Device for connecting a component to a substrate

Abstract

Device for connecting a component to a substrate, with a chamber divisible into at least two parts, wherein a stamp (11, 111) is provided on a first part (1), and a counter-stamp (31) is provided on a second part (3), wherein the first part (1) has a wall with an edge which can be brought into contact with an opposite edge of a wall of the second part (3) in order to close the chamber, wherein the counter-stamp (31) can be loaded with starting materials in an open state of the chamber, and in a closed state of the chamber, pressure can be exerted on the starting materials provided between the stamp (11, 111) and the counter-stamp (31) via the stamp (11), wherein In the closed state, the first part (1) and the second part (3) can be locked together by means of a positive locking mechanism, so that opening of the chamber by separation of the first part (1) from the second part (3) is prevented, characterized by the fact that Each edge has a recess (131) and / or a projection (137; 39) with a hole (133a, 133b; 391) which can be brought into contact with a projection (39; 137) and / or a recess (131) of the opposite edge, wherein a cross-section of the hole (133a, 133b) of the projection (137a, 137b) of the wall of the first part (1) in a brought-in state at least partially overlaps with a cross-section of the hole (391) of the projection (39) of the wall of the second part (3), and the positive locking can be achieved by means of a pin (135) guided through both holes (133a, 133b; 391).

Description

[0001] The invention relates to a device for connecting a component to a substrate. BACKGROUND OF THE INVENTION

[0002] With the increasing need of the electronics industry for the development of efficient and high-temperature resistant components such as chips, the sintering of a bonding layer between the component and the substrate is gaining in popularity.

[0003] Sintering is known, among other things, as a process for manufacturing metal or ceramic parts. In this process, a fine- or coarse-grained green body is created by compressing a powdered starting material. This green body then undergoes a subsequent heat treatment to achieve its final shape and become a solid workpiece.

[0004] Sintering, as defined in the application and used in the manufacturing and processing of components such as semiconductor chips, refers to a similar process of pressing a component and a substrate together under predetermined pressure and temperature for a specific period of time, thereby creating a bond between the two elements. The current state of the art involves the use of pasty materials such as silver or copper paste, or even nanostructured platelets, which serve as a connection between the chip and the substrate and are sintered by the application of pressure and temperature. Such sintering as a method for bonding a component to a substrate is known and has proven advantageous compared to previously used tin- or lead-based soldering processes.

[0005] For such a sintering process, certain parameters, such as a set temperature, pressure, and holding time, must be defined to ensure effective bonding of the component to the substrate. These parameters can be determined based on experiments, depending on the requirements. In such sintering processes, a bonding agent can also be advantageously used, applied between the component and the substrate. The thickness of the bonding agent layer can then be another parameter. A silver paste is preferably used as such a bonding agent.

[0006] Preferably, during a sintering process, the binder, e.g., a silver paste, does not undergo a phase transformation, as is the case in tin- and lead-based soldering processes. Through appropriate temperature and pressure application, particles of the binder diffuse into the surface of the substrate and the component to be bonded. This creates a surface-to-surface bond instead of a phase-change bond.

[0007] Effective fastening requires a parallel, uniform force distribution across the component's surface, and this must be ensured. Therefore, a custom force application component is a preferred solution for modern electronics manufacturers, guaranteeing a high-quality connection. Custom force application means a separate tool for each component-substrate pairing, which can result in high tooling costs.

[0008] The application of temperature and pressure is necessary to achieve an effective bond between the component and the substrate; otherwise, the quality of the bond could be poor or too slow for practical purposes.

[0009] The principle of this process does not involve a phase change of the bonding agent (e.g., silver paste), as is the case with tin- and lead-based soldering processes. Through appropriate temperature and pressure application, silver components diffuse into the surface of the substrate and the component being bonded. This results in a surface-to-surface connection, rather than a phase change contact.

[0010] The terms "die attach" or "die packaging" are also commonly used for this type of process.

[0011] German patent application DE 10 2013 101 124 A1 discloses a device and a method for sintering a product. The sintered product comprises a component and a substrate. To join these, the sintered product is placed in a device with a press table and a press ram. By increasing the temperature using a heating device, a pressure element in the press ram expands, thereby exerting pressure on the sintered product. This bonds the component to the substrate.

[0012] German patent application DE 10 2015 120 156 A1 discloses a device for the material-locking connection of connection partners of a power electronics component. Here, a dimensionally stable frame acts on one of the connection partners, while an elastic cushion acts on a second connection partner to build up the pressure required for joining.

[0013] Prior art systems require an external counterforce mechanism that holds the substrate together with the support, forming a force circuit. Hydraulically actuated counterforce mechanisms are known to be used, typically applying a counterforce against gravity to compensate for the compressive forces required for sintering. While such systems are stable, precise, and adjustable via the counterforce, they are heavier and feature a complex pressing mechanism.

[0014] German patent application DE 10 2021 126 716 B3 describes a sintering or diffusion brazing device for joining components and shows in the figures an evacuable process chamber with two parts: a base body and a lid. An upper tool is provided as a punch on the lid, and a lower tool as a counter-punch on the base body. The base body and the lid have walls and edges for closing the process chamber. When the process chamber is open, the lower tool can be loaded with starting materials, and when closed, pressure can be applied via the upper and lower tools. When the process chamber is closed, the base body and the lid can be locked together by means of a positive locking mechanism, thus preventing the process chamber from being opened by separating the base body and lid.

[0015] The object of the invention is to provide a device for connecting a component to a substrate which, despite its small size, makes it possible to set a connection pressure and compensate for forces that occur.

[0016] The object of the invention is achieved by a device for connecting a component to a substrate according to claim 1 or claim 6. Advantageous embodiments are described in the dependent claims.

[0017] According to the invention, a device for connecting a component to a substrate is provided with a chamber that can be divided into at least two parts. A punch is provided on a first part, and a counter-punch is provided on a second part. The first part has a wall with an edge that can be brought into contact with an opposite edge of a wall of the second part to close the chamber. The counter-punch can be loaded with starting materials when the chamber is open. When the chamber is closed, pressure can be exerted on the starting materials located between the punch and the counter-punch via the punch. In the closed state, the first part and the second part can be locked together by means of a positive locking mechanism, thus preventing the chamber from being opened by separating the first part from the second part.

[0018] The chamber is locked in the closed state by means of a positive locking mechanism, so that separation of the first part and the second part is prevented.

[0019] Thus, unintentional opening of the chamber, for example due to the pressure generated between the punch and the counter-punch, is prevented. The positive locking mechanism is established after the chamber is closed and the punch and counter-punch are brought together, thereby locking the first part to the second. Pressure is then applied to the punches, which transfer this pressure to the substrate located between the punch and counter-punch. This pressure, combined with the punch surface area, results in a force that is absorbed by the positive locking mechanism between the first and second parts. This eliminates the need for a counter-mechanism, such as a hydraulic device.

[0020] This creates an internal force circuit that utilizes positive locking. This reduces the overall complexity of the machine, allowing for a smaller and more robust machine structure. It eliminates the need to pre-tension, calibrate, and install an external mechanism. Furthermore, an internal positive locking mechanism can compensate for dynamic changes in process forces. This also reduces the costs associated with manufacturing, assembly, and operating the machine.

[0021] Each edge has a recess and / or a projection with a hole, which can be aligned with a projection and / or recess of the opposite edge. In this aligned state, the cross-section of the hole in the projection of the wall of the first part overlaps at least partially with the cross-section of the hole in the projection of the wall of the second part. The positive fit can be achieved by means of a pin inserted through both holes.

[0022] According to the invention, a "positioned state" is to be understood as such that the mutually facing surfaces of the recess and the projection touch each other. Thus, the holes are in a predetermined position in which the pin can be easily inserted.

[0023] At least one of the holes can have a cross-section with a greater length than width. The length of the cross-section extends in one opening direction of the chamber.

[0024] This design makes it easier to insert the pin into the hole to reliably create a positive fit, as there is some play for the pin.

[0025] In the installed state, the central axis of the hole of the projection of the wall of the first part may deviate from the central axis of the hole of the projection of the wall of the second part.

[0026] Since it is not necessary for the axes of the holes in the first part and the second part to be exactly aligned, larger tolerances are permissible, which makes machining possible in a fast and cost-effective manner.

[0027] In the closed state of the chamber during pressure exerted by the plunger on the counter-plunger via the starting materials, the pin is clamped between an inner wall section of the hole in the projection of the second part, directed towards the first part, and an inner wall section of the hole in the projection of the first part, directed towards the second part, whereas in a pressure-free state the pin can be freely inserted into and removed from the holes.

[0028] The term "closed state of the chamber" means that the edges of the walls of the first and second parts are brought together until the opposing surfaces of the projections and recesses touch. This also corresponds to the "engaged state" defined above. However, when pressure is applied, the contacting surfaces of the projections and recesses are slightly separated until the pin is clamped as defined above. The "closed state of the chamber" also encompasses this situation.

[0029] At least the edge of the first part or the edge of the second part has a seal capable of creating a gas-tight state of the chamber in a closed state, regardless of any pressure exerted by the plunger on the counter-plunger via the starting materials.

[0030] This allows the interior of the chamber in the processing area to be pressurized with a process gas. Alternatively or additionally, a negative or positive pressure can be created in the processing area.

[0031] According to an alternative, the first part has a flange-like projection on its edge, directed towards the outer side of the chamber. The second part has a flange-like projection on its edge, also directed towards the outer side of the chamber. The positive fit is achieved by bringing a surface of the first projection, facing the second projection, into contact with a surface of the second projection, facing the first projection, and then attaching a clamp over both flange-like projections.

[0032] This type of positive locking mechanism represents an alternative to the type of positive locking mechanism with holes and pin defined above. Particularly under very high pressures during application, the high forces generated by the positive locking mechanism with holes and pin can lead to deformation, especially of the pin itself. A clamp applied externally via the flange-like projections then offers a very good alternative. Such a clamp can even be removed again without much effort in the event of deformation.

[0033] A surface of the first projection pointing away from the second projection and / or a surface of the second projection pointing away from the first projection may be chamfered.

[0034] Because of such beveled surfaces, the clamp can be guided more easily to create a positive fit.

[0035] Each inner surface of the clamp that is to be brought into contact with a chamfered surface of the first and / or the second projection can have a corresponding chamfer.

[0036] This design achieves a large area of ​​contact between the inclined surfaces of the projections and the mating surfaces of the clamp. Therefore, the positive locking mechanism can be maintained, particularly when a suitable surface with a high coefficient of friction is selected, without the need for additional clamping measures.

[0037] The clamp can be rotatably connected at one of its ends to the wall of the first part or the wall of the second part. The positive connection can then be established and released by rotating the clamp around the connection point.

[0038] The invention presents a method for fastening components that enables high power transmission and efficient operation at high temperatures. The present invention utilizes a machine structure with internal force locking using a positive locking tool. Furthermore, the device can compensate for differences in height and inclination of the product.

[0039] Furthermore, a positioning system can be used to bring the substrate into a desired position. This can also compensate for any disadvantages that may arise from the form-fit connection.

[0040] The form-fitting, sealed tool leads to a positive enhancement of the process in a chamber that may optionally accommodate process gases or a vacuum.

[0041] Further advantageous features and effects of the invention are described below.

[0042] The invention provides an adaptable tool for developing a surface mounting technology by joining surfaces made of different materials through pressure and a specific temperature acting on the upper surface of a component, by means of a form-fitting sealing / locking mechanism of the tool.

[0043] It is not necessary to provide a counterforce through an external system.

[0044] The tool can be designed as a sealed pressure chamber (under negative or positive pressure). The joining process can take place in a high-pressure gas or vacuum atmosphere. The chamber is closed by its own shape. A portion of the chamber—preferably the lower part—can be moved into position by means such as motors, or by hydraulic or pneumatic means.

[0045] The resulting compressive force exerted by the tool is balanced by a form-fitting mechanical internal element and / or a geometric shape, so that the force reaction takes a shorter path.

[0046] The substrate can consist of directly bonded copper or a similar ceramic substrate.

[0047] The pressure can be predefined, for example, at 40 MPa. The connection process can take place at a temperature setting between, for example, 20°C and 330°C for a defined time of, for example, 70-120 seconds.

[0048] The temperature can be maintained by a heating device in the chamber, preferably supplied directly at the pistons. Additionally, several heating devices can advantageously be used in the system.

[0049] Insulating layers and / or materials can be used in the chamber for the thermal insulation of sensitive components.

[0050] In the joining process, a protective film, e.g. made of PTFE material, can also be used to protect the semiconductor dies, which is preferably arranged using a roller mechanism.

[0051] The chamber can consist of several parts and be designed for multiple components (chips) in the form of multiple levels. Simultaneous processing on one level or on different, superimposed levels is also possible.

[0052] The size of the stamp, especially of its surface facing the opposite surface, can correspond exactly to the size of the component (chip). BRIEF DESCRIPTION OF THE FIGURES

[0053] Further advantages of the invention will also become clear from the following description with reference to the figures, which show a currently preferred embodiment. Fig. Figure 1 shows a device according to the invention for connecting a component to a substrate in an open state. Fig. 2a shows a side view of a positive locking mechanism according to a first embodiment of the invention, and Fig. 2b shows a sectional view of the Fig. 2a. Fig. Figure 3a shows a sectional view of the positive locking mechanism according to the first embodiment in a closed state of the device under load, and Fig. 3b shows a sectional view according to Fig. 3a in a closed state of the device without load. Fig. 4a shows a modification according to Fig. 3a, which is fitted with a seal, and Fig. 4b shows the modification according to Fig. 4b. Fig. Figure 5 shows an alternative form-locking mechanism. Fig. Figure 6 shows a detail of a stamp for joining a component to a substrate. Fig. Figure 7a shows a view of a stamp from the underside of the stamp. Fig. Figure 7b shows a side view of the punch, the shank of which is guided in a punch guide plate, and Fig. Figure 7c shows a view of the die shank guided in the die guide plate from a top view. Fig. Figure 8 shows a detailed view of a lower part of the device with a thermal separation device. Fig. Figure 9 shows an alternative device for thermal separation.

[0054] Embodiments of the invention are described by reference to the Fig. 1, Fig. 2, Fig. 3, Fig. 4, Fig. 5, Fig. 6, Fig. 7, Fig. 8 to Fig. 9 described. The figures are schematic, and some described details may have been omitted.

[0055] The device according to the invention is with reference to the Fig. The chamber is formed in the form of a chamber comprising an upper part 1 (first part) and a lower part 3 (second part). The chamber is essentially in the shape of a hollow cuboid with four side walls, a base, and a top wall. By separating the lower part 3 from the upper part 1, the chamber can be opened into two parts, the openings of which face each other.

[0056] The lower part 3 contains a press plate 31, also referred to as a product holder, which functions as a counter-punch. The press plate 31 serves to arrange raw materials such as a substrate, a sintering paste, and a component before a sintering process. A heating plate (heating device) 33 is located below the press plate 31. The heating plate 33 serves to transfer heat to the press plate 31 during a sintering process, thereby heating it.

[0057] The top will be based on the Fig. 1, Fig. 6 and Fig. 7 is described in more detail. A cylinder plate 19 is provided on the upper part 1 of the chamber at a top position, i.e., a position furthest from the opening of the upper part 1. The cylinder plate 19 has cylindrical bores in which pistons 117 are received. The cylindrical bores on the side of the cylinder plate 19 facing away from the respective piston 117 are connected to a pressure supply line 115. This piston-cylinder arrangement serves as a pneumatic adjustment device.

[0058] To actuate the pistons 117, a pressurized fluid, such as air, is introduced into the cylindrical bores in the cylinder plate 19 via the pressure supply line, thereby actuating the pistons 117. This actuation causes the pistons 117, together with a guide rod 113 provided on one side of the piston facing the lower part 3, to move towards the lower part 3 of the chamber. This direction is hereinafter also referred to as the "downward direction" or simply "downwards" and corresponds in the figures to a direction from the upper surface of the leaf to the lower surface.

[0059] While it is preferred to actuate all pistons simultaneously by pressurizing the fluid in the pressure supply line to a predetermined pressure, it is alternatively possible to provide means for actuating the pistons 117 individually. The pistons 117 are reset by applying a vacuum in the pressure supply line 115, which returns the pistons 117 and the guide rods 113 to their initial position.

[0060] Each piston 117 can be brought into contact with a shaft 111 of a punch via the guide rod 113. This is achieved by moving a rounded end of the guide rod 113, facing away from the piston 117, downwards against a flat end face of the shaft 111 facing the piston 117, through the actuation of the piston 117.

[0061] As can be seen in particular from the Fig. As can be seen in Figure 6, the guide rod 113 is guided through a hole in an upper plate 16 arranged above a piston guide plate 15. The upper plate 16 is also in contact with the inner walls of the upper part 1 such that a space located between the upper plate 16 and the cylinder plate 19 can be pressurized with overpressure or underpressure independently of the pressure in the pressure supply line 115. Preferably, a seal 8 is provided between the inner walls of the upper part 1 and the upper plate 16 for this purpose. The space between the upper plate 16 and the cylinder plate 19 is designated as the intermediate control chamber 119.

[0062] The shank 111 of the punch is cylindrical and guided through a hole in a punch guide plate 15. The diameter of the hole is dimensioned such that it slightly exceeds the diameter of the shank 111 of the punch, i.e., a clearance fit with interference is present. The clearance dimension is between 8 and 12 µm. A clearance dimension of 10 µm is preferred.

[0063] On the side of the shaft 111 facing away from the piston is a pressure body 11 of the ram, which is directed towards the pressure plate 31. In the Fig. Figure 1 shows seven stamps; however, the number of stamps is in no way limited and can be chosen arbitrarily. In particular, only a single stamp may be provided, although a larger number of stamps is preferred.

[0064] Each punch is manufactured from a single piece and consists of the shank 111 and the pressure body 11. The cylindrical shank 111 is guided by the punch guide plate 15 and, due to the clearance fit, can be tilted slightly. The maximum possible tilting angle can be adjusted by precisely defining the gap between the shank 111 and the hole in the punch guide plate 15.

[0065] Tilting is made possible by the fact that the guide rod 113 has a rounded end that can roll on the flat end face of the shaft 111 facing the piston 117. Because the shaft 111, and thus the punch 11, can tilt, it is possible to compensate for any inclination of the components to be sintered. This means that when the punch is brought into contact with a component that is not perfectly flat, it is able to adjust to the inclination of the component by tilting.

[0066] The pressure body 11 of the punch is cuboid in shape. Its underside surface, facing away from the piston, is called the pressure surface. The dimensions of the pressure surface slightly exceed those of the product to be sintered in order to reliably cover the component to be sintered completely even in the event of minor positional deviations, such as a slight rotation of the punch and thus of the pressure body 11.

[0067] The pressure body 11 of the punch is received in a recess 141, which is provided on the underside of a punch base plate 14 located below the punch guide plate 15. The thickness of the punch base plate 14, and thus of the recess 141, is dimensioned such that the pressure body 11 of the punch cannot completely dislodge from the recess during pressure application by the pistons 117. This is because the total height of the starting materials, and thus the required travel of the punch, is in the micrometer range, while the height of the pressure body and the recess is several millimeters.

[0068] The distance between the sides of the pressure body 11 and the inner walls of the recess 141 is greater than the distance between the shaft 111 and the inner wall of the hole. Therefore, it is impossible for the pressure body 11 to become jammed in the recess 141 due to the previously described possible tilting of the punch.

[0069] Since the plunger merely comes into contact with the guide rod 113 or the piston 117, but is not rigidly connected to it, the plunger remains in an extended position after pressurization, even though the piston 117 and the guide rod 113 are returned to their initial position by applying a vacuum to the pressure supply line. This condition is shown schematically in the Fig. 6 shown.

[0070] To detach the punch from the sintered product and return it to its starting position, the intermediate control chamber 119 is pressurized, and the punch is drawn back into its starting position due to the resulting pressure difference between the pressure body 11 and the intermediate control chamber. However, this creates a slight airflow between the shaft 111 and the inner wall of the hole, as well as between the walls of the pressure body 11 and the inner walls of the recess 141.

[0071] This slight airflow is negligible and ceases as soon as the upper surface of the pressure body 11 surrounding the shaft 111 comes into contact with the piston guide plate 15. Since the upper surface of the piston pressure body 11 is in contact with the underside of the piston guide plate 15, the end face of the shaft 111 is prevented from striking the guide rod 113 of the retracted piston 117. This has the advantage of creating a thermal separation between the hot piston (after the sintering process) and the piston.

[0072] Air drawn from a space 151 between the end face of the shaft 111 and the upper plate 16 also contributes to the resetting of the stamp, as shown from Fig. 6 is evident. The air present in the space 151 is already increased on the one hand by resetting the guide rod 113 by creating the negative pressure in the intermediate control chamber 119.

[0073] This design allows for the easy replacement of a defective punch at any time, or, depending on the component being sintered, the complete replacement of all punches. This simply requires removing the punches and the punch base plate 14 with the recesses 141 from the chamber and replacing them with other punches that have a punch base plate with matching recesses.

[0074] Should the piston 117 become jammed despite the thermal separation and be unable to retract solely due to the negative pressure in the pressure supply line 115, pressure can be exerted on the underside of the piston by increasing the pressure in the intermediate control chamber 119, thereby releasing the jam and allowing the piston 117 to return to its starting position.

[0075] It should also be mentioned that, due to the different cross-sections of the piston 117 and the plunger with the pressure surface of the pressure body 11, a minimum ratio of the input pressure exerted by the piston 117 on the guide rod 113 and the shaft 111 to the output pressure of the plunger surface must be maintained. The input pressure is applied to a circular cross-section of the piston 117.

[0076] In a possible configuration of the piston with a square pressure surface, let the side length of the square be "a". The piston 117 has a circular cross-section with radius "a" in both cases. In this case, where the cross-section of the piston surface is square, the ratio of inlet to outlet area is smallest. That is, the pressure exerted on the component is maximized, as can be seen from the equation P=F / A This results in the following equation: "P" represents pressure, "F" represents force, and "A" represents cross-sectional area.

[0077] For a square with a side length "a", the ratio of pressure area to piston area is approximately 1.273. This corresponds to the ratio of the area of ​​a square with side length "a" to that of a circle inscribed in the square with diameter "a".

[0078] Therefore, it is necessary to pressurize piston 117 to a pressure higher than the pressure exerted on the starting materials. In the example above, the inlet pressure would need to be approximately 51 MPa to achieve the desired outlet pressure of 40 MPa.

[0079] In the case of a non-square, but for example rectangular, printing surface, the ratio is determined analogously. Required input pressures for different die areas can be provided, for example, in the form of a table, or for different output pressures in the form of a characteristic curve.

[0080] Details of subsection 3 will be explained in particular by reference to the Fig. 1, Fig. 8 and Fig. 9 described in more detail.

[0081] The lower part 3 of the chamber is equipped, in order from bottom to top, with a cooling plate 37, thermal insulation in the form of an insulating plate 35, a heating plate 33, and a product holder 31. The product holder 31 serves as a counter-mold and is used to support a substrate onto which components are to be sintered.

[0082] To improve the quality of the sintered product, it is necessary to apply heat to the raw materials as simultaneously as possible with the application of pressure by the die. For this purpose, a thermal break is provided between the heating plate 33 and the product holder 31 positioned above it, as shown in the Fig. 8 can be seen schematically.

[0083] To achieve thermal separation, preload elements 32 are provided between an underside of the product holder 31 and a bottom wall of the lower part 3. These preload elements 32 tension the product holder 31 upwards, spacing it away from the heating plate 33. The preload elements 32 can be in the form of springs, such as coil springs, as shown in the Fig. The schematic representation in section 8 is not limited to this.

[0084] For example, instead of the schematically indicated coil springs, other types of springs such as leaf springs, hydraulic or pneumatic pistons, or mechanical means such as racks are possible as preload elements.

[0085] Due to the preload elements 32, the product holder 31 is positioned at a distance from the heating plate 33, in which heat transfer is at most reduced because an air gap acts as an insulator between the product holder 31 and the heating plate 33. As soon as the pistons are actuated and begin to exert pressure on the raw materials and the product holder supporting them, the preload force of the preload elements 32 is overcome and the product holder 31 is brought into contact with the heating plate 33. In this state, direct heat transfer occurs from the heating plate 33 to the product holder 31 and then to the raw materials.

[0086] Thus, the raw materials are simultaneously exposed to pressure and heat until the pressure load is released by the piston 117 being reset. Simultaneously with the release of the pressure load, the preload force of the preload elements 32 removes the product holder 31 from the heating plate 33, preventing further heating of the product holder 31 and the raw materials by the still-hot heating plate 33.

[0087] It should be noted that the presentation of the Fig. Figure 8 shows only the components important for thermal separation, but the overall structure can be designed as shown in the Fig. Figure 1 shows that, for example, thermal insulation, cooling, etc., may be present between the heating plate 33 and the bottom wall of the lower part 3.

[0088] The Fig. Figure 9 schematically shows an alternative for the thermal separation of the product holder and the heating plate. According to this alternative, the heating plate is provided with numerous through-holes (air channels) oriented from its underside to its top surface, which are connected to an air supply channel 36 that runs through the bottom wall of the base 3 and the thermal insulation 35 of the heating plate 33. To thermally separate the product holder 31 from the heating plate 33, air or another suitable fluid is supplied through the air supply channel 36 until the piston 117 applies pressure to the plunger. After passing through the numerous air channels in the heating plate 33, this air forms an air cushion between the heating plate 33 and the product holder, providing not only thermal separation but also additional insulation against radiant heat.

[0089] By interrupting the air supply at the moment the piston 117 is actuated, the air cushion between the heating plate 33 and the product holder 31 is eliminated. The product holder 31 comes into contact with the heating plate and is thus immediately heated. This heat is simultaneously transferred to the starting materials, which are then under pressure from the piston.

[0090] To carry out the sintering process, the device is closed by bringing the upper part 1 and the lower part 3 together. This process is described in particular by the Fig. 1, Fig. 2, Fig. 3, Fig. 4 to Fig. 5 described.

[0091] The side walls of the upper part 1 have a recess 131 at their edge facing the lower part 3. Next to the recess 131 are corresponding projections 137a and 137b. The side walls of the lower part 3 have a corresponding projection 39, which is inserted into the recess 131 between the projections 137a and 137b when the edge of the upper part 1 is brought into contact with the edge of the lower part 3. Additionally, a seal is arranged outside the projection 39 of the lower part 3, which, when the chamber is closed, seals its interior fluid-tight against the external environment.

[0092] In each of the projections 137a, 137b, 39, holes 133a, 133b, and 391 are provided transversely to the opening and closing directions of the chamber, respectively. Their cross-sections overlap when the chamber is in its closed position. The holes 133a, 133b, and 391 are elongated. This means that the length l1 of the holes 133a, 133b in the upper part and the length l2 of the hole 391 in the lower part 3 exceed the width b of the holes 133a, 133b, and 391. The inner hole 133b is a blind hole.

[0093] The figures exaggerate the proportions of the holes. In reality, it is sufficient if the lengths l1 and l2 exceed the widths b of holes 133a, 133b and 391 by approximately 0.5 mm.

[0094] The holes can have a diameter of 5 to 40 mm, depending on their number. The same diameter range applies to the pin(s). Tolerances from H7 to 2 mm are possible. If the holes are chosen to be larger than the pins, an advantageous automatic centering is achieved via the upper contact point (i.e., where the pin contacts the wall of the hole), thus eliminating the need for high-precision fits.

[0095] Because of the proportions of holes 133a, 133b, and 391, a cylindrical pin 135, in its installed position, can easily be guided through all the holes due to the clearance created by the elongated hole shape. As soon as the piston 117 exerts a pressure load on the plunger and, via the plunger, on the lower part 3 of the chamber, a situation arises as described in Fig. 3a shown.

[0096] Due to the pressure load, a downward force F acts, causing the lower part 3 of the chamber to move downwards from its in-place position until further movement is prevented by the now-locking pin 135. This positive locking mechanism thus makes it possible to absorb the force acting on the lower part without the need for complex hydraulic tables, etc.

[0097] As from the Fig. As can be seen in Figure 2a, several series of holes 133a, 133b, and 391 are provided, across which the resulting force F is distributed. Thus, requirements regarding the material properties of the pins can be met. After the chamber is locked, the plunger is actuated, the pressure of which acts on the starting materials. Therefore, a predetermined pressure is exerted on the starting materials placed on the product holder 31, such as a substrate, a layer of silver paste as a bonding agent, and a chip as a component. According to the invention, a pressure of 40 to 50 MPa can be achieved.

[0098] Within the chamber, a temperature between 20 °C and 330 °C can be reached in the area between the product holder 31 and the stamp base plate 14. This makes it possible to complete a joining process in 70 to 120 seconds. A key advantage is that the heating plate is positioned so that the heat is transferred directly to the product holder 31.

[0099] The required pressure is generated by pressurizing pistons 117 in cylinders of the cylinder plate 19 with a gas under high pressure.

[0100] If necessary, an overpressure or underpressure can also be created in the chamber by introducing or removing gas, and / or a gas such as nitrogen can be supplied to promote the joining process, or a reaction gas can be added.

[0101] Holding this state for a predetermined time results in a sintering process, i.e., a bonding of the silver molecules with the component and the substrate.

[0102] As soon as the pressure on the piston ends, the lower part 3 can again come into contact with the upper part 1, as shown in the Fig. 3b is evident. In this state, the pin 135 can easily be removed again from the holes 133a, 133b and 391 and the chamber opened to remove the finished sintered components.

[0103] In the Fig. 4a and Fig. Figure 4b shows a variant in which additional seals 311 are provided inside and outside the projection 39. These seals 311 are able to protect the interior of the chamber not only in the installed state (see Figure 4b). Fig. 4b) but also in the pressure load state (see Fig. 4a) to seal fluid-tight.

[0104] All compressive forces generated during the sintering process are absorbed by the chamber itself due to the form-fit. Therefore, it is not necessary to implement further structural measures to absorb or dissipate high compressive forces.

[0105] An alternative design for the positive locking mechanism is schematically derived from the Fig. Figure 5 shows that, instead of the configuration described above, each side wall of the upper part 1 and the lower part 3 is provided with a flange-like projection 431, 433. The projections 431, 433 have a chamfer on their surfaces facing away from each other. To create the positive fit, a C-shaped clamp 435 is guided over the projections. The clamp 435 has a corresponding chamfer on the inner surfaces of its legs facing the chamfered surfaces of the projections, so that a surface contact between the inner surfaces of the clamp 435 and the chamfered surfaces of the projections 431, 433 is possible. In the case of the alternative described here, the compressive forces are absorbed by the C-shaped clamp 435, which can be easily removed again after the sintering process is complete due to the chamfered surfaces.

[0106] Instead of the cylindrical pin described above, the positive locking mechanism can also be achieved, for example, with tapered pins and correspondingly conical bores.

[0107] The process described above can be advantageously automated.

[0108] According to the current state of the art, the counterforces required for the pressing process must be applied using external structures. In this case, a mechanism that moves a support assembly upwards to hold the substrate provides the external force necessary to lock the substrate in position and generate the counterforce required for the process. However, this results in a machine structure that is heavy and very complex.

[0109] Due to the positive locking mechanism according to the invention, the present invention creates an internal counterforce mechanism. Therefore, an external force source is not required to provide the counterforce.

[0110] To prepare for the bonding process, the paste is printed onto the substrate and the components (chips) are arranged on the paste; that is, the substrate is populated with the chips on the paste. Afterwards, the printed and chip-populated substrate is placed into the chamber.

[0111] Since the tool is adjustable, the positions of the punch correspond to the positions of the chips on the substrate. A film can be advantageously placed over the chips, for example, using rollers mounted on the sides of the tool. The film can be renewed after each bonding process. This can be done by replacing the rollers with the film or by changing the position of the existing film. The latter can be achieved by advancing the film wound on a roller, thereby changing its position. PTFE or a similar plastic can be used as the film material, but this is not the only option.

[0112] The joining process takes place over a predetermined period at a predetermined temperature and pressure to effectively sinter the component onto the substrate. Advantageously, the component and / or other starting materials such as the substrate and silver paste can be preheated or cooled by a preheating or cooling device before and after the joining process.

Claims

[1] Device for connecting a component to a substrate, with a chamber divisible into at least two parts, wherein a stamp (11, 111) is provided on a first part (1), and a counter-stamp (31) is provided on a second part (3), wherein the first part (1) has a wall with an edge which can be brought into contact with an opposite edge of a wall of the second part (3) in order to close the chamber, wherein the counter-stamp (31) can be loaded with starting materials in an open state of the chamber, and in a closed state of the chamber, pressure can be exerted on the starting materials provided between the stamp (11, 111) and the counter-stamp (31) via the stamp (11), wherein In the closed state, the first part (1) and the second part (3) can be locked together by means of a positive locking mechanism, so that opening of the chamber by separation of the first part (1) from the second part (3) is prevented, characterized by , that Each edge has a recess (131) and / or a projection (137; 39) with a hole (133a, 133b; 391) which can be brought into contact with a projection (39; 137) and / or a recess (131) of the opposite edge, wherein a cross-section of the hole (133a, 133b) of the projection (137a, 137b) of the wall of the first part (1) in a brought-in state at least partially overlaps with a cross-section of the hole (391) of the projection (39) of the wall of the second part (3), and the positive locking can be achieved by means of a pin (135) guided through both holes (133a, 133b; 391). [2] Device according to claim 1, wherein at least one of the holes (133a, 133b; 391) has a cross-section with a greater length (l1; l2) than width (b), wherein the length (l1, l2) of the cross-section extends in an opening direction of the chamber. [3] Device according to claim 2, wherein in the installed state the central axis of the hole (133a, 133b) of the projection (137a, 137b) of the wall of the first part (1) differs from the central axis of the hole (391) of the projection (39) of the wall of the second part (3). [4] Device according to one of claims 1 to 3, wherein, in the closed state of the chamber during the exertion of pressure by the plunger (11) on the counter-plunger (31) via the starting materials, the pin (135) is clamped between an inner wall section of the hole (391) in the projection (39) of the second part (3) directed towards the first part (1) and an inner wall section of the hole (133a, 133b) in the projection (137a, 137b) of the first part directed towards the second part (3), whereas the pin (135) is freely movable in a pressure-free state and can be inserted into and removed from the holes (133a, 133b; 391). [5] Device according to one of claims 1 to 4, wherein at least the edge of the first part (1) or the edge of the second part (3) has a seal (311) which is able to create a gas-tight state of the chamber in a closed state, irrespective of any pressure exerted by the plunger (11) on the counter-plunger (31) via the starting materials. [6] Device for connecting a component to a substrate, with a chamber divisible into at least two parts, wherein a stamp (11, 111) is provided on a first part (1), and a counter-stamp (31) is provided on a second part (3), wherein the first part (1) has a wall with an edge which can be brought into contact with an opposite edge of a wall of the second part (3) in order to close the chamber, wherein the counter-stamp (31) can be loaded with starting materials in an open state of the chamber, and In a closed state of the chamber, pressure can be exerted on the starting materials provided between the punch (11, 111) and the counter-punch (31) via the punch (11), wherein in the closed state the first part (1) and the second part (3) can be locked by means of a positive locking mechanism, so that opening of the chamber by separation of the first part (1) from the second part (3) is prevented, characterized by , that the first part (1) has a flange-like first projection (431) at the edge directed towards an exterior of the chamber, and the second part (3) has a flange-like second projection (433) at the edge directed towards an exterior of the chamber, wherein The positive connection can be achieved by bringing a surface of the first projection (431) directed towards the second projection (433) into contact with a surface of the second projection (433) directed towards the first projection (431) and attaching a clamp (435) over both flange-like projections (431, 433). [7] Device according to claim 6, wherein a surface of the first projection (431) pointing away from the second projection (433) and / or a surface of the second projection (433) pointing away from the first projection (431) is / are chamfered. [8] Device according to claim 7, wherein each inner surface of the clamp (435) which is to be brought into contact with a chamfered surface of the first and / or the second projection (431; 433) has a corresponding chamfer. [9] Device according to claim 6, 7, or 8, wherein the clamp (435) is rotatably connected at one of its ends to the wall of the first part (1) or the wall of the second part (3), and the positive locking can be established and released by rotating the clamp about the connection point.

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