Flux transfer to a carrier substrate

Abstract

A method for transferring flux to a carrier substrate (1) is described. In this method, a flux (FM) is applied to a mobile carrier (2) such that the flux (FM) adheres to the mobile carrier (2). The flux (FM) is applied to the underside of the mobile carrier (2). Furthermore, the carrier substrate (1) is positioned below the mobile carrier (2) with electrical contacts (3) facing upwards towards the underside of the mobile carrier (2). Subsequently, the carrier substrate (1) is contacted with the mobile carrier (2). During this contact, the flux (FM) is transferred from the mobile carrier (2) to the electrical contacts (3) of the carrier substrate (1). A method for manufacturing an electronic circuit board is also described. A flux transfer device (30) is also described.

Description

[0001] The invention relates to a method for transferring flux onto a carrier substrate. Furthermore, the invention relates to a method for manufacturing an electronic circuit board. The invention also relates to a flux transfer device.

[0002] The assembly of so-called sensor boards for counting X-ray detector systems presents challenges for assembly and interconnection technology. The sequence of individual connection steps for bonding a so-called hybrid consisting of one or more ASICs and the CT sensor material, which usually comprises cadmium telluride or cadmium zinc telluride, to a substrate comprising either an HTCC ceramic or an LTCC ceramic (HTCC stands for "High Temperature Cofired Ceramics", LTCC stands for "Low Temperature Cofired Ceramics"), requires specific process control and handling procedures.

[0003] While the ASIC can be mounted onto the sensor material using a typical flip-chip process, allowing the ASIC's solder balls to be dipped into a flux and then assembled onto the designated pads of the sensor material, the question arises as to how the so-called hybrid (i.e., an arrangement of the ASIC(s) plus the sensor material) can be applied to the substrate in the subsequent step if later tiling of the sensor boards is required and the substrate must therefore not be larger than a multiple of the assembled number of hybrids.

[0004] Since the resulting hybrids lack an external ball structure, they cannot be fluxed using a dipping process (here, "fluxing" means wetting with flux) and subsequently mounted on pads of a substrate. The contact balls or solder balls for contacting the substrate and the hybrids are typically arranged on the substrate itself. Such a substrate with contact balls is described in Fig. Figure 1 shows that the carrier substrate has the necessary contacts on its upper surface to receive signals from the hybrid structure and to supply the hybrid structure with electrical energy. Furthermore, such a carrier substrate has one or more connectors on its underside, also for signal transmission and power supply.

[0005] Due to the aforementioned tiling, the solder balls extend to the edges of the carrier substrate, making simple handling of these components impossible.

[0006] A conventional process of flux transfer to the contact balls of a carrier substrate is in Fig. Figure 2 illustrates this. In the process mentioned, additional measures and devices must be used to rotate the carrier substrate by 180° before flux transfer, thus placing it in a pose suitable for flux transfer. A carrier device for flux transfer for such a conventional method is described in DE 20 2020 101 726 U1.

[0007] The object of the invention is to simplify the design and assembly of an electronic structure with a via or other vertical electrical connection and a support substrate, and in particular the manufacture of a sensor board for a counting X-ray detector.

[0008] This problem is solved by a method for transferring flux to a carrier substrate according to claim 1, a method for manufacturing an electronic circuit board according to claim 13 and a flux transfer device according to claim 14.

[0009] In the inventive method for transferring flux to a carrier substrate, a flux is transferred to a mobile carrier in such a way that the flux adheres to the mobile carrier, with the flux being applied to the underside of the mobile carrier. According to the invention, the flux is therefore not transferred directly from a flux bath to an upside-down carrier substrate, as is conventionally done, but rather a mobile carrier is used as an intermediary for this transfer process. As will be explained in detail later, the use of this intermediary has the advantage that the carrier substrate does not have to be held upside down during the flux transfer process, since the mobile carrier essentially mirrors or spatially inverts the arrangement of the flux.

[0010] A substrate is defined as a substrate on which electronic components, preferably electronic circuits, particularly semiconductor circuits, and especially hybrids of ASICs and semiconductor sensors, are arranged. The substrate thus functions as a circuit carrier. It is connected to the electronic components, particularly the electronic circuits, by electrical contacts. These electrical contacts preferably comprise contact elements protruding from the substrate, more preferably vias or contact balls. A connector located on the opposite side, the underside of the substrate or the ceramic substrate, to which ribbon cables for signal and power transmission can be attached, is to be distinguished from these electrical contacts.

[0011] The support substrate preferably comprises an HTCC ceramic and / or an LTCC ceramic or FR4 (a flame-retardant composite material made of epoxy resin and fiberglass fabric). However, the support substrate can also comprise other materials, particularly electrically insulating materials, to support electronic structures.

[0012] A mobile carrier is understood to be a device onto which flux can be applied and with which the flux can be transported to and transferred onto a semiconductor substrate. As will be explained in detail later, flexible belts, preferably roller belts, and in particular belt-like films, are particularly suitable for this purpose. These films allow the flux to be applied and can be set in motion, preferably by rollers, like conveyor belts, to transport the flux applied to the films, especially roller belts, to a position where the flux can be transferred to the carrier substrate or to the electrical contacts arranged on the carrier substrate.

[0013] The carrier substrate is positioned and aligned below the mobile carrier with the electrical contacts, preferably contact balls, facing upwards towards the downward-facing surface of the mobile carrier, on which the flux to be transferred is located (i.e., the underside of the mobile carrier). The terms "above" and "below," or "facing upwards" and "facing downwards," are to be used in the sense that an object is accelerated or pulled by gravity from "above" to "below," i.e., towards the center of the Earth's gravitational field.If the carrier substrate is oriented "upwards" with its electrical contacts, a holding device for the carrier substrate can be arranged on the opposite side of the carrier substrate, i.e., the underside. Unlike the conventional arrangement of the carrier substrate in "upside-down" flux transfer, this holding device does not need to be suctioned to the carrier substrate by a vacuum. The arrangement of the carrier substrate with the electrical contacts facing upwards is possible because the mobile carrier, when the flux is applied to its underside, already inverts the orientation of the flux. The flux is no longer in a flux reservoir, but rather "hangs" or "sticks" to the underside of the mobile carrier.

[0014] The carrier substrate is then contacted by a vertical relative movement between the two. This movement can occur either vertically, from bottom to top, towards the carrier substrate, or vertically downwards towards the carrier substrate until contact is achieved. Vertical movement of both the carrier and the carrier substrate towards each other is also possible. If the carrier, in order to transport the flux to the carrier substrate, moves perpendicular to the described vertical movement between the carrier and the carrier substrate, this transverse movement is stopped before the carrier and the carrier substrate make contact.To transfer the flux to the electrical contacts, preferably the contact balls, a vertical movement occurs between the mobile carrier and the carrier substrate until they touch and the electrical contacts are immersed in the flux on the mobile carrier, with the flux adhering to the electrical contacts. Subsequently, the carrier substrate and the mobile carrier are moved apart again. Optionally, a transverse transport movement of the mobile carrier is then resumed.

[0015] Optionally, the carrier substrate and the mobile carrier can be moved past each other during contact in such a way that the flux is transferred to the contact balls by wiping. This "passing" is achieved by moving the mobile carrier horizontally relative to the carrier substrate, thus effecting a wiping action.

[0016] The transfer process is advantageously simplified compared to the conventional method, since the carrier substrate no longer needs to be rotated 180° by a complex device using a vacuum, and the flux transfer no longer needs to take place with the carrier substrate in an "upside-down" position. Instead, this inversion of orientation is handled by the mobile carrier, and instead of the orientation of the carrier substrate, the orientation of the flux is inverted when the mobile carrier picks up the flux from a flux reservoir. As already indicated, the inventive method is particularly advantageous when fixing the carrier substrate in a holding device is difficult, for example, due to the complete covering of the carrier substrate with electrical contacts.Such a full coverage is necessary for the arranging of sensor units, especially when using sensor units for an X-ray detector, so that image data can be generated without artifacts between individual pixels or sensor areas.

[0017] In the flux transfer method according to the invention, the viscosity and adhesion properties of a flux are utilized. That is, the flux can be approached "upside down" to the carrier substrate and then transferred to the semiconducting substrate or the contact balls of the carrier substrate by a wiping process.

[0018] The flux transfer method according to the invention can also be used to apply flux to larger areas, such as substrates of flat panel detectors. It is irrelevant whether solder balls or contact spheres, in particular SAC solders (SAC stands for "SnAgCu") or low-melting-point solder systems made of SnIn (a tin-indium compound), or other contacting structures, such as so-called copper pillars, are used as contact elements.

[0019] The flux transfer method according to the invention can be used for various electronic applications, such as in medical technology, the automotive sector, or industrial electronics, regardless of the subsequent use of the carrier substrate. However, its application in the manufacture of counting X-ray detectors for X-ray imaging, particularly CT imaging, is especially preferred.

[0020] In the inventive method for manufacturing an electronic circuit board, an electronic structure with a plurality of switching elements is formed.

[0021] In the method according to the invention, a carrier substrate is formed with a plurality of electrical contacts on one of its surfaces.

[0022] Furthermore, a flux is applied to the contacts of the carrier substrate by applying the flux transfer method according to the invention to a carrier substrate.

[0023] Finally, the electronic structure and the substrate are joined, preferably by a soldering process. Advantageously, the manufacturing process is also simplified by the streamlined method for transferring flux to the substrate.

[0024] The flux transfer device according to the invention comprises an application unit for applying a flux to a mobile carrier such that the flux adheres to the mobile carrier, with the flux being applied to the underside of the mobile carrier. The flux transfer device according to the invention also includes a positioning unit for arranging the carrier substrate below the mobile carrier, with electrical contacts, preferably contact balls, which are directed upwards towards the side of the mobile carrier facing the ground, i.e., the underside of the mobile carrier.The flux transfer device according to the invention also comprises a transfer unit for transferring the flux from the mobile carrier to the electrical contacts of the carrier substrate by means of a vertical relative movement of the carrier substrate and the mobile carrier towards each other, such that the carrier substrate contacts the mobile carrier and the flux is transferred from the mobile carrier to the electrical contacts. The flux transfer device according to the invention shares the advantages of the flux transfer method according to the invention.

[0025] According to the invention, a control device for controlling a flux transfer device according to the invention can also be provided, with which control processes for implementing the steps of the method according to the invention for flux transfer onto a carrier substrate or the method according to the invention for manufacturing an electronic circuit board can be carried out.

[0026] The computer program product according to the invention comprises program code sections with which control operations are carried out to implement the steps of the method according to the invention for transferring flux onto a carrier substrate or the method according to the invention for manufacturing an electronic circuit board, when the program is executed by a control device of the flux transfer device according to the invention or a device for manufacturing electronic circuit boards.

[0027] A largely software-based implementation has the advantage that existing components of a flux transfer device or a device for manufacturing electronic circuit boards, which includes the flux transfer device, can be easily retrofitted by a software update to operate in the manner according to the invention, provided the hardware is modified accordingly.

[0028] Some of the aforementioned components of the flux transfer device according to the invention can be implemented wholly or partially as software modules in a processor of a corresponding computer system, e.g., by a control unit of the flux transfer device according to the invention or by a controller of a device for manufacturing electronic circuit boards that includes such a flux transfer device. A largely software-based implementation has the advantage that even previously used computer systems for production control of electronic circuit boards can be easily retrofitted by means of a software update to operate in the manner of the invention.Therefore, the problem is also solved by a corresponding computer program product with a computer program that can be directly loaded into a computer system, containing program sections to execute control processes for implementing the steps of the inventive method for transferring flux onto a carrier substrate or the inventive method for manufacturing electronic circuit boards. In addition to the computer program, such a computer program product may optionally include additional components such as documentation and / or additional components, including hardware components such as hardware keys (dongles, etc.) for using the software.

[0029] For transport to the computer system or control unit and / or for storage on or in the computer system or control unit, a computer-readable medium, such as a memory stick, a hard drive, or other portable or permanently installed data carrier, can be used, on which the program sections of the computer program that can be read and executed by a computer system are stored. The computer system may, for example, have one or more cooperating microprocessors or similar components for this purpose.

[0030] The dependent claims and the subsequent description each contain particularly advantageous embodiments and further developments of the invention. In particular, the claims of one claim category may also be further developed analogously to the dependent claims of another claim category. Furthermore, within the scope of the invention, the various features of different embodiments and claims may also be combined to form new embodiments.

[0031] In a preferred embodiment of the inventive method for flux transfer to a carrier substrate, before the flux is transferred from the mobile carrier to the carrier substrate, or during the step of contacting the carrier substrate with the mobile carrier, the carrier substrate is fed onto the mobile carrier from below and pressed against the mobile carrier. Advantageously, the carrier substrate does not need to be rotated 180° to come into contact with the flux on the mobile carrier and therefore does not need to be held in place by additional measures or devices, such as a vacuum unit. In this embodiment, the carrier substrate to be fluxed is lifted and pressed into the flux film. Lifting can be performed mechanically or hydraulically.

[0032] Preferably, or alternatively, before the step of transferring the flux from the mobile carrier to the substrate, or during the step of contacting the substrate with the mobile carrier, the mobile carrier is fed onto the substrate from above and pressed against it. In this variant, the substrate itself can remain in an unchanged position, while the mobile carrier moves towards the substrate. For example, the substrate can remain in a manufacturing fixture during a production process, so that the manufacturing process does not have to be interrupted for flux application.

[0033] It is also preferred that, for the transfer of the flux from the mobile carrier to the substrate, a sufficient stripping force for the transfer of the flux from the mobile carrier to the substrate is achieved by generating counter-pressure on the side of the mobile carrier facing away from the substrate using a plate. Applying such counter-pressure allows the use of a mobile flexible carrier, in particular a film, since the flexible carrier can be pressed against the substrate by the plate, or provides counter-pressure in the event that the substrate is pressed against the mobile carrier. The plate can be static, or it can be specifically positioned to support the transfer only for the flux transfer itself. Advantageously, the transfer of the flux between the carrier and the substrate can be facilitated and made more reliable.

[0034] As already indicated, the mobile carrier preferably comprises a film, in particular a carrier film, with adhesive properties for the flux. Advantageously, the film, especially the carrier film, can be made flexible and moved along a predetermined trajectory to facilitate the transport and transfer of the flux. Due to its adhesive properties, the flux can also adhere to the mobile carrier "upside down" and be transferred to a substrate in this position.

[0035] Preferably, the mobile carrier includes a roller conveyor and is immersed in a flux reservoir when the flux is applied to the mobile carrier, particularly the roller conveyor. A roller conveyor is defined as a belt that is moved forward by rollers, such that material on the roller conveyor is transported from one location to another. One type of such a roller conveyor is a conveyor belt that is moved cyclically by rollers and transports material, in this case flux, from one position to another. Advantageously, the mobile carrier can be continuously supplied with new flux, allowing a large number of flux transfer operations to be carried out in a short time.

[0036] If the mobile carrier is designed as a conveyor belt, the conveyor belt is preferably guided over a plurality of deflection rollers. Advantageously, the mobile carrier can be guided over several stations, in particular the flux reservoir and the transfer unit, whereby several process steps can take place in parallel.

[0037] Preferably, at least one of the deflection rollers is arranged on the side of the conveyor belt where the flux is applied, i.e., the "underside," and has a recess over which a portion of the conveyor belt coated with flux is guided. Advantageously, the recess prevents unwanted smearing of the flux on the deflection roller. Thus, when such "outer" rollers or deflection rollers are used, the underside of the conveyor belt is only partially coated with flux, preferably in the center. "Partially" in this context means that the conveyor belt is not coated with flux across its entire width, but only partially coated in the transverse direction. It is preferred that the flux is applied centrally to the conveyor belt and that the outer deflection rollers come into contact with the conveyor belt on both outer sides or with the outer surface of the conveyor belt to guide or drive the conveyor belt.However, other variants are also conceivable, in which the contact area between the outer deflection roller and the roller belt is arranged centrally or is formed on one side and the roller belt is supplied with flux in a correspondingly complementary manner.

[0038] To achieve a uniform layer of flux with a constant thickness on the mobile carrier during application, a predetermined thickness of the flux layer is determined by a wiping device positioned at a predetermined distance from the mobile carrier, where the predetermined distance defines the predetermined thickness. Advantageously, a uniform layer of defined thickness is applied to the mobile carrier. Furthermore, achieving a defined layer thickness on the mobile carrier advantageously defines the quantity of flux transferred during the transfer process between the mobile carrier and the substrate.

[0039] If excess flux is wiped off the mobile carrier by the wiping device, the wiped-off flux is preferably returned to the flux reservoir. The return of the flux to the reservoir preferably occurs by gravity, with the wiped-off flux falling back into the reservoir after the wiping process. For this purpose, the wiping device is preferably arranged above the flux reservoir or within the flux area, so that the wiped-off flux can preferably be reabsorbed from the flux reservoir without additional return units. Alternatively, the wiped-off flux is also collected by a receiving unit and / or fed to the flux reservoir by a return unit, for example by means of negative or positive pressure.Advantageously, by returning the stripped flux to the flux reservoir, the flux consumption of the inventive method for transferring flux to a carrier substrate is reduced or optimized compared to a variant without such return.

[0040] The flux, which typically or preferably consists primarily of rosin, exhibits low fluidity and has a honey-like consistency. By guiding and immersing the carrier, preferably a film, at the surface of the flux pool, the flux adheres to the underside of the carrier. This property of the flux is specifically utilized for its absorption by the film.

[0041] Preferably, a cutting edge is used as the wiping device, the tip of which is positioned at a predetermined distance from the mobile carrier. The distance between the tip and the mobile carrier is used to define the thickness of the flux layer on the mobile carrier. The flux film, which initially forms and is irregular in height, is thus adjusted to a uniform thickness by the cutting edge at the outlet from a flux reservoir. The excess and removed flux is recovered and remains in the flux reservoir.

[0042] Preferably, the flux is kept in the flux reservoir under an inert atmosphere, preferably nitrogen, to minimize the reactivity and drying out of the flux in the flux reservoir.

[0043] If the mobile carrier has a roller conveyor, the conveyor is preferably immersed in a flux reservoir at a first position in a closed cycle, and the flux applied to the conveyor is then transferred to the carrier substrate at a second position. The second position is spatially separated from the first. Advantageously, several processes, in particular the application of the flux to the conveyor and the transfer of the flux to the carrier substrate, can be carried out in parallel, since the processes take place at different positions.

[0044] If the conveyor belt is sufficiently long, multiple transfer operations can preferably be performed per cycle. Here, a cycle is defined as one complete rotation of the conveyor belt. In particular, several sections of the conveyor belt can be treated with flux per cycle, and the flux can be transferred from these sections to one or more carrier substrates. If the flux is transferred from the multiple sections to the same carrier substrate, this transfer typically occurs sequentially. However, parallel transfer of flux to multiple carrier substrates simultaneously is also possible. Advantageously, the transfer of flux to the carrier substrate or multiple carrier substrates can be accelerated by applying flux multiple times per cycle.

[0045] The invention is explained in more detail below with reference to the accompanying figures and exemplary embodiments. The figures show: Fig. 1 a sectional view of a support substrate, Fig. 2 a schematic representation of a conventional method for transferring flux to a carrier substrate, Fig. 3 a schematic sectional view of a flux transfer device according to an embodiment of the invention, Fig. 4 a schematic sectional view of an application unit of a flux transfer device according to an embodiment of the invention, Fig. 5 a comparative view of two different variants of the contacting between a carrier substrate and a flux transfer device according to an embodiment of the invention, Fig. 6 an illustration of a multiple flux transfer according to an alternative embodiment of the invention, Fig. 7 a comparative representation of a fully supporting deflection pulley and a partially supporting deflection pulley, Fig. 8 a flowchart illustrating a method for transferring flux to a carrier substrate according to an embodiment of the invention, Fig. 9 a flowchart illustrating a method for manufacturing an electronic circuit board according to an embodiment of the invention.

[0046] In Fig. Figure 1 shows a cross-sectional view of a conventional carrier substrate 1. The carrier substrate 1 has a plurality of contact points, also referred to as contact balls 3, which are in Fig. Figure 1 shows the top of a substrate ceramic 1a of the carrier substrate 1. The carrier substrate 1 also has a connector 5 on its underside, i.e., the side facing away from the contact balls 3.

[0047] In Fig. Figure 2 is a schematic representation of a conventional method for transferring flux to a carrier substrate 1. The in Fig. The carrier substrate 1 shown has a plurality of solder balls 3 on its upper side and a connector 5 on its underside opposite the upper side.

[0048] In the first illustration on the far left in Fig. 2 is already in Fig. Figure 1 shows the carrier substrate 1 in an arrangement in which the carrier substrate 1 is positioned in a carrier device 4, which is also referred to as an inlay. The carrier device 4 encloses the carrier substrate 1 on the underside as in a frame and holds it in a horizontal position, so that the substrate ceramic of the carrier substrate 1 does not rest on the connector 5. The carrier device 4 has a plurality of feet 6, which are shown in the left in Fig. 2. The first illustration shows the downward direction.

[0049] In a second representation to the right of the first representation in Fig. Figure 2 shows a mechanical device 8 into which the support substrate 1, including the support device 4, is inserted. The support substrate 1 is held from below by a vacuum unit 7. The mechanical device 8 has a frame consisting of a bottom and top. The vacuum unit 7 has a metal receptacle with vacuum channels and vacuum openings with rubber seals. The support substrate 1 is held and secured by the vacuum unit 7 between the connector 5 and the feet. The support substrate 1 can be rotated while the vacuum is maintained.

[0050] A third illustration to the right of the second shows how the carrier substrate 1 is rotated by 180° and immersed from above into a flux bed 9 with a cavity for flux FM, whereby the contact balls 3 are wetted with the flux FM. The carrier substrate 1 is held in the carrier device 4 by the vacuum unit 7.

[0051] In a fourth illustration to the right of the third, the solder balls 3 of the carrier substrate 1 with adhering flux FM are shown after flux transfer by immersion of the carrier substrate 1 into the flux bed 9. That is, the carrier substrate 1 has already been removed from the flux bed 9. Furthermore, the flux bed 9, from which flux FM was transferred to the solder balls 3, is also shown in the lower part of the fourth illustration.

[0052] Subsequently, the carrier substrate 1 is rotated again by 180° using the vacuum unit 7 and shown in a fifth representation in Fig. 2, which is shown to the right of the fourth illustration, shows the carrier substrate 1 in the carrier device 4 wetted with flux on the solder balls 3.

[0053] In Fig. Figure 3 illustrates a schematic sectional view of a flux transfer device 30 according to an embodiment of the invention.

[0054] The flux transfer device 30 according to the invention has an application unit 31. In the Fig. In the illustrated embodiment 3, the application unit 31 is designed with a flux reservoir 31a through which a carrier film 2 is guided. The carrier film 2 is guided in a circuit by a plurality of deflection rollers 33, 33a. The inner deflection rollers 33 guide the carrier film 2 across its entire surface, while the outer deflection rollers 33a have recesses that prevent contact between the flux FM applied to the outside of the carrier film 2 and the outer deflection rollers 33a. These recesses are in Fig. 7 illustrates. In Fig. Figure 3 shows a plate 32a on the lower right side to support the wiping process of the flux FM on a carrier substrate 1. A thick arrow indicates the direction of movement of the carrier film 2, in this embodiment counterclockwise. Furthermore, in Fig. Figure 3, represented by two upward-pointing parallel arrows, symbolizes the function of a transfer unit 34 of the flux transfer device 30. The transfer unit 34 is designed to transfer the flux FM to the electrical contacts of the semiconductor substrate by establishing a mechanical contact between the electrical contacts (not shown) of a semiconductor substrate (not shown) and the flux FM on the carrier film 2.

[0055] In Fig. Figure 4 shows a schematic sectional view of an application unit 31 of a flux transfer device 30 according to an embodiment of the invention. The Fig. The application unit 31 shown in Figure 4 has a cutting edge 31b, which is shown in the right-hand part of the image. This cutting edge wipes off the flux FM contained in a flux reservoir 31a as it transitions onto the carrier film 2, thus defining the thickness of the flux film on the carrier film 2. As already mentioned, the flux FM, which generally consists primarily of rosin (a resin system), has low flowability and a honey-like consistency. By guiding and immersing the carrier film 2 at the surface of the flux level in the flux reservoir 31a, the flux FM adheres to the underside of the carrier film 2.

[0056] In Fig. Figure 5 illustrates a comparative view of two different variants of the contacting between a carrier substrate 1 and the flux transfer device 30 according to an embodiment of the invention. The contacting is carried out by step 8.III, which is described in Fig. As illustrated in Figure 8, this is implemented. In the left half of the image, the carrier substrate 1 is first positioned under the carrier film in a region of the flux transfer device 30 by a positioning unit 32. Subsequently, the carrier substrate 1 is pressed against the flux transfer device 30 from below by a transfer unit 34 during the flux transfer, which is symbolized by an upward-pointing arrow. In the variant shown in the right half of the image, the flux transfer device 30 is pressed onto the carrier substrate 1 from above by the transfer unit 34, which is symbolized by a downward-pointing arrow.

[0057] In Fig. Figure 6 illustrates a multiple flux transfer according to an alternative embodiment of the invention. From the illustration in Fig. Figure 6 shows how the flux film loses or becomes depleted of flux at the positions on the carrier film 2 after the individual transfer processes. The figure also shows that the flux film is continuously rebuilt by guiding the carrier film 2 through the flux reservoir 31a and that the depleted flux film areas on the carrier film 2 are replenished.

[0058] In step 6.I (shown top left), the flux transfer is initiated, and the carrier substrate 1, to be coated with flux FM, is brought from below towards the flux transfer device 30. In step 6.II (shown top right), the flux FM is first wiped from a carrier film 2 of the flux transfer device 30 onto the contact balls 3 of the carrier substrate 1. In a third step 6.III (bottom left), the carrier substrate 1 is lowered, whereby the contact balls 3 of the carrier substrate 1 are now coated with flux FM, and the carrier film 2 of the flux transfer device 30 is at least partially freed of flux FM in the transfer area 30a of the flux transfer device 30, which in Fig. Figure 6 illustrates this with a jagged pattern. In the fourth step, 6.IV (bottom right), the transfer process of the flux FM to a carrier substrate 1 has already occurred four times. This is evident from the jagged patterns visible at four points on the carrier film 2 of the flux transfer device 30, indicating that flux FM has been wiped onto the contact balls 3 of a carrier substrate 1 at these points. Advantageously, a multiple transfer processes can therefore occur with one rotation of the carrier film 2, depending on the length of the band or roll formed by the carrier film 2.

[0059] In Fig. Figure 7 shows a comparative representation of a deflection roller 33 that fully contacts a carrier film 2 and a deflection roller 33a that partially contacts a carrier film 2. Fig. 7 therefore serves to better understand the function and the different construction of the different types 33, 33a of deflection pulleys.

[0060] On the left side of the Fig. Figure 7 shows a deflection roller 33 that makes full contact with a carrier film 2. This type of internal deflection roller is designed to support the carrier film 2 or the circulating belt of the flux transfer device 30 formed by the carrier film 2 from the inside, or to deflect this circulating belt. It is thus clearly evident that the full-surface deflection roller 33 is only used on the side of the carrier film 2 that is not wetted with flux FM.

[0061] On the right side of the Fig. Figure 7 shows a deflection roller 33a that partially contacts a carrier film 2. The flux FM is applied to a central region 2a of the carrier film 2 facing the deflection roller 33a, while it is not applied to the edge region 2b of the carrier film 2. The edge region 2b of the carrier film 2 contacts the deflection roller 33a, which moves the carrier film 2 by rotation. The central region 2a of the deflection roller 33a is radially reduced or slightly recessed compared to the edge region 2b of the deflection roller 33a in order to prevent contact of the flux FM with the deflection roller 33a in this central region 2a.

[0062] In Fig. Figure 8 shows a flowchart 800 illustrating a method for transferring flux to a carrier substrate 1 according to an embodiment of the invention.

[0063] In step 8.I, a flux FM is applied to a carrier film 2 such that the flux FM adheres to the carrier film 2. For this purpose, the carrier film 2 is passed through a flux reservoir 31a, whereby the flux FM adheres to the underside of the carrier film 2.

[0064] In step 8.II, the carrier substrate 1 is positioned below the carrier film 2 with contact balls 3 pointing upwards.

[0065] In step 8.III, the carrier substrate 1 is brought into contact with the carrier film 2 by vertically approaching the carrier substrate 1 to the carrier film 2. This transfers the flux FM adhering to the contact balls 3 of the carrier substrate 1.

[0066] In step 8.IV, the carrier substrate 1 is separated from the carrier film 2 again by a vertical movement.

[0067] In Fig. Figure 9 shows a flowchart 900 illustrating a method for manufacturing a module of an X-ray detector according to an embodiment of the invention.

[0068] In step 9.I, a direct-converting semiconductor sensor (DKS) is first formed.

[0069] Subsequently, in step 9.II, an electronic circuit structure ASIC is generated, and in step 9.III, the electronic circuit structure ASIC is electrically connected to the semiconductor sensor DKS by solder balls 3, thus creating a hybrid structure H. In step 9.IV, a carrier substrate 1 with a plurality of solder balls 3 is generated.

[0070] In step 9.V, flux FM is transferred to the contact balls 3 of the carrier substrate 1 by applying the flux transfer method according to the invention to a carrier substrate 1, as described in Fig. Figure 8 illustrates this.

[0071] Finally, in step 9.VI, the hybrid structure H and the support substrate 1 are joined together by soldering the contact balls 3 of the support substrate 1 to the hybrid structure H.

[0072] Finally, it should be noted once again that the detailed methods and devices described above are exemplary embodiments and that the basic principle can be varied in many ways by those skilled in the art without departing from the scope of the invention, insofar as it is defined by the claims. For the sake of completeness, it should also be noted that the use of the indefinite articles "a" or "an" does not preclude the possibility that the features in question may be present multiple times. Likewise, the term "unit" does not preclude the possibility that it consists of several components, which may also be spatially distributed. Regardless of the grammatical gender of a particular term, persons of male, female, or other gender identities are included. QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] DE 20 2020 101 726 U1

[0006]

Claims

[1] Method for flux transfer to a carrier substrate (1), comprising the steps: - applying a flux (FM) to a mobile support (2) such that the flux (FM) adheres to the mobile support (2), wherein the flux (FM) is applied to an underside of the mobile support (2), - arranging the carrier substrate (1), which has a plurality of electrical contacts (3) on one of its two substrate surfaces, below the mobile carrier (2) with the electrical contacts (3) facing upwards towards the downwardly facing underside of the mobile carrier (2), - contacting the carrier substrate (1) with the mobile carrier (2) by a vertical relative movement between the carrier substrate (1) and the mobile carrier (2), - Transferring the flux (FM) to the electrical contacts (3) of the carrier substrate (1). [2] The method according to claim 1, wherein in the step of contacting the carrier substrate (1) with the mobile carrier (2), the carrier substrate (1) is fed from below onto the mobile carrier (2) and is pressed against the mobile carrier (2). [3] Method according to claim 1 or 2, wherein in the step of contacting the carrier substrate (1) with the mobile carrier (2), the mobile carrier (2) is fed from above onto the carrier substrate (1) and is pressed against the carrier substrate (1). [4] Method according to one of the preceding claims, wherein in the step of transferring the flux (FM) to the electrical contacts (3) of the carrier substrate (1), a sufficient stripping force for the transfer of the flux (FM) from the mobile carrier (2) to the carrier substrate (1) is achieved by generating a counterpressure on the side of the mobile carrier (2) facing away from the carrier substrate (1) by a plate. [5] Method according to one of the preceding claims, wherein the mobile carrier (2) comprises a film with an adhesive property for the flux (FM). [6] Method according to one of the preceding claims, wherein the mobile carrier (2) comprises a roller belt and, when applying the flux (FM) to the mobile carrier (2), the roller belt is immersed in a flux reservoir (31a). [7] Method according to claim 6, wherein the roller belt is guided over a plurality of deflection rollers (33, 33a). [8] Method according to claim 7, wherein at least one of the deflection rollers (33a) is arranged on the side of the roller belt on which the flux (FM) is applied and has a recess (2a) over which a partial surface of the roller belt, which is acted upon by the flux (FM), is guided. [9] Method according to one of the preceding claims, wherein a predetermined thickness of a layer of the flux (FM) applied to the mobile carrier (2) is determined by a stripping device (31b) which is arranged at a predetermined distance from the mobile carrier (2), the predetermined distance defining the predetermined thickness of the layer of the flux (FM) applied to the mobile carrier (2). [10] Method according to one of claims 6 to 8 and according to claim 9, wherein flux (FM) applied to the mobile carrier (2) is stripped off by the stripping device (31b) and the stripped flux (FM) is returned to the flux reservoir (31a). [11] Method according to claim 9 or 10, wherein a cutting edge is used as the stripping device (31b). [12] Method according to one of claims 5 to 11, wherein the mobile carrier (2) comprises a roller belt and the roller belt is immersed in a flux reservoir (31a) in a closed cycle and the flux (FM) thus applied to the roller belt is transferred to the carrier substrate (1). [13] A method for manufacturing an electronic circuit board, comprising the steps of: - forming an electronic structure with a plurality of switching elements, - forming a carrier substrate (1) with a plurality of electrical contacts (3) on one of its surfaces, - Transferring flux (FM) to the contacts (3) of the carrier substrate (1) by applying the method according to one of claims 1 to 12, - Assembling the electronic structure and the carrier substrate (1). [14] Flux transfer device (30), comprising: - an application unit (31) for applying a flux (FM) to a mobile support (2) such that the flux (FM) adheres to the mobile support (2), wherein the flux (FM) is applied to an underside of the mobile support (2), - a positioning unit (32) for arranging the carrier substrate (1) below the mobile carrier (2) with electrical contacts (3) directed upwards towards the underside of the mobile carrier (2), - a transfer unit (34) for relatively vertically moving the carrier substrate (1) and the mobile carrier (2) towards each other such that the carrier substrate (1) contacts the mobile carrier (2) and the flux (FM) is transferred from the mobile carrier (2) to the electrical contacts (3). [15] Computer program product comprising a computer program which is directly loadable into a control device of a flux transfer device (30), with program code sections to carry out all steps for controlling the steps of a method according to one of claims 1 to 13 when the program is executed in the control device. [16] Computer-readable medium on which program sections executable by a computer unit are stored in order to carry out steps for controlling the steps of a method according to one of claims 1 to 13 when the program sections are executed by the computer unit.

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