Package with heat transfer

A semiconductor package includes an encapsulant, a semiconductor device within the encapsulant, and one or more terminals for electrically coupling the semiconductor device to a node exterior to the package. The package further includes bonding means coupling the semiconductor device to the one or more terminals. The semiconductor package is configured to dissipate heat through a top surface of the package. To directly dissipate heat via the top surface of the package, a thermally conductive layer is coupled to the semiconductor device, and the layer is exposed at a surface of the package.

FIELD OF THE INVENTION

The present invention is in the field of semiconductor packaging and is more specifically directed to semiconductor packaging with heat transfer.

BACKGROUND

Modern semiconductor packages continue to become smaller due to improvements in fabrication technology. These smaller packages are more densely packed with circuitry and components that often run much faster than their predecessors. These improvements typically increase the amount of heat generated within the package, while reducing the amount of exterior surface area available for the dissipation of heat. The factors of small size and high speed circuitry contribute to certain undesirable conditions for the operation of modern packages. For instance, semiconductor performance and reliability are directly related to the operating temperature interior and exterior to the package, and thus performance and reliability are also related to the ability to dissipate heat from the package.

Conventionally, heat reduction is achieved by the inclusion of additional interior and/or exterior heat sinks that undesirably affect the overall form factor of the package. However, as the semiconductor packages decrease in size, as well as the devices that use the circuitry and components within the semiconductor packages, the interior space within the package, or the exterior space for the placement of the package, or both, are often heavily constrained. For example, in small form factor applications, such as mobile technology, the overall form factor of a mobile device is so small that there are both profile or height constraints, as well as board surface area constraints, for the onboard electronics.

SUMMARY OF THE DISCLOSURE

A semiconductor package includes an encapsulant, a semiconductor device within the encapsulant, and one or more terminals for electrically coupling the semiconductor device to a node exterior to the package. The package further includes bonding means coupling the semiconductor device to the one or more terminals. The semiconductor package is configured to dissipate heat through a top surface of the package. To directly dissipate heat via the top surface of the package, in some embodiments a portion of the semiconductor device is exposed at the top surface of the package. In some embodiments, a portion of the one or more of the terminals exposed at a surface of the package.

In some embodiments, instead of having the semiconductor device directly exposed at a surface of the package, a thermal cushion is coupled to the semiconductor device. The thermal cushion can be formed by using a thermally conductive, electrically insulating epoxy, or by using a thermally and electrically conductive epoxy. A molding compound encapsulates the semiconductor device.

In some embodiments, the epoxy is exposed at an exterior of the package, and is preferably of the thermally conductive type. In some packages, the epoxy has a width dimension that approximates the dimensions of a surface of the package. Alternatively, the epoxy has a width dimension that is less than the dimensions of a surface of the packager such as, for instance, the width of the semiconductor device.

Alternatively, or in conjunction with the thermal epoxy, the package of some embodiments includes a cap structure coupled to the semiconductor device. Typically, the cap structure is coupled to the semiconductor device via the thermally conductive epoxy. In some embodiments, the cap structure is formed by using a thermally conductive material, such as a metal, for example. In other embodiments, the cap structure is formed by using a thermally conductive, electrically insulting material, such as a ceramic, for example. The cap structure has a dimension that approximates a dimension of an exterior surface of the package, or alternatively, the cap structure has a dimension that is less than an exterior dimension of the package. Typically, the epoxy forms a layer that is approximately the width of the cap structure, or the epoxy forms a layer that is approximately the width of the semiconductor device.

In some implementations, the cap structure has a dimension that varies from the interior to the exterior of the package. For instance, where the cap structure comprises a step, a smaller portion of the cap structure faces the interior of the package, while a larger portion of the cap structure faces the exterior of the package to aid in heat dispersion. As another example, the cap structure has a tapered shape that broadens toward the exterior surface of the package. In some cases, the cap structure comprises an interlocking feature that is formed by using a step and/or a tapered shape. Preferably, in these cases, the smaller portion of the cap structure is located near the exterior of the package, while the larger portion is located near the interior of the package.

In some embodiments, the epoxy is replaced by a thermally and electrically conductive solder paste, and a copper layer is added between the solder paste and the cap structure. In some embodiments, a second copper layer is added such that the cap structure is sandwiched between the two copper layers. In some embodiments, a heat sink is thermally coupled to second copper layer at the stop surface of the package.

DETAILED DESCRIPTION

In the following description, numerous details and alternatives are set forth for purpose of explanation. However, one of ordinary skill in the art will realize that the invention can be practiced without the use of these specific details. In other instances, well-known structures and devices are shown in block diagram form in order not to obscure the description of the invention with unnecessary detail.

In a particular embodiment, a package is configured to dissipate heat during operation via at least a bottom side and/or a top side of the package. For packages that dissipate heat from a bottom side, bonding means transfer the heat from a heat generating device, such as a semiconductor device, or die, through metal terminals and/or through exposed semiconductor device attach pads to a printed circuit board (PCB). The bonding means can include, but are not limited to, solder balls, pillar bumps, or binding wires.

For packages that dissipate heat from a top side, at least one side of the semiconductor device is exposed to the outside environment in some embodiments. Hence, in these packages, heat transfer is achieved via the semiconductor device body itself.FIG. 1illustrates a package for heat transfer via at least one exposed surface of a semiconductor device according to an embodiment. A package100includes a molding102that encapsulates at least a portion of a semiconductor device104, such as a die, and one or more terminals106. A bonding means108electrically couples the semiconductor device104to one or more of the terminals106. Preferably, the bonding means108is thermally conductive and provides for thermal transfer from the semiconductor device104to the terminal106. The semiconductor device104and/or the one or more of the terminals106are positioned at or near a surface of the package100, such that heat from the semiconductor device104is advantageously transferred to the exterior of the package100, via the exposed portion of the semiconductor device104, or the exposed portions of the one or more terminals106, or both. As shown inFIG. 1, a surface of the semiconductor device104is exposed for heat dissipation via the exposed semiconductor device surface, and a surface of each terminal106is exposed for heat dissipation via the exposed terminal surface. In some embodiments, a side surface of the semiconductor device and/or one or more terminals is exposed, which form one or more other heat dissipation surfaces.

In certain instances, it is preferable that the semiconductor device is not directly exposed at the exterior of the package. Hence, alternatively, the semiconductor device is covered by and thermally coupled to another structure to cover the semiconductor device, and the structure is exposed at one or more surfaces of the package. For example, the additional structure can include a thermally conductive layer, which has one side exposed to the outside environment. In some embodiments, the thermally conductive layer is formed using a thermally conductive epoxy. In other embodiments, the thermally conductive layer is formed using a thermally conductive epoxy and a metal cap.

In some embodiments, the thermally conductive epoxy has shock and/or force absorbing properties. In packages that use such a thermally conductive epoxy, the thermally conductive layer not only helps to transfer heat from the semiconductor device to the outside environment, but also serves as a cushion to absorb impact to the semiconductor device. Such impact often occurs during mold cavity clamping step of the molding process.

In some embodiments, heat transfer is advantageously achieved by two routes, a first route via a thermally conductive layer on top, and a second route via a bottom exposed semiconductor device attach pad. In these packages, the exposed semiconductor device attach pad at the bottom of the package encourages efficient heat transfer to the printed circuit board, while the thermally conductive layer has a variety of applications at the top surface of the package. For instance, the top layer of some embodiments advantageously provides for coupling to another structure and/or node external to the top surface of the package.

Alternatively, or in conjunction with a thermally conductive epoxy type material, the thermally conductive layer at the top of the package can be formed by using a thermally conductive cap structure. The material of the cap structure is selected, at least in part, based on its ability to enhance the dissipation of heat. Further, the top exposed thermally conductive layer of various embodiments is formed into a variety of advantageous shapes. For example, the semiconductor devices of some packages are small. Hence, the ability of these small semiconductor devices to transfer heat through a bottom exposed pad is limited. However, for these cases, a thermally conductive layer is preferably added near the top of the package, to advantageously disperse and/or transfer heat toward the top surface of the package. The top thermally conductive layer is preferably formed by using an epoxy and/or a cap structure that is advantageously malleable to meet the particular size and/or shape requirements for the smaller semiconductor devices. Moreover, it is often advantageous that the top exposed thermally conductive layer itself has a small or other particular shape. Further, the various shapes and sizes of the top exposed thermally conductive layer are combined with one or more bottom exposed features, such as a semiconductor device attach pad, for increased and/or maximized thermal transfer. Examples of certain embodiments of the package are further described below, by reference to the figures.

Top Exposed Layer and Thermal Cushion

Embodiments employing a top exposed layer and/or a thermal cushion are further described in relation toFIG. 1A. More specifically,FIG. 1Aillustrates a package100A for heat transfer via a thermally conductive layer110A near a top surface of the package. As shown inFIG. 1A, the package100A includes a molding compound102A that is typically a plastic or resin type material, that encapsulates a semiconductor device104A, such as a die.

The semiconductor device104A is preferably electrically coupled to one or more terminals106A by using a bonding means108A. One of ordinary skill recognizes a variety of bonding means including, but not limited to, solder balls, pillar bumps, and/or bonding wires. However, the bonding means is advantageously selected for the ability to transfer heat. In some embodiments, the thermally conductive layer110A is formed by using a thermally conductive epoxy. In some embodiments, the thermally conductive epoxy is not electrically conductive so as to electrically isolate the semiconductor device104A. Examples of thermally conductive, electrically insulating epoxies include, but are not limited to, AbleStick 84-3, 2025DS, 8006NS, DF-125, and NEX140. In other embodiments, the thermally conductive epoxy is also electrically conductive. Examples of thermally and electrically conductive epoxies include, but are not limited to, 8600, 2600AT, and 8008HT. In general, thermally conductive, electrically insulating epoxies have a lower thermal conduction rate than thermally and electrically conductive epoxies. However, using epoxies that are both thermally and electrically conductive for the thermally conductive layer110A sacrifices the electrical safety of the semiconductor device104A. The thermally conductive layer110A of these embodiments advantageously receives heat from the semiconductor device104A and transfers the heat to a location that is external to the package100A.

FIG. 2illustrates a package200for heat transfer via a cushion210with a bottom exposed semiconductor device attach pad214. In some embodiments, the cushion210is formed by using a thermally conductive epoxy that is coupled to a semiconductor device204. The cushion210advantageously conducts heat from within the package200to an external location. The cushion210is configured and functions similarly to the thermally conductive layer110A ofFIG. 1A. Since in these embodiments, the cushion210is located near a top surface of the package200, heat is advantageously transferred from the semiconductor device204via the cushion210, without affecting the electrical and/or thermal contacts at the bottom surface of the package200. Moreover, space is typically in short supply at a bottom surface of these packages200, as illustrated by the inclusion of the pad214and contact leads and/or terminals206inFIG. 2.

Cap Structure

FIG. 3illustrates a package300for heat transfer via a cap structure312. As shown inFIG. 3, the cap structure312is exposed at a surface of the package300, and is coupled within the interior of the package300to a semiconductor device304by using a layer of thermally conductive epoxy310. In the implementation300ofFIG. 3, the layer of thermally conductive epoxy310and the cap structure312spans the width of the package300.

In some embodiments, the cap structure312is made of a metal material, which is both thermally and electrically conductive. To provide electrical isolation for the semiconductor device304when the cap structure312is a metal cap, the thermally conductive epoxy310is electrically insulating. Epoxies that are thermally conductive, but electrically insulating typically have a thermal conductivity of less than 1 W/mK. A thermally conductive, electrically insulating epoxy has a lower thermal conductivity than a thermally and electrically conductive epoxy, which typically has a thermal conductivity of more than 2.5 W/mK.

To improve the heat dissipation property of the package300while maintaining the electrical safety of the semiconductor device304, in some embodiments the thermally conductive epoxy310is made using a thermally and electrically conductive epoxy, and the cap structure312is made using a thermally conductive, electrically insulating material. In some embodiments, the thermally conductive, electrically insulating cap structure material is a ceramic. Examples of ceramic used as a thermally conductive, electrically isolating material include, but are not limited to, aluminum oxide, which has a thermal conductivity of about 24 W/mK, and aluminum nitride, which has a thermal conductivity of about 180 W/mK.

FIG. 4illustrates an alternative implementation400of the package300ofFIG. 3. In the implementation400ofFIG. 4, the layer of thermally and electrically conductive epoxy410spans the width of the semiconductor device404, and the thermally conductive, electrically insulating cap structure412spans the width of the package400.

FIG. 5illustrates an alternative implementation500of the package400ofFIG. 4. In the implementation500ofFIG. 5, the thermally conductive, electrically insulating cap structure512has a variety of widths for different portions of the cap structure512. For instance, inFIG. 5the cap structure512has the width of the package500at the external, exposed surface, while the cap structure512has the width of the semiconductor device504at least at an internal surface of the cap structure512that is coupled to the semiconductor device504, via the thermally and electrically conductive epoxy510, within the interior of the package500. The configuration500maximizes the surface area coupling the cap structure512and the semiconductor die, and also maximizes the surface area of the cap structure512exposed at the top surface of the package500. As shown inFIG. 5, the cap structure has a step configuration where transitioning from the width of the exposed top surface to the width of the semiconductor device. It is understood that alternative transition configurations can be used.

FIG. 6illustrates an alternative implementation of the package500ofFIG. 5. A thermally conductive, electrically insulating cap structure612is coupled to a semiconductor device604via a thermally and electrically conductive epoxy610. As shown inFIG. 6, the shape of the thermally conductive, electrically insulating cap structure612includes a variety of features, such as a gradual tapering configuration from the width of the semiconductor device604internal to the package600to the width at the external, exposed surface of the package600. Such a configuration further includes particular advantages in the use of space within the package600, while promoting efficient heat transfer to the exterior of the package600.

Cap Structure for Small Die

FIGS. 7 through 10illustrate embodiments of the package that are suitable for small semiconductor devices. For instance,FIG. 7illustrates a thermally conductive, electrically insulating cap structure712coupled to a small semiconductor device704by using a thermally and electrically conductive epoxy710. The semiconductor device704is smaller than the semiconductor devices104-604inFIGS. 1-6. The cap structure712is similarly configured as the cap structure512inFIG. 5. The epoxy710spans the width of the semiconductor device704. The epoxy710and the cap structure712advantageously conduct heat from the semiconductor device704and transfer the heat to a location exterior to the package700.

FIG. 8illustrates an alternative implementation800of the package700ofFIG. 7. A thermally conductive, electrically insulating cap structure812is coupled to a semiconductor device804via a thermally and electrically conductive epoxy810. In the implementation800ofFIG. 8, the cap structure812has a tapered shape similar in configuration to the cap structure612inFIG. 6. The epoxy810spans the width of the semiconductor device804.

InFIGS. 7 and 8, the layers of epoxy710and810, respectively, extend and/or are applied first to the dimensions of the semiconductor devices704and804, respectively. Alternatively, inFIGS. 9 and 10, thermally and electrically conductive epoxy layers910and1010extend and/or are applied first to the dimensions of thermally conductive, electrically insulating cap structures912and1012, respectively.

More specifically,FIG. 9illustrates a thermally and electrically conductive epoxy layer910that has an alternative shape or dimension than the epoxy710of the package700ofFIG. 7. Similarly,FIG. 10illustrates a thermally and electrically conductive epoxy layer1010that has an alternative dimension than the epoxy810of the package800ofFIG. 8. Hence, as further shown in these figures, the interface between the semiconductor device, the thermally conductive layer, and the exterior of the package has a variety of dimensions to meet the needs of a variety of package specifications and/or applications. The packages described above, are also selectively used in conjunction with additional mechanisms for heat transfer, for example, at a bottom surface of the package.

Exposed Pad

FIG. 11illustrates a package1100for heat transfer via a thermally conductive layer and a bottom exposed pad1114. The thermally conductive layer includes a thermally conductive, electrically insulating cap structure1112and a thermally and electrically conductive epoxy1110. As described above, the cap structure1112is preferably located near a top portion of the package1100. A semiconductor device1104is coupled to the cap structure1112via the epoxy1110. The cap structure1112and the epoxy1110are similarly configured as the cap structure312and the epoxy310inFIG. 3. The semiconductor device1104is electrically and thermally coupled to the pad1114and/or one or more terminals1106via bonding means1108. Preferably, the pad1114and the one or more terminals1106are exposed at a surface of the package1100. One of ordinary skill recognizes a variety of bonding means including, but not limited to, solder balls, pillar bumps, and/or bonding wires.

FIG. 12illustrates an alternative implementation1200of the package1100ofFIG. 11. A thermally conductive, electrically insulating cap structure1212is coupled to a semiconductor device1204via a thermally and electrically conductive epoxy1210. The semiconductor device1204is electrically and thermally coupled to a pad1214and/or one or more terminals1206via bonding means1208. The cap structure1212and the epoxy1210are similarly configured as the cap structure412and the epoxy410inFIG. 4. In the implementation1200ofFIG. 12, the epoxy1210has the width of the semiconductor device1204.

FIG. 13illustrates an alternative implementation1300of the package1200ofFIG. 12. A thermally conductive, electrically insulating cap structure1312is coupled to a semiconductor device1304via a thermally and electrically conductive epoxy1310. The semiconductor device1304is electrically and thermally coupled to a pad1314and/or one or more terminals1306via bonding means1308. The cap structure1312and the epoxy1310are similarly configured as the cap structure512and the epoxy510inFIG. 5. In the implementation1300ofFIG. 13, the cap structure1312has a wider width at an exterior of the package1300than at the epoxy1310, where the cap structure1312preferably has the width of the semiconductor device1304. As shown inFIG. 13, the cap structure has a step configuration where transitioning from the width of the exposed top surface to the width of the semiconductor device. It is understood that alternative transition configurations can be used.

FIG. 14illustrates an alternative implementation1400of the package1300ofFIG. 13. A thermally conductive, electrically insulating cap structure1412is coupled to a semiconductor device1404via a thermally and electrically conductive epoxy1410. The semiconductor device1404is electrically and thermally coupled to a pad1414and/or one or more terminals1406via bonding means1408. The cap structure1412and the epoxy1410are similarly configured as the cap structure612and the epoxy610inFIG. 6. The implementation1400ofFIG. 14includes the cap structure1412that has a tapered shape. Thus, the cap structure of different embodiments has a variety of shapes, which provide space savings and/or promote efficient heat transfer for example. Moreover, the packages1100,1200,1300, and1400, include both a thermally conductive layer near the top of the package, and thermally conductive bottom exposed terminals and die pad, for improved heat transfer via a plurality of routes.

Small Cap Structure

FIG. 15illustrates a package1500for heat transfer via a thermally conductive, electrically insulating small cap structure1512that is exposed at a top surface of the package1500. The cap structure1512has a width that is approximately the width of a semiconductor device1504to which it is coupled by using a thermally and electrically conductive epoxy1510. In this implementation, the dimensions of the cap structure1512are less than the dimensions of the surface of the package1500at which the cap structure1512is exposed. For instance, the cap structure1512of some embodiments has dimensions 0.7 by 0.7 millimeters, while the package1500of these embodiments has dimensions of about 1 by 1 millimeters.

FIG. 16illustrates an alternative implementation1600of the package1500ofFIG. 15. A thermally conductive, electrically insulating cap structure1612is coupled to a semiconductor device1604via a thermally and electrically conductive epoxy1610. As shown inFIG. 16, the package1600includes a cap structure1612that has an interlocking feature, such as a step, at one or more edges of the cap structure1612. The interlocking feature is preferably embedded within the encapsulant1602of the package1600to advantageously minimize separation of the cap structure1612from the package1600.

FIG. 17illustrates an alternative implementation1700of the package1600ofFIG. 16. A thermally conductive, electrically insulating cap structure1712is coupled to a semiconductor device1704via a thermally and electrically conductive epoxy1710. As shown inFIG. 17, the cap structure1712of different embodiments has an interlocking feature that employs a variety of shapes to achieve improved resistance to separation from the package1700.

Small Cap Structure and Exposed Die Pad

FIG. 18illustrates a package1800for heat transfer via a thermally conductive layer on top with a bottom exposed die pad1814. The thermally conductive layer includes a thermally conductive, electrically insulating cap structure1812and a thermally and electrically conductive epoxy1810. As shown inFIG. 18, the molding compound1802encapsulates a semiconductor device1804that is coupled on one surface to one or more terminals1806and to a die pad1807. Preferably, one or more terminals1806and the die pad1807are exposed at a surface of the package1800. The cap structure1812and the epoxy1810are similarly configured as the cap structure1512and the epoxy1510inFIG. 15. The semiconductor device1804is electrically and thermally coupled to the pad1814and/or one or more terminals1806via bonding means1108. One of ordinary skill recognizes a variety of bonding means including, but not limited to, solder balls, pillar bumps, and/or bonding wires.

FIG. 19illustrates an alternative implementation1900of the package1800ofFIG. 18. A thermally conductive, electrically insulating cap structure1912is coupled to a semiconductor device1904via a thermally and electrically conductive epoxy1910. The cap structure1912and the epoxy1910are similarly configured as the cap structure1612and the epoxy1610inFIG. 16. As shown inFIG. 19, the cap structure1912includes an interlocking feature embedded within the package1900to advantageously resist separation from the package1900.

FIG. 20illustrates an alternative implementation2000of the package1900ofFIG. 19. A thermally conductive, electrically insulating cap structure2012is coupled to a semiconductor device2004via a thermally and electrically conductive epoxy2010. The cap structure2012and the epoxy2010are similarly configured as the cap structure1712and the epoxy1710inFIG. 17. As shown inFIG. 20, the interlocking feature of different embodiments has a variety of shapes that serve to prevent separation from the package2000.

Thermal Cushion and Copper Layer

In some embodiments, the thermally and electrically conductive epoxy is replaced by a solder paste, and a copper layer is added between the solder paste and the cap structure. Both the solder paste and the copper layer are thermally and electrically conductive.FIG. 21illustrates a package2100for heat transfer via a thermally conductive layer. The thermally conductive layer includes a thermally conductive, electrically insulating cap structure2112, a thermally and electrically conductive solder paste2114, and a thermally and electrically conductive copper layer2116. As shown inFIG. 21, the molding compound2102encapsulates a semiconductor device2104that is coupled on one surface to one or more terminals2106. Preferably, one or more terminals2106are exposed at a surface of the package2100. The semiconductor device2104is electrically and thermally coupled to the one or more terminals2106via bonding means2108. One of ordinary skill recognizes a variety of bonding means including, but not limited to, solder balls, pillar bumps, and/or bonding wires.

In an exemplary implementation, an SAC305solder paste having a thermal conductivity of about 58.7 W/mK is used. Copper has a thermal conductivity of about 400 W/mK. The use of the solder paste and the copper layer provides improved heat dissipation over the use of thermally and electrically conductive epoxy.

As shown inFIG. 21, the cap structure2112, the copper layer2116, and the solder paste2114are similarly configured as the cap structure312and the epoxy310inFIG. 3. Alternative configurations are also contemplated. For example, the cap structure can be configured similarly to any of the cap structures shown inFIGS. 3-20, and the copper layer and the solder paste can be configured similarly to any of the epoxy configurations shown inFIGS. 3-20. Alternatively, the cap structure and copper layer can be configured similarly to any of the cap structures shown inFIGS. 3-20, and the solder paste can be configured similarly to any of the epoxy configurations shown inFIGS. 3-20.

In some embodiments, additional heat dissipating components can be added.FIG. 22illustrates an alternative implementation2200of the package2100ofFIG. 21. A thermally conductive layer including a thermally conductive, electrically insulating cap structure2212, a thermally and electrically conductive solder paste2214, and a thermally and electrically conductive first copper layer2216is similarly configured as the thermally conductive layer including the thermally conductive, electrically insulating cap structure2112, the thermally and electrically conductive solder paste2114, and the thermally and electrically conductive copper layer2116ofFIG. 21. Additionally, a thermally and electrically conductive second copper layer2218is coupled to the cap structure2212such that the cap structure2212is sandwiched between the first copper layer2216and the second copper layer2218. A heat sink2220is coupled to the top of the package2200such that the heat sink2220is thermally coupled to the second copper layer2218. In some embodiments, the heat sink2220is coupled to the second copper layer2218using a thermally conductive adhesive or solder.

As shown inFIG. 22, the cap structure2112, the first copper layer2116, the second copper layer2118, and the solder paste2114are similarly configured as the cap structure312and the epoxy310inFIG. 3. Alternative configurations are also contemplated. For example, the cap structure and the second copper layer can be configured similarly to any of the cap structures shown inFIGS. 3-20, and the first copper layer and the solder paste can be configured similarly to any of the epoxy configurations shown inFIGS. 3-20. Alternatively, the cap structure, the first copper layer, and the second copper layer can be configured similarly to any of the cap structures shown inFIGS. 3-20, and the solder paste can be configured similarly to any of the epoxy configurations shown inFIGS. 3-20.

Method

FIG. 23is a flow illustrating a process2300for forming the package of some embodiments. As shown in this figure, the process2300begins at the step2310, where a leadframe is provided. In some embodiments, a leadframe is formed by etching and/or stamping a metal layer. The leadframe optionally includes one or more contact terminals and/or one or more die attach pads. Once the leadframe is provided at the step2310, the process2300transitions to the step2320, where a bonding means is coupled to the leadframe and/or to a semiconductor device. For instance, in some embodiments, solder balls are placed on a top surface of the leadframe and/or on a surface of the semiconductor device. In some embodiments, coupling is achieved by screen printing the leadframe with solder on its surface at a location of solder balls or pillar bumps. The solder balls or pillar bumps are attached to the circuit surface. Then, the process2300transitions to the step2330, where the semiconductor device is attached and/or bonded to the leadframe, including the contact terminals and/or attach pads of the leadframe. As mentioned above, the bonding is performed by using conventional bonding means including, but not limited to, solder, solder balls, and/or pillar bumps. In some embodiments, bonding is effectuated by a standard semiconductor assembly reflow process. After the semiconductor device is bonded to the leadframe, the process2300transitions to the step2340, where a thermally conductive layer is formed. In a particular implementation, the thermally conductive layer includes a thermally and electrically conductive cushion. The cushion of some embodiments is formed by applying a layer of thermally conductive adhesive and/or epoxy to a surface of the semiconductor device.

Alternatively, some embodiments include an additional thermally conductive, electrically insulating cap structure. The epoxy is optionally applied to a surface of the cap structure. The cap structure is then coupled to the semiconductor device by via the layer of epoxy. In some embodiments, the cap structure comprises a material that has particular heat transference and electrical insulating properties, such as a ceramic, for example.

Still alternatively, in some embodiments, the thermally and electrically conductive epoxy is replaced by solder paste. In addition, a copper layer is applied to the solder paste, and the cap structure is applied to the copper layer. A high temperature eutectic melting process is formed to join the copper layer to the cap structure. In some embodiments, the cap structure forms the top surface, or a portion thereof, of the package. In other embodiments, a second copper layer is applied to the top surface of the cap structure such that the cap structure is sandwiched between the two copper layers. The two copper layers are applied prior to the high temperature eutectic melting process. After the high temperature eutectic melting process, a heat sink is applied to the top of the package such that the heat sink is thermally coupled to the second copper layer. In some embodiments, the heat sink is coupled to the second copper layer using a thermally conductive adhesive or solder.

After the thermally conductive layer is formed at the step2340, the process2300transitions to the step2350, where a molding compound is used to encapsulate the package. Preferably, the encapsulation at the step2350leaves a bottom surface of the contact terminal(s) and/or attach pad(s) exposed at the exterior of the package. Further preferably, the encapsulation leaves a top surface of the thermally conductive layer, such as the thermally conductive cushion, the cap structure, the electrical insulating material, or the copper layer, exposed at an exterior of the package. The step2350of some embodiments alternatively includes additional steps such as singulation, etching, and/or stamping or other means to leave the selected thermally and/or electrically conductive elements of the package exposed at the exterior surfaces.