METHOD FOR MANUFACTURING MULTILAYER PRINTED CIRCUIT BOARDS

Description

[0001] The invention relates to a method for producing multilayer printed circuit boards according to the preamble of patent claim 1.

[0002] Multilayer printed circuit boards are now typically manufactured in a multi-level heating press. During experimental testing of the manufacturing process, suitable process parameters for operating the multi-level heating system are determined, and subsequent series production is carried out using the process parameters determined experimentally. To determine the necessary parameters for experimental testing, copper-based functional layers and insulation layers are alternately layered on top of one another in the tool during the assembly process step. A temperature sensor is positioned between two of these layers as a measuring transducer, and a signal line is routed out of the tool. The temperature sensor is a lost sensor that cannot be reused.

[0003] A free end of the signal line is typically temporarily secured to the outside of the tool, for example, using an adhesive strip. The loaded tool is then inserted into a stack heating press with a plurality of other tools in the loading process step. The lower tool section rests on a heating plate of the stack heating press and is aligned or positioned relative to it. The heating plate serves as a support for the tool. The upper tool section is spaced from another heating plate arranged above it, which—with the exception of the top heating plate—supports another loaded tool.

[0004] In order to determine measured values ​​and process parameters during experimental testing, the free ends of the signal lines are detached from the respective tool and connected to a data storage box located with the heating plates and tools in a thermocompression chamber of the multi-story heating press. The thermocompression chamber is then closed, and in a subsequent manufacturing step, the heating plates are moved toward each other so that the tools are sandwiched between two heating plates, heating the loaded tools, and bonding the functional and insulating layers in the tool under pressure. During this process, the temperature inside the tool is measured using the temperature sensor.

[0005] The process parameters are determined offline during experimental testing. During experimental testing, the data is simply recorded and stored in the data storage box. The data is processed and evaluated downstream. The measured values ​​obtained during experimental testing are therefore not intended to be used to control or regulate the ongoing production process step. Furthermore, the effort required to manually wire the individual temperature sensors in the hot multi-daylight heating press is complex and time-consuming due to the limited space and the temperatures typically prevailing there, which reach 100°C or more. This involves a risk of burns for the machine operator.

[0006] In exceptional cases, the procedure described above for experimental testing is also applied in the context of serial production of printed circuit boards. However, due to the considerable time and associated high costs involved, this effort is only undertaken in exceptional cases, for example, when the printed circuit boards to be manufactured are used in safety-critical applications and the user therefore has special requirements for monitoring and documenting production. However, even in this case, the measured values ​​cannot be used for online intervention in the ongoing production process step.

[0007] IT 2019 0000 1739 A1 discloses a manufacturing process for multilayer printed circuit boards.

[0008] From DE 10 2016 113 985 A1 a multi-level heating press is known which is suitable for use in the production of multi-layer printed circuit boards.

[0009] The object of the present invention is to provide an improved method for producing multilayer printed circuit boards.

[0010] To achieve this object, the invention has the features of patent claim 1.

[0011] The particular advantage of the invention is that the online recording and processing of the measured values ​​does not interfere with the ongoing

[0012] This makes it possible to monitor and adjust the manufacturing process step with respect to relevant process parameters, such as the temperature in the thermocompression chamber or in the tool and / or the pressure applied to the tool. This makes it possible to optimize the process and, if necessary, complete it earlier than planned. As a result, the process time or cycle time is reduced, and throughput can be increased. The higher throughput then directly leads to a reduction in costs or an increase in production quantities.

[0013] Furthermore, improved monitoring of the ongoing manufacturing process step allows for the installation of quality monitoring, which allows defects in the manufacturing process to be identified before the manufactured printed circuit boards are shipped and reach the market. This can improve product quality. Furthermore, the costs for troubleshooting or the return of defective devices are reduced. Particularly in safety-critical applications, increased requirements for production documentation can be met and the risk of failure reduced.

[0014] Insofar as the present invention refers to a production control device and / or the control of the ongoing production process step, this equally includes control and regulation devices or control and regulation interventions.

[0015] According to the invention, the measured values ​​themselves obtained with the aid of the sensor and / or the data obtained therefrom can be transmitted and used to monitor or control the ongoing manufacturing process step. The term "data obtained from the measured values" includes, in particular but not exclusively, data obtained by smoothing, compressing, aggregating, and / or mathematical processing of the measured values ​​of the sensor.

[0016] According to a preferred embodiment of the invention, the measured values ​​determined using the sensor and / or the data obtained therefrom are transmitted in a hybrid manner, i.e., in some cases wirelessly and in some cases via cable or wired transmission. Advantageously, the hybrid transmission of the measured values ​​and / or the data obtained therefrom makes it possible to equally satisfy the harsh boundary conditions of production and the logistical challenges in the manufacturing process. For example, the measured values ​​and / or the data obtained therefrom can be transmitted wirelessly from a transmitter assigned to the tool to a receiving unit that interacts with the transmitter and is installed stationary in the thermocompression chamber or outside it as part of a multi-stage heating press or other suitable production system.By inserting the tool into the thermocompression chamber, the currently common cabling for the sensor is eliminated. This reduces assembly time and the risk of the machine operator getting burned while wiring the sensors. At the same time, the measured values ​​obtained inside the tool can be transmitted to the transmitter via cable or wire. Given the temperature in the thermocompression chamber and the pressure acting on the tool, this is both robust and error-free. Furthermore, the use of radio sensors and the wireless data transmission of the measured values ​​from the tool would be very expensive due to the fact that the sensors cannot be reused as lost sensors. In contrast, if, for example, a thermocouple wire forms both the sensor and a signal line leading from the sensor to the transmitter, the implementation is extremely cost-effective.

[0017] According to a further development of the invention, the receiving unit that interacts with the transmitter is arranged in the thermocompression chamber itself, and the measured values ​​or the data obtained therefrom are transmitted via cable or line from the thermocompression chamber to the production control device provided outside the thermocompression chamber. This advantageously ensures that the transmitter and the receiving unit are arranged in close proximity to one another. Wireless data transmission can thus be extremely interference-free and energy-efficient. For example, the transmitter itself can be supplied with power wirelessly. The further data transmission from the receiving unit to the production control device, in turn, is cable-based or line-based and designed to be robust in accordance with the production conditions.

[0018] According to an alternative embodiment of the invention, the receiving unit can be provided outside the thermocompression chamber. Advantageously, the receiving unit outside the thermocompression chamber is subjected to less thermal stress, which allows the use of particularly cost-effective receiving units.

[0019] According to a further development of the invention, the transmitter is fluidically cooled in the thermocompression chamber. A cooling fluid is supplied or discharged via at least one fluid line. The cooling fluid can be, for example, air and preferably ambient air. The thermal load on the transmitter is advantageously reduced by the fluidic cooling. This counteracts damage to the transmitter.

[0020] According to a further development of the invention, a temperature, a pressure, or a humidity value are determined as measured values. These measured values ​​advantageously provide the basis for making statements about the quality or functionality of the printed circuit board. At the same time, these measured values ​​can be used to intervene online in the ongoing production process step. In particular, the possibility of influencing the ongoing production process step online can make it possible to reduce process or cycle times to a minimum without adversely affecting the quality or functionality of the printed circuit boards. The pressure and / or temperature in the thermocompression chamber are maintained and adjusted such that the functional and insulating layers bond together reliably in the desired manner.

[0021] According to a further development of the invention, a target temperature to which the thermocompression chamber is to be heated during the ongoing manufacturing process step and / or a target pressure to which the tool is subjected in the thermocompression chamber during the ongoing manufacturing process step can be increased beyond a specified value for the target temperature or the target pressure during the ongoing manufacturing process step, or can be set differently in the sense of a readjustment, depending on the measured values ​​and / or the data obtained therefrom. In an analogous manner, it can be provided that a temperature-time profile and / or a pressure-time profile to be run during the ongoing manufacturing process step is adapted or changed depending on the measured values ​​and / or the data obtained therefrom.

[0022] Further advantages, features and details of the invention can be gathered from the further subclaims and the following description.

[0023] The drawings are merely exemplary to clarify the invention and are not limiting in nature to the invention defined by the claims.

[0024] They show: Fig. 1 a perspective partial view of an apparatus according to the invention for producing multi-layer printed circuit boards with a populated multi-part tool, a tool logic module and a measured value transmission module, wherein a lower part of the tool is placed on a heating plate and a receiving unit of the measured value transmission module is held on the heating plate, Fig. 2 an enlarged view of a detail X of the arrangement according to Fig. 1 , Fig. 3 a side view of the arrangement according to Fig. 1 , Fig. 4 a top view of the arrangement according to Fig. 1 , Fig. 5 an exploded view of the arrangement according to Fig. 1, wherein the equipped multi-part tool with the tool logic module mounted thereon is arranged at a distance from the heating plate, and Fig. 6 is a schematic diagram of the device according to the invention as part of a multi-story heating press with a production control device.

[0025] A device according to the invention for producing multilayer printed circuit boards comprises a multi-part tool with a lower tool part 2 and an upper tool part 1, a measured value sensor, and a tool logic module 7, to which measured values ​​acquired by the measured value sensor are fed via a signal line. The device further comprises a measured value transmission module 12 with a receiving unit 9 and a transmitting unit 10, as well as a data line 14 for further transmitting the measured values ​​or data obtained therefrom. The receiving unit 9 and the transmitting unit 10 of the measured value transmission module 12 are arranged spatially separated from one another and, in this case, are connected to one another for data purposes via a line 11.

[0026] When the device according to the invention is used as intended, the tool with the upper tool part 1 and the lower tool part 2, the tool logic module 7, the measured value transmitter, and the receiving unit 9 of the measured value transmission module 12 are arranged together with a plurality of heating plates 3 in a thermocompression chamber 20 of a multi-story heating press. The transmission unit 10 of the measured value transmission module 12 and a production control device 13 of the multi-story heating press, connected to the transmission unit 10 via the data line 14, are provided outside the thermocompression chamber 20. The production control device 13, the thermocompression chamber 20, and the heating plates 3 are not part of the device according to the invention. However, they belong to the multi-story heating press together with the device according to the invention.

[0027] In the production of multilayer printed circuit boards, functional layers 5 and insulation layers 4 of the printed circuit board to be produced are first arranged alternately in the tool in a preparatory assembly process step outside the thermocompression chamber 20 of the multi-level heating press and layered between the upper tool part 1 and the lower tool part 2. During the layering process, in the present embodiment of the invention, a total of six thermocouple wires 6, which simultaneously form the sensor and the signal line of the device according to the invention, are arranged between the layers 4, 5. The thermocouple wires 6 are preferably arranged between different layers 4, 5 such that the thermocouple wires 6 lie outside the printed circuit board of the layered structure to be produced later by cutting.

[0028] The thermocouple wires 6 are routed from the layered structure to the tool logic module 7, where they are contacted. The tool logic module 7, which includes a housing 8, a transmitter, and other functional components for receiving and / or storing and / or post-processing the measured values, is attached to the lower part 2 of the tool. The internal structure of the tool logic module 7 is implemented such that the measured values ​​supplied via the signal line reach the transmitter.

[0029] In preparation for the production of the multilayer printed circuit boards, a plurality of tools are preconfigured or pre-assembled in the manner described above and transported, preferably automatically, to the multi-level heating press in a single assembly process step using suitable handling means. The majority of the tools are then inserted into the thermocompression chamber 20 of the multi-level heating press such that each tool is placed with the underside of its lower tool part 2 from above onto a heating plate 3 and positioned relative to the latter. The number of heating plates 3 in the thermocompression chamber 20 is preferably selected such that a heating plate 3 is provided below each lower tool part 2 and that an additional heating plate 3 is provided above the upper tool part 1 of an uppermost tool in the thermocompression chamber 20.

[0030] When inserting the tools into the thermocompression chamber 20 of the multi-story heating press, the tool logic module 7 with the transmitter is positioned adjacent to the receiving unit 9 of the measured value transmission module 12, which is also installed in the thermocompression chamber 20. A distance between the transmitter of the tool logic module 7 and the receiving unit 9 of the measured value transmission module 12 is selected such that wireless transmission of the measured values ​​or the data obtained therefrom from the transmitter of the tool logic module 7 to the receiving unit 9 is possible.

[0031] In this example, the wireless transmission is carried out using a near-field communication routine. The transmitter of the tool logic module 7 then comprises, for example, an NFC coil (NFC: Near Field Communication), and the receiver unit 9 of the measured value transmission module 12 is designed as an NFC reader or provides one. The NFC coil and the NFC reader interact in such a way that the measured values ​​or the data obtained from them are transmitted or forwarded wirelessly.

[0032] For example, a power supply for the tool logic module (7) is realized within the framework of NFC communication via the measured value transmission module (12).

[0033] In order to simultaneously ensure the positioning of the tools on the heating plates 3 of the transmitter of each tool relative to the receiving unit 9 of the measured value transmission module 12 assigned to the respective tool, a support body 19 is provided on each heating plate 3, to which the receiving unit 9 is fixed. In the present embodiment of the invention, the support body 19 is formed, for example, by a double L- or Z-shaped profile body.

[0034] In order to bond the functional and insulating layers 4, 5 arranged in the tool, the thermocompression chamber 20 is heated to approximately 180°C. At the same time, the heating plates 3 are moved together, thus pressing the layers 4, 5 against each other in the tools. After a certain holding time, which varies particularly depending on the temperature, pressure, and material of the functional and insulating layers 4, 5 used, the layers 4, 5 are then firmly bonded to each other, with adjacent functional layers 5 each separated and insulated from each other by an insulating layer 4. The thermocouple wires 6 are firmly bonded to the layer structure. As lost sensors, they cannot be reused.

[0035] To protect the functional components of the tool logic module 7, and in particular the transmitter, from excessive temperatures, the present embodiment of the invention provides fluid cooling for the tool logic module 7. The fluid cooling system provides two fluid lines 16, 17 through which a cooling fluid is supplied and discharged. Furthermore, an inlet opening 21 and an outlet opening 22 for the cooling fluid are provided on the housing 8 of the tool logic module 7.

[0036] Elastic connecting sleeves 18, which are attached to the support body 19 on a side facing the tool logic module, serve to connect the inlet and outlet openings 21, 22 on the one hand to the fluid lines 16, 17 on the other. The connecting sleeves 18 are connected to the fluid lines 16, 17.

[0037] Furthermore, the connecting sleeves 18 are positioned on the support body 19 such that they are placed against the inlet and outlet openings 21, 22 when the tool is inserted into the thermocompression chamber 20. The connecting sleeves 18 can deform elastically. As a result of this deformation, a contact force is provided, which leads to a sufficiently tight connection and minimal leakage.

[0038] The cooling fluid reaches the inlet opening 21 of the housing 8 via a first fluid line 16 and a first connection sleeve 18 and flows out via the outlet opening 22, a second connection sleeve 18, and a second fluid line 17. The housing 8 itself serves as a fluid channel and connects the inlet and outlet openings 21, 22.

[0039] In this way, cooling of the functional components of the tool logic module 7 installed in the housing 8 is realized.

[0040] For example, ambient air supplied from outside the thermocompression chamber can be used as the cooling fluid.

[0041] The use of the device according to the invention as part of a multi-level heating press can improve the production of multilayer printed circuit boards. The measured values ​​determined using the thermocouple wire and / or the data obtained therefrom can be fed online to the production control device (13) of the multi-level heating press, i.e., directly during the ongoing production process step. Based on the measured values ​​and / or the data obtained therefrom, the production control device (13) can decide whether intervention in the ongoing production process step is necessary and, for example, extend or shorten the holding time or adjust the temperature or pressure.The production control device can therefore be designed, in particular, to compare the measured values ​​and / or the data obtained therefrom with stored and / or calculated default values, in particular with default values ​​for the duration of the ongoing production process step, for a target temperature to which the thermocompression chamber (20) is heated, or for a target pressure to which the tool in the thermocompression chamber (20) is subjected. In this way, deviations from the target and actual process can be detected early, and measures to prevent or correct errors can be initiated in a timely manner. Furthermore, the measured values ​​and / or the data obtained therefrom can be stored for documentation purposes.

[0042] Identical components and component functions are identified by the same reference symbols.

Claims

1. A method for manufacturing multi-layer circuit boards, - wherein, within the scope of a production method step, a tool upper part (1) and a tool lower part (2) of a multi-part tool with multiple functional layers (5) and at least one insulation layer (4) of a circuit board to be produced and at least one measurement value sensor provided therebetween are pressed against one another and heated in a thermo-compression chamber (20) and in doing so measured values are captured with the measurement value sensor, - wherein the measured values and / or data obtained therefrom are transmitted to a production control device (13) during the ongoing production method step and that the measured values and / or the data obtained therefrom are processed by the production control device (13) for monitoring the ongoing production method step and / or for controlling the ongoing production method step with respect to a default value for a measurand of the measurement value sensor, characterized in that - before the production method step, first, within the scope of an assembling method step, the multiple functional layers (5) and the at least one insulation layer (4) are arranged in a layered manner between the tool lower part (2) and the tool upper part (1), and the at least one measurement value sensor is positioned between the tool upper part (1) and the tool lower part (2) such that the measurement value sensor rests against at least one functional layer (5) and / or insulation layer (4), and - that before the production method step, then, within the scope of an equipping method step, a plurality of preassembled tools with the multiple functional layers (5) and the at least one insulation layer (4) and the measurement value sensor are transported via suitable handling means to a multi-platen heat press and inserted into the thermo-compression chamber (20) of the multi-platen heat press such that each tool is placed with an underside of its tool lower part (2) from above onto a heating plate (3) and positioned relative thereto.

2. The method according to claim 1, characterized in that the measured values are transmitted in any case partially wirelessly to the production control device (13).

3. The method according to claim 2, characterized in that the measured values are transmitted in a hybrid manner, i.e. in any case partially wirelessly and partially in a wire-bound or line-bound manner.

4. The method according to any of claims 1 to 3, characterized in, that the measured values are guided out of the tool in a wire-bound or line-bound manner.

5. The method according to any of claims 1 to 4, characterized in that the measured values are guided out of the thermo-compression chamber (20) in a wire-bound or line-bound manner to the production control device (13) provided outside the thermo-compression chamber (20).

6. The method according to any of claims 2 to 5, characterized in that the measured values are transmitted wirelessly from a transmitter arranged in the thermo-compression chamber (20) to a receiving unit (9) cooperating with the transmitter.

7. The method according to claim 6, characterized in that the transmitter is fluidically cooled in the thermo-compression chamber (20), wherein a cooling fluid is supplied and / or discharged via at least one fluid line (16, 17).

8. The method according to any of claims 1 to 7, characterized in that when inserting the tool into the thermo-compression chamber (20) the transmitter together with the tool or as part thereof is positioned and / or aligned relative to the receiving unit (9).

9. The method according to any of claims 1 to 8, characterized in that a temperature and / or a pressure and / or a humidity value are determined as a measured value.

10. The method according to any of claims 1 to 9, characterized in that when processing the measured values and / or the data obtained therefrom by the production control device (13) the measured values and / or the data obtained therefrom are compared with stored reference values, wherein preferably the default values as reference values for the measurand of the measurement value sensor are used as a basis for the comparison.

11. The method according to any of claims 1 to 10, characterized in that a duration of the ongoing production method step is determined depending on the measured values and / or the data obtained therefrom, and / or that the ongoing production method step is continued beyond a default value for the duration of the ongoing production method step or is terminated before reaching the default value for the duration of the ongoing production method step.

12. The method according to any of claims 1 to 11, characterized in that a target temperature to which the thermo-compression chamber (20) is heated is increased in the ongoing production method step, depending on the measured values and / or the data obtained therefrom, beyond a default value for the target temperature and / or is set deviating from the default value for the target temperature.

13. The method according to any of claims 1 to 12, characterized in that a target pressure the tool in the thermo-compression chamber (20) is subjected to is increased in the ongoing production method step, depending on the measured values and / or the data obtained therefrom, beyond a default value for the target pressure and / or is set deviating from the default value for the target pressure.