Method of attaching terminals to an insulated metal base structure of a semiconductor power module and semiconductor power module

Abstract

A method for attaching a terminal (4) to an insulated metal base structure (3) for a semiconductor power module (10) comprises providing at least one terminal (4) and providing an insulated metal base structure (3) having a metal top layer (17), a metal bottom layer (19) and an insulating resin layer (18) arranged between the metal top layer (17) and the metal bottom layer (19). The method further comprises providing a sintering layer (5) and coupling it to the metal top layer (17) and / or to the at least one terminal (4) to form a sintering area for the at least one terminal (4). The method further comprises coupling the at least one terminal (4) to the metal top layer (17) by means of sintering using a sintering tool (6) such that the sintering layer (5) is arranged between the metal top layer (17) and the at least one terminal (4) and connects the at least one terminal (4) to the metal top layer (17).

Description

TECHNICAL FIELD

[0001] The present disclosure relates to a method of attaching terminals to an insulated metal base structure of a semiconductor power module. The present disclosure also relates to a semiconductor power module. BACKGROUND

[0002] Conventional insulated metal bases for low power and medium power semiconductor packaging technologies have both low insulation requirements and low thermal resistance requirements. Terminals are attached to the insulated metal base and need to be reliably and cost-effectively connected to the insulated metal base. SUMMARY

[0003] Embodiments of the present disclosure relate to a method for attaching terminals to an insulated metal base structure, which facilitates cost savings for semiconductor power modules and enables reliable functionality even in high voltage power module applications where reliability requirements are high. Other embodiments of the present disclosure relate to corresponding semiconductor power modules.

[0004] According to one embodiment, a method for attaching terminals to an insulated metal base structure for a semiconductor power module includes providing at least one terminal and providing an insulated metal base structure having a metal top layer, a metal bottom layer, and an insulating resin layer arranged between the metal top layer and the metal bottom layer. The method further includes providing a sintering layer and coupling it to a top surface of the metal top layer and / or a bottom surface of the at least one terminal to form a sintering area for the at least one terminal. The method further includes coupling the at least one terminal to the metal top layer using sintering with a sintering tool such that the sintering layer is arranged between the metal top layer and the at least one terminal and connects the at least one terminal to the metal top layer.

[0005] Thanks to the method, sintering bond connections can be achieved on the insulated metal base structure, which can facilitate stable and reliable operation of the semiconductor power module, even for high voltage power module applications. For example, the method also facilitates secure attachment of the terminals on the insulated metal base structure by sintering while reducing the risk of damage to the insulating resin layer. The insulated metal base structure enables cost-effective technology for power semiconductor modules with low insulation and low thermal resistance requirements and enables large size power modules to be used for low, medium, and high voltage range applications. The method can also facilitate achieving sintering bond connections on the insulated metal base structure such that the semiconductor power module with such an insulated metal base structure can operate stably and reliably.

[0006] It was found in the context of the present disclosure that alternative joining techniques, such as soldering techniques, are able to provide reliable joining connections, but are considered to be of vital importance in view of a stable process on the base with the insulating resin sheet without damaging the base structure. In particular, ultrasonic welding is accompanied by a strong influence of thermal and mechanical stresses on the base structure due to the high friction and pressure between the terminal leg and the base. The resin sheet is significantly softer than the ceramic here, but also brittle due to the incorporation of inorganic fillers, severely endangered by deformation and crack formation. During the ultrasonic welding process, a corresponding deformation of the underlying soft layer can occur, for example for thick copper wires ultrasonically bonded on thin soldered copper plates. The soft solder layer below the copper wire is subjected to a similar strong deformation as the soft resin sheet of the insulating metal base structure when the terminal leg is soldered thereto.

[0007] Ultrasonic welding experiments on insulating metal base structures confirmed these expectations, i.e. a severe damage in the insulating resin sheet during the welding process, so that ultrasonic welding on insulating metal base structures appears to be very difficult or even impossible. At least, there is an inadmissible risk that due to the welding technique, the interface of the insulating resin sheet below the welded terminal leg contains defects. Additionally, it can be assumed that laser welding or other welding techniques are also severe in terms of damage to the base and in particular to the resin sheet due to the strong thermal impact and the introduced mechanical stresses. The resin sheet is severely endangered by deformation and crack formation. Furthermore, there is a risk of delamination of the metallization from the resin sheet layer. When applying ultrasonic welding or laser welding or other terminal leg welding techniques on the circuit metallization of an insulating metal base structure, a corresponding failure mode can occur.

[0008] By using the described method for manufacturing an insulating metal base structure with one or more soldered terminals, the above-mentioned adverse effects due to the soldering of the terminals with the metal top layer can be counteracted. The soldering process is able to reduce the mechanical and thermal stresses acting on the underlying layers of the insulating metal base structure. The risk of crack formation or damage in the insulating resin layer and delamination of the metal top layer can be reduced and a stable semiconductor power module can be achieved, which is able to reliably operate even in high-voltage power module applications, for example in the voltage range of 0.5 kV up to 10.0 kV.

[0009] According to one embodiment of the method, the step of providing and coupling the sintering layer comprises providing a substance with pre-determined sintering particles and applying the substance (e.g. by means of printing) onto the top surface of the metal top layer, thereby forming a sintering area with a pre-formed sintering layer. The substance refers to a sintering raw material, e.g. in the form of a thin film or paste, which can be printed onto the metal top layer in pre-determined locations. The sintering material and thus the sintering layer can be provided in a pre-determined manner as a pumpable liquid or viscous paste, including at least one of silver, copper, gold and nickel or other applicable metals as the main material. Alternatively or additionally, the sintering raw material can be provided as a solid sheet or pre-formed piece attached to the base and / or the terminal. Alternatively or additionally, the sintering material can be another material applicable by sintering. The sintering raw material can be pre-applied in given locations on the insulated metal base structure to have a ready structure.

[0010] The sintering material can include micro- and / or nano-particles of the main components, which are capable of forming a firm bond connection or material bond connection between the one or more terminals and the metal top layer. The sintering layer or the sintering material forming the sintering layer can include a material composition with a polymer and / or a solvent, adhesive or reagent in the raw material, which is removed during the sintering process. The sintering layer enables a more porous or less porous paste (with a more porous or less porous shape) of a material typically being pure metal, which is different from the material of the terminals and the metal top layer (which can be achieved by bulk copper or aluminum) in view of the sintering connection between the one or more terminals and the insulated metal base structure.

[0011] Sintering is a process of compacting and forming a solid mass of material by heat and / or pressure without melting the joint partners to the liquidus point. A sintering tool can be used to apply pressure and / or to apply heat to bake the terminals and the metal top layer together with the sintering layer therebetween. Thus, sintering can be described as baking the particles together, whereas joining is done by a diffusion process between the particles.

[0012] According to another embodiment of the method, the sintering is performed at a high pressure of at most 20 MPa applied to the at least one terminal. For example, the high pressure is set in the range of 5 MPa to 25 MPa. For example, the sintering of the terminals and the metal top layer can be performed at a high pressure of up to 10 MPa or 15 MPa. Generally, the relatively high pressure acting on the joint partners makes the quality of the sintered joint reliable, which also depends on the porosity of the sintering material. In this case, the sintering layer has a low porosity and / or a high density. Thus, the pressure for sintering is given in coordination with the joint partners and the selected sintering material.

[0013] According to a further embodiment of the method, the sintering is performed at a low pressure of at most 2 MPa applied to the at least one terminal. For example, the sintering of the terminals and the metal top layer can be performed at a low pressure of 0.2 MPa, 0.5 MPa, 1 MPa or 1.5 MPa. The choice of the sintering pressure also depends on the sensitivity of the joint partners to pressure. In this case, in particular the resin sheet of the base is rather sensitive. For example, the terminal or terminals are part of an electronic device, such as a chip, and high pressures should not be used in order to reduce the risk of damaging the chip and / or the insulating resin layer. If sintering is performed using a low pressure, the terminals can be fixed or held in place using a rubber or positioning tool, which can also be part of the sintering tool. Furthermore, the sintering of the terminals and the metal top layer can be performed without pressure, such that no additional pressure or very low pressure is used during sintering.

[0014] According to a further embodiment of the method, the step of providing the at least one terminal comprises providing the at least one terminal with a given stress release structure. The stress release structure can comprise at least one of a spring structure, a thinned portion and a groove implemented onto the terminal or terminals in order to beneficially influence the sintering process.

[0015] According to a further embodiment of the method, the step of providing the at least one terminal comprises providing the at least one terminal with a given stress release structure. The stress release structure can comprise at least one of a spring structure, a thinned portion and a groove implemented onto the terminal or terminals in order to beneficially influence the sintering process.

[0016] The terminal or terminals can be made of or comprise at least one of copper, a copper alloy, aluminum and an aluminum alloy or any other applicable metal or other electrically conductive material. The metal top layer can also be made of or comprise at least one of copper, a copper alloy, aluminum and an aluminum alloy or any other applicable metal or other electrically conductive material.

[0017] According to a further embodiment of the method, the metal top layer is provided with a coating on the top face, which is configured to face the bottom face of the sintering material or the at least one terminal during sintering. Alternatively or additionally, the at least one terminal is provided with a coating on the bottom face, which is configured to face the sintering layer or the metal top layer of the insulating metal base structure during sintering. Such a coating can be used to facilitate a joint connection between the terminal, the sintering material film and / or the base metallization achieved by the metal top layer.

[0018] One or more of the above-mentioned coatings of the terminals and the metal top layer can be made of or comprise noble metals, such as nickel and / or silver and / or gold, and / or one or more other metals. Such coatings can help to prevent oxidation and / or improve the conditions of the sintering process and / or can also protect the insulating resin layer of the insulated metal base structure. The respective coating can partially or completely cover the predetermined face of the bottom face of the terminal or the predetermined face of the top face of the metal top layer. Furthermore, the respective coating can comprise one or more layers.

[0019] The insulating resin layer forms a dielectric layer and can be realized as a prepreg which is assembled between the two metal sheets of the top and bottom part forming the metal top layer and the metal bottom layer. Such a metalized sheet or plate is bonded to the dielectric resin layer, for example, by a lamination process. The desired metallization structure of the metal top layer can then be completed by subsequent mask and etching process steps to locally remove the conductive metal to form the final metallization structure. Alternatively, the top metallization structure can be formed by cutting or stamping, for example, before the finished insulated metal base structure is shaped.

[0020] Alternatively, the insulating resin layer can be formed by molding. For such a molded dielectric layer, the molding substance realizes a pumpable molding substance with predetermined material properties. The molding substance is a liquid or viscous raw material of the insulating resin layer to be formed. For example, the molding substance is an epoxy resin and / or a ceramic-based liquid. Alternatively or additionally, the raw material of the dielectric layer can be a thermoset or thermoplastic resin material, such as polyamide, PBT, PET. Alternatively or additionally, the raw material of the dielectric layer can comprise inorganic fillers, such as based on ceramic materials, for improved thermal conductivity and / or CTE adjustment with respect to the metal top layer and / or the metal bottom layer. For example, the molded dielectric layer comprises a resin-based dielectric material with ceramic filler material, such as AI2O3, AIN, BN, Si3N4, or SiO2. For example, the dielectric layer is an epoxy resin with fillers. The dielectric layer can also be based on other materials suitable for transfer, injection or compression molding or other suitable molding techniques, such as bismaleimides, cyanate esters, polyimides, and / or silicones. Alternatively or additionally, the dielectric layer can comprise ceramic materials and / or wet-stated materials or a combination of two or more of the above-mentioned components.

[0021] The metal top layer and the metal bottom layer are aligned relative to each other with a predetermined distance between both, which will basically predetermine the subsequent thickness of the molded dielectric layer. For example, the thickness is defined along a stacking direction of the insulated metal base structure, which can be represented as a z-direction. However, the alignment can also be made in orthogonal x- and y-directions for suitable positioning, for example of the metal pattern relative to the x- and y-directions. The alignment can be achieved, for example, by placing the metal top layer on a release film or liner or other fixation means, for example in a mold slot of a molding tool. This enables a precise positioning of the metallization structure provided by the metal top layer relative to the metal bottom layer and can be helpful if the metal top layer comprises a separate metal pad, for example due to different operating potentials. In case of lamination, the thickness of the insulating resin layer is determined by the thickness and behavior of the lamination layer.

[0022] The thickness of the insulating resin layer can be a value of 50 pm up to 300 pm. The thickness of the metal top layer can be a value of 0.15 mm up to 0.5 mm or 0.15 mm to 2.00 mm. The terminal can comprise an L-shape, wherein a long terminal body mainly extends along the stacking direction and a terminal leg mainly extends along a lateral direction which is substantially perpendicular to the stacking direction. The terminal leg can form a plate with a thickness of 0.5 mm up to 1.5 mm relative to the stacking direction. The thickness of the terminal leg and / or a sintered area formed by the sintering process can be, for example, smaller compared to other parts of the terminal. For example, the lateral dimension or area of the terminal leg can be larger or smaller than the respective extension of the sintered layer. One or more terminals can implement a main terminal of the semiconductor power module for a power connection or an auxiliary terminal for an electrical signal connection or signal wiring.

[0023] The at least one terminal can further comprise a structure prepared for improved sintering. For example, such sintering structure can be implemented by a roughened area or a thinned area in the terminal leg of the terminal, one or more slots, grooves and / or notches. Such sintering structure can be prepared on a top side and / or a bottom side of the respective terminal and / or on a top surface of the metal top layer. The specific terminal structure can beneficially influence the sintering process and can contribute to the formation of a material bond or a strong bonded sinter joint.

[0024] By using the described manufacturing or attachment method for joining the terminal to the insulated metal base structure, adverse effects can be counteracted. For example, the risk of cracks, deformations or the formation of other damages can be reduced, especially in the insulating resin layer of the insulated metal base structure, and a stable semiconductor power module can be realized at low cost, enabling a reliable operation of the semiconductor power module with enhanced durability or service life.

[0025] Finally, it is pointed out that all features and methods presented can be used individually or in combination of two or more.

[0026] According to an embodiment, the semiconductor power module comprises a base having a metal top layer, a metal bottom layer and an insulating resin layer coupled to and arranged between the metal top layer and the metal bottom layer. The semiconductor power module further comprises at least one terminal and a sintered layer. The sintered layer is arranged between the metal top layer and the at least one terminal with respect to a stacking direction of the semiconductor power module. The sintered layer connects a bottom face of the at least one terminal to a top face of the metal top layer by means of sintering.

[0027] Since the semiconductor power module can be manufactured by means of the above-mentioned embodiments of the method, the features and characteristics of the method are also disclosed for the semiconductor power module and vice versa. Thus, the present disclosure comprises a plurality of aspects, wherein all features described with respect to one of the aspects are also disclosed with respect to the other aspects, even if the respective features are not explicitly mentioned in the context of a particular aspect.

[0028] According to an embodiment of the semiconductor power module, the at least one terminal comprises a given stress release structure, for example having at least one spring structure, a thinned portion and a recess. Thus, the respective terminal can have a spring segment or a resilient portion to realize a cushioning structure or a stress release structure which helps to protect the insulating resin layer from mechanical and / or thermal shocks.

[0029] According to another embodiment, the semiconductor power module comprises a plurality of terminals which are coupled to the housing block and / or the lead frame on the one hand and which are connected to the top face of the metal top layer by means of sintering on the other hand, respectively. The housing block can be formed as a resin body and the plurality of terminals can be partially embedded into the resin body.

[0030] The semiconductor power module can further comprise a heat sink which is coupled to the metal bottom layer of the insulating metal base structure to dissipate heat during operation of the semiconductor power module. The metal bottom layer forms a bottom of the insulating metal base structure and can be made of or comprise copper, aluminum and / or respective alloys thereof. Thus, the semiconductor power module can comprise a separate heat sink. The additional heat sink can also be made of copper, aluminum and / or respective alloys thereof or of a composite material, such as aluminum-silicon carbide or magnesium-silicon carbide. Alternatively or additionally, the metal bottom layer of the insulating metal base structure can itself be used as a heat sink, for example, a bottom side with respect to the stacking direction can be configured to comprise ribs, fins or protrusions to provide beneficial heat dissipation. The metal bottom layer can also be used as a substrate of the semiconductor power module.

[0031] The semiconductor power module comprising the insulating metal base structure can also be partially or completely encapsulated by a dielectric gel or a resin prepared by molding or potting. Furthermore, the semiconductor power module can comprise two or more embodiments of the above-mentioned cushioning structure. The semiconductor power module can further comprise electronic devices, for example chips, integrated circuits, sensors and / or other discrete devices.

[0032] The presented process of sintering the terminal legs onto the surface of the insulated metal base structure has a great potential compared to soldering technology, for example, it can reduce the mechanical and thermal impact of the bonding process on the resin insulation sheet. The sintering process does not damage the insulation resin layer, which is sensitive to heat and pressure, making it interesting to use this rather cost-effective base technology. This attachment or manufacturing method for insulated metal base structures can be interesting for large power modules with enhanced reliability requirements and for power modules for higher voltage classes. However, the method allows the manufacture of insulated metal base structures and semiconductor power modules that can be applied to a variety of products, for example, low-voltage industrial and automotive products operating in the 1.7 kV or below voltage range, but also for products of higher voltage classes. When replacing the standard mounting of a ceramic base soldered to the substrate by an insulated metal base structure, the costs can be significantly reduced. On the one hand, material costs can be reduced, on the other hand, several other process steps, for example, the bonding process between the base and the substrate in the assembly of a power module, are not required and can thus be removed from the process flow. BRIEF DESCRIPTION OF DRAWINGS

[0033] In the following exemplary embodiments will be explained by means of the schematic drawings and the drawing references. The drawings show:

[0034] Figures 1 to 3 An embodiment of a method for attaching a terminal to an insulated metal base structure of a semiconductor power module is shown in a corresponding side view; and

[0035] Figure 4 A flow chart of a method for attaching one embodiment of a terminal to an insulated metal base structure is shown.

[0036] The drawings are included to provide a further understanding of the present application. It should be understood that the embodiments shown in the drawings are illustrative representations and are not necessarily drawn to scale. The same reference numerals in different drawings represent the same or similar elements or components. Descriptions of elements or components in different drawings are not repeated for each drawing in which they appear, as long as they correspond to each other in their function. For the sake of clarity, elements can not appear in all the drawings with corresponding reference numerals. DETAILED DESCRIPTION

[0037] Figure 1 A side view of an embodiment of the method steps for attaching a terminal leg or terminal 4 to an insulated metal base structure 3 of a semiconductor power module 10 for a semiconductor device is shown. The semiconductor power module 10 comprises an insulated metal base structure 3 having a metal top layer 17, a metal bottom layer 19 and an insulation resin layer 18 arranged between the metal top layer 17 and the metal bottom layer 19 with respect to a stacking direction A.

[0038] The semiconductor power module 10 further comprises a cooler or heat sink 1 with a fin structure or rib structure, which is coupled with the insulated metal base structure 3 by a bonding layer 2 and / or a thermal interface material layer. Relative to the shown stacking direction A, one or more terminals 4 are to be coupled to the metal top layer 17, and the heat sink 1 is coupled at the bottom with the metal bottom layer 19 by a bonding layer 2.

[0039] In this regard, terms such as "above", "below", "top", "upper" and "bottom" refer to the orientation or direction relative to the stacking direction A as shown in the figures. Thus, the height or thickness of the elements is related to the stacking direction A, while the lateral direction B is perpendicular to the stacking direction A (see Figures 1 to 3 ).

[0040] The thickness of the insulating resin layer 18 can be for example 100-200 pm. The thickness of the circuit metallization formed by the metal top layer 17 can be 0.15-2.00 mm. The thickness of the metal bottom layer 19 of the substrate can be 1-5 mm and can also be configured to dissipate heat from the insulated metal base structure 3 and the semiconductor power module 10. The insulating resin layer 18 can comprise an epoxy resin material, but can also be another thermoset resin or other type of resin, for example a thermoplastic resin. The insulating resin layer 18 can be formed as a resin sheet or prepreg sheet that is assembled or laminated between the two metal layers 17, 19.

[0041] Alternatively or additionally, the insulated metal base structure 3 comprises the insulating resin layer 18 formed by molding, for example by injection, transfer molding or compression molding. The resin of the insulating resin layer can contain inorganic fillers, ceramic materials, for example AIN, Si3N4, BN, AI2O3 or SiO2. The metal bottom layer 19 can be made of or comprise copper and / or aluminum and / or respective alloys thereof. The circuit metallization formed by the metal top layer 17 can be made of or comprise copper and / or aluminum and / or respective alloys thereof. Furthermore, the metal top layer 17 can be partially or fully coated, and the respective coating of the circuit metallization can be made of or comprise noble metals, for example nickel and / or gold and / or silver and / or other metals.

[0042] The semiconductor power module 10 further comprises a sintering layer 5, which can comprise silver or copper, and which is arranged between the metal top layer 17 and the at least one terminal 4. The sintering layer 5 serves to connect the bottom face 42 of the terminal 4 to the top face 171 of the metal top layer 17 by sintering. The sintering layer 5 can have a thickness of 20 pm - 50 pm or even up to 250 pm. The sintering layer 5 can be formed thinner and can be pre-applied to one or both of the joint partners in order to reduce costs.

[0043] Sintering can join the main or auxiliary terminals 4 to the insulated metal base structure 3, but also to a corresponding base structure based on alternative technologies, such as stamped and molded metal bases. In contrast to welding technologies, where strong thermal and / or mechanical impacts make the joining process very difficult, only limited static mechanical pressure impacts and moderately increased temperatures have to be considered when joining the terminal legs to the circuit metallization or the metal top layer 17 by means of sintering.

[0044] As shown in Figures 1 to 3 , one or more terminal legs can be joined to the top face 171 of the insulated metal base structure 3 by means of a sintering process. For example, the pressure and / or heat for performing the sintering process can be applied by means of a sintering tool 6 acting on the top face 41 of the terminal 4. However, heat can also be applied to the entire insulated metal base structure 3 and the assembly means used for manufacturing the semiconductor power module 10. The sintering tool 6 can also precisely position or hold the terminal 4 in a specified position during the sintering process. The sintering connection is provided by a sintering material configured to form the sintering layer 5 with particles of micron or sub-micron size of silver, copper or any other material suitable for the sintering process.

[0045] The sintering process can be used for a single terminal 4 or a group of multiple terminals. It is also possible to perform a synchronized sintering process for multiple terminals arranged in a shared terminal or housing block or lead frame (see Figure 3 ). In order to further improve to counteract the mechanical stresses suffered by the joining connection and to contribute to an increased reliability, the terminal 4 can have a stress release structure 7, for example aiming at compensating possible mismatches of the thermal expansion coefficients or compensating mechanical or geometric tolerances in the housing block or terminal structure without increasing the stresses (see Figure 2 ].

[0046] The terminals 4 can be made of, or comprise, copper, aluminum and / or respective alloys thereof, and the terminals 4 can realize main terminals or auxiliary terminals of the semiconductor power module 10. Furthermore, the terminals 4 can comprise a coating which partially or completely covers the top face 41 and / or the bottom face 42 of the terminals 4. Such a coating can beneficially influence the sintering process and / or can protect one or more surfaces of the terminals 4 from oxidation, and can be made of, or comprise, noble metals such as nickel, gold, silver and / or other metals. The coating can also comprise one or more layers of such materials.

[0047] The method steps for attaching the terminals 4 to the insulating metal base structure 3 can be conducted according to the flow chart shown in Fig. 1. In step S1 at least one terminal 4 is provided. The terminals 4 can be provided to comprise one or more coatings on their top face 41 and / or bottom face 42. Figure 4

[0048] In step S2 the insulating metal base structure 3 is provided with a metal top layer 17, a metal bottom layer 19 and an insulating resin layer 18 between the metal top layer 17 and the metal bottom layer 19. A coating can also be applied at least partially on the top face 171 of the insulating metal base structure 3.

[0049] In step S3 a sintering material can be provided to form the sintering layer 5. The sintering material can comprise, for example, microparticles and / or nanoparticles, including silver and / or gold as a substance or raw material. The sintering material can then be applied by printing onto the top face 171 of the metal top layer 17 and / or the bottom face 42 of the terminals 4, thereby forming the sintering region where the sintering layer 5 is to be formed. The sintering material can also be a solid piece or preform which is attached to one of the joint partners.

[0050] In a further step S4 the terminals 4 are pressed against the metal top layer 17 at a specified pressure, and heating of the assembled terminals 4, metal top layer 17 and sintering material therebetween is started. For this purpose, the specified pressure and heat can be applied simultaneously, or the pressure can be applied before or after the heat is introduced into the device. For example, a pre-heating can be conducted before entering the sintering machine. Such a pre-heating process can introduce a temperature setting which is slightly lower than the temperature used in the sintering process.

[0051] Thus, it can be said that the sintering material is baked and transformed into the sintering layer 5 which connects the bottom face 42 of the terminals 4 to the top face 171 of the metal top layer 17 by means of sintering.

[0052] ​One or more terminals 4 can implement primary or secondary terminals and connect their respective terminal pins to the top face 171 of the insulating metal base structure 3 by means of a sintering process. The sintering connection between the terminal pin and the top face 171 is made of particles of silver, copper or other material suitable for the sintering process. The sintering particles can have a diameter in the range of microns or sub-microns. Depending on the type and material of the terminal, the terminal pin has a thickness of 0.5-1.5 mm. In order to improve the sintering process or to protect the joint partners, for example against oxidation, the base top face 171 and / or the top face 41 of the terminal pin and / or the bottom face 42 of the terminal pin can be coated with a metal layer, for example made of nickel, silver and / or gold.

[0053] There can be various arrangements of the terminals 4 to the top face 171 of the insulating metal base structure 3: First, one or more individual terminals 4 can be connected to the top face 171 by means of a sintering process, respectively. Second, a plurality of terminals 4 can be arranged in a group, as is the case in a leadframe, wherein the terminal pins are simultaneously joined to the base metallization, which is realized by the metal top layer 17. Finally, a plurality of terminals 4 arranged in a shared terminal or housing block 8 can be sintered simultaneously (see Figure 3 ). Here, for example, at least a portion of the terminals 4 is embedded in a shared resin body of the housing block 8. The housing block 8 can form a part of the module housing of the semiconductor power module 10, which is prepared by a molding process. For leadframe or housing block terminals, a sequential sintering process is also feasible.

[0054] Additionally, one or more stress release structures 7 can be implemented to one or more terminals 4 (see Figure 2 and Figure 3 ). Such stress release structures can help to compensate for thermal expansion or to compensate for vibrations or other forces or to compensate for mechanical or geometric tolerances in the housing or terminal structure without increasing the stress experienced by the joint connection. The stress release structures 7 of the individual terminals 4 can be implemented by different designs, for example one or more spring portions, thinned portions and / or openings / holes in the terminal axis.

[0055] Compared to conventional joint technologies using ultrasonic welding processes, the sintering process can for example reduce mechanical and thermal impact on the insulating resin layer 18. Additionally, for example in order to form a very stable and reliable connection, one or more terminals 4 can be coupled to the metal top layer 17 by means of soldering, gluing, dry contact, welding and / or any other applicable joint method for fixing to the circuit metallization realized by the metal top layer 17. The terminals 4 can also be coupled to the metal top layer 17 by sintering before forming the insulating metal base structure 3 to further prevent mechanical impact on the insulating resin layer 18.

[0056] The sintering process itself has various alternative realizations depending on the joint partner and / or the sintering material, for example:

[0057] • The sintering can be carried out under high pressure by using a pressure of about 20 MPa or using a pressure value from 5 MPa up to 25 MPa.

[0058] • The sintering can be carried out under low pressure by using a pressure of about 0.5 MPa or using a pressure value from 0.1 MPa up to 5.0 MPa. As far as the terminal or housing block 8 is concerned, in which a plurality of terminals 4 are arranged in a resin body, which can be part of a module housing, the pressure can be applied by the housing block 8 itself.

[0059] • Pressureless sintering;

[0060] • The heating can be carried out in the range of 200 up to 270 °C or up to 290 °C or up to 300 °C.

[0061] The heating and the retaining of the heat can be realized by means of an oven, a heating plate and / or a heated sintering tool for heating the sintering raw material and the joint partner from one or more sides. The pressure can be applied by means of a mechanical pressing element, which can also comprise a positioning and / or fixing structure formed in cooperation with the respective terminal design to be sintered. The sintering material can comprise micron and / or nano sintering particles, wherein larger particles and higher sintering pressure can be used, which also depends on the porosity requirements and the intended application of the semiconductor power module 10.

[0062] For example, the sintering raw material is provided as a paste-like substance with nano-sized silver particles and / or copper particles. Then, by applying a relatively low pressure (from 0.1 MPa up to 5.0 MPa) and applying heat with a temperature of 200 °C - 300 °C in a time range of 1 - 10 minutes or up to 20 minutes, the sintering layer 5 can be formed. Thus, alternatively or additionally, the paste-like substance can comprise micron-sized silver particles and / or copper particles.

[0063] Alternatively, for example, the sintering raw material can be provided as a silver foil and / or a copper foil with micron-sized silver particles and / or copper particles. Then, by applying a relatively high pressure (from 5 MPa up to 25 MPa) and applying heat with a temperature of 200 °C - 300 °C in a time range of 1 minute - 10 minutes or up to 20 minutes, the sintering layer 5 can be formed. The silver particles, gold particles, nickel particles or copper particles can be chosen depending on the cost, the sintering process and its temperature and pressure parameters and / or the design and intended application of the semiconductor power module 10 and / or the requirements on the sintered joints and the porosity of the sintering layer 5.

[0064] The described Figures 1 to 2The illustrated embodiments represent exemplary embodiments of improved insulating metal base structure 3, semiconductor power module 10, and methods of manufacturing thereof; thus, they do not constitute a complete list of all embodiments. Actual arrangements and methods can vary from the embodiments shown, for example, with respect to the insulating metal base structure 3 and semiconductor power module 10.

[0065] Reference numerals

[0066] 1 heat sink

[0067] 2 bonding layer

[0068] 3 insulating metal base structure

[0069] 4 terminal

[0070] 41 top surface of terminal

[0071] 42 bottom surface of terminal

[0072] 5 sintering layer

[0073] 6 sintering tool

[0074] 7 stress release structure

[0075] 8 housing block

[0076] 10 semiconductor power module

[0077] 17 metal top layer

[0078] 171 top surface of metal top layer

[0079] 18 insulating resin layer

[0080] 19 metal bottom layer

[0081] A stacking direction

[0082] B lateral direction

[0083] S (i) step of a method for attaching a terminal to an insulating metal base structure

Claims

1. A method for attaching a terminal (4) to an insulating metal base structure (3) for a semiconductor power module (10), comprising: - Provides multiple terminals (4) coupled to the housing block (8) and / or lead frame. - Provide the insulating metal base structure (3), the insulating metal base structure (3) having a metal top layer (17), a metal bottom layer (19) and an insulating resin layer (18) disposed between the metal top layer (17) and the metal bottom layer (19). - Provide a sintered layer (5) and couple the sintered layer to the top surface (171) of the top metal layer (17) and / or the bottom surface (42) of each of the terminals (4) to form a sintered region of each of the terminals (4), and - The terminals (4) are coupled to the metal top layer (17) by sintering, such that a corresponding sintered layer (5) is arranged between the metal top layer (17) and the associated terminals (4), and the terminals (4) are connected to the metal top layer (17), wherein the coupling of the terminals (4) includes coupling the housing block (8) and / or the lead frame to the insulating metal base structure (3), such that a predetermined pressure for sintering is applied to the plurality of terminals (4) applied through the coupling.

2. The method according to claim 1, wherein the step of providing the sintered layer (5) and coupling the sintered layer comprises: - Provide a substance or sintering raw material having predetermined sintering particles, and - The material or sintering raw material is applied to the top surface (171) of the metal top layer (17) by printing, thereby forming the sintering region and preforming the sintering layer (5).

3. The method according to claim 1, wherein the sintered layer (5) comprises at least one of silver, copper, gold and nickel.

4. The method according to any one of claims 1 to 3, wherein sintering is performed on the at least one terminal (4) under a high pressure of up to 25 MPa.

5. The method according to any one of claims 1 to 3, wherein sintering is performed on the at least one terminal (4) under no pressure or a low pressure of up to 2 MPa.

6. The method according to any one of claims 1 to 3, wherein the step of providing the at least one terminal (4) comprises: Provide at least one terminal (4) having a given stress relief structure (7), wherein the stress relief structure (7) includes at least one of a spring structure, a thinned portion, and a groove.

7. The method according to any one of claims 1 to 3, wherein the at least one terminal (4) and / or the metal top layer (17) is provided as at least one of copper, copper alloy, aluminum and aluminum alloy.

8. The method according to any one of claims 1 to 3, wherein the step of providing the at least one terminal (4) and / or the insulating metal base structure (3) comprises: A coating is provided on the bottom surface (42) of the at least one terminal (4) and / or the top surface (171) of the metal top layer (17), wherein the bottom surface (42) and the top surface (171) are configured to face each other during sintering, and wherein the coating of the at least one terminal (4) and / or the metal top layer (17) comprises one or more layers having at least one of nickel, silver and gold.

9. The method according to any one of claims 1 to 3, wherein the step of providing the insulating metal base structure (3) comprises: - Provide molding materials, - Align the top metal layer (17) and the bottom metal layer (19) relative to each other with a predetermined distance between them, and - The provided molding material is introduced between the aligned metal top layer (17) and the metal bottom layer (19), and thus the insulating resin layer (18) is formed by molding.

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