Low CTE and low elastic modulus encapsulant for low-stress electronic packaging

Abstract

An encapsulant (100) for an electronic package (110), wherein the encapsulant (100) comprises an electrically insulating matrix material (102) and stress-inhibiting filler particles (104) in the matrix material (102) having a thermal expansion coefficient of no more than 6 ppm / K and a modulus of elasticity of no more than 4 GPa.

Description

BackgroundTechnical area

[0001] Various embodiments generally relate to an encapsulant and to a housing. Description of the state of the art

[0002] A conventional package may include a semiconductor component mounted on a carrier, such as a leadframe structure, may be electrically connected by a bonding wire extending from the semiconductor component to the carrier, and may be molded using a molding compound as an encapsulant.

[0003] Power cycling is the testing of a package, device, or module by repeatedly cycling it from the off to the on state according to a defined pattern of time, maximum allowable device temperature, and electrical current. It usually results in the destruction of the package, device, or module through the fracture of key interfaces or connections of the package, device, or module due to coefficient of thermal expansion (CTE)-induced material stress fractures induced by the inhomogeneous temperature distribution within the package, device, or module, i.e., material fatigue.

[0004] The power cycling performance of packages, devices, and modules is becoming a key performance indicator. It would be desirable to achieve appropriate power cycling behavior. More generally, the electrical reliability of such packages can be a concern. Summary

[0005] There may be a need for an enclosure with high electrical reliability.

[0006] According to an exemplary embodiment, an encapsulant for an electronic package is provided, the encapsulant comprising an electrically insulating matrix material and stress-relieving filler particles in the matrix material having a coefficient of thermal expansion value of not more than 6 ppm / K and a modulus of elasticity value of not more than 4 GPa.

[0007] According to a further exemplary embodiment, a package is provided comprising a carrier, an electronic component mounted on the carrier, and an encapsulant at least partially encapsulating the electronic component and the carrier, wherein a value of the elastic modulus of the encapsulant multiplied by an absolute value of a difference between values ​​of the thermal expansion coefficient of the encapsulant and the electronic component is less than 372 GPa*ppm / K.

[0008] According to an exemplary embodiment, an encapsulant (e.g., a molding compound) is provided for encapsulating an electronic housing (in particular, for encapsulating an electronic component mounted on a carrier). A matrix material may form the base of the encapsulant and may be electrically insulating, thereby preventing unwanted current flow between an outer side and an inner side of the encapsulant (e.g., to and / or from an encapsulated electronic component of a corresponding housing).Advantageously, stress-relieving filler particles (for example, porous zirconium tungstate particles) are incorporated into the matrix, which have a coefficient of thermal expansion (CTE) of no more than 6 ppm / K and a Young's modulus of no more than 4 GPa (for example, porous zirconium tungstate can have a CTE of -7 ppm / K and a Young's modulus of 0.85 GPa). In short, the stress-relieving filler particles added to the matrix material can be characterized by a soft property with low stiffness (as a result of the low Young's modulus) in combination with a very small positive or even negative CTE, which leads to at least greatly limited thermal expansion of the encapsulant in the event of a temperature increase.Consequently, thermal stress can be greatly reduced while simultaneously imparting a soft property to the stress-relieving filler particles and consequently to the encapsulant as a whole. In combination with a matrix material of the encapsulant, for example, an epoxy resin, this can provide an encapsulant that experiences very limited stress, so that an encapsulated electronic component (for example, a semiconductor chip, which may be made essentially of silicon, for example) of a package can be highly resistant to damage or failure during a power cycle and during use, even under harsh conditions. Consequently, a package encapsulant with high electrical reliability can be obtained.

[0009] According to another exemplary embodiment, a housing with an encapsulated electronic component (such as a semiconductor chip, for example, made essentially of silicon) is provided. Advantageously, the encapsulant is designed to have a value of elastic modulus that, multiplied by an absolute value of a difference between CTE values ​​of the encapsulant and the electronic component, is less than 372 GPa*ppm / K. In other words, the aforementioned design rule corresponds to a sufficiently small stress-describing index, reflecting a combined soft encapsulation with low stiffness and a simultaneously small CTE mismatch between the materials of the encapsulant and the electronic component.During significant temperature changes (e.g., due to heating of the package), thermal expansion of the package components can generate thermal stress. The package may be vulnerable to damage, particularly if there is a significant difference in the CTE values ​​of the individual components. Generally, the resin of an encapsulant may have a significantly higher CTE value (e.g., more than or even much higher than 10 ppm / K) than the semiconductor (especially silicon) material of the electronic component (e.g., 4-5 ppm / K).According to the above design rule, the encapsulant can be designed such that the CTE mismatch, or difference in CTE values, between the encapsulant and the electronic component is sufficiently small to obtain a sufficiently low stress index, which makes it possible to suppress or prevent failure or damage during a power cycle or during use under harsh conditions. In short, if the thermal stress is kept sufficiently small by a sufficiently low CTE mismatch (i.e., difference in CTE values ​​between the encapsulant and the electronic component) and the encapsulant is designed to be soft enough to buffer thermal stress, the package can be reliably prevented from failure or damage.Thus, a sufficiently low stress-describing index, as reflected by the design rule described above, can lead to high electrical reliability. For example, the stress-describing index can be determined by separately measuring the CTE values ​​of the encapsulant and the electronic component, as well as the elastic modulus value of the encapsulant. Description of further exemplary embodiments

[0010] Further exemplary embodiments of the encapsulant and the housing are explained below.

[0011] In the context of the present application, the term "encapsulant" may in particular refer to a material, a structure, or an element that surrounds or is intended to surround at least part of an electronic component and at least part of a carrier of a housing. In this context, an encapsulant may provide mechanical protection and electrical insulation and optionally contribute to heat dissipation during operation. In particular, the encapsulant may be electrically insulating, for example a molding compound. A molding compound may comprise a matrix of a flowable and curable material, in particular a resin, optionally one or more additives, and optionally filler particles embedded therein. As an alternative to a molding compound (for example based on epoxy resin), the encapsulant may also be a potting compound (for example based on an epoxy).

[0012] In the context of the present application, the term "encapsulant for electronic housing" may, in particular, mean that the encapsulant is suitable and configured for encapsulating one or more components of an electronic housing, in particular an electronic component and / or a carrier. This may, in particular, require sufficient electrical insulation capability of the encapsulant to prevent the flow of electrical current through the encapsulant. Furthermore, this may require proper adhesion of the encapsulant to one or more components of the housing (in particular an electronic component and / or a carrier), which may be achieved by a suitable matrix material and / or one or more suitable additives of the encapsulant.

[0013] In the context of the present application, the term "electrically insulating matrix material" may, in particular, refer to a material in which the voltage-reducing filler particles are embedded. The electrically insulating properties of the matrix material may be so pronounced that no significant amount of electrical current can flow through or along the encapsulant. The matrix material may comprise a resin, in particular a polymer resin. For example, such a polymer resin may be an epoxy resin. For example, the matrix material may be made of a curable material such as epoxy resin, which can be cured during an encapsulation process. Filler particles within the matrix material can fine-tune the package properties.

[0014] In the context of the present application, the term “filler particles” may in particular refer to a substance (in particular powdery or granular) that fills internal volumes in a surrounding medium such as a matrix.

[0015] In the context of the present application, the term "stress-relieving filler particles" may, in particular, refer to filler particles specifically configured to inhibit stress, in particular thermal stress, in an interior of the encapsulant and / or between the encapsulant and an encapsulated electronic component. In particular, the stress-relieving filler particles may be provided with a sufficiently low elastic modulus and a sufficiently low thermal expansion coefficient to comply, in combination, with the above-mentioned design rules. In particular, stress-relieving filler particles may be provided as nanoparticles or microparticles. Stress-relieving filler particles may have identical dimensions or may be provided with a distribution of particle sizes.Such a particle size distribution may be preferred as it may enable improved filling of gaps within the interior of the encapsulant. The stress-relieving filler particles may be modified, coated, and / or treated to improve adhesion and / or chemical bonding to the surrounding matrix.

[0016] In the context of the present application, the term "coefficient of thermal expansion" (CTE) may specifically refer to a parameter that describes the rate at which a material expands with increasing temperature. For many materials, this CTE value is positive, while it may also be negative for certain other materials. In this context, thermal expansion may refer to the tendency of matter to change its shape, area, volume, and density in response to a change in temperature. The relative expansion (also referred to as strain) divided by the change in temperature may be referred to as the material's coefficient of thermal expansion. The value of the coefficient of thermal expansion may be expressed in ppm / K.

[0017] In the context of the present application, the term "elastic modulus" may specifically refer to a mechanical property of solid materials that measures tensile or compressive stiffness when a force is applied in a longitudinal direction. The elastic modulus may be defined as the ratio of the stress (i.e., force per unit area) applied to the object and the resulting axial strain (i.e., displacement or deformation) in the linear elastic range of the material. The value of the elastic modulus may be expressed in GPa.

[0018] In the context of the present application, the term "housing" may, in particular, refer to an electronic device that may comprise one or more electronic components mounted on a (particularly partially or fully electrically conductive) carrier. The components of the housing may be at least partially encapsulated by an encapsulant. Optionally, one or more electrically conductive connecting elements (such as metallic pillars, bumps, bond wires, and / or clips) may be implemented in a housing, for example, for electrically coupling and / or mechanically supporting the electronic component.

[0019] In the context of the present application, the term "carrier" may in particular refer to a support structure (which may be at least partially electrically conductive) that serves as mechanical support for the electronic component(s) to be mounted thereon and that may also contribute to the electrical connection between the electronic component(s) and the periphery of the housing. In other words, the carrier may fulfill a mechanical support function and optionally an electrical connection function. A carrier may comprise or consist of a single part, multiple parts connected via encapsulation or other housing components, or a subassembly of carriers. If the carrier forms part of a leadframe structure, it may be or comprise a die pad.For example, such a carrier may be a leadframe structure (e.g., made of copper), a DAB (Direct Aluminum Bonding) substrate, a DCB (Direct Copper Bonding) substrate, etc. Furthermore, the carrier may also be configured as an AMB (Active Metal Brazing) substrate. At least a portion of the carrier may also be encapsulated together with the electronic component by the encapsulant.

[0020] In the context of the present application, the term "electronic component" may in particular encompass a semiconductor chip (in particular a power semiconductor chip), an active electronic device (such as a transistor), a passive electronic device (such as a capacitor or an inductor or an ohmic resistor), a sensor (such as a microphone, a light sensor, or a gas sensor), an actuator (such as a loudspeaker), and a microelectromechanical system (MEMS). However, in other embodiments, the electronic component may also be of a different type, such as a mechatronic element, in particular a mechanical switch, etc. In particular, the electronic component may be a semiconductor chip having at least one integrated circuit element (such as a diode or a transistor in a surface portion thereof).The electronic component may be a bare die or may be pre-packaged or encapsulated. Semiconductor chips implemented according to exemplary embodiments may be formed using silicon technology, gallium nitride technology, silicon carbide technology, etc.

[0021] The parameter values ​​mentioned in this application (in particular the thermal expansion coefficient and the elastic modulus) may be in the temperature range from -40 °C to 250 °C, in particular in the temperature range from -40 °C to 85 °C, and in particular in the temperature range from 0 °C to 70 °C. Furthermore, amounts of components of an encapsulant stated in percent (%) in the present application may indicate weight percent.

[0022] In one embodiment, the stress-relieving filler particles have a Young's modulus of no more than 1 GPa. Such very soft stress-relieving filler particles can efficiently reduce stress in the encapsulant and the housing. Even in the case of stress due to a certain CTE mismatch, such stress-relieving filler particles can act as a mechanical buffer.

[0023] In one embodiment, the stress-relieving filler particles have a coefficient of thermal expansion of no more than 4 ppm / K. Since said CTE value is significantly lower than that of usable resin materials, especially usable epoxy resin materials, and may also be smaller than the CTE value of the electronic component (e.g., made essentially of silicon), such stress-relieving filler particles can efficiently reduce the CTE mismatch and can therefore greatly suppress thermal stress.

[0024] In one embodiment, the stress-relieving filler particles have a negative coefficient of thermal expansion. Stress-relieving filler particles with a negative CTE can actually contract upon heating and can therefore highly efficiently reduce the CTE mismatch by leading to a strong reduction in the encapsulant CTE, which is typically significantly larger than that of the electronic component.

[0025] In one embodiment, the stress-relieving filler particles are porous. Porous stress-relieving filler particles may include pores within them. Illustratively, porous particles may exhibit a lower CTE and / or a lower elastic modulus than comparable continuously solid particles. It is believed that by not only manufacturing the stress-relieving filler particles from a material with a low CTE and a low elastic modulus, but also by creating porosity within the stress-relieving filler particles, the particles may be made even softer. Thus, making the stress-relieving filler particles porous may further reduce their stiffness and consequently lead to highly advantageous properties with respect to power cycling behavior.

[0026] In one embodiment, the stress-relieving filler particles are closed porous particles. The closure of porous stress-relieving filler particles can be achieved by coating. If the pores of the porous stress-relieving filler are closed, particularly from their surroundings, the porous properties can be fully maintained even if the porous stress-relieving filler particles are incorporated into a still-flowable resin matrix of the encapsulant. In other words, resin can then be prevented from flowing into and filling the pores, which could reduce the degree of porosity.

[0027] Additionally or alternatively, it may also be possible to use open porous stress-relieving filler particles, which can lead to a particularly simple manufacturing process.

[0028] In one embodiment, the porous stress-relieving filler particles have a pore volume to total particle volume ratio in a range of 1% to 80%, particularly in a range of 1% to 40%. For example, the ratio may be in a range of 10% to 40%. In this context, the mentioned percentage of porosity (more precisely, the volume fraction of porosity) may be defined as the fraction of the volume of the stress-relieving filler particles attributed to the pores. Preferably, the porous stress-relieving filler particles may have a porosity in the range of 1% to 40%, which is defined as the fraction of the apparent specific volume of the stress-relieving filler particles attributed to the pores.

[0029] In one embodiment, the stress-relieving filler particles have a functional coating. Illustratively speaking, coating (especially porous) stress-relieving filler particles can allow a classic interface to be maintained between filler particles and a surrounding resin matrix. By coating an outer surface of the stress-relieving filler particles with a functional coating, the properties of the stress-relieving filler particles can be adjusted or fine-tuned. For example, the functional coating can be selected to enhance the stress-relieving function provided by the stress-relieving filler particles.For this purpose, it is possible, for example, to apply a functional coating that reduces the CTE mismatch between encapsulant and encapsulated electronic component and / or reduces the value of the elastic modulus of the stress-relieving filler particles.

[0030] In one embodiment, the functional coating comprises an insulator. Thus, the functional coating of the stress-relieving filler particles can be electrically insulating, thereby improving the dielectric properties of the encapsulant. This, in turn, can improve the electrical reliability of the package as a whole.

[0031] Additionally or alternatively, the functional coating comprises an adhesion promoter. In the context of the present application, the term "adhesion promoter" can, in particular, refer to any material and / or substance that improves the adhesion between the stress-relieving filler particles, on the one hand, and other components of the encapsulant (for example, a matrix resin) and / or other components of the housing (in particular, the electronic component and / or the carrier), on the other hand. In particular, such an adhesion promoter can act as an interface between the stress-relieving filler particles and their surroundings to improve the adhesion therebetween.

[0032] In one embodiment, the adhesion promoter of the functional coating of the stress-inhibiting filler particles comprises silane and / or a morphological adhesion promoter.

[0033] Thus, the adhesion promoter of the functional coating of the stress-relieving filler particles can be a morphological adhesion promoter, i.e., an adhesion promoter with a morphological structure. In the context of the present application, the term “morphological structure” can, in particular, refer to a structure that has a topology and / or a porous structure and / or is shaped to increase the bonding surface, thereby promoting adhesion. Furthermore, the morphology of a morphological adhesion promoter can bring about advantageous mechanical interlocking between material of the morphological adhesion promoter and an environment of the stress-relieving filler particles. In other words, a morphological structure promotes adhesion due to its shape, rather than just promoting adhesion due to its chemistry.However, it is also possible for a morphological structure to be synergistically constructed from material that, due to its intrinsic properties, promotes adhesion in addition to its shape. In particular, a morphological coupling agent can be an inorganic porous material. For example, the presence of a morphological structure between the stress-relieving filler particles and their surroundings can additionally promote the bond between the stress-relieving filler particles and the surroundings to further improve reliability. Very advantageously, the coupling agent can promote adhesion at least partly due to its morphology. Thus, specific shaping and, in particular, enlarging the inner surface of the coupling agent can improve the adhesion between the stress-relieving filler particles and their surroundings, which is mediated by the morphological coupling agent.

[0034] In one embodiment, the morphological coupling agent comprises at least one of a metallic structure, an alloy structure, a chromium structure, a vanadium structure, a molybdenum structure, a zinc structure, a manganese structure, a cobalt structure, a nickel structure, a copper structure, a flame-deposited structure, a roughened metal structure (in particular, a roughened copper structure or a roughened aluminum oxide structure), and any oxide, nitride, carbide, and selenide of any of the structures. All structures may comprise or consist of these metals and / or their alloys. Additionally, these structures may comprise or consist of these metals and their alloy oxides. In particular, single oxides and mixed oxides are possible in various embodiments.However, other materials and structures can also be used for the morphological coupling agent. The flame-deposited structure mentioned above can be silicon dioxide, any titanium oxide (such as TiO2, TiO, TiO3). y ), etc. Any organometallic precursor that can be combusted in a mixture with a combustion gas such as propane or butane and forms the specific metal oxide can be used. In particular, a morphological coupling agent can be formed using atomic layer deposition (ALD), chemical vapor deposition (CVD), etc.

[0035] In another embodiment, the coupling agent of the stress-relieving filler particles can be an organic coupling agent, such as silane. Such an organic coupling agent can promote adhesion due to its chemical properties.

[0036] In one embodiment, the stress-relieving filler particles comprise at least one material selected from zirconium tungstate, porous silica, borosilicate glass, β-eucryptite, α-ZrW2O8, β-ZrW2O8, Cd(CN)2, ReO3, (HfMg)(WO4)3, Sm 2,75 C 60 , Bi 0,95 La 0,05 NiO3, Invar (Fe-36Ni), Invar (Fe3Pt), Tm2Fe 16 Cr, copper oxide nanoparticles and Mn3Cu 0,53 Ge 0,47 N . Zirconium tungstate, α-ZrW2O8, ReO3, (HfMg)(WO4)3, Invar (Fe-36Ni), Invar (Fe3Pt), and copper oxide nanoparticles may be particularly preferred. These materials, either as such or in a porous variant and / or with a suitable coating, can meet the requirements of a low or even negative CTE value and can also exhibit a low elastic modulus, especially if they are porous.

[0037] In one embodiment, the stress-relieving filler particles have a size of less than 100 µm, particularly in a range from 1 µm to 30 µm. At such sizes, the stress-relieving filler particles are compatible with the homogeneous properties of the encapsulant.

[0038] In one embodiment, the stress-relieving filler particles are round. However, the stress-relieving filler particles can also have other geometries. For example, the shape of the stress-relieving filler particles can be random, spherical, cuboid, flake, and film.

[0039] In one embodiment, the encapsulant additionally comprises functional filler particles that impart at least one additional function to the encapsulant. For example, the at least one additional function provided by the functional filler particles can be an increase in the thermal conductivity of the encapsulant, an increase in the hardness of the encapsulant, and / or a reduction in the mismatch in the coefficient of thermal expansion between the encapsulant and a semiconductor material, in particular silicon or silicon carbide. Thus, the encapsulant can further comprise functional filler particles in the matrix material, i.e., at least a second type of filler particles in addition to the stress-relieving filler particles. By selecting the functional filler particles, the physical and / or chemical properties of the encapsulant can be adjusted.Such properties may include the thermal expansion coefficient, thermal conductivity, dielectric properties, etc. The functional filler particles can thus be added to fine-tune the physical, chemical, etc., properties of the encapsulant. For example, the functional filler particles may increase the thermal conductivity of the encapsulant to efficiently remove heat from an interior of the package (such heat may be generated by a semiconductor component, for example, when embodied as a power semiconductor chip). It is also possible for the functional filler particles to provide improved dielectric decoupling between such a semiconductor component and the environment of the package.

[0040] In one embodiment, functional filler particles are selected from a group consisting of aluminum hydroxide, magnesium hydroxide, zirconium dioxide, calcium carbonate, calcium silicate, talc, clay, carbon fiber, glass fiber, and mixtures thereof. However, other functional filler materials are possible depending on the requirements of a particular application. Functional filler particles (e.g., Al2O3, Si3N4, BN, AlN, diamond, etc.), for example, to improve thermal conductivity, can also be used. In particular, organic particles can be used as functional fillers (e.g., functional fillers can also comprise or consist of polymers or polymer blends, such as epoxies, polyethylene, polypropylene, etc.).

[0041] In one embodiment, the total amount of filler particles (in particular, stress-relieving filler particles and optionally additionally one or more additional types of functional filler particles) of the encapsulant relative to the encapsulant as a whole may be in a range of 60 weight percent to 95 weight percent, in particular in a range of 70 weight percent to 90 weight percent. Such a filler content relative to the matrix material (in particular, resin material) may enable the desired overall properties of the encapsulant as a whole to be achieved.

[0042] In one embodiment, the matrix material comprises an epoxy resin, silicone, a bismaleimide, and / or an imide. Epoxy resin can be a suitable matrix material for an epoxy molding compound (EMC). Silicone can form the basis of a gel-like encapsulant for the casting resin.

[0043] In one embodiment, the encapsulant is configured as a molding compound, in particular as an epoxy-based molding compound. Thus, various types of molding compounds can be used, such as silicone molding compound, bismaleimide molding compound, imide molding compound, etc. Molding can refer to a manufacturing process for shaping liquid or flexible raw material using a rigid tool referred to as a mold. Thus, encapsulation of the one or more electronic components, in particular semiconductor components, of the semiconductor package can be achieved by molding. Consequently, the encapsulant can comprise a curable matrix (for example, based on epoxy resin) with filler particles therein.

[0044] In one embodiment, the encapsulant is configured as a potting compound, in particular as an epoxy-based casting resin. In particular, casting can refer to a process for filling an electronic assembly with a solid or gel-like compound, for example, for high-voltage assemblies. This can suppress or exclude gaseous phenomena such as corona discharge, can be performed for shock and vibration resistance, and / or can be performed to exclude water, moisture, etc.

[0045] In one embodiment, the encapsulant of the housing comprises an electrically insulating matrix material and stress-relieving filler particles, for example, having a thermal expansion coefficient of no more than 6 ppm / K and / or a Young's modulus of no more than 4 GPa, in the matrix material. In general, the encapsulant of the housing can be configured according to any of the above-mentioned embodiments.

[0046] In preferred embodiments of the package, the value of the elastic modulus of the encapsulant multiplied by the absolute value of the difference between the values ​​of the thermal expansion coefficient of the encapsulant and the electronic component is less than 200 GPa*ppm / K, more preferably less than 100 GPa*ppm / K. Thus, the elastic modulus and / or the CTE values ​​of the encapsulant components can be adjusted to obtain the stress-indicating index values ​​mentioned, which can further improve the power cycling properties of the encapsulant and package compared to conventional approaches. Table 2 provides an example of how this can be achieved.A sufficiently large amount of stress-relieving filler particles, the provision of porous stress-relieving filler particles with a sufficiently large porosity percentage, and a selection of stress-relieving filler particles with a sufficiently low (preferably negative) CTE value and / or low value of the elastic modulus are measures that can be taken to achieve such very small stress-describing index values.

[0047] In one embodiment, the package is configured as a power module, for example, a molded power module, such as a semiconductor power package. For example, an exemplary embodiment of the package may be an intelligent power module (IPM). Another exemplary embodiment of the package is a dual in-line package (DIP).

[0048] In one embodiment, the package is configured as one of the group consisting of a power module connected to a lead frame, a transistor outline (TO) package, a quad flat no-leads package (QFN) package, a small outline (SO) package, a small outline transistor (SOT) package, and a thin small outline package (TSOP). Packages for sensors and / or mechatronic devices are also possible embodiments. Furthermore, exemplary embodiments may also relate to packages that function as nanobatteries or nanofuel cells or other devices with chemical, mechanical, optical, and / or magnetic actuators. Therefore, according to an exemplary embodiment, the package is fully compatible with standard package concepts (in particular, fully compatible with standard TO package concepts) and externally appears as a conventional package, which is very convenient for the user.

[0049] In one embodiment, the electronic component is a semiconductor power chip. Thus, the semiconductor component (such as a semiconductor chip) can be used for power applications, for example in the automotive sector, and can, for example, comprise at least one integrated insulated-gate bipolar transistor (IGBT) and / or at least one transistor of another type (such as a MOSFET, a JFET, etc.) and / or at least one integrated diode. Such integrated circuit elements can, for example, be manufactured using silicon technology or be based on wide-bandgap semiconductors (such as silicon carbide). A semiconductor power chip can comprise one or more field-effect transistors, diodes, inverter circuits, half-bridges, full-bridges, drivers, logic circuits, other devices, etc.

[0050] In one embodiment, the housing comprises a plurality of electronic components, in particular semiconductor components, which are encapsulated by the housing encapsulant. Thus, the housing can comprise one or more semiconductor components (e.g., at least one passive component, such as a capacitor, and at least one active component).

[0051] In one embodiment, the electronic component is a semiconductor chip, for example, comprising silicon. Particularly when the electronic component is embodied as a semiconductor chip made predominantly of silicon or silicon carbide material, the CTE mismatch with an epoxy-based encapsulant material can be very pronounced. Thus, especially under such circumstances, the provision of stress-inhibiting filler particles and / or an encapsulant with a sufficiently low stress-describing index value can be extremely advantageous.

[0052] For example, the stress-relieving filler particles may be subjected to a coating and / or surface treatment process before the stress-relieving filler particles are mixed with the matrix material.

[0053] In particular, it may be possible to mix the stress-inhibiting filler particles with the matrix material before or after adding additional filler particles and / or at least one further additive.

[0054] A semiconductor substrate, in particular a silicon substrate, can be used as the substrate or wafer that forms the basis of the electronic component(s). Alternatively, a silicon oxide or other insulating substrate can be provided. It is also possible to implement a germanium substrate or a III-V semiconductor material. For example, exemplary embodiments can be implemented using GaN or SiC technology.

[0055] The above and other objects, features and advantages will become apparent from the following description and the appended claims, taken in conjunction with the accompanying drawings, in which like parts or elements are designated by like reference numerals. Short description of the drawings

[0056] The accompanying drawings, which are included to provide a further understanding of example embodiments and constitute a part of the specification, illustrate example embodiments.

[0057] In the drawings: Fig. 1 illustrates a cross-sectional view of an encapsulant according to an exemplary embodiment. Fig. 2 illustrates a cross-sectional view of a housing according to an exemplary embodiment. Fig. 3 illustrates various types of stress-relieving particles of an encapsulant according to an exemplary embodiment. Fig. 4 illustrates a cross-sectional view of a housing according to an exemplary embodiment. Fig.5 illustrates a cross-sectional view of a housing according to another exemplary embodiment. Detailed description

[0058] The illustration in the drawing is schematic and not to scale.

[0059] Before describing exemplary embodiments in more detail with reference to the figures, some general considerations are summarized based on which exemplary embodiments have been developed.

[0060] Power cycling performance of packages can be critical. A common failure mode can be breakage of key interfaces. One factor contributing to power cycling failure can be an inhomogeneous temperature distribution within the device due to CTE-induced material stress fractures, i.e., material fatigue. Thus, it may be desirable to have an encapsulation with a controlled or tunable low elastic modulus. Additionally, a controlled CTE delta at a critical die interface can be helpful.

[0061] It has been recognized that the behavior of a package during power cycling, as discussed above, is determined by several material properties of the encapsulation, including the CTE and Young's modulus values. Both factors can be temperature-dependent and not discrete points.

[0062] It would be desirable to have an encapsulation with a controlled or tunable low elastic modulus to enable longer power cycling lifetimes and / or to tune the encapsulation to a desired power cycling regime (for example, depending on a temperature difference or temperature range or an upper temperature limit in the power cycling).

[0063] Problems with conventional molding compounds are that they are loaded with filler particles (e.g., aluminum oxide particles) that have very high elastic modulus values ​​and are consequently extremely stiff and induce high stress during power cycling. At high filler loadings, this can lead to molding compounds with a high bonding elastic modulus value, for example, well over 20 GPa.

[0064] According to an exemplary embodiment, an encapsulant (such as a molding compound) for an electronic package (particularly for a semiconductor package comprising silicon) may incorporate stress-relieving filler particles (such as porous zirconium tungstate) in a resin matrix (e.g., epoxy resin, which may also include functional filler particles such as alumina). Advantageously, the stress-relieving filler particles may be selected to have a CTE value of no more than 6 ppm / K and a Young's modulus value of no more than 4 GPa. As a result, a softer encapsulant may be obtained that is better able to buffer stress. Such low-stiffness properties may be synergistically combined with a low CTE value, which limits thermal expansion and thus thermal stress.As a result, an encapsulant can be provided that does not cause excessive stress when encapsulating the electronic component, such as a semiconductor component (e.g., comprising silicon). Consequently, the risk of damage or failure during a power cycle can be reduced, and improved electrical reliability can be achieved.

[0065] According to another exemplary embodiment (which may or may not be combined with the previously described embodiment), an electronic component (such as a semiconductor chip comprising, for example, silicon) may be encapsulated by an encapsulant to form a package. Advantageously, the product of the net, average, or effective value of the elastic modulus of the encapsulant and an absolute value of a difference between the net, average, or effective CTE values ​​of the encapsulant and the electronic component may be below 372 GPa*ppm / K. The above-mentioned limited parameter range may indicate a reasonably low degree of stress, as it may reflect softness of the encapsulant in combination with a sufficiently small CTE mismatch between the encapsulant and the encapsulated electronic component.Given the aforementioned design rule that the stress-describing index is below 372 GPa*ppm / K, the stress can be significantly reduced compared to conventional approaches, for example, by at least 30%. A suitably manufactured housing can thus be protected from failure or damage during a power cycle.

[0066] A model for stress in a package comprising an encapsulant (such as a molding compound) encapsulating an electronic component (such as a silicon die) may be based on a stress index (SI) that reflects the combined effects of CTE values ​​(CTE), temperature (T), glass transition temperature (Tg) of the encapsulant, and elastic modulus (E). Such a model may be based on the following equation: SI=(CTE1−CTEx)(T−Tg)E1+(CTE2−CTEx)(T−175)E2

[0067] In this equation, index 1 (corresponding to room temperature) and index 2 (corresponding to high temperature) refer to the molding compound, while index x refers to the silicon die.

[0068] To estimate the stress in a semiconductor-to-encapsulant power cycle in a further simplified model, the scenario can be modeled as follows for the regime below Tg: Isothermal conditions are assumed directly near the semiconductor, meaning that the epoxy molding compound and the semiconductor die can be assumed to be at the same temperature. Upon heating, the semiconductor die and the encapsulant can experience CTE-driven length and volume changes. Since the semiconductor die and the encapsulant are rigidly attached, this can induce stress at the interface according to Hooke's law.

[0069] Consequently, the voltage on the top of the semiconductor die can be proportional to: Voltage~(CTEncapsulation−CTEthe)Encapsulation

[0070] According to an exemplary embodiment, the design of the encapsulant components may be such that the stress-describing index is sufficiently low. As described below with reference to Example 1, a power-cycling-resistant housing according to an exemplary embodiment may utilize an epoxy molding compound with a stress index (ΔCTE x E) less than 70% of that of conventional approaches. In particular, this may involve providing stress-inhibiting filler particles with a sufficiently low elastic modulus and a sufficiently low CTE.

[0071] According to an exemplary embodiment, a tunable epoxy molding compound with low CTE and low elastic modulus can be provided, resulting in reduced package stress under power cycling.

[0072] According to exemplary embodiments, it may be possible to produce an epoxy molding compound with negative thermal expansion (NTE) particles, i.e., stress-relieving filler particles with a negative coefficient of thermal expansion (CTE). This may make it possible to improve power cycling performance by partially incorporating stress-relieving filler particles with a low CTE or negative CTE and a low elastic modulus into an epoxy molding compound. Preferably, porous stress-relieving filler particles may be used in conjunction to further lower elastic modulus and CTE. For example, zirconium tungstate filler particles may be coated or treated prior to incorporation. For example, the stress-relieving filler particles may be coated with an adhesion promoter or an insulating compound that is different from the epoxy compound.For example, the stress-relieving filler particles are added during epoxy molding compound production, for example, before or after the addition of other fillers (such as functional filler particles) and / or other components or additives of the molding compound formulation.

[0073] According to exemplary embodiments, it may be possible to partially admix stress-relieving filler particles with low CTE and low elastic modulus, in particular with negative CTE, and / or in conjunction with (preferably closed) porous particles to further reduce the elastic modulus and / or CTE. A preferred example of a material for the stress-relieving filler particles is zirconium tungstate, preferably porous and / or coated. Another embodiment of the stress-relieving filler particles is the use of porous silica particles.

[0074] In various embodiments, the stress-relieving filler particles can have any shape, but are preferably round. They can have particle sizes below 100 µm, for example, in a range from 1 µm to 30 µm. For example, the stress-relieving filler particles can be porous, for example, in the range of up to 80%, but preferably in a range from 1% to 40%. In various embodiments, open-porous or closed-porous stress-relieving filler particles can be used, but preferably closed-porous ones. For example, the stress-relieving filler particles of the encapsulant can have a compound CTE of less than 4 ppm / K, for example, in the range from 0°C to 150°C. The stress-relieving filler particles can have an elastic modulus of less than 1 GPa.They can optionally be coated or treated prior to admixture, for example with an adhesion promoter (e.g. silanes or a morphological adhesion promoter) and / or an insulating compound different from the epoxy compound.

[0075] Alternatively, properly treated glass (or silica), preferably properly treated borosilicate glasses, can be used as stress-relieving filler particles.

[0076] In one embodiment, the stress-relieving filler particles can be added during epoxy molding compound preparation before or after adding the other fillers and component substances to the molding compound formulation.

[0077] According to one embodiment, the loading of the stress-relieving filler particles may be in a range of up to 40% by volume, but preferably in a range of 1% to 15%. For example, a weight percentage of the stress-relieving filler particles relative to the total weight of the encapsulant may be below 40%, preferably in a range of 1% to 15%. Example 1:

[0078] The following justification for the upper limit of 372 GPa*ppm / K for the product of the encapsulant's elastic modulus value multiplied by the absolute value of the difference between the encapsulant's and the electronic component's coefficient of thermal expansion values ​​is provided. For example, an epoxy molding compound (EMC), see the first and third parameter rows of Table 1 and the first parameter row of Table 2, with 20% resin and 80% functional silicon dioxide filler particles, may have an elastic modulus value of 48.4 GPa and a thermal expansion coefficient of 16 ppm / K. An electronic component embodied as a silicon chip may have a thermal expansion coefficient of 5 ppm / K.Thus, a product of the encapsulant's elastic modulus value multiplied by the absolute value of the difference between the CTE values ​​of the encapsulant and the electronic component can be equal to 48.4 GPa*(16-5) ppm / K = 532 GPa*ppm / K. For hybrid rule blends, the following considerations apply: 70% of this product can be 372 GPa*ppm / K. This can, in one embodiment, correspond approximately to an admixture of 15% stress-relieving filler particles embodied as 40% porous zirconium tungstate, as can be seen from the first through third parameter rows of Table 1 and the second parameter row of Table 2. Table 1: Components of an encapsulant material Elastic modulus [GPa] CTE[ppm / K] Matrix: resin 2 60 Stress-inhibiting filler particles: 40% porous zirconium tungstate 0,85 -7 Functional filler particles: silicon dioxide 60 5 Table 2: Parameter values ​​for different amounts of components of an encapsulant Resin[] Porous zirconium tungstate [%] Silicon dioxide [%] Elastic modulus of encapsulant1 [GPa] CTE encapsulation agent1 [ppm / K] stress-describing index [GPa*ppm / K] 20 0 80 48,4 16,0 532,4 20 15 65 39,5 14,2 363,7 20 25 55 33,6 13,0 268,9 20 45 35 21,8 10,6 122,0 20 55 25 15,9 9,4 69,8 20 65 15 10,0 8,2 31,8

[0079] More specifically, based on the values ​​of elastic modulus and CTE for the individual components of the encapsulant according to Table 1, averaged values ​​of elastic modulus and CTE for the encapsulant can be calculated, see Table 2.

[0080] For example, regarding the estimation of an average value of the elastic modulus, an averaged or effective value of the elastic modulus (Ecomposite) for a composite, such as an encapsulant, comprising several components, each having a respective value of the elastic modulus (Econstituent), can be estimated based on the rule of mixtures (VFconstituent can denote the volume fraction of the respective component of the composite): Ecomposite=∑Econstituent VFconstituent

[0081] For different percentages of stress-relieving filler particles, the stress-describing index explained above can be regulated or adjusted. With reference to the first parameter row of Table 2, a scenario without stress-relieving filler particles is shown, i.e., only matrix resin and functional filler particles made of silica are present. The second parameter row of Table 2 indicates that the addition of 15% stress-relieving filler particles in the form of 40% porous zirconium tungstate improves the stress-describing index by reducing it to approximately 70% of the conventional value of the first parameter row of Table 2. Further referring to the first and second parameter rows of Table 2, the amount of functional filler particles is reduced by the amount of added stress-relieving filler particles in Example 1 shown.As can be seen from the subsequent parameter rows of Table 2, larger amounts of stress-relieving filler particles can further improve the stress-describing index. The described Example 1 can make it possible to provide a highly suitable encapsulant by adjusting both CTE and elastic modulus values ​​due to the addition of the stress-relieving filler particles. All parameter rows of Table 2 refer to a constant total filler content of 80%, which can be advantageous with regard to the overall properties of the encapsulant. However, it may also be possible to adjust the total filler content when adjusting CTE and / or elastic modulus to improve properties related to power cycling.As can be seen from Table 2, the stress-describing index can be reduced by at least one order of magnitude due to the addition of the stress-inhibiting filler particles. Example 2:

[0082] The following example differs from the previous example in that 40% porous silica is used as stress-relieving filler particles (instead of 40% porous zirconium tungstate as in the previous Example 1) in the encapsulant, see Table 3. Table 3: Components of an encapsulant material Elastic modulus [GPa] CTE[ppm / K] Matrix: resin 2 60 Stress-inhibiting filler particles: 40% porous silicon oxide 30 5 Functional filler particles: silicon dioxide 60 5 Table 4: Parameter values ​​for different amounts of components of an encapsulant Resin[%] Porous silicon oxide[%] Silicon dioxide[%] Elastic modulus of encapsulant1 [GPa] CTE encapsulation agent1 [ppm / K] stress-describing index [GPa*ppm / K] 20 0 80 48,4 16,0 532,4 20 55 25 31,9 16, 0 350,9 20 65 15 28, 9 16, 0 317, 9

[0083] As can be seen from Table 4 (which shows corresponding information as Table 2 above), adding 55% of 40% porous silica to the encapsulant allows the target value for the stress-describing index of 372 GPa*ppm / K to be met. Adding 65% of 40% porous silica to the encapsulant allows even better values ​​for the stress-describing index to be obtained. As can be seen from Table 4, the addition of the stress-reducing filler particles can reduce the stress-describing index by approximately 40%.

[0084] Fig. 1 illustrates an encapsulant 100 according to an exemplary embodiment.

[0085] The schematically illustrated encapsulant 100 is for encapsulating an electronic package 110, such as the one shown in Fig. 2, Fig. 4 or Fig. 5 shown, configured.

[0086] As shown, the encapsulant 100 comprises an electrically insulating matrix material 102. For a molding compound type encapsulant 100, as used for the housing 110 of Fig. 2 or Fig. 4, the matrix material 102 may comprise an epoxy resin. For a potting-type encapsulant 100, such as that used for the housing 110 of Fig. 5, the matrix material 102 may comprise silicone.

[0087] Furthermore, the encapsulant 100 may include stress-relieving filler particles 104, which may have a coefficient of thermal expansion value of no more than 6 ppm / K, preferably no more than 4 ppm / K. As a result, the overall, average, or net CTE value of the encapsulant 100 may be greatly reduced by the presence of the stress-relieving filler particles 104. This may reduce a CTE mismatch in a package 110 with respect to silicon material of an encapsulated electronic component 103 and may therefore reduce thermal stress.

[0088] Furthermore, the elastic modulus of the stress-relieving filler particles 104 may be no more than 4 GPa, preferably no more than 1 GPa. This may impart a soft property to the encapsulant 100 and thus the ability to mechanically buffer thermal stress. For example, the stress-relieving filler particles 104 may comprise zirconium tungstate, porous silicon dioxide, and / or coated borosilicate glass.

[0089] As shown, at least some of the stress-relieving filler particles 104 may be porous, i.e., they may include pores 105. This may further reduce the stiffness of the stress-relieving filler particles 104 and may further improve the stress-buffering ability of the stress-relieving filler particles 104. At least some of the porous stress-relieving filler particles 104 may be closed porous particles with a coating 108. However, it is also possible for at least some of the porous stress-relieving filler particles 104 to be open porous particles without a coating 108. Porous stress-relieving filler particles 104 with a coating 108 may be preferred, as this may provide a defined interface with a surrounding resin of matrix material 102 and may keep the pores 105 unfilled or empty.Preferably, the porous stress-relieving filler particles 104 have a pore volume to total particle volume ratio in a range of 1% to 40%.

[0090] At least a portion of porous and / or non-porous stress-relieving filler particles 104 may include a functional coating 108, which may include an adhesion promoter (e.g., silane and / or a morphological adhesion promoter) and / or an insulator.

[0091] As shown, at least a portion of the preferably (but not necessarily) round stress-relieving filler particles 104 may have a maximum diameter or size D preferably in a range of 1 µm to 30 µm.

[0092] A weight percentage of the stress-relieving filler particles 104 with respect to a total weight of the encapsulant 100 may, for example, be up to 70%, preferably in a range of 10% to 40%.

[0093] In addition to the stress-relieving filler particles 104, the encapsulant 100 may comprise functional filler particles 106 to impart at least one additional function to the encapsulant 100. This at least one additional function may, for example, be an increase in the thermal conductivity of the encapsulant 100. For example, the functional filler particles 106 may comprise aluminum nitride. All functional filler particles 106 may be of the same type. Alternatively, different subtypes of functional filler particles 106 may be used, for example, a mixture of different materials.

[0094] A weight percentage of the stress-relieving filler particles 104 plus the functional filler particles 106 with respect to a total weight of the encapsulant 100 may, for example, be up to 95%, preferably in a range of 70% to 90%.

[0095] Apart from that, one or a plurality of further additives 112 (schematically shown in Fig. 1) may be added to the encapsulant 100 to further adjust its physical properties and provide dedicated functionality. For example, the additives 112 may include a dye, a voltage stabilizer, an antioxidant, an ultraviolet (UV) absorber, an adhesion promoter, etc.

[0096] Fig. 2 illustrates a cross-sectional view of a molded housing 110, which may be a power housing, according to an exemplary embodiment.

[0097] The illustrated housing 110 has a carrier 114, which may be, for example, a leadframe structure made of, for example, copper. An electronic component 103 may be mounted on the carrier 114. For example, the electronic component 103 may be a semiconductor die made, for example, using silicon technology or silicon carbide technology. For example, the electronic component 103 may be a semiconductor power chip. An electrically conductive connecting element 116, for example a bonding wire, may electrically couple the electronic component 103 to the carrier 114. An encapsulant 100, for example, the encapsulant 100 made of Fig. 1, can encapsulate the electronic component 103, the electrically conductive connecting element 116 and a part of the carrier 114.

[0098] Advantageously, the encapsulant 100 may be made of Fig.2 according to a design rule according to which a value of the elastic modulus of the encapsulant 100 multiplied by an absolute value of a difference between values ​​of the thermal expansion coefficient of the encapsulant 100 and the electronic component 103 is less than 372 GPa*ppm / K and preferably less than 200 GPa*ppm / K. This may make it possible to significantly reduce a stress-describing index, for example in a manner as described above for Example 1 or Example 2. For example, the encapsulant 100 may be as described above with reference to Fig. 1 described.

[0099] Fig. 3 illustrates various types of stress-relieving filler particles 104 of an encapsulant 100 according to an exemplary embodiment.

[0100] A stress-relieving filler particle 104a of a first type may be a continuously solid particle, for example made of a material with a negative thermal expansion (NTE), ie with a negative value of the CTE.

[0101] A second type of stress-relieving filler particle 104b may be a porous particle, in particular a porous NTE particle.

[0102] A third type of stress-relieving filler particle 104c may be a coated particle, in particular a coated porous NTE particle.

[0103] Any of the three shown and / or other types of stress-relieving filler particles 104a, 104b, 104c, 104 may be used alone or in combination.

[0104] Fig. 4 illustrates a cross-sectional view of a molded housing 110 according to an exemplary embodiment.

[0105] The semiconductor package 110 is mounted on a mounting structure 132, which is implemented here as a printed circuit board (PCB).

[0106] The mounting structure 132 includes an electrical contact 134 embodied as a plating in a through-hole of the mounting structure 132. When the semiconductor package 110 is mounted on the mounting structure 132, a semiconductor component 103 of the semiconductor package 110 is electrically connected to the electrical contact 134 via an electrically conductive carrier 114, which is embodied here as a lead frame made of copper.

[0107] The semiconductor package 110 thus comprises the electrically conductive carrier 114, the semiconductor component 103 (which is embodied here as a power semiconductor chip) mounted on the carrier 114, and an encapsulant 100 which encapsulates a part of the carrier 114 and the semiconductor component 103.

[0108] As from Fig. 4, a pad 160 on an upper main surface of the semiconductor component 103 is electrically coupled to the carrier 114 via a bonding wire as an electrically conductive connecting element 116. Alternatively, a clip can be used as an electrically conductive connecting element 116 (not shown).

[0109] In particular, the carrier 114 may have different lines leading out of the encapsulant 110 of the housing 110. The backside of the semiconductor component 103 (such as a die) is connected to a portion of the carrier 114, while the electrically conductive connection element 116 (such as a bond wire) is not connected to the same line. Instead, each line may be separately connected to the carrier 114 at different contact holes.

[0110] During operation of the power semiconductor package 110, the power semiconductor chip in the form of the semiconductor component 103 generates a considerable amount of heat. At the same time, it is important to ensure that unwanted current flow between a bottom surface of the semiconductor package 110 and the surrounding area is reliably prevented.

[0111] To ensure electrical insulation of the semiconductor component 103 and to dissipate heat from an interior of the semiconductor component 103 toward an environment, an electrically insulating and thermally conductive interface structure 148 may be provided, covering an exposed surface portion of the carrier 114 and a connected surface portion of the encapsulant 100 at the bottom of the semiconductor housing 110. The electrically insulating property of the interface structure 148 prevents unwanted current flow even in the presence of high voltages between an inside and an outside of the semiconductor housing 110. The thermally conductive property of the interface structure 148 promotes heat dissipation from the semiconductor component 103 via the electrically conductive carrier 114 (e.g., made of thermally conductive copper) through the interface structure 148 and toward a heat dissipation body 162.The heat dissipation body 162, which may be made of a highly thermally conductive material such as copper or aluminum, includes a base body 164 directly connected to the interface structure 148 and includes a plurality of cooling fins 166 extending from the base body 164 and parallel to each other to dissipate heat toward the environment.

[0112] The construction and function of the encapsulant 100 can be, for example, as in Fig. 1 and described with reference thereto, see detail 141. The illustrated semiconductor package encapsulant 100 partially or completely encapsulates the semiconductor component 103 with its metallic pad 160, the metallic leadframe-type chip carrier 114 and the electrically conductive bond wire-type connecting element 116.

[0113] Fig.5 illustrates a cross-sectional view of a semiconductor package 110 with a semiconductor component 103 encapsulated by a molding resin, according to another exemplary embodiment. Thus, Fig. 5 shows a semiconductor package encapsulant 100, which is designed as a potting compound. The semiconductor package 110 of Fig. 5 can be a power package.

[0114] The semiconductor package 110 shown is mounted to a mounting structure 132 embodied as a printed circuit board (PCB). The semiconductor package 110 is mounted at its mounting interface on the mounting structure 132 with a seal 158 therebetween. Preferably, the gas-flow-preventing seal 158 can establish a gas-tight connection between the semiconductor package 110 and the mounting structure 132.

[0115] The semiconductor package 110 includes a semiconductor component 103, such as a power semiconductor chip, which includes, for example, a field-effect transistor (FET). The semiconductor component 103 includes metallic pads 160.

[0116] A housing 174 encloses the semiconductor component 103 and defines a module interface at which the semiconductor package 110 is to be mounted on the mounting structure 132. In the illustrated embodiment, the housing 174 consists of two parts. A first or inner part of the housing 174 is embodied as a soft encapsulant 100 (made, for example, from epoxy and comprising stress-relieving filler particles 104 that are Fig.5) that directly encapsulates the semiconductor component 103 with physical contact, applied, for example, by molding. A second or outer portion of the housing 174 is embodied as a rigid housing or casing 172, which may be made of plastic and accommodates the semiconductor component 103 and the soft encapsulant 100.

[0117] Furthermore, vertically extending electrically conductive needles 180 may be provided, which electrically couple the semiconductor component 103 and the carrier 114 to an outer side of the semiconductor package 110, more specifically to the mounting structure 132. The needles 180 may also extend through the mounting structure 132. More specifically, lower ends (according to Fig. 5) of the needles 180 may be connected to an upper main surface of the carrier 114. Furthermore, upper ends (according to Fig.5) the needles 180 may be guided through the mounting structure 132 and may even protrude beyond the top of the mounting structure 132.

[0118] As in Fig.As shown in Figure 5, the semiconductor package 110 comprises the carrier 114, which carries the semiconductor component 103. The semiconductor component 103 can be soldered onto the carrier 114. In the embodiment shown, the carrier 114 comprises a central thermally conductive and electrically insulating plate (for example, made of a ceramic) covered on both opposite major surfaces thereof with a respective electrically conductive layer (such as a continuous or patterned copper or aluminum layer). For example, the carrier 114 can be a DCB (Direct Copper Bonding) substrate or a DAB (Direct Aluminum Bonding) substrate. It is also possible to implement the carrier 114 as an AMB (Active Metal Brazing) substrate. The semiconductor component 103 is mounted on the top-side electrically conductive layer.The bottom electrically conductive layer may be connected to a heat sink (not shown) to promote heat dissipation from the semiconductor package 110 during operation thereof.

[0119] Thus, the outer layer of the carrier 114 is configured for mounting a heat sink (not shown) thereon to efficiently dissipate heat from the semiconductor package 110 generated by the semiconductor component 103 mounted on the inner layer of the carrier 114. The semiconductor component 103 may be, for example, a power semiconductor chip. Electrical connection of the semiconductor component 103 may be achieved through the carrier 114 (in particular, through the inner electrically conductive layer thereof) and through electrically conductive connecting elements 116 that connect the carrier 114 to the pads 160 on an upper main surface of the semiconductor component 103. The electrically conductive connecting elements 116 are embodied here as bond wires, but may alternatively be bond ribbons or clips.

[0120] As also shown, the semiconductor component 103 mounted on the carrier 114 is enclosed within the housing 174, which consists of the soft encapsulant 100 and the wall of the housing 172.

[0121] The semiconductor package 110 may further include a further gas flow preventing seal 179 between the carrier 114 and the housing 172 of the housing 174.

[0122] The electrically conductive needles 180 extend from the carrier 114 through the encapsulant 100 and through the seal 158 at the module interface where the semiconductor package 110 faces the mounting structure 132.

[0123] For example, the semiconductor package 110 and the mounting structure 132 may be connected by screwing, soldering, sintering, gluing and / or mechanical pressing.

[0124] By implementing the potting type encapsulant 100 in a manner similar to that described above with reference to Fig. 1 (preferably based on epoxy resin as matrix 102), high electrical reliability can also be achieved with respect to a power cycle.

[0125] It should be noted that the term "comprising" does not exclude other elements or features, and "a" or "an" does not exclude a plurality. Furthermore, elements described in connection with different embodiments may be combined. It should also be noted that reference numerals are not to be construed as limiting the scope of the claims. Furthermore, the scope of the present application is not intended to be limited to the particular embodiments of the process, machine, manufacture, composition of matter, means, methods, and steps described in the specification. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacture, compositions of matter, means, methods, or steps.

Claims

[1] Encapsulant (100) for an electronic housing (110), the encapsulant (100) comprising: • an electrically insulating matrix material (102); and • stress-inhibiting filler particles (104) in the matrix material (102) which have a thermal expansion coefficient of not more than 6 ppm / K and a modulus of elasticity of not more than 4 GPa. [2] The encapsulant (100) of claim 1, wherein the stress-relieving filler particles (104) have a modulus of elasticity of not more than 1 GPa. [3] The encapsulant (100) according to claim 1 or 2, wherein the stress-relieving filler particles (104) have a thermal expansion coefficient value of not more than 4 ppm / K. [4] Encapsulant (100) according to one of claims 1 to 3, wherein the stress-inhibiting filler particles (104) have a negative value of the thermal expansion coefficient. [5] Encapsulant (100) according to one of claims 1 to 4, wherein the stress-inhibiting filler particles (104) are porous. [6] The encapsulant (100) of claim 5, wherein the stress-relieving filler particles (104) are closed porous particles. [7] Encapsulating agent (100) according to claim 5 or 6, wherein the porous stress-inhibiting filler particles (104) have a ratio between pore volume and total particle volume in a range of 1% to 80%, in particular in a range of 1% to 40%. [8] Encapsulating agent (100) according to one of claims 1 to 7, wherein the stress-inhibiting filler particles (104) have a functional coating (108). [9] Encapsulant (100) according to claim 8, wherein the functional coating (108) comprises an adhesion promoter and / or an insulator. [10] Encapsulant (100) according to claim 9, wherein the coupling agent comprises silane and / or a morphological coupling agent. [11] Encapsulant (100) according to one of claims 1 to 10, wherein the stress-inhibiting filler particles (104) comprise at least one material selected from the group consisting of zirconium tungstate, porous silica, borosilicate glass, β-eucryptite, α-ZrW2O8, β-ZrW2O8, Cd(CN)2, ReO3, (HfMg)(WO4)3, Sm 2,75 C 60 , Bi 0,95 La 0,05 NiO3, Invar (Fe-36Ni), Invar (Fe3Pt), Tm2Fe 16 Cr, copper oxide nanoparticles and Mn3Cu 0,53 Ge 0,47 N. [12] Encapsulating agent (100) according to one of claims 1 to 11, wherein the stress-inhibiting filler particles (104) have a size (D) below 100 µm, in particular in a range from 1 µm to 30 µm. [13] Encapsulating agent (100) according to one of claims 1 to 12, which additionally comprises functional filler particles (106) which impart at least one additional function to the encapsulating agent (100). [14] Encapsulant (100) according to claim 13, wherein the at least one additional function comprises an increase in the thermal conductivity of the encapsulant (100), an increase in the hardness of the encapsulant (100) and a reduction in the mismatch of the thermal expansion coefficient between the encapsulant (100) and a semiconductor material, in particular silicon or silicon carbide. [15] Encapsulant (100) according to one of claims 1 to 14, wherein the matrix material (102) comprises an epoxy resin, silicone, a bismaleimide and / or an imide. [16] Encapsulating agent (100) according to one of claims 1 to 15, comprising at least one of the following features: formed as a molding compound, in particular as an epoxy-based casting compound; formed as a casting compound, in particular as an epoxy-based casting resin. [17] Housing (110), comprising: • a carrier (114); • an electronic component (103) mounted on the carrier (114); and • an encapsulant (100) that at least partially encapsulates the electronic component (103) and the carrier (114); • wherein a value of the elastic modulus of the encapsulant (100) multiplied by an absolute value of a difference between values ​​of the thermal expansion coefficient of the encapsulant (100) and the electronic component (103) is less than 372 GPa*ppm / K. [18] Housing (110) according to claim 17, wherein the encapsulant (100) comprises: • an electrically insulating matrix material (102); and • stress-inhibiting filler particles (104) which, for example, have a thermal expansion coefficient value of not more than 6 ppm / K and / or a modulus of elasticity value of not more than 4 GPa in the matrix material (102). [19] Housing (110) according to claim 17 or 18, wherein the encapsulant (100) corresponds to one of claims 1 to 16. [20] Housing (110) according to one of claims 17 to 19, comprising at least one of the following features: wherein the value of the elastic modulus of the encapsulant (100) multiplied by the absolute value of the difference between the values ​​of the thermal expansion coefficient of the encapsulant (100) and the electronic component (103) is less than 200 GPa*ppm / K, preferably less than 100 GPa*ppm / K; wherein the housing (110) is a power housing; wherein the electronic component (103) is a semiconductor chip, for example comprising silicon.

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