Soldering process

Abstract

Soldering process with the steps: Providing a soldering system (200) having a heating chamber (211, 212, 213) with an inductive heating unit (250) designed to provide energy, and a cooling chamber (221, 222) with at least one cooling device (270); Providing at least two sets (50) of components (1, 2, 8) to be soldered together, each of the sets (50) comprising a first soldering partner (1, 2) and a second soldering partner (2, 8) as well as a solder (11, 23); positioning each of the sets (50) of components (1, 2, 8) in the heating chamber (211, 212, 213) such that the solder (11, 23) is arranged between the first soldering partner (1, 2) and the second soldering partner (2, 8); for each of at least two of the two sets (50): providing a temperature measuring unit individually associated with the respective one of the two sets (50), each of the temperature measuring units being integrated into and / or attached to one of the components (1, 2, 8) of the corresponding set (50); Providing at least one radio transmitter (300) and one radio receiving unit (231); Providing a control unit (232) coupled to the radio receiving unit (231) and configured to control the inductive heating unit (250); for each of the temperature measuring units: transmitting information about the temperature of one of the components (1, 2, 8) of the corresponding set (50) detected by the temperature measuring unit in question to the radio receiving unit (231) by means of the radio transmitter (300); Heating the sets (50) of components (1, 2, 8) by energy provided by the inductive heating unit (250); Controlling the energy provided by the inductive heating unit (250) in dependence on the temperature information; Transferring all sets (50) of components (1, 2, 8), after the solders (11, 23) of all sets (50) have been heated to at least their respective melting points, from the heating chamber (211, 212, 213) into the cooling chamber (221, 222); and Cooling the sets (50) of components (1, 2, 8) by the cooling device (270) by controlling the cooling device (270) in dependence on the temperature information.

Description

BACKGROUND

[0001] In brazing processes where a large number of units are brazed, it is difficult to control the quality of the brazed joints between two brazing partners. For example, when brazing many units in a conventional brazing furnace, the quality of the brazed joints can vary due to uneven heat distribution within the furnace or due to different heat capacities of the brazing partners.

[0002] The document DE 10 2006 034 600 A1 discloses a method for producing a soldered connection with the following steps: providing two soldering partners to be connected to one another at a provided joint, at least one of which comprises an electronic component or is designed as such, - providing a soldering device having an inductor, - providing an intermediate plate, - positioning the soldering partners, the inductor and the intermediate plate in such a way that the intermediate plate is arranged between the electronic component and the provided joint on the one hand and the inductor on the other hand, - connecting the soldering partners at the provided joint by means of a solder which is melted by energy emitted by the inductor.

[0003] US 4,180,199 A discloses a system for measuring time / temperature profiles of a mass soldering process. A data probe and a miniature transmitter are guided through the soldering process on the circuit board being soldered. A plurality of probes are attached to various components, component leads, and selected areas of the circuit board and provide electrical signals in response to the temperature and dwell time to which the components and board are exposed during preheating and soldering. The temperature of the solder at the point where the solder contacts the board can also be measured. The electrical signals are transmitted wirelessly, e.g., by low-frequency electromagnetic transmission, to a remote stationary receiver for integration and display. SUMMARY

[0004] A soldering method is provided in which a soldering system is equipped with at least one heating chamber and a cooling chamber. The heating chamber comprises an inductive heating unit that can be operated to provide energy, and the cooling chamber has at least one cooling device. In the method, at least two sets of components are soldered. Each of the sets comprises a first solder partner, a second solder partner, and a solder. To produce the soldered connection, each of the sets is positioned in the heating chamber. Each set comprises a solder layer, e.g., a preform solder, arranged between the first solder partner and the second solder partner of the respective set.

[0005] Additionally, a temperature measurement unit is provided for each of the sets, which is individually assigned to the respective set, with each of the temperature measurement units being integrated into and / or attached to one of the components of the respective set. Also provided are a radio transmitter, a receiver unit, and a control unit. The control unit is coupled to the receiver unit and can be used to control the inductive heating unit. Each of the temperature measurement units is thermally coupled to the respective soldering partner.

[0006] During the process, the radio transmitter can be operated to transmit temperature information about the temperature of each of the temperature measuring units to the receiving unit. For preheating or soldering, the sets of components are heated by energy provided by the inductive heating unit. The energy provided by the inductive heating unit is controlled by the heating unit being controlled using the control unit in dependence on the temperature information. This means that the heating unit is controlled by the control unit such that the energy generated by the heating unit for preheating or soldering depends on the current temperature of the individual sets. In this way, temperature profiles can be controlled and measured throughout the entire soldering cycle and the entire cycle in the furnace.After the solders of all sets have been heated to at least their respective melting points, all sets of components are transferred from the heating chamber to the cooling chamber. The cooling device cools the sets of components by controlling the cooling device based on the temperature information.

[0007] According to one aspect of the invention, the brazing can be carried out at least partially in a vacuum in a reducing atmosphere, for example at a pressure of less than 20 hPa. The reducing atmosphere can comprise one or more of the following components: hydrogen, formic acid, and one or more reducing gases. The embodiments described herein enable the control of a temperature profile of the batches throughout the entire cycle during which the batches are treated in the furnace. This is particularly true when the furnace has two or more chambers through which the batches pass, so that they move from chamber to chamber and undergo different treatments in the different chambers.To achieve this goal, the carriers that transport the batches are equipped with temperature measurement electronics and transmission electronics that move with the carriers and continuously record the temperature profile of each batch, enabling continuous control of the soldering process throughout the entire processing of the batch in the furnace. In particular, the control of the remaining soldering process at any time can depend on the temperature profiles of the batches recorded from the beginning of the soldering process up to that point.

[0008] In light of the following detailed description and upon consideration of the accompanying drawings, those skilled in the art will be able to appreciate further additional features and advantages of the invention. SHORT DESCRIPTION OF THE CHARACTERS

[0009] The invention can be better understood with reference to the following figures and description. The components shown in the figures are not necessarily drawn to scale. Fig. 1A is a cross-sectional view of a power semiconductor module. Fig. 1B shows a set of components to be soldered as used in the power semiconductor module according to Fig. 1A can be used. Fig. 2 is a sectional view of a soldering furnace. Fig. Figure 3A illustrates a portion of a carrier configured to receive a set of components to be soldered. Fig. 3B shows a section of the carrier according to Fig. 3A, into which a set of components to be soldered is inserted. Fig. 3C shows the section of the beam according to Fig. 3B, wherein one of the components is clamped to the carrier. Fig. 3D shows the section of the beam according to Fig. 3C with a temperature sensor element integrated into a power semiconductor chip and with another temperature sensor element arranged on the substrate. Fig. 4A shows a sectional view of a heating chamber and a control unit of a soldering furnace, wherein each of two sets of components to be soldered is individually provided with a radio transmitter, and wherein the two sets are heated by a common inductor. Fig. 4B is a sectional view of a heating chamber extending from the heating chamber of Fig. 4A in that the two sets of components to be soldered are equipped with a common radio transmitter instead of individual radio transmitters. Fig. 5A is a sectional view of a heating chamber and a control unit of a soldering furnace, wherein each of three sets of components to be soldered is individually equipped with a radio transmitter and a heating means. Fig. 5B is a sectional view of a heating chamber extending from the heating chamber of Fig. 5A in that the three sets of components to be soldered are equipped with a common radio transmitter instead of individual radio transmitters. Fig. 6A is a plan view of a carrier disposed in a soldering furnace having a plurality of openings, each of the openings being configured to receive a set of components to be soldered, and each of the openings having an individual radio transmitter provided therefor. Fig. 6B shows the carrier according to Fig. 6A, where the openings are equipped with sets of components to be soldered. Fig. 7A is a plan view of a carrier arranged in a soldering furnace and having a number of openings, each of the openings being configured to receive a set of components to be soldered, and a common radio transmitter being provided for collectively transmitting the temperatures of the various sets. Fig. 7B shows the carrier according to Fig. 7A, where the openings are equipped with sets of components to be soldered. Fig. 8A is a sectional view of a cooling chamber and a control unit of a soldering furnace, wherein each of three sets of components to be soldered is equipped with an individual radio transmitter and an individual cooling plate. Fig. Fig. 8B is a sectional view of a cooling chamber extending from the cooling chamber of Fig. 8A in that three sets of components to be soldered are equipped with a common radio transmitter instead of individual radio transmitters. Fig. 9 is a plan view of a carrier arranged in a cooling chamber and having a number of openings, each of the openings being adapted to receive a set of components to be soldered, and each of the openings being provided with an individual radio transmitter. Fig. Figure 10 is a plan view of a carrier extending from the carrier according to Fig. 9 in that the sets of components to be soldered are equipped with a common radio transmitter instead of individual radio transmitters. Fig. 11 is a sectional view of another power semiconductor module. Fig. 12 is a sectional view of a set comprising a substrate and a power semiconductor chip as soldering partners, which is inserted into a carrier and soldered by means of an inductor. DETAILED DESCRIPTION

[0010] In the following detailed description, reference is made to the accompanying drawings, which form a part hereof, and in which is shown by way of illustration specific embodiments in which the invention may be practiced. As used in this connection, directional terminology such as "top", "bottom", "front", "back", "fore", "rear", etc., refers to the orientation of the respective figures. Since components of the embodiments can be positioned in a number of different orientations, the directional terminology is for the purpose of illustration only and is not to be considered limiting. It is to be understood that the invention may be practiced in other embodiments that are structurally or logically different from the embodiments shown.The following detailed description is therefore not to be construed in a limiting sense; the scope of the present invention is defined by the appended claims. It is understood that the features of the various exemplary embodiments described may be combined with one another in any way, unless otherwise stated or unless the combination of certain features is technically impossible.

[0011] Referring to Fig. 1A illustrates an embodiment of a power semiconductor module 100. The power semiconductor module 100 comprises a flat base plate 8 with a top side 8t and a bottom side 8b. Together with an injection-molded housing 4, which has side walls 41 and an optional housing cover 42, the base plate 8 forms a housing of the power semiconductor module 100. Furthermore, the bottom side 8b of the base plate 8 represents part of the bottom side of the power semiconductor module 100.

[0012] The module 100 comprises at least one substrate 2. Each substrate 2 has a dielectric insulating support 20 provided with an upper metallization 21 and an optional lower metallization 22. For example, the upper metallization 21 can have a thickness in the range of 0.1 mm to 0.6 mm. The insulating support 20 serves to electrically insulate the upper metallization 21 from the base plate 8.

[0013] One or more power semiconductor chips 1 are arranged on the substrate 2. In the embodiment according to Fig. 1, each of the power semiconductor chips 1 can have a controllable power semiconductor switch, for example, an IGBT (insulated gate bipolar transistor), a MOSFET (metal oxide semiconductor field-effect transistor), a JFET (junction field-effect transistor), a thyristor, or a diode. However, in other examples of a power semiconductor module, the number and type of waste heat-generating power semiconductor chips 1 arranged on the substrate 2 are arbitrary.

[0014] In Fig. 1A, the power semiconductor chips 1 are mounted on the upper metallization 21 by means of a connecting layer 11, for example a solder layer, a diffusion solder layer with a significant proportion of intermetallic phases, an electrically conductive adhesive or a sintered layer and are electrically conductively connected to the latter.

[0015] The top sides of the semiconductor chips 1 can be electrically connected, for example, by bonding, electrically conductive adhesive, sintering, or through-printing. In the embodiment according to Fig. 1A, a number of bond wires 5 are provided that connect various components of the module 100 to one another. Instead of bond wires 5, the power semiconductor chips 1 can be electrically connected by clips, which can be soldered, diffusion-soldered, sintered, or pressure-contacted to a top-side contact of the respective power semiconductor chip.

[0016] To enable sufficient cooling of the power semiconductor chips 1, an important property of the dielectric layer 20 is a low thermal resistance. Therefore, it is necessary that the material and thickness of the dielectric layer 20 be adapted to the requirements of the power semiconductor module 100. For example, the insulating carrier 20 can be a ceramic, so that the substrate 2 forms a ceramic substrate. For example, the insulating carrier 20 can comprise one or more of the following materials: aluminum oxide (Al2O3); aluminum nitride (AIN); silicon nitride (Si3N4). Furthermore, the thickness of one, several, or each such ceramic substrate can be in the range from 0.2 mm to 2 mm.

[0017] Furthermore, at least one of the substrates 2 can be a DCB substrate (DCB = direct copper bonding), a DAB substrate (DAB = direct aluminum bonding), or an AMB substrate (AMB = active metal brazing).

[0018] The base plate 8 may comprise or consist of an electrically conductive metal plate (e.g., made of copper or aluminum), which may optionally be provided on its surface with a thin layer of material, e.g., made of nickel, to improve the solderability of the base plate 8. In general, a power semiconductor module 100 comprises a number of connection lugs 3 provided with terminals 31 that enable electrical connection of the module 100 to other components, such as power supply units, intermediate circuit capacitors, electrical machines, other power semiconductor modules, and / or a control unit. Inside the module housing 4, the connection lugs 3 are electrically connected to the upper metallization 21 and / or to one or more of the power semiconductor chips 1. In the embodiment according to Fig. 1A, the respective electrical connections are realized using bonding wires 5. However, any other connection techniques are equally suitable for establishing the respective electrically conductive connections.

[0019] To mount the bottom 8b of the module 100 to a heat sink (not shown), the base plate 8 and the module housing 4 may have optional screw holes 84 and 44, respectively.

[0020] Optionally, the interior of the housing 4 can be filled with an insulating soft potting compound (not shown), e.g., a silicone gel, which extends from the base plate 8 and covers at least the upper metallization 21 and the power semiconductor chips 1 in order to increase the insulation strength of the module 100.

[0021] The area of ​​the underside of the lower metallization 22, i.e., the side of the lower metallization 22 facing the base plate 8, can be greater than or equal to 0.2 mm, for example, which is large compared to the soldering areas of conventional electronic components. Therefore, soldering a substrate 2 to a base plate 8 is challenging. If, for example, shrinkage cavities occur in the solder layer 23, the electrical and thermal contact between the substrate 2 and the power semiconductor chips 1 is very poor, and the dissipation of the waste heat generated in the power semiconductor chips 1 to the base plate 8 is insufficient.

[0022] To improve the quality of soldered joints, a method is provided that allows the individual temperatures of a number of components to be soldered to be monitored during a heating step and / or a subsequent cooling step. This method enables continuous monitoring of the current temperatures of each unit to be produced by soldering. There is no need to use "dummy" units for temperature measurement. Knowing the current temperatures of all units at any given time allows the heating temperature and / or cooling temperature to be controlled depending on these temperatures.

[0023] In order to manufacture a power semiconductor module as described above with reference to Fig. 1A, the unit comprising the base plate 8, the solder 23, the substrate 2, the solder 11, and the power semiconductor chips 1 can be manufactured by soldering the connection between the substrate 2 and the base plate 8 in a first step and mounting this prefabricated unit on the module housing 4 in a subsequent second step. In the soldering process of the first step, a number of similar or identical units can be prefabricated by soldering these units simultaneously, ie, in parallel with one another.

[0024] For each unit to be manufactured, a set of 50 components 8, 10 and 23 to be soldered together is provided, as shown in Fig. 1B. The set 50 comprises a first solder partner 8, a second solder partner 10, and a solder 23. In the present example, the first solder partner is a base plate 8. The second solder partner 10 is a substrate 2 which is populated with one or more power semiconductor chips 1, which are soldered to the substrate 2 through the connection layer 11. The melting point of the connection layer 11 can be higher than the melting point of the solder 23 in order to avoid reflow or other degradation of the connection layer 11 during the subsequent soldering process. According to a further embodiment, the first solder partner can be a semiconductor chip 1 and the second solder partner can be the substrate 2 to which the semiconductor chip 1 is to be soldered. According to yet another embodiment, one, several or each of the sets 50 can have more than one solder partner.For example, the solder connection 11 between a semiconductor chip 1 and a substrate and the solder connection 23 between the same substrate 2 and the base plate 8 can be produced by soldering during the same soldering step, ie three soldering partners are provided which are soldered to one another in parallel: the semiconductor chip 1, the substrate 2 and the base plate 8.

[0025] Compared to conventional solder joints, solders 11 and 23 extend over a large area. For example, solder 11 can have a base area of ​​at least 25 mm 2 and Lot 23 has a base area of ​​at least 400 mm 2Therefore, the production of the respective soldered joints 11 and 23 is challenging. For example, there is a risk of shrinkage cavities that may remain in the solder 11, 23 after the soldering process is completed. Shrinkage cavities can adversely affect the electrical and thermal connection between the respective solder partners.

[0026] In the power semiconductor module according to Fig. 1A is merely an illustrative embodiment of a power semiconductor module. Other embodiments may have different details. For example, instead of a thick base plate 8, a substrate 2 having two or more metallization layers 21, 22 and one or more insulation layers 20 located between the metallization layers 21, 22 may serve as the base plate, i.e., the bottommost metallization layer 22 of such a substrate 2 then forms an outer surface of the power semiconductor module.

[0027] Fig. Figure 2 illustrates a soldering system 200 with a heating section 210, a cooling section 220, and a receiving and control unit 230. The soldering system 200 can be used, in particular, to solder a number of sets 50 simultaneously, as described above. A soldering method is explained below, in which a soldering system is used that has the same or similar features as the previously explained soldering system 200, in which a number of sets 50 are soldered simultaneously. By way of example, the sets 50 are sets as described with reference to Fig. 1B. However, other sets can be soldered in the same manner. At least one heating chamber 211, 212, 213 is located in the heating section 210 of the soldering system 200, and at least one cooling chamber 221, 222 is located in the cooling section 220. The heating chambers 211, 212, 213 can be used to preheat the sets 50 or to melt the solder 23 of the sets 50. After the solder 23 of all sets has been melted, the sets 50 can be cooled in one or more cooling chambers 221, 222.

[0028] For example, the cooling system 200 may have one to three heating chambers 211, 212, 213 and one or two cooling chambers 221, 222. In each heating chamber 211, 212, 213, there is a heating element 250, which serves to preheat the sets 50 and / or to melt the solder 23 of the sets 50. In one example, a heating element 250 may have one or more inductors. Accordingly, a cooling element 260, 270 is located in each cooling chamber 221, 222. For example, the cooling chamber 221 includes a cooling element 260 that provides one or more jets of a cooling fluid, for example, air or another gas. In another example, the cooling chamber 222 includes a cooling element 270 that includes a number of cooling plates.

[0029] Both the heating element 250 and the cooling elements 260, 270 can be controlled using a control unit 232 to adjust the required intensity of the heating process or the cooling process depending on the individual temperatures of all sets 50.

[0030] The basis for controlling the heating element 250 and the cooling elements 260, 270 is the transmission of the temperatures of at least two or, ideally, all sets 50 to the control unit 232, which is a component of the receiving and control unit 230. More specifically, the transmission of the temperatures is achieved by transmitting signals corresponding to the temperatures. As shown in Fig. 2, these signals may be radio signals transmitted via an RF (radio frequency) radio transmitter 300 and received by a receiving unit 231. The control unit 232, which is coupled to the receiving unit 231, evaluates the temperature information contained in the radio signal received by the receiving unit 231 and controls the heating element 250 and / or the cooling elements 260, 270 depending on the temperature information.

[0031] Fig. Figure 3A shows a portion of a carrier 350 configured to receive multiple sets 50 as previously described with reference to Fig. 1B. The carrier 350 has an opening 351 and a step 352 adapted to receive a single set 50 as shown in Fig. 1B is shown. As shown in Fig. As can be seen in Figure 3B, the set 50 with the solder 23 arranged between the first soldering partner (in the present example, a base plate 8) and the second soldering partner 10 (in the present example, the substrate 2, which carries the semiconductor chips 1 soldered thereto) is positioned above the opening 351. Until then, there is no soldered connection between the substrate 2 and the base plate 8.

[0032] After the clamp 353 has been moved downwards towards the carrier 350, the set 50 is held by the clamp 353 within the step 352, which in Fig. 3C. The clamp 353 can exert a contact pressure on the upper surface 8t of the base plate 8 or on the upper surface of the substrate 2.

[0033] Integrated into the clamp 353 are an electrically conductive first contact element 354 and an electrically conductive second contact element 355, which electrically contact the upper side 8t of the base plate 8 or the upper metallization 21 of the substrate 2.

[0034] According to one embodiment, the first contact element 354 and the second contact element 355 can be made of different materials, so that as soon as both contact elements 354, 355 electrically contact the same electrically conductive part, a first contact potential difference develops between the first contact element 354 and the electrically conductive part, and a second contact potential difference develops between the second contact element 355 and the electrically conductive part. For example, the electrically conductive part can be the base plate 8, the upper metallization 21 of the substrate 2, or an upper metallization of one of the power semiconductor chips 1. The difference between the first contact potential difference and the second contact potential difference is then a measure of the temperature of the electrically conductive part.

[0035] According to another embodiment, the first contact element 354 and the second contact element 355 may be made of different materials, although this is not necessarily required. In this example, both contact elements 354, 355 contact terminals of a temperature sensor element that is thermally coupled to a specific location of the set 50.

[0036] As in Fig. 3D, a temperature sensor element 356 can be integrated into a power semiconductor chip 1, and / or a temperature sensor element 357 can be attached to the substrate 2 or the base plate 8. This allows the contact elements 354, 355 to tap a signal provided by the respective sensor element 356 or 357. Some of the electrical connections between the terminals of the temperature sensor elements 356, 357 and the contact elements 354, 355 can be realized using conductive tracks formed in the upper metallization 21 of the substrate 2. For example, the sensor element 356 can be a diode, and the sensor element 357 can be any desired temperature sensor element, such as an NTC resistor (NTC = negative temperature coefficient), a PTC resistor (PTC = positive temperature coefficient), or a thermocouple, etc.

[0037] Fig. Figure 4 is a sectional view of parts of a soldering system 200, which shows, by way of example, a heating chamber 211, 212, 213, as well as a receiving and control unit 230. Furthermore, at least one cooling chamber is present, which, however, is not shown for the sake of simplicity. Two sets 50 are arranged on the support 350, as previously described with reference to Figures Fig. 3A to 3D. Below the carrier 350 is a heating element 250 with a single inductor. The inductor can be designed like a coil with one or more turns. When the inductor is connected to an electric current, an electromagnetic field is formed and causes eddy currents in the base plates 8 located above it (shown in black), which leads to a temperature increase of the base plate 8, the solder 23 and the solder 23 connected to the power semiconductor chips 1 (see the Fig. 3B to 3D). Each of the sets 50 is assigned a radio transmitter 300. Each of the radio transmitters 300 transmits a signal containing information about the temperature of the respective set 50 to the common receiving unit 231. Subsequently, the control unit 232 evaluates the temperature information from both sets 50 and maintains, reduces, or increases the intensity of the alternating current depending on the temperature information.

[0038] The order according to Fig. 4B differs from the arrangement according to Fig. 4A in that a common radio transmitter 300 is provided which transmits the temperature information from both sets 50.

[0039] Fig. 5A shows a sectional view of parts of a soldering system 200, which shows, by way of example, a heating chamber 211, 212, 213 and a receiving and control unit 230. Furthermore, at least one cooling chamber is provided following the last 213 of the heating chambers 211, 212, 213, although this is not shown to simplify the illustration. On the carrier 350, as previously described with reference to Fig. 3A to 3D, three sets 50 are arranged. As in the arrangement according to Fig. 4A, the temperature information of each set 50 is transmitted individually to the common receiving unit 231 by means of different radio transmitters 300 and evaluated by the control unit 232.

[0040] Below the carrier 350 is a heating element 250 with at least two inductors 250. Each of the inductors 250 can be designed like a coil with one or more turns. Each of the inductors 250 is arranged below one or exactly one of the sets 50, so that when the respective inductor 250 is supplied with an alternating current, a temperature increase is caused only in the respective set 50 (stray effects are not significant and can be neglected). Therefore, the various inductors 250 can be individually controlled depending on the temperature information associated with the respective set 50, which is arranged above the respective inductor 250. This means that the heating of one set 50 can be controlled individually and independently of the other sets 50 and can therefore be individually adapted to specific requirements of the soldering process.

[0041] The order according to Fig. 5B differs from the arrangement according to Fig. 5A in that a common radio transmitter 300 is provided which transmits the temperature information of all sets 50 located in the heating chamber 211, 212, 213.

[0042] Fig. 6A is a plan view of a carrier 350 arranged in a soldering system and having a number of openings 351. Each of the openings 351 is designed to receive a set of components to be soldered. An individual radio transmitter 300 is provided for each of the openings 351, i.e., for each of the sets 50 to be inserted into the openings 351. Once the carrier 350 is equipped with a number of sets 50, it can be moved between different heating and cooling chambers without interrupting the radio transmission of the temperature information via the sets. Since no set has yet been inserted into the carrier 350, the inductors 250 located below the openings 351 of the carrier 350 can be seen, each of which is individually assigned to one and only one of the openings 351.

[0043] Fig. 6B shows the carrier 350 according to Fig. 6A, wherein the openings 351 are as previously described with reference to the Fig. 3A to 3D explained are equipped with sets 50.

[0044] The Fig. 7A differs from the carrier 350 according to Fig. 6A in that only one common radio transmitter 300 is provided instead of a plurality of radio transmitters. A first and second contact element is integrated into each of the clamps 353, as described above with reference to the Fig. 3A to 3D. All first and second contact elements are connected to the same radio transmitter 300 via electrical connecting lines 301, 302.

[0045] Fig. 7B shows the carrier according to Fig. 7A, wherein the openings 351 are as previously described with reference to the Fig. 3A to 3D are equipped with sets 50. The radio transmitter 300 transmits the individual temperature information from all sets 50 together to a common receiving unit 231.

[0046] Fig. 8A is a sectional view of parts of a soldering system 200, which has, by way of example, a cooling chamber 222 and a receiving and control unit 230. Furthermore, at least one heating chamber is provided preceding the cooling chamber 222, although this is not shown for simplicity of illustration. As previously described with reference to FIG. Fig. 3A to 3D, three sets 50 are arranged. As with the arrangements according to the Fig. 4A, Fig. 5A and Fig. 6B, the temperature information for each of the sets 50 is transmitted individually by different radio transmitters 300 to the common receiving unit 231 and evaluated by the control unit 232.

[0047] Below the carrier 350 is a cooling element 270, which comprises a number of cooling plates 270. The cooling plates 270 can be moved independently of each other upwards towards the sets 50, as well as downwards, which in Fig. 8A is indicated by black double arrows. The movement of the cooling plates 270 can be controlled independently of one another by the control unit 232. If a cooling plate 270 is required to cool the set 50 assigned to it, the cooling plate 270 is moved upwards toward the respective set 50 until it thermally contacts the base plate 8, so that a heat flow develops from the respective set 50 toward the cooling plate 270.

[0048] The order according to Fig. 8B differs from the arrangement according to Fig. 8A in that a common radio transmitter 300 is provided which transmits the individual temperature information of each of the sets located on the carrier 350 to the receiving unit 231.

[0049] Instead of cooling plates 270, the cooling of the sets 50 can also be achieved by one or more controllable jets of a cooling fluid, for example, air or another gas. If only one jet of a cooling fluid is provided, this jet can act on all sets 50 located in the cooling chamber 222. In this case, the cooling can be controlled by a single cooling jet depending on the temperature information about all sets 50 located in the cooling chamber 222, as described with reference to the Fig. 4A and Fig. Heating by a single inductor as described in Figure 4B.

[0050] However, it is also possible to provide an individual jet of cooling fluid for each of the sets 50 located in the cooling chamber 222, ie a jet that acts individually on one and only one of the sets 50. In this case, the cooling by individual cooling jets can be controlled in the same way depending on the temperature information about all sets 50 located in the cooling chamber 222, as described with reference to the Fig. 5A and Fig. Figure 5B explained heating by the individual inductors.

[0051] If it is desired to identify the individual sets 50, for example if each of the sets is to be labelled with its individual temporal profile of the temperature in the soldering system after completion of the soldering process, in an arrangement in which each of the sets 50 is assigned a label as described above with reference to the Fig. 5A, Fig. 5B, Fig. 6A, Fig. 6B, Fig. 7A, Fig. 7B, an individual inductor 250 is assigned, all inductors 250 are temporarily supplied with electrical energy one after the other, so that a significant temperature increase occurs in one of the sets. By monitoring the temperature of all sets 50, it can thus be clearly determined that the one of the sets 50 showing a significant temperature increase has been heated by the electrical energy, and can thus be assigned to the respective inductor 250.

[0052] By repeating this process successively for all inductors 250 and with sufficient time intervals to avoid resolution problems, each of the sets 50 can be assigned to a different one of the inductors 250.

[0053] If unreasonable temperature information is transmitted, it may be concluded that there is a fault in a temperature sensor, an electrical connection, or a transmission, or that one or more of the openings are not equipped with a set 50.

[0054] Fig. Figure 9 shows a carrier 350 arranged in a cooling chamber 221. The carrier 350 has a number of openings 351, each of which is configured to receive a set 50 of components to be soldered together. An individual RF radio transmitter 300 is provided for each of the openings 351.

[0055] Fig. Figure 10 shows a carrier 350 which extends from the carrier according to Fig. 9 in that a common radio transmitter 300 is provided for the sets 50 of components to be soldered together instead of individual radio transmitters.

[0056] The heating and cooling processes described above can be combined in any way. For example, with reference again to Fig. 2, a first heating step is carried out in a first heating chamber 211 in order to preheat each of the sets 50 approximately to a first temperature which is lower than the melting point of the solder 23. In a subsequent second heating step, which is carried out when the sets 50 are located in a second heating chamber 212 following the first heating chamber 211, the temperature of each of the sets 50 can be increased approximately to a second temperature which is higher than the first temperature, but still lower than the melting point of the solder 23. Optionally, the surfaces of the soldering partners to be soldered can be activated in an atmosphere which contains forming gas, formic acid or the like.

[0057] Then, in a subsequent third heating step, which is carried out when the sets 50 are located in a third heating chamber 213, the temperature of each of the sets 50 can be increased to a third temperature that is above the melting point of the solder 23, so that the solder 23 of the respective set 50 is melted. Optionally, the third heating step can be carried out at a low gas pressure, for example, below 20 hPa, in the third heating chamber 213 to prevent the occurrence of shrinkage cavities in the solder joint.

[0058] In a subsequent first cooling step, which is carried out when the sets 50 are in a first cooling chamber 221, the temperature of each of the sets 50 can be reduced to a fourth temperature which is lower than the melting point of the solder 23, so that the solder 23 of the respective set 50 solidifies.

[0059] Then, in a subsequent second cooling step, which is carried out when the sets 50 are in a second cooling chamber 222, the temperatures of the sets 50 can be slowly reduced to a fifth temperature, which is lower than the fourth temperature, so that thermomechanical stresses in the soldered assemblies are avoided. The transport of the sets 50 between the chambers 211, 212, 213, 221, 222 of the soldering system can be carried out in such a way that the sets 50 remain on the same carrier 350 throughout the entire soldering and cooling process.

[0060] Fig. 11 shows a power semiconductor module 100 which differs from the power semiconductor module according to Fig. 1A in that the substrate 2 itself forms a base plate of the module 100 instead of a thick metallic base plate 8. The substrate 2 is connected to the module housing 4 by means of an adhesive 7. The substrate 2 has two or more metallization layers 21, 22 and one or more insulation supports 20, with at least one of the insulation supports 20 being arranged between any two metallization layers 21, 22. Since the substrate 2 serves as a base plate, the underside of the lowest metallization layer 22 of the metallization layers 21, 22 of the substrate 2 forms an outer surface of the power semiconductor module 100.

[0061] Fig. Figure 12 shows a sectional view of a set with two soldering partners during the soldering process. The first soldering partner is a substrate 2, and the second soldering partner is a power semiconductor chip 1. The set is inserted into a carrier 350. Soldering is carried out by means of an inductor 250, which generates eddy currents, particularly in the bottommost metallization layer 22 of the substrate 2. These eddy currents melt the solder 11 between the substrate 2 and the power semiconductor chips 1. Apart from the fact that there is no thick metallic base plate, the soldering process and the subsequent cooling process can be carried out in the same way as described above with reference to the Fig. 2 to 10. The assembly produced in the soldering process can be used to manufacture a power semiconductor module 100, as previously described with reference to Fig. 1, and equally well for the production of a power semiconductor module 100 as previously explained with reference to Fig. 11 was explained.

[0062] The directional terminology used in this application, such as "below," "above," "lower," "upper," and the like, is intended to facilitate description and to indicate the positioning of one element relative to a second element. These terms also include orientations of the illustrated arrangements other than those shown in the figures. Furthermore, terms such as "first," "second," and the like are also used to identify various elements, regions, sections, etc., and are therefore not intended to be limiting in terms of order. Furthermore, like terms refer to like or corresponding elements throughout the specification.

Claims

[1] Soldering process with the steps: Providing a soldering system (200) comprising a heating chamber (211, 212, 213) with an inductive heating unit (250) designed to provide energy, and a cooling chamber (221, 222) with at least one cooling device (270); Providing at least two sets (50) of components (1, 2, 8) to be soldered together, each of the sets (50) comprising a first soldering partner (1, 2) and a second soldering partner (2, 8) as well as a solder (11, 23); positioning each of the sets (50) of components (1, 2, 8) in the heating chamber (211, 212, 213) such that the solder (11, 23) is arranged between the first soldering partner (1, 2) and the second soldering partner (2, 8); for each of at least two of the two sets (50): providing a temperature measuring unit that is individually assigned to the respective one of the two sets (50), wherein each of the temperature measuring units is integrated into one of the components (1, 2, 8) of the corresponding set (50) and / or attached to one of the components (1, 2, 8) of the corresponding set (50); Providing at least one radio transmitter (300) and one radio receiver (231); Providing a control unit (232) coupled to the radio receiver unit (231) and configured to control the inductive heating unit (250); for each of the temperature measuring units: transmitting information about the temperature of one of the components (1, 2, 8) of the corresponding set (50) measured by the temperature measuring unit in question to the radio receiving unit (231) using the radio transmitter (300); Heating the sets (50) of components (1, 2, 8) by energy provided by the inductive heating unit (250); Controlling the energy supplied by the inductive heating unit (250) depending on the temperature information; Transferring all batches (50) of components (1, 2, 8), after the solders (11, 23) of all batches (50) have been heated at least to their respective melting points, from the heating chamber (211, 212, 213) to the cooling chamber (221, 222); and Cooling of the sets (50) of components (1, 2, 8) by the cooling device (270) by controlling the cooling device (270) depending on the temperature information. [2] Soldering method according to claim 1, wherein the temperature information is continuously or quasi-continuously monitored during the heating of the sets (50) of components (1, 2, 8). [3] Soldering method according to one of the preceding claims, wherein a first of the temperature measuring units comprises an electrically conductive first contact element (354) and an electrically conductive second contact element (355). [4] Soldering method according to claim 3, wherein the electrically conductive first contact element (354) and the electrically conductive second contact element (355) are made of different materials; the first soldering partner (1, 2) or the second soldering partner (2, 8) of the set (50) to which the first of the temperature measuring units is assigned is designed as an electrically conductive part or has an electrically conductive part; Both the electrically conductive first contact element (354) and the electrically conductive second contact element (355) make pressure contact with the electrically conductive part; and the temperature information for the temperature detected by the first of the temperature measuring units depends on a first contact potential difference between the electrically conductive first contact element (354) and the electrically conductive part, as well as on a second contact potential difference between the electrically conductive second contact element (355) and the electrically conductive part. [5] Soldering method according to one of claims 3 or 4, wherein one of the soldering partners (1, 2, 8) of the set (50) to which the first temperature measuring unit is assigned has a temperature measuring element or is coupled to one which is electrically connected by pressure contact directly or indirectly to both the electrically conductive first contact element (354) and the electrically conductive second contact element (355). [6] Soldering method according to one of the preceding claims, wherein the inductive heating unit (250) is an inductor which supplies energy to at least two of the sets (50) of components (1, 2, 8) during the heating of the sets (50). [7] Soldering process according to one of the preceding claims, wherein the inductive heating unit (250) comprises at least two inductors; each of the inductors is assigned to a different set (50) of components (1, 2, 8); and Each of the inductors individually supplies energy to a different set (50) of components (1, 2, 8) and only to that set (50) during the heating of the sets (50). [8] Soldering method according to one of the preceding claims, wherein for each of the different sets (50) of components (1, 2, 8) a separate radio transmitter (300) is provided which is assigned to the set (50) in question. [9] Soldering method according to claim 8, wherein each of the radio transmitters (300) is configured to transmit temperature information about the temperature of the set (50) to which it is assigned, but not about the temperature of any of the other sets (50). [10] Soldering method according to claim 9 comprising the sequence of steps: (a) temporarily increasing the energy supplied by one and only one of the inductors, so that only the set (50) associated with that inductor is heated briefly; (b) Comparing the temperature information transmitted by each of the radio transmitters (300) and determining which of the temperature information shows a maximum temperature increase; and (c) Assigning the radio transmitter (300) that transmitted the temperature information showing the maximum temperature increase to the inductor at which the supplied energy was increased. [11] Soldering method according to claim 10, wherein the sequence of steps (a) to (c) is repeated for each of the inductors. [12] Soldering method according to any one of claims 1 to 11, wherein the temperature information of each of the sets (50) is continuously or quasi-continuously monitored while the sets (50) are transferred from the heating chamber (211, 212, 213) to the cooling chamber (221, 222). [13] Soldering method according to any one of claims 1 to 12, wherein the temperature information of each of the sets (50) is continuously or quasi-continuously monitored during the cooling of the sets (50). [14] Soldering method according to any one of claims 1 to 13, wherein the cooling device (270) is designed to to provide a cooling airflow that cools at least two of the sets (50) of components (1, 2, 8); or to provide at least two cooling air streams, each of which is individually assigned to one and only that set (50) of components (1, 2, 8) and which cools only that set (50) of components (1, 2, 8); or to provide at least two cooling plates, each of which is individually assigned to one and only that set (50) of components (1, 2, 8) and which cools that set (50) of components (1, 2, 8). [15] Soldering process according to one of the preceding claims, wherein the solder (11, 23) of each of the sets (50) of components (1, 2, 8) is melted and subsequently solidified, so that a solid solder joint is formed between the first soldering partner (1, 2) and the second soldering partner (2, 8); and after the solder (11, 23) of each of the sets (50) of components (1, 2, 8) has melted and before the solder (11, 23) of each of the sets (50) of components (1, 2, 8) is subsequently resolidified, the solder (11, 23) of each of the sets (50) of components (1, 2, 8) is exposed to a reducing atmosphere at a pressure of less than 20 hPa.

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