A package comprising a chip contact element made of two different electrically conductive materials, and a method for producing a package

Abstract

A package (100) comprising: • an electronic chip (102) having at least one pad (104); • an encapsulation (106) which at least partially encapsulates the electronic chip (102); • an electrically conductive contact element (108) extending from the at least one pad (104); • wherein the electrically conductive contact element (108) comprises a first contact structure (110) made of a first electrically conductive material on the at least one pad (104), and a second contact structure (112) made of a second electrically conductive material and exposed with respect to the encapsulation (106), such that the electrically conductive contact element (108) extends through the encapsulation (106) to be exposed with respect to the encapsulation (106); • wherein the electrically conductive contact element (108) is a strip element, comprising the first contact structure (110) having a first layer of the first electrically conductive material, and the second contact structure (112) having a second layer of the second electrically conductive material. • wherein at least one of the at least one pad (104) has at least one surface portion comprising or consisting of the first electrically conductive material.

Description

background

[0001] The present invention relates to packages and a method for manufacturing a package.

[0002] Packages can be defined as encapsulated electronic chips with electrical connections extending from the encapsulation and mounted on an electronic peripheral, such as a printed circuit board.

[0003] Packaging costs are a key factor influencing industry. Performance, dimensions, and reliability are all linked to them. Packaging solutions are diverse and must address the requirements of the application.

[0004] US 2004 / 0266037 A1 discloses a device comprising a leadframe and an electronic chip with contacts on a top surface. The device further comprises a conductive ball attached to the contact. A barrier layer and a solder ball are disposed on the side of the conductive ball facing away from the contact. Furthermore, the device comprises an encapsulation covering the chip.

[0005] DE 10 2009 040 557 A1 discloses a component comprising a semiconductor chip having a first and a second electrode on a first and second surface, respectively. Contact elements are coupled to the corresponding electrodes.

[0006] US 2015 / 0076712 A1 discloses an electronic device with a bimetallic interface element. The interface element has two layers made of different materials. The interface element is arranged between a contact pad and a bond wire. The contact pad and the entire package are completely encapsulated.

[0007] DE 10 2015 205 704 A1 discloses a contact arrangement of a semiconductor component. An electrical terminal of the semiconductor component has a metallization made of Al or an Al alloy, wherein the electrical terminal is connected to at least one wire bond made of Cu or a Cu alloy. A contact element is arranged between the at least one electrical terminal and the wire bond, which contact element is connected to the electrical terminal by a bottom side and to the wire bond by a top side.

[0008] WO 2012 / 053129 A1 discloses a semiconductor device comprising a chip mounting element with a connection pad and a semiconductor chip mounted on the chip mounting element and having a chip pad. A metal band connects the chip pad and the connection pad. The metal band has a first surface connected to the chip pad and a second surface located on the opposite side of the first surface and connected to the connection pad. The metal band extends from the connected portion of the first surface and the chip pad in the opposite direction of the base and is reversed over the semiconductor chip such that the second surface comes into contact with the upper surface of the base. An encapsulation completely encloses the chip and the lead. Summary

[0009] There may be a need to produce a package in a simple and reliable manner.

[0010] According to an exemplary embodiment, a package according to claim 1 or claim 13 is provided,

[0011] According to yet another exemplary embodiment, a method for manufacturing a package according to claim 17 is provided.

[0012] According to the present invention, a package and a manufacturing method for manufacturing such a package are thus provided, wherein an electrically conductive contact element has a first surface that directly contacts a chip pad and another, second surface that is exposed with respect to an encapsulation to enable electrical contacting of the encapsulated chip from outside the encapsulated package. A first contact structure of the contact element, which contacts the chip pad, is made of a different electrically conductive material than the exposed portion of the contact element, i.e., the second contact structure.This makes it possible, for example, to contact the chip pad with the same electrically conductive material as the chip pad and to contact the exposed portion of the second contact structure with another electrically conductive structure, which is preferably made of the same material as the second contact structure. Clearly, the contact element can serve as a robust electrically conductive material interface.

[0013] For example, a bimetallic or multimetallic integrally formed contact element can be provided which enables the provision of an electrical connection for an encapsulated chip pad in a simple and efficient manner, without the need to establish connections between different metals of the chip pad and contact element on the one hand, and between the contact element and an external electrically conductive contact structure on the other. This simplifies the packaging of the chip and provides a simple and robust solution for chip packaging. The contact element can contact the chip pad in a mechanically robust and stable manner, while also leaving the surface portion of the second contact structure extending beyond the encapsulation free for establishing a further electrically conductive connection between the second contact structure and the electronic periphery.In other words, the exposed portion of the second contact structure can function as a "package pad." This ensures an even more stable and reliable mechanical connection than using bond wires that directly contact the electronic chip. Directly connecting a bond wire to an electronic chip can require the application of pressure to the sensitive semiconductor chip, leading to the risk of damaging the latter. By using a bimetallic or multimetallic contact element, which enables smoother wire bonding and generally easier connection to the chip pad, the mechanical shock to the chip can be reduced, thus ensuring appropriate protection of the chip (e.g., a semiconductor die) during packaging.Furthermore, connecting a bond wire foot in the form of a bi- or multi-metallic stack allows the use of all types of chip topside metals, especially existing technologies with their topside metallization.

[0014] According to the exemplary embodiments, at least one of the at least one pad has at least one surface portion made of the first electrically conductive material. Thus, an undesirable additional material bridge between the pad and the contact element by the contact element can be avoided. Description of further exemplary embodiments

[0015] Further exemplary embodiments of the packages and the method are explained below.

[0016] In the context of the present application, the term “package” can in particular refer to at least one at least partially encapsulated electronic chip with at least one external electrical contact.

[0017] The term "electronic chip" may, in particular, refer to a semiconductor chip having at least one integrated circuit element (e.g., a diode or a transistor) in a surface portion thereof. The electronic chip may be a bare die or may be pre-packaged or encapsulated.

[0018] In the context of the present application, the term "encapsulation" can, in particular, refer to a substantially electrically insulating and preferably thermally conductive material that surrounds (e.g., hermetically surrounds) an electronic chip and optionally a portion of a carrier in order to provide mechanical protection, electrical insulation, and optionally contribute to heat dissipation during operation. Such an encapsulation can, for example, be a mold compound. Encapsulation by molding can, for example, be carried out by injection molding or transfer molding.

[0019] In the context of the present application, the term "chip carrier" may, in particular, refer to an electrically conductive structure that serves as a support for the one or more chips and may also contribute to the electrical connections between the chip(s) and the peripherals. In other words, the carrier may fulfill a mechanical support function and an electrical connection function.

[0020] In the context of the present application, the term "contact element" can in particular refer to an integrally formed electrically conductive body comprising at least two different electrically conductive materials, one of which represents a first contact structure and the other of which represents a second contact structure. The first contact structure and the second contact structure can have a material interface inside the contact element. The first contact structure can be configured to contact a chip pad, and the second contact structure can be configured to provide an electrically conductive coupling between the first contact structure and the exposed portion of the second contact structure. The first contact structure and the second contact structure can form a bilayer or a multilayer.

[0021] In one embodiment, the first electrically conductive material can be, for example, a pure metal, a metal with additives, or an alloy. The at least one pad can, in particular, also be made of the first electrically conductive material. The second electrically conductive material can be different from the first electrically conductive material and can be, for example, a pure metal, a metal with additives, or an alloy. The second metal can be different from the first metal.

[0022] In one embodiment, the contact element or bonding foot may be a bimetallic or multimetallic structure, which may allow for more gentle bonding parameters. It is also possible to use a bimetallic or multimetallic contact element for mounting (in particular, soldering) another component on the chip.

[0023] In one embodiment, the first contact structure may be a first layer formed only from the first metal or the first electrically conductive material. Accordingly, the second contact structure may be a second layer on the first layer and formed only from the second metal or the second electrically conductive material. The first metal or the first electrically conductive material may be made of a different material than the second metal or the second electrically conductive material. As mentioned above, the package may include a chip carrier on which the electronic chip is mounted.For example, such a chip carrier may comprise a lead frame and / or a ceramic plate (or another electrically insulating body made of another material, for example silicon nitride or aluminum oxide), which is covered on both opposite main surfaces with a corresponding metallic layer (in particular an active metal braze (AMB), substrate and / or a direct copper bond (DCB), substrate). Thus, a suitable mounting base for mounting the chip can be created.

[0024] In one embodiment, the chip carrier is at least partially electrically conductive. In such an embodiment, the chip carrier can also contribute to the electrical connection of the electronic chip. For example, a further pad on the main surface of the electronic chip, which faces the chip carrier, can be electrically conductively coupled to the chip carrier.

[0025] In a further embodiment, the chip carrier is a lead frame. Such a lead frame may be a plate-like metallic structure, which may be patterned to form one or more mounting sections for mounting the one or more electronic chips of the package and one or more conductor sections for electrically connecting the package to an electronic environment when the electronic chip(s) is / are mounted on the lead frame. In one embodiment, the lead frame may be a metal plate (in particular made of copper), which may be patterned, for example, by means of stamping or etching. Forming the chip carrier as a lead frame is a cost-effective and mechanically and electrically advantageous configuration, in which a low-resistance connection of the at least one electronic chip can be combined with a robust support capability of the lead frame.Furthermore, a lead frame can contribute to the thermal conductivity of the package and can dissipate heat generated during operation of the electronic chip(s) due to the high thermal conductivity of the metallic material (particularly copper) of the lead frame. A lead frame can, for example, comprise aluminum and / or copper.

[0026] In one embodiment, the chip carrier has at least one surface portion comprising or consisting of a third electrically conductive material (e.g., an alloy comprising copper), wherein the third electrically conductive material in particular comprises or consists of the second electrically conductive material (e.g., copper). In such an embodiment, the electrically conductive surface of the chip carrier can be used to establish an electrical connection to the one or more semiconductor chips. If the chip carrier also has an electrically insulating portion, this can contribute to suitable electrical insulation of the electronic chip with respect to an electronic periphery.

[0027] In one embodiment, the chip carrier is connected to at least one further pad of the electronic chip, wherein the at least one pad is formed on one main surface of the electronic chip and the at least one further pad is formed on an opposite, other main surface of the electronic chip. Some electronic chips have pads on their two opposite main surfaces. One example is an electronic chip with vertical current flow. For example, a transistor chip may have a source pad and a gate pad on one main surface and a drain pad on the other, opposite main surface. In such an embodiment, one or more contact elements may be used to contact a first part of the pads of the electronic chip, whereas the electrically conductive chip carrier is used to contact the at least one other part of the pads of the electronic chip.

[0028] In one embodiment, the package comprises at least one electrically conductive protrusion protruding from the chip carrier, in particular up to a vertical plane to which the contact element extends. For example, such an electrically conductive protrusion may be a block, a post, or a pillar, e.g. made of copper, which provides a vertical connection between the electrically conductive chip carrier and the upper main surface of the chip via the contact element. The electrically conductive protrusion may extend up to the same plane as the contact element. This then enables a connection between the contact element and the protrusion by means of a planar structure, such as a redistribution layer (RDL).

[0029] In one embodiment, the at least one electrically conductive protrusion extends through the encapsulation to be exposed relative to the encapsulation. In such an embodiment, the electrically conductive protrusion can be reliably mechanically connected and electrically insulated using the same encapsulation used to encapsulate the chip and parts of the contact element. The result is a compact and reliable package.

[0030] In one embodiment, the at least one electrically conductive projection comprises or is made of a fourth electrically conductive material, wherein the fourth electrically conductive material in particular comprises or is made of one of the second electrically conductive material and the third electrically conductive material. If the electrically conductive projection is made of the second and / or the third electrically conductive material, which is also the second contact structure of the contact element and / or the carrier, a (for example horizontal) connection can be established between the electrically conductive projection and the contact element, which extends from the encapsulation, without a further material bridge. A connection to the carrier can then also be established in a simple manner.

[0031] In one embodiment, the method comprises mounting the electronic chip onto a chip carrier. It is further possible to attach an electrically conductive protrusion to the chip carrier. This can be done before encapsulating a portion of the protrusion. Thus, the chip carrier and the electrically conductive protrusion can also be partially encapsulated during the encapsulation process.

[0032] In one embodiment, the encapsulation comprises or consists of an electrically insulating material. As a result, the encapsulation material can contribute to the electrical insulation of the chip, the contact element, optionally a chip carrier, and optionally an electrically conductive projection.

[0033] In one embodiment, the contact element is a bimetallic structure, in particular an aluminum-copper bimetallic structure. Such a bimetallic structure, i.e., a contact element consisting of two different metallic materials with a material interface therebetween, is easy to manufacture and highly efficient for providing a package according to an exemplary embodiment. For example, such a bimetallic structure can be a bimetallic layer or plate. If one of the metals of the bimetallic structure is aluminum, it is possible to contact aluminum pads of semiconductor chips. If the other metal of the bimetallic structure is copper, a suitable connection of such an aluminum pad to copper lead frames or copper pillars or pins is also possible.This allows for a compact package that is robust against damage even under difficult conditions and avoids the need for material bridges to establish contact between the chip pad and an electronic environment.

[0034] In one embodiment, the package comprises an electrically conductive connection structure on a surface portion of the contact element (in particular, on the second contact structure thereof), which surface portion is exposed with respect to the encapsulation. Such an electrically conductive connection structure can be made of the same material as the second contact structure exposed with respect to the encapsulation. Then, a direct connection can be formed between the contact element and such an electrically conductive connection structure without creating a further transition between metallic materials, which could cause problems during soldering.

[0035] For example, the electrically conductive connection structure may comprise at least one of the group consisting of a redistribution structure (in particular a redistribution layer which is arranged at least partially on the encapsulation and on the contact element), a clamp, a wire bond, and a ribbon bond.

[0036] A terminal may be a three-dimensionally curved plate-like connecting element having two planar sections to be connected to an upper main surface of the respective electronic chip and an upper main surface of the chip carrier, the two said planar sections being connected by means of an inclined section.

[0037] As an alternative to such a clamp, it is possible to use a wire bond or ribbon bond, which is a flexible, electrically conductive, wire- or ribbon-shaped body having one end portion connected to the upper main surface of the respective chip and an opposite other end portion electrically connected to the chip carrier.

[0038] A redistribution structure (in particular a redistribution layer) can be referred to as a multilayer structure of electrically conductive elements in a dielectric matrix, which translates, with respect to electrically conductive connection surfaces, between a small chip size and a larger size of another electronic element to be connected to the encapsulated chip via the redistribution structure, in particular on a top side thereof.

[0039] In one embodiment, the electronic chip is a transistor chip having a source pad, a drain pad, and a gate pad as the at least one pad. In particular, the source pad and the gate pad may be formed on the same main surface of the electronic chip and may each be coupled to a corresponding contact element. The drain pad may be formed on an opposite, other main surface of the electronic chip. Such a transistor chip may be a chip that fulfills the function of a transistor, in particular a field-effect transistor. In particular, a source pad and a gate pad may be formed on one main surface of such a transistor chip, whereas a gate pad is formed on an opposite, other main surface of the transistor chip. Such a transistor chip may be used, for example, for semiconductor power applications.

[0040] In one embodiment, the first metal is aluminum. This allows the contact element to be used to directly contact an aluminum pad of a semiconductor chip. Conventionally, the combination of a semiconductor chip having an aluminum pad with another electrically conductive connection structure (e.g., a lead frame) made of copper leads to problems due to the different metallic materials. These problems can be overcome by the bimetallic or multimetallic contact element, which is used as a metal-to-metal connection according to an exemplary embodiment.

[0041] In one embodiment, the second metal is copper. When the second metal is copper, subsequent connection of the exposed portion of the contact element to an electrical periphery is simplified, which in many cases is formed from copper. This applies to copper lead frames, printed circuit boards with copper structures, and copper columns as electrically conductive projections. Wire bonds, terminals, and ribbon bonds are also often made of copper.

[0042] In one embodiment, a thickness of the first contact structure is different from, in particular smaller than, a thickness of the second contact structure. The first contact structure can be a layer made of the first metal. The second contact structure can be a layer which is connected to the first contact layer and is made of the second metal. Such a multilayer bimetallic or multimetallic contact element is compact and robust, as well as simple and inexpensive to manufacture. Furthermore, such a double-layer contact element makes it possible to use the individual thicknesses of the individual layers of the integral contact element as design parameters for setting the desired properties of the contact element. For example, the first contact structure which is connected to the chip pad can have the function of forming an electrical connection of the chip pad without a material bridge.A relatively small thickness of the first contact structure is therefore sufficient in many cases. In contrast, the second contact structure can serve to establish an electrical connection at the exposed surface of the contact element, in many cases a copper coupling surface. However, copper is not only inexpensive and convenient to process, but also has very high thermal conductivity. Providing the second contact structure from a thick copper layer can therefore avoid intermetallic connections on both opposite sides of the contact element, while simultaneously providing a thermally highly suitable contact element.

[0043] Alternatively, the thicknesses of the first contact structure and the second contact structure may be the same.

[0044] In one embodiment, the contact element is configured as a multi-metallic stack, which, for example, comprises three or more stacked contact structures. In particular, the contact element may additionally comprise a third contact structure between the first contact structure and the second contact structure. Since the function of the first and second metals of the contact element is to establish connections to the chip pad and an electronic periphery of the package without material bridges, there is design freedom to arrange at least one further third contact structure (in particular a third contact layer) between the first contact structure and the second contact structure. The material properties of the third contact structure can then be adapted according to the requirements of a specific application. For example, properties such as corrosion resistance, high electrical conductivity, high thermal conductivity, etc.by means of the third contact structure. It is possible that a vertical extension of the third contact structure is even greater than a vertical extension of the first contact structure and the second contact structure, so that the physical properties of the contact element are determined by the third contact structure.

[0045] In particular, the third contact structure may comprise or consist of a material having a higher thermal conductivity, a higher electrical conductivity, and / or a lower elastic modulus than at least one of the first contact structure and the second contact structure. If the third contact structure is configured from a material having a very high thermal conductivity and / or electrical conductivity (for example, graphene), the thermal and / or electrical performance of the package can be further improved. In another advantageous embodiment, the third contact structure may be made of a material having a low elastic modulus, i.e., is very soft, so that it can serve as a stress buffer and thus improve the reliability of the package.

[0046] In one embodiment, the contact element is plate-shaped or strip-shaped. In particular, the contact element can be a multilayer (in particular two-layer) multimetallic (in particular bimetallic) platelet. Such a platelet can be easily formed from a larger plate or strip, for example by stamping. Furthermore, the plate-shaped geometry of the contact element has the advantage that it can be robustly contacted both with the chip pad and with the electronic periphery of the package. Unlike a much more sensitive wire bond, significant pressure can be exerted on such a plate-like contact element without the risk of damaging the contact element, the electronic chip, or the package.

[0047] In one embodiment, a thickness of the contact element is in a range between 10 µm and 1 mm, in particular in the range between 20 µm and 500 µm, further in particular in a range between 50 µm and 200 µm. For example, the thickness of the contact element can be 100 µm. However, a length and a width of the contact element can be greater than its thickness. For example, the length and the width of the contact element can be at least twice, in particular at least five times, its thickness. This provides a robust contact element.

[0048] In one embodiment, the electrically conductive contact element is a strip element (tape-bond-shaped element) comprising the first contact structure, which has a first layer made of the first electrically conductive material, and the second contact structure, which has a second layer made of the second electrically conductive material. The strip element can be provided by cutting an endless strip consisting of the strip element material. Thus, the strip element can be a metallic tape / strip element, wherein one layer in particular comprises a first layer of the first contact structure and a second layer of the second contact structure. The corresponding layers lie on top of one another and form, for example, a layered structure. The strip element can be a flexible and in particular plastically deformable element.For example, the first layer of the strip element can be made of a first metal, such as aluminum, and the second layer of the strip element can be made of a second metal, such as copper. Thus, the strip element can be used to create strip pieces for connecting to the pad or chip and another component or conductive structure. The strip element can be arranged on the pad and can be electrically coupled to the pad, for example, using strip bonding technologies. Thus, an additional Cu coating process on the chip can be unnecessary.

[0049] In one embodiment, the strip element has at least one third contact structure between the first contact structure and the second contact structure, wherein the at least one third contact structure in particular has or consists of a material which has a higher thermal conductivity, a higher electrical conductivity and / or a lower modulus of elasticity than at least one of the first contact structure and the second contact structure.

[0050] In one embodiment, the strip element is bent such that the strip element has a curved profile, in particular one of a U-shape, a V-shape, a Z-shape and a W-shape.

[0051] In one embodiment, the strip element has a first end, a second end, and a central section disposed between the first end and the second end, wherein the first end and the second end are coupled to the pad and the central section is spaced from the pad.

[0052] In particular, the curved profile of the strip elements can be formed by bending the strip element before arranging it on the respective pad. In particular, a variety of robust profiles for the strip elements are possible. For example, a strip element having a U- or V-shaped profile can be bonded to the pad with its first end and its second end, wherein the central part is spaced from the pad and in particular extends out of the encapsulation to provide a connection to external components, for example an electrically conductive connection structure, for example a redistribution layer. Alternatively, a Z-shaped profile of the strip element is also bendable, such that the first end of the strip element is bonded to the pad and the second end of the strip element is spaced from the pad and can be connected to further external components.To provide a plurality of bonding points, in particular more than two, on the pad or to the external component, the strip element may be bent in the form of a W-shape, i.e., in a meander-like shape. Furthermore, the bent strip element may be completely embedded in an encapsulation, with only a part, in particular a part of the central section, not covered by the encapsulation.

[0053] In one embodiment, the method comprises attaching the contact element to the at least one pad prior to encapsulation. By connecting the contact element to the chip pad prior to encapsulation, the semiconductor chip is easily accessible and the handling procedure is simple. For example, the connection can be established by soldering, welding, etc.

[0054] In one embodiment, the method further comprises (prior to attaching the strip element forming the electrically conductive contact element to the at least one pad) cutting a strip element from an endless strip, for example a bimetallic foil or tape (for example comprising an aluminum and a copper layer) having the first layer and the second layer.

[0055] In one embodiment, the method further comprises bending the strip element such that the profile of the strip element is curved, in particular a curved U-shape, a curved V-shape, a curved Z-shape, and a curved W-shape, before the strip element is attached to the at least one pad. In particular, the respective strip elements can be bent before the package is encapsulated. For example, the bent strip elements enclose open cavities. However, during encapsulation, the encapsulation flows into the respective cavities to completely surround and thus embed the respective strip element. Thus, the risk of unwanted air pockets in the package can be reduced because the encapsulation step is performed after the strip elements have been mounted on the respective pads.

[0056] In another embodiment, the method comprises attaching the contact element to the at least one pad after encapsulation. Thus, it is alternatively also possible to first encapsulate the electronic chip with the encapsulation and subsequently form an access opening that extends through the encapsulation to the chip pad. The contact element can then be inserted into such an access opening after encapsulation. Such an embodiment has the advantage that the second contact structure of the contact element does not have to be separately exposed after encapsulation.

[0057] In one embodiment, the method comprises exposing the contact element by removing excess encapsulation material after encapsulation. This can be accomplished mechanically and / or chemically.

[0058] In one embodiment, the method comprises exposing the contact element by preventing the encapsulation of an exposed portion of the contact element during encapsulation. In addition to or alternatively to removing excess encapsulation that inadvertently covers the surface of the second contact structure of the contact element, it is possible to take a measure to prevent an encapsulation material from being formed on the surface to be exposed. For example, this can be accomplished by covering the surface of the second contact structure, which is to remain exposed after encapsulation, with a surface portion of a molding tool.For example, the electronic chip can be inserted into a mold with the contact element already pre-assembled, with the surface of the contact element, which is to remain exposed, directly contacting a portion of the mold. A subsequently introduced preform of a mold compound can then flow into the mold but is prevented from flowing onto the surface of the contact element, which is to remain exposed. Additionally or alternatively, it is possible to cover the surface of the contact element, which is to remain uncovered by the encapsulation, with a protective film during encapsulation. If such a protective film is attached (e.g., glued) to the surface of the contact element, which is to remain exposed, removing the film after encapsulation makes it possible to obtain the contact element with an exposed surface.

[0059] Thus, the method may comprise exposing the second contact structure with respect to the encapsulation by means of at least one of the group consisting of: - covering at least a portion of the second contact structure with a protective film during encapsulation and removing the protective film after encapsulation; - contacting at least a portion of the second contact structure during encapsulation with a surface of an encapsulation tool to prevent the encapsulation from covering the contacted portion; - Cleaning, in particular mechanical and / or chemical cleaning, of at least a portion of the second contact structure after encapsulation, in order to thereby remove encapsulation material from the portion.

[0060] Of course, other methods are also possible.

[0061] In one embodiment, the method comprises refining an exposed surface of the second contact structure, in particular by forming a functional layer on the second contact structure. Thus, the exposed surface of the second contact structure can be subjected to a post-treatment to improve its properties desired for performing suitable packaging. Refining its surface can, for example, comprise adding a silver layer to improve solderability. It is also possible to apply a nickel-gold protective layer. Such a layer protects the contact element and promotes its suitability to serve as an electrically conductive connection. Refining the exposed surface of the contact element can also comprise a cleaning process, for example, mechanical polishing and / or a chemical deoxidation process.Furthermore, a thin aluminum oxide layer can alternatively be formed on the exposed second contact structure as protection against oxidation of the contact element. For example, a coating process can be performed to form additional material on the exposed surface of the second contact structure. This can be accomplished, for example, by means of a galvanic deposition procedure. In general, such a refinement of the exposed surface can improve the solderability, bondability, or coatability of the contact element. Electroless plating is also a possible option.

[0062] In one embodiment, the at least one electronic chip comprises one of the group consisting of a controller circuit, a driver circuit, and a power semiconductor circuit. All of these circuits can be integrated in one semiconductor chip or be separate in different chips. For example, a corresponding power semiconductor application can be realized by the chip(s), wherein the integrated circuit elements of such a power semiconductor chip can comprise at least one transistor (in particular a MOSFET, metal oxide semiconductor field effect transistor), at least one diode, etc. In particular, circuits can be produced which fulfill a half-bridge function, a full-bridge function, etc.

[0063] In one embodiment, the encapsulation comprises a molding compound. Thus, the encapsulation can comprise a molded body, in particular a plastic molded body. For example, a correspondingly encapsulated body (in particular the chip with the carrier) can be provided by placing the body or bodies between an upper mold and a lower mold and injecting a liquid molding material into it. After the molding material has solidified, the formation of the encapsulation is complete. If desired, the molded body can be filled with particles that improve its properties, for example its heat dissipation properties.

[0064] In other exemplary embodiments, the encapsulation may also be a laminate or a casting compound.

[0065] A semiconductor substrate, i.e., a silicon substrate, can be used as the substrate or wafer for the semiconductor chips. 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.

[0066] Clearly, the contact element can form a particularly stable pad that extends from the encapsulation.

[0067] The present invention also provides the following aspects: According to one aspect, a package is provided comprising an electronic chip having at least one pad, an encapsulation encapsulating at least the electronic chip, and an electrically conductive contact element extending from the at least one pad and through the encapsulation to be exposed with respect to the encapsulation, wherein the electrically conductive contact element comprises a first contact structure made of a first electrically conductive material on the at least one pad and a second contact structure made of a second electrically conductive material and exposed with respect to the encapsulation. According to one aspect, a package is provided comprising an at least partially electrically conductive chip carrier, an electronic chip mounted on the chip carrier, the electronic chip being provided with a pad having an outer surface comprising a first metal, an electrically conductive contact element extending from the pad, and an encapsulation at least partially encapsulating the contact element and the electronic chip, the contact element comprising a first contact structure on the at least one pad and comprising the first metal and a second contact structure having an exposed surface not covered by the encapsulation and comprising a second metal. According to one aspect, a method of manufacturing a package is provided, the method comprising at least partially encapsulating an electronic chip having at least one pad with an encapsulation, providing an electrically conductive contact element extending from the at least one pad and through the encapsulation to be exposed with respect to the encapsulation, and configuring the electrically conductive contact element to have a first contact structure made of a first electrically conductive material on the at least one pad and to have a second contact structure made of a second electrically conductive material and exposed with respect to the encapsulation.

[0068] The above and other objects, features and advantages of the present invention will become apparent from the following description and the appended claims, taken in conjunction with the accompanying drawings in which the same parts or elements are designated by the same reference numerals. Short description of the drawings

[0069] The accompanying drawings, which are included to provide a further understanding of exemplary embodiments of the invention and which constitute a part of the specification, illustrate exemplary embodiments of the invention.

[0070] In the drawings: Shows Fig. 1 a cross-sectional view of a package according to an exemplary embodiment. Shows Fig. 2 a cross-sectional view of a package according to another exemplary embodiment. Shows Fig. 3 is a flowchart of a method for manufacturing a package according to an exemplary embodiment. Shows Fig. 4 is a cross-sectional view of a package according to yet another exemplary embodiment. Shows Fig. 5 is a cross-sectional view of a package according to yet another exemplary embodiment. Show Fig. 6 to 11 Cross-sectional views of structures produced during the manufacture of a package used in Fig. 4 or Fig. 5, according to an exemplary embodiment. Shows Fig. 12 is a cross-sectional view of a package according to yet another exemplary embodiment. Shows Fig. 13 is a cross-sectional view of a package according to yet another exemplary embodiment. Shows Fig. 14 a cross-sectional view of a contact element of a package according to an exemplary embodiment. Shows Fig. 15 is a cross-sectional view of a contact element of a package according to another exemplary embodiment. Shows Fig. 16 is a cross-sectional view of a package according to yet another exemplary embodiment. Shows Fig. 17 is a schematic view of an endless belt for forming strip elements according to an exemplary embodiment. Shows Fig. 18 is a schematic view of curved strip elements according to an exemplary embodiment. Detailed description of exemplary embodiments

[0071] The representation in the drawing is schematic and not to scale.

[0072] Before describing exemplary embodiments in more detail with reference to the figures, some general considerations are summarized on the basis of which the exemplary embodiments were developed.

[0073] According to an exemplary embodiment, a contact element in the form of a bimetallic or multimetallic bonding pad is provided as an interconnect for ultra-thin packages. Such a package can be formed in a very compact manner and with low effort, using existing chip technologies, without the need to specifically adjust front-side metallization. This can be accomplished by providing a simple bimetallic or multimetallic interconnect in the form of the contact structure.

[0074] By directly contacting chips using laser drilling, vias, and redistribution technology, chip embedding variants have been established that lead to increased electrical and thermal performance. However, conventional approaches have the disadvantage that via connection requires chip technology with a suitable front-side metallization of the chip, particularly a copper pad. Furthermore, plating the copper vias incurs additional costs.

[0075] To overcome these disadvantages, among others, an exemplary embodiment provides a multi-metallic bonding pad (e.g., aluminum-copper) for a chip connection in the form of the aforementioned contact element. By taking this measure, a thin package can be formed by encapsulation, in particular using a molding compound or a laminate. Subsequently, it may be possible to thin the encapsulation material until the copper side of the bonding pad protrudes beyond the (e.g., molded-body or laminate-like) encapsulation.

[0076] Subsequently, a further electrically conductive connection structure (e.g., a redistribution structure) may be formed to be electrically coupled to the exposed surface of the contact element. For example, it is possible to perform a copper plating on the encapsulation and on the exposed surface of the second contact structure. The latter may be made of a different metal than the first contact structure of the contact element, which is directly connected to the encapsulated semiconductor chip pad. Forming an electrically conductive connection structure, e.g., a redistribution structure, may also include lamination of a copper clad with a corresponding recess at the position where the contact element extends out of the encapsulation. Subsequently, a copper plating process may be performed.The electrically conductive connection structure, such as the redistribution structure, can be formed directly on the bonding pad. In other words, the bonding pad or contact element can serve as a package pad. Such a contact element can be formed by cutting or punching a portion of a bilayer board or tape, for example, having an aluminum layer integrally formed with a copper layer.

[0077] The aforementioned embodiments have the advantage that chip technologies that do not have suitable front-side metallization for a via connection can also be implemented. Therefore, it is no longer necessary to apply a copper plating process to a chip, which traditionally requires significant effort.

[0078] According to an exemplary embodiment, a bimetallic connection in the form of a contact element may be provided to contact a chip pad on one side thereof. An opposite, other side thereof may be exposed with respect to an encapsulation and may be used to contact the encapsulated electronic chip with an electronic environment of the package. In one embodiment, it is possible to perform printed circuit board processes for further processing of the package.

[0079] According to an exemplary embodiment, a bonding foot composed of different metallic materials may be used, which is in particular realized as a bimetallic two-layer structure. One of the metals corresponding to one of the layers may be, for example, aluminum, which may be connected to an aluminum chip pad using standard methods. The other metal and the other layer may be, for example, copper, which may serve as a base for further redistribution structures or as a pad to be connected, for example, to another copper structure (such as a copper column, a printed circuit board, or a lead frame).

[0080] In one embodiment, the bonding foot or contact element can be connected to the chip pad using ultrasonic bonding. It is possible to encapsulate the bonded chip with a laminate, a mold, or a plastic.

[0081] Exposing the surface of the contact element can be performed by cleaning processes for refining or cleaning the exposed surface. It is therefore possible to use the exposed metallic surface of the contact element as a pad, in particular a wire bonding pad. Such a pad-like exposed surface of the contact element can also be used for chip embedding processes. It is further possible to refine the pad-like exposed surface of the contact element for wire bonding. Furthermore, it is possible to refine the pad-like exposed surface on the contact element to provide a solder resist or for pre-soldering.

[0082] Further formation of redistribution structures by direct copper plating or lamination with a copper cladding and copper plating can also be performed. It is then possible to produce molded and / or laminated packages based on the described principle.

[0083] In brief, an exemplary embodiment may provide a semiconductor package having a semiconductor device, for example, a chip. An insulating material as an encapsulation may cover at least one surface of the semiconductor chip. The semiconductor package may further comprise a contact element. The contact element may be arranged on the surface of the semiconductor chip. Additionally, the contact element may form a via in the insulating material. The contact element may have at least two different metallic layers.

[0084] Fig. 1 shows a cross-sectional view of a package 100 according to an exemplary embodiment.

[0085] The package 100 shown comprises an electronic chip 102, for example, a semiconductor chip. In the embodiment shown, the electronic chip 102 is provided with a pad 104, for example, made of aluminum, on an upper main surface of the electronic chip 102. An encapsulation 106, for example, a molding compound, partially encapsulates the electronic chip 102 and an electrically conductive contact element 108. The electrically conductive contact element 108, which is embodied here as a bimetallic double-layer stack, extends from (and is connected to) the pad 104. The electrically conductive contact element 108 extends vertically through the encapsulation 106 such that the contact element 108 is exposed with respect to the encapsulation 106. More specifically, the contact element 108 comprises a first contact structure 110 made of a first electrically conductive material, for example, aluminum, on the pad 104.The contact element 108 additionally has a second contact structure 112 made of a second electrically conductive material, for example, copper. As shown in . Fig. 1, a top surface of the second contact structure 112 is exposed with respect to the encapsulation 106 so that it is accessible from outside the package 100.

[0086] The Package 100 according to Fig. 1 has the advantage that the exposed surface 131 of the second contact structure 112 of the contact element 108 can serve as a pad made of a different material than the metal of the chip pad 104. This allows the exposed surface 131 to be directly connected to another electronic element made of the second metal, which is also the second contact structure 112, without an undesired intermetallic bridge. At the same time, the metal of the chip pad 104 and the metal of the first contact structure 110 of the contact element 108 can be the same, so that an undesired intermetallic bridge is also unnecessary in this area.

[0087] Fig. 2 shows a cross-sectional view of the package 100 according to another exemplary embodiment.

[0088] The Package 100 according to Fig. 2 comprises an electrically conductive chip carrier 114, for example, a copper lead frame. An electronic chip 102, for example, a power semiconductor chip, is mounted (for example, soldered) on the chip carrier 114. A lower main surface 124 of the electronic chip 102 is attached to the chip carrier 114. The electronic chip 102 is provided with a pad 104 having an outer surface comprising a first metal, for example, aluminum. An electrically conductive contact element 108 extends upward from the pad 104 and is connected to the pad 104, for example, by soldering. An encapsulation 106, which is formed, for example, by molding, only partially encapsulates the contact element 108 and the electronic chip 102. As shown, the contact element 108 comprises a first metal layer (for example, an aluminum layer) that forms a first contact structure 110 directly on the pad 104.Furthermore, the contact element 108 includes a second metal layer (e.g., a copper layer) forming a second contact structure 112. As shown, the second contact structure 112 has an exposed upper surface in alignment with an upper surface of the encapsulant 106. The exposed upper surface is not covered by the encapsulant 106. An electrically conductive contact structure 118, embodied here as a clip (made of, for example, copper), provides a connection between the exposed surface 131 of the second contact structure 112 and the chip carrier 114.

[0089] As shown, the terminal 118 (made of copper, for example) can be easily connected to the chip carrier 114 (in particular, a lead frame, which is also made of copper) and to the exposed surface 131 of the second contact structure 112, which can also be made of copper. In contrast, the chip pad 104 and the first contact structure 110 can both be made of aluminum. The material transition from aluminum to copper can thus occur without undesirable intermetallic bridges. This can be achieved by the bimetallic nature of the contact element or bond pad.

[0090] Fig. 3 shows a flowchart 300 of a method for manufacturing a package 100 according to an exemplary embodiment.

[0091] As illustrated by a block 310, the method comprises at least partially encapsulating an electronic chip 102 having at least one pad 104 by means of an encapsulation 106. As illustrated by a block 320, the method may further comprise providing an electrically conductive contact element 108 extending from the at least one pad 104 and through the encapsulation 106 to be exposed with respect to the encapsulation 106. Furthermore, a block 330 shows that the method may additionally comprise configuring the contact element 108 to comprise a first contact structure 110 made of a first electrically conductive material on the at least one pad 104, and a second contact structure 112 made of a second electrically conductive material and exposed with respect to the encapsulation 106.

[0092] Of course, the procedure which is applicable to Fig. 3, other procedures may be added.

[0093] Fig. 4 shows a cross-sectional view of a package 100 according to yet another exemplary embodiment.

[0094] The Package 100 from Fig. 4 comprises an electrically conductive chip carrier 114 (for example, a lead frame, which may be formed of copper) on which an electronic chip 102 is mounted. Furthermore, the package 100, which in Fig. 4, an electrically conductive projection 116 (for example, a copper block) which projects from the chip carrier 114 to a vertical plane to which a contact element 108 extends, as shown in relation to Fig. 1 or Fig. 2. The projection 116 extends through the encapsulation 106 and is exposed at an upper side with respect to the encapsulation 106. The encapsulation 106 may be formed from a dielectric molding compound. The contact element 108 is formed as a double-layer bimetallic structure, i.e., as a plate-shaped aluminum-copper bimetallic double-layer structure. For example, a vertical thickness of the contact element 108 is in a range between 50 µm and 200 µm. The length and width of the contact element 108 in a horizontal plane may be greater than the vertical thickness.

[0095] In the embodiment from Fig. 4, two chip pads 104 are provided on an upper main surface of the electronic chip 102, which are directly connected to the first contact structure 110 of the contact element 108 (e.g., by soldering or welding). For example, the chip pads 104 and the first contact structures 110 can both be made of aluminum. The exposed second contact structures 112 of the two contact elements 108 are, however, exposed with respect to the encapsulation 106, but are aligned at their upper surfaces with the upper surface of the encapsulation 106. Therefore, the second contact structures 112 can serve as pad-like structures made of copper, which allow the encapsulated electronic chip to be indirectly contacted with aluminum pads 104. The exposed upper surface 133 of the electrically conductive protrusion 116 is also on the same vertical plane as the upper main surfaces of the contact elements 108 and the encapsulation 106.Thus, a planar surface is formed, which enables a planar connection between the electrically conductive structures 116, 112. This will be described in more detail below with reference to FIG. Fig. 5. The chip carrier 114 (e.g., a copper lead frame) and the protrusions 116 (e.g., copper blocks) may be made of the same material (e.g., copper) as the second contact structures 112 of the contact elements 108 and may therefore be connected without forming undesirable intermetallic bridges.

[0096] Fig. 5 shows a cross-sectional view of a package 100 according to yet another exemplary embodiment. Differences with respect to the embodiment of Fig. 4 are described below.

[0097] According to Fig. 5, the chip carrier 114 is connected to another pad 122 of the electronic chip 102 on a lower main surface 124 thereof. In the embodiment shown, two pads 104 (designated by reference numerals 104a, 104b) are formed on the upper main surface 120 of the electronic chip 102, and the one further pad 122 is formed on the opposite lower main surface 124 of the electronic chip 102. The package 100 of Fig. 5 additionally includes a planar electrically conductive interconnect structure 118 on an exposed surface portion of the contact element 108, an exposed surface portion of the protrusion 116, and an upper major surface of the encapsulation 106. In the illustrated embodiment, the electrically conductive interconnect structure 118 is configured as a redistribution layer on the encapsulation 106, on the protrusion 116, and on the contact elements 108.

[0098] Since the electronic chip 102 of the package 100 according to Fig. 5 is a transistor chip, it has a source pad 104a, a drain pad 122, and a gate pad 104b. The source pad 104a and the gate pad 104b are formed on the same upper main surface 120 of the electronic chip 102 and are each coupled to a first contact structure 110 of a respective one of the contact elements 108. In contrast, the drain pad 122 is formed on the opposite lower main surface 124 of the electronic chip 102 in direct electrically conductive connection with the chip carrier 114.

[0099] As in the embodiment from Fig. 5, the embodiment of Fig. 4 by also providing a further pad 122 on the lower main surface of the electronic chip 102. This further pad 122 may be electrically connected to one of the chip pads 104a, 104b on the upper main surface of the semiconductor chip 102 via the electrically conductive chip carrier 114, the electrically conductive overhang 116 and the redistribution layer 118 (the latter being formed by structuring one or more copper layers on the upper main surface of the package 100, which in Fig. 4). Illustratively, the redistribution-type electrically conductive connection structure 118 can translate between the small dimensions of the chip world and the larger dimensions of the world of the mounting bases (e.g., a printed circuit board) with which the upper main surface of the package 100 is connected. Fig. 5 can be connected (not shown).

[0100] As in the embodiment from Fig. 4, no undesirable intermetallic bridges are formed except for the interior of the contact elements 108, which may be stacked layers of copper and aluminum. However, such stacked layers can be provided with little effort as a preformed integral multi-layer structure.

[0101] The embodiment from Fig. 5 therefore corresponds to a package 100 with encapsulated transistor chip 102, which has the further pad 122 as drain pad on its lower main surface 124, and has the gate pad 104b and the source pad 104a on its upper main surface 120.

[0102] Fig. 6 to Fig. 11 show cross-sectional views of structures obtained during the manufacture of a package 100 which is Fig. 4 or Fig. 5, according to an exemplary embodiment.

[0103] The chip carrier 114, which is used as a starting point and in Fig. 6 is a structured lead frame.

[0104] Referring to Fig. 7, the method comprises mounting electronic chips 102 on the chip carrier 114 and attaching the electrically conductive projections 116 to the chip carrier 114. The structure shown in Fig. 7 can be obtained by attaching the bare plates, ie the bare semiconductor chips 102, to mounting areas of the structured lead frame, which is shown as an example of a chip carrier 114 in Fig. 6 is shown.

[0105] Furthermore, copper blocks may be mounted as vertical electrically conductive projections 116 on the mounting surface of the chip carrier 114 and extend vertically beyond the upper main surfaces of the electronic chips 102.

[0106] Alternatively, it is also possible for the electrically conductive projections 116 to be formed integrally with the chip carrier 114, ie, without attaching the projections 116 to the carrier 114. For example, material of an original preform of the chip carrier 114 can be etched away so that regions between the projections 116 are selectively removed and the projections 116 remain integrally connected to a plate-shaped portion of the chip carrier 114.

[0107] In yet another exemplary embodiment, it is also possible that the electrically conductive projections 116 are formed after the encapsulation procedure, which is described below with reference to Fig. 9. In such an embodiment, recesses may be etched into an encapsulant 106. Subsequently, material may be introduced into the recesses, forming the protrusions 116. For example, a solder ball may be introduced into such a recess, melted, and subsequently solidified, thus converting into a protrusion 116.

[0108] Referring to Fig. 8, electrically conductive contact elements 108 are provided, each extending from a corresponding one of the pads 104. The contact elements 108 are each provided with a first contact structure 110 made of a first electrically conductive material and connected to the pad 104, and with a second contact structure 112 made of a second electrically conductive material and having an upper free end. As shown, the contact elements 108 are attached to and connected to the pads 104.

[0109] To maintain the structure that Fig. 8, bonding feet as contact elements 108 can thus be attached to the chip pads 104 on the upper main surface of the electronic chips 102. The upper main surfaces of the contact elements 108 can be vertically aligned with the upper main surfaces of the electrically conductive projections 116.

[0110] Referring to Fig. 9, the carrier 114, the electronic chips 102, the protrusions 116, and the chip carrier 114 are partially encapsulated by a molded body-type encapsulation 106. The contact elements 108 extend through the encapsulation 106 but are exposed at a flat, planar, horizontal upper surface of the second contact structures 112 with respect to the encapsulation 106. Flat, planar, horizontal upper surfaces of the protrusions 116 are also exposed with respect to the encapsulation 106.

[0111] If desired or necessary, the contact elements 108 may be treated after encapsulation by removing excess encapsulation material 106 from their upper surfaces. For example, it is possible to mechanically and / or chemically clean the second contact structure 112 after encapsulation to thereby remove encapsulation material 106 from the upper portion of the second contact structures 112.

[0112] However, it is also possible to ensure that the contact elements 108 are exposed by preventing the encapsulation of upper portions of the contact elements 108 during the encapsulation procedure. For example, the exposure of the second contact structures 112 with respect to the encapsulation 106 can be ensured by covering upper portions of the second contact structure 112 with a protective film (not shown) during encapsulation and removing the protective film after encapsulation. Additionally or alternatively, the upper portions of the second contact structure 112 can be contacted with a surface of an encapsulation tool (not shown) during the encapsulation procedure to prevent material of the encapsulation 106 from covering the contacted portion.

[0113] The structure in Fig. 9 can therefore be obtained by encapsulating the structure in Fig. 8, in particular by molding. During this encapsulation procedure, the upper main surfaces of the contact elements 108 and the upper main surfaces of the projections 116 can be prevented from being encapsulated and / or they can be exposed from the encapsulation 106 after encapsulation. This can be achieved, for example, by mechanical treatment (water jet, polishing) and / or chemically (for example, by etching away excess encapsulation material).

[0114] The structure of Fig. 10 can be obtained by forming a redistribution layer as an example of an electrically conductive connection structure 118 on the planar upper main surface of the structure of Fig. 9. This may include attaching and structuring copper foils, depositing copper or another electrically conductive material by means of coating, performing structuring procedures (e.g., lithographic structuring), etc. It is also possible for the electrically conductive connection structure 118 to have electrically insulating layers (not shown) in which the electrically conductive elements of the electrically conductive connection structure 118 may be embedded.

[0115] As in Fig. 11, it is optionally possible to form a further element 135 on the upper main surface of the structure Fig. 10, for example, a passive component such as a ceramic capacitor or an ohmic resistor. As in Fig. 11, multiple packages 100 can be formed at batch level, as described with reference to Fig. 6 to Fig. 11. After such a joint manufacturing process, in which several packages 100 are manufactured simultaneously, the structure can be Fig. 11 to obtain multiple packages 100, which are Fig. 4 or Fig. 5 are shown.

[0116] Fig. 12 shows a cross-sectional view of a package according to yet another exemplary embodiment.

[0117] The embodiment of Fig. 12 shows a package 100 in which an electronic chip 102 with pads 104a, 104b, 122 on both opposite main surfaces is encapsulated in an encapsulation 106, together with a contact element 108 as described above. The second contact structure 112 of the contact element 108 is exposed with respect to the encapsulation 106 and extends to the same vertical plane as the encapsulation 106. Subsequently, a finishing procedure for finishing the exposed surface of the contact element 108 can be carried out. The manufacturing method leading to the package 100 of Fig. 12, can thus comprise a refinement of an exposed surface of the second contact structure 112, for example by forming a functional layer 132 on the second contact structure 112.

[0118] Furthermore, it is possible to use a wire bond as another example of an electrically conductive connection structure 118 between the functional layer 132 and an electrically conductive surface of the chip carrier 114, for example, a copper surface thereof. Thus, it is possible to use a copper wire bond to connect the copper leadframe as the chip carrier 114 to the exposed copper surface of the second contact structure 112, although the chip pads 104a, 104b on the top side of the semiconductor chip 102 may be made of a different material, for example, aluminum. This aluminum material may be connected to the first contact structure 110, which may also be made of aluminum.

[0119] Fig. 13 shows a cross-sectional view of a package 100 according to yet another exemplary embodiment, in which two semiconductor chips 102 are connected in a half-bridge configuration and embedded in the same encapsulation 106. Two contact elements 108 may be used to connect the upper pads 104a, 122 of the two semiconductor chips 102 via a clamp as another example of an electrically conductive connection structure 118. In the shown example, the clamp may extend into recesses 139 formed in the respective second contact structures 112 of the contact elements 108 connected to the two electronic chips 102. Again, it is possible to use, for example, a copper clamp, although the contacted pads 104a, 122 of the shown semiconductor chips 102 may be made of aluminum.

[0120] Fig. 14 shows a cross-sectional view of a contact element 108 of a package 100 according to an exemplary embodiment. The embodiment of Fig. 14 shows a bimetallic two-layer contact element 108 according to an exemplary embodiment.

[0121] In the contact element 108 of Fig. 14, a thickness d of the first contact structure 110 is smaller than a thickness D of the second contact structure 112. As shown, the thickness d of the layered first contact structure 110 may be thinner than the thickness D of the layered second contact structure 112. For example, a thin aluminum layer having the thickness d and forming the first contact structure 110 may be integrally bonded to a thicker (thickness D>d) copper layer forming the second contact structure 112. By taking this measure, the lower cost, better processability, and high thermal conductivity of copper can be combined with a thin aluminum layer for acting as a connection to an aluminum pad of a semiconductor chip, without forming intermetallic bridges.

[0122] Fig. 15 shows a cross-sectional view of a contact element 108 of a package 100 according to another exemplary embodiment.

[0123] In this embodiment, the contact element 108 has a third contact structure 111 as an additional layer, which is arranged between the layered first contact structure 110 and the layered second contact structure 112. Thus, the embodiment of Fig. 15 three connected layers (see reference numerals 110, 111, 112). The bottom layer forms the first contact structure 110, the top layer forms the second contact structure 112, and the third contact structure 111 is arranged as a third layer between them. For example, the first contact structure 110 may be made of aluminum, the second contact structure 112 may be made of copper, and the third contact structure 111 may be made of yet another metallic material, which may be selected by a circuit designer based on the requirements of a particular application.

[0124] Fig. 16 shows a cross-sectional view of a package 100 according to yet another exemplary embodiment.

[0125] The package 100 shown comprises electronic chips 102, for example, semiconductor chips. The electronic chips 102 are provided with pads 104, for example, made of aluminum, on upper main surfaces of the electronic chips 102. An encapsulation 106, for example, a molding compound, partially encapsulates the electronic chip 102 and an electrically conductive contact element 108. In the embodiment shown, the electrically conductive contact element 108 is a strip element (ribbon-bond-shaped element) comprising the first contact structure 110, which has a first layer of the first electrically conductive material, and the second contact structure 112, which has a second layer of the second electrically conductive material.

[0126] For example, the first layer of the strip element can be made of a first metal, such as aluminum, and the second layer of the strip element can be made of a second metal, such as copper. Thus, the strip element creates strip pieces for connecting to the pad or chip and another component or conductive structure. The strip element is electrically coupled to the pad 104 and is electrically coupled to the pad 104, for example, using strip bonding technologies.

[0127] The strip elements have a first end 1601, a second end 1602, and a central section 1603 disposed between the first end 1601 and the second end 1602. In the exemplary embodiment of Fig. 16, the first end 1601 and the second end 1602 are electrically coupled to the respective pad 104 and the central section 1603 is spaced from the respective pad 104. In the exemplary embodiment of Fig. 16, the strip elements have a U-shape. The outer layer forms the second contact structure 112, which is connected in the region of the central section 1603 to another component, such as the electrically conductive connection structure 118, for example, a redistribution structure or a lead frame. An inner layer of the strip element forms the first contact structure 110, which is connected by its ends 1601, 1602 to a respective pad 104. The first end 1601 and the second end 1602 are spaced apart from one another along the pad 104. At the respective ends 1601, 1602, the material of the first contact structure 110 partially encloses and covers the respective end surfaces of the second contact structure 112, so that material of the first contact structure 110 can contact the respective pads 104 of the semiconductor chip 102 and be bonded thereto.Thus, the strip elements extend vertically through the encapsulation 106 such that the strip elements are exposed with respect to the encapsulation 106. More specifically, the strip elements comprise layers of the first contact structure 110 made of a first electrically conductive material, for example, aluminum, on the pad 104. The strip elements additionally comprise a layer of the second contact structure 112 made of a second electrically conductive material, for example, copper.

[0128] Furthermore, in the exemplary embodiment of Fig. 16 shows a further electronic chip 1604, which has a front-side metallization 1605 and a back-side metallization 1606. The back-side metallization 1606 can be electrically connected directly to the electronic chip 102. Corresponding electrically conductive elements 108 are connected to the front-side metallization 1605 such that the front-side metallization 1605 can function as a corresponding pad 104, according to the claimed solution. The electrically conductive contact elements 108 couple the front-side metallization 1605 to the electrically conductive connection structure 118 and can also be U-shaped and comprise respective first contact structures 110 having a first layer of the first electrically conductive material and second contact structures 112 having a second layer of the second electrically conductive material.The 1603 chip can be an IGBT (insulated gate bipolar transistor), a MOSFET (metal oxide semiconductor field effect transistor), a diode or an integrated circuit IC.

[0129] Fig. 17 shows a schematic view of an endless belt 1701 for forming strip elements according to an exemplary embodiment.

[0130] The strip elements are provided by cutting the endless strip 1701, which consists of the strip element material. Thus, the strip element can be a metallic strip / strip element, wherein one layer comprises, in particular, a first layer of the first contact structure and a second layer of the second contact structure. The strip element can be a flexible and, in particular, plastically deformable element.

[0131] Fig. 18 shows schematic views of curved strip elements according to an exemplary embodiment. The strip elements of Fig. 18 are bent such that the strip element forms a curved profile, in particular a U-shape or a V-shape. In particular, the curved profile of the strip elements can be formed by bending the strip element before arranging it on the corresponding pad. In particular, a variety of robust profiles for the strip elements are possible. For example, a strip element having a U- or V-profile can be bonded to the pad 104 with its first end 1601 and second end 1602, wherein the central part 1603 is spaced from the pad 104 and in particular extends out of the encapsulation to provide a connection to external components, for example a component carrier.

[0132] As from Fig.18, the ends 1601, 1602 are folded such that the material of the first contact structure 110 partially encloses and covers the respective end surfaces of the second contact structure 112, so that material of the first contact structure 110 can contact the corresponding pads 104 of the semiconductor chip 102 and be bonded thereto.

[0133] Furthermore, the bent strip element can be fully embedded by means of an encapsulation 106. After being bonded to the pad 104, an inner cavity of the strip elements is formed, which is enclosed by the end portions 1601, 1602, and the central section 1603. However, during encapsulation, the encapsulation 106 flows into the respective cavities to surround and thereby embed the respective strip elements. Thus, the risk of unwanted air pockets in the package can be reduced because the encapsulation step is performed after the strip elements have been mounted on the corresponding pads.

Claims

[1] A package (100) comprising: • an electronic chip (102) having at least one pad (104); • an encapsulation (106) which at least partially encapsulates the electronic chip (102); • an electrically conductive contact element (108) extending from the at least one pad (104); • wherein the electrically conductive contact element (108) comprises a first contact structure (110) made of a first electrically conductive material on the at least one pad (104), and a second contact structure (112) made of a second electrically conductive material and exposed with respect to the encapsulation (106), such that the electrically conductive contact element (108) extends through the encapsulation (106) to be exposed with respect to the encapsulation (106); • wherein the electrically conductive contact element (108) is a strip element, comprising the first contact structure (110) having a first layer of the first electrically conductive material, and the second contact structure (112) having a second layer of the second electrically conductive material. • wherein at least one of the at least one pad (104) has at least one surface portion comprising or consisting of the first electrically conductive material. [2] The package (100) according to claim 1, comprising a chip carrier (114) on which the electronic chip (102) is mounted. [3] The package (100) according to claim 2, wherein the chip carrier (114) has at least one surface portion which comprises or is made of a third electrically conductive material, wherein the third electrically conductive material in particular comprises or is made of the second electrically conductive material. [4] The package (100) according to claim 2 or 3, wherein the chip carrier (114) is connected to at least one further pad (122) of the electronic chip (102), wherein the at least one pad (104) is formed on a main surface (120) of the electronic chip (102) and the at least one further pad (122) is formed on an opposite, other main surface (124) of the electronic chip (102). [5] The package (100) according to any one of claims 2 to 4, comprising at least one electrically conductive projection (116) which projects from the chip carrier (114), in particular up to a vertical plane to which the contact element (108) extends. [6] The package (100) according to claim 5, wherein the at least one electrically conductive projection (116) comprises or is made of a fourth electrically conductive material, wherein the fourth electrically conductive material in particular comprises or is made of one of the second electrically conductive material and the third electrically conductive material. [7] The package (100) according to any one of claims 1 to 6, wherein the electrically conductive contact element (108) is a layer stack comprising, as the first contact structure (110), at least a first layer of the first electrically conductive material and, as the second contact structure (112), at least a second layer of the second electrically conductive material. [8] The package (100) according to any one of claims 1 to 7, comprising an electrically conductive connection structure (118) on a surface portion of the second contact structure (112), the surface portion being exposed with respect to the encapsulation (106). [9] The package (100) according to claim 8, wherein the electrically conductive connection structure (118) comprises at least one of the group consisting of a redistribution structure, in particular a redistribution layer, which is arranged at least partially on the encapsulation (106) and on the contact element (108), a clamp, a wire bond and a tape bond. [10] The package (100) according to one of claims 1 to 9, wherein the strip element has at least one third contact structure (111) between the first contact structure (110) and the second contact structure (112), wherein the at least one third contact structure (111) in particular has or consists of a material which has a higher thermal conductivity, a higher electrical conductivity and / or a lower modulus of elasticity than at least one of the first contact structure (110) and the second contact structure (112). [11] The package (100) according to claim 10, wherein the strip element is bent such that the strip element has a curved profile, in particular one of a U-shape, a V-shape, a Z-shape and a W-shape. [12] The package (100) of claim 11, wherein the strip element has a first end (1601), a second end (1602) and a central section (1603) disposed between the first end (1601) and the second end (1602), the first end (1601) and the second end (1603) being coupled to the pad (104) and the central section (108) being spaced from the pad (104). [13] A package (100) comprising: • an at least partially electrically conductive chip carrier (114); • an electronic chip (102) mounted on the chip carrier (114), the electronic chip (102) being provided with a pad (104) having an outer surface comprising a first metal; • an electrically conductive contact element (108) extending from the pad (104); • an encapsulation (106) which at least partially encapsulates the contact element (108) and the electronic chip (102); • wherein the contact element (108) comprises: ◯ a first contact structure (110) on the at least one pad (104) and ◯ a second contact structure (112) having an exposed surface not covered by the encapsulation (106), wherein the electrically conductive contact element (108) is a strip element, comprising the first contact structure (110) having a first layer of the first metal, and the second contact structure (112) having a second layer of the second metal. [14] The package (100) according to claim 13, wherein a thickness (d) of the first contact structure (110) is different from, in particular smaller than, a thickness (D) of the second contact structure (112). [15] The package (100) according to claim 13 or 14, wherein the electrically conductive contact element (108) has at least one third contact structure (111) between the first contact structure (110) and the second contact structure (112), wherein the at least one third contact structure (111) in particular has or consists of a material which has a higher thermal conductivity, a higher electrical conductivity and / or a lower modulus of elasticity than at least one of the first contact structure (110) and the second contact structure (112). [16] The package (100) according to any one of claims 13 to 15, wherein the electrically conductive contact element (108) is plate-shaped or strip-shaped. [17] A method of manufacturing a package (100), the method comprising: • at least partially encapsulating an electronic chip (102) having at least one pad (104) with an encapsulation (106); • Providing an electrically conductive contact element (108) extending from the at least one pad (104) and through the encapsulation (106) to be exposed with respect to the encapsulation (106); • Configuring the electrically conductive contact element (108) to have a first contact structure (110) made of a first electrically conductive material on the at least one pad (104), and a second contact structure (112) which is made of a second electrically conductive material and which is exposed with respect to the encapsulation (106), wherein the electrically conductive contact element (108) is a strip element comprising the first contact structure (110) having a first layer of the first electrically conductive material, and the second contact structure (112) having a second layer of the second electrically conductive material, wherein at least one of the at least one pad (104) has at least one surface portion comprising or consisting of the first electrically conductive material. [18] The method of claim 17, wherein the method comprises attaching the electrically conductive contact element (108) to the at least one pad (104) prior to encapsulation. [19] The method of claim 17 or 18, further comprising, prior to attaching the strip element to the at least one pad (104), cutting the strip element from an endless belt (1701) comprising the first layer and the second layer. [20] The method according to any one of claims 17 to 19, further comprising bending the strip element such that the profile of the strip element is curved, in particular a curved U-shape, a curved V-shape, a curved Z-shape and a curved W-shape, before attaching the strip element to the at least one pad (104). [21] The method according to any one of claims 17 to 20, comprising one of the following features: • wherein the method comprises exposing the electrically conductive contact element (108) by removing excess material of the encapsulation (106) after encapsulation; • wherein the method comprises exposing the contact element (108) by preventing encapsulation of an exposed portion of the contact element (108) during encapsulation. [22] The method according to any one of claims 17 to 21, wherein the method comprises mounting the electronic chip (102) on a chip carrier (114), and optionally providing an electrically conductive projection (116) on the chip carrier (114), in particular before at least partially encapsulating the projection (116) and the electronic chip (102). [23] The method according to any one of claims 17 to 22, wherein the method comprises exposing the second contact structure (112) with respect to the encapsulation (106) by means of at least one of the group consisting of: • covering at least a portion of the second contact structure (112) with a protective film during encapsulation and removing the protective film after encapsulation; • during encapsulation, making contact of at least a portion of the second contact structure (112) with a surface of an encapsulation tool to prevent the encapsulation (106) from covering the contacted portion; • Cleaning, in particular mechanical and / or chemical cleaning, of at least a portion of the second contact structure (112) after encapsulation, in order to thereby remove material of the encapsulation (106) from the portion. [24] The method according to any one of claims 17 to 23, wherein the method comprises refining an exposed surface of the second contact structure (112), in particular by means of cleaning, by means of activating and / or by means of forming a functional layer (132) on the second contact structure (112).

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