductor device includes a semiconductor module having a heat conductive portion formed of metal and also having a molded resin having a surface at which the heat conductive portion is exposed, a cooling body secured to the semiconductor module by means of bonding material, and heat conductive material formed between and thermally coupling the heat conductive portion and the cooling body.
According to another aspect of the present invention, a method of manufacturing a semiconductor device, includes the steps of forming heat conductive material on a surface of a cooling body, forming bonding material on the surface of the cooling body, the bonding material having a projection, forming a resin groove in a molded resin of a semiconductor module having a heat conductive portion which is formed of metal and which is exposed at a surface of the molded resin, and integrally securing the cooling body and the semiconductor module together in such a manner that the projection is in contact with an inner wall of the resin groove, and that the heat conductive portion overlaps and is in contact with the heat conductive material.
Other and further objects, features and advantages of the invention will appear more fully from the following description.
The following description will be directed to components between the semiconductor module 14 and the cooling body 12. A bonding material 20 and a heat conductive material 22 are formed between the semiconductor module 14 and the cooling body 12. The bonding material 20 secures the molded resin 18 of the semiconductor module 14 to the cooling body 12. The bonding material 20 is formed of insulating material. The heat conductive material 22 is formed between and thermally couples the heat conductive portion 16 and the cooling body 12. The heat conductive material 22 is formed of electrically conductive material having excellent heat conductivity.
In the semiconductor device of the first embodiment, the semiconductor module 14 is secured to the cooling body 12 by means of the bonding material 20, which is suitable for that purpose, making it possible to attach the semiconductor module 14 to the cooling body 12 with substantial bonding strength. Further, the heat conductive portion 16 is thermally coupled to the cooling body 12 by way of the heat conductive material 22, which is suitable for cooling the semiconductor module 14, making it possible to adequately cool the semiconductor module 14. Further, the semiconductor device 10 has a reduced number of parts, since the semiconductor module 14 is secured to the cooling body 12 without using screws or the like. Thus, although the semiconductor device of the first embodiment has a reduced number of parts, the semiconductor module 14 is attached to the cooling body 12 with substantial bonding strength and cooled adequately.
As is known in the art, materials having higher electrical conductivity have higher heat conductivity. In the semiconductor device of the first embodiment, the heat conductive material 22 is formed of electrically conductive material having excellent heat conductivity, and hence is expected to provide good heat conduction. Furthermore, the heat conductive portion 16 and the heat conductive material 22 are separated from the outside by the bonding material 20, which is formed of insulating material, thereby insulating the heat conductive material 22 from the outside atmosphere. Insulating a semiconductor module from the outside atmosphere is an effective way to maintain the characteristics of the semiconductor module, especially if the module includes a power semiconductor device driven by a high voltage.
Various other alterations may be made to the first embodiment without departing from the features of the present invention. For example, the bonding material 20 may be formed of material other than insulating material. Further, although in the first embodiment the heat conductive material 22 is formed of electrically conductive material, it is to be understood that in other embodiments it may be formed of, e.g., silicone grease. When the heat conductive material 22 is formed of an insulating material such as silicone grease, it is easier to insulate the semiconductor module 14. Further, the semiconductor element and the heat conductive portion 16 within the molded resin 18 may be insulated from each other by insulating material in order to ensure the insulation of the semiconductor module.
The following description of a semiconductor device in accordance with a second embodiment of the present invention will be primarily limited to the differences from the semiconductor device of the first embodiment in order to avoid undue repetition.
As described above in connection with the first embodiment, the heat conductive material 22 serves to cool the semiconductor module 14, and the bonding material 30 serves to bond the semiconductor module 14 to the cooling body 12. Thus, the heat conductive material 22 and the bonding material 30 have different functions. Therefore, mixing or bringing into contact these materials may prevent them from functioning properly. In the semiconductor device of the second embodiment, the heat conductive material 22 and the bonding material 30 are prevented from being mixed or brought into contact with each other, since they are separated from each other by the cooling body groove 12a.
The following description of a semiconductor device in accordance with a third embodiment of the present invention will be primarily limited to the differences from the semiconductor device of the first embodiment in order to avoid undue repetition.
In the semiconductor device of the third embodiment, since the bonding material 40 extends to cover the side surfaces 18a of the molded resin 18, the bonding strength of the bonding material 40 between the semiconductor module 14 and the cooling body 12 is increased. Further, since the surface of the heat conductive portion 16 in contact with the heat conductive material 22 and the bottom surface 18b of the molded resin 18 form a single plane, the gap between the bottom surface 18b and the cooling body 12 is narrowed, making it easier to form the bonding material 40, which extends to cover the side surfaces 18a of the molded resin 18.
The following description of a semiconductor device in accordance with a fourth embodiment of the present invention will be primarily limited to the differences from the semiconductor device of the first embodiment in order to avoid undue repetition.
The following description of a semiconductor device and a method of manufacture thereof in accordance with a fifth embodiment of the present invention will be primarily limited to the differences from the semiconductor device of the first embodiment in order to avoid undue repetition.
The method of manufacturing a semiconductor device in accordance with the fifth embodiment will now be described.
Next, the cooling body 12 and the semiconductor module 14 are integrally secured together. In this process step, the cooling body 12 and the semiconductor module 14 are integrally secured together in such a manner that the projection 70a is in contact with inner walls of the resin groove 18d, and that the heat conductive portion 16 overlaps and is in contact with the heat conductive material 22. At that time, the cooling body 12 and the semiconductor module 14 are aligned with each other by inserting the projection 70a into the resin groove 18d.
In the semiconductor device manufacturing method of the fifth embodiment, the cooling body 12 and the semiconductor module 14 are integrally secured together using the projection 70a as an alignment guide, making it possible to increase the accuracy of alignment of the components in the semiconductor device. Further, since the projection 70a is in contact with inner walls of the resin groove 18d, the bonding strength between the semiconductor module 14 and the cooling body 12 is increased. Further, since the bonding material 70 is spaced apart from the heat conductive material 22, even if a portion of the bonding material 70 diffuses toward the heat conductive material 22, that portion is retained or trapped in the resin groove 18d, thereby preventing the bonding material 70 from reaching and mixing with the heat conductive material 22.
The semiconductor device manufacturing method of the fifth embodiment is characterized in that the cooling body 12 and the semiconductor module 14 are aligned with each other using the projection 70a when integrally securing them together, and that the projection 70a is brought into bonding engagement with the resin groove 18d in order to increase the bonding strength between the semiconductor module 14 and the cooling body 12. It should be noted that the bonding material 70 need not necessarily be formed at a distance from the heat conductive material 22.
The semiconductor devices described in connection with the second and subsequent embodiments are susceptible of alterations at least similar to those that can be made to the semiconductor device of the first embodiment. Further, features of different embodiments may be combined where appropriate.
In accordance with the present invention, both bonding material and heat conductive material are formed between the semiconductor module and the cooling body in a semiconductor device, making it possible to attach the semiconductor module to the cooling body with substantial bonding strength and adequately cool the semiconductor module while reducing the number of parts in the semiconductor device.
Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.
The entire disclosure of a Japanese Patent Application No. 2011-184800, filed on Aug. 26, 2011 including specification, claims, drawings and summary, on which the Convention priority of the present application is based, are incorporated herein by reference in its entirety.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2011-184800 | Aug 2011 | JP | national |
