Semiconductor Package with Insert

A semiconductor package includes a semiconductor die thermally coupled to a planar metal pad, an encapsulant body that encapsulates the semiconductor die and includes a recess that extends from an outer upper side of the encapsulant body towards a rear side of the planar metal pad, and an insert arranged within the recess that is thermally coupled to the planar metal pad and extends to the outer upper side of the encapsulant body, wherein the insert that is arranged within the recess includes a curable polymer compound.

BACKGROUND

Semiconductor packages can be configured to dissipate heat by thermally coupling the die to a heat sink. One possible semiconductor package configuration has an exposed die pad at its rear surface so the die pad can be directly thermally coupled to a heat sink. However, in some cases an exposed die pad is not possible because the die pad is connected to an electrical potential and therefore must be electrical isolated. Current approaches to solving this problem suffer from various drawbacks including unwanted process variation and increased time and expense in board assembly.

SUMMARY

A semiconductor package is disclosed. According to an embodiment, the semiconductor package comprises a semiconductor die thermally coupled to a planar metal pad, an encapsulant body that encapsulates the semiconductor die and comprises a recess that extends from an outer upper side of the encapsulant body towards a rear side of the die pad, and an insert arranged within the recess that is thermally coupled to the die pad and extends to the outer upper side of the encapsulant body, wherein the insert that is arranged within the recess comprises a curable polymer compound.

A method of forming a semiconductor package is disclosed. According to an embodiment, the method comprises thermally coupling a semiconductor die to a planar metal pad, forming an encapsulant body that encapsulates the semiconductor die and comprises a recess that extends from an outer upper side of the encapsulant body towards a rear side of the die pad, and providing an insert within the recess that is thermally coupled to the die pad and extends to the outer upper side of the encapsulant body, wherein the insert that is arranged within the recess comprises a curable polymer compound.

A method of assembling an electronics device is disclosed. According to an embodiment, the method comprises providing a plurality of semiconductor packages, each of the semiconductor packages comprising a semiconductor die thermally coupled to a planar metal pad, an encapsulant body that encapsulates the semiconductor die, a plurality of leads exposed from the encapsulant body, a recess that extends from an outer upper side of the encapsulant body towards a rear side of the die pad, and an insert arranged within the recess that is thermally coupled to the die pad and extends to the outer upper side of the encapsulant body, providing a circuit carrier that comprises a plurality of contact pads disposed on an upper side of the circuit carrier, arranging the plurality of semiconductor packages on the circuit carrier with the leads facing the contact pads and with the outer upper sides of each of the encapsulant bodies facing away from the circuit carrier, arranging a heat sink over the plurality of semiconductor packages such that the heat sink contacts at least some of the inserts, and joining the heat sink to each of the inserts so as to form a thermally coupled connection between the heat sink and each of the semiconductor packages, wherein joining the heat sink to each of the inserts comprises flowing material from the inserts laterally away from the recesses.

DETAILED DESCRIPTION

Embodiments of a semiconductor package, a method of forming the semiconductor package, and a method of assembling a plurality of the semiconductor packages are disclosed herein. The semiconductor package comprises a semiconductor die mounted on a die pad that is encapsulated by an encapsulant body. A recess is formed in the encapsulant body that exposes a rear side of the die pad. An insert is provided within the recess that is thermally coupled to the die pad and hence to the semiconductor die mounted thereon. The insert may completely fill the recess and protrude past an outer upper side of the encapsulant body. The insert comprises a curable polymer compound, e.g., thermoset polymer, UV curable polymer, moisture curable polymer, catalytic polymer, etc. In the method of assembling a plurality of the semiconductor packages, a group of the semiconductor packages each having this insert configuration can be mounted on a single carrier structure. Advantageously, the semiconductor packages can have height variations relative to the circuit carrier, and a multi-device heat sink can nevertheless mate with each semiconductor package along a single plane. This is because the curable polymer compound can be flowed and redistributed to and eliminate any height discrepancy and form a planar mating interface between each semiconductor package and the heat sink. Concurrently or simultaneously, the curable polymer compound can be cured to form a hardened attachment interface.

Referring toFIG.1, a semiconductor package100is depicted, according to an embodiment. The semiconductor package100comprises a semiconductor die102. Generally speaking, the semiconductor die102can be any of a wide variety of device types, e.g., discrete device, logic device, passive device, sensor, etc. According to an embodiment, the semiconductor die102is configured as a power device that is rated to withstand voltages of at least 100V (volts), and more typically voltages of 600V, 1200V or more and/or is rated to accommodate currents of at least 1 A, and more typically currents of10A,50A,100A or more. Examples of power devices include discrete power diodes and discrete power transistor dies, e.g., MOSFETs (Metal Oxide Semiconductor Field Effect Transistors), IGBTs (Insulated Gate Bipolar Transistors), and HEMTs (High Electron Mobility Transistors), etc.

The semiconductor package100comprises a planar metal pad104and a plurality of package leads106. The planar metal pad104and the package leads106can be provided formed of a conducive metal, e.g., copper, nickel, aluminum, etc., and alloys or combinations thereof. The semiconductor die102is thermally coupled to the planar metal pad104. This may be done using an adhesive, e.g., solder, sinter, glue, tape, etc. Terminals of the semiconductor die102are electrically connected to the package leads106. In the depicted embodiment, the planar metal pad104is a metal die pad that is electrically isolated within the encapsulant body110and the semiconductor die102is mounted on this die pad with upper surface terminals facing away from the die pad. The upper surface terminals of the semiconductor die102are electrically connected to the package leads106. As shown, at least some of these electrical connections are provided by bond wires108. Other types of electrical interconnect elements, e.g., metal clips, ribbon, etc., may be used instead to provide these electrical connections. As shown, one of the package leads106is directly electrically connected to an upper surface terminal of the semiconductor die102via a package lead106that is configured as a clip connector. In that case, the semiconductor die102can be configured as a lateral device, wherein the rear surface connection between the die and the planar metal pad104does not form a terminal connection. In other embodiments, the semiconductor die102can be configured as a vertical device with a load terminal, e.g., source, drain, collector, emitter, etc., disposed at a rear side of the semiconductor die. In that case, the planar metal pad104can form a continuous connection with a package lead106(e.g., as shown inFIG.5) or be electrically connected to a package lead106by an electrical interconnect element.

The semiconductor package100comprises an encapsulant body110that encapsulates the semiconductor die102. The encapsulant body110is formed from an electrically insulating material that surrounds and protects the semiconductor die102and associated electrical connections. The encapsulant body110can comprise any of a wide variety of electrical insulators that are suitable package materials, e.g., mold compound, epoxy, polymer, ceramic, glass-woven fiber materials, etc. According to an embodiment, the encapsulant body110is formed by a molding technique, e.g., injection molding, compression molding, transfer molding, etc. In that case, the encapsulant body110can comprise a mold compound. Alternatively, the encapsulant body110can be formed by a lamination technique whereby multiple layers of laminate material, e.g., a glass-woven fiber such as FR-4, are successively stacked on top of one another.

Outer ends of the package leads106are exposed from the encapsulant body110, thus forming externally accessible points of electrical contact to the semiconductor package100. The depicted package configuration corresponds to a so-called surface mount package type. The insert concept described herein is more generally applicable to a wide variety of package types, including so-called flat packages, leadless packages, through-hole packages, etc.

The encapsulant body110of the semiconductor package100comprises a recess112that extends from an outer upper side114of the encapsulant body110towards a rear side of the planar metal pad104, which in turn is opposite from the upper side of the planar metal pad104to which the semiconductor die102is mounted on. As shown, the recess112extends completely to the rear side of the planar metal pad104, thus exposing the rear side of the planar metal pad104. Alternatively, the recess112may extend partially into the encapsulant body110such that a thickness of encapsulant material remains covering the rear side of the planar metal pad104. The recess112therefore removes or at least reduces the amount of encapsulant material from the encapsulant body110between the planar metal pad104and the exterior environment.

The recess112can be formed in a variety of ways. For example, in the case that the encapsulant body110is formed by a molding process, the molding chamber can be adapted to form the encapsulant body110with the recess112. Alternatively, the encapsulant body110can be initially formed with encapsulant material in the place of the recess112, and the recess112can be formed by removing material, e.g., etching, mechanical grinding, etc.

The recess112may have a variety of different geometries. As shown, the recess112may have sidewalls that are substantially perpendicular to the outer upper side114of the encapsulant body11and the rear side of the planar metal pad104. Alternatively, the sidewalls of the recess112may be oriented at an oblique angle relative to the outer upper side114and/or the rear side of the planar metal pad104. Separately or in combination, instead of having acute corners, the recess112may have gradual transitions. Separately or in combination, instead of smooth sidewalls, the sidewalls of the recess112may comprise features that increase the surface area of the sidewalls and enhance adhesion with the insert124to be described below.

According to an embodiment, the encapsulant body110comprises one or more overflow channels116. The location of the bottom surfaces118of these overflow channels116are shown inFIG.1Aand the sidewalls120of the overflow channels116is shown inFIG.1B. The overflow channels116each extend vertically into the encapsulant body110from the outer upper side114of the encapsulant body110and extend laterally from the sidewalls of the recess112to the outer edge sides122of the encapsulant body110. The overflow channels116thus form open passages for ingress and egress of fluid from the recess112to the outer edge sides122of the encapsulant body110along a conduit that is below the outer upper side114of the encapsulant body110. Generally speaking, the depth of the overflow channels116can be between 100% and 5% of the depth of the recess112. According to an embodiment, the depth of the overflow channels116is no greater than 25% of the depth of the recess112.

According to an embodiment, the encapsulant body110comprises a plurality of the overflow channels116and one of the overflow channels116extends between the recess112and each one of the outer edge sides122of the encapsulant body110. As a result, the overflow channels116are arranged to facilitate ingress and egress of fluid in every direction. The number of overflow channels116extending from one of the sidewalls of the recess112to one of the outer edge sides122may vary, e.g., two, three (as shown), four, five, etc.

Referring toFIG.2, the semiconductor package100comprises an insert124arranged within the recess112. The insert124is thermally coupled to the planar metal pad104. Preferably, the thermal resistance between the insert124and the planar metal pad104is maintained low such that the insert124forms a thermal conduction path between the planar metal pad104and the exterior environment. As shown, the insert124may directly contact the rear side of the planar metal pad104and hence be directly thermally connected to the planar metal pad104. Alternatively, a thin layer of material may be provided between the insert124and the rear side of the planar metal pad104. For example, as previously mentioned, the recess112may not extend completely to the planar metal pad104such that a small thickness of material from the encapsulant body110, e.g., no greater than 50 μm, no greater than 25 μm, no greater than 10 μm, etc. remains. Separately or in combination, a thin layer of material may be provided between the rear side of the planar metal pad104and the insert124, e.g., an adhesive layer, adhesion promoter, etc., that is no greater than 10 μm thick, no greater than 5 μm thick, etc.

According to an embodiment, the insert124comprises a curable polymer compound. A curable polymer compound refers to a material that can be irreversibly hardened by a curing process. A curable polymer compound comprises monomers capable of being cross-linked by an external stimulus. The curing process induces a chemical reaction in the material to cross-link the polymers. Thus, a curable polymer compound is a precursor material of hardened plastic material. Before the curing process, the curable polymer compound can be in a liquid or semi-liquid state. For example, the curable polymer compound material can comprise a resin with dynamic viscosity in the range of 1,000-50,000 mPa*s (millipascal seconds) at room temperature. Alternatively, the curable polymer compound material can be a powder in a granular or pressed state. Alternatively, the curable polymer compound can be a solid at room temperature with a melting point such that it liquifies during the curing process, thus forming a viscous liquid or quasi-liquid having, e.g., a dynamic viscosity in the range of 1,000-50,000 mPa*s, and then returns to a hardened state during the cooling process. According to an embodiment, the curable polymer compound is a thermoset polymer, which refers to a material that is polymerized through the application of heat. According to another embodiment, the curable polymer compound is a UV curable polymer, which refers to a material that is polymerized through the application of ultraviolet light. According to another embodiment, the curable polymer compound is a moisture-cure polymer compound, which refers to a material that is polymerized through the application of water, examples of which include polyurethane prepolymer. According to another embodiment, the curable polymer compound is a catalytic polymer, which refers to a material that is polymerized through exposure to a chemical catalyst such as an acid.

According to an embodiment, the curable polymer compound comprises a matrix of pre-polymerized resin combined with a filler material. The matrix of pre-polymerized resin comprises monomers that are configured to be cured by the above-described cross-linking reaction. The matrix of polymer may be based on an epoxy resin which contains a hydroxyl group, for example. A percent by weight of the matrix of polymer resin in the curable polymer compound may be in the range of 5% to 50%, for example. The filler material may represent a substantial remaining majority of the percent by weight of the curable polymer compound. For example, the percent by weight of the filler material may be in the range of 50% to 95%, with the combined percentage by weight of the pre-polymerized resin and the filler material being in the range of 95% to 100%, for example. The filler material may be used to adjust the properties of the curable polymer compound in one or both of the uncured or cured state, e.g., thermal conductivity, viscosity before curing, coefficient of thermal expansion, melting point after curing, etc. For example, the thermal conductivity of the insert124can be increased by incorporated thermally conductive filler materials. The filler material may comprise particles that are intermixed with the matrix of pre-polymerized resin. Examples of the filler materials include crystalline silica, fused silica, spherical silica, titanium oxide, aluminum hydroxide, aluminum oxide, aluminum nitride, silicone nitride, magnesium hydroxide, zirconium dioxide, calcium carbonate, calcium silicate, talc, clay, carbon fiber, glass fiber and mixtures thereof. The curable polymer compound may also comprise a small percentage, e.g., within 1% to 5% percent by weight of the curable polymer compound, of other additive materials. Examples of these materials include adhesion promoters and hardening agents.

The insert124may be provided within the recess112in a variety of different ways. According to an embodiment, the semiconductor package100is formed to comprise the encapsulant body110with the recess112according to any of the above-described. Subsequently, the insert124is formed by a pre-molding step whereby the recess is filled by a mixture of material. According to an embodiment, the mixture of material may comprise a matrix of pre-polymerized resin combined with a thermally conductive filler. In the case of a curable polymer compound that is configured as a semi-liquid, the mixture may be provided within the recess112by an injection technique whereby the material is slightly heated to decrease the viscosity of the material, but the material remains below the temperature at which substantial cross-linking of the polymers occur. In the case of a curable polymer compound that is configured as a powder, the mixture may be pressed into the into the recess112by means of a stamp. In either case, the curable polymer compound material may be provided within at least a portion of the overflow channels116. This may result from mechanical pressure being applied to the insert124material to force it through the overflow channels116or through the natural flow of the material. In any case, the overflow channels116advantageously aid in the adhesion of the insert124to the encapsulant body110by providing an interlocking mechanism. By securely affixing the insert124within the recess112in a pre-cured state with the proper viscosity, the semiconductor package100comprising the insert124can be produced by a manufacturer and transported to a downstream assembler that mounts the semiconductor package100and cures the curable polymer compound, e.g., according to the technique described below.

The insert124is arranged within the recess112so as to fill the recess112and extend at least to the outer upper side114of the encapsulant body110. As shown, the insert124protrudes past the outer upper side114of the encapsulant body110. That is, the insert124forms an outermost surface of the semiconductor package100that is spaced apart from outer upper side114of the encapsulant body110. According to an embodiment, the insert124protrudes past the outer upper side114of the encapsulant body110by an amount between 50 μm and 1,000 μm (1 mm). More particularly, the insert124may protrude past the outer upper side114of the encapsulant body110by an amount between 100 μm and 200 μm, e.g., about 125 μm to 175 μm. As shown, the upper side126of the insert124may be substantially planar and parallel to the outer upper side114of the encapsulant body110such that the insert124protrudes by a uniform distance. Alternatively, the upper side126of the insert124may comprise ridges, rounded edges, warpage, etc. In that case, the distance that the insert124protrudes past the outer upper side114of the encapsulant body110refers to the distance between the outer upper side114of the encapsulant body110and the highest point of the insert124In other embodiments, the insert124may be at least level with the upper side114of the encapsulant body110, i.e., with substantially no protrusion. This ensures that the recess112is filled and that there is thermal coupling to the planar metal pad104.

Referring toFIG.3A, a method of assembling an electronics device comprises providing a circuit carrier200. The circuit carrier200comprises contact pads202disposed on an electrically insulating substrate. The circuit carrier200may be a laminate based electronics carrier, such as a printed circuit board (PCB). Alternatively, the circuit carrier may be a a power electronics carrier, such as a Direct Copper Bonding (DCB) substrate, a Direct Aluminum Bonding (DAB) substrate, or an Active Metal Brazing (AMB) substrate.

The method comprises providing a plurality of the semiconductor packages100that comprise the insert124arranged within the recess112. The semiconductor packages100are arranged on the circuit carrier200with the package leads106facing the contact pads202. A joining material, such as a solder, sinter, conductive glue may be provided between the package leads106and the contact pads202to effectuate a mechanical and electrical connection therebetween. According to an embodiment, a pre-reacted solder material such as a solder paste comprising a tin based and/or lead-free solder material is provided between the package leads106and the contact pads202. The semiconductor packages100can be mounted and attached to the carrier by performing a heating process whereby the temperature of the solder material is elevated to melt the material and induce a reaction whereby a stable soldered joint is formed. A peak temperature of this heating process occurs at a reflow phase of this heating process. Reflow temperatures for this soldering process may be in the range of 200° C. to 300° C., for example.

The semiconductor packages100are arranged with the outer upper sides114of each of the encapsulant bodies facing away from the circuit carrier200. As a result, the inserts124from each of the semiconductor packages100form an uppermost contact point from above the plurality of the semiconductor packages100. According to an embodiment, the upper sides126of the inserts124are arranged at different heights relative to the upper side of the circuit carrier200. That is, as between the various semiconductor packages100from the plurality, the uppermost contact points are disposed at different vertical separation distance from the circuit carrier200.FIG.3shows three different planes204that are arranged at different heights relative to the upper side of the circuit carrier200and correspond to the uppermost contact point of each of the semiconductor packages100. The different heights of the planes204can be for a variety of reasons. For example, the different heights can be present as between two semiconductor packages100that are supposed to have identical geometric specifications, but actually have a small difference in geometry, e.g., due to process variation. The leftmost pair of semiconductor packages100illustrate one example of two semiconductor packages100that are nominally identical but in fact the inserts124extend to two different planes204that are separated from one another. This difference in height may be up to 10 μm, up to 200 μm, or up to 600 μm, for example. In another example, the different heights can be attributable to semiconductor packages100with different geometric specifications and/or package type, wherein the difference in heights is within the acceptable window to perform the heat sink attachment process to be described below. This difference in height may be up to 50 μm, for example. The rightmost semiconductor package100illustrates an example of this possibility, wherein this package has a different standoff height as the two leftmost semiconductor packages100.

Referring toFIG.3B, a heat sink300is arranged over the plurality of semiconductor packages100such that the heat sink contacts at least some of the inserts124. The heat sink300is a thermally conductive structure that is configured to radiate heat away from multiple semiconductor packages100. The heat sink300may be formed of a thermally conductive metal, e.g., copper, aluminum, etc. At this stage, the curable polymer compound from each of the inserts124is still in an uncured state. Due to the difference in heights between the upper sides126of the inserts124and the circuit carrier200, the heat sink300may not necessarily contact each one of the inserts124, and instead only contacts the highest inserts124from the plurality. Moreover, the heat sink300may not be precisely level and/or parallel to the upper surface of the circuit carrier200due to the to the difference in heights. Depending on the viscosity of the material from each of the inserts124while in an uncured state, some flow of the material from the inserts124is possible such that the heat sink300settles at this time. In the case of harder material from the inserts124, there may be little or no flow of the material from the inserts124at this time.

Referring toFIG.3C, the heat sink300is joined to each of the inserts124to form a thermally coupled connection between the heat sink300and each of the semiconductor packages100. The joining process redistributes the material from the inserts124such that the heat sink300contacts at least some of the inserts124. As shown, the heat sink300contacts the material from each one of the inserts. Depending on the package height and amount of material in the inserts124, the heat sink300may directly contact the upper side114of the encapsulant body110in some embodiments. The inserts124form a thermal conduction path between the planar metal pads104from each of the semiconductor packages100and the heat sink300. The material from the inserts124can be tailored for increased thermal conductivity, e.g., through appropriate selection of the filler materials. The thermal conductivity of the inserts124can be higher than that of the material which forms the encapsulant body110, which does not require thermal conductivity. In this way, an advantageous bifurcation of the materials of the semiconductor package100is realized, wherein the thermally beneficial properties are relegated to the element that accommodates the thermal load (i.e., the insert124) and other beneficial properties are selected for the encapsulant body110, e.g., cost, dielectric strength, etc.

During the joining process, the material of the inserts124may have a liquid or semi-liquid viscosity so as to enable the lateral flow of the insert124material away from the recess112and towards the outer edge sides122of the encapsulant body110. For example, during the joining process, the material of the inserts124may have a dynamic viscosity in the range of 1,000 mPa*s (millipascal seconds) to 50,000 mPa*s. More particularly, the material of the inserts124may have a dynamic viscosity in the range of 5,000 mPa*s to 15,000 mPa*s at this time, which roughly resembles the viscosity of honey at room temperature. The material from the inserts124can be heated to obtain the proper viscosity during the joining process, and a specific example of which will be described in further detail below. Alternatively, the material from the inserts124can have the proper viscosity at room temperature. This may be obtained through proper selection of the filler materials, for example. The viscous flow of the insert124material may result from the natural weight of the heat sink300. Alternatively, direct force may be applied to the heat sink300to induce or aid in the flow of the material.

According to an embodiment, the joining process comprises forming an interface between the lower side of the heat sink300and the insert124material from each of the semiconductor packages100that extends along a single plane206. Thus, in the case that upper sides126of the inserts124are arranged at different heights, the joining process redistributes the insert124material in such a way to form a flat interface that extends along the single plane206and connects the heat sink300to the insert124material from each of the semiconductor packages100. The flat interface between the lower side of the heat sink300and the insert124material from each of the semiconductor packages100may be leveled and/or substantially parallel to the upper side of the circuit carrier200. The joining process redistributes the insert124material such that the volume of insert124material displaced is greatest in the semiconductor packages100with the highest vertical distance from the circuit carrier200and is lowest in the semiconductor packages100with the lowest vertical distance from the circuit carrier200. In this way, the insert124concept provides a buffer region at the upper side of each of the semiconductor packages100that absorbs any discrepancy in package height and ensures that a multi-chip heat sink300structure can be mated with a plurality of semiconductor packages100notwithstanding this discrepancy. This buffer region can accommodate discrepancies in package height of 50 μm, 100 μm, or more.

According to an embodiment, the joining process comprises pushing the material from the inserts124through the overflow channels116. The liquid or semi-liquid state of the insert124material allows it to flow through the overflow channels116and into the exterior environment. The presence of the overflow channels116in the semiconductor packages100can therefore advantageously aid in the heat sink300attachment process by providing regions for the excess insert124material to accumulate and by providing conduits for the insert124material to reach the lateral space outside of the semiconductor packages100. Thus, the amount of discrepancy in vertical height that can be tolerated, can advantageously be increased by the overflow channels116. Furthermore, the overflow channels116ensure that the distance of the planar metal pad104that is closest to the heat sink300will be minimized and close to the height of the recess. By controlling this distance, a favorable tradeoff between thermal resistance and electrical isolation can be obtained. That is, a minimum amount of insulation material necessary to isolate the planar metal pad104from the heat sink300can be realized. In addition to flowing the material from the inserts124, the joining process may comprise curing the curable polymer compound from each of the inserts124, thereby forming a hardened plastic structure that securely affixes the heat sink300to each of the semiconductor packages100. The curing of the curable polymer compound comprises providing the appropriate stimulus to cross-link the polymers according to the type of curable polymer compound. Thus, the curing process may comprise applying heat in the case of a thermoset material, applying UV radiation in the case of a UV curable material, applying moisture to the material in the case of a moisture-cure polymer compound, applying a catalyst in the case of a catalytic polymer, and so forth.

According to an embodiment, each of the inserts124comprises a thermoset polymer in a solid or viscous form and the joining process comprises performing a heat treatment that melts the thermoset polymer to induce the flowing of the material from the inserts124laterally away from the recesses and cures the thermoset polymer. That is, a combined step is formed that liquifies the insert124material, thereby redistributing the insert124material in the above-described manner, and simultaneously induces the reaction that cross-links the polymers to cure the material. In this case, the material from the inserts124can be tailored such that a curing temperature of the material obtains the above-described dynamic viscosity to induce flow of the material. This may be done through appropriate selection of filler materials, for example. The material hardens due to the cross-linkage to form a stable plastic interface between each of the semiconductor packages100and the heat sink300.

According to an embodiment, the heat treatment that melts the thermoset polymer is part of a combined process that that reflows the solder material between the package leads106and the contact pads202. That is, a single heat treatment is performed that melts and cures the thermoset polymer as described above, and additionally solders the semiconductor packages100to the circuit carrier200. This may be done by tailoring the thermoset polymer to have a curing temperature and desired melt viscosity that coincides with the reflow temperature of the solder material.

Referring toFIG.4, the semiconductor package100is depicted, according to two different embodiments. In these embodiments, the planar metal pad104that is thermally coupled to the semiconductor die102is provided as part of a metal interconnect clip128. In the embodiment ofFIG.4A, the insert124interfaces with only the planar metal pad104portion of the interconnect clip128. In the embodiment ofFIG.4B, the recess112is arranged such that the insert124interfaces with a bridge portion of the metal interconnect clip128, which may facilitate a more central arrangement of the insert124for more even flow of insert material to either side.

The semiconductor package100ofFIG.4comprises a lead frame that comprises a lead106and a second planar metal pad104that forms a die pad of the lead frame. The lead106and the second planar metal pad104are exposed at an outer lower side130of the encapsulant body110. The metal interconnect clip128electrically connects an upper surface terminal of the semiconductor die102with the lead106. A lower surface thermal of the semiconductor die, e.g., source, drain, collector, emitter, etc., can be electrically connected to the second planar metal pad104, which in turn may form a package terminal. The arrangements ofFIGS.4A and4Beach provide a double-sided cooling arrangement wherein the semiconductor package100can be thermally coupled to a heat sink300using the insert124in the manner described with reference toFIG.3Aat an upper side of the semiconductor package100, and the semiconductor package100can be thermally coupled to a second heat sink or power electronics carrier at a lower side of the semiconductor package100via the second planar metal pad104.

Referring toFIG.5, the semiconductor package100is depicted, according to another embodiment. In this embodiment, the semiconductor package100comprises a second planar metal pad104that is thermally coupled to the semiconductor die102, and a second recess112that extends from an outer lower side130of the encapsulant body110towards a rear side of the second planar metal pad104. The second planar metal pad104can serve as a die pad that is electrically connected to an upper surface terminal of the semiconductor die and one of the package leads106by an interconnect element such as a bond wire108. A lower surface terminal of the semiconductor die102can be electrically connected to one of the leads106by a continuous structure that also comprises the first metal pad. The semiconductor package further comprises a second124insert arranged within the second recess112that is thermally coupled to the second planar metal pad104and extends to the outer lower side130of the encapsulant body110. The second insert124may have the same material composition as the first insert124according to any of the embodiments as described above. This embodiment provides a double-sided cooling arrangement wherein the semiconductor package100can be thermally coupled to a heat sink300using the insert124in the manner described with reference toFIG.3Aat an upper side of the semiconductor package100, and the semiconductor package100can be thermally coupled to a second heat sink or power electronics carrier at a lower side of the semiconductor package100via the second planar metal pad104and the second insert104.

Example 1. A semiconductor package, comprising: a semiconductor die thermally coupled to a planar metal pad; an encapsulant body that encapsulates the semiconductor die and comprises a recess that extends from an outer upper side of the encapsulant body towards a rear side of the planar metal pad; and an insert arranged within the recess that is thermally coupled to the planar metal pad and extends to the outer upper side of the encapsulant body, wherein the insert that is arranged within the recess comprises a curable polymer compound.

Example 2. The semiconductor package of example 1, wherein the curable polymer compound comprises a matrix of pre-polymerized resin combined with a thermally conductive filler.

Example 3. The semiconductor package of example 2, wherein the encapsulant body comprises a mold compound, and wherein the insert has a greater thermal conductivity than the mold compound.

Example 4. The semiconductor package of example 1, wherein the insert protrudes past the outer upper side of the encapsulant body by an amount between 50 μm and 250 μm.

Example 5. The method of example 1, wherein the electrically insulating encapsulant body comprises one or more overflow channels, wherein the one or more overflow channels each extend vertically into the encapsulant body from the outer upper side of the encapsulant body and extend laterally from the sidewalls of the recess to the outer edge sides of the encapsulant body.

Example 6. The method of example 5, wherein a depth of the one or more overflow channels is no greater than twenty five percent of a depth of the recess.

Example 7. The method of example 5, wherein the electrically insulating encapsulant body comprises a plurality of the overflow channels, wherein the overflow channels form an open passage between an upper region of the recess and each outer edge side of the encapsulant body.

Example 8. The method of example 1, wherein the rear side of the planar metal pad is exposed at a bottom of the recess and the insert directly contacts the rear side of the planar metal pad.

Example 9. The method of example 1, wherein the planar metal pad is a metal die pad that is electrically isolated within the encapsulant body, wherein the semiconductor die is mounted on the metal die pad with upper surface terminals facing away from the metal die pad, and wherein the semiconductor package comprises leads that are electrically connected to the upper surface terminals.

Example 10. The method of example 1, wherein the planar metal pad is an interconnect clip, wherein the semiconductor package comprises a lead that is exposed at an outer lower side of the encapsulant body, and wherein the interconnect clip electrically connects an upper surface terminal of the semiconductor die with the lead.

Example 11. The method of claim1, wherein the semiconductor package further comprises: a second planar metal pad that is thermally coupled to the semiconductor, a second recess that extends from an outer lower side of the encapsulant body towards a rear side of the second planar metal pad, a second insert arranged within the second recess that is thermally coupled to the second planar metal pad and extends to the outer lower side of the encapsulant body, wherein the second insert comprises a curable polymer compound.

Example 12. A method of forming a semiconductor package, the method comprising: thermally coupling a semiconductor die to a planar metal pad; forming an encapsulant body that encapsulates the semiconductor die and comprises a recess that extends from an outer upper side of the encapsulant body towards a rear side of the planar metal pad; and providing an insert within the recess that is thermally coupled to the planar metal pad and extends to the outer upper side of the encapsulant body, wherein the insert that is arranged within the recess comprises a curable polymer compound.

Example 13. The method of example 12, wherein providing the insert within the recess comprises: providing a mixture of material that comprises a matrix of pre-polymerized resin combined with a thermally conductive filler; and filling the recess with the mixture of material.

Example 14. The method of example 13, wherein providing the insert within the recess further comprises: heating the mixture of material to a temperature that is below a curing temperature of the matrix but increases the viscosity of the mixture to reach a semi-liquid state; and filling the recess with the mixture of material in the semi-liquid state.

Example 15. The method of example 13, wherein the electrically insulating encapsulant body comprises one or more overflow channels, each extend vertically into the encapsulant body from the outer upper side of the encapsulant body and extend laterally from the sidewalls of the recess to the outer edge sides of the encapsulant body, and wherein the mixture of material is provided within the one or more overflow channels.

Example 16. A method of assembling an electronics device, the method comprising: providing a plurality of semiconductor packages, each of the semiconductor packages comprising a semiconductor die thermally coupled to a planar metal pad, an encapsulant body that encapsulates the semiconductor die, a plurality of leads exposed from the encapsulant body, a recess that extends from an outer upper side of the encapsulant body towards a rear side of the planar metal pad, and an insert arranged within the recess that is thermally coupled to the planar metal pad and extends to the outer upper side of the encapsulant body; providing a circuit carrier that comprises a plurality of contact pads disposed on an upper side of the circuit carrier; arranging the plurality of semiconductor packages on the circuit carrier with the leads facing the contact pads and with the outer upper sides of each of the encapsulant bodies facing away from the circuit carrier; arranging a heat sink over the plurality of semiconductor packages such that the heat sink contacts at least some of the inserts; and joining the heat sink to each of the inserts so as to form a thermally coupled connection between the heat sink and each of the semiconductor packages, wherein joining the heat sink to each of the inserts comprises flowing material from the inserts laterally away from the recesses.

Example 17. The method of example 16, wherein the joining process comprises forming an interface between the lower side of the heat sink and the insert material from each of the semiconductor packages that extends along a single plane.

Example 18. The method of example 16, wherein before arranging the heat sink over the plurality of semiconductor packages, the upper sides of the inserts are arranged at different heights relative to the upper side of the circuit carrier.

Example 19. The method of example 16, wherein inserts from each of the semiconductor packages comprises a curable polymer compound, and wherein joining the heat sink to each of the inserts comprises curing the curable polymer compound from each of the inserts.

Example 20. The method of example 16, wherein each of the inserts comprises a thermoset polymer, wherein joining the heat sink to each of the inserts comprises performing a heat treatment, and wherein the heat treatment melts the thermoset polymer to induce the flowing of the material from the inserts laterally away from the recesses and cures the thermoset polymer.

Example 21. The method of example 16, wherein the plurality of semiconductor packages is arranged on the circuit carrier with solder material between the leads and the contact pads, and wherein the heat treatment is a combined process that reflows the solder material and melts the material from the inserts.

Example 22. The method of example 16, wherein the electrically insulating encapsulant body comprises a plurality of the overflow channels, wherein the overflow channels form an open passage between an upper region of the recess and each outer edge side of the encapsulant body, and wherein flowing the material from the inserts to form a level interface comprises pushing the material from the inserts through the overflow channels.

Example 23. The method of example 16, wherein before joining the heat sink to each of the inserts the upper sides of the inserts are arranged at different heights relative to the upper side of the circuit carrier, and wherein joining the heat sink to each of the inserts forms an interface between the lower side of the heat sink and the insert material from each of the semiconductor packages that extends along a single plane.

The semiconductor dies disclosed herein can be formed in a wide variety of device technologies that utilize a wide variety of semiconductor materials. Examples of such materials include, but are not limited to, elementary semiconductor materials such as silicon (Si) or germanium (Ge), group IV compound semiconductor materials such as silicon carbide (SiC) or silicon germanium (SiGe), binary, ternary or quaternary III-V semiconductor materials such as gallium nitride (GaN), gallium arsenide (GaAs), gallium phosphide (GaP), indium phosphide (InP), indium gallium phosphide (InGaPa), aluminum gallium nitride (AlGaN), aluminum indium nitride (AIInN), indium gallium nitride (InGaN), aluminum gallium indium nitride (AIGaInN) or indium gallium arsenide phosphide (InGaAsP), etc.

The semiconductor dies disclosed herein may be configured as a vertical device, which refers to a device that conducts a load current between opposite facing main and rear surfaces of the die. Alternatively, the semiconductor dies may be configured as a lateral device, which refers to a device that conducts a load current parallel to a main surface of the die.