Method and apparatus for forming a permanent connection between two connecting fittings

Abstract

Methods and apparatus for forming a permanent connection between two connecting fittings are disclosed. One method includes applying a pre-layer (64) to either a first connecting fitting (10) or a second connecting fitting (80); arranging the first connecting fitting (10) on the second connecting fitting (80) such that the pre-layer (64) is arranged between the first connecting fitting (10) and the second connecting fitting (80); heating the first connecting fitting (10), the second connecting fitting (80), and the pre-layer (64) arranged between the first connecting fitting (10) and the second connecting fitting (80); and while heating the first connecting fitting (10), the second connecting fitting (80), and the pre-layer (64), applying pressure to the first connecting fitting (10) to thereby press the first connecting fitting (10) toward the second connecting fitting (80) and form a permanent connection layer (62) between the first connecting fitting (10) and the second connecting fitting (80).

Description

Technical Field

[0001] This disclosure relates to methods and apparatus for forming a permanent connection between two connecting fittings, and in particular for forming a sintered layer between two connecting fittings. Background Technology

[0002] Semiconductor module devices typically include at least one substrate. A semiconductor device comprising multiple controllable semiconductor elements (e.g., two or more IGBTs) is disposed on each of the at least one substrate. Each substrate typically includes a substrate layer (e.g., a ceramic layer), a first metallization layer deposited on a first side of the substrate layer, and a second metallization layer deposited on a second side of the substrate layer. The controllable semiconductor elements are mounted, for example, on the first metallization layer. At least some of the controllable semiconductor elements in the semiconductor module device perform multiple switching operations during operation of the semiconductor module device. For example, when many switching operations are performed within a short period of time, the controllable semiconductor elements generate heat. The heat generated during operation of the semiconductor module device is dissipated primarily from the controllable semiconductor elements to the substrate and further to a heat sink. The substrate is typically sintered to the corresponding heat sink via a sintering layer. The sintering layer deforms upon heating. Typically, during operation of the semiconductor module, some sections of the substrate are heated more than other sections. Therefore, the sintering layer may also be heated unevenly. During the lifetime of the semiconductor module, it undergoes numerous heating and cooling cycles. This could significantly reduce the lifespan of the semiconductor module, as the sintered layer between the substrate and the heat sink may be damaged over time, and the functionality of the semiconductor module may no longer be guaranteed.

[0003] A method and apparatus are needed for forming a stable and reliable permanent connection between a first connecting accessory and a second connecting accessory. Summary of the Invention

[0004] A method includes: applying a pre-layer to a first connector or a second connector; disposing the first connector on the second connector such that the pre-layer is disposed between the first connector and the second connector; heating the first connector, the second connector, and the pre-layer disposed between the first connector and the second connector; and while heating the first connector, the second connector, and the pre-layer, applying pressure to the first connector to press the first connector toward the second connector and form a permanent bonding layer between the first connector and the second connector, wherein applying pressure to the first connector includes: applying a first pressure to at least one first segment of the first connector and applying a second pressure to at least one second segment of the first connector, wherein the second pressure is greater than the first pressure, and the resulting permanent bonding layer has a first porosity in a region disposed below at least one first segment of the first connector and a second porosity in a region disposed below at least one second segment of the first connector, wherein the second porosity is lower than the first porosity.

[0005] An apparatus for forming a permanent connection between two connecting fittings includes a pressing tool comprising an upper punch and a plurality of pressure transmitting elements attached to the upper punch, the plurality of pressure transmitting elements including at least one first type of pressure transmitting element and at least one second type of pressure transmitting element, wherein the upper punch is configured to apply pressure to a first connecting fitting, wherein the plurality of pressure transmitting elements are arranged between the upper punch and the first connecting fitting to press the first connecting fitting onto a second connecting fitting, wherein a pre-layer is arranged between the first connecting fitting and the second connecting fitting, and each first type of pressure transmitting element is configured to transmit a first pressure from the upper punch to a first segment of at least one first segment of the first connecting fitting, and each second type of pressure transmitting element is configured to transmit a second pressure from the upper punch to a second segment of at least one second segment of the first connecting fitting, wherein the second pressure is greater than the first pressure.

[0006] The invention can be better understood by referring to the following figures and description. The components in the figures are not necessarily drawn to scale, but rather the focus is on illustrating the principles of the invention. Furthermore, in the figures, the same reference numerals denote corresponding components in different views. Attached Figure Description

[0007] Figure 1 This is a cross-sectional view of a semiconductor module device.

[0008] Figure 2 This is a cross-sectional view of another semiconductor module device.

[0009] Figure 3 This is a cross-sectional view of the first connecting accessory that is permanently connected to the second connecting accessory.

[0010] Figure 4 A step of a method according to an embodiment of the present disclosure is illustrated schematically.

[0011] Figure 5 This is a cross-sectional view of an apparatus according to an embodiment of the present disclosure.

[0012] Figure 6 This is a cross-sectional view of an apparatus according to another embodiment of the present disclosure. Detailed Implementation

[0013] In the following detailed description, reference is made to the accompanying drawings. The drawings illustrate specific examples in which the invention can be practiced. It should be understood that, unless explicitly stated otherwise, the features and principles described with respect to the various examples can be combined with each other. In the specification and claims, certain elements are designated as "first element," "second element," "third element," etc., and should not be construed as enumerating. Rather, these designations are used only to refer to different "elements." That is, for example, the presence of a "third element" does not necessarily require the presence of "first element" and "second element." The wires or electrical connections described herein may be a single conductive element or may comprise at least two individual conductive elements connected in series and / or parallel. The wires and electrical connections may comprise metallic and / or semiconductor materials and may be permanently conductive (i.e., non-switchable). The semiconductor body described herein may be made of (doped) semiconductor material and may be a semiconductor chip or contained within a semiconductor chip. The semiconductor body has electrically connectable pads and includes at least one semiconductor element with electrodes.

[0014] refer to Figure 1 The diagram shows a cross-sectional view of a conventional semiconductor module device 100. The semiconductor module device 100 includes a housing 7 and a substrate 10. The substrate 10 includes a dielectric insulating layer 11, a (structured) first metallization layer 111 attached to the dielectric insulating layer 11, and a (structured) second metallization layer 112 attached to the dielectric insulating layer 11. The dielectric insulating layer 11 is disposed between the first metallization layer 111 and the second metallization layer 112.

[0015] Each of the first metallization layer 111 and the second metallization layer 112 may be composed of or include one of the following materials: copper; copper alloys; aluminum; aluminum alloys; any other metal or alloy that remains solid during operation of the semiconductor module device. The substrate 10 may be a ceramic substrate, i.e., the dielectric insulating layer 11 is a ceramic substrate (e.g., a thin ceramic layer). The ceramic may be composed of or include one of the following materials: alumina; aluminum nitride; zirconium oxide; silicon nitride; boron nitride; or any other dielectric ceramic. Alternatively, the dielectric insulating layer 11 may be composed of an organic compound and include one or more of the following materials: Al2O3, AlN, ZrO2, SiC, BeO, BN, or Si3N4. For example, the substrate 10 may be, for example, a direct copper bonding (DCB) substrate, a direct aluminum bonding (DAB) substrate, or an active metal bonding (AMB) substrate. Furthermore, the substrate 10 may be an insulating metal substrate (IMS). The insulating metal substrate typically includes a dielectric insulating layer 11, which comprises a (filled) material such as epoxy resin or polyimide. For example, the material of the dielectric insulating layer 11 may be filled with ceramic particles. Such particles may include, for example, SiO2, Al2O3, AlN, SiN, or BN, and may have a diameter between about 1 μm and about 50 μm.

[0016] The substrate 10 is arranged in the housing 7. Figure 1 In the example shown, substrate 10 forms the base surface of housing 7, and housing 7 itself includes only sidewalls and optionally a top or cover. Substrate 10 is attached to heat sink 80 via connection layer 62. For example, connection layer 62 in a conventional semiconductor module 100 may be an electrically insulating adhesive layer, a solder layer, a conductive adhesive layer, or a sintered metal powder (e.g., sintered silver (Ag) powder) layer.

[0017] One or more semiconductor bodies 20 may be disposed on at least one substrate 10. Each semiconductor body 20 disposed on at least one substrate 10 may include a diode, an IGBT (insulated gate bipolar transistor), a MOSFET (metal-oxide-semiconductor field-effect transistor), a JFET (junction field-effect transistor), a HEMT (high electron mobility transistor), or any other suitable semiconductor element.

[0018] One or more semiconductor bodies 20 can be formed on the substrate 10 to create a semiconductor device. Figure 1 In the example shown are only two semiconductor bodies 20. Figure 1 The second metallization layer 112 of the substrate 10 is a continuous layer. In some semiconductor modules 100, the second metallization layer 112 can be a structured layer. Figure 1In the example shown, the first metallization layer 111 is a structured layer. In this context, "structured layer" means that the corresponding metallization layer is not a continuous layer, but rather comprises recesses between different segments of the layer. These recesses... Figure 1 The diagram is schematically shown. In this example, the first metallization layer 111 comprises three distinct segments. Different semiconductor bodies 20 may be mounted to the same or different segments of the first metallization layer 111. The different segments of the first metallization layer 111 may not be electrically connected, or may be electrically connected to one or more other segments using electrical connections 3 (e.g., bonding wires). Semiconductor bodies 20 may be electrically connected to each other or to the first metallization layer 111 using, for example, electrical connections 3. Electrical connections 3 (instead of bonding wires) may also include, for example, bonding tapes, connecting plates, or conductor rails, to name a few. One or more semiconductor bodies 20 may be electrically and mechanically connected to the substrate 10 via a conductive connection layer 60. Such a conductive connection layer 60 may be a solder layer, a conductive adhesive layer, or a sintered metal powder layer (e.g., sintered silver (Ag) powder).

[0019] Figure 1 The illustrated semiconductor module device 100 also includes a terminal element 4. The terminal element 4 provides electrical connection between the interior and exterior of the housing 7. The terminal element 4 can be electrically connected to the first metallization layer 111 via its second end 42, while its first end 41 protrudes outside the housing 7. The terminal element 4 can be electrically contacted from the outside at its first end 41.

[0020] Arranging terminal element 4 at the center of substrate 10 is merely an example. According to other examples, terminal element 4 may be arranged closer to or adjacent to the sidewall of housing 7. The second end 42 of terminal element 4 can be connected via a conductive connection layer (…). Figure 1 Electrical and mechanical connections (not specifically shown) are made to the substrate 10. For example, such a conductive connection layer may be a solder layer, a conductive adhesive layer, or a sintered metal powder (e.g., sintered silver (Ag) powder) layer. Alternatively, the terminal element 4 may also be coupled to the substrate by ultrasonic welding.

[0021] The semiconductor module device 100 may also include an encapsulant 5. For example, the encapsulant 5 may consist of or include cured silicone gel, or it may be a rigid molding compound. The encapsulant 5 may at least partially fill the interior of the housing 7, thereby covering the components and electrical connections disposed on the substrate 10. Terminal elements 4 may be partially embedded in the encapsulant 5. However, at least their first end 41 is not covered by the encapsulant 5 and protrudes from the encapsulant 5 through the housing 7 to the exterior of the housing 7. The encapsulant 5 is configured to protect the components and electrical connections of the power semiconductor module 100, particularly those disposed inside the housing 7, from certain environmental conditions and mechanical damage. The encapsulant 5 is also configured to electrically insulate regions with different potentials (e.g., different sections of the first metallization layer 111) from each other.

[0022] The overall functionality of the semiconductor module 100 typically does not require the second metallization layer 112 of the substrate 10. That is, the second metallization layer 112 generally does not conduct any current during operation of the semiconductor module 100. Therefore, the second metallization layer 112 can usually be omitted entirely. However, in some cases, the second metallization layer 112 may be necessary to allow the substrate 10 to be directly attached to the heat sink 80, for example, using conventional sintering paste or sintering preforms. Heat generated during operation of the semiconductor module device 100 is transferred to the heat sink 80 via the substrate 10 and the interconnect layer 62.

[0023] Now for reference Figure 2 For example, if the encapsulant 5 is a rigid molding compound, then the housing 7 can also be omitted. In this case, the encapsulant 5 can adequately protect the substrate 10 and any components mounted thereon from mechanical damage.

[0024] Now for reference Figure 3 The diagram schematically shows a cross-sectional view of a substrate 10 connected to a heat sink 80 via a connection layer 62. The connection layer 62 can be, for example, a sintered layer. The sintered layer may include sintered metal powder, such as sintered silver (Ag) powder. At least some semiconductor bodies 20 of the semiconductor module device ( Figure 3 The semiconductor body 20 (not specifically illustrated) performs multiple switching operations during the operation of the semiconductor module device 100. For example, when many switching operations are performed within a short period of time, the semiconductor body 20 generates heat. The heat generated during the operation of the semiconductor module device 100 is mainly dissipated from the semiconductor body 20 to the substrate 10, and further dissipated to the heat sink 80 through the interconnect layer 62.

[0025] The sintered interconnect layer 62 deforms upon heating. Typically, during operation of the semiconductor module device 100, some sections of the substrate 10 are heated more than others. For example, regions of the substrate 10 disposed directly beneath the semiconductor body 20 may be heated more than other regions of the substrate 10. The temperature distribution typically depends on the duration of the current flowing through the semiconductor body 20. Due to the uneven heating of the substrate 10, the sintered interconnect layer 62 may also be heated unevenly. The interconnect layer 62 expands unevenly because the temperature in some sections of the substrate 10 (e.g., beneath the semiconductor body 20) is higher than in other sections. In particular, the interconnect layer 62 expands more in regions beneath more heated sections of the substrate 10 than in regions beneath less heated sections of the substrate 10. During the lifetime of the semiconductor module device 100, the semiconductor body 20 is heated and subsequently cooled many times. The cyclic heating and cooling of the semiconductor body 20 and the interconnect layer 62 can lead to mechanical fatigue of the interconnect layer 62, for example, mechanical fatigue originating from the region beneath the semiconductor body 20.

[0026] For this reason, Figure 3 The connecting layer 62 shown includes a first region 62a and a second region 62b. The first region 62a each has a first porosity, and the second region 62b each has a second porosity. The first porosity differs from the second porosity. For example, the first porosity may be higher than the second porosity. The porosity of a material is generally a measure of the void (e.g., “empty”) space in the material and is a fraction of the void volume relative to the total volume between 0 and 1. Porosity can also be given as a percentage between 0 and 100%. The porosity of the first region 62a may, for example, be about 10% or less, about 15% or less, about 20% or less, or about 40% or less. For example, the porosity of the second region 62b may be greater than 10%, greater than 20%, greater than 40%, or greater than 50%. In other words, the second region 62b may be denser than the first region 62a.

[0027] Low porosity (high density) typically provides high mechanical strength and good thermal and electrical conductivity. On the other hand, high porosity (low density) results in low stiffness of the interconnect layer 62, and thus low mechanical stress in the structure comprising the semiconductor body 20, the substrate 10, and the interconnect layer 62.

[0028] A method for generating a connecting layer with regions of different porosities in a simple and effective manner according to embodiments of the present disclosure includes: applying a pre-layer 64 to a first connecting fitting 10 or a second connecting fitting 80; disposing the first connecting fitting 10 on the second connecting fitting 80 such that the pre-layer 64 is disposed between the first connecting fitting 10 and the second connecting fitting 80; and heating the first connecting fitting 10, the second connecting fitting 80, and the pre-layer 64 disposed between the first connecting fitting 10 and the second connecting fitting 80. While heating the first connecting fitting 10, the second connecting fitting 80, and the pre-layer 64, pressure is applied to the first connecting fitting 10 to press the first connecting fitting 10 against the second connecting fitting 80 and form a permanent connecting layer 62 between the first connecting fitting 10 and the second connecting fitting 80. Applying pressure to the first connecting fitting 10 includes: applying a first pressure P1 to at least one first segment of the first connecting fitting 10 and applying a second pressure P2 to at least one second segment of the first connecting fitting 10, wherein the second pressure P2 is greater than the first pressure P1. The resulting permanent bonding layer 62 has a first porosity in a region disposed below at least one first segment of the first bonding fitting 10, and a second porosity in a region disposed below at least one second segment of the first bonding fitting 10, wherein the second porosity is lower than the first porosity.

[0029] Figure 4 A step of a method according to an embodiment of the present disclosure is illustrated schematically. In particular, Figure 4 The diagram schematically illustrates the step of applying pressure to the first connecting fitting 10, thereby pressing the first connecting fitting 10 against the second connecting fitting 80 and forming a permanent bonding layer 62 between the first connecting fitting 10 and the second connecting fitting 80. The first pressure P1 and the second pressure P2 applied to different sections of the first connecting fitting 10... Figure 4 The arrows are represented by arrows of different thicknesses.

[0030] In the example described herein, the first connector is described as a substrate 10 of a semiconductor module device 100, and the second connector is described as a heat sink 80. However, this is merely an example. This method can be used to form permanent connections between any type of connector when a connection layer 62 with regions of different porosities is formed between the respective connectors 10, 80 for any reason. As stated above, a connection layer 62 with regions of different porosities may be advantageous if, during use of the device, the first connector 10 is heated unevenly, and this heat is transferred through the connection layer 62 to the second connector 80, causing the connection layer 62 to also be heated unevenly.

[0031] Applying pressure to the first connector 10 may include applying pressure using a pressing tool. During the step of applying pressure to the first connector 10, the pressing tool may be in direct contact with the first connector 10. For example, if the first connector 10 is a substrate of the semiconductor module 100, the pressing tool may be in direct contact with the substrate 10 (e.g., with the first metallization layer 111), such as... Figure 5 As exemplarily illustrated. During the step of applying pressure to substrate 10, substrate 10 may be unassembled, similar to... Figure 5 As shown in the diagram. That is, no components (e.g., semiconductor body 20, terminal element 4, electrical connector 3, etc.) may be arranged on the substrate 10. However, this is merely an example. It is also generally possible that the substrate 10 is partially or even completely assembled during the step of applying pressure to the substrate 10. However, the housing 7 may not yet be attached to the substrate 10, and the substrate 10 may not yet be covered by the encapsulant 5.

[0032] As mentioned above Figure 2 As mentioned, the substrate 10 can be molded into a rigid molding compound. Generally, the first connector 10 (e.g., the substrate 10) can be disposed in the molded package 5, wherein at least one surface of the first connector 10 (e.g., the lower surface of the second metallization layer 112 facing away from the dielectric insulating layer 11) faces the outside of the molded package 5. That is, at least one surface of the first connector 10 may not be covered by the molded package 5 and may be freely accessible. In this case, during the step of applying pressure to the first connector 10, the pressing tool may come into direct contact with the molded package 5. That is, the pressing tool may apply pressure to the molded package 5, thereby pressing the first connector 10 toward the second connector 80.

[0033] Applying the pre-layer 64 to the first connector 10 or the second connector 80 may include applying a sintering paste layer or a sintered preform to the first connector 10 or the second connector 80. According to some examples, applying the pre-layer 64 to the first connector 10 or the second connector 80 may include applying a sintering paste layer or a sintered preform comprising at least one of copper and silver to the first connector 10 or the second connector 80.

[0034] refer to Figure 5The diagram schematically illustrates an apparatus for forming a permanent connection between two connecting fittings according to an embodiment of the present disclosure. The apparatus includes a pressing tool comprising an upper punch 92 and a plurality of pressure transmitting elements 94 attached to the upper punch 92, the plurality of pressure transmitting elements 94 including at least one first type pressure transmitting element 94a and at least one second type pressure transmitting element 94b. The upper punch 92 is configured to apply pressure to a first connecting fitting 10, wherein the plurality of pressure transmitting elements 94 are arranged between the upper punch 92 and the first connecting fitting 10, thereby pressing the first connecting fitting 10 onto a second connecting fitting 80, wherein a pre-layer 64 is arranged between the first connecting fitting 10 and the second connecting fitting 80. Each first type of pressure transmission element 94a is configured to transmit a first pressure P1 from the upper punch 92 to a first segment of at least one first segment of the first connecting fitting 10, and each second type of pressure transmission element 94b is configured to transmit a second pressure P2 from the upper punch 92 to a second segment of at least one second segment of the first connecting fitting 10, wherein the second pressure P2 is greater than the first pressure P1.

[0035] The pressure transmission element 94 may extend substantially perpendicular to the upper surface of the first connecting fitting 10, wherein the upper surface of the first connecting fitting 10 is the surface facing the pressing tool when pressure is applied to the connecting fittings 10, 80. The lower surface of each pressure transmission element 94 may be flat and is the surface opposite to the upper punch 92.

[0036] The upper punch 92 can apply uniform pressure to the pressure transmission element 94. However, the first type of pressure transmission element 94a and the second type of pressure transmission element 94b can transmit pressure from the upper punch 92 to the first connecting fitting 10 at different transmission ratios. In this way, different amounts of pressure can be applied to different sections of the first connecting fitting 10. This can be achieved in different ways.

[0037] refer to Figure 6 According to some embodiments of this disclosure, a first type of pressure transmission element 94a can be attached to an upper punch 92 via a first type of connecting element 96a, and a second type of pressure transmission element 94b can be attached to an upper punch 92 via a second type of connecting element 96b. The first type of connecting element 96a transmits pressure from the upper punch 92 to the first type of pressure transmission element 94a at a first transmission ratio, and the second type of connecting element 96b transmits pressure from the upper punch 92 to the second type of pressure transmission element 94b at a second transmission ratio different from the first transmission ratio.

[0038] like Figure 5 and Figure 6As schematically shown, the first type of pressure transmission element 94a and the second type of pressure transmission element 94b can have the same cross-sectional area. That is, the first type of pressure transmission element 94a and the second type of pressure transmission element 94b can be identical to each other in terms of their dimensions. The first type of pressure transmission element 94a and the second type of pressure transmission element 94b can also be identical to each other in terms of their manufacturing materials.

[0039] The cross-sectional area of ​​each second-type connecting element 96b can be constant between the upper punch 92 and the corresponding second-type pressure transmitting element 94b. On the other hand, the cross-sectional area of ​​each first-type connecting element 96a can increase from the side facing the upper punch 92 to the opposite side facing the corresponding first-type pressure transmitting element 94a. That is, if the cross-sectional area of ​​the second-type connecting element 96b is equal to the cross-sectional area of ​​the second-type pressure transmitting element 94b, the pressure transferred from the upper punch 92 to the second-type pressure transmitting element 94b can be maximized. However, if the cross-sectional area of ​​each first-type connecting element 96a increases from the side facing the upper punch 92 to the opposite side facing the corresponding first-type pressure transmitting element 94a, the pressure transferred from the upper punch 92 to the first-type pressure transmitting element 94a is lower. The cross-sectional area of ​​the side of the first-type connecting element 96a facing the corresponding first-type pressure transmitting element 94a can be the same as the cross-sectional area of ​​the corresponding first-type pressure transmitting element 94a.

[0040] like Figure 5 and Figure 6 As further shown, the device may also include a lower punch 90. A stack formed by a second connecting fitting 80, a pre-layer 64, and a first connecting fitting 10 may be arranged on the lower punch 90, wherein the second connecting fitting 80 faces the lower punch 90. An upper punch 92 is configured to apply pressure to the lower punch 90, wherein the first connecting fitting 10, the pre-layer 64, and the second connecting fitting 80 are arranged between the upper punch 92 and the lower punch 90. That is, the lower punch 90 forms the counterpart of the upper punch 92.

[0041] During the sintering process, the device can be heated while pressure is applied to the connecting fittings 10, 80 and the pre-layer 64 disposed between the connecting fittings 10, 80. Therefore, according to some embodiments, the device may further include at least one of a first heating unit configured to heat the upper punch 92 and a second heating unit configured to heat the lower punch 90. That is, while pressure is applied through the upper punch 92, the upper punch 92 and / or the lower punch 90 can be heated by the respective heating unit. This heat can be transferred from the upper punch 92 and / or the lower punch 90 to the connecting fittings 10, 80 and the pre-layer 64. However, the connecting fittings 10, 80 and the pre-layer 64 may optionally be heated in any other suitable manner.

Claims

1. A method comprising: Apply the pre-layer (64) to the first connecting fitting (10) or the second connecting fitting (80); The first connecting fitting (10) is arranged on the second connecting fitting (80) such that the pre-layer (64) is arranged between the first connecting fitting (10) and the second connecting fitting (80); Heating the first connecting fitting (10), the second connecting fitting (80), and the pre-layer (64) disposed between the first connecting fitting (10) and the second connecting fitting (80); and While heating the first connecting fitting (10), the second connecting fitting (80), and the pre-layer (64), pressure is applied to the first connecting fitting (10), thereby pressing the first connecting fitting (10) against the second connecting fitting (80), and forming a permanent connection layer (62) between the first connecting fitting (10) and the second connecting fitting (80), wherein Applying pressure to the first connecting fitting (10) includes: applying a first pressure (P1) to at least one first section of the first connecting fitting (10), and applying a second pressure (P2) to at least one second section of the first connecting fitting (10), wherein the second pressure (P2) is greater than the first pressure (P1), and The resulting permanent bonding layer (62) has a first porosity in a region disposed below at least one first segment of the first bonding fitting (10) and a second porosity in a region disposed below at least one second segment of the first bonding fitting (10), wherein the second porosity is lower than the first porosity.

2. The method according to claim 1, wherein, Applying pressure to the first connecting fitting (10) includes applying pressure by pressing a tool.

3. The method of claim 2, wherein, During the step of applying pressure to the first connecting fitting (10), the pressing tool is in direct contact with the first connecting fitting (10).

4. The method of claim 2, wherein, The first connecting fitting (10) is disposed in the molded package (5), wherein at least one surface of the first connecting fitting (10) faces the outside of the molded package (5), and wherein the pressing tool is in direct contact with the molded package (5) during the step of applying pressure to the first connecting fitting (10).

5. The method of any one of claims 1 to 4, wherein, Applying a pre-layer (64) to the first connector (10) or the second connector (80) includes applying a sintering paste layer or a sintering preform to the first connector (10) or the second connector (80).

6. The method of claim 5, wherein, Applying a pre-layer (64) to a first connector (10) or a second connector (80) includes applying a sintered paste layer or sintered preform comprising at least one of copper and silver to the first connector (10) or the second connector (80).

7. An apparatus for forming a permanent connection between two connecting fittings (10, 80), the apparatus comprising a pressing tool, the pressing tool comprising: Upper punch (92); as well as A plurality of pressure transmission elements (94) are attached to the upper punch (92), the plurality of pressure transmission elements (94) including at least one first type pressure transmission element (94a) and at least one second type pressure transmission element (94b), wherein The upper punch (92) is configured to apply pressure to the first connecting fitting (10), wherein the plurality of pressure transmitting elements (94) are arranged between the upper punch (92) and the first connecting fitting (10), thereby pressing the first connecting fitting (10) onto the second connecting fitting (80), wherein a pre-layer (64) is arranged between the first connecting fitting (10) and the second connecting fitting (80), and Each of the first type of pressure transmission elements (94a) is configured to transmit a first pressure (P1) from the upper punch (92) to a first segment of at least one first segment of the first connecting fitting (10), and each of the second type of pressure transmission elements (94b) is configured to transmit a second pressure (P2) from the upper punch (92) to a second segment of at least one second segment of the first connecting fitting (10), wherein the second pressure (P2) is greater than the first pressure (P1).

8. The apparatus according to claim 7, wherein The first type of pressure transmission element (94a) is attached to the upper punch (92) via a first type of connecting element (96a). The second type of pressure transmission element (94b) is attached to the upper punch (92) via a second type of connecting element (96b). The first type of connecting element (96a) transmits pressure from the upper punch (92) to the first type of pressure transmitting element (94a) at a first transmission ratio, and The second type of connecting element (96b) transmits pressure from the upper punch (92) to the second type of pressure transmitting element (94b) at a second transmission ratio different from the first transmission ratio.

9. The apparatus of claim 8, wherein, The first type of pressure transmission element (94a) and the second type of pressure transmission element (94b) have the same cross-sectional area.

10. The apparatus according to claim 9, wherein The cross-sectional area of ​​each of the second type of connecting elements (96b) is constant between the upper punch (92) and the corresponding second type of pressure transmitting element (94b), and The cross-sectional area of ​​each of the first type of connecting elements (96a) increases from the side facing the upper punch (92) to the opposite side facing the corresponding first type of pressure transmitting element (94a).

11. The apparatus of any one of claims 7 to 10, further comprising a lower punch (90), wherein, The upper punch (92) is configured to apply pressure to the lower punch (90), wherein the first connecting fitting (10), the pre-layer (64) and the second connecting fitting (80) are arranged between the upper punch (92) and the lower punch (90).

12. The apparatus according to any one of claims 7 to 11, further comprising at least one of the following: A first heating unit, configured to heat the upper punch (92); and a second heating unit configured to heat the lower punch (90).

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