Multi-press cylinder device of a sintering or diffusion apparatus, sintering or diffusion apparatus, and method for operating said device

Abstract

The invention relates to a multi-press cylinder device (18) of a preferably gas-tight sintering or diffusion apparatus (10), in particular for use as a lower and / or upper press tool (14, 16) in a process chamber of the sintering or diffusion apparatus (10), which process chamber can be subjected to a process atmosphere and can preferably be vacuumed. The multi-press cylinder device (18) comprises at least two adjacent press cylinders (20) having movable press pistons (22) for generating an adjustable pressing force of a sintering or diffusion application on a workpiece (12) or product associated with the respective press cylinder (20). The pressing force of each press cylinder (20) can be separately controlled. Each press cylinder (20) can be heated at least indirectly by means of a basic heating system (24). According to the invention, a displacement measuring system (28) of the displacement path of the press piston (22) is associated with each press cylinder (20), wherein preferably, a booster heating system (30) is also associated with each press cylinder (20), said booster heating system being arranged in the plunger region (31) of the press piston (22). The invention further relates to a method for operating the aforementioned multi-press cylinder device (18) and to a corresponding sintering or diffusion apparatus (10) having a process chamber comprising said multi-press cylinder device (18).

Description

[0001] MULTI-PRESS CYLINDER DEVICE OF A SINTERING OR DIFFUSION DEVICE, SINTERING OR DIFFUSION DEVICE AND METHOD FOR ITS OPERATION

[0002] The present invention relates to a multi-press cylinder device of a sintering or diffusion device, a method for operating a multi-press cylinder device and a sintering or diffusion device for simultaneously joining workpieces / products of several adjacently arranged electronic assemblies by means of pressure sintering.

[0003] STATE OF THE ART

[0004] In pressure sintering or diffusion brazing, two or more workpieces / products, especially electronic components and substrates, can be electrically and / or thermally connected to each other using a joining material, whereby the joining material is sintered or diffusion brazed. The workpieces / products to be joined are pressed uniaxially between an upper and a lower tool to provide the necessary joining pressure.

[0005] It has been found that joining under a process atmosphere, especially under reduced pressure or vacuum, is particularly advantageous, especially for suppressing undesirable chemical reactions such as oxidation, preventing gas inclusions, and eliminating impurities. The heat required for sintering is generally transferred to the workpieces / products via the upper and lower dies, but can also be applied as radiant heat from the top and / or bottom surfaces. Often, several components are to be arranged on a common substrate, which may differ in both their lateral dimensions and height. To ensure uniform pressure transmission, multiple press dies can be provided on the upper and / or lower die, their dimensions matched to the workpieces / products to be joined.If various assemblies of different types are to be processed on a single machine, the press die arrangement on the upper and / or lower tool regularly needs to be adjusted. This adjustment is time-consuming and made more difficult by the fact that the tools and / or press dies can be hot. Furthermore, the tools, especially the press dies, are usually made of metal because they must withstand high compressive forces. Therefore, such tools are heavy, cool down slowly, and are expensive. In addition, precise alignment of the tools or press dies with the workpieces / products to be joined is essential.A multi-press cylinder system of this type, also known as a multi-drive press system, which will be offered on the market under names such as PINK SIN 100 Sintering Module or PINK SIN 20 Multi-Drive Sintering System, is particularly suitable for system sintering of mold modules onto copper or aluminum heat sinks, or hybrid heat sinks, made of various metals and / or metals and plastics, especially closed or open heat sinks for SiC / IGBT / GAN (gallium nitride) or mixed semiconductors in various power levels from high-power to low-power traction inverters. This can be carried out as part of system sintering of a power module, which may have been manufactured in a preliminary process using injection molding. In the preliminary process, the power electronics can be sealed under a dielectric material that provides extremely good protection for the components.The result is a very robust, cost-effective, and reliable electronic component, which, however, is sensitive to temperature and humidity. The power module typically consists of at least three overmolded half-bridges and forms, for example, the core of an inverter system that controls both the drive energy and energy recovery (recuperation) in high-voltage electric vehicles, but can also be used in the generation of renewable energy in the wind or solar sector. Examples of such power modules include the "smart semiconductor-based switch" power modules developed by KYOCERA AVX for inverter applications in voltage ranges of 48 V, 470 V, 810 V, or 1200 V.Furthermore, such sinterable or diffusion-solderable power modules can first be prepared for everyday use using an overmolding technique (transfer molding process) to ensure robustness, and then sintered or diffusion-soldered onto a common heat sink, usually as a pair of three for three-phase applications, using a multi-press cylinder device. PNK-8402WO 17.10.2025 DE 102021126716 B3 and WO 2023 / 061872 A disclose a test system for process development and optimization that can perform a sintering or diffusion soldering process to join workpieces / products such as: • semiconductors on ceramic substrates and on leadframes • substrates on base plates • copper substrates without oxidation • chip top-side contacts • high-power LEDs. The system is particularly suitable for joining cooling elements such as cooling plates with power semiconductors such as IGBTs. These are found particularly in electrical energy conversion and electrical motor conversion, such as...Sintering processes are widely used in wind turbines and electric vehicles. The resulting advantages include: • Sintering of different layouts without changing the upper tool • Multi-layer sintering • High flexibility and control of the sintering atmosphere • Processing under an inert or reducing atmosphere. In addition, sintering and diffusion brazing processes are known from WO 2024 / 042155A, in which a flexible press punch configuration is enabled by arranging press punches on the workpieces / products before they are placed in the process chamber. Flexible multiple press punch configurations are also known from WO 2023 / 062116 A2. A problem with multi-press applications is the potential for inconsistencies in the pressing pressures and temperatures of adjacent press cylinders, particularly due to aging. This can lead to irregularities in ensuring consistent production results and thus to fluctuations in product quality.Particularly with increasing age or operating time of the corresponding system, production quality often decreases due to the increased severity of the aforementioned inconsistencies associated with wear. Furthermore, the process times, caused in part by the interventions necessary to correct these inconsistencies, are often too long, especially for flow production. PNK-8402WO 17.10.2025 In addition, thermal distortion of the workpieces or the workpiece carrier makes it difficult to ensure identical joining qualities of adjacent workpieces. It is an object of the invention to provide a multi-press cylinder device for a sintering or diffusion unit, a method for operating a multi-press cylinder device, and a sintering or diffusion unit that allows for optimized and time-efficient process control of a sintering or diffusion brazing process with regard to the aforementioned problems.DISCLOSURE OF THE INVENTION The problem is solved by a multi-press cylinder device comprising a sintering or diffusion device, a method for operating a multi-press cylinder device, and a sintering or diffusion device having the features of the independent claims. Preferred embodiments are specified in the dependent claims.The invention relates to a multi-press cylinder assembly according to the invention for a preferably gas-tight sintering or diffusion device, in particular for use as a lower and / or upper press tool in a process atmosphere-adjustable, preferably vacuum-sealed, process chamber of the sintering or diffusion device, comprising at least two adjacent press cylinders with movable press pistons for generating an adjustable pressing force of a sintering or diffusion application on a workpiece or product assigned to the respective press cylinder, wherein the pressing force of each press cylinder is separately controllable and wherein each press cylinder can be heated at least indirectly by a basic heating element. It is proposed that each press cylinder be assigned a displacement measuring system for the travel of the press piston. In particular, each press cylinder further comprises a booster heater arranged in the ram area of ​​the press piston.Both the displacement measuring system and the booster heating system advantageously provide a solution for correcting inequalities in the pressing pressures and / or temperature loads of adjacent press cylinders. Both solutions can work synergistically, with the displacement measuring system being preferred for the precise control of the piston's extension stroke. PNK-8402WO 17.10.2025 The displacement measuring system enables monitoring and verification of the individual travel distance of each press cylinder. The travel distance correlates with the corresponding pressure applied to the respective press cylinder. If there are inequalities in pressure between the individual press cylinders, this results in individually different travel distances, which can be detected by the displacement measuring system.This allows for individual pressure adjustments to each press cylinder via hydraulic valves and / or by adjusting the hydraulic pressure or the speed of a hydraulic pump, ensuring a uniform travel and thus press pressure for all press cylinders and guaranteeing consistent product quality. Simply put, inconsistencies in individual pressure settings or travel distances are effectively corrected by monitoring with the displacement measuring system and the associated individual pressure adjustments. The booster heater also enables individual thermal adjustment of individual press cylinders or their punch sections to correct process inconsistencies. Thermally induced inconsistencies, for example,Fluctuations in the heat distribution of a base heating system (at least indirectly acting) and the respective thermal expansion and / or material-related heating capacities can be corrected by individual heating using the booster heater. For example, if a press cylinder expands less than a neighboring press cylinder due to material variations, wear, or its arrangement and the associated greater heat dissipation, it can be additionally heated using the booster heater to compensate. Similarly, if one press cylinder is assigned a workpiece that expands less or more than another, the resulting distortion or difference in the individual travel paths can be corrected by individual reheating. Thus, the displacement measuring system and, if necessary, the booster heater can be used to determine the optimal operating parameters.The booster heating system can advantageously counteract the problem discussed at the outset, with both solutions being able to act synergistically and thus being particularly effective in combination. The respective press cylinders can be driven hydraulically, but also electrically, in particular by electric motors or electromagnetically. Preferably, a single hydraulic pump can provide hydraulic pressure for all press cylinders, whereby the hydraulic pump used for this purpose can advantageously be speed-controlled. PNK-8402WO 17.10.2025 In an advantageous embodiment, the displacement measuring system can have a measuring accuracy of less than 500 µm, preferably less than 30 µm, in particular less than 15 µm, and specifically less than 10 µm, and is preferably designed as a non-contact displacement measuring system, in particular as an optical, magnetic, or capacitive displacement measuring system.The displacement measuring system can, for example, be an optical laser displacement sensor with a maximum acquisition time of 1.5 ms and a measuring range of 65 to 135 mm, exhibiting a linearity of 0.1%, such as the LAR series from WayCon Positionsmesstechnik GmbH. Alternatively, a capacitive or magnetic displacement measuring system with comparable accuracies can be used, such as a digital magnetic tape displacement sensor from the MX series by WayCon. Ultrasound-based displacement measuring sensors are also a possibility. The higher the measuring accuracy, the more precise the measurement-based control of the travel distance or pressure application can be. This advantageously enables precise monitoring and control, while providing wear-free, thermally insensitive, robust, and non-contact displacement measurement over extended service lives.The displacement measuring system essentially determines the travel distance of the press piston within the press cylinder and can, for example, measure the distance between the ram and the press cylinder. In an advantageous embodiment, the displacement measuring system can be arranged on the base of the press cylinder and detect the distance between one end of the piston rod and the base of the press cylinder. In this structurally advantageous mounting position, the displacement measuring system can fully and optimally detect and monitor the travel distance. Furthermore, this mounting position is easily accessible and is generally not blocked by other components of the multi-press cylinder assembly, so that the corresponding measuring area can be monitored unimpeded and without interference. This advantageously ensures simple installation and interference-free measurement.Generally, a global pressure can be regulated by the pressure output of a hydraulic pump, in particular by the rotational speed of the hydraulic pump. For this purpose, each press cylinder has an individually controllable shut-off valve to regulate the hydraulic pressure in the press cylinder. In an advantageous embodiment, each press cylinder can include a pressure sensor configured to detect the pressing pressure exerted by the press piston on the workpiece / product, and preferably, each press cylinder can be assigned at least one pressure or shut-off valve for the controllable adjustment of a pressing pressure. A shut-off valve allows for a binary switching on or off of the hydraulic pressure, while a pressure valve allows for proportional pressure adjustment up to the maximum hydraulic pressure.The pressure sensor can be designed as a precision sensor in ranges up to 100 bar, preferably up to 60 bar, and with accuracies up to 0.05% across the entire pressure measuring range, in particular of the WIKA precision pressure transmitter type P-30. In addition to the respective travel distance, the individual press pressure of each cylinder can also be monitored using the pressure sensor, thus providing a dual verification option. Therefore, it is not strictly necessary to calculate the press pressure from the measured travel distance; it can also be monitored directly. A hydraulic valve allows for precise and targeted pressure adjustment or correction of the press pressure of each cylinder, enabling quick and effective readjustment of the pressure of each cylinder as needed. This advantageously allows for particularly efficient and precise correction of any discrepancies.The basic heating system can be designed to heat all press cylinders directly. However, it has proven structurally advantageous to heat only the outer press cylinders directly via a basic heating system, particularly the front and rear press cylinders, and to heat inner or intermediate press cylinders indirectly through the heat-conducting properties of the cylinder block. In an advantageous embodiment, the basic heating system can be designed as a common heating sleeve for at least two adjacent, and in particular all, at least the outermost press cylinders, with each press piston being slidably guided by the heating sleeve and being able to be heated at least indirectly for basic temperature control. In this respect, the basic heating system encompasses all press cylinders or their press pistons. Advantageously, the basic heating system is designed to be both efficient and cost-effective.In an advantageous embodiment, the base heating element can be designed as an electric heater or as a fluid heater, in particular using water or oil as the heating fluid. Both embodiments provide effective and low-loss heat transfer, thus enabling fast and efficient heating. Therefore, both embodiments are advantageously energy-efficient and cost-effective. In an advantageous embodiment, the booster heater can be designed as an electric heater, PNK-8402WO 17.10.2025, in particular as a ceramic heating element. The electric design enables fast and precisely controllable heating and provides high robustness and mechanical load capacity. Furthermore, it is advantageously a cost-effective and energy-efficient embodiment.By designing the booster heater as a lightweight, mass-reduced heating element with high specific heat density, it can, for example, be charged to a temperature higher than the sintering process temperature in a short time, thus enabling a dynamic thermal heating ramp. The temperature gradient can be specifically adapted to the sintering process temperature. This is particularly important when in contact with a cooler workpiece containing mass, as this allows the superheated temperature to drop relatively quickly. Alternatively, the booster heater can, for example, provide a lower temperature than the sintering process temperature. During the sintering process, a temperature gradient can be dynamically set towards the process temperature to control the heating ramp in a time-optimized manner.Thus, temperature control can be provided for different die geometries and die and workpiece masses, for a multitude of temperature requirements, and for various temperature gradient requirements. This makes it possible to compensate for the mass ratios of the dies, workpiece carriers, components, and workpieces, and to achieve a uniform and repeatable process result even under heterogeneous boundary conditions. Length-variable thermal contact elements for transferring contact heat, even in the case of thermally induced mechanical distortion between two components, are known from WO2016 / 091962A1. These contact elements can be used, preferably for basic heating, to transfer heat to the press cylinders and, if necessary, to a workpiece carrier or workpieces.In an advantageous embodiment, the booster heater can be thermally contacted with the underside of the workpieces / products by means of length-variable thermal contact elements, in particular spring-loaded contact elements. The possibility of length variation allows the booster heater and its heat transfer potential to be optimally adjusted to the individual mechanical characteristics of the individual press cylinders, especially individual differences in length or expansion. Advantageously, this ensures reliable and efficient heating. PNK-8402WO 17.10.2025 In an advantageous embodiment, the booster heater can include a temperature sensor configured to detect a temperature in the punch area of ​​the cylinder piston. Preferably, the temperature sensor in the booster heater can be arranged close to the surface of the press punch in order to detect the contact temperature close to the workpiece.When the booster heater is designed as a ceramic heating element, this element can be embedded in the ceramic substrate. The temperature sensor can advantageously be designed as a sheathed thermocouple, as sheathed thermocouples differ from conventional thermocouples in their smaller size and flexibility. Due to these properties, sheathed thermocouples can also be used in hard-to-reach locations, such as in the ceramic head section of the booster heater. Thermocouples consist of two metallic conductors made of different materials and are welded together at the measuring point. In a sheathed thermocouple, the thermocouple is embedded in a highly compacted ceramic powder for protection against environmental influences and mechanical stress. Depending on the alloy of the sheath, sheathed thermocouples can be used for temperatures above 1,000 °C.In addition to their mechanical and thermal robustness, sheathed thermocouples offer the significant advantage of being very thin and flexible. This makes it advantageous to access and connect measuring points in the booster heater that are difficult to reach. In an advantageous embodiment, at least one, particularly a higher-level, control unit can be included, which is configured to set the temperature, pressure, and piston stroke of each press cylinder. In this respect, the control unit is associated with the displacement measuring system and preferably also with a booster heater, and is configured to evaluate corresponding measurement data, such as travel distance, pressure, temperature, etc., and to initiate any necessary readjustment.In particular, the control unit can control the hydraulic pump, especially its speed, and / or the respective shut-off and / or pressure valves of the individual press cylinders to adjust the individual pressure or piston stroke. The control unit can also control the individual booster heaters to individually adjust or readjust the temperature of the press cylinders as needed. Advantageously, a controllable cooling system for the hydraulic system can also be controlled by the control unit to maintain consistent hydraulic conditions. In particular, several control units can be present, each assigned to specific functions, for example, one control unit for adjusting the pressure / piston stroke and another for adjusting the temperature. This advantageously enables reliable and precise readjustment.In an advantageous embodiment, as previously indicated, a hydraulic pump, in particular a speed-controlled one, can be included, which is designed to generate and control hydraulic pressure for the pressing force of the press cylinders. Preferably, an active cooling control system is provided for the controllable cooling of the hydraulic pump, a hydraulic compensation reservoir, and / or a hydraulic fluid, in particular hydraulic oil. Alternatively or additionally, cooling can be passive, for example via one or more cooling elements. Active cooling control using active cooling elements such as fans, cooling fluid, or similar devices also enables dynamic temperature control. In this respect, the press cylinders are hydraulically driven. The cooling can preferably be provided by water cooling or liquid cooling; however, gas flow cooling, such as air cooling, is also possible.Cooling can be achieved using fans or other cooling technologies. The hydraulic pump, the hydraulic reservoir, and / or the hydraulic fluid can be actively cooled, i.e., controlled and requiring energy. Continuous operation of the hydraulic pump generates heat, which is transferred to the hydraulic fluid, warming it. The problem here is that as the hydraulic fluid heats up, the available hydraulic pressure decreases, leading to pressure loss and a corresponding reduction in pressing force. Furthermore, the correlation between hydraulic pressure and pressure changes with increasing temperature, making it more difficult to determine the hydraulic pressure by measuring the travel of the press cylinders. This negatively impacts pressure determination using the displacement measuring system.Active cooling control makes it possible to maintain the temperature of the hydraulic pump, the hydraulic expansion reservoir, and / or the hydraulic fluid within a definable temperature range. In other words, active cooling control allows the temperature of the hydraulic fluid to be maintained at the level optimal for pressure generation. Advantageously, this prevents the previously mentioned problem. PNK-8402WO 17.10.2025 In an advantageous embodiment, active cooling control can be provided by a controllable cooling device associated with the hydraulic pump and / or a hydraulic expansion reservoir. The cooling device is designed to maintain the operating temperature of the hydraulic pump or the hydraulic expansion reservoir—that is, its temperature during intended operation—within an adjustable operating temperature range.In particular, a hydraulic temperature sensor associated with the hydraulic pump and / or the hydraulic expansion reservoir can be included to monitor the temperature of the hydraulic pump and / or the hydraulic expansion reservoir. The hydraulic temperature sensor can, for example, be located in or on the motor of the hydraulic pump to detect the temperature generated there, which heats the hydraulic fluid. The controllable cooling device advantageously enables precisely controllable active cooling. With increasing temperature, a hydraulic fluid changes its hydraulic properties, usually becoming less viscous, whereby a temperature-pressure correlation influences the behavior of the hydraulic system. To be able to control this behavior, a hydraulic temperature signal from the hydraulic temperature sensor can be evaluated.The hydraulic temperature sensor provides an advantageous method for temperature monitoring, allowing the corresponding monitoring results to be considered when controlling the active cooling. This advantageously further optimizes the active cooling. In a related aspect, a method for sintering or diffusion brazing using the aforementioned multi-press cylinder device is proposed, whereby the displacement or pressure profile of each press cylinder and / or the temperature profile of each booster heater is controlled by a higher-level control system, in particular setting a uniform or individual pressure and / or a uniform or individual temperature in the ram area of ​​each press piston. This enables precise and individual readjustment to compensate for the previously discussed inconsistencies. The advantages already mentioned in this regard result.As a rule, the pressure chambers of the press cylinders can be hydraulically interconnected, so that a hydraulically identical pressure is applied to all press cylinders. In an advantageous embodiment of the method, a time-dependent characteristic curve of the pressure profile and / or the piston stroke of each press cylinder, or a group of press cylinders, and / or a characteristic curve of the temperature profile in the punch area can be set and / or recorded. This ensures that any inequalities that may exist for each PNK-8402WO 17.10.2025 press cylinder can be individually monitored and thus corrected, enabling precise compensation to ensure a consistent production result. Advantageously, individual readjustment can thus be guaranteed in the long term or sustainably. If the multi-press cylinder device is driven by hydraulic pumps, in particular...When a common hydraulic pump is operated with a speed-controlled hydraulic pump, it can be advantageous to regulate the travel distance or press pressure by precisely controlling the pump speed of the hydraulic pump. In an embodiment of the method based on the previous embodiment, the characteristic curve can be ramp-shaped, parabolic, step-like, or a predefined function, e.g., exponential or logarithmic, or according to a table. A combination of the aforementioned characteristic curve shapes is also possible. The selection or design of the characteristic curve depends on the individual requirements and intended results of the respective application. Depending on the type of characteristic curve, various application-specific advantages arise.According to a further preferred embodiment of the method, the actuation of various drive devices for moving the first and / or second press rams into the working position is staggered in time. The actuation of the various drive devices for moving the first and / or second press rams from the working position back to the rest position can occur in the same sequence, simultaneously, or in reverse chronological order. Thus, in an advantageous embodiment of the method, at the beginning of the pressing process, the central, i.e., inner, press pistons of the multi-press cylinder assembly can extend ahead of the first, followed by the extension of the outer press pistons of the multi-press cylinder assembly.Thus, the actuation of different press cylinders occurs in a staggered manner, such that at least one press cylinder located in a central area is actuated first, followed by press cylinders located further outwards at a later time interval. For example, in an arrangement of nine press pistons in three rows of three, the central press piston can be actuated first, followed by the surrounding, more outwardly located press pistons. In particular, by prematurely lifting the central component or central assemblies, a guide frame or tool carrier, as described above, can advantageously be lifted as well, and all upper press rams or upper parts of the assemblies with upper press rams contained therein can be lifted and centered before the other, peripheral press rams press.This allows for the early alignment of the assemblies relative to the upper and lower press rams or upper and lower drive devices. Advantageously, the guide frame or tool carrier comprises three groups of three assemblies each, or optionally four groups of three assemblies each, with the central drive device within each group prematurely lifting the central assembly with the upper press ram and guide frame out of the carrier frame. According to a further preferred embodiment of the method, active cooling control is implemented for a hydraulic pump, in particular a speed-controlled pump, which drives the press cylinders and provides hydraulic pressure for generating the pressing force. The temperature of the hydraulic pump and / or a hydraulic compensation reservoir is maintained within an adjustable temperature range during operation by means of controllable cooling.In particular, the temperature of the hydraulic pump and / or the hydraulic expansion reservoir is monitored by a hydraulic temperature sensor. The hydraulic temperature sensor can preferably be located in the hydraulic pump motor as the main heat source, so that the hydraulic temperature can be inferred from the motor temperature. This offers the advantages already mentioned above. In a further, secondary aspect, a sintering or diffusion device, in particular a multi-chamber device with a preheating, process, and cooling chamber, is proposed, which comprises the aforementioned multi-press cylinder assembly in a process-gas-tight, and in particular vacuum-sealed, process chamber. For this purpose, the sintering or diffusion device is configured to carry out the sintering or diffusion brazing process described above. This offers the advantages already mentioned above.In an advantageous further development of the sintering or diffusion device, a counter-tool of the multi-press cylinder assembly, designed as an upper or lower tool, can provide pressure tolerance compensation, tilt compensation, and / or thermal distortion compensation, and in particular comprises a pressure pad, a graphite foil, and / or multiple punch arrangement with a pressure compensation function. For example, a pressure pad sealed by an elastic membrane, preferably a metal membrane, in the counter-tool can provide pressure tolerance compensation and height compensation. A graphite foil can also provide distortion and height compensation in the upper tool (PNK-8402WO 17.10.2025). WO 2023 / 062116 A2 describes various possibilities for single and counter-tools with single or multiple punches with pressure pads that enable warpage compensation, pressure equalization, and / or tolerance compensation.DRAWINGS Further advantages become apparent from the drawing and the associated drawing description. The drawings illustrate exemplary embodiments of the invention. The drawings, the description, and the claims contain numerous features in combination. It is advantageous for those skilled in the art to also consider the features individually and combine them into meaningful further combinations. In particular, those skilled in the art will also apply features described in relation to embodiments of the sintering device to embodiments of the method according to the invention, and vice versa. The figures show: Fig. 1 a schematic representation of an advantageous sintering or diffusion device with an advantageous multi-press cylinder assembly with a displacement measuring system and a booster heater; Fig. 2 a perspective view of an embodiment of the multi-press cylinder assembly; Figs.Figs. 3A, 3B: Each a representation of the displacement measuring system of the multi-press cylinder device; Fig. 4: A perspective view of pressure measuring sensors of the multi-press cylinder device; Fig. 5: A schematic representation of a further embodiment of the sintering or diffusion device; Fig. 6: A schematic representation of a further embodiment of the sintering or diffusion device; Figs. 7A, 7B: Each a perspective view of the booster heater; Figs. 8A, 8B: Schematic circuit diagrams of preferred embodiments of the multi-press cylinder device; PNK-8402WO 17.10.2025; Fig. 9: A diagram of a two-point control for the force profile during operation of the multi-press cylinder device; Figs. 10A - 10G: Various characteristic curves for the temporal control of the pressure profile or the pressing force of press cylinders of the multi-press cylinder device.Figure 1 shows a simplified perspective view of an advantageous sintering or diffusion device 10. Using the device 10, two or more workpieces 12 can be electrically and / or thermally connected to one another in a generally known sintering or brazing process. This process can be carried out in a process atmosphere-adjustable process chamber of the device 10 using an upper tool 14 and a cooperating lower tool 16. During the process, the workpieces 12 are arranged in the area between the upper tool 14 and the lower tool 16 and pressed together by applying a pressing force. The pressing force can be applied by mechanically displacing the upper tool 14 and / or the lower tool 16. In this case, the lower tool 16 is pressed against the upper tool 14. The lower tool 16 is formed by a multi-press cylinder assembly 18.The multi-press cylinder assembly 18 comprises at least two adjacent press cylinders 20 with movable press pistons 22 for adjustable generation of the pressing force. The individual pressing force of each press cylinder 20 or press piston 22 can be controlled separately. Furthermore, the multi-press cylinder assembly 18 includes a base heater 24, by means of which the outer press cylinders 20, in this case the press cylinders 20 arranged to the right and left in the plane of the image, can be heated to ensure or generate the process temperature necessary for the sintering or brazing processes. Inner press cylinders 20 are thus indirectly heated by thermal diffusion from the outer press cylinders 20. The design and function of a generic multi-press cylinder assembly 18, as described above, are generally known, for example, from the aforementioned applications of the applicant.Therefore, this will not be discussed in further detail here. PNK-8402WO 17.10.2025 The repositioning of the press cylinders 20 or press pistons 22 is effected in this case by means of a hydraulic pump 26 assigned to the multi-press cylinder assembly 18 and fluidically connected to the individual press cylinders 20. A hydraulic fluid with an adjustable hydraulic pressure can be conveyed to the repositionable press cylinders 20 by means of the hydraulic pump 26 to generate the pressing force, so that they are pressed towards the upper tool 14 or the associated workpieces 12 due to the hydraulic pressure. Preferably, the press cylinders 20 are operated by a common hydraulic pump 26, as shown here. Alternatively, each press cylinder 20 can also be assigned its own hydraulic pump 26. The speed of the hydraulic pump 26 is adjustable in this case, so that the hydraulic pressure can be set particularly flexibly and precisely.Furthermore, an active cooling control system for the hydraulic pump 26 and / or one of the hydraulic compensation reservoirs associated with the hydraulic pump 26 (not shown in detail here for clarity) is provided. This active cooling control effectively counteracts the steadily increasing heating of the hydraulic pump 26, the hydraulic compensation reservoir, and / or the hydraulic fluid during continuous operation, thus preventing pressure loss. The cooling system maintains the corresponding temperature, particularly that of the hydraulic fluid, within a definable temperature range that is optimal for pressure generation and transmission. Especially with increasing age or operating time, multi-press cylinder devices 18 of this type often experience problems with inconsistencies in the individual pressing pressures.Pressing forces from adjacent press cylinders 20 and / or inconsistencies in their temperature distribution, caused at least partially and possibly indirectly by the base heating 24, can occur. These inconsistencies can result in inconsistent processing quality of the workpieces 12, for example, by adjacent workpieces 12 being pressed unevenly. To solve this problem, it is advantageously provided that the multi-press cylinder device 18 includes at least one displacement measuring system 28 and at least one booster heater 30. In this respect, each press cylinder 20 is assigned its own displacement measuring system 28, and each press cylinder 20 further comprises its own booster heater 30 arranged in a punch area 31 of the respective press piston 22. PNK-8402WO 17.10.2025 The travel distance of the respective assigned press piston 22 can advantageously be monitored by means of the displacement measuring system 28.This allows irregularities or inequalities between adjacent press cylinders 20 to be easily detected, enabling individual readjustment of the travel path of the respective press cylinder 20. Since the travel path correlates with the hydraulic pressure acting on the press cylinder 20 or press piston 22, the inequality in travel path can be precisely corrected by adjusting the hydraulic pressure acting on the respective press cylinder 20. Simply put, if it is detected that one of the press cylinders 20 or press piston 22 is not traveling far enough or is traveling too far, the corresponding hydraulic pressure can be individually increased or decreased. This detection and monitoring is possible for each individual press cylinder 20 using the respective displacement measuring systems 28.As a result, the individual travel paths of the respective press cylinders 20 are identical or consistent after appropriate readjustment, thus effectively avoiding the aforementioned inequalities. The displacement measuring system 28 is preferably designed to be wear-free, non-contact, and mechanically robust; optical, magnetic, capacitive, or acoustic displacement measuring systems with sufficiently fine displacement resolution are suitable for this purpose. In this design, each press cylinder 20 includes a pressure sensor 32, by means of which the applied pressing force or the corresponding pressing pressure of the press piston 22 on the workpiece 12 can be detected. Furthermore, each press cylinder 20 is equipped with at least one pressure or shut-off valve 34 for adjustable setting of the pressing pressure. Using the pressure sensor 32 and the pressure or shut-off valve 34 improves the ability to readjust the individual pressing pressure of each press cylinder 20.The pressure sensor 32 allows the individually applied pressing pressure of each press cylinder 20 to be directly detected, in addition to, or alternatively to, the displacement measuring system 28. The pressure valve or shut-off valve 34, in turn, enables a targeted supply or discharge of hydraulic fluid and thus individual and targeted control of the respective pressing pressure. The booster heater 30 advantageously compensates for thermally induced inequalities. Such inequalities can, for example, involve different degrees of thermally induced expansion of the individual press cylinders 20 or press pistons 22, specifically their punch sections 31, and / or thermal distortion of the individual workpieces 12, i.e., essentially different sizes of these.The booster heater 30 present in each press cylinder 20 enables individual reheating to compensate for thermal inequalities. For example, if one of the press cylinders 20 heats up or expands to a different degree due to the material and / or the size of the workpiece 12, it can be individually reheated by the corresponding booster heater 30. In this context, the booster heater 30 is provided in addition to the main heater 24. For example, it can happen that the individual press cylinders 20 are heated unevenly, particularly indirectly, by the common main heater 24 because the temperature is distributed differently due to the arrangement of the press cylinders 20.The individual booster heaters 30 enable targeted reheating of individual press cylinders 20 to compensate for this uneven distribution, so that all press cylinders 20 are heated uniformly and / or expand to the same degree. In this case, the booster heater 30 is designed as an electric heater in the form of a ceramic heating element, which is embedded in the punch area 31 of the respective press piston 22. Thus, the displacement measuring system 28 and the booster heater 30, which work synergistically, can advantageously correct or compensate for the aforementioned inequalities in pressure and thermal expansion of the press cylinders 20. According to further embodiments not shown here, however, only the displacement measuring system 28 or only the booster heater 30 may be present. Figure 2 shows a perspective view of an embodiment of the previously described multi-press cylinder device 18.According to the embodiment shown in Figure 2, the multi-press cylinder assembly 18 has four rows, each with three press cylinders 20 arranged side by side. Such a multi-press cylinder assembly 18 can, for example, be used for the manufacture of a drive train for a four-wheeled electric vehicle, each row containing three semiconductor power switching elements as a 3-phase inverter. As can be clearly seen in Figure 2, each row of press cylinders 20 has a guide unit 36 ​​through which the press pistons 22 can be guided longitudinally. As mentioned previously, individual booster heaters 30 are arranged in the respective punch areas 31 of each press cylinder 20. Each press piston 22 has a piston rod extension 38, which, as will be discussed below, can serve in particular as a suspension for the displacement measuring system 28. PNK-8402WO 17.10.Figure 3A shows a side view and Figure 3B a perspective view of a preferred embodiment of the displacement measuring system 28. According to the embodiment shown in Figure 3, the displacement measuring system 28 is designed as a laser displacement measuring system and thus as an optical displacement measuring system. Of course, alternatively, other non-contact and robust displacement measuring systems, for example based on magnetic, capacitive or acoustic principles, can be used. The displacement measuring system 28 is, as indicated in Figures 1 and 2, arranged on a base area 76 of the respective press cylinder 20 and, from there, determines one end of a piston rod 74 of the press piston 22. In this case, the arrangement is on a corresponding suspension of the piston rod extension 38. The displacement measuring system 28 is designed and arranged such that the distance between the base area 76 of the press cylinder 20 and the end of the piston rod 74 of the press piston 22 can be detected.The laser displacement measuring system 28 comprises a laser sensor 40 for distance measurement. The laser sensor 40 is mounted on a sensor holder 41 formed from several plates and screws. The design, i.e., shape and composition, of the sensor holder 41 can be individually varied and flexibly adapted to the mechanical design of the press cylinder 20 in which the laser displacement measuring system 28 is to be used. The sensor holder 41 has a sensor section 42 and a reflector section 43. The sensor section 42 and the reflector section 43 are axially displaceable relative to each other at a bearing point 44 by means of a guide rod 49, so that one of the sections 42, 43 can be displaced axially or linearly relative to the other section 43, 42 along the guide rod 49 by a defined displacement path.In this case, the guide rod 49 is slidably guided in an opening of the bearing point 44 of the reflector section 43, so that the sensor section 42 can be moved away from and towards the reflector section 43 up to the maximum length of the guide rod 49. The reflector section 43 has a reflective surface 45, which is assigned to and faces the laser sensor 40. During operation, the laser sensor 40 emits a corresponding laser line 39 in the direction of the reflective surface 45, which reflects it back for distance measurement. Based on a reflection time or a phase shift, the distance between the respective positions of the laser sensor 40 and the reflective surface 45 can be calculated using known mathematical methods. In this case, during intended assembly or operation, the sensor section 42 is fixed in a base area 76 of the respective press cylinder 20. The PNK-8402WO 17.10.Reflector section 43 is arranged on a movable part of the press piston 22, in this case the piston rod extension 38, so that the reflector section 43 is coupled to the movement of the piston rod extension 38 away from and towards the sensor section 42 in the axial direction during operation (pressing process) of the press cylinder 20. This causes the distance between the reflective surface 45 and the laser sensor 40 to vary, allowing the travel distance of the press cylinder 20 to be calculated or measured accordingly. In this case, the laser displacement measuring system 28 has a measuring accuracy of less than 15 µm to enable particularly precise detection of the travel distance. According to alternative embodiments not shown, the measuring accuracy is at least less than 500 µm. Figure 4 shows a composite representation of several examples of a preferred embodiment of the pressure measuring sensor 32.The pressure sensor 32 is a precision pressure transmitter for pressure ranges up to 60 bar and with an accuracy of up to 0.05% over the entire pressure measuring range. In this embodiment, the pressure sensor 32 is advantageously particularly small, robust, and durable, yet highly precise, making it especially well-suited for the application described. Figure 5 shows a further simplified schematic representation of another embodiment of the sintering or diffusion device 10 and the corresponding multi-press cylinder assembly 18. Identical elements are designated with the same reference symbols, and only the differences are explained below. In the embodiment shown in Figure 5, at least the outer press cylinders 20 have their own, and therefore separately operable, basic heating element 24.Therefore, no common base heater 24 is provided for each individual press cylinder 20, and only the outer press cylinders 20 can be individually heated by their own base heater 24; the inner press cylinders 20 are heated indirectly by heat conduction from the cylinder block. A further difference is that the booster heater 30 comprises length-variable thermal contact elements 46, as described, for example, in WO 2016 / 091962. These contact elements 46, which are spring-loaded in particular, allow thermal contact to be established with the underside of the workpieces 12. The contact elements 46 enable heat transfer from the booster heater 30 to the workpieces 12, adapting flexibly to the surface geometry of the workpieces 12.2025 workpieces 12, so that these, in addition to the punch area 31 of the respective press cylinder 20, can also be individually reheated to compensate for thermal distortion. Figure 6 shows a simplified schematic representation of another embodiment of the sintering or diffusion device 10 or the multi-press cylinder device 18. Again, identical elements are provided with the same reference numerals, with only the differences being explained below. The embodiment shown in Figure 6 differs from the embodiment shown in Figure 5 in that the basic heating element 24 is designed as a common heating sleeve 47 for at least two adjacent, outer, in this case all, outer press cylinders 20. Thus, a common basic heating element 24 is provided for all outer press cylinders 20.Each individual press piston 22 is slidably guided through the heating sleeve 47 and can be heated for basic temperature control. Although the previously discussed contact elements 46 are not shown in Figure 6, they can, in principle, also be present in this embodiment, as in all previous embodiments. Another difference is that a temperature sensor 48 encompassed by the booster heater 30 is shown in Figure 6. The temperature sensor 48 can, in principle, be provided in all embodiments. The temperature sensor 48 is configured to detect the temperature in the ram area 31 of the respective press piston 22. By means of the temperature sensor 48, the individual temperature of the respective ram areas 31 or press pistons 22 can advantageously be monitored and taken into account for controlling the respective booster heater 30.Therefore, the booster heater 30 can be individually and precisely controlled by means of the feedback received from the temperature sensor 48. Figures 7A and 7B each show a closer view of the piston area 31 of a press piston 22 with a view of the booster heater 30. According to the present embodiment, the temperature sensor 48 is designed as a sheathed thermocouple 50 and is centrally located in a ceramic head area of ​​the booster heater 30. With this design and positioning of the temperature sensor 48, the temperature in the piston area 31 can be detected particularly reliably, and the booster heater 30 can be controlled very precisely. In this case, a corresponding thermocouple of the sheathed thermocouple 50 is embedded in the ceramic of the heating element and is thus advantageously protected against mechanical wear and environmental influences.Supply connections 78 of a basic heating system, which is primarily electrically but also fluid-operated and can maintain the basic temperature of at least external press cylinders, are accessible from the outside. The multi-press cylinder unit 18 further comprises a control unit, not shown in detail here for the sake of clarity, which is configured to set the temperature, pressure, and / or travel of each press cylinder 28. The control unit is thus primarily associated with the displacement measuring system 28 and the booster heater 30. The control unit can also be associated with the basic heating system 24 and the hydraulic pump 26. The pressurization and heating of the press cylinders 20 can be controlled by means of the control unit, taking into account, in particular, the measured values ​​obtained from the displacement measuring system 28 or its laser sensor 40 and / or the pressure sensor 32, as well as the measured values ​​from the booster heater 30 or the temperature sensor 48, for individual adjustment.For example, if the displacement measuring system 28 and / or the pressure measuring sensor 32 detects an inequality in the pressing pressure of a press cylinder 20, the control unit can actuate the hydraulic pump 26 or the pressure or shut-off valve 34, shut-off valve 64 and other control valves 70 in such a way as to compensate for this inequality. Similarly, if the temperature sensor 48 detects that there is an inequality with respect to temperature in the ram area 31 of a press cylinder 20, the control unit can actuate the corresponding booster heater 30 for individual reheating and thus temperature equalization. In a corresponding process for sintering and / or diffusion brazing using the multi-press cylinder device 18, it is thus provided that the displacement and / or pressure profile of each press cylinder 20 and / or temperature profile of each booster heater 30 is controlled by a (superior) control unit or control system.In particular, a uniform or individual pressure and / or a uniform or individual temperature is set in the ram area 31 of each press cylinder 20. It is preferably provided that a time-dependent characteristic curve of the pressure profile and / or the piston stroke of each press cylinder 20 and / or a characteristic curve of the temperature profile in the ram area 31 is set and / or recorded. PNK-8402WO 17.10.2025 In particular, it is provided that at the beginning of the pressing process, an inner press piston 22 extends ahead of the others, followed by a time-delayed extension of outer press pistons 22 of the multi-press cylinder device 18. The aforementioned characteristic curve of the pressure profile and / or piston stroke can be individually specified or defined and / or adjusted or readjusted depending on the specific application.The characteristic curve can be ramp-shaped, parabolic, step-shaped, or a predefinable function, or can be defined according to a table, with combinations of these forms also being possible. The following section will discuss the aforementioned method using the characteristic curves, using a preferred embodiment of the inventive multi-press cylinder device 18, which can also be referred to as a multi-drive, as an example. This enables monitoring of the pressing force over time during intended operation: Figure 8a schematically shows the structure of an embodiment of a multi-press cylinder device 18. In the embodiment of the multi-drive 18, the press cylinders 20 are designed as hydraulic cylinders and are part of a servo-hydraulic drive system.This system contains pre-pressurized hydraulic oil, which is used to build up and release pressure in several tandem cylinders 56 via a hydraulic pump 26, designed as a gear pump 54 and driven by a synchronous servo motor 50. The tandem cylinders 56 each consist of two press cylinders 20 connected in series. The use of synchronous cylinders largely eliminates the need for valve technology, and the entire force process can be controlled by a continuous control system. A continuous piston rod 58 of the synchronous cylinder also provides a simple way to measure the position of the corresponding press piston 22 using the respective displacement measuring system 28. By varying the installation position of the system, the force can be applied from above or below. It is also possible to use both ends of the piston rod 58, allowing for alternating upward and downward force application.PNK-8402WO 17.10.2025 The synchronous servomotor 52, which drives the gear pump 54, is connected to a frequency converter 60. This converter controls the position of a rotor, the torque, and the speed of the synchronous servomotor 52. The frequency converter 60 is controlled by a programmable control unit 62. The control unit 62 also receives sensor data from the pressure and displacement sensors 28 and 32 and can open and close a shut-off valve 64. The control unit 62 executes a program that controls the entire system. The program functions responsible for force control and the force's temporal profile are described in detail below. The design of the gear pump 54 allows continuous operation up to a pressure of 80 bar.By employing an additional active cooling control (as discussed above), which is attached to the synchronous servomotor 52 and the gear pump 54, the generated heat can be dissipated in such a way that continuous operation up to this pressure is possible. The design of the press cylinders 20 and the hydraulic system allows operating pressures up to a maximum of 210 bar. Compliance with this maximum limit is ensured by pressure relief valves. The pressure of the hydraulic oil in the two cylinder chambers above and below the press piston 22 is measured by respective global pressure sensors 66, so that the resulting force from the differential pressure with respect to the effective area of ​​the press piston 22 can be determined with high accuracy. Depending on the piston diameter of the press cylinders 20, very controllable forces can be generated in this way, which can meet or exceed the high requirements for sintering electronic components.At an oil pressure of 80 bar in the gear pump 54, a force of 25 kN can be achieved at the piston rod 58 with two press cylinders 20 arranged in series, each with a piston diameter of 50 mm and a piston rod diameter of 22 mm. The typical pressure for the sintered pastes commonly used in this area for bonding power electronics components to a heat sink is approximately 25 MPa. At a force of 25 kN, this pressure cannot be reached for typical product sizes with an effective area of ​​the power electronics components of up to 2500 mm² during continuous operation of the gear pump 54. PNK-8402WO 17.10.2025 To achieve higher forces, the gear pump 54 is only briefly brought up to speed, and once the target force is reached, the shut-off valve 64 between the gear pump 54 and the press cylinders 22 is closed.After closing the shut-off valve 64, the pressure remains trapped in the press cylinders 22, and the force on the piston rods 58 is maintained. The gear pump 54 can be stopped again, so there is no risk of local overheating. Due to minimal leakage inside the press cylinders 20, the pressures in the upper and lower parts of the press cylinders 20 can slowly equalize, so that the acting force also decreases slowly over time. After a cooling period of several seconds, the decrease in force can be compensated for by switching the gear pump 54 back on. Figure 8b shows another embodiment of a multi-press cylinder device 18, which can also be called a multi-drive, based on the embodiment of a multi-press cylinder device 18 shown in Figure 8a.Preferably, the multi-press cylinder device 184x3 comprises press cylinders 20, with the front of each group of four parallel press cylinders 20 shown in the illustration. Additionally, this embodiment has a pressure sensor 72 and a control valve 70 for each press cylinder 20 or each group of four press cylinders 20, which allow the respective press cylinders 20 or groups of four press cylinders 20 to be controlled individually, in particular with a time delay, wherein the middle press cylinder 20 or the group of four middle press cylinders 20 is moved ahead of the outer press cylinders 20 or the outer groups of four press cylinders 20. The pressure sensors 72 allow the pressure to be individually monitored and controlled for each press cylinder 20 or for each group of press cylinders 20.The system is maintained at a desired force level by a two-point control system, schematically illustrated in Figure 9. A minimum hysteresis cannot be undercut due to leakage in the press cylinders 20 and the cooling time of the gear pump 56. Using this operating mode, a maximum force of 66.5 kN at a cylinder pressure of 210 bar is possible in this cylinder configuration. By using a hydraulic pressure intensifier 68 between the gear pump 56 and the press cylinders 20, the high cylinder pressure can also be achieved at low pump pressures. This enables continuous force control across the entire force range. The structure of typical products manufactured using such processes often consists of a mix of diverse materials, such as metals, plastics, ceramics, and semiconductors, which are spatially closely bonded.The interaction of these materials and their joints under external mechanical forces leads to complex, nonlinear reactions of the overall product, which can result in damage or even product destruction. Numerous tests have shown that the temporal profile of the external force acting on such products has a significant influence on the settling behavior and spring action of the materials used and their joints, and that therefore, controlling the temporal profile of the force plays a crucial role in the quality of the final product. The hydraulic system described above enables the continuous control of the force acting on the product via a closed-loop control system. This system allows for process control across a wide range of possible force profiles, specifically tailored to the requirements of the respective products.To achieve optimal sintering, it is necessary to apply a specific force F to the interfaces and in the sinter layer for a specific period of time t. soll at a specific temperature T soll to establish. Since the sintered layer is located inside the product, force and temperature must be applied via the product's outer surfaces. To control the force's progression over time, it is first necessary to provide the desired force setpoint for each point in the process. A function generator is implemented in the control software for this purpose, which can be structured as follows: At the start of the process, the currently acting force F0 and the current time t0 are determined as start offsets for the function's progression. Subsequently, the respective instantaneous force setpoint F is determined in a cyclic loop. tThe following target value function is calculated for the elapsed time t since the process start: PNK-8402WO 17.10.2025 Hat F t the final value F soll The setpoint generator determines the sintering force F from this point until the setpoint for the sintering force changes or until the end of the process. sollThe instantaneous force setpoint calculated in the setpoint generator is cyclically fed to the downstream control algorithm as a setpoint. The task of the control algorithm is to reduce the difference between the currently acting force on the product, determined by the pressure measurement in the press cylinder 20, and the instantaneous force setpoint as quickly as possible, ideally to the resolution limit of the measuring system, by changing the rotational speed of the hydraulic pump 26, 54. The force on the press cylinder 20, and thus on the product and ultimately on the sintered layer, is generated by the force that the pump impeller exerts on the hydraulic oil. Since the gear pump 54 inherently exhibits slippage, i.e., a certain amount of oil flows past the pump impeller, continuous rotation of the impeller is necessary to generate and maintain the force at the output of the gear pump 54.If the piston 22 can move freely within the press cylinder 20 connected to the gear pump 54, the pressure exerted on the piston 22 by the rotation of the pump impeller causes the press cylinder 20 to move in order to equalize the pressure difference in the cylinder chambers. During this movement, a corresponding quantity of oil is transported in the gear pump 54, equal to the volume of the piston stroke. If the piston rod 58 encounters an obstruction that prevents the movement of the piston 22, the pressure difference in the cylinder chambers cannot be equalized by the movement of the piston 22, resulting in a force that is transmitted to the obstruction via the piston rod 58. In this case, no more oil is transported by the gear pump 54, and the pump impeller rotates in stagnant oil.The key to controlling the force on the product therefore lies in the precise control of the pump speed, as long as the oil column between gear pump 54 and press piston 22 is not blocked by further valves. Since the losses caused by slippage depend on the pressure difference between the inlet and outlet of gear pump 54, the relationship between outlet pressure and pump speed is not linear; rather, the magnitude of the output pressure of gear pump 54 is proportional to the square root of the pump speed when there is a static back pressure in the connected system. PNK-8402WO 17.10.2025. Part of the kinetic energy of the pump impeller is converted into heat through friction in the oil, and this heating can be advantageously counteracted by a cooling device. Since no more oil flows through gear pump 54, this leads to local heating in the pump chamber. As the oil temperature increases, the viscosity of the pump oil decreases, i.e.,The oil becomes less viscous. This increases the pump's slippage, as the less viscous oil can flow more easily past the impeller. At a constant speed, this reduces the pressure at the outlet of the gear pump 54. A constant output pressure cannot be achieved with a constant pump speed unless active cooling control is in place. To generate a defined force, an integral control algorithm that continuously adjusts the pump speed based on the square of the difference between the target and actual force relative to the target force value is very well suited. The integral controller's function block is called cyclically in the software. It requires the current force, the current target force value, and a gain factor that scales the effect of the pump speed on the output force as input values. A corresponding integral controller is structured according to the following formula: This results in the following control function for the pump speed of the hydraulic pressure pump n in the control program: This control algorithm fulfills the requirements of adjusting the speed n of the gear pump 54 so that the force on the product follows the setpoint curve and the control differential can be quickly reduced to a minimum. PNK-8402WO 17.10.2025 The following discusses a number of functions as characteristic curves for setpoint specification: The simplest case for the time course of the setpoint function is the step shown in Figure 10A. With the step, the final setpoint is immediately supplied to the controller. The step is suitable for a minimum cycle time in sintering, but also leads to maximum stress on the products. The step is calculated according to the following formula: Another widely used form for the time course of the setpoint function is a linear ramp, as shown in Figure 10B. With the linear ramp, the setpoint supplied to the controller is increased by a constant value with each loop iteration, resulting in a straight line.The linear ramp results in lower stress on the products but takes a long time to reach the final setpoint. The linear ramp is calculated using the following formula: Suitable setpoint functions should exhibit a time profile that combines both positive properties of a step and a linear ramp. Two simple functions fulfill these conditions: With the quadratic function according to the parabola shown in Figure 10C, the slope of the setpoint fed to the controller is increased by a constant value with each loop iteration. This results in a gentle rise at the beginning and a steeper gradient at the end of the curve. The parabola is calculated using the following formula: If an exponential function, as shown in Figure 10D, is used to generate the force setpoint, the stress at the beginning of the process is even lower, but the slope at the end is even steeper than with a parabola.The parabola is calculated using the following formula: PNK-8402WO 17.10.2025. To dampen the transition from the steep gradient when the target force value is reached, an S-curve offers a suitable profile. The logistic function shown in Figure 10E provides a simple way to calculate an S-curve profile. The logistic function is calculated using the following formula: To specifically account for settling processes, relaxation, or similar phenomena in the material of the components, more complex force profiles and targeted holding times or gradients can be implemented by combining the functions mentioned above, as shown in Figure 10F. There, section a) corresponds to the exponential function, section b) to the linear ramp, section c) again to the exponential function, section d) to a constant force setpoint (sintering), section e) again to the exponential function, and section f) to the parabola. A further advantage of this method is its ease of use for the operator or process developer. For all described curve profiles, the coefficients can be calculated by simply specifying the target force and the time required to reach this setpoint. Another way to calculate specially shaped curve profiles is by using polynomial functions.Interpolation allows the calculation of coefficients for polynomial functions that pass through defined force points. By specifying points through which the force should pass at certain times, a function equation can be established through polynomial interpolation that is valid for the period t0 to t. F provides the desired continuous force profile. The following formula can be used to calculate the force: PNK-8402WO 17.10.2025 The coefficients k0 to k can be determined by polynomial interpolation. n The number of support points determines the degree of the polynomial required to ensure the force passes through all points. A desired distribution is shown in Figure 10G. The coefficients k0 to k nThese values ​​can be calculated using Newton's algorithm. The function generator then calculates the current target force at time t from the polynomial function. PNK-8402WO 17.10.2025 Reference List 10 Sintering or Diffusion Device 12 Workpieces 14 Upper Tool 16 Lower Tool 18 Multi-Press Cylinder Device 20 Press Cylinder 22 Press Piston 24 Base Heater 26 Hydraulic Pump 28 Position Measuring System, Laser Position Measuring System 30 Booster Heater 31 Punch Section 32 Pressure Sensor 34 Pressure Valve / Shut-off Valve 36 Guide Unit 38 Piston Rod Extension 39 Laser Line 40 Laser Sensor 41 Sensor Holder 42 Sensor Section 43 Reflector Section 44 Bearing 45 Reflector Surface 46 Contact Element 47 Heating Sleeve 48 Temperature Sensor 49 Guide Rod 50 Sheathed Thermocouple 52 Synchronous Servo Motor 54 Gear Pump 56 Tandem Cylinder 58 Piston Rod 60 Frequency Converter 62 Control Unit PNK-8402WO 17.10.2025 64 Shut-off valve 66 Global pressure sensor 68 Pressure intensifier 70 Control valve 72 Pressure sensor 74 End of a piston rod of a press cylinder 76 Bottom area of ​​the press cylinder 78 Supply connections of the basic heating system PNK-8402WO 17.10.2025.

Claims

1 Claims 1. Multi-press cylinder device (18) of a, preferably gas-tight, sintering or diffusion device (10), in particular for use as a lower and / or upper press tool (14, 16) in a process atmosphere-adjustable, preferably vacuum-sealed process chamber of the sintering or diffusion device (10), comprising at least two adjacent press cylinders (20) with movable press pistons (22) for generating an adjustable press force of a sintering or diffusion application on a workpiece (12) assigned to the respective press cylinder (20), wherein a press force of each press cylinder (20) is separately controllable and wherein each press cylinder (20) is at least indirectly heated by a basic heating element (24), characterized in that each press cylinder (20) is assigned a displacement measuring system (28) of the travel path of the press piston (22), and in particular each Press cylinder (20) one,1. A booster heater (31) is arranged in the punch area (31) of the press piston (22).

2. A multi-press cylinder device (18) according to claim 1, characterized in that the displacement measuring system (28) has a measuring accuracy of less than 500 µm, preferably less than 100 µm, in particular less than 30 µm, and specifically less than 15 µm, and is preferably designed as a non-contact displacement measuring system, in particular as an optical, magnetic or capacitive displacement measuring system (28).

3. A multi-press cylinder device (18) according to claim 1 or 2, characterized in that the displacement measuring system (28) is arranged on a bottom area of ​​the press cylinder (20) and detects a distance of one end of the piston rod (74) of the press piston (22) to the bottom area (76) of the press cylinder (20).

4. Multi-press cylinder device (18) according to one of the preceding claims, characterized in that each press cylinder (20) comprises a pressure measuring sensor (32),which is designed to detect the pressing pressure exerted by the press piston (22) on the workpiece (12), and preferably each press cylinder (20) is assigned at least one pressure valve (34) for the adjustable setting of a pressing pressure. PNK-8402WO 17.10.2025 5. Multi-press cylinder device (18) according to one of the preceding claims, characterized in that the basic heating element (24) is designed as a common heating sleeve (47) for at least two adjacent, in particular all, at least outermost press cylinders (20), wherein each press piston (22) is slidably guided by the heating sleeve (47) and can be heated at least indirectly for basic temperature control.

6. Multi-press cylinder device (18) according to one of the preceding claims, characterized in that the basic heating element (24) is designed as an electric heater or as a fluid heater, in particular with water or oil as the heating fluid.

7. Multi-press cylinder device (18) according to one of the preceding claims, characterized in that the booster heater (30) is designed as an electric heater, in particular as a ceramic heating element. 8.Multi-press cylinder device (18) according to one of the preceding claims, characterized in that the booster heater (30) can be thermally contacted with an underside of the workpieces (12) by means of length-variable thermal contact elements (46), in particular spring-loaded contact elements (46).

9. Multi-press cylinder device (18) according to one of the preceding claims, characterized in that the booster heater (30) comprises a temperature sensor (48) configured to detect a temperature in the punch area (31) of the press piston (22).

10. Multi-press cylinder device (18) according to one of the preceding claims, characterized in that it comprises a control unit configured to adjust the temperature, pressure, and piston stroke of each press cylinder (20). PNK-8402WO 17.10.2025. 3 11. Multi-press cylinder device (18) according to one of the preceding claims, characterized in that it comprises a hydraulic pump (26), in particular a speed-controlled pump, which is designed to generate and control a hydraulic pressure for the press cylinders (20), wherein preferably an active cooling control is provided for the controllable cooling of the hydraulic pump (26), a hydraulic compensation reservoir and / or a hydraulic fluid, in particular hydraulic oil.

12. Multi-press cylinder device (18) according to claim 11, characterized in that the active cooling control is provided by a controllable cooling device associated with the hydraulic pump (26) and / or a hydraulic compensation reservoir, wherein in particular a hydraulic temperature sensor associated with the hydraulic pump (26) and / or the hydraulic compensation reservoir is included for monitoring the temperature of the hydraulic pump (26) and / or the hydraulic compensation reservoir.

13. A method for sintering or diffusion brazing using a multi-press cylinder device (18) according to any of the preceding claims, characterized in that the displacement or pressure profile of each press cylinder (20) and / or the temperature profile of each booster heater (30) is controlled by a higher-level control system, in particular a uniform or individual pressure and / or a uniform or individual temperature is set in the punch area (31) of each press cylinder (20).

14. A method according to claim 13, characterized in that a time-dependent characteristic curve of the pressure profile and / or the piston displacement of each press cylinder (20), and / or a characteristic curve of the temperature profile in the punch area (31) is set and / or recorded.

15. A method according to claim 14, characterized in that the characteristic curve is ramp-shaped, parabolic, step-like, or of a predefinable function or according to a table. PNK-8402WO 10 / 17 / 2025.4 16. Method according to one of claims 13 to 15, characterized in that at the beginning of the pressing process, the inner press pistons (22) of the multi-press cylinder assembly (18) first extend ahead of the pressing process, and subsequently the outer press pistons (22) of the multi-press cylinder assembly (18) extend behind the pressing process. 17.A method according to any one of claims 13 to 16, characterized in that active cooling control is carried out on a hydraulic pump (26) that drives the press cylinders (20) and provides hydraulic pressure for generating the pressing force, and in particular a speed-controllable hydraulic pump (26), wherein the temperature of the hydraulic pump (26) and / or a hydraulic compensation reservoir is maintained within an adjustable temperature range during operation by controllable cooling, and in particular wherein the temperature of the hydraulic pump (26) and / or the hydraulic compensation reservoir is monitored by a hydraulic temperature sensor. 18.Sintering or diffusion device (10), in particular a multi-chamber device with a preheating, process, and cooling chamber, characterized in that a multi-press cylinder assembly (18) is enclosed in a process gas-tight, in particular vacuum-sealed, process chamber according to one of the preceding claims 1 to 9, and the sintering or diffusion device (10) is configured to carry out a process according to one of claims 13 to 17.

19. Sintering or diffusion device according to claim 18, characterized in that a counter-tool of the multi-press cylinder assembly (18) as an upper or lower tool (14, 16) provides pressure tolerance compensation, tilt compensation, and / or thermal distortion compensation, and in particular comprises a pressure cushion, a graphite foil, and / or a multiple punch arrangement with a pressure compensation function. PNK-8402WO 17.10.2025.

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