Patent Application
20070120236
This is a divisional of application Ser. No. 10/911,509 filed Aug. 5, 2004 which claims benefit of and priority to Japanese Patent Application Nos. 2003-287813 and 2003-287814 filed Aug. 6, 2003. The entire disclosure of the prior application, application Ser. No. 10/911,509 is considered part of the disclosure of the accompanying Divisional application and is hereby incorporated by reference.
The present invention relates to a semiconductor device provided with a semiconductor integrated circuit, and in particular, to a semiconductor integrated circuit configured such that while wiring resistance is reduced when disposed on a circuit board, such as a printed circuit board, and so forth, and heat generated therein can be efficiently radiated.
With a conventional semiconductor device, outlets for internal electrodes of a semiconductor integrated circuit, such as a ground electrode or power source electrode, are generally disposed in a peripheral part of the semiconductor integrated circuit, and consequently, it has been necessary to connect internal elements of the semiconductor integrated circuit to the outlets for the electrodes, disposed in the peripheral part of the semiconductor integrated circuit by a very thin metal interconnection made of aluminum or copper, leading from the former, respectively. Further, connection of the outlets for the electrodes of the semiconductor integrated circuit to electrodes of a circuit board, such as a printed circuit board, and so forth, is implemented by bonding the electrodes of the semiconductor integrated circuit to so-called leads made of a copper alloy and so forth, such as metal sheets, bumps, or lands with a wire made of made of gold, aluminum, or copper, or with a bump made of gold, solder, tin, and so forth, respectively, and further, in order to protect the semiconductor integrated circuit, respective junctions of the semiconductor integrated circuit with the leads, bumps, or lands, and the leads, bumps, lands, or so on, from mechanical stress, and so on, these are all encapsulated with a synthetic resin such as epoxy resin, polyimide, and so forth.
On rare occasions, there is also a case where the outlets for the internal electrodes are provided in the vicinity of the center of the semiconductor integrated circuit, and connection to the leads is made with a wire leading from the outlets, respectively.
Thus, with the conventional semiconductor device 1, as it has been necessary to connect the internal electrodes of the semiconductor integrated circuit 10 to the electrode outlet 22 disposed in a peripheral part of the semiconductor integrated circuit 10 with the metal interconnection 20 which is very thin, and also to connect the electrode outlets 22, 24, of the semiconductor integrated circuit 10 to the leads 16, with the wires 18, respectively, a wiring length has become very long, and to that extent, an increase in electrical resistance value has resulted, thereby creating a main factor for deterioration in characteristics of the semiconductor device 1.
Further, with a semiconductor integrated circuit of a construction such that electrode outlets are provided in the vicinity of the center of the semiconductor integrated circuit, wiring resistance can be rendered somewhat lower than that for the semiconductor device 1 of the previously-described construction, however, there is the need for connecting the electrode outlets to the leads with a fine metal line, respectively, and respective lengths of the fine metal lines become longer, so that it has been unavoidable to bring about an increase in electrical resistance value anyway, thereby creating a main factor for deterioration in characteristics of a semiconductor device.
Along with recent increases in degree of integration of the IC chip, there have been further advances toward miniaturization of the semiconductor integrated circuit. As a result, there is a tendency of metal interconnections and fine metal lines becoming increasingly thinner, so that the deterioration in the characteristics, due to the main factor as described, is seen increasingly pronounced.
Among semiconductor devices, there has been known the semiconductor device of a construction in which an IC chip is provided with metal protrusions (metal bumps), and a metal member (metal bar) is mounted on the metal protrusions to thereby secure both together with, for example, a nonconducting adhesive, and so forth, before exposing the end of the metal bar (refer to JP-A 7-66332), which is, however, intended to exclusively dissipate heat, and the metal bar is not connected to the electrodes of the IC chip.
Further, as a result of the increases in the degree of integration of the IC chip, a processing speed thereof has become very fast, and as the degree of integration of the IC chip and the processing speed thereof increase, so does a current amount flowing per unit time, so that there is a tendency of heat quantity of the IC chip increasing.
Upon an increase in heat quantity of the semiconductor integrated circuit, leak current increases, causing not only a problem of deterioration in reliability, and so forth, but also a problem of a gap developed between respective elements of the semiconductor device, due to difference in coefficient of thermal expansion between the respective elements. Such gaps will cause not only a problem of faulty contact, but also a problem that foreign matter, such as moisture, and so forth, makes ingress in the interior from outside, and if heat generation occurs to the semiconductor device in such a state, the foreign matter, such as moisture, and so forth, having made ingress in the interior will undergo expansion, thereby causing even destruction of the semiconductor device.
In addition, with a semiconductor device having a high degree of integration, since there is an increase in the number of input/output electrodes (pads), and the number of power source electrodes, within the semiconductor device, spacing between the electrodes becomes narrower, so that leads become inevitably thinner, resulting in a problem of poor heat radiation characteristics.
Hence, there have thus far been proposed heat radiation means, for example, as described hereinafter.
However, in the case of radiating heat from the back surface side of a semiconductor integrated circuit through the die pad, as described under (1) above, it is the common practice to use an electrically conductive adhesive, insulating adhesive, solder, and so forth, as means for bonding the semiconductor integrated circuit with the die pad. In the case of bonding the semiconductor integrated circuit with the die pad by use of these adhesives, solder, and so forth, it is extremely difficult based on the current fabrication technology to completely eliminate voids contained in the adhesives, or solder, and furthermore, if the semiconductor integrated circuit is bonded with the die pad by use of the adhesives, there is no denying a possibility that exfoliation of the die pad from the semiconductor integrated circuit occurs due to thermal stress developed at the time when the semiconductor device is mounted on a circuit board. For this reason, the means have shortcomings in that heat radiation characteristics of the semiconductor device largely fluctuate, and the characteristics undergo variation. Further, in the case of radiating heat from the back surface side of the conventional semiconductor integrated circuit through the die pad, a heat radiation path tends to become longer, so that there has been a tendency of thermal resistance between junction cases becoming higher. Hence, even if the semiconductor device as a whole meets a permissible loss against heat generation, there exists a risk of the semiconductor device undergoing thermal destruction due to localized heat generation of the semiconductor integrated circuit.
Further, with the heat radiation means whereby the die pad is connected to the inner leads, and the heat radiation sheet is bonded to the inner leads connected to the die pad through the intermediary of the insulation layer to thereby radiate heat of the printed board as described under (2) above, and with the heat radiation means whereby the die pad is bonded to all the leads with the tape-like adhesive, and heat is radiated to the printed board through the leads as described under (3) above, there is a tendency that a heat radiation path becomes longer than that in the case of (1) above, thereby causing a problem of an increase in thermal resistance.
In the case of (4) above, a construction is adopted such that in order to radiate heat generated in the IC chip to the outside at the shortest distance from the metal protrusions through the respective metal members, the IC chip is provided with the metal protrusions (metal bumps), on which the metal member (metal bar) is mounted to secured both together with, for example, a nonconducting adhesive, and so forth, so that the construction is complex, and consequently, fabrication becomes complicated, resulting in high cost.
The invention has been developed to resolve the above-described problems with the conventional semiconductor device, and it is a first object of the invention to significantly reduce wiring resistance from elements inside a semiconductor integrated circuit of a semiconductor device up to external terminals of a printed board, and so forth, thereby checking deterioration in characteristics of the semiconductor device to the minimum.
A second object of the invention is to minimize the length of a heat radiation path from the semiconductor integrated circuit, thereby significantly reducing thermal resistance between junction cases.
A third object of the invention is to preclude deterioration in heat radiation characteristics, due to variation in condition of bonding between the semiconductor integrated circuit, and a die pad.
A fourth object of the invention is to enhance resistance to thermal destruction due to localized heat generation occurring inside the semiconductor integrated circuit.
In accordance with a first aspect of the invention, there is provided a semiconductor device encapsulated with a resin, comprising a semiconductor integrated circuit, and conduction means for connecting electrode terminals of the semiconductor integrated circuit to electrodes of a board, respectively, said semiconductor device further comprising a protective film, and a metal film, deposited in that order over the semiconductor integrated circuit, wherein the metal film is exposed from the resin for encapsulation on the top surface side or the back surface of the semiconductor device.
The invention provides in its second aspect a semiconductor device encapsulated with a resin, comprising a semiconductor integrated circuit, and conduction means for connecting electrode terminals of the semiconductor integrated circuit to electrodes of a board, respectively, said semiconductor device further comprising a protective film, and a metal film, deposited in that order over the semiconductor integrated circuit, wherein the metal film is connected to internal electrodes of the semiconductor integrated circuit through openings provided in the protective film, and is exposed from the resin for encapsulation on the top surface side or the back surface of the semiconductor device.
With the semiconductor device having those features described, the metal film is preferably provided with a stress relief film.
Further, with the semiconductor device as described above, the metal film may comprise first and second metal films, the first and second metal films being connected with each other via at least one spot, with the stress relief film interposed therebetween, and the second metal film may be exposed from the resin for encapsulation on the top surface side or the back surface of the semiconductor device.
Still further, the semiconductor device described in the foregoing may further comprise a metal sheet bonded to the first metal film, and the metal sheet may be exposed from the resin for encapsulation on the top surface side or the back surface of the semiconductor device.
Yet further, the semiconductor device described above may further comprise a metal sheet bonded to the second metal film, and the metal sheet may be exposed from the resin for encapsulation on the top surface side or the back surface of the semiconductor device.
Further, the first and second metal films are preferably made of gold, aluminum, copper, or an alloy composed of these elements as main constituents, respectively, and the stress relief film may be made of an elastomer or a plastomer, such as a polyimide, an epoxy resin, and so forth.
Still further, the semiconductor device described above comprises a die pad with the semiconductor integrated circuit mounted thereon, and the die pad may be exposed from the resin for encapsulation on the top surface side or the back surface of the semiconductor device.
Yet further, the surface of the metal film or the metal sheet, made of an element other than gold, that is exposed from the resin for encapsulation on the top surface side or the back surface of the semiconductor device, preferably has a gold plating.
The present invention has the following advantages:
That is, by minimizing the length of the heat radiation path from the semiconductor integrated circuit, thermal resistance between the junction cases can be significantly reduced.
Embodiments of the invention are described hereinafter with reference to the accompanying drawings.
Now, with the present embodiment, an electrode outlet 32 for taking out at least either a ground line or a power supply line of the semiconductor integrated circuit, is provided at one spot or a plurality of spots in optional locations of the active surface of the semiconductor integrated circuit 10, in addition to the electrode outlets 22, 24, as for the conventional case, and portions of the protective film 26, corresponding thereto, are removed.
Over portions of the protective film 26, excluding openings of the protective film 26, other than the electrode outlet 32 for connection with external terminals of the semiconductor integrated circuit 10, a metal film 30 made of gold, aluminum, or copper, or an alloy composed of these, as main constituents, is deposited by a vapor deposition method or a plating method. The metal film to be formed preferably corresponds in size to approximately 60 to 80% of a region of the protective film 26, excluding the openings of the protective film 26, other than the electrode outlet 32 for connection with the external terminals of the semiconductor integrated circuit. By so doing, either the ground line or the power supply line of the semiconductor integrated circuit is bonded to the metal film 30 formed over the protective film 26.
The metal film 30 is exposed from the epoxy resin 28 covering the semiconductor device 1, and by connecting the metal film 30 as exposed with electrodes (not shown) of a printed board, connection to an electrode (a power supply electrode, or ground electrode) of the semiconductor integrated circuit 10 can be implemented without use of a long metal interconnection as required in the conventional case. Furthermore, heat generated in the semiconductor integrated circuit 10 can be radiated to the outside via the metal film 30. That is, the metal film 30 is exposed from the epoxy resin 28 covering the semiconductor integrated circuit 10, and, through the intermediary of the metal film 30 as exposed, the heat generated in the semiconductor integrated circuit 10 can be radiated to an enclosure, and so forth, of electronic equipment bonded to the semiconductor integrated circuit 10, or into the atmosphere.
Furthermore, because the stress relief film 34 is provided, it is possible to prevent occurrence of problems such that repetition in heating and cooling of the semiconductor device 1 when the same is in operation, and out of operation will cause exfoliation to occurs to joined parts due to difference in coefficient of thermal expansion between respective elements inside the semiconductor device 1, resulting in breakage of the semiconductor device 1 or faulty connections, and so forth.
With the adoption of such a configuration as described, as with the case of the first embodiment, internal electrodes of the semiconductor integrated circuit 10 can be connected to a power supply line, or a ground line, without use of a long metal interconnection as required in the conventional case.
Because the metal sheet 40 functions as a heat sink, radiation of heat generated in the semiconductor integrated circuit 10 can be further promoted. In this case, the metal film 30 is preferably bonded to the metal sheet 40 by gold-tin bonding or by high-temperature soldering, and further, the exposed surface of the metal sheet 40 is preferably plated with gold if the metal sheet 40 is made of an element other than gold, or with solder, or tin. With such a configuration as described heat can be not only temporarily accumulated in the metal sheet 40 owing to thermal capacity thereof, but also radiated from the surface thereof to the outside, so that heat radiation can be effected more efficiently.
More specifically, the semiconductor device according to the fourth embodiment is constructed such that a stress relief film 34 made of polyimide, and so forth is further provided over a metal film 30a formed over a protective film 26, a metal film 30b made of, for example, gold, aluminum, copper, or an alloy composed of these elements as main constituents is deposited over the stress relief film 34 by the vapor deposition method or the plating method, and so forth, and, further, there is disposed a metal sheet 40 over the metal film 30b. In this case as well, the metal film 30a in the lower layer is connected to the metal film 30b in the upper layer via at least one spot.
Accordingly, the semiconductor device 1 according to the present embodiment has the operation effects of the second embodiment in combination with those of the third embodiment. That is, by connecting the semiconductor integrated circuit 10 to a power supply line, or a ground line, without use of a long metal interconnection as required in the conventional case, not only radiation of heat from the semiconductor integrated circuit 10 can be further promoted through the metal sheet 40 functioning as the heat sink, but also thermal stress occurring to the metal sheet 40, due to heat generation in semiconductor, can be relieved by the stress relief film 34, so that exfoliation at junction parts, and formation of gaps can be prevented with reliability, thereby enabling the semiconductor device 1 to perform stable operation all the time without undergoing breakage.
With such a construction as described, since the metal sheet 40 is directly connected to a printed circuit board, wiring resistance can be further reduced, and further, with the construction described, as the metal sheet 40 is in direct contact with the printed circuit board upon mounting the semiconductor integrated circuit thereon, heat generated in the semiconductor integrated circuit 10 can be radiated directly to the printed board through the intermediary of the metal sheet 40 in addition to the heat radiation efficiency of the fifth embodiment, and as the die pad 12 is exposed from an epoxy resin for encapsulation, the heat generated in the semiconductor integrated circuit 10 can be radiated from the die pad 12 as well to the outside through an enclosure, and so forth, of electronic equipment, bonded to the die pad 12. Hence, with the configuration described, efficient heat radiation can be effected.
With the construction described as well, because a metal sheet is directly connected to a printed circuit board, the metal sheet can be connected to electrodes of the circuit board by way of a still shorter distance, and to that extent, resistance can be reduced, and at the same time, heat generated in the semiconductor integrated circuit 10 can be radiated to the printed circuit board through the metal sheet 40. Other operation effects of the present embodiment are the same as those of the semiconductor device 1 described with reference to
FIGS. 9 to 16 are schematic sectional views of ninth to sixteenth embodiments of a semiconductor device according to the invention, respectively. The ninth to sixteenth embodiments are the same in construction as the first to eighth embodiments, respectively, except for the electrode outlets 22, and 32 that are provided in the first to eighth embodiments, respectively, and the operation effects of the former are the same as those of the latter, respectively, omitting therefore detailed description thereof.
With the respective embodiments described in the foregoing, if the metal film 30 or the metal sheet 40 is made of material other than gold, the exposed surface of the metal film 30 or the metal sheet 40 is preferably plated with gold, solder, or tin in order to protect the interior of the semiconductor device 1 to thereby implement prevention of corrosion thereof, and so forth.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2003-287813 | Aug 2003 | JP | national |
| 2003-287814 | Aug 2003 | JP | national |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 10911509 | Aug 2004 | US |
| Child | 11468693 | Aug 2006 | US |
