DBC substrate, in particular ceramic DBC substrate of a power module

Abstract

The invention relates to a DBC substrate (20), in particular a ceramic DBC substrate (20) of a power module (10) provided at least partially with a mold material (18), wherein the DBC substrate (20) has at least one exposed region (28) for external contacting. On the DBC substrate (20), interspaces (54) between adjacent Cu conductor tracks (22) at least within the at least one exposed region (28) are covered by the mold material (18) in a covering thickness (46). The invention furthermore relates to a method for producing a DBC substrate (20) having at least one region exposed on the DBC substrate (20), and to the use of the DBC substrate (20) in power modules for controlling inverters of electric drives of vehicles.

Description

[0001] R.415300

[0002] - 1 -

[0003] Description

[0004] title

[0005] DBC substrate, in particular ceramic DBC substrate of a power module

[0006] Technical field

[0007] The invention relates to a DBC substrate, in particular a ceramic DBC substrate of a power module at least partially provided with a molding material, wherein the DBC substrate has at least one exposed area for external contacting. Furthermore, the invention relates to a method for producing a DBC substrate with at least one exposed area on the DBC substrate and to the use of the DBC substrate in power modules of inverters on electric drives of vehicles.

[0008] State of the art

[0009] From DE 10 2022 206 265 A1, a power module is known with a first circuit carrier having an electrically insulating layer on which at least one first conductor structure, at least one second conductor structure, and at least one third conductor structure are formed, wherein at least one first semiconductor switch is electrically connected between the at least one first conductor structure and the at least one third conductor structure, wherein at least one second semiconductor switch is electrically connected between the at least one third conductor structure and the at least one second conductor structure, and wherein at least one second circuit carrier is arranged spatially parallel above the first circuit carrier and has at least one internal contact area and at least one external contact area. The layout of the first circuit carrier is mirror-symmetrical about a central longitudinal axis.The second circuit carrier is designed as a rectangular and, in particular, flexible printed circuit board, which is symmetrical to the central longitudinal axis R.415300.

[0010] - 2 - is arranged and is connected to the first circuit carrier via soldered connections, welded connections, adhesive connections or sintered connections.

[0011] DE 10 2014 219 998 B4 discloses a power module, in particular for providing a phase current for an electric motor. The power module comprises a circuit carrier with a surface, at least two first contact surfaces on the surface, and at least two first power transistors, each having a ground contact surface. Each of the at least two first power transistors is directly arranged on one of the first contact surfaces and electrically connected to the respective first contact surface via its ground contact surface. The power module also comprises a second contact surface on the surface and at least two second power transistors, each having a ground contact surface.The at least two second power transistors are arranged directly on the second contact surface and are electrically connected to the second contact surface via their respective base contact surfaces. Furthermore, the power module comprises at least two third contact surfaces on its surface, wherein the at least two second power transistors each have an additional contact surface on their side facing away from the surface of the circuit carrier, and each second power transistor of the at least two second power transistors is electrically connected to one of the at least two third contact surfaces via its additional contact surface.

[0012] The at least two first contact surfaces and the at least two third contact surfaces are arranged alternately in a longitudinal direction of the power module, with the second contact surface being located next to the at least two first contact surfaces and the at least two third contact surfaces. The second contact surface has at least two contact areas, with each of the at least two contact areas being located next to one of the at least two first power transistors. The at least two first power transistors each have an additional contact surface on their sides facing away from the surface of the circuit carrier, and each first power transistor of the at least two first power transistors is connected via its additional contact surface to the one located next to it.

[0013] - 3 - The contact area of ​​the at least two contact areas of the second contact surface is electrically connected. The at least two contact areas of the second contact surface and the at least two second power transistors are arranged alternately one after the other in the longitudinal direction.

[0014] EP 2 418 925 B1 relates to an electrical contact between a flexible film having at least one conductor track and at least one electrical contact of a sensor or control unit. In this case, an end section of the flexible film is electrically contacted at a contact point by means of heat input, wherein the end section of the flexible film at the contact point is aligned with the electrical contacts formed above. The end section of the flexible film is designed as a corrugation, in particular as a deflection.

[0015] In DBC ceramics, particularly Al₂O₃, vertical cracks appear through the ceramic during operation due to temperature changes. These cracks extend within the laser-cut mold areas necessary for external contacts and occur after passive temperature cycling, especially from -40 °C to +125 °C. They lead to reduced insulation between the top and bottom BBC copper conductors with differing electrical potentials. This can result in product failure and even adverse consequences for passengers. The cause of these vertical cracks is the prior initiation of subcritical, i.e., slow, crack growth within the DBC ceramic at locations subjected to tensile stress. These tensile stress locations are at the ends of each copper conductor, which are characterized by differing coefficients of thermal expansion (CTE) between the copper and the ceramic.Stress corrosion cracking occurs at the ends of the copper / ceramic interfaces where the DBC ceramic is exposed to air. Humidity combined with the high tensile residual stresses described above leads to stress corrosion cracking. This results in minute conchoidal cracks in the micrometer range, which propagate into the ceramic even though the ceramic is stressed far below its flexural or tensile strength. As the conchoidal crack length increases due to propagation, the ceramic in the DBC substrate is weakened, and its mechanical strength decreases. If the conchoidal crack length reaches a critical value, a fracture occurs in the force-controlled system due to the system module cooler during temperature changes, extending through the entire thickness of the ceramic, which can be several hundred millimeters. (See R.415300.)

[0016] - 4 -

[0017] In system module coolers, the coefficient of thermal expansion (CTE) of the cooler is higher compared to a negatively curved system at low temperatures.

[0018] Disclosure of the invention

[0019] According to the invention, a DBC substrate is proposed, in particular a ceramic DBC substrate of a power module at least partially provided with a molding material, wherein the DBC substrate has at least one exposed area for external contacting. On the DBC substrate, the spaces between adjacent Cu conductor tracks, at least within the at least one exposed area, are covered by the molding material to a certain thickness.

[0020] The solution proposed according to the invention advantageously achieves a significant reduction in the stress in the ceramic of the DBC substrate and a significant reduction in its load-bearing capacity by reducing the moisture load.

[0021] In an advantageous embodiment of the DBC substrate proposed according to the invention, the covering thickness of the mold material is designed to be in the single-digit micrometer range.

[0022] In a second advantageous embodiment of the DBC substrate proposed according to the invention, the covering thickness of the mold material is designed such that it corresponds to at least 50% of the height of the adjacent Cu conductor tracks.

[0023] In a further advantageous embodiment of the DBC substrate according to the invention, the covering thickness of the mold material corresponds to at least one height of the copper conductor tracks. In this embodiment, the copper conductor tracks are completely embedded in the mold material.

[0024] Finally, in a further advantageous embodiment of the DBC substrate according to the invention, it is proposed that the mold material forms mold ridges or raised mold ridges in the spaces between, which bridge the at least one exposed area. The height of the mold ridges is described as R.415300.

[0025] - 5 -

[0026] Bridges formed from mold material, such as raised bridges or raised mold bridges, can advantageously fill the gaps between adjacent Cu conductor tracks in such a way that an even greater reduction of the stress level can be achieved.

[0027] In a further embodiment of the DBC substrate proposed according to the invention, to reduce the stresses in the ceramic of the DBC substrate and to reduce the moisture load on the outside of the DBC substrate, Cu conductor tracks running on the outside of the DBC substrate are designed in a stepped structure, with first and second steps extending in the longitudinal direction of the Cu conductor tracks and opposite each other.

[0028] Advantageously, in this embodiment of the DBC substrate, the length of the step structure of the Cu conductor tracks is designed such that it corresponds at least to the width of a mold cavity or the width of the area opened by laser for contacting the Cu conductor tracks in the molding material.

[0029] Furthermore, in this embodiment of the DBC substrate proposed according to the invention, it is advantageously possible to provide the spaces on the outside of the DBC substrate between the conductor tracks with a protective covering. This protective covering can, for example, be a protective cover made of silicone gel, a filler material, or an epoxy-based material. In principle, the stepped structure can also be combined with the conventional molding process and the aforementioned mold bridge method.

[0030] Furthermore, the invention relates to a method for producing a DBC substrate with at least one exposed area on the DBC substrate.

[0031] In an alternative version of the proposed method, a) a laser deflash process is applied in situ to the DBC substrate using an automated optical inspection system, with the laser application running to control the laser, or b) in a method alternative, R.415300 is applied within a mold cavity.

[0032] - 6 - of the molding material at least one translationally movable, spring-loaded, stamp-shaped additional cavity of the DBC substrate is pressed, with excess molding material subsequently being removed by laser.

[0033] In an advantageous embodiment of the method according to process step b), the stamp-shaped cavity is preferably PTFE-coated and furthermore provided with sharp edges, so that the outer edge penetrating the DBC substrate within a micrometer range is sealed.

[0034] Furthermore, the invention relates to the use of the DBC substrate in power modules of inverters on electric drives of vehicles, whether passenger vehicles or commercial vehicles.

[0035] Advantages of the invention

[0036] The solution proposed according to the invention advantageously enables a significant reduction in both stress and moisture load at highly stressed locations within the copper-conducting DBC substrates. This is achieved primarily by covering the spaces between adjacent copper conductors with mold material using a laser deflash process. This allows for the creation of a residual mold material covering on the top or outer surface of the ceramic DBC substrate between the copper conductors. The greater the mold material covering thickness over the ceramic (for example, the Al₂O₃ of the DBC substrate), the lower the resulting stress.Similarly, moisture ingress is reduced due to the negligible diffusion of water molecules through the mold material, thus drastically reducing stress corrosion cracking. As a result, conchoidal cracking no longer occurs, and vertical crack propagation within the ceramic material of the DBC substrate is prevented, thereby preventing electrical failure of the module or the entire inverter. Furthermore, consequential defects caused by ceramic cracks due to the resulting lower effective flexural stiffness, such as cracking in the mold body and further subsequent damage, can be avoided. R.415300.

[0037] - 7 -

[0038] By applying a laser deflash process to the DBC substrate and using an automated optical inspection (AOI) system, precise control of the laser position and the mold material coverage thickness described above can be achieved in situ during the laser process. A significant initial reduction in stress levels and moisture ingress into the DBC substrate can be achieved with a minimum mold material coverage in the single-digit micrometer range. Increasing the coverage thickness, for example to 50% of the thickness or height of adjacent copper conductor tracks, allows for a further reduction in stress levels and moisture ingress into the ceramic material of the DBC substrate.The coating thickness of the mold material can also be created by forming mold ridges between adjacent copper conductor tracks within the spaces between them, with a height corresponding to the height of the copper conductor tracks. Alternatively, raised mold ridges can be created in the spaces between the copper conductor tracks, bridging the exposed area within the mold cavity along its width.

[0039] In another embodiment of the DBC substrate proposed according to the invention, the copper conductor tracks on the upper surface of the DBC substrate can be provided with a stepped structure formed by opposing first and second steps extending parallel to each other in the longitudinal direction. In this embodiment of the DBC substrate as well, a significant reduction in the stress level can be achieved without covering the spaces with mold material.

[0040] In another process variant, translationally movable, spring-loaded additional cavities with a stamp-like appearance can be used within the mold cavity. These can be pressed directly onto the top surface of the DBC substrate before or during the molding process, allowing any small remnants of the mold material remaining on the copper material to be subsequently removed by laser. Sealing such additional cavities, also known as "moving inserts," can be achieved, for example, using a PTF E-coated stamp or sharp stamp edges during the molding process. R.415300

[0041] - 8 -

[0042] Brief description of the drawings

[0043] Embodiments of the invention are explained in more detail with reference to the drawings and the following description.

[0044] They show:

[0045] Figure 1 shows a section through a power module mounted on a cooler with an exposed area on the outside of the DBC substrate.

[0046] Figure 2 shows a perspective top view of the mold material with exposed areas within it.

[0047] Figure 3 shows the section depicted in Figure 2 in an enlarged perspective top view.

[0048] Figure 4 shows a top view of a first embodiment variant with remaining mold coverage after the laser deflash process.

[0049] Figure 5 shows the section depicted in Figure 4 on an enlarged scale.

[0050] Figure 6 shows a further, second embodiment of the mold covering of gaps between adjacent Cu conductor tracks proposed according to the invention.

[0051] Figure 7 shows a further, third embodiment variant with mold ribs running in the spaces between adjacent conductor tracks corresponding to the height of the Cu conductor tracks,

[0052] Figure 8 shows a further, fourth embodiment of the mold covering with bridge-like mold ribs, higher than the Cu conductor tracks at the height level of the mold cavity,

[0053] Figure 9 shows a further, fifth embodiment of the DBC conductor structure with Cu conductor tracks having a step structure extending in the longitudinal direction of the same, R.415300

[0054] - 9 -

[0055] Figure 10 is a perspective, enlarged view of the representation according to Figure 9.

[0056] Figure 11 shows a top view of the Cu conductor tracks without the mold material, wherein the Cu conductor tracks are formed with step structures,

[0057] Figure 12 shows a representation of the stress conditions in a space between adjacent Cu conductor tracks with missing mold covering on the DBC substrate.

[0058] Figure 13 shows a mold material applied in the space between adjacent Cu conductor tracks with minimal overlap thickness,

[0059] Figure 14 shows a schematic representation of the resulting voltage profiles in the case where the mold material is introduced into the space between adjacent Cu conductor tracks to approximately 50% of the height of the adjacent Cu conductor tracks and

[0060] Figure 15 shows a space between adjacent Cu conductor tracks completely filled with mold material, with the resulting voltage level schematically indicated.

[0061] Embodiments of the invention

[0062] In the following description of embodiments of the invention, identical or similar elements are designated by the same reference numerals, and repeated descriptions of these elements are omitted in individual cases. The figures represent the subject matter of the invention only schematically.

[0063] Figure 1 schematically depicts a power module 10 comprising an AMB substrate 12. The AMB substrate 12 (Active Metal Brazing) is a composite of copper and ceramic material, for example, a material combination of Ti / Cu or Ti / Ag.

[0064] The power module 10 is mounted on a connection surface 16 of a cooler 14. The power module 10, or rather the AMB substrate 12 and R.415300

[0065] - 10 - A DBC substrate 20 (Direct Bonded Copper) arranged above it is at least partially enclosed by a mold material 18. A number of copper conductor tracks 22 extend within the mold material 18, or on both sides of the DBC substrate 20. The DBC substrate 20 is formed as a ceramic layer 24, for example, as AbOa ceramic 26. At least one exposed area 28 is located on an outer surface 40 of the DBC substrate 20, which is exposed to environmental influences such as temperature or humidity. The at least one exposed area 28 can also be located on a surface other than the outer surface 40 of the DBC substrate 20.

[0066] The representation in Figure 1 further shows that the structure of the power module 10, shown schematically here, also includes an alloy 42 (reference numeral 30) which is arranged above a silicon carbon layer 32. Below this is a SialXk layer 34. Furthermore, the layer structure of the power module 10, shown schematically in section here, includes a cooling solder 36 and cold gas-sprayed Cu 38.

[0067] The mold material 18, for example, is an epoxy-based thermoset with filler particles for packaging power modules 10 using a molding process, in particular a transfer molding process. The DBC substrates 20 shown in Figure 1 can also be, for example, metal / ceramic / metal compounds, such as AMB substrates 12.

[0068] Figures 2 and 3 show a perspective view of a power module 10 with exposed copper conductor tracks 22 within exposed areas 28. The mold material 18, comprising several exposed areas 28, is located on the top surface of the power module 10. The cooler 14, including the connection surface 16, is located on the underside of the power module 10, as shown in the perspective view in Figure 2. The section shown with reference numeral 50 in Figure 2 is enlarged and highlighted in Figure 3.

[0069] Figure 3 shows that within the exposed area 28 shown here in a perspective top view, a number of copper conductor tracks 22 run, for example on an outer surface 40 of the DBC substrate 20, forming gaps 54. The further paths of the conductor tracks 22 are not shown in Figure 3.

[0070] - 11 - shown, since they are covered on both sides by the mold material 18. The exposed area 28 represents a mold cavity 68, a height level of a first laser process is designated by reference numeral 52 in the representation according to Figure 3. The spaces 54 between the adjacent Cu conductor tracks 22, which are formed with a thickness 62, are formed here, for example, by the outer surface 40 of the ceramic layer 24, for example an AbOa ceramic 26.

[0071] Based on the representations in Figures 2 and 3, Figure 4 shows a power module 10 obtained after a laser de-flash or laser ablation process. The section 50 in Figure 4 is shown enlarged in Figure 5. In this first embodiment according to the invention, the gaps 54 between adjacent copper conductor tracks 22, which are still exposed in Figure 3 and have a thickness 62, are covered by a layer of mold material 18 with a covering thickness 46. This means that, for example, the outer surface 40 of the DBC substrate 20 is no longer directly exposed to environmental influences such as humidity and temperature. As shown in Figure 5, the covering thickness 46 of the gaps 54 between adjacent copper conductor tracks 22 can be formed with a minimum thickness 42 of only a few micrometers.However, to further improve the protection of, for example, the outer surface 40 of the DBC substrate 20, or to reduce the stress level and the moisture load, the covering thickness 46 of the mold material 18 can be increased so that it reaches, for example, 50% of the height or thickness 62 of the copper conductor tracks 22. The spaces 54 can therefore be filled with mold material 18 at a variable mold height 58 with respect to the covering thickness 46. A constant mold height 60, which either corresponds to the minimum thickness 42 or can be greater, can be used.

[0072] Figure 6 shows a further, second embodiment of the solution proposed according to the invention, in which the free spaces 54 are formed with a covering thickness 46, which can, for example, correspond to a constant mold height 60 of the filled mold material 18, such as 50% or more of the height or thickness 62 of the Cu conductor tracks 22. The constant mold height 60 can also be selected such that the top surfaces of the Cu conductor tracks 22 and the top surfaces of the bridge-like fillings made of mold material R.415300

[0073] - 12 -

[0074] 18 of the spaces between 54 adjacent Cu conductor tracks 22 form a flat surface.

[0075] The variant shown in Figure 6 is analogous to the first embodiment shown in Figure 5, except for the thickness of the mold material 18 covering the surface. Such mold covering and the maintenance or adjustment of the covering thickness 46 can be achieved, for example, by a laser deflash process performed only on the copper of the DBC substrate 20. The process is carried out in situ during the laser process using an automated optical inspection system with respect to laser control. Alternatively, the covering thickness 46 of the mold material 18 covering can be achieved using a moving insert. This refers to a spring-loaded, translationally movable additional cavity within the large mold cavity 68.This can be, in particular, a stamp that is pressed directly onto the copper of the DBC substrate 20 before or during the molding process. This allows any small remnants of the mold material 18 that may be present on the copper to be subsequently removed by laser. The sealing of the stamp-shaped moving insert can be achieved, for example, by means of a Teflon-coated stamp or by means of sharp stamp edges that are pressed into the copper of the DBC substrate 20 in the micrometer range, thus enabling a seal during the molding process.

[0076] As can be seen from the illustration in Figure 7, in comparison to the embodiment shown in Figure 6, in this embodiment the covering thickness 46 of the mold material 18 projects beyond the upper surface of the adjacent copper conductor tracks 22 and is formed between the adjacent copper conductor tracks 22, thus forming a raised mold height 64. This results in mold ridges 66 whose height exceeds the height of the adjacent surfaces of the copper conductor tracks 22.

[0077] The illustration in Figure 8 shows raised mold ridges 70, which extend essentially across the width of the mold cavity 68. The height of the raised mold ridges 70 corresponds essentially to the height level of the mold cavity 68. This height level is higher than the height level 52, which results after a first laser cutting. The height of the raised mold ridges 70 is shown in Figure 8.

[0078] - 13 -

[0079] The webs 70, as shown in Figure 8, are further raised compared to the raised mold height 64, as shown in Figure 7 in relation to the mold webs 66. This allows the stress, for example within the Al₂O₃ ceramic 26 of the DBC substrate 20, to be significantly reduced. In this embodiment, the laser process takes place only in the areas of the Cu conductor tracks 22, i.e., in the areas of the contact rails of a flexible film yet to be applied.

[0080] The illustration according to Figures 9, 10 and 11 shows a further embodiment of the solution proposed according to the invention for reducing the stress level in the ceramic of the DBC substrate 20 and for reducing the moisture load.

[0081] According to the embodiment shown in Figures 9, 10, and 11, copper conductor tracks 22 with a stepped structure 72 are applied, for example, to the outer surface 40 – other areas are also possible – of the DBC substrate 20, which is in particular an Al₂O₃ ceramic 26. The stepped structure 72 of the individual, adjacent copper conductor tracks 22 is characterized by parallel first and second steps 74, 76. These are located opposite each other along the first and second edges 86, 88 of each individual copper conductor track 22. As can be seen from the illustration in Figure 9, the stepped structure 72 is implemented with a length 78 on each copper conductor track 22. The representations according to Figures 9, 10 and 11 show that the individual spaces 54 formed between the Cu conductor tracks 22 on the outside 40 of the DBC substrate 20 are free of mold material 18.The stepped structure 72 of the Cu conductor tracks 22 allows for a significantly reduced stress at the described stress singularity in the DBC substrate 20, thus eliminating the need to fill the spaces 54 between the Cu conductor tracks 22 with mold material 18. Substrates with stepped structures 72, such as "Endurance Substrate" from Rogers Corp. (https: / / www.rogerscorp.com / advanced-electronics-solutions / curamik-ceramic-substrates / curamik-endurance), can be used. This stepped structure 72 does not need to be present along the entire length of the Cu conductor tracks 22, but only locally in the laser-treated area where it is required. This can be seen from the illustrations in Figures 10 and 11, where in Figure 11 the mold material 18 covering the Cu conductor tracks 22, which limits the mold cavity 68, R.415300.

[0082] - 14 - is omitted. Figure 11 shows that the stepped structure 72 along the copper conductor tracks 22 is only partially formed and that only in the areas of the copper conductor tracks 22 located within the mold cavity 68 are the first and second steps 74, 76, running parallel to each other, formed by the stepped structure 72, located in the adjacent copper conductor tracks 22. In Figures 10 and 11, reference numeral 78 denotes the length of the stepped structure 72. The length 78 of the stepped structure 72 corresponds essentially to the width of the mold cavity 68 in the mold material 18. Reference numeral 80 in Figure 11 shows the further course of the copper conductor tracks 22 outside the spaces 54 in those areas that are covered by the mold material 18 in the representation according to Figure 10.

[0083] In another embodiment, the aforementioned stepped structure 72 can be formed along the copper conductor tracks 22, and additional mold material 18 can be introduced between the copper conductor tracks 22 to further enhance the system's robustness. It is also possible to provide an additional protective covering 82 in each of the embodiments described above, which could be, for example, a silicone gel 84 or an epoxy-based material 84. These additional protective coverings 82 can be applied to the DBC substrate 20 after the welding process of a flexible film to reduce stress corrosion cracking by decreasing the moisture load on the outer surface 40 of the exposed A Oa ceramic 26.

[0084] Various embodiments of the solution proposed according to the invention can be seen in Figures 12 to 15. Figure 12 shows an embodiment in which the gap 54 on the outer surface 40 of the DBC substrate 20 is free of mold material 18. The gap 54 has a height 90, extending from the top surface of the copper conductors 22, here to the outer surface 40 of the DBC substrate 20. The opposing edges of the copper conductors 22 are designated by reference numerals 86 and 88. The copper conductors 22 contact the outer surface 40 with their end regions 92, for example; these are the most stressed positions 44 with respect to the connection between the copper conductors 22 on the one hand and the outer surface 40 of the DBC substrate 20 on the other. R.415300

[0085] - 15 -

[0086] Figure 13 shows that in this embodiment, the mold material 18 is applied to the outer surface 40 of the DBC substrate 20 with a coverage thickness 46. The coverage thickness 46 shown in Figure 13 corresponds to a minimum thickness 42 of the mold material 18, which is within the single-digit micrometer range. This coverage, applied to the outer surface 40 with a minimum thickness 42 of the coverage thickness 46, already results in a stress reduction of more than 30% at the most stressed positions 44 on the underside of the copper conductor tracks 22.

[0087] In the representation according to Figure 14, the coating thickness 46 of the DBC substrate 20 is formed in a constant mold height 60 of approximately 150 pm, which corresponds essentially to half the height 48 of the Cu conductor tracks 22. In this embodiment, a stress reduction of almost 40% can be achieved at the most stressed positions 44.

[0088] For the sake of completeness, it should be mentioned that the space 54 is essentially half filled with mold material 18 between the opposing edges 86, 88 of the adjacent Cu conductor tracks 22.

[0089] Finally, Figure 15 shows an embodiment in which the space 54 between adjacent copper conductor tracks 22, i.e., between the first edge 86 and the second edge 88, is completely filled with mold material 18. Here, the covering thickness 46 corresponds to a thickness 62 in which the copper conductor tracks 22 are formed. In this embodiment, a stress reduction of more than 50% can be achieved at the most stressed positions 44 on the underside of the copper conductor tracks 22 and the outer surface 40 of the DBC substrate 20. The covering thickness 46, i.e., the mold height, corresponds to approximately 300 pm and is identical to the thickness 62 of the Cu conductor tracks 22. In the embodiment according to Figure 15, the top surfaces of the adjacent Cu conductor tracks 22 and the top surface of the mold material 18 filling the space 54 form a continuous plane.

[0090] Reference numeral 92 designates the end regions of the copper conductor tracks 22 on the outer surface 40 of the DBC substrate 20. Electrical contact areas 94 are located here. R.415300

[0091] - 16 -

[0092] The invention is not limited to the embodiments described here and the aspects highlighted therein. Rather, within the scope specified by the claims, a multitude of modifications are possible that fall within the bounds of what is considered skilled in the art.

Claims

R.415300 - 17 - Claims 1. DBC substrate (20), in particular ceramic DBC substrate (20), of a power module (10) at least partially provided with a mold material (18), wherein the DBC substrate (20) has at least one exposed area (28) for external contacting, characterized in that on the DBC substrate (20) spaces (54) of adjacent Cu conductor tracks (22) are covered by the mold material (18) in a covering thickness (46) at least within the at least one exposed area (28).

2. DBC substrate (20) according to claim 1 , characterized in that the covering thickness (46) of the mold material (18) is designed to have a minimum thickness (42) in the single-digit micrometer range.

3. DBC substrate (20) according to claim 1 , characterized in that the covering thickness (46) of the mold material (18) corresponds to at least 50% of a height (48) of the Cu conductor tracks (22).

4. DBC substrate (20) according to claim 1 , characterized in that the covering thickness (46) of the mold material (18) corresponds at least to the height (48) of the Cu conductor track (22).

5. DBC substrate (20) according to claims 1 and 4, characterized in that the mold material (18) forms mold ribs (66) or raised mold ribs (70) in the spaces (54) which bridge the at least one exposed area (28).

6. DBC substrate (20), in particular a ceramic DBC substrate (20) of a power module (10) partially provided with a mold material (18), wherein the DBC substrate (20) has at least one exposed area (28), characterized in that Cu conductor tracks (22) running on the DBC substrate (20) are arranged in a stepped structure (72) R.415300 - 18 - are guided, with first and second steps (74, 76) extending in the longitudinal direction of the Cu conductor tracks (22), opposite each other, and designed in a stepped manner.

7. DBC substrate (20) according to the preceding claim, characterized in that a length (78) of the step structure (72) of the Cu conductor tracks (22) corresponds to at least a width of a mold cavity (68) or a width of the area opened by laser for contacting the Cu conductor tracks (22) in the mold material (18).

8. DBC substrate (20) according to claims 6 and 7, characterized in that the spaces (54) on an outer side (40) of the DBC substrate (20) between the conductor tracks (22) are provided with a protective cover (82).

9. DBC substrate (20) according to claims 6 to 8, characterized in that the protective cover (82) is designed as a silicone gel or as a filler material or as an epoxy-based material (84).

10. Method for producing a DBC substrate (20) according to claims 1 to 9, with at least one exposed area (28) on the DBC substrate (20), characterized in that either a) a laser deflash process or laser ablation process is used in situ on the DBC substrate (20) by means of an automatic optical inspection system (AOI) during the laser application to control the laser, or b) at least one translationally movable, spring-loaded, stack-shaped additional cavity is pressed onto the DBC substrate (20) within a mold cavity (68) of the mold material (18), wherein the mold material (18) is subsequently removed by laser.

11. Method according to claim 10, characterized in that according to method step b) the stamp-shaped cavity is PTF E-coated and is sealed by means of sharp outer edges which are pressed into the DBC substrate (20) in the micrometer range. R.415300 - 19 - 12. Use of the DBC substrate (20) according to claims 1 to 5 or 6 to 9 in power modules (10) of inverters on electric drives of vehicles.

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