WO2024110052A1

WO2024110052A1 - Molded power module

Info

Publication number: WO2024110052A1
Application number: PCT/EP2022/083294
Authority: WO
Inventors: Andreas Munding; Frank Winter; Andreas SITTINGER; Stefan RAATZ; Holger Torwesten
Original assignee: Huawei Digital Power Technologies Co., Ltd.
Priority date: 2022-11-25
Filing date: 2022-11-25
Publication date: 2024-05-30

Abstract

A molded power module (100) comprises a thermally conductive and electrically isolating substrate (120) and at least one power semiconductor die (110) having a top surface (110a) and a bottom surface (110b) opposing the top surface (110a). The bottom surface (110b) is attached to the substrate (120). The power semiconductor die (110) comprises one or more terminal pads (111, 112, 113) formed on the top surface (110a) for electrically connecting the power semiconductor die. The module (100) comprises a mold compound (140) at least partially encapsulating the at least one power semiconductor die. The mold compound has an upper main face (140a) and a lower main face (140b) opposing the upper main face (140a). The upper main face (140a) faces the top surface (110a) of the power semiconductor die (110). One or more contact holes (150a, 150c) are penetrating the mold compound (140) from the upper main face (140a) to a respective terminal pad (111) on the top surface (110a) of the power semiconductor die (110). Each contact hole (150a, 150c) is formed with an undercut profile (151). The undercut profile enables unidirectional insertion of a contact element (130a, 130c) into the contact hole for electrically contacting the respective terminal pad (111).

Description

Molded Power Module

TECHNICAL FIELD

The disclosure relates to the field of panel level packaging technology for molded high-power modules. In particular, the disclosure relates to a molded power module with at least one semiconductor die.

BACKGROUND

Scaling of production formats increases productivity and improves economic benefits. In analogy to front-end device technology this trend can also be observed in package technology. Panel level packaging technologies such as laminate chip embedding/embedded component packaging (CE/ECP) and fan-out panel level packaging (FO-PLP) are currently replacing conventional strip-molded small footprint QFP or BGA packages in logic or ICT (information and communication technology) applications such as mobile communication chip sets or automotive radar chipsets. Panel level packaging is also attractive for power modules because of the potential economic benefit over standard sequential module packaging concepts. For industrializing panel manufacturing of molded high-power modules, flexible and scalable power terminal structures that can be integrated into a panel level packaging process are required, but not yet available.

SUMMARY

This disclosure provides a solution for a molded power module with flexible and scalable power terminal structures that can be manufactured by a panel level packaging process.

The foregoing and other objects and other objectives are achieved by the features of the independent claims. Further implementation forms are apparent from the dependent claims, the description and the figures.

This disclosure presents a solution how to make power terminals for high power modules that can be produced on panel level. It allows to produce many contacts at a time by parallel processing or batch processing. Accordingly, productivity is increased by increasing throughput, production format from single module to panel format, and by sharing tool costs across different products. It can be applied to single side cooled modules with power terminals in the form of pins on the upper surface and various other power modules. The pin layout is fully customizable. Embodiments described in this disclosure may comprise the following:

A single side cooled molded power module with a mold body that has open contact holes from the outer surface to the metallization of the substrate or the die.

A chip contact for molded power modules including blind hole with lock-in features.

The contact holes may have an undercut profile created by sacrificial material which retains its shape during molding and can be removed completely after molding.

The blind hole with undercut profile may belong to a lock-in function (cannot be produced by prior art drilling/lasering/molding) that allows unidirectional insertion of a power pin into the contact hole and holding it in place to fulfil its functions during the lifetime of the product.

Contact elements that consists of 3 sections: a) External section protruding from the upper surface; b) Middle section with lock-in features in x/y dimension; and c) Contact section with elasticity and compliance in z dimension to maintain and constrain the contact force onto the pad of the die/substrate during the lifetime of the product.

There can be different types of contact elements for different current carrying capabilities.

The lock-in function can be realized in different ways.

The insertion can be done during production in different ways.

In case of direct contact to the chip surface, a metallization reinforcement on the chip pad can be necessary in order to protect the chip from damage and contamination.

Embodiments described in this disclosure can be applied in power modules with a single sided cooling interface and a power range in the several tens of kW area. It can also be used in applications where the power terminals and signal terminals are on the upper main surface and are connected directly to a power PCB or busbar. Exemplary applications are power modules for PV (photovoltaic) inverters, data center power conversion, and industrial grade application of power modules.

In order to describe the disclosure in detail, the following terms, abbreviations and notations will be used:

FOWLP,

FO-WLP Fan-out wafer level packaging

FOPLP,

FO-PLP Fan-out panel level packaging

RDL Redistribution layer

PCB Printed Circuit Board SSC Single sided cooling

DSC Double (or dual) sided cooling

CE Chip Embedding

ECP Embedded Component Package or Packaging

QFP Quad flat pack

BGA Ball grid array

ICT Information & communication technology

Panel level packaging, Fan-out panel level packaging in this disclosure refers to the generalized concept of using RDL metallization equipment from PCB industry to increase the production format of fan-out wafer level packages (FO-WLP) up to the PCB panel format of 24” x 18” (600 mm x 450 mm) with the goal to achieve economic benefit for high volume production. Equivalent to FO-WLP, the “fan-out” of FO-PLP means that the package can be larger than the die, and the RDL for the board mounting interface extends beyond the projected area of the chip. It also means that multiple chips can be in one package, and that the chips have to be rearranged or reconstituted in a key process step.

Laminate chip embedding, embedded component packaging in this disclosure refers to the practice of embedding chips in PCB type core and prepreg laminate sheet material and using PCB type processes to realize RDL metallization. While panel level packaging more generally includes the use of moldable materials, chip embedding or laminate chip embedding usually excludes materials that are not supplied as sheets and cannot be processed in a PCB lamination press.

Strip molding in this disclosure refers to molding using the manufacturing format of typical leadframes. Typical sizes range from 70/90 mm x 270/300 mm.

Panel molding in this disclosure refers to the use of panel production format for molding. This excludes transfer molding equipment for lack of large area equipment (exorbitant closing forces). Usually panel molding refers to compression molding with liquid mold compounds and respective equipment, or to the use of mold sheets in combination with a lamination press. It usually also excludes package material which has a glass fiber matrix. The mold compounds are usually filled with glass or ceramic type of particles.

Power terminals in this disclosure mean pin, bolt or nut type metallic features of power modules that are mechanically stable, that can support currents beyond 100 A and that provide isolation/clearance for voltages beyond 100 V. Chip embedding or embedded component packaging (CE/ECP) in this disclosure means packaging technology where bare dies typically with Cu metallization are embedded inside PCB material and connected to the Cu routing on the package with plated vias.

According to a first aspect, the disclosure relates to a molded power module, comprising: a thermally conductive and electrically isolating substrate; at least one power semiconductor die having a top surface and a bottom surface opposing the top surface, wherein the bottom surface is attached to the substrate, the at least one power semiconductor die comprising one or more terminal pads formed on the top surface for electrically connecting the at least one power semiconductor die; a mold compound at least partially encapsulating the at least one power semiconductor die, the mold compound having an upper main face and a lower main face opposing the upper main face, wherein the upper main face faces the top surface of the at least one power semiconductor die; and one or more contact holes penetrating the mold compound from the upper main face of the mold compound to a respective terminal pad on the top surface of the at least one power semiconductor die; wherein each contact hole is formed with an undercut profile, the undercut profile enabling unidirectional insertion of a contact element into the contact hole for electrically contacting the respective terminal pad.

Such molded power module provides flexible and scalable power terminal structures that can be easily manufactured by a panel level packaging process. The one or more contact holes can be produced at a time by parallel processing or batch processing. Applying this molded power module increases productivity by increasing throughput, increasing the production format from single module to panel format, and by sharing tool costs across different products. The molded power module can be used as a single side cooled module with power terminals in the form of pins on the upper surface. The pin layout of this molded power module is fully customizable.

An undercut profile as described in this disclosure is a profile formed by cutting away material from the underside of an object so as to leave an overhanging portion in relief.

An undercut or undercut profile of the contact hole is any indentation or protrusion in the contact hole that will prevent withdrawal of the contact element from the contact hole when moved into the contact hole. For example, the undercut (or undercut profile) has the purpose to lock the contact element into the contact hole. This is also referred to as the undercut function. In an exemplary implementation of the molded power module, the undercut profile enables beside unidirectional insertion of the contact element also locking of the contact element in the contact hole. Locking means that the contact element is fixed in the contact hole and cannot be released from the contact hole without destroying either the contact element or the contact hole. For example, locking means that the contact element becomes fixed in its inserted position in the contact hole. Thus, the molded power module ensures that the contact element is fixed in the contact hole.

In an exemplary implementation of the molded power module, the substrate comprises an upper metallization layer, a lower metallization layer opposing the upper metallization layer and an insulating layer between the upper metallization layer and the lower metallization layer, wherein the bottom surface of the at least one power semiconductor die is attached to the upper metallization layer; wherein the substrate comprises one or more substrate pads formed on the upper metallization layer for electrically connecting the upper metallization layer; wherein the molded power module comprises: one or more further contact holes penetrating the mold compound from the upper main face of the mold compound to a respective substrate pad on the upper metallization layer of the substrate; wherein each further contact hole is formed with an undercut profile, the undercut profile enabling unidirectional insertion of a contact element into the further contact hole for electrically contacting the respective substrate pad.

This provides the advantage that multiple contact holes can be formed which can be either contacted to a terminal pad of the power semiconductor die or directly with a substrate pad on the substrate, e.g., at a trace on the substrate beneath the power semiconductor die. Thus, the molded power module can be flexible designed, e.g. by location where the contact hole can be formed, geometrical shape of the contact hole and type of the contact hole.

In an exemplary implementation of the molded power module, each contact hole comprises a first axial section having a first width and an adjoining second axial section having a second width that is larger than the first width; wherein the first axial section is formed at the upper main face of the mold compound. Thus, larger width of the second axial section provides the locking feature by which the contact element can be locked in the contact hole.

The different axial sections of the contact hole are not limited to round axial geometries. They can also have any other axial geometry or combination of different axial geometries, such as for example, square, rectangular, ellipsoid, regular polygonic or other any-shape symmetric axial sections. For a round axial geometry the widths of the sections may refer to the respective diameters of the axial sections.

In an exemplary implementation of the molded power module, a first contact hole of the contact holes is configured to receive a signal pin; and a second contact hole of the contact holes is configured to receive a power pin; wherein the first width of the first axial section of the second contact hole is larger than the first width of the first axial section of the first contact hole; and/or the second width of the second axial section of the second contact hole is larger than the second width of the second axial section of the first contact hole. Therefore different kind of pins can be efficiently contacted. For a power pin large currents will flow, therefore, a large width is provided for this power pin. For a signal pin, only small currents will flow, therefore, a small width is sufficient for this signal pin.

In an exemplary implementation of the molded power module, the undercut profile of the contact hole comprises one of the following: a step or multi-step sidewall profile; an inwards slanted sidewall profile; a concave or convex sidewall profile; a hyperboloid sidewall profile. Accordingly, flexible design options are possible.

In an exemplary implementation of the molded power module, the molded power module comprises: one or more contact elements electrically contacting the respective terminal pad, the one or more contact elements being attached to the respective terminal pad via the contact hole above the respective terminal pad. Thus, flexible and scalable power terminal structures can be provided. The contact holes can be attached to the respective terminal pads during panel level packaging process or after production of the molded power module.

In an exemplary implementation of the molded power module, each contact element comprises: an external section protruding from the upper main face of the mold compound; a contact section contacting the respective terminal pad; and a middle section between the external section and the contact section, the middle section formed to lock the contact element in the contact hole above the respective terminal pad.

The contact section of a respective contact element may be shaped to provide compliance to limit mechanical force, thereby protecting the metal pad (terminal pad) and sustaining sufficient clamping force during the entire module operation life. The molded power module provides efficient electrical and mechanical contact properties. In an exemplary implementation of the molded power module, each contact element comprises one or more spring elements that engage with an undercut of the contact hole to clamp the contact element in the contact hole above the respective terminal pad.

This provides efficient clamping of the contact element in the contact hole.

In an exemplary implementation of the molded power module, each contact element comprises one or more fixation elements that engage with the upper main face of the mold compound to clamp the contact element against the upper main face of the mold compound. This provides the efficient clamping of the contact element against the mold compound.

In an exemplary implementation of the molded power module, the one or more contact elements are made of metal. Specifically, metals with high electrical and thermal conductivity should be used, like e.g., Cu, Ni, Cu:Fe, Ni:Fe, Cu:Be. Elastic properties of the metals can be enhanced by alloys or additives to the metal composition, or by specific heat treatment. Contact elements can be made from sheet metal by means of stamping, coining, bending, forging, etc. Contact elements can have a surface finish to enhance electrical contact resistance and to avoid oxidation of the surface.

This provides excellent electrical conductivity and mechanical stability.

In an exemplary implementation of the molded power module, the one or more contact elements attached to the respective terminal pad are plastically deformed compared to their original shape; wherein a locking of the contact element results from the plastic deformation. This provides excellent locking of the contact element in the contact hole due to the plastic deformation. In other words, the contact is deformed during insertion by means of constriction and deflection of the thin contact material to clamp the contact element in the contact hole irreversibly forming a bow or sleeve.

In an exemplary implementation of the molded power module, the one or more contact elements attached to the respective terminal pad are buckled compared to their original shape; wherein a locking of the contact element results from the buckling of the contact element. This provides excellent locking of the contact element in the contact hole due to the buckling of the contact element. Buckling may be triggered during insertion or during the last few microns of insertion length by constriction/touching the bottom of the contact hole. The lock-in function results from the buckling action.

In an exemplary implementation of the molded power module, the one or more contact holes are at least partially filled by a metal layer. This means that the sidewalls of the contact hole and the semiconductor metal pad or substrate pad can be metallized. This provides excellent electrical conductivity of the contact between the contact hole and the contact element.

In an exemplary implementation of the molded power module, the one or more contact elements comprise connection elements which are configured to connect the one or more contact elements with respect to each other before insertion into the one or more contact holes, wherein the connection elements are configured to be separated after insertion into the one or more contact holes. This provides mechanical stability of the contact elements by using these connection elements.

The connection elements may be connected to each other according to a predefined raster. The raster may be any regular or repetitive pattern but is not limited to such pattern. It can also be any kind of regular or irregular connection, e.g., via tie bars or other elements. A raster configuration can be helpful to minimize tooling cost as attempt to re-use a pressing tool-plate. Such connection of elements facilitates mass production. The connected elements (by e.g. tie bars) can be separated again by a cutting tool after insertion.

In an exemplary implementation of the molded power module, the one or more contact elements comprise a galvanically deposited metal layer, the galvanically deposited metal layer being formed after insertion of the contact elements for increasing an electrical contact area with the respective terminal pad in order to reduce an electrical and/or thermal resistance and to protect the contact area by metallic sealing. Here, the galvanically deposited metal layer means an additional post insertion deposited metal layer. Such post insertion metallization is intended to increase the area of electrical contact by closing gaps. This provides an increased electrical contact area with the respective terminal pad enabling a reduced electrical and/or thermal resistance and protection of the contact area by metallic sealing.

In an exemplary implementation of the molded power module, the molded power module comprises a single side cooled, SSC, power module. This provides an SSC power module can be efficiently provided by panel level packaging.

BRIEF DESCRIPTION OF THE DRAWINGS

Further embodiments of the disclosure will be described with respect to the following figures, in which:

Figure 1 shows a schematic cross section of a molded power module 100 according to the disclosure; Figure 2 shows a schematic cross section of the molded power module 100 shown in figure 1 , without contact elements inserted in the contact holes;

Figures 3a and 3b show different schematic cross sections of a molded power module 100 illustrating a lock-in feature for a power pin 301 , a signal pin 302 and an alternative signal pin 303 by barbed spring metal contact element during insertion (Figure 3a) and after insertion (Figure 3b);

Figures 4a and 4b show different schematic cross sections of a molded power module 100 illustrating a lock-in feature for a power pin 401 and a signal pin 402 by plastic deformation of the metal contact element, e.g. the pin during insertion (Figure 4a) and after insertion (Figure 4b) for different shaped contact holes 410a/b, 411a/b;

Figure 5a shows a schematic cross section of a molded power module 100 illustrating the lock- in feature by plastic deformation for a different shaped power pin 501 after insertion; and Figure 5b shows a top view of an example of the structured metal sheet 510 for insertion of the signal pins and power pins.

DETAILED DESCRIPTION OF EMBODIMENTS

In the following detailed description, reference is made to the accompanying drawings, which form a part thereof, and in which is shown by way of illustration specific aspects in which the disclosure may be practiced. It is understood that other aspects may be utilized and structural or logical changes may be made without departing from the scope of the disclosure. The following detailed description, therefore, is not to be taken in a limiting sense, and the scope of the disclosure is defined by the appended claims.

It is understood that comments made in connection with a described method may also hold true for a corresponding device or system configured to perform the method and vice versa. For example, if a specific method step is described, a corresponding device may include a unit to perform the described method step, even if such unit is not explicitly described or illustrated in the figures. Further, it is understood that the features of the various exemplary aspects described herein may be combined with each other, unless specifically noted otherwise.

Figure 1 shows a schematic cross section of a molded power module 100 according to the disclosure. The upper pictures 100a and 100b represent zoom views of the contact areas for a first type contact element 100a, e.g., a signal pin and for a second type contact element 100b, e.g., a power pin. The molded power module 100 comprises a thermally conductive and electrically isolating substrate 120; at least one power semiconductor die 110; a mold compound 140; and one or more contact holes 150a, 150c.

The at least one power semiconductor die 110 has a top surface 110a and a bottom surface 110b opposing the top surface 110a. The bottom surface 110b is attached to the substrate 120. The at least one power semiconductor die 110 comprises one or more terminal pads 111 , 112, 113 formed on the top surface 110a for electrically connecting the at least one power semiconductor die 110.

The mold compound 140 is at least partially encapsulating the at least one power semiconductor die. The mold compound 140 has an upper main face 140a and a lower main face 140b opposing the upper main face 140a. The upper main face 140a faces the top surface 110a of the at least one power semiconductor die 110 as shown in Figure 1.

The one or more contact holes 150a, 150c are penetrating the mold compound 140 from the upper main face 140a of the mold compound 140 to a respective terminal pad 111 on the top surface 110a of the at least one power semiconductor die 110.

Each contact hole 150a, 150c is formed with an undercut profile 151. The undercut profile 151 enables unidirectional insertion of a contact element 130a, 130c into the contact hole 150a, 150c for electrically contacting the respective terminal pad 111.

The undercut profile 151 is formed by cutting away material from the underside of an object, here an interior chamber of the mold compound 140, so as to leave an overhanging portion in relief, as can be seen in Figure 1 , in particular in the zoom views 100a and 100b.

As can be seen from Figure 1 , the undercut profile 151 of the contact holes 150a, 150c is an indentation or protrusion in the contact hole 150a, 150c that prevents withdrawal of the contact element 130a, 130c from the contact hole 150a, 150c when moved into the contact hole 150a, 150c. The undercut profile 151 has the purpose to lock the contact element 130a, 130c into the contact hole 150a, 150c. This is also referred to as the undercut function.

The undercut profile 151 enables beside unidirectional insertion of the contact element 130a, 130c also locking of the contact element 130a, 130c in the respective contact hole 150a, 150c. Locking means here that the contact element 130a, 130c is fixed in the contact hole 150a, 150c and cannot be released from the contact hole 150a, 150c without destroying either the contact element 130a, 130c or the contact hole 150a, 150c. Locking means that the contact element 130a, 130c becomes fixed in its inserted position in the contact hole 150a, 150c.

The substrate 120 comprises an upper metallization layer 121 , a lower metallization layer 123 opposing the upper metallization layer 121 and an insulating layer 122 between the upper metallization layer 121 and the lower metallization layer 123. It understands that further metallization and/or insulating layers may be included in the substrate. The bottom surface 110b of the at least one power semiconductor die 110 is attached to the upper metallization layer 121.

The substrate 120 may comprise one or more substrate pads 124, 125 formed on the upper metallization layer 121 for electrically connecting the upper metallization layer 121. The one or more substrate pads 124 may be formed to electrically connect a signal pin. The one or more substrate pads 125 may be formed to electrically connect a power pin. A size of the substrate pins 125 may be larger than a size of the substrate pins 124.

The molded power module 100 may comprise one or more further contact holes 150b, 150d penetrating the mold compound 140 from the upper main face 140a of the mold compound 140 to a respective substrate pad 124, 125 on the upper metallization layer 121 of the substrate 120. The one or more further contact holes 150b may be designed for receiving a respective contact element 130b of a signal pin. The one or more further contact holes 150d may be designed for receiving a respective contact element 130d of a power pin.

Each further contact hole 150b, 150d may be formed with an undercut profile 151 which enables unidirectional insertion of a respective contact element 130b, 130d into the further contact hole 150b, 150d for electrically contacting the respective substrate pad 124, 125.

Each contact hole 150a, 150c, 150b, 150d may comprise a first axial section 153 having a first width and an adjoining second axial section 154 having a second width that is larger than the first width, e.g., as shown in the zoom view 100a. The first axial section 153 can be formed at the upper main face 140a of the mold compound 140.

As already mentioned above, the different axial sections of the contact holes 150a, 150b, 150c, 150d are not limited to round axial geometries. They can also have any other axial geometry or combination of different axial geometries, such as for example, square, rectangular, ellipsoid, regular polygonic or other any-shape symmetric axial sections.

For a round axial geometry the widths of the sections may refer to the respective diameters of the axial sections.

As can be seen from Figure 1 , a first contact hole 150a may be configured to receive a signal pin; and a second contact hole 150c may be configured to receive a power pin.

The first width of the first axial section 153 of the second contact hole 150c can be larger than the first width of the first axial section 153 of the first contact hole 150a.

The second width of the second axial section 154 of the second contact hole 150c can be larger than the second width of the second axial section 154 of the first contact hole 150a.

The undercut profile 151 may be implemented based on different shapes. For example, the undercut profile 151 of the contact hole 150a, 150c may comprise a step or multi-step sidewall profile; an inwards slanted sidewall profile; a concave or convex sidewall profile; a hyperboloid sidewall profile or many other profile types.

One or more contact elements 130a, 130c for electrically contacting the respective terminal pad 111 may be attached to the respective terminal pad 111 via the contact hole 150a, 150c above the respective terminal pad 111.

In Figure 1 , the molded power module 100 is shown with the contact elements 130a, 130b, 130c inserted in the contact holes 150a, 150b, 150c. However, the molded power module 100 can also be provided without the contact elements 130a, 130b, 130c inserted in the contact holes 150a, 150b, 150c as shown in Figure 2.

Each contact element 130a, 130c may comprise: an external section 131 protruding from the upper main face 140a of the mold compound 140, as can be seen in Figure 1 ; a contact section 133 contacting the respective terminal pad 111 ; and a middle section 132 between the external section 131 and the contact section 133. The middle section 132 is formed to lock the contact element 130a, 130c in the contact hole 150a, 150c above the respective terminal pad 111.

As already mentioned above, the contact section of a respective contact element 130a, 130b, 130c, 130d may be shaped to provide compliance to limit mechanical force, thereby protecting the metal pad (terminal pad) and sustaining sufficient clamping force during the entire module operation life.

Each contact element 130a, 130c may comprise one or more spring elements 134, e.g., as shown in the zoom view 100b, that engage with an undercut of the contact hole 150a, 150c to clamp the contact element 130a, 130c in the contact hole 150a, 150c above the respective terminal pad 111.

Each contact element 130a, 130c may comprise one or more fixation elements 135, e.g., as shown in the zoom view 100b, that engage with the upper main face 140a of the mold compound 140 to clamp the contact element 130a, 130c against the upper main face 140a of the mold compound 140.

The one or more contact elements 130a, 130c may be made of metal.

The one or more contact elements 130a, 130c attached to the respective terminal pad 111 can be plastically deformed compared to their original shape, e.g., as described below with respect to Figures 4 and 5. A locking of the contact element 130a, 130c may result from the plastic deformation. In other words, the contact is deformed during insertion by means of constriction and deflection of the thin contact material to clamp the contact element in the contact hole.

The one or more contact elements 130a, 130c attached to the respective terminal pad 111 may be buckled compared to their original shape, e.g., as described below with respect to Figures 4 and 5. A locking of the contact element 130a, 130c may result from the buckling of the contact element. Buckling may be triggered during insertion or during the last few microns of insertion length by constriction/touching the bottom of the contact hole. The lock-in function results from the buckling action.

The contact holes 150a, 150c can be at least partially filled by a metal layer. This means that the sidewalls of the contact hole and the semiconductor metal pad or substrate pad can be metallized. This improves the contact between the contact holes 150a, 150c and the respective contact element 130a, 130c.

The one or more contact elements 130a, 130c may comprise connection elements, e.g., connection elements 510 as shown in Figure 5, which are configured to connect the one or more contact elements 130a, 130c with respect to each other before insertion into the one or more contact holes 150a, 150c. The connection elements are configured to be separated after insertion into the one or more contact holes 150a, 150c.

The connection elements may be connected to each other according to a predefined raster. The raster may be any regular or repetitive pattern but is not limited to such pattern. It can also be any kind of regular or irregular connection, e.g., via tie bars or other elements. Such connection elements facilitate mass production. The connected elements (by e.g. tie bars) can be separated again by a cutting tool after insertion.

A raster configuration can be helpful to minimize tooling cost as attempt to re-use a pressing tool-plate.

The one or more contact elements 130a, 130c may comprise a galvanically deposited metal layer being formed after insertion of the contact elements to increase an electrical contact area with the respective terminal pad 111 in order to reduce an electrical and/or thermal resistance and to protect the contact area by metallic sealing. Here, the galvanically deposited metal layer means an additional post insertion deposited metal layer. Such post insertion metallization is intended to increase the area of electrical contact by closing gaps.

In one example, the molded power module 100 may comprise a single side cooled power module.

The molded power module 100 can be efficiently produced on panel level. Many contacts between a contact element 130a, 130b, 130c, 130d and a respective contact hole 150a, 150b, 150c, 150d can be produced at a time by parallel processing or batch processing. The molded power module can be applied as a single side cooled module with power terminals in the form of pins on the upper surface, for example. The pin layout is fully customizable.

The main features of such single side cooled molded power module 100 can be summarized as follows.

The single side cooled molded power module 100 with mold body 140 has open contact holes 150a, 150b, 150c from the outer surface to the metallization of the substrate 120 or the die 110.

The contact holes 150a, 150b, 150c, 150d have an undercut profile 151 created by sacrificial material which retains its shape during molding and can be removed completely after molding. The undercut profile 151 is a feature which is part of a lock-in function (cannot be produced by prior art drilling/lasering/molding) that allows unidirectional insertion of a power pin into the contact hole 150a, 150b, 150c, 150d and holding it in place to fulfil its purpose during the lifetime of the product.

The contact elements 130a, 130b, 130c, 130d may comprise 3 sections: a) External section 131 protruding from the upper surface; b) Middle section 132 with lock-in features in x/y dimension; and c) Contact section 133 with elasticity and compliance in z dimension to maintain and constrain the contact force onto the pad of the die/substrate during the lifetime of the product.

There can be different types of contact elements 130a, 130b, 130c, 130d for different current carrying capabilities, as described in the embodiments below.

The lock-in function can be realized in different ways, as described in the embodiments below.

The insertion can be done during production in different ways, as described in the embodiments below.

In case of direct contact to the chip surface, a metallization reinforcement on the chip pad 111 , 112, 113 can be necessary in order to protect the chip 110 from damage and contamination.

Figure 2 shows a schematic cross section of the molded power module 100 shown in figure 1 , without contact elements inserted in the contact holes.

The molded power module 100 shown in Figure 2 is the same as shown in Figure 1 , but in contrast to Figure 1 , no contact elements 130a, 130b, 130c are inserted in the contact holes 150a, 150b, 150c.

The contact elements 130a, 130b, 130c may be inserted in the contact holes 150a, 150b, 150c during the panel level packaging or may be inserted after the panel level packaging, e.g., when the molded power module 100 is applied in the field.

While the molded power module 100 shown in Figures 1 and 2 represent the general design of such a molded power module, further embodiments that represent variations that replace and vary the function of the lock-in mechanism and the insertion method during production, are described in the following Figures.

Figures 3a and 3b show different schematic cross sections of a molded power module 100 illustrating a lock-in feature for a power pin 301 , a signal pin 302 and an alternative signal pin 303 by barbed spring metal contact element during insertion (Figure 3a) and after insertion (Figure 3b).

These figures 3a and 3b represent a first embodiment where the lock-in feature is realized by barbed spring feature of the metal contact element.

This embodiment describes contact elements 301 , 302, 303 elastic barbed features that snap into the support recess of the contact hole during insertion. Different implementations are shown for signal or low power connections 302, 303 (middle and right-side pictures) and for large area contact elements with array of dimples 301 (left-side picture) to make point contact with the pad of the die/substrate.

After insertion as shown in Figure 3b, the contact element 301 , 302, 303 is clamped between the undercut step 151 or recess in the sidewall of the contact hole upper section and the bottom metallization 310 of the contact hole 150c, 150a.

Figures 4a and 4b show different schematic cross sections of a molded power module 100 illustrating a lock-in feature for a power pin 401 and a signal pin 402 by plastic deformation of the metal contact element, e.g. the pin during insertion (Figure 4a) and after insertion (Figure 4b) for different shaped contact holes 410a/b, 411a/b.

These figures 4a and 4b represent a second embodiment where the lock-in feature is realized by plastic deformation driven by insertion and deflected to act orthogonal to the direction of insertion which is represented by the force F applied to the contact element 130c, 130a.

Figure 4a further shows that contact elements can be inserted simultaneously from a pre- loaded carrier plate, e.g., a press plate 420, which is pressed against the panel (parallel, batch processing).

The contact hole may be conically shaped 410a for receiving a power pin 401 or conically shaped 410b to receive a signal pin 402. Alternatively, the contact hole may have a recess with non-conically side walls 411a for receiving a power pin 401 or a recess with non-conically shaped side-walls 410b to receive a signal pin 402.

In a third embodiment (not shown in Figure 4), the lock-in feature may be realized by buckling action triggered by touching the bottom of the contact hole 150a, 150c.

Figure 5a shows a schematic cross section of a molded power module 100 illustrating the lock- in feature by plastic deformation for a different shaped power pin 501 after insertion.

The locking feature results from the plastic deformation of the contact section 133 and the fixation element 135 of the contact element, e.g. the power pin 501.

In this implementation, the contact element 501 , 130c may comprise one or more fixation elements 135 that engage with the upper main face 140a of the mold compound 140 to clamp the contact element 501 , 130c against the upper main face 140a of the mold compound 140.

As described above with respect to figure 4, the contact hole may have a recess with non- conically side walls 411a for receiving the power pin 501 .

In a seventh embodiment, the insertion of the power pins and signal pins may be performed by using a structured metal sheet 510.

Figure 5b shows a top view of an example of the structured metal sheet 510 for insertion of the signal pins and power pins. In particular, Figure 5b shows a metal sheet 510 of connection elements connected together by tie-bars. The cross section of this metal sheet 510, which may reveal a 3D structure, e. g. formed by stamping/coining of a metal sheet, is presented above the metal sheet 510 shown in Figure 5b.

The structured metal sheet 510 may be used for insertion of contact elements simultaneously. The structured metal sheet 510 may form the contact elements that may be connected with each other on the metal sheet 510.

The contact elements can be connected by tie bars and can be separated in a succeeding step after insertion at panel level. For insertion at panel level a metal plate with raster holes to appropriately accommodate the external part of the contact elements can be used to apply the pressure uniformly utilizing a typical lamination press, for example. In a fourth embodiment (not shown in the Figures), the mold body 140 may have partially filled through mold contact holes, e.g., partially metallized contact holes. The metallization can provide mechanical protection, corrosion protection and contamination protection of the sensitive die surface or substrate surface at the bottom of the contact hole. It can be realized by means of standard PCB type processes for blind via metallization utilizing a seeding process followed by an electro-galvanic or a chemical metal deposition process from a liquid. Importantly, those processes are by standard available on a panel level.

The metallization can also take the function of a gliding medium to facilitate a press-in insertion of a contact element directly into the contact hole. The metallization electrically connects the sidewall of the contact hole with the substrate or chip metallization at the bottom of the contact hole. The metallization can form a cold-welded connection with the contact element during insertion.

In combination with the contact hole inner sidewall undercut step, a more reliable lock-in press- fit connection can be made.

In a fifth, sixth, seventh and eighth embodiment (not shown in the Figures), the method of insertion of the contact elements during production can be varied as follows.

In the fifth embodiment, contact elements can be inserted sequentially one-by-one into the contact openings of the panel (sequential insertion, discrete insertion, serial process).

In the sixth embodiment, contact elements can be inserted simultaneously from a pre-loaded carrier plate, e.g., a press plate 420 shown in Figure 4, which is pressed against the panel (parallel, batch processing).

In the seventh embodiment, contact elements can be inserted simultaneously, e.g., by using a structured metal sheet 510 with connected contact elements as described above.

After inserting the contact elements, the contact elements can be separated by a cutting process like for example laser cutting, sawing, etc. Alternatively, after inserting the contact elements, a subsequent galvanic reinforcement metallization can be applied, e.g., to reinforce the point shaped electrical connection and increase the current capability of the power terminal. After applying the reinforcement metallization, the contact elements can be separated by a cutting process like for example laser cutting, sawing, etc. In the following, main points of the embodiments introduced in this disclosure are summarized.

By utilizing sacrificial material for contact hole formation through the mold body of a molded single side cooled (SSC) high power module any-shape contact holes and any-shape inner sidewall profiles can be realized.

An SSC power module is presented that has a mold body with through mold contact holes having an undercut sidewall profile. This enables lock-in function of a corresponding metal pin contact element.

An SSC power module is presented that has a mold body with or without partially metallized through mold contact holes having an undercut sidewall profile. This enables combination of press-fit and lock-in function for enhanced reliability of the power terminal connection.

A high-power module is presented with power and signal pins having a lock-in insertion function in combination with the corresponding contact hole. This enables cost-effective high- throughput manufacturing of high power modules with power terminals.

Contact holes and contact elements are presented that can be manufactured and integrated into a panel level packaging production process.

Reinforcement plating of inserted contact elements can be applied. This can increase current capability and reliability of power terminals.

While a particular feature or aspect of the disclosure may have been disclosed with respect to only one of several implementations, such feature or aspect may be combined with one or more other features or aspects of the other implementations as may be desired and advantageous for any given or particular application. Furthermore, to the extent that the terms "include", "have", "with", or other variants thereof are used in either the detailed description or the claims, such terms are intended to be inclusive in a manner similar to the term "comprise". Also, the terms "exemplary", "for example" and "e.g." are merely meant as an example, rather than the best or optimal. The terms “coupled” and “connected”, along with derivatives may have been used. It should be understood that these terms may have been used to indicate that two elements cooperate or interact with each other regardless whether they are in direct physical or electrical contact, or they are not in direct contact with each other. Although specific aspects have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art that a variety of alternate and/or equivalent implementations may be substituted for the specific aspects shown and described without departing from the scope of the disclosure. This application is intended to cover any adaptations or variations of the specific aspects discussed herein.

Although the elements in the following claims are recited in a particular sequence with corresponding labeling, unless the claim recitations otherwise imply a particular sequence for implementing some or all of those elements, those elements are not necessarily intended to be limited to being implemented in that particular sequence.

Many alternatives, modifications, and variations will be apparent to those skilled in the art in light of the above teachings. Of course, those skilled in the art readily recognize that there are numerous applications of the disclosure beyond those described herein. While the disclosure has been described with reference to one or more particular embodiments, those skilled in the art recognize that many changes may be made thereto without departing from the scope of the disclosure. It is therefore to be understood that within the scope of the appended claims and their equivalents, the disclosure may be practiced otherwise than as specifically described herein.

Claims

CLAIMS:

1. A molded power module (100), comprising: a thermally conductive and electrically isolating substrate (120); at least one power semiconductor die (110) having a top surface (110a) and a bottom surface (110b) opposing the top surface (110a), wherein the bottom surface (110b) is attached to the substrate (120), the at least one power semiconductor die (110) comprising one or more terminal pads (111 , 112, 113) formed on the top surface (110a) for electrically connecting the at least one power semiconductor die (110); a mold compound (140) at least partially encapsulating the at least one power semiconductor die, the mold compound having an upper main face (140a) and a lower main face (140b) opposing the upper main face (140a), wherein the upper main face (140a) faces the top surface (110a) of the at least one power semiconductor die (110); and one or more contact holes (150a, 150c) penetrating the mold compound (140) from the upper main face (140a) of the mold compound (140) to a respective terminal pad (111) on the top surface (110a) of the at least one power semiconductor die (110); wherein each contact hole (150a, 150c) is formed with an undercut profile (151), the undercut profile (151) enabling unidirectional insertion of a contact element (130a, 130c) into the contact hole (150a, 150c) for electrically contacting the respective terminal pad (111).

2. The molded power module (100) of claim 1 , wherein the undercut profile (151) enables beside unidirectional insertion of the contact element (130a, 130c) also locking of the contact element (130a, 130c) in the contact hole (150a, 150c).

3. The molded power module (100) of claim 1 or 2, wherein the substrate (120) comprises an upper metallization layer (121), a lower metallization layer (123) opposing the upper metallization layer (121) and an insulating layer (122) between the upper metallization layer (121) and the lower metallization layer (123), wherein the bottom surface (110b) of the at least one power semiconductor die (110) is attached to the upper metallization layer (121); wherein the substrate (120) comprises one or more substrate pads (124) formed on the upper metallization layer (121) for electrically connecting the upper metallization layer (121); wherein the molded power module (100) comprises: one or more further contact holes (150b, 150d) penetrating the mold compound (140) from the upper main face (140a) of the mold compound (140) to a respective substrate pad (111) on the upper metallization layer (121) of the substrate (120); wherein each further contact hole (150b, 150d) is formed with an undercut profile (151), the undercut profile (151) enabling unidirectional insertion of a contact element (130b) into the further contact hole (150b, 150d) for electrically contacting the respective substrate pad (124).

4. The molded power module (100) of any of the preceding claims, wherein each contact hole (150a, 150c, 150b, 150d) comprises a first axial section (153) having a first width and an adjoining second axial section (154) having a second width that is larger than the first width; wherein the first axial section is formed at the upper main face (140a) of the mold compound (140).

5. The molded power module (100) of any of the preceding claims, wherein a first contact hole (150a) of the contact holes (150a, 150c, 150b, 150d) is configured to receive a signal pin; and wherein a second contact hole (150c) of the contact holes (150a, 150c, 150b, 150d) is configured to receive a power pin; wherein the first width of the first axial section (153) of the second contact hole (150c) is larger than the first width of the first axial section (153) of the first contact hole (150a); and/or wherein the second width of the second axial section (154) of the second contact hole (150c) is larger than the second width of the second axial section (154) of the first contact hole (150a).

6. The molded power module (100) of any of the preceding claims, wherein the undercut profile of the contact hole (150a, 150c) comprises one of the following: a step or multi-step sidewall profile; an inwards slanted sidewall profile; a concave or convex sidewall profile; a hyperboloid sidewall profile.

7. The molded power module (100) of any of the preceding claims, comprising: one or more contact elements (130a, 130c) electrically contacting the respective terminal pad (111), the one or more contact elements (130a, 130c) being attached to the respective terminal pad (111) via the contact hole (150a, 150c) above the respective terminal pad (111).

8. The molded power module (100) of claim 7, wherein each contact element (130a, 130c) comprises: an external section (131) protruding from the upper main face (140a) of the mold compound (140); a contact section (133) contacting the respective terminal pad (111); and a middle section (132) between the external section (131) and the contact section (133), the middle section (132) formed to lock the contact element (130a, 130c) in the contact hole (150a, 150c) above the respective terminal pad (111).

9. The molded power module (100) of claim 7 or 8, wherein each contact element (130a, 130c) comprises one or more spring elements

(134) that engage with an undercut of the contact hole (150a, 150c) to clamp the contact element (130a, 130c) in the contact hole (150a, 150c) above the respective terminal pad (111).

10. The molded power module (100) of any of claims 7 to 9, wherein each contact element (130a, 130c) comprises one or more fixation elements

(135) that engage with the upper main face (140a) of the mold compound (140) to clamp the contact element (130a, 130c) against the upper main face (140a) of the mold compound (140).

11 . The molded power module (100) of any of claims 7 to 10, wherein the one or more contact elements (130a, 130c) are made of metal.

12. The molded power module (100) of any of claims 7 to 11 , wherein the one or more contact elements (130a, 130c) attached to the respective terminal pad (111) are plastically deformed compared to their original shape; wherein a locking of the contact element (130a, 130c) results from the plastic deformation.

13. The molded power module (100) of any of claims 7 to 12, wherein the one or more contact elements (130a, 130c) attached to the respective terminal pad (111) are buckled compared to their original shape; wherein a locking of the contact element (130a, 130c) results from the buckling of the contact element.

14. The molded power module (100) of any of claims 7 to 13, wherein the one or more contact holes (150a, 150c) are at least partially filled by a metal layer.

15. The molded power module (100) of any of claims 7 to 14, wherein the one or more contact elements (130a, 130c) comprise connection elements which are configured to connect the one or more contact elements (130a, 130c) with respect to each other before insertion into the one or more contact holes (150a, 150c), wherein the connection elements are configured to be separated after insertion into the one or more contact holes (150a, 150c).

16. The molded power module (100) of any of claims 7 to 15, wherein the one or more contact elements (130a, 130c) comprise a galvanically deposited metal layer, the galvanically deposited metal layer being formed after insertion of the contact elements for increasing an electrical contact area with the respective terminal pad (111) in order to reduce an electrical and/or thermal resistance and to protect the contact area by metallic sealing.

17. The molded power module (100) of any of the preceding claims, comprising a single side cooled, SSC, power module.