METHOD FOR PRODUCING A SEMICONDUCER MODULAR ARRANGEMENT

Abstract

A method for manufacturing a semiconductor module assembly comprises: arranging a casting tool vertically over a substrate of the semiconductor module assembly, wherein several pins and / or rivets are arranged on the substrate, each of the several pins and / or rivets having substantially the same height in a vertical direction perpendicular to the substrate; the casting tool having several cover elements, the several cover elements comprising a first subset of cover elements and a second subset of cover elements, each cover element of the first subset of cover elements being arranged vertically over another of the several pins and / or rivets, and the cover elements of the second subset of cover elements not being arranged vertically over a pin or rivet; and pressing each cover element of the first subset of cover elements onto the respective pin or rivet.and the pouring of a first material onto the substrate, thereby covering the substrate and enclosing each of the multiple pins and / or rivets, wherein the first material is prevented by the respective cover elements of the first subset of cover elements from covering a top surface of each of the multiple pins and / or rivets.

Description

TECHNICAL AREA The present disclosure relates to methods for manufacturing a semiconductor module assembly. BACKGROUND Document US 2020 / 0350236 A1 discloses a semiconductor device comprising a circuit unit with a semiconductor chip, several pin-shaped terminals extending in the same direction from the circuit unit and electrically connected to it, a sealing resin area sealing the circuit unit and first sections of the pin terminals arranged on one side of the circuit unit, and several cover resin areas extending integrally from the outer surface of the sealing resin area and from which second sections of the pin terminals project. The cover resin areas are cylindrically shaped and each covers the base ends of the second sections of the pin terminals arranged on one side of the sealing resin area. Semiconductor module assemblies often contain at least one substrate enclosed in a package. A semiconductor assembly with multiple controllable semiconductor devices (e.g., two IGBTs in a half-bridge configuration) is mounted on each of the at least one substrate. Each substrate typically has a substrate layer (e.g., a ceramic layer), a first metallization layer applied to one side of the substrate layer, and a second metallization layer applied to the other side of the substrate layer. The controllable semiconductor devices are mounted, for example, on the first metallization layer. A semiconductor module assembly generally has several terminals that are electrically connected at one end to the first metallization layer to establish an electrical connection between the interior and exterior of the package.Conventional semiconductor module assemblies often still contain a potting compound that can at least partially fill the interior of the package, thereby covering at least some of the components and electrical connections located on the substrate. The terminal elements may be partially embedded in the potting compound. However, at least their distal ends are not covered by the potting compound and protrude from it, allowing them to be electrically contacted. Different semiconductor module assemblies often have different layouts. This means that the various components, including the leads, are arranged in different positions on a substrate. When preparing the potting compound, it must be ensured that the ends of the leads are not covered by the compound. In some semiconductor module assemblies, leads are inserted into rivets attached to the substrate. In such cases, when preparing the potting compound, it must be ensured that the ends of the rivets facing away from the substrate are not covered by the compound, so that the leads can be easily inserted and sufficient electrical contact is established between the leads and the respective rivet.Since the layout can differ between various semiconductor modules, special casting tools may be required to fit the respective layout. This is complex and expensive. There is a need for a method for manufacturing a semiconductor module assembly that makes it possible to efficiently and cost-effectively produce semiconductor module assemblies with different layouts. OVERVIEW A method for manufacturing a semiconductor module assembly comprises arranging a die vertically over a substrate of the semiconductor module assembly, wherein several pins and / or rivets are arranged on the substrate, each of the several pins and / or rivets having substantially the same height in a vertical direction perpendicular to the substrate, the die comprising several cover elements, the several cover elements comprising a first subset of cover elements and a second subset of cover elements, each cover element of the first subset of cover elements being arranged vertically over another of the several pins and / or rivets, and the cover elements of the second subset of cover elements not being arranged vertically over a pin or rivet, pressing each cover element of the first subset of cover elements onto the respective pin or rivet.and the pouring of a first material onto the substrate, thereby covering the substrate and enclosing each of the multiple pins and / or rivets, wherein the first material is prevented by the respective cover elements of the first subset of cover elements from covering a top surface of each of the multiple pins and / or rivets. The invention can be better understood with reference to the following drawings and description. The components in the figures are not necessarily to scale; rather, the focus is on illustrating the principles of the invention. Furthermore, identical reference numerals in the figures denote corresponding parts in the different views. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a cross-sectional view of a power semiconductor module assembly. Fig. 2 is a three-dimensional view of a power semiconductor module assembly arranged in a housing. Figs. 3 and 4 schematically illustrate steps of a method for manufacturing a semiconductor module assembly according to embodiments of the disclosure. Fig. 5 is a three-dimensional view of a press tool used to carry out the method according to embodiments of the disclosure. DETAILED DESCRIPTION The following detailed description refers to the accompanying drawings. The drawings show specific examples of how the invention can be implemented. It is understood that the features and principles described in relation to the various examples can be combined with one another, unless expressly stated otherwise. In the description and in the claims, designations of certain elements as "first element," "second element," "third element," etc., are not to be understood as enumerative. Rather, such designations merely serve to name different "elements." That is to say, for example, that the presence of a "third element" does not require the presence of a "first element" and a "second element."An electrical conductor or electrical connection, as described here, can be a single electrically conductive element or at least two single electrically conductive elements connected in series and / or parallel. Electrical conductors and electrical connections can contain metal and / or semiconductor material and can be permanently electrically conductive (i.e., non-switchable). A semiconductor body, as described here, can be made of (doped) semiconductor material and can be a semiconductor chip or contained within a semiconductor chip. A semiconductor body has electrically connecting pads and contains at least one semiconductor element with electrodes. Referring to Fig. 1, a cross-sectional view of a semiconductor module assembly 100 is shown. The semiconductor module assembly 100 comprises a housing 7 and a substrate 10. The substrate 10 includes a dielectric insulating layer 11, a (structured) first metallization layer 111 attached to the dielectric insulating layer 11, and a (structured) second metallization layer 112 attached to the dielectric insulating layer 11. The dielectric insulating layer 11 is arranged between the first and second metallization layers 111 and 112. Each of the first and second metallization layers 111, 112 can consist of or contain one of the following materials: copper, a copper alloy; aluminum, an aluminum alloy; or any other metal or alloy that remains solid during operation of the power semiconductor module assembly. The substrate 10 can be a ceramic substrate, that is, a substrate in which the dielectric insulating layer 11 is a ceramic, e.g., a thin ceramic layer. The ceramic can consist of or contain one of the following materials: aluminum oxide; aluminum nitride; zirconium oxide; silicon nitride; boron nitride; or another dielectric ceramic. For example, the dielectric insulating layer 11 can consist of or contain one of the following materials: Al₂O₃, AlN, SiC, BeO, or Si₃N₄.The substrate 10 can be, for example, a direct copper bonding (DCB) substrate, a direct aluminum bonding (DAB) substrate, or an active metal brazing (AMB) substrate. Furthermore, the substrate 10 can be an insulated metal substrate (IMS). An insulated metal substrate generally has a dielectric insulating layer 11, which may consist of (filled) materials such as epoxy resin or polyimide. The material of the dielectric insulating layer 11 can, for example, be filled with ceramic particles. Such particles may consist of, for example, SiO₂, Al₂O₃, AlN, or BN and may have a diameter between approximately 1 µm and approximately 50 µm. The substrate 10 can also be a conventional printed circuit board (PCB) with a non-ceramic dielectric insulating layer 11.For example, a non-ceramic dielectric insulating layer 11 may consist of or contain a cross-linked resin. The substrate 10 is arranged in a housing 7. In the example shown in Fig. 1, the substrate 10 forms a bottom surface of the housing 7, while the housing 7 itself only has side walls and (optionally) a cover. However, this is only one example. It is also possible for the housing 7 to still have a bottom surface, with the substrate 10 arranged inside the housing 7 and on the bottom surface. According to another example, the substrate 10 can be mounted on a base plate (not shown). In some power semiconductor module assemblies 100, more than one substrate 10 is arranged on a single base plate. The base plate can, for example, form a bottom surface of the housing 7. One or more semiconductor bodies 20 can be arranged on the substrate 10. Each of the semiconductor bodies 20 arranged on the substrate 10 can contain a diode, an IGBT (insulated-gate bipolar transistor), a MOSFET (metal-oxide-semiconductor field-effect transistor), a JFET (junction field-effect transistor), a HEMT (high-electron-mobility transistor), or another suitable controllable semiconductor element. One or more semiconductor bodies 20 can form a semiconductor array on the substrate 10. In Fig. 1, only two semiconductor bodies 20 are shown by way of example. The second metallization layer 112 of the substrate 10 in Fig. 1 is a continuous layer. The first metallization layer 111 in the example shown in Fig. 1 is a structured layer. “Structured layer” means that the first metallization layer 111 is not a continuous layer, but contains recesses between different sections of the layer. Such recesses are shown schematically in Fig. 1. The first metallization layer 111 in this example contains three different sections. Different semiconductor bodies 20 can be mounted on the same or on different sections of the first metallization layer 111. Different sections of the first metallization layer may not have an electrical connection or may be connected using, for example, a cross-linking device.B. Bond wires 3 can be electrically connected to one or more other sections. Electrical connections 3 can also include, for example, connecting plates or busbars, to name just a few examples. The one or more semiconductor bodies 20 can be electrically and mechanically connected to the substrate 10 by an electrically conductive interconnect layer 30. Such an electrically conductive interconnect layer can be a solder layer, a layer of an electrically conductive adhesive, or a layer of a sintered metal powder, e.g., a sintered silver powder. The semiconductor module assembly 100 shown in Fig. 1 further includes terminal elements 4. The terminal elements 4 are electrically connected to the first metallization layer 111 and establish an electrical connection between the interior and exterior of the housing 7. The terminal elements 4 can be electrically connected to the first metallization layer 111 at a first end 41, while a second end 42 of the terminal elements 4 protrudes from the housing 7. The terminal elements 4 can be electrically contacted from the outside at their second ends 42. However, the terminal elements 4 shown in Fig. 1 are only examples. Terminal elements 4 can be implemented in any other way and can be arranged anywhere within the housing 7. For example, one or more terminal elements 4 can be arranged near or adjacent to the side walls of the housing 7. Any other suitable implementation is possible. In the semiconductor module arrangement 100 shown in Fig. 1, the first end 41 of each terminal element 4 is inserted into a rivet 44. A first end of each rivet 44 is attached to the substrate 10, i.e., to the first metallization layer 111. The rivets 44 can be electrically and mechanically connected to the substrate 10, for example, by an electrically conductive bonding layer (not specifically shown for the rivet 44 in Fig. 1). Such an electrically conductive bonding layer can be a solder layer, a layer of electrically conductive adhesive, or a layer of sintered metal powder, for example, sintered silver powder. A second end of the rivet 44 faces away from the substrate 10. The terminal elements 4 are inserted into the rivet 44 from their respective second ends.However, it is also generally possible for a connecting element 4 to be directly connected to the substrate 10 by means of an electrically conductive layer. This means that the rivets 44 can also be omitted. Conventional semiconductor module assemblies 100 generally include a potting compound 5. The potting compound 5 may, for example, be or contain a silicone gel, or it may be a rigid molding compound. The potting compound 5 may at least partially fill the interior of the housing 7, thereby covering the components and electrical connections arranged on the substrate 10. The rivets 44 may be embedded in the potting compound 5. However, at least their second ends facing away from the substrate 10 are not covered by the potting compound 5, so that they are freely accessible to the terminal elements 4. If terminal elements 4 are connected directly to the substrate 10 without rivets 44, the terminal elements 4 may be at least partially embedded in the potting compound 5. However, at least one surface of each terminal element 4 facing away from the substrate is not covered by the potting compound 5, so that it can be electrically contacted. The potting compound 5 is designed to protect the components and electrical connections within the semiconductor module 100, particularly within the housing 7, from certain environmental conditions and mechanical damage. The potting compound 5 also provides electrical insulation for the components within the housing 7. If the potting compound 5 is a rigid molding compound, the housing 7 can be omitted. The potting compound 5 can form a protective layer in a vertical direction y of the substrate 10. The vertical direction y is a direction substantially perpendicular to a top surface of the substrate 10. The top surface of the substrate 10 is a surface on which semiconductor bodies 20 are or can be mounted. The potting compound 5 at least partially covers all components arranged on the top surface of the substrate 10, as well as all exposed surfaces of the substrate 10. Fig. 2 schematically shows a semiconductor module with several terminal elements 4 (second ends 42 of terminal elements) protruding from the cover of a housing 7. In this example, the cover has several openings 722. Terminal elements 4 protrude from some, but not all, of the openings 722. By providing several openings 722 in the cover, one and the same housing 7 can be used for many different layouts or applications without the need to adapt the housing 7 for specific applications or customers. The potting compound 5 is typically formed by filling a first material into the housing 7 and subsequently crosslinking it. When filling the first material into the housing 7, it must be ensured that at least one top surface of the connecting elements 4 and / or one top surface of the rivets 44, which are arranged on the substrate 10, remains free of the first material. In particular, when using rivets 44, as shown in Fig. 1, it must be ensured that the first material does not flow into the rivets 44. In this way, the second ends of the rivets 44 remain open and freely accessible to the connecting elements 4. Furthermore, sufficient electrical contact between the rivets 44 and the respective connecting elements 4, which is not interrupted by the first material, is ensured.If connecting elements 4 are attached directly to the substrate 10, at least their second ends 42 should remain free of the first material so that they can be electrically contacted. When filling the initial material into the housing 7, suitable tools can be used that cover at least one surface of the rivet 44 and / or the terminal elements 4 facing away from the substrate 10. However, as mentioned above, many different layouts are possible for different semiconductor module arrangements. That is, the rivet 44 and / or terminal elements 4 can be arranged in different positions on the substrate 10 in different semiconductor module arrangements. Consequently, it may be necessary to use custom tools to accommodate each individual layout. This is cumbersome and costly. Connection elements 4 are frequently implemented as simple pins. Therefore, connection elements 4 are also referred to as pins 4 in the following. A semiconductor module assembly can only have connection elements 4 that are directly coupled to the substrate 10 by means of electrically conductive interconnect layers. Alternatively, a semiconductor substrate assembly can only have connection elements 4 that are connected to the substrate 10 by means of rivets 44, as schematically shown in the figures. However, it is also possible that some connection elements 4 are directly coupled to the substrate 10 by means of electrically conductive layers, while other connection elements 4 are connected to the substrate 10 by means of rivets 44. A method for manufacturing a semiconductor module assembly according to embodiments of the disclosure comprises arranging a casting tool 82 vertically above a substrate 10 of the semiconductor module assembly, wherein several pins 4 and / or rivets 44 are arranged on the substrate 10, each of the several pins 4 and / or rivets 44 having substantially the same height in a vertical direction y perpendicular to the substrate 10, the casting tool 82 having several cover elements 84, the several cover elements 84 comprising a first subset of cover elements 84 and a second subset of cover elements 84, each cover element 84 of the first subset of cover elements 84 being arranged vertically above another of the several pins 4 and / or rivets 44, and the cover elements 84 of the second subset of cover elements 84 not being arranged vertically above a pin 4 or a rivet 44. This is shown schematically in Fig. 3. Now referring to Fig. 4, the method further comprises the following steps: pressing each cover element 84 of the first subset of cover elements 84 onto the respective pin 4 or rivet 44 and pouring a first material onto the substrate 10, thereby covering the substrate 10 and enclosing each of the several pins 4 and / or rivets 44, the first material being prevented by means of the respective cover elements 84 of the first subset of cover elements 84 from covering a top surface of each of the several pins 4 and / or rivets 44. As schematically illustrated in Figures 3 and 4, and in the three-dimensional view of a casting tool 82 in Figure 5, the number of cover elements 84 contained within the multiple cover elements 84 is greater than the number of pins 4 and / or rivets 44 on the substrate 10. The cover elements 84 can be arranged in a regular pattern on a side of the casting tool 82 that faces the substrate 10 when the casting tool 82 is positioned over the substrate 10. For example, the cover elements 84 can be arranged in rows and columns. A cross-sectional area of ​​a surface of the casting tool 82 facing the substrate 10 can, for example, be substantially equal to a cross-sectional area of ​​the substrate 10. However, it is also possible, for example, that a cross-sectional area of ​​a surface of the casting tool 82 facing the substrate 10 is larger than a cross-sectional area of ​​the substrate 10.According to some examples, the casting tool 82 can have essentially the same shape and size as the substrate 10. The cover elements 84 can be evenly distributed over the surface of the casting tool 82 facing the substrate 10. In this way, the casting tool 82 can be used for many different semiconductor module layouts. Regardless of where the pins 4 and / or rivets 44 are located on the substrate 10, one of the cover elements 84 is always positioned over each of the pins 4 and / or rivets 44. This eliminates the need for custom casting tools that can only be used for very specific layouts. According to some embodiments, pressing each cover element 84 of the first subset of cover elements 84 onto the respective pin 4 or rivet 44 involves moving the casting tool 82 together with several cover elements 84 towards the substrate 10. The cover elements 84 can, for example, be connected to the casting tool 82 by means of a spring connection. When the casting tool 82 is moved towards the substrate 10, the cover elements 84 of the first subset contact the pins 4 or rivets 44. As the casting tool 82 continues to move towards the substrate 10, the cover elements 84 of the first subset yield to a certain degree due to the spring connection. In this way, they can be pressed firmly onto the respective pins 4 and / or rivets 44 without damaging the pins 4 and / or rivets 44. Alternatively, pressing each cover element 84 of the first subset of cover elements 84 onto the respective pin 4 or rivet 44 involves the individual movement of the cover elements 84 of the first subset towards the substrate 10. That is, the cover elements 84 can be movable relative to the casting tool 82. For example, each cover element 84 can be individually movable relative to the casting tool 82 by means of a movement mechanism. The casting tool 82 can initially be moved towards the substrate 10 until the cover elements 84 of the first subset contact the respective pins 4 or rivets 44. The casting tool 82 can then remain in this position. However, the cover elements 84 of the first subset can be moved further towards the substrate 10, e.g., by means of the movement mechanism.In this alternative procedure, the cover elements 84 of the first subset can also be pressed firmly onto the respective pins 4 and / or rivets 44 without damaging the pins 4 and / or rivets 44. After the first material has been poured onto the substrate 10, a crosslinking step can follow, forming a casting compound. The casting tool 82 can be removed after the first material has been poured onto the substrate 10. The casting tool 82 can be removed before or after the first material has been crosslinked. If the casting tool 82 remains in position during a crosslinking step with the cover elements 84 of the first batch pressed firmly against the pins 4 and / or rivets 44, it can be ensured that the first material does not reach the top surface of the pins 4 and / or rivets 44 facing away from the substrate 10 while the first material is still liquid or viscous. Before the casting tool 82 is positioned vertically above the substrate 10, the substrate 10 can be arranged in a housing 7 or in a mold 80. Many semiconductor module assemblies are arranged in housings 7, as shown by way of example in Figs. 1 and 2. In such assemblies, the housing 7 itself can be filled with the first material. That is, after the first material has been poured into the housing 7 and after it has been crosslinked (optionally), the substrate 10 can remain in the housing 7. In such cases, no separate mold is required. However, if the casting compound 5 is a rigid molding compound after the first material has cured and can adequately protect the substrate 10 from mechanical damage, a housing 7 may not be necessary. In such cases, the substrate 10 can be arranged in a mold 80 (see, for example, Figs. 3 and 4). The first material can be poured into the mold 80, with the substrate 10 positioned within it. The mold 80 prevents the first material from flowing off the substrate 10 until it cures. Once the first material has cured, the substrate 10, with the casting compound 5 formed on it, can be removed from the mold 80 (not shown specifically). The casting of the first material onto the substrate 10 can involve the formation of a layer of the first material on the substrate 10, wherein the height of the layer of the first material in the vertical direction y is essentially equal to the height of the multiple pins 4 and / or rivets 44 in the vertical direction y, as exemplified in Figs. 3 and 4. In this way, the pins 4 and / or rivets remain easily accessible for electrical contact.

Claims

A method for manufacturing a semiconductor module assembly, comprising: arranging a casting tool (82) vertically over a substrate (10) of the semiconductor module assembly, wherein several pins (4) and / or rivets (44) are arranged on the substrate (10), each of the several pins (4) and / or rivets (44) having substantially the same height in a vertical direction (y) perpendicular to the substrate (10), the casting tool (82) having several cover elements (84), the several cover elements (84) comprising a first subset of cover elements (84) and a second subset of cover elements (84), each cover element (84) of the first subset of cover elements (84) being arranged vertically over another of the several pins (4) and / or rivets (44), and the cover elements (84) of the second subset of cover elements (84) not being arranged vertically over a pin (4) or rivet (44);Pressing each cover element (84) of the first subset of cover elements (84) onto the respective pin (4) or rivet (44), and pouring a first material onto the substrate (10), thereby covering the substrate (10) and enclosing each of the multiple pins (4) and / or rivets (44), the first material being prevented by the respective cover elements (84) of the first subset of cover elements (84) from covering a top surface of each of the multiple pins (4) and / or rivets (44). Method according to claim 1, wherein pressing each cover element (84) of the first subset of cover elements (84) onto the respective pin (4) or rivet (44) comprises moving the casting tool (82) together with several cover elements (84) in the direction of the substrate (10). Method according to claim 1, wherein pressing each cover element (84) of the first subset of cover elements (84) onto the respective pin (4) or rivet (44) comprises the individual movement of the cover elements (84) of the first subset in the direction of the substrate (10). Method according to any one of claims 1 to 3, further comprising the crosslinking of the first material. Method according to one of the preceding claims, further comprising the removal of the casting tool (82) after casting the first material onto the substrate (10). A method according to one of the preceding claims, further comprising arranging the substrate (10) in a housing (7) or in a mold (80) before arranging the casting tool (82) vertically above a substrate (10). Method according to one of the preceding claims, wherein the casting of the first material onto the substrate (10) comprises the formation of a layer of the first material on the substrate (10), wherein the height of the layer of the first material in the vertical direction (y) is substantially equal to the height of the multiple pins (4) and / or rivets (44) in the vertical direction (y).

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