High-temperature bonding furnace

Abstract

A high temperature bonding furnace is presented, in particular configured for diffusion welding of materials such as metals, plastics, ceramics and corresponding workpieces, etc. The bonding furnace comprises a heating chamber, a tool receiving seat arranged in the heating chamber for receiving a workpiece to be processed in the bonding furnace, a pressing device arranged and configured to apply a pressing force to the workpiece, in which the pressing device comprises a pressing plate for uniformly applying the pressure of the workpiece, and is characterized in that the pressing plate is arranged in the heating chamber. The pressing plate is equipped with a pressing plate heating device for heating the pressing plate and / or the workpiece.

Description

Technical Field

[0001] The invention relates to a high-temperature bonding furnace, a process for diffusion bonding and a press plate capable of being heated. Background Art

[0002] It is generally known that metal workpieces can be joined by diffusion bonding. For example, metal workpieces can be diffusion bonded if they are joined by a press under pressure at high temperature. Diffusion bonding processes are complex procedures that depend on various influences and do not necessarily lead to equivalent or at least satisfactory results even under the same process conditions.

[0003] In the joining process, for example, deformations of the workpieces must be taken into account. For example, if the workpieces to be joined have cooling channels or other holes or openings in their interior, the pressure applied to the workpieces may deviate locally, resulting in a different overall deformation compared to a solid body of the same size. The previous history of the materials to be joined may also be important for the joining result; the grain size in the metal composite material and the manufacturing process of the individual metal layers (for example by rolling) may be particularly relevant here. Even if different materials for different workpieces should be described essentially as identical, i.e. produced using the same manufacturing process and pretreated to the same temperature, so that similar grain sizes should be assumed in the materials, the spread width between the materials must also be taken into account. This also applies if the workpieces are provided or cut from the same piece of raw material. For certain materials and / or material combinations, this may be even more difficult.

[0004] A particular challenge in the operation of a diffusion bonding system is to achieve uniform joining results across the components. In addition to the above considerations regarding the materials to be selected, various process parameters may be examined to see whether the process conditions can be further improved in order to further improve uniform joining results across the components to be joined or to make them satisfactorily available in the first place. Further improved joining results may expand the range of applications for other materials that cannot be processed or can only be processed inappropriately with existing systems. More complex structural shapes may be joined with already joinable materials. This may also help to reduce production downtime. Summary of the invention

[0005] Against this background, the invention has set itself the task of further homogenizing the joining result over the components to be joined. In one aspect of the invention, the task is also to enable the joining of new materials or more complex designs by means of diffusion bonding, which previously could not or only insufficiently be processed using this method. In a further sub-aspect, for example, the invention has set itself the task of enabling operation at lower temperatures in order to be able to join materials which would be too hot and would therefore be too strongly deformed using conventional joining processes. In a further aspect of the invention, the task is to further accelerate the process sequence in order to reduce operating costs and increase component throughput.

[0006] Said problem is solved by the invention as defined in the independent claim.The dependent claims provide further embodiments and preferred embodiments of the invention.

[0007] In the diffusion bonding process, a workpiece or a batch of workpieces is deformed in a controlled manner. Any pores in the bonding material, recesses inside the workpiece, the number and size of the bonding surfaces, and the previous history of the bonding materials are variables that can affect the process sequence. When force is applied to the workpiece or the batch of workpieces by a press, the material contact on the bonding surface is improved. In this way, inherent mutual diffusion can be generated or induced. Therefore, pressing is used to increase the contact surface in the area of ​​the bonding surface. These processes vary from workpiece to workpiece, whereby the difference may be so significant that the first component can be bonded with sufficient strength, but the next component to be bonded with the same parameters only achieves insufficient strength or quality. On the other hand, the shape of a component can be retained, while the next, otherwise identical component with the same parameters can be deformed in the area of ​​the cooling channel, for example due to the pressing process.

[0008] According to the present invention, a high temperature bonding furnace is provided, which is prepared for diffusion bonding of bonding materials, for example. The bonding material can be metal and include metal workpieces. The metal can be any metal-containing material or substance. For example, this includes metals such as iron, copper, aluminum, titanium, etc., and alloys such as stainless steel, tool steel, superalloys, bronze, tin or others. The bonding material can also be non-metallic or composite materials. Examples of non-metals include plastics or ceramics. Examples of composite materials include ceramic composite materials with aluminum or copper, etc.

[0009] The high temperature joining furnace may also be arranged for force assisted welding or sintering of components.In general, therefore, the high temperature joining furnace is arranged for pressurized material finishing with or without filler material.

[0010] A high-temperature joining furnace comprises a heating chamber in which the workpieces and usually also the furnace interior are heated to the processing temperature.

[0011] The workpiece holder is arranged in the heating chamber to remain on the workpiece to be processed in the bonding furnace. Usually, the workpiece holder is located at the downside of the heating chamber. For example, the workpiece holder can include a plate, and includes a holder into which the workpiece to be bonded will be inserted. The workpiece holder can be a part of a reverse pressing element or be arranged thereon. In other words, the workpiece holder can be a passive counterpart for a pressing device, or the workpiece holder itself can withstand the pressing force from below the workpiece holder, and therefore represents a reverse pressing element.

[0012] The bonding furnace further comprises a pressing device, which is arranged and designed to apply a pressing force to the workpiece. For example, the pressing device is arranged so that the upper part (such as a pressing punch, etc.) abuts against the workpiece from above, whereby the workpiece abuts against the workpiece holder or against the counter-pressing element. In other words, the workpiece is clamped between the upper part or the pressing punch and the counter-pressing element or the workpiece holder.

[0013] The upper part comprises a pressing plate for this purpose, by means of which the pressing force can be evenly distributed and applied to the surface so that the workpiece is evenly pressed. Depending on the intended use or shape of the workpiece, the pressing plate can have a flat surface so that the workpiece can be evenly subjected to the pressing force via the surface of the pressing plate. The pressing plate can also have recesses, protrusions or steps in order to shape the pressing plate to the desired surface of the workpiece or workpieces. Therefore, the pressing plate can generally be described as a "pressing element". In the following, the term "pressing plate" is used because, according to this description, this term seems to be commonly used by those skilled in the art.

[0014] The press plate is equipped with a press plate heating device for heating the press plate and / or the workpiece. For example, the press plate is a pressure distribution plate because it distributes the pressing force generated by the press device and applied to the workpiece on the surface of the workpiece. With the help of the press plate heating device, the press plate can be tempered or heated as evenly and homogenized as possible on its surface. This also makes it possible to heat the workpiece evenly across the press plate. In other words, the workpiece can now be heated conductively with the help of the press plate heating device, which can enable significantly faster heat transfer to the workpiece and also enable more uniform heat input on the surface of the workpiece. In addition, the use of the press plate heating device enables the use of materials that require significantly lower processing temperatures, at which lower processing temperatures, radiant heat may not be able to deliver enough heat output to the workpiece, making it even impossible to perform uniform temperature distribution in the workpiece using only radiant heat. Therefore, the press plate heating device according to the present invention opens up the use of new materials as workpieces that were previously not available for diffusion bonding.

[0015] The press plate heating device can preferably be integrated into the press plate, i.e. it can be fully integrated. In this case, a heat supply can be fed or connected to the press plate from the outside and supply heat to the press plate heating device. If the press plate heating device is integrated in the press plate, the heat transfer into the press plate is as seamless as possible, i.e. conductive.

[0016] The press plate can be a multi-part press plate. In the multi-part press plate, a workpiece side layer and a press side layer can be included, and the press plate heating device can be preferably arranged between the workpiece side layer and the press side layer of the press plate.

[0017] The bonding oven may have a flexible bonder for bonding the press plate heating device to the energy source. For example, the flexible bonder may include a metal strip material, such as copper strip, etc., which can compensate for movement, shock or vibration while maintaining electrical contact.

[0018] The press plate heating device provides a heat conductive output for the press plate, i.e., the press plate heating device is a conductive press plate heating device. For example, the press plate heating device is designed to be electrically operable, such that the press plate heating device generates heat when supplied with electricity from the energy source. Alternatively or cumulatively, the press plate heating device may be arranged such that a fluid may flow through the press plate heating device, such that the press plate heating device generates heat when a hot fluid is applied to the press plate heating device by the energy source.

[0019] The pressing plate may be movable, for example the pressing plate is displaced by one or more pressing punches, whereby the one or more pressing punches are set in motion by one or more pressing cylinders. When the pressing force is applied, the workpieces are continuously deformed or joined.

[0020] For example, by providing a movable workpiece holder and moving the workpiece upward on the workpiece holder, the pressing device can also be arranged in the following manner: the pressing device presses onto the workpiece from below. In a further embodiment of the present invention, a first pressing plate and a second pressing plate for applying force on both sides can be provided, for example an upper pressing plate and a lower pressing plate or a left pressing plate and a right pressing plate.

[0021] To press the workpiece, a part that acts like a pressing punch, which can withstand forces from the outside, and a counter-pressing element that counteracts the pressing force are usually used. The workpiece is clamped between the pressing punch and the counter-pressing element and joined or formed there.

[0022] The bonding furnace may include a wall-side heating device or a furnace heating device in the furnace chamber. The wall-side heating device may be designed to heat the workpiece by thermal radiation. Because a low pressure (i.e., a vacuum of the highest possible quality) is usually provided in the furnace chamber, there is virtually no convection in the furnace chamber, so that the wall-side heating device can substantially transmit radiant power. The wall-side heating device can compensate for any heat loss caused by the workpiece arranged in the furnace chamber continuously emitting a certain amount of heat by radiant heat. Therefore, the wall-side heating device can be used as a support to further homogenize the temperature distribution in the workpiece. The furnace heating device may be further provided to emit radiant heat into the furnace chamber alone. The two heating devices (i.e., the pressing plate heating device and the furnace heating device) may complement each other, because the furnace heating device compensates for the radiation of heat away from the workpiece by radiating heat into the workpiece. In this way, any cold spots that may appear on the workpiece (especially on the side edges) can be avoided. However, depending on the design or requirements of the workpiece to be pressed, the furnace heating device may not be necessary, because the pressing plate heating device can provide an advantageously uniform heat output on the surface of the workpiece by conduction transfer.

[0023] The sensor device may be provided in the bonding furnace, which provides at least one sensor signal. For example, the sensor device may detect the position or extension length of the pressing punch or the position of the pressing plate. The sensor signal may be transmitted to or processed by the control device, which is designed to control at least the pressing device in response to the at least one sensor signal.

[0024] The sensor device of the bonding furnace can detect process parameters. The process parameter can be the thickness of the workpiece, the pressure ram of the pressing device or the position of the pressing ram. The process parameter can also be the pressing force applied, the hydraulic pressure or the distance traveled by the pressing device. Then, a sensor signal can be generated from the base value recorded by the sensor device (i.e., one of the aforementioned process parameters). Several sensor devices can be provided to record different process parameters simultaneously. A further sensor device can detect one or more process parameters simultaneously with the first sensor device, and thus generate at least one or more further sensor signals. One or more sensor signals can be processed to control the bonding process or the bonding furnace so that different process parameters can be considered in the control.

[0025] The pressing device may include a hydraulic device, whereby the pressing force is established by establishing hydraulic pressure. The pressing device may also include an electric spindle, which generates feed, for example, by rotation, and applies the pressing force to the workpiece.

[0026] The bonding furnace may include an input device for inputting process parameter settings. For example, the input device may be a user-operated terminal device. The process parameter specifications that may be stored before the bonding process begins are, for example, the desired process temperature, process time, material of the workpiece, parameters or other data about the underlying material, and the number and / or quantity of one or more bonding surfaces of the workpiece.

[0027] For example, a workpiece may consist of a plurality of layers of different materials (e.g. at least two different materials stacked on top of each other), whereby each surface to be joined between two different materials is described as a joining surface. In the case of a plate-like workpiece comprising 25 layers, for example, 24 joining surfaces are thus arranged in the workpiece. Information about cavities in the workpiece may also be taken into account in the specification of the process parameters.

[0028] The bonding furnace may further comprise an output device, for example, for displaying or selecting process parameters and / or control programs. For example, information about which process step the bonding furnace is currently in may be displayed on the output device.

[0029] The pressing device may include a pressing punch through which the pressing force is transmitted, and / or the pressing device may include a pressing plate by which the pressing force is applied to the workpiece.

[0030] The pressing device may include a pressing cylinder. The pressing punch may be coupled to the pressing cylinder so that the pressing cylinder acts on the pressing punch by a pressing force and adjusts the pressing punch in the direction of the workpiece. The pressing device may include a plurality of pressing cylinders, for example, 2, 3 or 4 pressing cylinders.

[0031] Preferably, a plurality of pressing punches are used, which act together on the workpieces (e.g. via a pressing plate), and the pressing plate is subjected to a pressing force which is as uniform as possible or evenly distributed on the surface by these two or more pressing punches. These pressing punches can be arranged adjacent to each other so that an array of pressing punches acts on the pressing plate. The aim here is to distribute the pressure as uniformly as possible on the workpieces to be joined, since the pressing force required for joining may deform the pressing plate or the pressing element, so that the workpieces to be joined are subjected to the pressing force unevenly.

[0032] The high temperature bonding furnace may include a housing. For example, the heating device, the heating chamber, the workpiece holder and / or the pressing device may be accommodated in the housing. The pressing device may be arranged on the housing and / or supported on the housing by means of a pressing mount. For example, the pressing mount is attached to the housing or rests against the housing so that a pressing cylinder connected to the pressing mount can be supported against the housing of the high temperature bonding furnace.

[0033] In order to support the pressing device on the housing, the housing may have a supporting or holding structure, such as a supporting frame or a supporting cage, etc. The supporting or holding structure may be a component separate from the housing or integrated with the housing.

[0034] The support or retaining structure and / or the pressing mount can be designed to be movable and / or deformable. For example, when a pressing force is applied to the workpiece, the pressing device can support itself against the pressing mount, thereby displacing and / or deforming the pressing mount, for example by deforming the support or retaining structure. Here, a storage force can be absorbed between the pressing mount and the pressing device (for example, a pressing cylinder with a pressing punch), similar to the pretension of a spring, so that, for example, when the pressing force increases, the pressing action on the workpiece can increase evenly or more gently. The movable and / or deformable design of the pressing mount or the support or retaining structure can be used to prepare the pressing device, wherein the pressing device is prepared in an initial position in which a pre-pressing force has been applied to the workpiece.

[0035] The joining furnace can be arranged in such a way that a lateral displacement and / or deformation of the press holder occurs by means of a compressive force exerted by the pressing device on the workpiece. In other words, the application of a pressing force to the press holder (the press holder acting as a base of the press machine) causes a lateral displacement and / or deformation of the press holder. By absorbing the compressive force in the region of the press holder or in the press holder, a spring effect is generated between the press holder and the pressing device or between the press holder, the pressing cylinder and the pressing punch.

[0036] The pressing device can be arranged in such a way that a pre-tensioning force can be established between the pressing punch and the housing during the pressing process or when the pressing force is established. The presence of the pre-tensioning force in the pressing device allows for a finer dosing and thus a more accurate detection and / or tracking of the punch position during the pressing process. Furthermore, the accumulation of the pre-tensioning force allows for a more accurate setting or dosing of a pressure correction or a pressing force correction.

[0037] For example, when a pressing force is applied, the pressing mount may be displaced or deformed by more than 1 mm, for example more than 3 mm, more specifically more than 5 mm or even more than 10 mm. This may form a kind of "spring mechanism", i.e., a preload force. When a compressive force is applied, the pressing mount may also be displaced or deformed by less than 3 mm, preferably less than 6 mm, more preferably less than 12 mm; the minimum deflection value and the maximum deflection value may be combined into an interval, for example more than 3 mm and less than 6 mm, such as "in the range between 3 mm and 6 mm".

[0038] The sensor device may be designed to detect the position of the pressing punch. The sensor device may also be designed to detect the pressing force applied to the workpiece.

[0039] The control device can be arranged to determine the required pressing force of the inserted workpiece for the joining process by recording and evaluating the sensor signal. In addition, the control device can automatically control the pressing device based on the determined required pressing force. In other words, the control device controls the pressing device taking into account the recorded or evaluated sensor signal.

[0040] If necessary, the control device can also adjust or control the heating device so that different temperatures can be maintained in the heating chamber at different times during the bonding process.

[0041] The joining furnace may have a filling and removal opening. In one example, the filling and removal opening is coupled to a safety circuit that detects the state of the opening.

[0042] The workpiece holder can advantageously serve as a counter-pressing element for the pressing device.Thus, the pressing device can press the workpiece against the workpiece holder so that the workpiece is clamped between the pressing device and the workpiece holder.

[0043] The control device may provide at least one selectable control program. The selectable control program may preselect basic parameters, such as a typical pressure that is generally suitable for a specific material combination or a minimum pressure tension at which a joining process can be started. The selectable control program may include a pretreatment program and / or a press-to-go program.

[0044] The control device is preferably designed to adapt the selected control program in response to at least one sensor signal, in particular during the execution of the control program. The control program can be adapted to change or influence process parameters such as the pressing force, temperature and / or path of the pressing device during the bonding process.

[0045] At least one control program may be stored in a program memory of the high temperature bonding furnace.The control device may comprise a programmable logic controller.

[0046] The bonding furnace is preferably designed for carrying out the bonding process at a temperature of 1200°C or less, preferably 1000°C or less, more preferably 950°C or less, for example in the case of metals or metal workpieces. This means that the high temperature bonding furnace is able to carry out the diffusion bonding process at a lower temperature than previously known metals or metal workpieces, and thus introduce new materials that could not previously be processed using this method into the diffusion bonding. At lower temperatures, the time required to introduce sufficient radiation energy into the workpiece to be processed is significantly longer, and it may even be the case that the irradiation and radiation are in equilibrium or that a uniform temperature distribution cannot be achieved inside the workpiece. These problems are solved using the press plate heating device presented here. The bonding furnace can also be designed to carry out the bonding process at a temperature of 450°C or more, for example 500°C or more, preferably 550°C or more and more preferably 600°C or more.

[0047] For example, in the case of non-metals such as plastics, ceramics or corresponding workpieces, the bonding furnace can also be set to perform the bonding process at a temperature of 350° C. or lower, preferably 300° C. or lower, more preferably 250° C. or lower, or even at a temperature of 200° C. or lower. This temperature range also opens up access to new materials for diffusion bonding processes. The bonding furnace can also be designed to perform the bonding process at a temperature of 80° C. or higher, for example 100° C. or higher, preferably 120° C. or higher and more preferably 140° C. or higher.

[0048] The invention further describes a method for diffusion bonding in a high temperature bonding furnace, such as described above. The method for diffusion bonding comprises the following steps: filling the bonding furnace with workpieces; applying at least one pressing plate of a pressing device to the workpieces; heating the workpieces to a bonding temperature mainly by means of a pressing plate heating device; pressing the workpieces with the pressing device to perform, for example, a diffusion bonding process.

[0049] The method can be further improved by the following steps: During the pressing process, the press plate is tempered or heated by means of a press plate heating device in order to homogenize the temperature distribution in the workpiece.

[0050] In addition, the method can be formed by the following steps: detecting or determining the pressing force required for the bonding process in the pressing process, for example using an automatic control device, such as a programmable logic controller (PLC), etc.; and controlling the pressing device in response to the detected or determined pressing force required for the bonding process. For example, the required pressing force can be determined via the pressing path by distance measurement.

[0051] The method can also be further developed to include the following step: adaptively controlling the pressing device by means of a pressing force required for the joining process which is detected or determined repeatedly, for example at fixed time intervals, and in response to the repeatedly detected or determined pressing force.

[0052] The method can also be further developed with the following steps: continuously monitoring the joining process by means of at least one sensor device and continuously adapting the joining process if a deviation of the monitoring value from a target value is detected.

[0053] The method can also be further developed by the following step: before pressing the workpiece, process parameter specifications are input, for example, by a user.

[0054] Furthermore, the step of taking into account process parameter specifications when providing set points for automated process control may also represent a further improvement of the method.

[0055] The specification also describes a heatable press plate, for example for use in a high temperature bonding furnace, as explained above. The press plate is designed to uniformly apply a pressing force to a workpiece placed in a high temperature bonding furnace. The press plate is characterized in that the press plate is equipped with an integrated press plate heating device for heating the press plate and / or the workpiece.

[0056] In an advantageous embodiment, the press plate heating device is integrated into the press plate, preferably fully integrated. The press plate can be a multi-part press plate, for example comprising a workpiece side layer and a press side layer of the press plate. The press plate heating device can be arranged between the workpiece side layer and the press side layer.

[0057] Each part of the press plate, i.e., for example, the layer on the workpiece side, the layer on the press side and a possible press plate heating device, can consist of the same basic material, but with different doping. The press plate can include a ceramic material. The layer on the workpiece side and / or the layer on the press side can include or consist of a ceramic material. Furthermore, the press plate heating device can include or consist of a ceramic material or a metallic material.

[0058] The ceramic material of the heatable press plate may include at least one of the following: carbon fiber reinforced graphite, carbon fiber reinforced silicon carbide, titanium zirconium reinforced molybdenum, silicon carbide or aluminum oxide fiber reinforced oxide ceramic. The workpiece side layer and / or the press side layer may also be composed of one of the above materials.

[0059] The press plate heating device of the heatable press plate may comprise at least one of the following or consist of tungsten, molybdenum, a nickel-based alloy such as micrometal, a non-oxide ceramic such as silicon carbide or graphite or also carbon fiber reinforced carbon (CFC).

[0060] The pressing plate heating device may be plate-shaped. The pressing plate heating device may also be curved. The pressing plate heating device may have channels or tracks. The channels or tracks may penetrate the pressing plate uniformly so that the distance between the material of the pressing plate and one of the channels or tracks is at most twice the width of one of the channels or tracks or less. Such a distribution of channels or tracks in the pressing plate provides the most uniform heat distribution possible for the pressing plate.

[0061] The press plate heating device may be electrically operated so that the press plate heating device generates heat when an electric current is applied to the press plate heating device. Alternatively or cumulatively, the press plate heating device may be arranged so that a fluid may flow through the press plate heating device so that the press plate heating device generates heat when a hot fluid is applied to the press plate heating device.

[0062] The press plate heating device can preferably have two or more heating plates. The press plate heating device can also have a connecting piece for joining two or more sub-areas (such as heating plates etc.), wherein the connecting piece comprises graphite or consists of graphite, for example.

[0063] The connector can be designed to be reversibly deformable, so that when a pressing force is applied, the connector deforms, for example becomes wider, and improves or establishes the electrical contact between these sections of the press plate heating device. In other words, the connector is arranged in the press plate heating device in such a way that at the moment when the compressive force is applied to the press plate, the electrical contact between the parts of the press plate heating device is improved or first established by the connector, thereby improving the operational safety of the press plate heating device. It should also be taken into account that the pressing force applied to the press plate is very high, and suitable materials are characterized by the fact that they are subjected to given pressure and temperature conditions, and on the other hand the materials used are not marked in the joining result. For example, materials of different densities are usually recognizable by the fact that they are impressed on the workpiece to be processed like a stamp, and the arrangement of materials of different densities or at least different hardnesses can be recognized in the finished workpiece. This should be prevented as much as possible. This can also be achieved by the press plate heating device presented here.

[0064] For this aspect, the heatable press plate may also include a pressure balancing layer. The pressure balancing layer may be designed to cover the entire surface and may be flexible or compressible. The pressure balancing layer may be arranged adjacent to the press plate heating device, for example placed on the press plate heating device and may completely cover the press plate heating device. The pressure balancing layer may be a graphite foil. The pressure compensation layer enables the compression force passing through the press plate to be further homogenized, whereby local differences in the hardness or density of the material used for the press plate heating device do not lead to die-like impressions in the workpieces to be joined or to a much lesser extent.

[0065] The layer on the press side and / or the layer on the workpiece side can be designed as a tile carpet, for example as a ceramic tile carpet. The use of small components, such as a ceramic tile carpet, can mean that inhomogeneities, such as the edges of the heating device, can be compensated for and the forces can be distributed via the tiles of the ceramic tile carpet and therefore via the press plate. The press plate heating device can be arranged in the heating plane, i.e. in other words, the press plate heating device is confined to a vertical area in the press plate and is surrounded by the press plate material on the lower side and the upper side. The ceramic tiles can be arranged between the components of the press plate heating device.

[0066] In the following, the invention is explained in more detail with reference to exemplary embodiments and with reference to the drawings, wherein identical and similar elements are sometimes provided with identical reference symbols and features of the different exemplary embodiments may be combined with one another. BRIEF DESCRIPTION OF THE DRAWINGS

[0067] Figure 1 A first embodiment of a high-temperature joining furnace with inserted workpieces is shown in a side cross-sectional view,

[0068] Figure 2 A further embodiment of a high temperature bonding furnace is shown in a side cross-sectional view, wherein a pressing device is applied to the workpiece or a pressing force is applied,

[0069] Figure 3 is a top view of the heating plate of the pressing plate heating device,

[0070] Figure 4 is a side cross-sectional view of the heating plate,

[0071] Figure 5 is a side view of the heating plate,

[0072] Figure 6 is a three-dimensional diagram of a continuous heating plate.

[0073] Figure 7 is a three-dimensional cross-sectional view of a continuous heating plate,

[0074] Figure 8 is a three-dimensional partial cross-sectional view of a pressing plate heating device with a split heating plate,

[0075] Fig. 9 yes Figure 8 A side cross-sectional view of an embodiment of

[0076] Fig.10 is a view of a split heating plate,

[0077] Fig.11 is a side view of the heating plate,

[0078] Fig.12 is a side view of a pressing plate with a pressing plate heating device,

[0079] Fig.13 is a view of a pressing plate with a pressing plate heating device,

[0080] Fig.14 is a three-dimensional diagram of a pressing plate with a pressing plate heating device,

[0081] Fig.15 is a three-dimensional partial cross-sectional view of a pressing plate with a pressing plate heating device,

[0082] Fig.16 is a further perspective partial cross-sectional view of a pressing plate with a pressing plate heating device,

[0083] Fig.17 is a perspective view of a flexible connector for a press plate heating device,

[0084] Fig.18 is a side view of the flexible joint,

[0085] Fig.19 is a perspective partial cross-sectional view of a further embodiment of a press plate having a press plate heating device with a ceramic bend,

[0086] Fig. 20 is a perspective partial cross-sectional view of a further embodiment of a press plate having a press plate heating device with ceramic tiles,

[0087] Fig.21 This is a three-dimensional diagram of a high-temperature bonding furnace.

[0088] Fig. 22 This is another three-dimensional image of the high-temperature bonding furnace.

[0089] Fig.23 is a perspective view of a high temperature bonding furnace with an outer edge attachment,

[0090] Fig.24 This is a top view of the high temperature bonding furnace.

[0091] Fig.25 This is a three-dimensional diagram of a high-temperature bonding furnace.

[0092] Fig.26 It is a flow chart of the joining process. DETAILED DESCRIPTION

[0093] Figure 1 A first embodiment of a high-temperature bonding furnace 1 having a heating chamber 15 arranged inside a housing 12 is shown, wherein a workpiece 50 is arranged for a subsequent pressing process. The bonding furnace 1 has a filling or removal opening 11, through which a workpiece 50 (or several workpieces 50 or a batch of workpieces) can be inserted into the heating chamber 15 or removed from the heating chamber 15. The workpiece 50 is located on a workpiece holder 34, which is arranged on the lower side of the heating chamber 15. The workpiece holder 34 can be a counter-pressing element 38 or be designed as a counter-pressing element 38 or be arranged on a counter-pressing element 38. In Figure 1 In the example shown, the workpiece 50 rests directly on the counter-pressing element 38, which also forms the workpiece holder 34. Depending on the design of the workpiece 50, the workpiece holder 34 can be placed on the counter-pressing element 38.

[0094] In this embodiment, the pressing device 20 is arranged on the upper side of the housing 12 of the bonding furnace 1 so as to be able to exert a pressing force on the workpiece 50 from above and against the workpiece holder 34 or the counter-pressing element 38. Figure 1In the example shown, four pressing punches 32 are connected to the pressing cylinder 24. The pressing cylinder 24 is, for example, a hydraulic cylinder, whereby the pressing punch 32 is set by the pressing cylinder 24 via a transmission 26 in the direction of the workpiece 50. The pressure distribution element 22 is arranged in the receiving area 6 of the housing 12 in order to distribute the pressing force of the pressing device 20 to the plurality of pressing punches 32.

[0095] Instead of a plurality of pressing plungers 32, a single pressing plunger 32 can also be used if necessary. By means of a plurality of pressing plungers 32, for example 4, 8 or 12 pressing plungers 32, the pressing force can be evenly (more evenly) distributed on the pressing element 36 on the one hand. For example, an improved heat sealing of the heating chamber 15 can also be achieved with the aid of a plurality of pressing plungers 32, since each pressing plunger 32 only requires a relatively small opening in the insulation 16 of the heating chamber 15, so that the energy loss from the heating chamber 15 can be lower. In addition, by using a plurality of pressing plungers 32, the heat energy loss can also be better balanced via the outer surface of the heating chamber 15, and an overall improved homogenization of the temperature distribution in the heating chamber 15 can be achieved. This also applies similarly to the counter-pressing plunger 29 on the lower side of the heating chamber 15, whereby a more even pressure distribution on the counter-pressing element 38 and a consideration of lower and / or more even heat losses are taken into account.

[0096] The pressing force generator 28 (in this example, the hydraulic unit 28) applies pressurized hydraulic fluid to the pressing cylinder 24 so that it is released or disengaged by the pressing force generator 28 and applied to the workpiece 50. For example, the motor unit 3 may generate hydraulic pressure in the pressing force generator 28.

[0097] A first sensor device 4 is arranged on the upper side, which serves to measure the path of the pressing cylinder 24. Thus, the first sensor 4 detects the distance of the pressing cylinder 24 or the distance of the pressing plunger 32 or the extension (stroke) of the pressing cylinder 24 and provides a first sensor signal from the distance. Another sensor 5 can be arranged in the pressing force generator 28 and / or in the pressing cylinder 24, for example, for measuring the hydraulic pressure, in order to derive information about the applied pressure and provide it as a sensor signal.

[0098] The workpiece holder 34 is arranged in the heating device 14 so as to accommodate the workpiece 50 in the heating chamber 15. Moreover, in order to damage the insulation 16 accommodating the heating chamber 15 as little as possible, the workpiece holder 34 is provided with a plurality of counter-pressing punches 29, which dissipate the force distribution from the counter-pressing element 38 as evenly as possible, so that the counter-pressing element 38 is subjected to the smallest possible deformation. Since the counter-pressing punches 29 pass through the insulation 16 and the insulation 16 should be subjected to the smallest possible damage, a relatively small penetration area can be caused overall or the counter-pressing punches 29 can be better heat-sealed.

[0099] A second sensor device 42 is also arranged on the underside, which can, for example, detect the pressing force applied to the workpiece 50. The second sensor device 42 is, for example, a pressure sensor. A plurality of two or more pressure sensors can also be used as the second sensor device 42, for example each in the region of the counter-pressing punch 29, so that the pressure distribution acting on the counter-pressing element 38 can be detected and output as a sensor signal. In this way, it can be detected whether the pressure distribution on the workpiece or charge 50 occurs in the desired manner, for example, uniformly on the workpiece or charge 50.

[0100] In an alternative embodiment, the pressing force may be applied to the workpiece or charge 50 from both sides. For example, the Figure 1 An embodiment of the invention is provided such that instead of a (passive) subassembly comprising, for example, a counter-pressing punch 29 and a counter-pressing element 38, a further pressing device 20' is arranged on the lower side of the high-temperature bonding furnace.

[0101] In this example, the automatic process control 44 is arranged in the region of the substructure 8 of the joining furnace 1. Input devices 48 and output devices 46, such as keyboard 48 and screen 46, enable input and output to the control device 44 and thus manually influence the input of process sequences or process parameters.

[0102] exist Figure 1 In the high-temperature bonding furnace 1 shown, in which the upper pressing plate 36 has a pressing plate heating device 62 and the counter-pressing element 38 has a pressing plate heating device 64, the two pressing plate heating devices 62, 64 can have a similar or identical design in form and function, especially if both the pressing plate 36 and the counter-pressing element 38 are provided in the form of pressing plates. If both plates 36, 38 are equipped with pressing plate heating devices 62, 64, the heat distribution in the workpiece 50 can be further homogenized and, if necessary, the time required for heating the workpiece 50 can be further reduced.

[0103] also, Figure 1Also shown is the possibility of electrically contacting the press plate heating devices 62, 64 by means of the contact device 100, whereby the flow of current extends via the joining element 112, the feedthrough 114 to the external contact 116. Further details of the contact device 100 can be found in Fig.17 and Fig.18 Found in.

[0104] See also Figure 2 , shows the pressing device 20 in an operating position, whereby the pressing plate 36 is completely positioned against the workpiece 50 and applies a pressing force to the workpiece 50. The pressing cylinder 24 or the transmission member 26 is shown in a disengaged position. In this embodiment, the pressing plungers 29, 32 are each equipped with a pressure distribution member 37, which is arranged at an angle between the pressing plate 36 and the corresponding pressing plunger 32 and helps to transmit the pressing force to the pressing plate 36 more evenly.

[0105] The pressing force applied to the workpiece 50 by the pressing device 20 can be detected by the pressure sensor 42, whereby the pressure sensor 42 transmits the sensor signal 170 to the control device 44. Figure 2 The embodiment in corresponds to Figure 1 The embodiments shown and described in . Figure 2 Also shown is the electrical contacting of the press plate heating devices 62 , 64 via the electrical contact device 100 .

[0106] Figure 3 A first embodiment of a heating plate 62 for a high-temperature joining furnace 1 is shown. In the plan view shown, the press plate heating device 62 has a heating element cover 72, in which a receiving seat 68 for a fastening means is provided. The connecting protrusion 66 protrudes laterally beyond the dimensions of the cover 72 on both sides, whereby the connecting protrusion 66 is associated with a heating element 74.

[0107] Figure 4 The press plate heater 62 is shown in cross section, whereby the three-layer structure with the heating element top layer 72 , the heating element 74 and the heating element bottom layer 76 can be seen.

[0108] Figure 5 A side view of the press plate heating device 62 is shown, from which the three layers 72, 74, 76 of the heating element 74 and the connecting tab 66 can also be seen. The heating element 74 is laterally surrounded by lateral enclosures 72a, 76a, so that it is surrounded on all sides by the top layer 72 and the bottom layer 76, except for the connecting tab 66. The connecting tab 66 serves to introduce the energy required for heating into the heating element 74. For example, electrical contact can be established via the connecting tab 66.

[0109] See also Figure 6, shows a three-dimensional view of the pressing plate heating device 62. For example, Figure 6 The heating device 62 shown may correspond to Figures 3 to 5 The heating device 62 is shown. In all the drawings, the same reference numerals represent the same elements or components. Figure 7 , Figure 6 The exemplary embodiment of FIG. 7 is shown in a stepped cross section, whereby the three-layer structure comprising a top layer 72 , a heating element 74 and a bottom layer 76 can be seen, as can the housing of the heating element 74 by means of housings 72 a , 76 a .

[0110] See also Figure 8 , shows a further embodiment of a press plate heating device 62, which has a split heating plate 74. In other words, two heating plates 74 are provided, which are jointly surrounded by a top layer 72 and a bottom layer 76. The heating elements 74 are in electrical contact with each other via the contact lip 67 and the connection piece 78, so that a current flow can be established from the first connection protrusion 66 through the first heating element 74, the contact lip 67 or the connection piece 78, the second heating element 74a and the second connection protrusion 66a. Fig. 9 Shows Figure 8 4. A cross section of the heating element 62, through which the connecting piece 78 is visible. Fig.10 and Fig.11 A single heating plate 74 is shown, for example as part of a split heating plate or heating plane, whereby the connecting protrusion 66 and the contact lip 67 are visible.

[0111] There may be several reasons for dividing into several smaller heating plates 74, 74a, 74b, 74c instead of one continuous large heating plate. On the one hand, it has been found that a continuous large heating plate 74 is more prone to cracking during operation and may therefore fail earlier than when several smaller heating plates 74, 74a, 74b, 74c are used. In addition, any desired material for manufacturing the press plates 74, 74a, 74b, 74c may not even be manufactured to a size corresponding to the full size of the current press plates 36 at the time of preparation of the present application. Finally, it is also determined in the context of the present invention that the use of smaller heating plates 74, 74a, 74b, 74c has the following advantages: it is easier to select any existing material defects, and in addition, any existing material defects (cracks, spalling, incorrect grain size, pores or cavities, etc.) can be detected in the heating plates 74, 74a, 74b, 74c. Furthermore, any existing material defects (cracks, spalling, defective grains, pores or cavities, etc.) in the heating plates 74, 74a, 74b, 74c result in less breakage because the bending moments (and deflections during operation) that occur are significantly smaller, so more material defects can be tolerated, which helps to reduce manufacturing costs overall.

[0112] See also Fig.12 , shows a press plate heating device 62 installed in a press plate 36, wherein the press plate has a press plate element 71 on the press side, a workpiece press plate element 77 and a press plate heating device 62 inserted between these two layers. These layers are connected to each other by fastening means 80, for example screwed together.

[0113] See also Fig.13 , shows a top view of the pressing plate 36 having the pressing plate heating device 62. Fig.13 The embodiments of Fig.14 The pressing plate heating device 62 is enclosed between the pressing plate element 71 on the pressing side and the workpiece pressing plate element 77 and is screwed together using screws 80. Fig.15 , Fig.13 and Fig.14 The embodiment of the invention is shown in a stepped cross section, exposing a plurality of heating elements 74, 74a, 74b, 74c. The heating elements 74, 74a, 74b, 74c are electrically contacted with each other by means of a connection piece 78. Fig.16 The same pressure plate 36 is shown again in another stepped section, so that four heating elements 74 , 74 a , 74 b , 74 c are exposed. The four heating elements 74 are arranged in a common heating element plane, ie adjacent to one another.

[0114] Since these heating elements are arranged in the press plate 36, they are usually subject to movement during operation. Therefore, the press plate 36 is placed against the workpiece and, depending on the size of the workpiece, etc., the press plate 36 is in different insertion positions during operation. In order to compensate for different positions or movements of the heating elements 74, such as Fig.17 A flexible contact device 100 is provided, which can not only compensate for the change of position, but also compensate for the movement of the pressing plate or pressing device 20, such as impact movement or vibration movement, etc. For this purpose, the contact device 100 has a flexible compensation element 104, which attenuates and separates oscillations and vibrations. The contact device 100 is attached to the heating element 74 using a heating element clamp 102, whereby the connecting protrusions 66, 66a are clamped or surrounded. It can also be screwed to the connecting protrusion 66. The top of the contact device 100 has a contact element 106, for example, to connect a copper strip there, for further current conduction. In this embodiment, two contact devices 100 are connected to the heating element 74, for supplying and removing current.

[0115] Fig.18 A cross-sectional view of the contact device 100 is shown, with the attachment arrangement of the connecting protrusion 66 provided with further details, the stud receiving seat 108 and the stud 110 being shown in cross-sectional view. Fig.18In FIG. 1 , the contact device 100 is connected to two heating elements 74 , whereby only one connection side is shown for better graphical visibility. Typically, a second contact device 100 is used so that a current circuit or current flow through the heating elements 74 , 74 a can occur.

[0116] See also Fig.19 , shows a further embodiment of the heating device 62, wherein the heating element 74 is provided in the form of a ceramic bend. The heating element 74 can also be designed, for example, as a graphite, molybdenum or CFC bend. The ceramic bend 74 is electrically conductive, so that a current can be realized from the first connecting protrusion 66 through the ceramic bend 74 to the second connecting protrusion 66a. The heating device 62 is enclosed in a press plate 36, which has press plate elements 71, 77. For reasons of clarity, the fastening device 80 is not explicitly shown in this embodiment. For example, these plates can be glued together, but due to the high operating temperatures, a screw connection will usually be advantageous.

[0117] See also Fig. 20 , shows a further embodiment of a press plate heating element 62, wherein the heating element top layer 72 and the heating element bottom layer 76 are designed as floor tiles. The heating element 74 is thus embedded in the floor tiles 72, 76, 82. This has the advantage that any unevenness or joints are uniform and are therefore less visible as restrictions in the workpiece 50.

[0118] See also Fig.21 and Fig. 22 , shows a high temperature bonding furnace 1, which includes an outer frame 7, 9, 10 to support a pressing device 20. A pressing cylinder 24 is supported by the supporting frame element 10 so that a pressing force can be transmitted from the pressing device 20 to a workpiece 50 arranged in the high temperature bonding furnace 1 (for example, see the attached Figure 1 , Figure 2 ). When the pressing force is applied, the total force is absorbed by the outer frames 7, 9, 10, which can bend upwards in a direction away from the joining furnace 1 during operation. The upward bending of the outer frames 7, 9, 10 provides dynamic support for the pressing device 20, so that the pressing base 18 is formed by the outer frames 7, 9, 10. Fig.23 In the embodiment, a position sensor 5 is provided, by which a position deviation of the pressing base 18 can be detected. The position deviation can also be used to draw conclusions about the pressing force applied by the pressing device 20, and this information can be provided as a sensor signal.

[0119] Figure 23 to Figure 25A further embodiment of the high temperature bonding furnace 1 is shown, which is now shown as being completed with additional attachments. A vacuum generator 54 (e.g., a turbomolecular pump) provides a vacuum suction system so that the bonding process in the high temperature bonding furnace 1 can be carried out in a vacuum (e.g., a high vacuum or an ultra-high vacuum). The pressing force generator 28 is located in a separate housing so that a larger unit can be accommodated in the housing if necessary. The input and / or output devices 48, 46 are outsourced to the user terminal 45, which includes the PLC 44 and the input / output 48, 46.

[0120] See also Fig.26 , a flow chart of a joining process 200 is shown. In a first step 210, the system is filled with a workpiece 50 or a batch of one or more workpieces. This is usually performed by a user, but can also be automatic. In step 220, the system 1 is parameterized, whereby different specifications (such as, for example, the material and joining surface of the workpiece or batch of workpieces 50) can be stored in the control device 44 using an input device 48. For example, the expected compression of the workpiece 50 or the batch of workpieces can also be entered as a percentage or a distance (for example in millimeters). For example, temperature specifications can also be stored. The parameters entered for step 220 can be transmitted to the control device 44. The control device 44 can then generate a set of control parameters. After closing the filling opening 11, the joining furnace 1 is now ready for operation. The processing stage 230 starts with a temperature parameter provided, for example, by the control device 44. The press 20 is then prepared. This can include applying a pre-pressure to the press device 20 so that the base 18 is displaced or deformed or preloaded, and the press device 20 can therefore take an initial position. During this process, or even before or after it, the workpiece 50 is heated in a heating phase 230 , during which the press plate heating devices 62 , 64 are heated and heat is uniformly transferred to the workpiece 50 by conduction.

[0121] Then in step 240, a pressing process or a bonding process is performed; if necessary, this can be monitored and adjusted by the automatic process control 44. Sensors 4, 5, 42 can provide sensor signals processed by the process control 44. The prepared control parameters can be checked or adjusted in response to the sensor signals provided by the sensors 4, 5, 42. If the control parameters are adjusted, the bonding process 240 is continued in a modified form using the adjusted control parameters. This can be implemented as a control loop and can be performed iteratively, for example, so that an improved parameter configuration can be set during the bonding process and an improved bonding result can be achieved. In other words, in one example, it is specified that the workpiece 50 is compressed by X%. This occurs within a specific time, which can be calculated by the control system. An initial pressing force is applied and the actual pressing process starts in step 240. During the pressing process 240, it can be checked whether the corresponding distance per unit time has been reached, and the pressing force can be changed if necessary.

[0122] Here, for example, an increased pressing pressure can be stored, which can be adaptively adjusted during the joining process 240. The maximum or required deflection of the pressing cylinder 24 to a desired end value can also have been stored in the set of original control parameters. During the checking or adjustment of the control parameters, it can also be determined whether the desired final value for the deflection of the pressing cylinder 24 and / or the deformation of the workpiece can be achieved without exceeding a pressing pressure at which the workpiece or the batch of workpieces 50 may be damaged or excessively deformed.

[0123] In step 250, the workpiece or batch of workpieces 50 can be subjected to further processing. This can be further tempering, further heating or cooling at a defined temperature constant. After post-processing 250, the workpiece or batch of workpieces 50 is sufficiently cooled and can be removed from the system 1 in step 260.

[0124] In the present description, functional solutions can therefore be explained in numerous examples, which also include features that can be combined individually with one another, regarding how the uniformity of the heat distribution in the workpiece 50 can be improved and / or the time required for heating the workpiece 50 can be reduced by integrating the heating devices 62, 64 directly into the press plates 36, 38 (for example by conductive heat transfer). In addition, it is now possible to process materials by means of diffusion bonding that were previously not open to this process due to the required low temperature range.

[0125] It has proven to be advantageous for this purpose to conduct the heating of the pressing plates 36, 38 by one or more heating elements 74, 74a, 74b, 74c, which can be made of ceramic or another heating material. The heater 62 is preferably a resistive heater integrated in an electrically insulating manner. A circumferential heater 14 can be provided for support so that the temperature at the edges and corners of the component 50 is equalized. The support or the circumferential heating can be moved vertically. If necessary, the support heater can be divided into different temperature zones. If necessary, a water-cooled pressure distribution plate 36, 38 can be used. A flexible heater connection 100 can be realized, for example, via a copper strip 112.

[0126] One objective is to make diffusion bonding of large format components (perhaps larger than DINA3 format) more efficient. Efficiency refers to the energy consumption per welding cycle and the duration of the joining cycle. This can be achieved by heating the components to be joined via conduction (ie, contact heating).

[0127] As the freedom in design due to additive manufacturing methods increases, there is also a desire to expand the size of previous component volumes. Although the build volume of powder bed systems has also grown in recent years, with currently commercially available measuring 500×280×850mm 3 With systems of additive manufacturing, the build rate is still low, especially when it comes to massive components such as molds etc. An alternative additive building process is material deposition with directed energy deposition (DED) using an electric arc and a wire as filler material. High accumulation rates in the range of several kilograms per hour are possible. However, the disadvantage here is the insufficient possibility of producing internal channels. In principle, these are feasible, although the dimensional accuracy and dimensional stability have so far been sufficient only for cooling channels. Functions such as the distribution of plastic blocks or heat exchanger structures are currently not feasible. Therefore, diffusion bonding has been used today for such components. The scale of diffusion bonding systems relative to the dimensions of press plates currently available on the market is in the range of more than one meter.

[0128] One purpose of this specification is to improve and refine the design boundary conditions of the heating concept for diffusion bonding, which homogenizes the heat input into the components and achieves it by contact heating (i.e., heat conduction) if possible. The purpose is to achieve processing temperatures of up to 900°C and the possibility of dynamic force application, for example. In addition, the system is designed for use in a high vacuum furnace. Conduction heating avoids the loss of heat transfer by radiation and emission-dependent heat transfer that occurs in a vacuum, whereby the energy input into most of the plate-like bonding components is quite more efficient, homogenized and faster. As a result, the heating system can significantly increase the energy efficiency and significantly shorter cycle times during diffusion bonding. The cost of the diffusion bonding process is greatly reduced, the quality of the components is improved, and the competitiveness of the process is improved.

[0129] Of particular importance is the thermal conduction or heating of the components 50 to be joined. In particular for non-ferrous metals with a joining temperature below 1,000°C, the previously established heating by thermal radiation in a vacuum is an inefficient process. Due to the low emissivity, only very low heating rates are possible, which has a negative impact on the cycle time and therefore the costs of the process. Direct (conductive) component heating by heat conduction via the press plates 36, 38 accelerates the energy input into the components 50 and at the same time enables a more homogenous temperature distribution, since the heat is introduced uniformly over the largest surface of the plate-shaped components, whereas conventional heating is essentially carried out via the outer edges, resulting in a gradient between the outside and the center of the component due to the path length, which, if not equalized by waiting (extended cycle time), leads to differences in the quality of the composite material formed.

[0130] The dimensions of the pressing plate surface may advantageously be at least 300 x 500 mm or more. The cyclic load capacity of the system 1 is preferably 0.1 Hz or more, or even 0.5 Hz or more, or even 1 Hz or more. -5 Operation in a fine or high vacuum of mbar is advantageous. ≥ 7 N / mm can be achieved on the system side 2of a transmittable surface pressure. For example, a surface pressure of at least 0.1 MPa, preferably at least 0.5 MPa, can be achieved on the component 50 using the pressing plates 36, 38. For example, the surface pressure can reach a maximum of 50 MPa, possibly a maximum of 40 MPa. Alternatively or cumulatively, a force of 1 ton or more can be applied to the component 50 by means of the pressing plates 36, 38, in which case the system can even be used for power-assisted brazing (PAB). Preferably, a force of 5 tons or more can be applied to the component 50 by means of the pressing plates 36, 38. If necessary, the force applied to the component 50 by means of the pressing plates 36, 38 can be up to 5,000 tons, for example also up to 4,000 tons. A lower surface pressure of less than 0.1 MPa or the application of a force of less than 1 ton is not to be understood as a pressing force or the application of a pressing force for the purposes of the present application. For example, a process for wafer bonding (i.e., bonding of semiconductor substrates) is not a pressing process within the meaning of the present application. In contrast, the field of diffusion bonding or force welding within the meaning of the present application is subject to the relatively high pressure conditions described above.

[0131] Three main factors are important for the diffusion bonding process on the system side: the environment in which the joining occurs, the way in which the force is applied, and the heating concept. If the geometry of the components is considered in addition to the process, the system concept, i.e., the design of the welding system, must also be considered. In principle, the components to be joined in a vacuum can be heated in a variety of ways (by means of thermal radiation, laser or electron beam, convection, direct resistance heating, induction, heat conduction (conduction) or a combination of individual variants). Beam-based processes (laser or electron beam) are particularly suitable for rotationally symmetrical small parts, but have the following disadvantages: an additional axis (a rotation axis for rotating the workpiece) must be provided in the system. Applying direct current to the components to be joined leads to direct resistance heating, but due to these electrical variables, the size of the component is also limited here. If the direct current is replaced by a pulsed current flow, a larger current can be converted. In this case, sparks also occur compared to plasma spark sintering. Since the direct current passes through these components, only conductive materials can be joined, and thus a homogenized distribution of the electric field must be ensured, especially for large components. Induction heating is used more frequently, especially in history. Here, heat is generated directly in the area of ​​the component surface, which heats the component quickly. Diffusion bonding systems for large-scale production (e.g. for valve disc seals, with production figures of 3.1 million units per year) were already equipped with induction heating in the 1970s. The penetration depth can be adjusted by setting parameters such as frequency or current. However, the component-inductor distance or the shape of the inductor also influences the heat input and thus the temperature distribution in the component. A disadvantage is that the inductor must be adapted to the component geometry for optimal heating and not all materials can be heated inductively. Induction heating is still suitable for thin component geometries, for example.

[0132] However, with regard to component dimensions, the current trend is towards solid, flat components with large dimensions in at least two spatial directions, for example, plate heat exchangers or injection molds. For this reason, the latest generation of diffusion bonding systems are typically designed according to the "furnace principle". This means that a vacuum furnace system forms the basis of the welding system, in which a "press system" 20 must also be integrated. Heating is carried out by thermal radiation, most often by means of resistive heating elements. Infrared radiators can also be used for small components. Since there is no convection in a vacuum, the heat transfer is limited to radiative heating between the heating element and the component. The main influencing factor in radiative heating is the degree of absorption of the thermal radiation, which depends on the conditions of the component surface. According to Kirchhoff's radiation law, which states that radiation absorption and emission correspond to each other at a given wavelength, usually only the emissivity is specified.

[0133] Molybdenum can be considered as a heating element material in air and vacuum. The oxide layer on molybdenum dissolves in vacuum and therefore achieves high emissivity in vacuum, which is why this material is used for heaters. In addition, two typical material groups of parts to be joined are included, aluminum and steel. Pure steel has a higher emissivity. This is temperature-dependent and increases with temperature. In contrast, the value of aluminum is significantly lower. Clean aluminum has very low values, while oxidized aluminum surfaces have values ​​that are only 2 to 3 times lower than those of steel. From the point of view of radiation technology, the oxidized surface is optimal in terms of absorbing thermal radiation, but not from the point of view of diffusion bonding because the oxide layer represents a diffusion barrier. The behavior of copper materials is similar to that of aluminum. This means that heating high thermal conductivity materials only by radiation may not be sufficient for welding processes. For materials with a low tendency to react with the environment, in addition to pure radiation heating (additional convection components), heat transfer by means of partial pressure in the working chamber can also be increased. In the case of aluminum and titanium alloys, the presence of impurities (e.g., oxygen / nitrogen) in the gas leads to reactions with the surface and the formation of layers, which in turn have a diffusion-inhibiting effect and can adversely affect the mechanical and technical properties.

[0134] Another disadvantage of the above-mentioned heating concept is the temperature uniformity in the component. In principle, heat is always transferred via the component surface and conducted from the component surface to the interior of the component by heat conduction. Therefore, a temperature gradient is formed in the component 50 during the heating process, which leads to uneven expansion and internal stresses. Depending on the thermal conductivity of the material to be joined, this situation must be dealt with by a correspondingly slow heating rate, also in order to avoid heat accumulation and overheating of the component surface. In addition to the material, the aspect ratio of the component plays a key role here. The above-mentioned concept mainly realizes heat input via the side surface of the component. This means the maximum heat conduction path for plate-shaped components. However, such component geometries with a low aspect ratio are currently in increasing demand (plate heat exchangers, mold inserts, etc.). Therefore, heat input via the base and top surface shortens the conduction path and therefore allows higher heating rates.

[0135] The pressing plate for the diffusion bonding system realizes the task of applying the pressing force into the component and distributing the force as evenly as possible on the component or the joining surface. This initially leads to basic requirements for the mechanical properties of the plates 36, 38, such as a low elastic modulus and sufficient compression and flexural strength. Due to the use in the high vacuum furnace system, these characteristics must be guaranteed over the entire application temperature range. In addition, the pressing plate material must be suitable for vacuum (high vapor pressure). In addition, the ideal pressing plate material must have a low specific heat capacity, because from an energy point of view, the pressing plate represents a dead mass that must be heated and cooled again during the processing. Another requirement is fatigue strength under dynamic load within the pressure threshold range.

[0136] In the field of metallic materials, titanium-zirconium reinforced molybdenum (TZM) is a good starting point and is used in many areas as a load-bearing element in the heating zone of a vacuum furnace system. In addition to its thermal and mechanical properties, its behavior during machining is comparable to that of CrNi steel. Thus, TZM is also of interest for this description. The disadvantage of TZM is its 10.2 g / cm 3 The relatively high density, high thermal conductivity characteristic of metals and the high costs associated with production.

[0137] From a mechanical point of view, all-ceramic press plates are ideal press plate materials. For example, silicon carbide ceramics have a high elastic modulus of 350-450 GPa and also have a compressive strength of more than 2500 MPa, resulting in a very dimensionally stable material. The main disadvantage of ceramics is the high cost of processing in the sintered state.

[0138] Steel materials such as heat-resistant steel 1.4828 are conceivable as the pressing plate material. However, at the desired application temperature of 900° C., the pressure drop is less than 5 N / mm 2 Low creep rupture strength is an exclusion criterion.

[0139] An alternative to the foregoing is a ceramic-based fiber composite (CMC). Similar to carbon fiber reinforced plastics, carbon fibers or ceramic fibers are embedded in a ceramic matrix. This retains the excellent properties of ceramics, such as temperature resistance and compressive strength, but the fiber reinforcement increases the fracture toughness required for dynamic use.

[0140] Carbon fiber reinforced graphite (CFC) can be used in diffusion bonding systems where static forces are applied. Due to the high thermal conductivity compared to other fiber composites considered here, more energy is extracted from the heating zone.

[0141] Carbon fiber reinforced silicon carbide is a composite material that has not yet been used in diffusion bonding systems.

[0142] Alumina fiber reinforced oxide ceramics have very low thermal conductivity of 0.4W / mK-2.7W / mK and a relatively low elastic modulus (40GPa), which leads to excellent insulation and very good pressure distribution. However, about 25N / mm 2 The low compressive strength is critical for this material.

[0143] The general requirements for the heater material for the heating means 62, 64 are essentially high electrical resistance, high melting temperature (which must significantly exceed the application temperature) and low vapor pressure in order to minimize heater wear in vacuum operation. From a design point of view, a low thermal expansion coefficient is also desirable. In the field of metallic materials, molybdenum stands out as a heater material alongside tungsten. With a melting temperature of 2623°C, a specific resistance in the range of 0.056·10-6-0.452·10-6Ωm (20-1500°C) and an expansion coefficient of 5.8·10-6K-1, it is possible to achieve temperatures of up to 1600°C with very high vacuum quality.

[0144] Alternatives to this are nickel-based alloys which have higher mechanical strength and toughness with comparable electrical resistance (e.g.: 0.103·10-6-0.114·10-6Ωm (20-1000°C)). However, due to the relatively low melting temperature (1370-1425°C) and the relatively high expansion coefficient of 16.9·10-6K-1 (1000°C), the scope of application is limited.

[0145] In addition to metallic materials, it is also possible to realize resistive heating with non-oxide ceramics such as SiC etc. These are now also commercially available as heating plates for temperatures up to 1100°C, allowing a uniform temperature distribution to be achieved. However, the high brittleness and sensitivity to bending stresses are critical for the planned applications.

[0146] Graphite is another alternative for furnace systems; the advantages here are the relatively low material price and high electrical resistance. However, graphite is only suitable to a limited extent for use in a high vacuum, since evaporated carbon can contaminate the parts to be joined and cause material changes.

[0147] It is clear to the skilled person that the embodiments described above are to be understood as exemplary and that the invention is not limited to them but may be varied in many ways without departing from the scope of protection of the claims. Furthermore, it is clear that even if these features are described together with other features, these features alone define essential parts of the invention, regardless of whether they are disclosed in the description, the claims, the drawings, etc. In all the figures, the same reference numerals denote the same objects, so that the description of an object which may be mentioned only in one or at least in relation to all the figures may also be transferred to these figures, with respect to which the object is not explicitly described in the description.

[0148] List of reference numerals:

[0149] 1High temperature bonding furnace

[0150] 3 motor units

[0151] 4. First sensor device

[0152] 5 Another sensor device

[0153] 6 Press-on support area of ​​housing 12 7 Support frame element (horizontal, bottom) 8 Substructure 9 Support frame element (vertical)

[0154] 10 Support frame elements (horizontal, top) 11 Filling and / or removing openings

[0155] 12 Shell

[0156] 14 Furnace heating device

[0157] 15 Heating chamber

[0158] 16 Insulation

[0159] 18 Press the base

[0160] 20 Pressing device

[0161] 22 Pressure distribution element

[0162] 24 Press cylinder

[0163] 26 transmission parts

[0164] 28 Press Pressure Generator

[0165] 29 Reverse press punch

[0166] 32 Press Punch

[0167] 34 Workpiece holder

[0168] 36 Press Plate

[0169] 37 Pressure distributor

[0170] 38 Reverse pressing element

[0171] 42 Second sensor device

[0172] 44Programmable Logic Controller

[0173] 45 User terminals, input and output devices with PLC

[0174] 46 Output device

[0175] 48 Input devices

[0176] 50 artifacts

[0177] 54 Vacuum generator (vacuum pump)

[0178] 62 Pressing plate heating device in pressing plate

[0179] 64 Press plate heating device in workpiece holder

[0180] 66, 66a connecting protrusion, protrusion collar

[0181] 67, 67a contact lip edge

[0182] 68 Retainer for fastener

[0183] 71 Pressing side pressing plate element

[0184] 72 Heating element top layer

[0185] 72a Transverse housing of heating element 74

[0186] 74, 74a, 74b, 74c heating element

[0187] 76 Heating element bottom layer

[0188] 76a Transverse housing of heating element 74

[0189] 77 Workpiece pressing plate element

[0190] 78 Connectors

[0191] 80 Fasteners, screws

[0192] 82 floor tiles

[0193] 100 contact devices

[0194] 102 Heating element fixture

[0195] 104 Flexible compensation element

[0196] 106 contact elements

[0197] 108 Bolt Retainer

[0198] 110 bolts

[0199] 112Connecting elements, such as copper tape

[0200] 114 Implementation

[0201] 116 external contacts

[0202] 200 Joining process

[0203] 210 Fill

[0204] 220 Parameterization

[0205] 230 process stage

[0206] 240 Pressing or joining steps

[0207] 250 If necessary, post-process

[0208] 260 Uninstall System

Claims

1. A high temperature bonding furnace (1), the high temperature bonding furnace (1) being used, for example, for diffusion bonding of bonding materials such as metal and metal workpieces (50), the high temperature bonding furnace (1) comprising: Heating chamber (15), a workpiece holder (34) arranged in the heating chamber for holding a workpiece (50) to be processed in the bonding furnace; a pressing device (20) arranged and prepared to apply a pressing force to the workpiece, the pressing device comprising a pressing plate (36) for uniformly applying the pressing force to the workpiece, It is characterized in that The press plate is equipped with a press plate heating device (62) for heating the press plate and / or the workpiece.

2. A joining furnace (1) according to the preceding claim, in, The pressing plate heating device (62) is integrated in the pressing plate (36), for example, the pressing plate heating device (62) and the pressing plate (36) are completely integrated together, and / or The pressing plate (36) is a multi-part pressing plate, wherein, for example, the pressing plate comprises a workpiece side element (77) and a pressing side element (71), and / or Wherein, the pressing plate heating device (62) is arranged between the workpiece side layer (77) and the pressing side layer (71).

3. A joining furnace (1) according to any one of the preceding claims, The bonding furnace (1) further comprises a flexible connection connector (100) for connecting the pressing plate heating device (62) to an energy source.

4. The joining furnace (1) according to any one of the preceding claims, wherein: The press plate heating device (62) provides a conductive heat output, i.e., the press plate heating device (62) is a conductive press plate heating device, and / or, wherein the pressing plate heating device (62) is arranged to be electrically operable so that when the pressing plate heating device (62) is supplied with electricity from the energy source, the pressing plate heating device (62) generates heat, and / or, The pressing plate heating device (62) is arranged to allow fluid to flow through the pressing plate heating device (62), so that when the pressing plate heating device (62) is supplied with hot fluid from the energy source, the pressing plate heating device (62) generates heat.

5. A joining furnace (1) according to any one of the preceding claims, in, The pressing device (20) comprises a hydraulic device which serves as a pressing force generator (28) and builds up the pressing force by building up hydraulic pressure, and / or Wherein, the pressing device (20) comprises an armature shaft, and / or Wherein, the pressing device (20) comprises a pressing cylinder (24), and / or Wherein, the pressing device (20) comprises: A plurality of pressing punches (24), in particular two, three, four or more pressing punches.

6. A joining furnace (1) according to any one of the preceding claims, in, The high temperature bonding furnace comprises an outer frame (7, 8, 10), and Wherein, the pressing device (20) is arranged on the outer frame and / or supported on the outer frame, and / or The outer frames (7, 8, 10) are designed to be movable and / or deformable.

7. A joining furnace (1) according to any one of the preceding claims, The bonding furnace (1) further comprises a pressing abutment (18), which is prepared in such a way that a lateral displacement and / or deformation of the pressing abutment (18) occurs by means of the pressing force applied by the pressing device (20) to the workpiece (50), and / or in, The pressing device (20) is configured in such a way that a prestress can be built up to the supporting frame element (10) during the pressing operation, and / or wherein the workpiece holder (34) is used as a counter-pressing element (38), and / or The pressing device (20) presses the workpiece (50) against the workpiece holder (34).

8. A joining furnace (1) according to any one of the preceding claims, The joining furnace (1) is prepared for carrying out a joining process of preferably metals or metal workpieces at a temperature of the metal workpieces of 1200° C. or less, preferably 1000° C. or less, further preferably 950° C. or less and / or at a temperature of 450° C. or more, preferably 500° C. or more, further preferably 550° C. or more or also 600° C. or more, and / or The joining furnace (1) is prepared for a joining process of preferably non-metallic workpieces such as plastics, ceramics or corresponding workpieces at a temperature of 350°C or lower, preferably 300°C or lower, further preferably 250°C or lower or also 200°C or lower and / or at 80°C or higher, for example 100°C or higher, preferably 120°C or higher and further preferably 140°C or higher.

9. A joining furnace (1) according to any one of the preceding claims, The bonding furnace (1) further comprises a furnace heating device (14) for emitting radiant heat into the heating chamber (15).

10. A method for diffusion bonding in a high temperature bonding furnace (1), for example according to any one of the preceding claims, comprising the following steps: filling the joining furnace with workpieces (50), applying at least one pressing plate (36) of a pressing device (20) to the workpiece, The workpieces of the main components are heated to the joining temperature by means of a press plate heating device (62), The workpiece is pressed by a pressing device (20) to perform a diffusion bonding process.

11. The method according to the preceding claim, further comprising the steps of: During the pressing process, the pressing plate (36) is tempered or heated by means of the pressing plate heating device (62) in order to make the temperature distribution in the workpiece (50) uniform.

12. A heatable press plate (36) for use in a high-temperature joining furnace (1), for example according to any one of the preceding claims, The pressing plate is prepared to uniformly apply a pressing force to a workpiece (50) placed in the high-temperature bonding furnace; It is characterized in that The press plate is equipped with an integrated press plate heating device (62) for heating the press plate and / or the workpiece.

13. A heatable press plate (36) according to the preceding claim, in, The pressing plate heating device (62) is integrated in the pressing plate, for example, the pressing plate heating device (62) and the pressing plate are completely integrated together, and / or Therein, the pressure plate is a multi-part pressure plate, so that, for example, the pressure plate comprises a workpiece-side element (77) and a pressure-side element (71), and / or The pressing plate heating device (62) is arranged between the workpiece side layer (77) and the pressing side layer (71).

14. A heatable press plate (36) according to any one of the preceding claims, comprising a multi-part press plate according to the preceding claims, in, Each part of the pressure plate consists of the same matrix material and has only different doping from one another.

15. A heatable pressing plate (36) according to any one of the preceding claims, in, The pressing plate comprises a ceramic material, and / or Wherein, the workpiece side layer (77) and / or the pressing side layer (71) include ceramic material or consist of ceramic material, and / or Wherein, the pressing plate heating device (62) comprises ceramic material or metal material or is composed of ceramic material or metal material.

16. A heatable press plate (36) according to the preceding claim, in, The ceramic material comprises at least one of carbon fiber reinforced graphite, carbon fiber reinforced silicon carbide, titanium zirconium reinforced molybdenum, silicon carbide or alumina fiber reinforced oxide ceramics, or the workpiece side layer (77) and / or the pressing side layer (71) are made of one of the above materials, and / or Wherein, the pressing plate heater (62) comprises tungsten, molybdenum, such as At least one of a nickel-based alloy, a non-oxide ceramic such as silicon carbide or graphite, or carbon fiber reinforced carbon, or a tungsten, molybdenum, such as The present invention is composed of at least one of a nickel-based alloy, a non-oxide ceramic such as silicon carbide or graphite, or carbon fiber reinforced carbon.

17. A heatable pressing plate (36) according to any one of the preceding claims, in, The pressing plate heating device (62) has a plate-shaped design, and / or Wherein, the pressing plate heating device (62) has a curved design, and / or The press plate heating device (62) has a channel or track, and the channel or track passes through the press plate evenly so that the material of the press plate is at most at a distance from one of the channels or tracks, which distance corresponds to twice or less the width of the channel or track.

18. A heatable pressing plate (36) according to any one of the preceding claims, in, The pressing plate heating device (62) is arranged to be electrically operable so that when electric current is applied to the pressing plate heating device (62), the pressing plate heating device (62) generates heat, and / or The pressing plate heating device (62) is arranged so that a fluid can flow through the pressing plate heating device (62), so that when hot fluid is applied to the pressing plate heating device (62), the pressing plate heating device (62) generates heat.

19. A heatable pressing plate (36) according to any one of the preceding claims, in, The pressing plate heating device (62) comprises at least two heating plates (74, 74a, 74b, 74c), and / or, The press plate heating device (62) comprises a connecting piece (78) for connecting two or more partial areas, such as heating plates (74, 74a, 74b, 74c), wherein the connecting piece comprises graphite or consists of graphite, for example.

20. The heatable press plate (36) according to the preceding claim, in, The connecting piece (78) is designed to be reversibly deformable so that the connecting piece (78) deforms, for example becomes wider, when a pressing force is applied, and so that the connecting piece (78) improves or establishes electrical contact between the sub-regions (74, 74a, 74b, 74c) of the pressing plate heating device (62).

21. A heatable pressing plate (36) according to any one of the preceding claims, The pressing plate (36) further comprises a pressure balancing layer (104), in, The pressure balancing layer is designed to be full-surface and is arranged to be flexible or compressible, and / or Wherein, the pressure balancing layer is arranged adjacent to the pressing plate heating device (62), and / or Wherein, the pressure balance layer is a graphite foil.

22. A heatable pressing plate (36) according to any one of claims 13 to 21, in, The pressing side layer (71) is formed as a floor tile carpet, for example, a ceramic tile carpet, and / or Wherein, the pressing plate heating device (62) is arranged in the heating plane, and / or The tiles (82) are arranged between the components of the press plate heating device (62).

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