Encapsulating agent with porous dye for an electronic housing

Abstract

Encapsulation agent (100) for an electronic housing (110), wherein the encapsulation agent (100) comprises an electrically insulating matrix material (102) and a porous dye (104) in the matrix material (102).

Description

BackgroundTechnical area

[0001] Various embodiments generally relate to an encapsulant, a housing, and a method of manufacture. 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] The electrical reliability of such a housing can be a problem. Summary

[0004] There may be a need for an enclosure with high electrical reliability.

[0005] According to an exemplary embodiment, an encapsulant for an electronic package is provided, the encapsulant comprising an electrically insulating matrix material and a porous dye in the matrix material.

[0006] According to a further exemplary embodiment, a housing is provided which comprises a carrier, an electronic component mounted on the carrier, and an encapsulant having the above-mentioned features which at least partially encapsulates the electronic component and the carrier.

[0007] According to another exemplary embodiment, a method of manufacturing an encapsulant for an electronic package is provided, the method comprising providing an electrically insulating matrix material and incorporating a porous dye into the matrix material.

[0008] According to an exemplary embodiment, an encapsulant (e.g., a potting 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 basis 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). Very advantageously, a porous dye with a high pore density may be contained in or embedded in the matrix material.Due to its numerous pores, which result in a significantly increased surface area per volume ratio compared to a non-porous dye, such a porous dye can exhibit excellent electrically insulating properties and can therefore promote the electrical reliability of the package. This reliable electrical insulation property contrasts with conventional approaches that use only electrically conductive carbon black as a dye of the encapsulant. Without wishing to be bound by any specific theory, it is currently believed that a porous dye, which provides an extremely high surface area due to its pores, leads to its highly pronounced electrical insulation properties. At the same time, such a porous dye can impart a defined color (such as black or dark gray) to the encapsulant.This can provide advantages in terms of laser markability and can lead to a simplification of a package stress test, which can be carried out with no, or at least no, significant color change. Furthermore, the porous dye of the encapsulant, which can be depleted or even completely free of electrically conductive particles (such as soot, metal particles, etc.), can lead to improved breakdown voltage and improved long-term low voltage stability. At the same time, a low amount of, or even no, electrically conductive particles in the encapsulant can advantageously reduce the tendency toward corrosion and can improve the adhesion of the components (such as an electronic component and / or a carrier) in contact with the encapsulant. The reduced tendency toward corrosion may be related to the large surface area of ​​the dye, which can adsorb free ions and / or small molecules.In particular, excellent time-dependent dielectric breakdown (TDDB) behavior can be achieved with such an encapsulant. Description of further exemplary embodiments

[0009] Further exemplary embodiments of the encapsulant, the housing and the method are explained below.

[0010] In the context of the present application, the term "encapsulant" may in particular refer to a material, structure, or 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 potting compound. A potting compound may comprise a matrix of a flowable and curable material, in particular a dye, optionally one or more additives, and optionally filler particles embedded therein. For example, filler particles may be used to adjust the properties of the molded component, in particular to increase thermal conductivity.As an alternative to a potting compound (e.g. based on epoxy resin), the encapsulant can also be a potting compound (e.g. based on a silicone gel).

[0011] 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 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 porous dye, a suitable matrix material, and / or one or more suitable additives of the encapsulant.

[0012] In the context of the present application, the term "electrically insulating matrix material" may, in particular, refer to a material in which the porous dye is embedded. The electrically insulating properties of the matrix material may be so pronounced that no appreciable 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 packaging properties.

[0013] In the context of the present application, the term "dye" can, in particular, refer to an agent that imparts a predefined and permanent color to the encapsulant. Preferably, the color is black or dark gray.

[0014] In the context of the present application, the term "porous dye" may, in particular, refer to a dye comprising a large number of pores. In particular, the porous dye may be formed as a large number of particles, at least a majority of which comprise one or more pores. The pores of the porous dye may include through-pores extending completely through a dye particle, blind pores extending into and terminating within a dye particle, and / or bifurcated pores forming part of an interconnected pore network within a respective dye particle.

[0015] 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, pumps, bonding wires, and / or terminals) may be implemented in a housing, for example, for electrically coupling and / or mechanically supporting the electronic component.

[0016] 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, it may be or comprise a die pad.For example, such a carrier can 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 can also be formed as an AMB (Active Metal Brazing) substrate. At least a portion of the carrier can also be encapsulated together with the electronic component by the encapsulant.

[0017] In the context of the present application, the term "electronic component" may in particular include 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). In other embodiments, however, 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 already be packaged or encapsulated. Semiconductor chips implemented according to exemplary embodiments may be formed using silicon technology, gallium nitride technology, silicon carbide technology, etc.

[0018] 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 potting compound (EMC). Silicone can form the basis of a gel-like encapsulant for potting.

[0019] In one embodiment, the encapsulant is formed as a potting compound, in particular as an epoxy-based potting compound. Thus, various types of potting compounds can be used, such as silicone potting compound, bismaleimide potting compound, imide potting 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, the encapsulation of the one or more semiconductor components of the semiconductor package can be achieved by molding. Consequently, the encapsulant can comprise a curable matrix (e.g., based on epoxy resin) with filler particles (for fine-tuning encapsulation functions) therein. By implementing a porous dye in the potting compound, further improved electrical reliability of the resulting molded semiconductor package can be achieved.

[0020] In one embodiment, the encapsulant is formed as a potting compound, in particular as a silicone gel-based compound. In particular, potting 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 resistance to shock and vibration, and / or can be performed for the exclusion of water, moisture, etc. Embedding a porous dye in a potting compound can further improve the electrical reliability of the resulting encapsulated semiconductor package.

[0021] In one embodiment, the porous dye comprises porous activated carbon. Porous activated carbon may refer to a carbon material (e.g., formed from soot, charcoal, wood, or another natural material comprising carbon) that may be provided in the form of particles, each comprising a porous solid body with internal pores. Pores may be formed by a surface treatment of carbonaceous particles or bodies, for example, by treatment with a chemical, a plasma, and / or a thermal treatment. Activating carbon may involve forming pores or increasing porosity in a carbonaceous material.

[0022] In one embodiment, the porous dye comprises porous titanium dioxide. Titanium dioxide also acts as a dye, imparting a defined and permanent color to the encapsulant, and can be treated to exhibit pronounced porosity.

[0023] In one embodiment, the encapsulant additionally comprises carbon black and / or crystalline petroleum coke. In the context of the present application, the term "carbon black" may specifically refer to a fine carbon powder that can be produced by burning hydrocarbons in insufficient air. In particular, carbon black may refer to a material that can be produced by the incomplete combustion of coal and coal tar, vegetable material, or petroleum products, including fuel oil, liquid catalytic cracking tar, and ethylene cracking, in a limited air supply. Carbon black may be a black, finely divided form of amorphous carbon. These particles provide a certain electrical conductivity for removing charge carriers from the housing. However, the electrical conductivity of these materials is not excessively high.In the context of the present application, the term ‘crystalline petroleum coke’ may in particular refer to a material made (for example exclusively) from liquid catalytic cracked tar oil or coal tar pitch.

[0024] Adding a limited amount of carbon black (and / or crystalline petroleum coke) to the porous dye and the matrix material can provide the advantage of further improving color intensity.

[0025] In one embodiment, a ratio between an amount, in weight percent, of the porous dye and an amount, in weight percent, of the carbon black and / or the crystalline petroleum coke is in a range of 1:4 to 4:1, particularly in a range of 1:2 to 2:1. For example, a partial weight percentage of the porous dye can be in a range of 20 weight percent to 80 weight percent, based on the total weight of the entire dye. Accordingly, a partial weight percentage of the carbon black (and / or the crystalline petroleum coke) can be in a range of 20 weight percent to 80 weight percent, based on the total weight of the entire dye. Of course, the various dye components will always add up to 100 weight percent of the total dye.The ratio between porous dye and carbon black / crystalline petroleum coke can be used as a design parameter to compromise between electrical insulation properties and color intensity.

[0026] In another embodiment, the encapsulant is free of carbon black and / or free of crystalline petroleum coke. In particular, the encapsulant may be free of electrically conductive particles (such as carbon black). One skilled in the art will understand that an encapsulant free of electrically conductive particles may still contain an unavoidable residue of electrically conductive particles due to manufacturing tolerances and the like. Because it is substantially free of electrically conductive particles, the encapsulant may exhibit excellent electrical breakdown voltage and favorable TDDB behavior.

[0027] In one embodiment, the porous dye is configured as an ion getter. Thus, free ions in the encapsulant, which can provide undesirable electrical conductivity, can be captured by the porous dye when configured as an ion getter. To configure the porous dye as an ion getter, suitable chemical groups can be added to the particles of the porous dye. This can be achieved by chemically treating the particles.

[0028] In one embodiment, the porous dye has at least one ion-adsorbing group (or ion getter group) designed to adsorb ions. Particularly suitable ion-adsorbing groups are a carboxylic acid, a lactone, a phenol, a lactol, and / or a carboxylic acid anhydride.

[0029] In one embodiment, the amount of the porous dye is at least 0.5 weight percent, based on the total weight of the encapsulant, and in particular is in a range of 0.5 weight percent to 2 weight percent, based on the total weight of the encapsulant. Selecting the weight percentage of the porous dye within the stated range can make it possible to keep manufacturing costs low while simultaneously ensuring sufficiently dark color intensity and favorable electrical properties.

[0030] In one embodiment, the porous dye has an electrical conductivity of not more than 10 -3 S / cm, in particular not more than 10 -5S / cm. These electrical conductivity values ​​of the porous dye indicate highly reliable electrical insulation provided by the porous dye in combination with the electrically insulating matrix material. This is a consequence of the sufficiently high porosity of the porous dye.

[0031] In one embodiment, the porous dye is designed to form carbon-oxygen complexes during use. To provide this effect, the carbon material of the porous dye can be designed to exhibit high oxygen chemisorption.

[0032] In one embodiment, the porous dye has a low nitrogen doping and / or a low degree of graphitization. These properties are also advantageous for the porous dye and the correspondingly designed encapsulant.

[0033] In one embodiment, the porous dye (particularly in the form of particles) has a surface-to-mass ratio of at least 100 m 2 / g, in particular a surface-to-mass ratio in the range of 100 m 2 / g up to 2000 m 2 / g, especially in a range of 500 m 2 / g up to 1750 m 2 / g, preferably in a range of 1000 m 2 / g up to 1500 m 2 / g. The values ​​and ranges mentioned indicate a very large external and / or internal surface area of ​​porous dye particles due to their correspondingly high pore density. A large external surface area of ​​the porous dye particles advantageously translates into strong electrical insulation properties.

[0034] In one embodiment, particles of the porous dye have a size in a range of 0.1 µm to 100 µm. In this range, a particularly high amount of porous outer surface can be obtained. Preferably, the particle size of the activated porous carbon can be no more than 100 µm.

[0035] In one embodiment, the method comprises subjecting the porous dye to an additional surface activation process to alter chemical groups on its surface. Thus, the already porous dye can be subjected to additional surface activation to further improve the contribution of the surface-activated porous dye to the electrical reliability of the encapsulant. This can be achieved by altering the chemical surface of the porous dye due to the activation treatment. Additionally or alternatively, this can be achieved by increasing the porosity of the porous dye due to the activation treatment.

[0036] In one embodiment, the method comprises treating the porous dye by vapor processing, oxidation, corona treatment, and / or chemical treatment. Other processes for pore formation, increasing porosity, altering the chemical surface of the porous dye, and / or surface activation may also be performed.

[0037] In one embodiment, the method comprises treating the porous dye to reduce its electrical conductivity. In particular, increasing the porosity can reduce the electrical conductivity. Another goal to be achieved by treating the porous dye can be increasing its adhesion to other package components, such as a semiconductor chip and / or a lead frame.

[0038] In one embodiment, the encapsulant further comprises filler particles in the matrix material. In the context of the present application, the term "filler particles" may in particular refer to a (particularly powdered or granular) substance that fills internal volumes in a surrounding medium, such as a matrix. By selecting the 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 filler particles can thus be added to fine-tune the physical, chemical, etc. properties of the encapsulant.For example, the filler particles may increase the thermal conductivity of the encapsulant to efficiently remove heat from the interior of an electronic device, such as a package (such heat may be generated by a semiconductor component, for example, when embodied as a power semiconductor chip). It is also possible that the filler particles may provide improved dielectric decoupling between such a semiconductor component and the environment of the package.

[0039] In one embodiment, filler particles are selected from a group consisting of crystalline silica, fused silica, spherical silica, aluminum hydroxide, magnesium hydroxide, zirconium dioxide, calcium carbonate, calcium silicate, talc, clay, carbon fiber, glass fiber, and mixtures thereof. However, other filler materials are possible depending on the requirements of a particular application. Filler particles (e.g., SiO2, Al2O3, Si3N4, BN, AlN, diamond, etc.), for example, to improve thermal conductivity, can also be used. In particular, organic particles can be used as fillers (e.g., fillers can also comprise or consist of polymers or polymer blends, such as epoxies, polyethylene, polypropylene, etc.). In particular, filler particles can be provided as nanoparticles or microparticles.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 an interior of the encapsulant. For example, the shape of the filler particles may be random, spherical, cuboid, flake, and film. The filler particles may be modified, coated, and / or treated to improve adhesion and / or chemical bonding to the surrounding matrix. Examples include silanes. A coating may also alter the surface energy of the fillers.

[0040] 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 include one or more field-effect transistors, diodes, inverter circuits, half-bridges, full-bridges, drivers, logic circuits, other devices, etc.

[0041] In one embodiment, the package is a power package. 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).

[0042] 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 (TSOP) package. 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 user-friendly.

[0043] In one embodiment, the package includes a plurality of semiconductor components encapsulated by the semiconductor package encapsulant. Thus, the package may include one or more semiconductor components (e.g., at least one passive component, such as a capacitor, and at least one active component).

[0044] A semiconductor substrate, in particular a silicon substrate, can be used as the substrate or wafer that forms the basis of the semiconductor 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.

[0045] 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

[0046] The accompanying drawings, which are included to provide a further understanding of exemplary embodiments and constitute a part of the specification, illustrate exemplary embodiments. In the drawings: Fig. 1 an encapsulant according to an exemplary embodiment. Fig. 2 a flowchart of a method for producing an encapsulant according to an exemplary embodiment. Fig. 3 a cross-sectional view of a housing according to an exemplary embodiment. Fig. 4 a cross-sectional view of a housing according to another exemplary embodiment. Detailed description

[0047] The representation in the drawing is schematic and not to scale.

[0048] Before describing exemplary embodiments in more detail with reference to the figures, some general considerations on the basis of which exemplary embodiments were developed are summarized.

[0049] Carbon black is a common additive in epoxy encapsulant formulations. Carbon black gives enclosures a stable black color, provides electrostatic discharge (ESD) protection, and improves laser markability.

[0050] However, an excessive concentration of carbon black in an epoxy encapsulant (EMC) increases the risk of enclosure failure under high-voltage conditions. Carbon black tends to aggregate and form a conductive bridge. Carbon black can shorten the distance between metals with opposite potentials and can distort the electric field within an enclosure.

[0051] Conventional solutions to address these deficiencies include adding additives, improving filler / epoxy interfacial bonding, using a smaller filler size as a crack spinner or deflector at the expense of additional effort, and modifying the EMC properties. For example, improving filler / epoxy interfacial bonding by incorporating a surface modifier can improve TDDB performance, but it makes the molding process more difficult.

[0052] To overcome at least some of the aforementioned and / or other conventional deficiencies, an exemplary embodiment provides an encapsulant (such as a potting compound or a potting gel) suitable for encapsulating an electronic package that may include a semiconductor chip to be encapsulated. An electrically insulating matrix material (which may be provided based on epoxy resin and / or silicone) may form the basis of the encapsulant and may contribute to the mechanical integrity and electrical insulation of package components. Advantageously, a dye for coloring the encapsulant may be embodied as a porous dye. In short, the pore structure of such a dye may result in a large surface area, preferably over 200 m 2 / g. It has been found that such a porous dye can exhibit highly reliable electrically insulating properties, which can lead to electrical reliability of the package. At the same time, the porous dye can color the encapsulant (preferably black or dark gray), which can improve the readability of laser markings formed on the exterior surface of a package encapsulant. Such a porous dye can also provide advantages in supporting a package stress test, during which significant color change can be prevented. Furthermore, an electrically insulating porous dye can exhibit excellent properties in terms of breakdown voltage and long-term low voltage stability.It can help prevent corrosion, act as an ion getter, and also act as an adhesion promoter for package components that may come into direct physical contact with the encapsulant during encapsulation. Furthermore, the time-dependent dielectric breakdown (TDDB) properties of an encapsulant with a porous dye are advantageous.

[0053] According to a preferred embodiment, a molding compound-type encapsulant is provided with a dye with tunable electrical conductivity and surface for improved voltage stability and corrosion resistance. In particular, such a molding compound-type encapsulant can be implemented as a high-voltage epoxy potting compound. In particular, the use of activated carbon as a porous dye in an electrically insulating epoxy potting compound has proven to be an excellent solution.

[0054] However, embodiments of the porous dye are not limited to porous carbon materials. It may also be possible to use alternative non-conductive dyes, such as titanium dioxide (TiO2).

[0055] Advantageously, a porous dye (or a mixture of a porous dye with a reduced amount of carbon black or the like) may be used as a component of an electrically insulating package encapsulant to provide color stability, ESD (electrostatic discharge) protection, readable laser marking, reduced potential for electrical warping, etc.

[0056] A preferred embodiment may involve the use of activated carbon as a porous pigment in an epoxy encapsulant. Activated carbon with a porous property can provide several advantages over a conventionally used carbon black in an EMC: On the one hand, such a porous dye can be advantageous for a package encapsulant for high-performance devices and wide-bandgap materials. Furthermore, it can also advantageously enable package shrinkage and increased stresses.

[0057] Furthermore, such a porous dye in a package encapsulant can offer particular advantages under high-voltage conditions. High porosity is a major factor reducing the intrinsic electrical conductivity of the material. For example, activated carbon formed with high porosity (i.e., surface-to-mass or volume ratio) can exhibit very strong electrical insulation properties. Replacing carbon black (particularly completely or partially) with activated porous carbon can maintain a black color in the EMC for color stability and ease of laser marking. Additionally, activated porous carbon (as an exemplary embodiment of a porous dye) can significantly reduce any remaining electrical conductivity by shortening the chain of soot agglomerates in the EMC.This can make it possible to reduce or even minimize the formation of electrical sagging and EMC failure. A corresponding improvement can be achieved when it comes to tracking, as an increased comparative tracking index (CTI) can be obtained.

[0058] Another advantage of a porous dye in a housing encapsulant is its intrinsic protection against corrosion. A porous material has a high surface-to-volume ratio. It can thus act as an efficient adsorbent to immobilize small organic contaminants, metals, and ions (e.g., chloride ion adsorption on the surface of activated carbon via hydrogen bonding or van der Waals forces). Therefore, activated porous carbon can act as an ion getter within the EMC.

[0059] Another advantage is that no significant change in the overall EMC properties can occur, as the concentration of the porous dye in an EMC can be relatively small, for example, less than 1 weight percent based on the total weight of the encapsulant. Since activated porous carbon is a black dye, no significant changes to an EMC production line are required.

[0060] Thus, a preferred embodiment may involve the use of activated porous carbon as a colorant in an epoxy resin-based (or silicone, bismaleimide, or imide resin-based) encapsulant. Both hydrogen bonding and Van der Waals forces are primary modes of attraction in activated porous carbon. The mode of attraction may shift from hydrogen bonding to Van der Waals as the pH of a medium increases. The typical pH of an EMC is between 3 and 8. To facilitate anion adsorption (e.g., Cl - , SO4 2- To increase or even maximize the kinetic energy of the activated porous carbon, the activated porous carbon can be provided with functional groups (e.g., carboxylic acid, lactone, phenol, lactol, carboxylic anhydride, ether) capable of forming hydrogen bonds. A corresponding reaction can be as follows: R-COOH + Cl - → R-COOH - Cl -

[0061] Thus, an activated porous carbon surface can be equipped with an R-COOH group to be able to absorb negative ions such as Cl - to capture, thereby acting as an ion getter.

[0062] Preferably, the activated porous carbon may have low electrical conductivity (which may be achievable via a high total pore volume), high chemisorption of oxygen (to form carbon-oxygen complexes as defects that further reduce the electrical conductivity of the encapsulant), a low degree of graphitization, and low nitrogen doping.

[0063] In another embodiment, an EMC is provided that contains a porous dye (e.g., porous titanium dioxide or activated porous carbon) without (or with a reduced concentration of) carbon black.

[0064] In yet another embodiment, a porous dye (e.g., embodied as activated porous carbon) may be used to form a different type of encapsulant than the EMC, e.g., a gel (which may be used, for example, as a silicone-based potting compound), etc.

[0065] In a preferred embodiment, an EMC with good electrical stability and corrosion resistance can be provided by providing the EMC-type encapsulant with a porous dye. This can eliminate or at least reduce the length of undesirable conductive carbon chains in the EMC. Furthermore, a porous dye in an encapsulant can be advantageously used to reduce ion mobility through immobilization or ion movement disruption. Further advantageously, a porous dye can provide very low electrical conductivity, thereby contributing to the electrical reliability of an encapsulated package.In a preferred embodiment, exactly no metal or modification may be present in the porous dye, which may allow to reliably avoid any undesirable increase in electrical conductivity and any undesirable metal release to the EMC.

[0066] As for soot in the EMC, it may even be completely absent or present in reduced concentrations.

[0067] Activated porous carbon can have a structure similar to graphite, but with a highly porous structure with pores of varying sizes. Activated porous carbon can exhibit different cracks and crevices at the molecular level. Advantageously, activated porous carbon can have an internal surface area of ​​up to 1500 m². 2 / g or more. Activated porous carbon can have very high porosity, even down to the molecular level. Preferably, a porous dye embodied as highly porous carbon can have an internal surface area of ​​up to 1500 m 2 / g or more. A suitable range can be between 100 m 2 / g and 2000 m 2 / g, especially from 500 m 2 / g up to 1750 m 2 / g and preferably from 1000 m 2 / g up to 1500 m 2 / g. More generally, an internal surface per mass can be at least 100 m 2 / g or at least 200 m 2 / g.

[0068] One operating principle of embodiments with the aforementioned high internal surface area per mass values ​​may be that, due to the high porosity of the porous carbon, the epoxy resin can incorporate the high-porosity carbon and fill the pores. This allows the resistivity of the final encapsulant to be significantly lower compared to non-porous carbon black. In non-porous carbon black, there is much less polymer per volume, and thus the electrical conductivity is higher, reducing the risk of electrical failure under high-voltage conditions.

[0069] If a porous dye such as porous carbon with a very high surface area is advantageously implemented, it may be further advantageous to perform additional surface activation of this high-porosity carbon. Advantageously, such additional surface activation can change the chemical groups on the surface of the porous dye. Such a surface treatment can change the structure in the pores and can thus lead to further improved properties. There are various surface treatments suitable for activated carbon. An example of such a surface treatment can function through an oxidation process as a first step, which can be carried out by corona treatment (preferably at high voltage and frequency), which causes surface oxidation by O3 and / or O2 on the substrate via electrical discharge.This oxidation can already lead to a further reduction in electrical conductivity, since the partially oxidized surface can increase the specific surface resistance of the porous carbon.

[0070] Other types of carbon treatment can be with suitable chemicals (such as H2O2, NH3), which can lead to various functional groups on the surface, such as -OH, -NH2 groups, etc. Other functionalities can also be achieved, for example, by using chemical groups such as -SH, =O, -COOH, COOR, COONH2, -epoxy, etc.

[0071] All of these surface treatments can be used to further reduce the conductivity of the activated porous carbon and improve the adhesion between the resin and the carbon particles. Additionally, changing the surface chemistry can also alter other properties, such as the ambient pH, which can affect the material properties.

[0072] Fig. 1 illustrates an encapsulant 100 according to an exemplary embodiment.

[0073] The schematically illustrated encapsulant 100 is configured to encapsulate an electronic package 110, such as the one shown in Fig. 3 and Fig. 4 shown.

[0074] 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. 3, the matrix material 102 may comprise an epoxy resin. For a potting type encapsulant 100, as used for the housing 110 of Fig. 4, the matrix material 102 may comprise silicone.

[0075] Furthermore, the encapsulant 100 may include filler particles 143 to fine-tune the physical properties of the encapsulant 100. For example, the filler particles 143 may be aluminum nitride particles to increase thermal conductivity.

[0076] Apart from that, one or a number of other additives (in Fig. 1 not shown) may be added to the encapsulant 100 to further adjust its physical properties and provide dedicated functionality. Added additives may include a voltage stabilizer, an antioxidant, an ultraviolet (UV) absorber, an adhesion promoter, low-stress additives, etc.

[0077] Advantageously, a porous dye 104 can be mixed into the matrix material 102. For example, an amount of the porous dye 104 is 1 weight percent, based on the total weight of the encapsulant 100. An electrical conductivity of the porous dye 104 can be, for example, 10 -4 S / cm. This gives the encapsulant 100 a distinct dark color and reliable electrically insulating properties. As described in Fig. 1, the porous dye 100 comprises a large number of pores 108, which significantly increase the outer surface area of ​​the particles of the porous dye 104. Preferably, the porous dye 104 has a surface-to-mass ratio of at least 100 m 2 / g, most preferably in a range of 1000 m 2 / g up to 1500 m 2 / G.

[0078] Individual particles of the porous dye 104 may have a maximum size D in a range of 0.1 µm to 100 µm, for example, in a range of 5 µm to 50 µm. The porous dye 104 may preferably comprise porous activated carbon. Additionally or alternatively, porous titanium dioxide may form or be part of the porous dye 104.

[0079] Optionally, the encapsulant 100 may additionally comprise an electrically conductive dye in a limited amount, such as carbon black 106. Preferably, the amount of carbon black 106 in the encapsulant 100 is strictly limited to avoid degrading the reliable electrical insulation properties of the encapsulant 100. However, a small amount of carbon black 106 may be advantageous in certain scenarios, as it can improve the color intensity of the encapsulant 100. For example, the total dye may be composed of 80 weight percent porous dye 104 (embodied here as activated porous carbon) and 20 weight percent nonporous dye (embodied here as carbon black 106), both based on the total weight of the total dye.

[0080] Advantageously, the porous dye 104, which is designed as activated porous carbon, is designed as an ion getter. For this purpose, at least some of the particles of the porous dye 104 can be equipped with at least one ion-adsorbing group 109, which is shown schematically in Fig. 1. Examples of suitable ion-adsorbing groups 109 are a carboxylic acid, a lactone, a phenol, a lactol, and / or a carboxylic acid anhydride. The porous dye 104 can advantageously be configured to form carbon-oxygen complexes during use. Furthermore, the porous dye 104 can be provided with a low nitrogen doping and with a low degree of graphitization. All of these measures can additionally contribute to strong electrical insulation of the porous dye 104 and thus to the excellent electrical reliability of a housing 110 comprising this encapsulant 100.

[0081] To fine-tune the aforementioned properties of the porous dye 104, the porous dye 104 may be subjected to an additional surface activation process to modify chemical groups (such as the at least one ion-adsorbing group 109) on its surface. For example, treating the porous dye 104 may include vapor processing, oxidation, corona treatment, and / or a chemical treatment. It may be particularly advantageous for the treatment of the porous dye 104 to be achieved selectively to reduce its electrical conductivity and / or to increase the adhesion properties with respect to the components of an associated housing 110 (see Fig. 3 and Fig. 4).

[0082] Fig. 2 illustrates a flowchart 200 of a method for manufacturing an encapsulant 100 for an electronic package 110 according to an exemplary embodiment. The reference numerals used for the following description of the manufacturing method refer to the embodiments of Fig. 1 and Fig. 3.

[0083] Referring to a block 202, the method includes providing a matrix material 102.

[0084] Referring to a block 204, the method further comprises incorporating a porous dye 104 into the matrix material 102.

[0085] Fig. 3 illustrates a cross-sectional view of a molded housing 110 according to an exemplary embodiment.

[0086] The semiconductor package 110 is mounted on a mounting structure 132, which is implemented here as a printed circuit board.

[0087] The mounting structure 132 has an electrical contact 134, which is 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 copper lead frame.

[0088] 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.

[0089] As from Fig. 3, 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 clamp may be used as an electrically conductive connecting element 116 (not shown).

[0090] 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.

[0091] 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 any unwanted current flow between a bottom surface of the semiconductor package 110 and the surrounding area is reliably prevented.

[0092] To ensure electrical insulation of the semiconductor component 103 and to remove 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 remove heat toward the environment.

[0093] The structure and function of the encapsulant 100 can be as shown in Fig. 1 and described with reference to it. A detail 141 of Fig. However, Figure 3 shows a slightly modified encapsulant 100 and will be explained in more detail below. The encapsulant 100 of Fig. 3 is a molding compound type composite. As shown in detail 141 of Fig. 3, the composite encapsulant 100 comprises a matrix 102 of epoxy resin and filler particles 143 in the matrix 102. Some or all of the filler particles 143 may be solid spheres. Advantageously, particles of a porous dye 104, each having a plurality of pores, are included in the encapsulant 100. In the embodiment of Fig. 3, the encapsulant 100 is completely free of dyes other than the porous dye 104, in particular it is free of carbon black (see reference numeral 106 in Fig. 1). This can provide highly reliable electrical insulation of the encapsulant 100 from Fig. 3 ensure.

[0094] 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. Filler particles 143 of the semiconductor package encapsulant 100 can increase the thermal conductivity and can be made of, for example, aluminum oxide and / or boron nitride. The porous dye 104 imparts Fig. 3 has a dark color and, together with the electrically insulating matrix material 102, contributes significantly to the strong electrically insulating properties of the encapsulant 100.

[0095] Fig. 4 illustrates a cross-sectional view of a semiconductor package 110 with a semiconductor component 103 encapsulated by molding, according to another exemplary embodiment. Thus, Fig. 4 shows a semiconductor package encapsulant 100, which is designed as a potting compound. The semiconductor package 110 of Fig. 4 can be a power enclosure.

[0096] 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.

[0097] 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.

[0098] 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 is composed of two parts. A first or inner part of the housing 174 is embodied as a soft encapsulant 100 (made, for example, from a silicone gel and including filler particles 143) that directly encapsulates the semiconductor component 103 with physical contact, for example, applied by potting. A second or outer part of the housing 174 is embodied as a rigid housing or case 172, which may be made of plastic and accommodates the semiconductor component 103 and the soft encapsulant 100.

[0099] Furthermore, vertically extending electrically conductive needles 180 may be provided, which electrically couple the semiconductor component 103 and the carrier 114 to an outside of the semiconductor package 110, more precisely to the mounting structure 132. The needles 180 may also extend through the mounting structure 132. More precisely, lower ends (according to Fig. 4) of the needles 180 may be connected to an upper main surface of the carrier 114. Furthermore, upper ends (according to Fig. 4) the needles 180 may be guided through the mounting structure 132 and may even protrude beyond the top of the mounting structure 132.

[0100] As in Fig. As shown in Figure 4, the semiconductor package 110 comprises the carrier 114, which supports 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.

[0101] Thus, the outer layer of the carrier 114 is configured for mounting a heat sink (not shown) thereon to efficiently remove 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. The electrical connection of the semiconductor component 103 may be achieved by the carrier 114 (in particular, by the inner electrically conductive layer thereof) and by 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 clamps.

[0102] As also shown, the semiconductor component 103 mounted on the carrier 114 is enclosed within the housing 174, which is composed of the soft encapsulant 100 and the wall of the housing 172.

[0103] 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.

[0104] 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. For example, the semiconductor package 110 and the mounting structure 132 may be connected by screwing, soldering, sintering, gluing, and / or mechanical pressing.

[0105] By implementing the potting type encapsulant 100 in a manner similar to that described above with reference to Fig. 1 or Fig. 3 (but preferably based on silicone gel as matrix 102, whereas epoxy resin is also possible), a pronounced and defined coloration as well as high electrical reliability can be achieved.

[0106] It should be noted that the term "comprising" does not exclude other elements or features, and "a" or "an" does not exclude a plurality. Even 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 such processes, machines, manufacture, compositions of matter, means, methods, or steps within their scope.

Claims

[1] Encapsulant (100) for an electronic housing (110), the encapsulant (100) comprising: • an electrically insulating matrix material (102); and • a porous dye (104) in the matrix material (102). [2] Encapsulant (100) according to claim 1, wherein the matrix material (102) comprises an epoxy resin, silicone, a bismaleimide and / or an imide. [3] The encapsulant (100) of claim 1 or 2, wherein the porous dye (104) comprises porous activated carbon. [4] The encapsulant (100) of any one of claims 1 to 3, wherein the porous dye (104) comprises porous titanium dioxide. [5] Encapsulant (100) according to one of claims 1 to 4, wherein the encapsulant (100) additionally comprises carbon black (106) and / or crystalline petroleum coke. [6] Encapsulating agent (100) according to claim 5, wherein a ratio between an amount, in weight percent, of the porous dye (104) and an amount, in weight percent, of the carbon black (106) and / or the crystalline petroleum coke is in a range of 1:4 to 4:1, in particular in a range of 1:2 to 2:

1. [7] Encapsulant (100) according to one of claims 1 to 4, wherein the encapsulant (100) is free of soot and / or free of crystalline petroleum coke. [8] Encapsulating agent (100) according to one of claims 1 to 7, wherein the porous dye (104) is formed as an ion getter. [9] Encapsulating agent (100) according to one of claims 1 to 8, wherein the porous dye (104) has at least one ion-adsorbing group (109), in particular a carboxylic acid, a lactone, a phenol, a lactol and / or a carboxylic acid anhydride. [10] Encapsulating agent (100) according to one of claims 1 to 9, wherein an amount of the porous dye (104) is at least 0.5% by weight, based on the total weight of the encapsulating agent (100), in particular in a range of 0.5% by weight to 2% by weight. [11] Encapsulant (100) according to one of claims 1 to 10, wherein the porous dye (104) has an electrical conductivity of not more than 10 -3 S / cm, in particular not more than 10 -5 S / cm. [12] Encapsulant (100) according to any one of claims 1 to 11, wherein the porous dye (104) is configured to form carbon-oxygen complexes in use. [13] Encapsulant (100) according to any one of claims 1 to 12, wherein the porous dye (104) has a surface-to-mass ratio of at least 100 m 2 / g, in particular a surface-to-mass ratio in a range of 100 m2 / g up to 2000 m 2 / g, especially in a range of 500 m 2 / g up to 1750 m 2 / g, preferably in a range of 1000 m 2 / g up to 1500 m 2 / G. [14] Encapsulating agent (100) according to one of claims 1 to 13, comprising one of the following features: designed as a potting compound, in particular as an epoxy-based potting compound; formed as a potting compound, in particular as a silicone gel-based compound. [15] Encapsulating agent (100) according to one of claims 1 to 14, wherein particles of the porous dye (104) have a size (D) in a range of 0.1 µm to 100 µm. [16] Housing (110), comprising: • a carrier (114); • an electronic component (103) mounted on the carrier (114); and • an encapsulating means (100) according to any one of claims 1 to 15, which at least partially encapsulates the electronic component (103) and the carrier (114). [17] The package (110) of claim 16, wherein the electronic component (103) is a semiconductor power chip. [18] Housing (110) according to claim 16 or 17, wherein the housing (110) is a power housing. [19] A method of manufacturing an encapsulant (100) for an electronic package (110), the method comprising: • Providing an electrically insulating matrix material (102); and • Inserting a porous dye (104) into the matrix material (102). [20] Method according to claim 19, comprising at least one of the following features: the method comprising subjecting the porous dye (104) to an additional surface activation process to change chemical groups on its surface; wherein the method comprises treating the porous dye (104) by steam processing, oxidation, corona treatment and / or a chemical treatment; wherein the method comprises treating the porous dye (104) to reduce its electrical conductivity.

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