Method for manufacturing a base plate for a semiconductor module

Abstract

A method for forming multiple spacers on a base plate according to embodiments of the disclosure comprises: attaching a base plate for a semiconductor module to a lateral side of a rotatable disk, wherein a first surface of the base plate faces away from the rotatable disk; directing an outlet of a spray gun towards a first edge of the first surface of the base plate; attaching a spacer mask to the rotatable disk and / or to the base plate, such that the spacer mask is adjacent to the first surface of the base plate and between the base plate and the spray gun, wherein the spacer mask has multiple openings, the size and shape of each opening of the multiple openings corresponding to the size and shape of a spacer to be formed on the base plate.The rotating of the rotatable disc with the base plate and the spacer mask attached to it at a constant rotational speed in a horizontal direction, so that the base plate and the spacer mask repeatedly pass the outlet of the spray gun, and the spraying of particles of a first material onto the spacer mask and the sections of the first surface of the base plate visible through the openings in the spacer mask through the outlet of the spray gun, while the spray gun is moved in a vertical direction from the first edge to an opposite second edge of the first surface of the base plate, the spray gun being moved at a constant speed from the first edge to the opposite second edge of the first surface of the base plate.

Description

TECHNICAL AREA

[0001] This disclosure relates to a method for manufacturing a base plate for a semiconductor module, in particular for manufacturing a base plate with several spacers arranged on it. BACKGROUND

[0002] Document EP 3 958 302 A1 discloses a base plate for a semiconductor module having at least one raised section. The at least one raised section is integrally formed with the base plate. The base plate has a uniform first thickness or a thickness that decreases continuously from the edge regions towards the center, which is locally increased in the area of ​​each of the at least one raised section up to a maximum second thickness.

[0003] Power semiconductor module assemblies often contain a base plate within a package. At least one substrate is mounted on the base plate. A semiconductor assembly with multiple controllable semiconductor devices (e.g., two IGBTs in a half-bridge configuration) is mounted on each of the at least one substrate. Each substrate typically has a substrate layer (e.g., a ceramic layer), a first metallization layer applied to one side of the substrate layer, and a second metallization layer applied to the other side of the substrate layer. The controllable semiconductor devices are mounted, for example, on the first metallization layer. The second metallization layer is typically attached to the base plate by means of a solder or sintered layer. When mounting a substrate on a base plate, e.g.,In soldering or sintering techniques, the substrate is pressed onto the base plate with a certain degree of force. This force can range from very low forces, such as those exerted by gravity in pressureless soldering, to very high pressing forces, such as those required for many forms of sintering or diffusion brazing. To prevent a bonding layer (e.g., solder layer or sintered layer) between the substrate and the base plate from becoming too thin, several spacers can be placed on the base plate and between the base plate and the substrate. The spacers ensure that the thickness of the bonding layer is always at least equal to the height of the spacers. The spacers can generally be separate elements or can be formed integrally with the base plate.

[0004] There is a need for a fast and cost-effective method for manufacturing a base plate with spacers arranged on it. OVERVIEW

[0005] A method for forming multiple spacers on a base plate according to embodiments of the disclosure includes attaching a base plate for a semiconductor module to a lateral side of a rotatable disk, wherein a first surface of the base plate faces away from the rotatable disk, directing an outlet of a spray gun towards a first edge of the first surface of the base plate, attaching a spacer mask to the rotatable disk and / or to the base plate such that the spacer mask is arranged adjacent to the first surface of the base plate and between the base plate and the spray gun, wherein the spacer mask contains multiple openings, the size and shape of each opening of the multiple openings corresponding to the size and shape of a spacer to be formed on the base plate.The rotating of the rotatable disc with the base plate and the spacer mask attached to it at a constant rotational speed in a horizontal direction, so that the base plate and the spacer mask repeatedly pass the outlet of the spray gun, and the spraying of particles of a first material onto the spacer mask and the sections of the first surface of the base plate visible through the openings in the spacer mask through the outlet of the spray gun, while the spray gun is moved in a vertical direction from the first edge to an opposite second edge of the first surface of the base plate, the spray gun being moved at a constant speed from the first edge to the opposite second edge of the first surface of the base plate.

[0006] A method for forming a plurality of spacers on a base plate according to further embodiments of the disclosure includes attaching a base plate for a semiconductor module to a lateral side of a rotatable disk, wherein a first surface of the base plate faces away from the rotatable disk, directing an outlet of a spray gun towards a first edge of the first surface of the base plate, rotating the rotatable disk with the base plate attached thereto at a constant rotational speed in a horizontal direction such that the first surface of the base plate repeatedly passes the outlet of the spray gun, and spraying particles of a first material onto the first surface of the base plate through the outlet of the spray gun, wherein several holding positions are defined between the first edge and an opposite second edge of the first surface of the base plate.The spray gun moves successively from one holding position to the next, pausing at each holding position for a defined duration, and features the spraying of particles of a first material onto the first surface of the base plate through the outlet of the spray gun, while the spray gun pauses at each of the multiple holding positions.

[0007] The invention can be better understood with reference to the following drawings and description. The components in the figures are not necessarily to scale; rather, the focus is on illustrating the principles of the invention. Furthermore, identical reference numerals in the figures denote corresponding parts in the different views. BRIEF DESCRIPTION OF THE DRAWINGS Fig. Figure 1 is a cross-sectional view of a power semiconductor module arrangement. Fig. Figure 2 is a cross-sectional view of another power semiconductor module arrangement with spacers positioned between a substrate and a base plate. Fig. Figure 3 schematically shows an arrangement for forming spacers on a base plate. Fig. 4, the Fig. 4A and Fig. 4B contains, schematically shows top views of a base plate ( Fig. 4A) and after ( Fig. 4B) the formation of a coating layer on it. Fig. Figure 5 schematically shows a mask for forming a coating layer on a base plate. Fig. 6, the Fig. 6A and Fig. Section 6B contains schematic top views of a base plate with a coating layer ( Fig. 6A) and after ( Fig. 6B) forming several spacers thereon using a method according to embodiments of the disclosure. Fig. 7, the Fig. 7A and Fig. 7B contains schematic top views of a base plate without a coating layer ( Fig. 7A) and after ( Fig. 7B) forming several spacers on it. Fig. Figure 8 schematically shows a mask for forming multiple spacers on a base plate. Fig. Figure 9 schematically shows an arrangement for forming several spacers on a base plate. Fig. 10, the Fig. 10A and Fig. 10B contains schematic top views of a base plate without a coating layer ( Fig. 10A) and after ( Fig. 10B) the simultaneous formation of a coating layer and several spacers thereon using a method according to further embodiments of the disclosure. Fig. 11, the Fig. 11A and Fig. 11B contains schematically shows top views of a base plate with a coating layer ( Fig. 11A) and after ( Fig. 11B) forming several spacers thereon using a method according to further embodiments of the disclosure. Fig. 12, the Fig. 12A and Fig. 12B contains schematic top views of a base plate without a coating layer ( Fig. 12A) and after ( Fig. 12B) forming several spacers thereon using a method according to further embodiments of the disclosure. Fig. Figure 13 schematically shows in a cross-sectional view a base plate with several spacers formed on it using a method according to embodiments of the disclosure. Fig. Figure 14 schematically shows in a cross-sectional view a base plate with several spacers formed on it using a method according to further embodiments of the disclosure. Fig. Figure 15 schematically shows a cross-sectional view of a coating layer with several spacers formed on it. DETAILED DESCRIPTION

[0008] The following detailed description refers to the accompanying drawings. The drawings show specific examples of how the invention can be implemented. It is understood that the features and principles described in relation to the various examples can be combined with one another, unless expressly stated otherwise. In the description and in the claims, designations of certain elements as "first element," "second element," "third element," etc., are not to be understood as enumerative. Rather, such designations merely serve to name different "elements." That is to say, for example, that the presence of a "third element" does not necessarily require the presence of a "first element" and a "second element."An electrical conductor or electrical connection, as described here, can be a single electrically conductive element or at least two single electrically conductive elements connected in series and / or parallel. Electrical conductors and electrical connections can contain metal and / or semiconductor material and can be permanently electrically conductive (i.e., non-switchable). A semiconductor body, as described here, can be made of (doped) semiconductor material and can be a semiconductor chip or contained within a semiconductor chip. A semiconductor body has electrically connecting pads and contains at least one semiconductor element with electrodes.

[0009] Referring to Fig. Figure 1 schematically represents a substrate 10. The substrate 10 comprises, for example, a dielectric insulating layer 11, a (structured) first electrically conductive layer 111, and a (structured) second electrically conductive layer 112. The first electrically conductive layer 111 is arranged on a first side of the dielectric insulating layer 11, and the second electrically conductive layer 112 is arranged on a second side of the dielectric insulating layer 11 opposite the first side. The dielectric insulating layer 11 is thus positioned between the first electrically conductive layer 111 and the second electrically conductive layer 112. However, the second electrically conductive layer 112 is optional. It is also possible to arrange only the first electrically conductive layer 111 on the dielectric insulating layer 11 and to omit the second electrically conductive layer 112 entirely.

[0010] The first electrically conductive layer 111 and the second electrically conductive layer 112 can each consist of or comprise one of the following materials: copper, a copper alloy, aluminum, an aluminum alloy, or any other metal or metal alloy that remains in a solid state during operation of the power semiconductor module. The substrate 10 can be a ceramic substrate, that is, a substrate in which the dielectric insulating layer 11 consists of ceramic. The dielectric insulating layer 11 can thus be, for example, a thin ceramic layer. The ceramic of the dielectric insulating layer 11 can, for example, consist of or comprise one of the following materials: aluminum oxide, aluminum nitride, zirconium oxide, silicon nitride, boron nitride, or any other ceramic.For example, the dielectric insulating layer 11 can be made of or comprise one of the following materials: Al₂O₃, AlN, or Si₃N₄. The substrate 10 can be, for example, a direct copper bonding (DCB) substrate, a direct aluminum bonding (DAB) substrate, an insulated metal substrate (IMS), or an active metal brazing (AMB) substrate. The substrate 10 can also be, for example, a conventional printed circuit board (PCB) with a non-ceramic dielectric insulating layer 11. A non-ceramic dielectric insulating layer 11 can, for example, consist of or comprise a cured resin.

[0011] Referring to Fig. 1. One or more semiconductor bodies 20 can be arranged on the substrate 10. Each of the semiconductor bodies 20 on the substrate 10 can comprise 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 controllable semiconductor device. The one or more semiconductor bodies 20 can form a semiconductor array on the substrate 10. In Fig. 1 shows only two semiconductor bodies 20 as examples.

[0012] The in Fig. The first electrically conductive layer 111 shown in Figure 1 is a structured layer. In this context, "structured layer" means that the first electrically conductive layer 111 is not a continuous layer, but has discontinuities between different sections of the layer. Different semiconductor bodies 20 can be arranged on the same section or on different sections of the first electrically conductive layer 111. The different sections of the first electrically conductive layer 111 may either have no electrical connection to each other or may be electrically connected to each other, e.g., by bond wires. Each of the semiconductor bodies 20 can be electrically and mechanically connected to the substrate 10 by an electrically conductive bonding layer 22. Fig. Figure 1 shows an example of a substrate 10 with interconnection layers 22 arranged on it. Such an electrically conductive interconnection layer 22 can in principle be a solder layer, a layer of an electrically conductive adhesive or a layer of a sintered metal powder, e.g. a sintered silver powder.

[0013] In principle, the first electrically conductive layer 111 can also be a continuous layer. The second electrically conductive layer 112 (if present) can either be a continuous layer or also a structured layer.

[0014] To connect a semiconductor body 20 to the substrate 10, the semiconductor body 20 is positioned on the surface (top surface) of the substrate 10, with the bonding layer 22 being placed between the substrate 10 and the semiconductor body 20. The top surface of the substrate 10 is a surface of the first electrically conductive layer 111 that faces away from the dielectric insulating layer 11. Semiconductor bodies 20 can alternatively or additionally be connected to the substrate 10, for example, by means of bond wires 24.

[0015] The substrate 10 with at least one semiconductor body 20 arranged on it can, for example, be part of a power semiconductor module and be arranged in a package (not shown).

[0016] The substrate 10 is arranged on a base plate 30. The base plate 30 can, for example, be a metallic base plate. While in Fig. While a single substrate 10 is arranged on the base plate 30, it is also possible to arrange more than one substrate 10 on the same base plate 30. A bonding layer 26 is arranged between the substrate 10 and the base plate 30. The bonding layer 26 mechanically connects the substrate 10 and the base plate 30. It is also possible for the bonding layer 26 to establish an electrical connection between the substrate 10 and the base plate 30. The bonding layer 26 can be, for example, a solder layer, a layer of electrically conductive adhesive, or a layer of sintered metal powder, such as sintered silver powder.

[0017] The base plate 30 can, for example, be mounted on a heat sink (not shown). During operation of the semiconductor assembly, heat is generally generated. This heat can be dissipated to a heat sink via the substrate 10, the interconnect layer 26, and the base plate 30. Therefore, the interconnect layer 26 and the base plate 30 generally exhibit good thermal conductivity.

[0018] To ensure, firstly, a stable mechanical connection between the substrate 10 and the base plate 30, and secondly, good thermal conductivity, the connecting layer 26 generally has a thickness that does not fall below a certain minimum thickness and does not exceed a certain maximum thickness.

[0019] As in Fig. As shown schematically in Figure 2, spacers 32 are often provided between the base plate 30 and the substrate 10 to allow for precise adjustment of the thickness of the bonding layer 26 when connecting the substrate 10 to the base plate 30. These spacers 32 have a thickness in a direction perpendicular to the upper (first) surface of the base plate 30 that corresponds to the desired thickness of the bonding layer 26. In this case, the upper (first) surface of the base plate 30 is the surface on which at least one substrate 10 is arranged.

[0020] One or more spacers 32 can, for example, be arranged on the base plate 30 before the one or more substrates 10 and the respective bonding layers 26 are placed on them. The substrate(s) 10 can then be placed on or pressed onto the spacers 32. The space between the base plate 30 and the substrate 10 can be completely filled by the bonding layer 26. The (minimum) thickness of the bonding layer 26 can thus be easily adjusted. The spacers 32 can have any suitable shape and can be arranged at any suitable position on the base plate 30. Typically, as few spacers 82 as possible are used to save material and thus costs. For example, a spacer 32 is arranged under each corner of a rectangular or square substrate 10.When the substrate(s) 10 are connected to the base plate 30 by the connecting layers 26, the material forming the connecting layers 26 is initially typically liquid or viscous. The liquid or viscous material of the connecting layers 26 can be displaced to a certain extent in the horizontal directions x, z, and the thickness of the connecting layers 26 can decrease, at least in some areas. The spacers 32 prevent the substrate(s) 10 from moving closer to the base plate 30. The spacers 32 can remain between the substrate(s) 10 and the base plate 30 after the substrate(s) 10 have been mounted / connected on the base plate 30.

[0021] A method for forming multiple spacers 32 on a base plate 30 according to embodiments of the disclosure comprises attaching a base plate 30 for a semiconductor module to a lateral side of a rotatable disk 400, wherein a first surface of the base plate 30 faces away from the rotatable disk 400, and directing an outlet of a spray gun 404 toward a first edge of the first surface of the base plate 30. A spacer mask 402 is attached to the rotatable disk 400 and / or to the base plate 30 such that the spacer mask 402 is located adjacent to the first surface of the base plate 30 and between the base plate 30 and the spray gun 404. The spacer mask 402 has multiple openings 410, the size and shape of each of the multiple openings 410 corresponding to the size and shape of a spacer 32 to be formed on the base plate 30.The rotatable disc 400 with the base plate 30 and the spacer mask 402 attached to it is then rotated at a constant speed in a horizontal direction (about a rotational axis X) so that the base plate 30 and the spacer mask 402 repeatedly pass through the outlet of the spray gun 404. Particles of a first material are sprayed through the outlet of the spray gun 404 onto the spacer mask 402 and the sections of the first surface of the base plate 30 visible through the openings 410 in the spacer mask 404, while the spray gun 404 is moved in a vertical direction from the first edge to an opposite second edge of the first surface of the base plate 30, the spray gun 404 being moved at a constant speed from the first edge to the opposite second edge of the first surface of the base plate 30.

[0022] A base plate 30 attached to a rotatable disc 400, a spray gun 404 directed towards the base plate 30, and a spacer mask 402 arranged in front of the base plate 30 and between the base plate 30 and the spray gun 404 are in Fig. 3 schematically represented. A rotation of the rotatable disk 400 about the axis of rotation X is shown in Fig. 3 is indicated by a ring-shaped arrow. The movement of the spray gun 404 and the respective particle jet, which is directed towards the spacer mask 402 and the base plate 30, is shown in Fig. 3 indicated by a vertical arrow. In the case of the Fig. In the example shown in Figure 3, the spray gun 404 moves from an upper edge of the base plate 30 downwards towards the opposite lower edge. However, it is also possible for the spray gun 404 to move upwards from the lower edge to the upper edge. A spacer mask 402 according to embodiments of the disclosure is shown in Fig. 8 shown schematically.

[0023] The base plate 30 can be made of a solderable material such as copper. In this case, spacers 32 can be formed directly on the first surface of the base plate 30. Spraying particles of a first material onto the first surface of the base plate 30 through the outlet of the spray gun 404 can, for example, involve spraying copper particles onto the first surface of the base plate 30 through the outlet of the spray gun 404. That is, for example, copper spacers 32 could be formed on a copper base plate 30.

[0024] However, some base plates 30 are not made of a solderable material. For example, some base plates 30 are made of AlSiC. If a base plate 30 is not made of a solderable material, it is not possible to directly attach a substrate 10 to it via a bonding layer 26. In this case, a coating layer 34 can first be formed on the base plate 30. The coating layer 34 is made of a solderable material. In this way, it is possible to attach a substrate 10 to the base plate 30, with the coating layer 34 positioned between the substrate 10 and the base plate 30, and in particular between the bonding layer 26 and the base plate 30. In such a case, the multiple spacers 32 are not formed directly on the base plate 30, but instead on the coating layer 34.

[0025] This means that if the base plate 30 is not made of a solderable material, the method may further include, prior to attaching the spacer mask 402 to the rotatable disk 400 and / or to the base plate 30, attaching a coating mask 406 to the rotatable disk 400 and / or to the base plate 30, such that the coating mask 406 is arranged adjacent to the first surface of the base plate 30 and between the base plate 30 and the spray gun 404. The coating mask 406 has one or more openings 412, the size and shape of each opening 412 corresponding to the size and shape of a coating layer 34 to be formed on the base plate 30.The method further comprises rotating the rotatable disk 400 with the base plate 30 and the coating mask 406 attached to it at a constant rotational speed in the horizontal direction (about the axis of rotation X), so that the base plate 30 and the coating mask 406 repeatedly pass through the outlet of the spray gun 404, whereby particles of the first material are sprayed onto the coating mask 406 and the sections of the first surface of the base plate 30 visible through the openings 412 in the coating mask 406 through the outlet of the spray gun 404, while the spray gun 404 is moved in the vertical direction from the first edge towards the second edge of the first surface of the base plate 30 at a constant speed. Once the coating layer 34 has been formed, the coating mask 406 can be removed.

[0026] This means that the coating layer 34 is first formed using a first mask (the coating mask 406), and only then are the multiple spacers 32 formed using a second mask (the spacer mask 402), which is different from the first mask. The resulting coating layer 34 can have one or more sections. Fig. Figure 4 schematically shows top views of a base plate ( Fig. 4A) and after ( Fig. 4B) the formation of a coating layer 34 on it. In the case of the Fig. In the example shown in Figure 4, the coating layer 34 has several distinct sections. The number of sections of the coating layer 34 can correspond to the number of substrates 10 to be attached to the base plate 30. That is, if only one substrate 10 is to be attached to the base plate 30, a continuous coating layer 34 can be formed on the base plate 30 (the coating layer has only one continuous section). However, it is also conceivable that a single large continuous coating layer 34 could be used if several substrates 10 are to be attached to the base plate 30. In the example shown in Figure 4, the coating layer 34 has several distinct sections. Fig. In the example shown in Figure 4B, the coating layer 34 has six separate sections. This means that six individual substrates 10 can be attached to the base plate 30. A corresponding coating mask 406 is shown in Fig. Figure 5 is shown schematically. That is, in this example, the coating mask 406 has six openings 412. The coating layer 34 generally covers large parts of the base plate 30. For example, the coating layer 34 can cover at least 40% or at least 50% of the first surface of the base plate 30. In contrast, the spacers 32 are generally comparatively small compared to the size of the base plate 30. For example, the multiple spacers 32 can cover less than 20% or even less than 10% of the first surface of the base plate 30.

[0027] Fig. Figure 6 schematically shows top views of a base plate 30 with a coating layer 34 ( Fig. 6A) and after ( Fig. 6B) forming several spacers 32 thereon using a method according to embodiments of the disclosure. Fig. Figure 7 schematically shows top views of a base plate 30 without a coating layer 34 ( Fig. 7A) and after ( Fig. 7B) forming several spacers thereon using a method according to embodiments of the disclosure.

[0028] The spacers in the Fig. 6B and Fig. 7B have a rectangular cross-section and extend parallel to the first and second edges of the base plate 30. However, this is only one example. In general, the spacers 32 can have any suitable cross-section, such as a round or square cross-section. Any other cross-section is also possible. According to one example, the spacers 32 have an elongated shape, similar to what is shown in the Fig. 6B and Fig. Figure 7B illustrates this by way of example. That is, the length of a spacer 32 in a first horizontal direction x can be significantly greater than the width of the spacer 32 in a second horizontal direction z perpendicular to the first horizontal direction x. For example, a spacer 32 can extend along at least 50%, at least 75%, or even at least 90% of the length or width of a substrate 10 when the substrate 10 is attached to the base plate 30. The number of spacers 32, as well as their shape and dimensions, can depend, for example, on the size and shape of the respective substrate 10.

[0029] However, using a spacer mask 402 to form the multiple spacers 32 on the base plate 30 is only one example. A method for forming multiple spacers 32 on a base plate 30 according to further embodiments of the disclosure includes attaching a base plate 30 for a semiconductor module to a lateral side of a rotatable disk 400, wherein a first surface of the base plate 30 faces away from the rotatable disk 400, directing an outlet of a spray gun 404 toward a first edge of the first surface of the base plate 30, rotating the rotatable disk 400 with the base plate 30 attached thereto at a constant rotational speed in a horizontal direction, such that the first surface of the base plate 30 repeatedly passes the outlet of the spray gun 404, and spraying particles of a first material onto the first surface of the base plate 30 through the outlet of the spray gun 404.Several holding positions are defined between the first edge and the opposite second edge of the first surface of the base plate 30. The spray gun 404 moves successively from one holding position to the next, pausing at each holding position for a defined duration. The spraying of particles of a first material onto the first surface of the base plate 30 through the outlet of the spray gun 404 involves the spraying of particles of a first material onto the first surface of the base plate 30 while the spray gun 404 pauses at each of the several holding positions.

[0030] This is schematically shown in Fig. Figure 9 shows the holding positions as black dots along the path of movement of the spray gun 404. At each holding position, the spray gun 404 can stop long enough to form a spacer 32 with a defined height / thickness in a direction perpendicular to the first surface of the base plate 30. If the spacers 32 are formed directly on the first surface of the base plate 30 and no mask is used at all during the formation of the spacers 32, this results in continuous spacers 32 extending from a third edge to an opposite fourth edge of the first surface of the base plate 30, with the third and fourth edges being perpendicular to the first and second edges. This is shown in Figure 9. Fig. 12, the schematic top views of a base plate 30 without coating layer 34 before ( Fig. 12A) and after ( Fig. 12B) the formation of several continuous spacers 32 shown schematically.

[0031] If a coating layer 34 is required on the first surface of the base plate 30 and between the base plate 30 and the multiple spacers 32, the method may, prior to rotating the rotatable disk 400 with the base plate 30 attached thereto, further include attaching a coating mask 406 to the rotatable disk 400 and / or to the base plate 30 such that the coating mask 406 is arranged adjacent to the first surface of the base plate 30 and between the base plate 30 and the spray gun 404, wherein the coating mask 406 has multiple openings 412, wherein a size and shape of each opening 412 of the multiple openings 412 corresponds to a size and shape of a coating layer 34 to be formed on the base plate 30 and between the base plate 30 and the multiple spacers 32.

[0032] According to some embodiments, the spray gun 404 can move at a constant speed from one holding position to the next, and the spraying of particles of the first material onto the first surface of the base plate 30 through the outlet of the spray gun 404 can further include the spraying of particles of the first material onto the first surface of the base plate 30 while the spray gun 404 moves from one holding position to the next. In this way, the coating layer 34 and the multiple spacers 32 can be formed simultaneously. In particular, particles of the first material are sprayed onto the first surface of the base plate 30 while the spray gun 404 moves at a constant speed from one holding position to the next, thereby forming sections of the coating layer 34 with a defined thickness.The spray gun 404 stops at each holding position for a defined duration, resulting in a thickness of the material deposited on the base plate 30 that is greater than the thickness of the layer in the areas between the holding positions, thereby forming the spacers 32.

[0033] Alternatively, the coating layer 34 and the multiple spacers 32 can be formed successively in two separate steps. That is, before rotating the rotatable disc 400 with the base plate 30 attached to it, a coating mask 406 can be attached to the rotatable disc 400 and / or to the base plate 30 such that the coating mask 406 is located adjacent to the first surface of the base plate 30 and between the base plate 30 and the spray gun 404, wherein the coating mask 406 has multiple openings 412.wherein the size and shape of each opening 412 of the multiple openings 412 corresponds to the size and shape of a coating layer 34 to be formed on the base plate 30 and between the base plate 30 and the multiple spacers 32. Before moving the spray gun 404 successively from one holding position to the next and spraying particles of the first material through the outlet of the spray gun 404 onto the first surface of the base plate 30, while the spray gun 404 stops at each of the multiple holding positions, the rotatable disc 400 with the base plate 30 and the coating mask 406 attached to it can be rotated at a constant speed, so that the base plate 30 and the coating mask 406 repeatedly pass the outlet of the spray gun 404.Particles of the first material can be sprayed through the outlet of the spray gun 404 onto the coating mask 406 and the sections of the first surface of the base plate 30 visible through the openings 412 in the coating mask 406, while the spray gun 404 is moved vertically from the first edge to the second edge of the first surface of the base plate 30 at a constant speed. In this way, a coating layer 34 of constant thickness is formed. The outlet of the spray gun 404 is then directed again toward the first edge of the first surface of the base plate 30. The multiple spacers 32 are then formed in a separate subsequent step.by moving the spray gun 404 from one holding position to the next, spraying particles of the first material through the outlet of the spray gun 404 onto the first surface of the base plate 30 while the spray gun 404 stops at each holding position. When forming the multiple spacers 32 in a separate step, no particles of the first material are sprayed onto the first surface of the base plate 30 while the spray gun 404 moves from one holding position to the next.

[0034] Fig. Figure 10 schematically shows top views of a base plate 30 without coating layer 34 ( Fig. 10A) and after ( Fig. 10B) the simultaneous formation of a coating layer 34 and several spacers 32 on it. Fig. Figure 11 schematically shows top views of a base plate with a coating layer ( Fig. 11A) and after ( Fig. 11B) forming several spacers on it.

[0035] The methods according to the embodiments described here can involve spraying copper particles onto the first surface of the base plate 30 through the outlet of the spray gun 404. According to some examples, the spraying of particles of the first material onto the first surface of the base plate 30 through the outlet of the spray gun 404 can involve a cold gas spraying process.

[0036] A maximum thickness d32 of each spacer 32 of the several spacers 32 in a direction perpendicular to the first surface of the base plate 30 generally depends on at least one of the following factors: a temperature at which the spraying is carried out, a pressure at which the spraying is carried out, how often the spraying is carried out, a distance between the outlet of the spray gun 404 and the first surface of the base plate 30 if the first surface of the base plate 30 is perpendicular to a direction of a particle jet emitted by the spray gun 404, a powder feed rate supplied to the spray gun 404, and a relative velocity between the spray gun 404 and the rotatable disk 400 if the rotatable disk 400 is rotated at a constant speed.This means that when forming each spacer 32 of the several spacers 32, at least one of the mentioned parameters of the spraying process can differ from the respective parameter used when forming the coating layer 34.

[0037] In general, when a spacer mask 402 is used to form the multiple spacers 32, the spacers 32 have a constant thickness d32 in a direction perpendicular to the first surface of the base plate 30. This is because the edges of the resulting spacers 32 are defined by the lateral surfaces of the openings 410 in the spacer mask 402. This is shown in the cross-sectional view of Fig. Figure 13 shows schematic representations. If no spacer mask is used to form the multiple spacers 32, the spacers generally have a varying thickness d32 in a direction perpendicular to the first surface of the base plate 30. This is because, when no spacer mask 402 is used, the thickness of the resulting spacers 32 follows a Gaussian distribution of the particles on the first surface of the base plate 30 or on the coating layer 34. This is shown schematically in the cross-sectional view of Fig. Figure 14 illustrates this. In general, the maximum thickness d32 of each spacer 32 of the multiple spacers 32 can, for example, be in the range of 100 µm to 500 µm. The maximum width w32 of each spacer 32 of the multiple spacers 32 can, for example, be in the range of 1 mm to 5 mm.

[0038] Referring to Fig.15. A distance s32 between an edge of a coating layer 34 and a spacer 32 located closest to that edge can be, for example, between 1 mm and 10 mm. In this way, the distance s32 is large enough to ensure that the substrate 10, i.e., the second electrically conductive layer 112 of the substrate 10 to be mounted on the coating layer 34, rests on the spacers 32. At the same time, the distance s32 is short enough to prevent the substrate 10 mounted on the respective spacers 32 from unintentionally tipping over.

Claims

[1] Method for forming multiple spacers (32) on a base plate (30) comprising: Attaching a base plate (30) for a semiconductor module to a lateral side of a rotatable disk (400), wherein a first surface of the base plate (30) faces away from the rotatable disk (400); Directing an outlet of a spray gun (404) towards a first edge of the first surface of the base plate (30); Attaching a spacer mask (402) to the rotatable disk (400) and / or to the base plate (30) such that the spacer mask (402) is located adjacent to the first surface of the base plate (30) and between the base plate (30) and the spray gun (404), wherein the spacer mask (402) has several openings (410), wherein the size and shape of each opening (410) of the several openings (410) corresponds to the size and shape of a spacer (32) to be formed on the base plate (30); Rotating the rotating disc (400) with the base plate (30) and the spacer mask (402) attached to it at a constant rotational speed in a horizontal direction, so that the base plate (30) and the spacer mask (402) repeatedly pass the outlet of the spray gun (404); and Spraying particles of a first material onto the spacer mask (402) and the sections of the first surface of the base plate (30) visible through the openings (410) in the spacer mask (404) through the outlet of the spray gun (404) while the spray gun (404) is moved in a vertical direction from the first edge to an opposite second edge of the first surface of the base plate (30), the spray gun (404) being moved from the first edge to the opposite second edge of the first surface of the base plate (30) at a constant speed. [2] The method of claim 1, further comprising the application of a coating mask (406) to the rotatable disk (400) and / or to the base plate (30) prior to the application of a spacer mask (402) to the rotatable disk (400) and / or to the base plate (30), such that the coating mask (406) is arranged adjacent to the first surface of the base plate (30) and between the base plate (30) and the spray gun (404), wherein the coating mask (406) has several openings (412), wherein a size and shape of each opening (412) of the several openings (412) corresponds to a size and shape of a coating layer (34) to be formed on the base plate (30), the rotating disc (400) with the base plate (30) and the coating mask (406) attached to it at a constant rotational speed in the horizontal direction, so that the base plate (30) and the coating mask (406) repeatedly pass the outlet of the spray gun (404); the spraying of particles of the first material onto the spacer mask (402) and the sections of the first surface of the base plate (30) visible through the openings (412) in the coating mask (404) through the outlet of the spray gun (404), while the spray gun (404) is moved in the vertical direction from the first edge to the second edge of the first surface of the base plate (30), the spray gun (404) being moved from the first edge to the second edge at a constant speed, and the removal of the coating mask (406). [3] Method for forming multiple spacers (32) on a base plate (30) comprising: the attachment of a base plate (30) for a semiconductor module to a lateral side of a rotatable disk (400), wherein a first surface of the base plate (30) faces away from the rotatable disk (400); the directing of an outlet of a spray gun (404) towards a first edge of the first surface of the base plate (30); the rotation of the rotatable disc (400) with the attached base plate (30) at a constant rotational speed in a horizontal direction, so that the first surface of the base plate (30) repeatedly passes the outlet of the spray gun (404); and the spraying of particles of a first material onto the first surface of the base plate (30) through the outlet of the spray gun (404), wherein between the first edge and an opposite second edge of the first surface of the base plate (30) several holding positions are defined, the spray gun (404) moves successively from one holding position to the next holding position, stopping at each holding position for a defined duration, and the spraying of particles of a first material onto the first surface of the base plate (30) through the outlet of the spray gun (404) while the spray gun (404) stops at each of the several holding positions. [4] The method of claim 3, further comprising the application of a coating mask (406) to the rotatable disk (400) and / or to the base plate (30) prior to rotating the rotatable disk (400) with the base plate (30) attached thereto, such that the coating mask (406) is arranged adjacent to the first surface of the base plate (30) and between the base plate (30) and the spray gun (404), wherein the coating mask (406) has several openings (412), wherein the size and shape of each opening (412) of the several openings (412) corresponds to the size and shape of a coating layer (34) to be formed on the base plate (30) and between the base plate (30) and the several spacers (32). [5] Method according to claim 4, wherein the spray gun (404) moves from one holding position to the next holding position at a constant speed and further comprises the spraying of particles of a first material onto the first surface of the base plate (30) through the outlet of the spray gun (404), while the spray gun (404) moves from one holding position to the next holding position. [6] The method of claim 4, which, prior to successively moving the spray gun (404) from one holding position to the next holding position and spraying particles of a first material onto the first surface of the base plate (30) through the outlet of the spray gun (404), while the spray gun (404) stops at each of the multiple holding positions, further the rotating disc (400) with the base plate (30) and the coating mask (406) attached to it at a constant speed, so that the base plate (30) and the coating mask (406) repeatedly pass the outlet of the spray gun (404); the spraying of particles of the first material onto the coating mask (406) and the sections of the first surface of the base plate (30) visible through the openings (412) in the coating mask (406) through the outlet of the spray gun (404), while the spray gun (404) is moved in a vertical direction from the first edge to the second edge of the first surface of the base plate (30), the spray gun (404) moving from the first edge to the second edge of the first surface of the base plate (30) at a constant speed, and the re-alignment of the outlet of a spray gun (404) to the first edge of the first surface of the base plate (30) exhibits. [7] Method according to one of the preceding claims, wherein the spraying of particles of a first material onto the first surface of the base plate (30) through the outlet of the spray gun (404) comprises the spraying of copper particles onto the first surface of the base plate (30) through the outlet of the spray gun (404). [8] Method according to one of the preceding claims, wherein the spraying of particles of a first material onto the first surface of the base plate (30) through the outlet of the spray gun (404) comprises a cold gas spraying process. [9] Method according to one of the preceding claims, wherein a maximum thickness (d32) of each spacer (32) of the multiple spacers (32) in a direction perpendicular to the first surface of the base plate (30) depends on at least one of the following factors: a temperature at which the spraying is carried out, a pressure with which the spraying is carried out, a distance between the outlet of the spray gun (404) and the first surface of the base plate (30), if the first surface of the base plate (30) is perpendicular to a direction of a particle beam emitted by the spray gun (404), one of the powder feed rates supplied to the spray gun (404), and a relative velocity between the spray gun (404) and the rotating disc (400) when the rotating disc (400) is rotated at a constant speed.

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