Method and apparatus for cooling a printed circuit board after an oven-supported soldering process

Abstract

The invention relates to a method (1) for cooling a printed circuit board (10) after an oven-assisted soldering process, wherein the temperature of the printed circuit board (10) after the soldering process is greater than a predetermined target temperature of the printed circuit board (10), comprising feeding the printed circuit board (10) to a lower pressing tool (3) of a pressing device (2), arranging the printed circuit board (10) in the lower pressing tool (3), closing the pressing device (2) by bringing together an upper pressing tool (4) of the pressing device (2) and the lower pressing tool (3), whereby punches (5) of the pressing tools (3, 4) contact the printed circuit board (10) at predetermined positions, applying a force to the printed circuit board (10) by means of the punches (5), cooling the printed circuit board (10) to the predetermined target temperature during the force application, so that the printed circuit board (10) solidifies in a predetermined shape, and ending the force application.Furthermore, the invention relates to a device for cooling a printed circuit board (10) after an oven-supported soldering process.

Description

[0001] The invention relates to a method and a device for cooling a printed circuit board after an oven-assisted soldering process.

[0002] Printed circuit boards (PCBs) are frequently used in electronic circuits to mechanically and / or electrically connect electronic components. These are often printed circuit boards (PCBs), which are usually made of plastic. A soldering process is typically used to assemble the PCBs. This process introduces heat into the PCB, resulting in a temperature increase. The temperature of the soldering process is usually higher than the softening point of the PCB material, especially if the PCB is made of plastic. As it cools, the PCB can therefore deform thermally. This thermal deformation and the resulting dimensional deviations of the assembled PCB (printed circuit board assembly, PCBA) can lead to problems in subsequent process steps.

[0003] US 2020 / 0101549A1 describes a method for creating a solder joint between multiple components in a process chamber sealed from its environment by heating and melting solder material placed between the components to be joined. The components to be joined are first temporarily connected with a bonding material to form a solder group in which the components are fixed relative to each other in a bonded position.

[0004] DE 26 40 613 A1 describes a method for contacting a flexible carrier having conductor tracks with which a circuit component arranged on it is connected to conductor tracks of a layered circuit arranged on a ceramic carrier, wherein one side of the flexible carrier has soldered conductor tracks and solder bumps.

[0005] DE 10 2014 217 927 A1 describes a method for solderless electrical press-fit contacting of electrically conductive press-fit pins in printed circuit boards (PCBs) comprising the following steps: Providing a PCB with at least one contact opening extending substantially perpendicularly through the PCB for press-fit contacting. Providing at least one press-fit component with at least one electrically conductive press-fit pin. Providing a sonotrode for exerting a force and for applying ultrasonic energy. In order to electrically and mechanically contact press-fit pins that are fixedly arranged in a carrier with a PCB using ultrasonic press-fit technology, it is provided that the at least one press-fit component with its at least one press-fit pin is fixed, in particular held in a stationary position, during a press-fit step.Furthermore, it is provided that in the press-fit pin the circuit board is directly acted upon with a force and with ultrasonic energy by means of the sonotrode in such a way that the circuit board is pressed onto the at least one press-fit pin of the at least one press-fit component at the location of its at least one contact opening.

[0006] The invention is based on the objective of providing a solution to the aforementioned problem.

[0007] The problem is solved according to the invention by a method with the features of claim 1 and a device with the features of claim 7. Advantageous embodiments of the invention are set forth in the dependent claims.

[0008] In particular, a method for cooling a printed circuit board after an oven-assisted soldering process is provided, wherein the temperature of the printed circuit board after the soldering process is greater than a predetermined target temperature of the printed circuit board, comprising: feeding the printed circuit board to a lower pressing tool of a pressing device, arranging the printed circuit board in the lower pressing tool, closing the pressing device by bringing together an upper pressing tool of the pressing device and the lower pressing tool, whereby punches of the pressing tools contact the printed circuit board at predetermined positions, applying a force to the printed circuit board by means of the punches, cooling the printed circuit board to the predetermined target temperature during the force application so that the printed circuit board solidifies in a predetermined shape, and ending the force application.

[0009] Furthermore, in particular, a device for cooling a printed circuit board after an oven-assisted soldering process is provided, wherein the temperature of the printed circuit board after the soldering process is greater than a predetermined target temperature of the printed circuit board, comprising a pressing device which is configured to cool the printed circuit board to the predetermined target temperature, wherein the pressing device comprises an upper pressing tool and a lower pressing tool, wherein the lower pressing tool is configured to hold the printed circuit board, wherein the pressing tools each comprise punches which are configured to apply a force to the printed circuit board at predetermined positions, wherein the pressing device is configured to perform a movement of the pressing tools relative to each other;and a control device designed to control the movement of the press tools relative to each other and designed to terminate the application of force after the predetermined target temperature has been reached.

[0010] The process and apparatus enable the solidification of a printed circuit board (PCB) into a predetermined shape. For this purpose, the PCB is fed into a press after an oven-assisted soldering process. The PCB's temperature is higher than a predetermined target temperature. The PCB is positioned in the lower press tool of the press. The press is then closed by bringing the upper and lower press tools together. This brings the press tool's plungers into contact with the PCB. A force is applied to the PCB by means of the plungers. During this force application, the PCB cools to the predetermined target temperature. This causes the PCB to solidify into a predetermined shape while the force is applied. Once the predetermined target temperature is reached, the force is released.

[0011] The basic idea here is to cool the printed circuit board (PCB) to the specified target temperature while its shape and position are fixed by the force exerted by the dies of the pressing device. This allows the PCB to solidify in the specified shape. The shape is determined primarily by the positions and / or designs of the dies. This method reduces and / or prevents thermal distortion during cooling. It also reduces and / or prevents unwanted dimensional deviations of the PCB. This, in turn, lowers the probability of defects in subsequent process steps. In particular, a downstream press-fit process has stringent requirements regarding permissible dimensional deviations, especially PCB warping, which this method and device can meet.

[0012] It is intended that the printed circuit board (PCB) is populated using a press-fit process after cooling to the specified target temperature. The press-fit device used for this process is identical or structurally equivalent to the press used in the cooling process, at least with respect to the positions of at least some of the press tool punches. Specifically, electronic components are arranged in a lower press tool of the press-fit device during the press-fit process, such that the positions of the press-fit pins of the electronic components correspond to the positions of holes in the PCB. In particular, a force is applied to the PCB by the punches of an upper press tool of the press-fit device, guiding the press-fit pins into the holes.In particular, thermal deformation during the cooling of the printed circuit board (PCB) is reduced and / or prevented primarily at the positions of the dies. Due to identical or identical die positions in the subsequent press-fit process, the dies can make contact with the PCB, especially at those points that exhibit no or minimal dimensional deviation. This can significantly reduce the risk of faulty component placement during the press-fit process, particularly by minimizing dimensional deviations in the areas of the press-fit holes.

[0013] A printed circuit board (PCB) is, in particular, a circuit board and / or a printed circuit. Specifically, the PCB comprises an electrically insulating material, especially a plastic or a fiber-reinforced plastic. Electronic components are mechanically and / or electrically connected through the PCB. In particular, the connection between the electronic components and the PCB is formed by means of an oven-assisted soldering process.

[0014] In the oven-assisted soldering process, the printed circuit board (PCB) is coated with solder and heated to a temperature higher than the solder's melting point. Specifically, the oven-assisted soldering temperature is higher than the specified target temperature of the PCB. Furthermore, the oven-assisted soldering temperature is higher than the heat deflection temperature, Vicat softening temperature, and / or glass transition temperature of a PCB material. For example, when using lead-based solder, the oven-assisted soldering temperature is specified as 230–250 °C. When using lead-free solder, a temperature of 245 °C is specified.

[0015] The specified target temperature is, in particular, the temperature to which the printed circuit board (PCB) is to be cooled. Specifically, the specified target temperature is a temperature at which further processing of the PCB is possible without deformation or damage. In particular, the specified target temperature is chosen such that it meets the temperature requirements of a downstream process step. Specifically, the specified target temperature is lower than the heat deflection temperature, the Vicat softening temperature, and / or the glass transition temperature of a PCB material. For example, a target temperature of 100 °C is specified if the PCB comprises a material with a glass transition temperature of 120 °C (for example, a flame-retardant composite material of class FR4).It can be arranged that the printed circuit board (PCB) remains between the aligning pressing tools of the pressing device for a predetermined time to cool, reaching the target temperature within this time. This eliminates the need to measure the PCB temperature and thus the need for a temperature sensor. The predetermined time can be determined, for example, through empirical testing. Alternatively, the PCB temperature can be measured using a temperature sensor and compared to the predetermined target temperature. This allows for the detection and / or verification of whether the target temperature has been reached.

[0016] A pressing device is, in particular, a setting machine, a press-fit machine, and / or a press, especially a hydraulic press, a pneumatic press, a mechanical press, or a servo press. The pressing device comprises a lower pressing tool and an upper pressing tool. Furthermore, the pressing device is configured to perform a movement of the pressing tools relative to each other.

[0017] The lower pressing tool is designed to hold the printed circuit board (PCB). Furthermore, the pressing tools include punches designed to apply force to the PCB at predetermined positions. The punches are, in particular, cylindrical and / or prism-shaped. The pressing tools and / or the punches are, in particular, at least partially made of metal. The positions of the punches are, in particular, individually predetermined for the PCB and depend on the positions of electronic components on the PCB.

[0018] In one embodiment, the printed circuit board (PCB) is actively cooled during the application of force in the pressing device. This reduces the time required to reach the specified target temperature, thereby shortening the cycle time of the process. Specifically, the PCB is cooled using a cooling gas, such as compressed air, nitrogen, and / or argon. In one embodiment of the device, at least one channel is provided within the pressing device to supply a cooling gas to the PCB. Specifically, the channel is designed to branch within the pressing device, supplying the cooling gas to the PCB at multiple points. The channel can be configured, for example, as bores and / or milled recesses in at least one of the pressing tools and / or in a cover plate.

[0019] In one embodiment, the printed circuit board (PCB) is removed from the press after cooling to the specified target temperature and cools down to a predetermined final temperature outside the press and / or during a subsequent process step. This reduces cycle time, as the PCB only needs to remain in the press to cool to the specified target temperature. This, in turn, reduces the overall process duration. The predetermined final temperature is, in particular, lower than the specified target temperature. The predetermined final temperature is, in particular, a temperature dictated by the requirements of subsequent handling and / or further processing. For example, if the PCB is to be handled by a person, a predetermined final temperature of 30–50 °C may be specified.In a further embodiment, cooling to the predetermined final temperature takes place during a printed circuit board test. In particular, the printed circuit board is checked for production defects and / or proper functionality by means of the printed circuit board test.

[0020] In a further embodiment, the pressing device executes a predetermined displacement-time profile, from which the applied force results. If a displacement-time profile (and not a constant force) is specified, according to which the pressing device performs a movement, the force applied by the punches can adjust itself, particularly through thermal deformation of the printed circuit board. Specifically, the punches are arranged at the positions where they contact the printed circuit board until the predetermined target temperature is reached. If thermal stresses occur in the printed circuit board during the cooling process, the punches counteract the thermal deformation of the printed circuit board. In this case, the force applied by the punches is precisely large enough to compensate for any thermal deformation of the printed circuit board at the punch positions.The applied force is therefore precisely as great as necessary to prevent deformation or to reverse deformation that has already occurred. This significantly reduces the risk of the circuit board being damaged by excessive force from the stamps.

[0021] In one embodiment of the device, at least one temperature sensor is provided, which is configured to detect the temperature of the printed circuit board. In particular, this allows the device to detect and / or verify when the target temperature has been reached. Furthermore, the cycle time of the process can be shortened, in particular, by ending the force application precisely when a temperature of the printed circuit board is detected that is less than or equal to the target temperature.

[0022] Further features regarding the design of the device are derived from the description of embodiments of the method. The advantages of the device are the same in each case as in the embodiments of the method.

[0023] Furthermore, a process arrangement is also provided, comprising a soldering oven for oven-assisted soldering of the printed circuit board and a device for cooling the printed circuit board according to one of the embodiments described in this disclosure.

[0024] The invention is explained in more detail below with reference to preferred embodiments and the figures. These show: Fig. 1 a schematic flowchart of an embodiment of the method; Fig. 2 a schematic flowchart of an embodiment of the method; Fig. 3 a schematic representation of an embodiment of the device; Fig. 4 a schematic representation of an embodiment of the device.

[0025] The Fig. Figure 1 shows a schematic flowchart of an embodiment of the method for cooling a printed circuit board (PCB) after an oven-assisted soldering process. Due to a preceding process step 100, in which the PCB was processed using an oven-assisted soldering process, the PCB temperature is higher than a predetermined target temperature. In process step 101, the PCB is fed to a lower pressing tool of a pressing device. In process step 102, the PCB is positioned in the lower pressing tool. In process step 103a, the pressing device is closed by bringing together an upper pressing tool and the lower pressing tool, causing the punches of the pressing tools to contact the PCB at predetermined positions.In process step 104a, a force is applied to the circuit board using the stamps, and the circuit board is cooled to the specified target temperature during the force application, so that the circuit board solidifies in a predetermined shape. In process step 105, the force application is terminated.

[0026] The Fig. Figure 2 shows a schematic flowchart of an embodiment of the method for cooling a printed circuit board after an oven-assisted soldering process. The embodiment is fundamentally the same as that described in the Fig. The embodiment shown is designed as shown in Figure 1. The process steps are fundamentally the same. In the illustrated embodiment, the pressing device is designed to execute a predetermined path-time profile in process step 103b, from which the applied force results.

[0027] Furthermore, in the illustrated embodiment, it is particularly provided that the printed circuit board is actively cooled to the predetermined target temperature in process step 104b, while a force is applied to the printed circuit board by means of the plungers. In particular, it is provided that the printed circuit board is cooled by means of a cooling gas, for example compressed air, nitrogen and / or argon.

[0028] In process step 106, the printed circuit board is removed from the press after cooling to the specified target temperature. In process step 107, the printed circuit board is cooled to a specified final temperature while a subsequent process step is carried out.

[0029] In particular, it is planned that a printed circuit board test will be carried out in process step 107 during the cooling of the printed circuit board.

[0030] In process step 108, the printed circuit board can be assembled in a press-fit process after cooling to the specified target temperature, wherein a press device used for the press-fit process is identical or structurally identical to the press device used in the cooling process, at least with regard to the positions of at least one part of the punches of the press tools.

[0031] The Fig. Figure 3 shows a schematic representation of an embodiment of the device 1 for cooling a printed circuit board 10 after an oven-assisted soldering process. After the oven-assisted soldering process, the temperature of the printed circuit board 10 is higher than the predetermined target temperature. The device 1 comprises a press 2, which is configured to cool the printed circuit board 10 to the predetermined target temperature. The press 2 comprises an upper press tool 4 and a lower press tool 3. The lower press tool 3 is configured to hold the printed circuit board 10. The press tools 3 and 4 each comprise a punch 5. The punches 5 are configured to apply a force to the printed circuit board 10 at predetermined positions. The press 2 is configured to move the press tools 3 and 4 relative to each other. The device 1 includes a control unit 9.The control unit 9 is configured to control the movement of the press tools 3 and 4 relative to each other. Furthermore, the control unit 9 is configured to terminate the application of force once the predetermined target temperature has been reached. In particular, the application of force is intended to cease after a predetermined time. Specifically, the predetermined time is selected such that the target temperature is reached during the cooling process. In particular, the predetermined time can be determined empirically.

[0032] The Fig. Figure 4 shows a schematic representation of an embodiment of the device 1 for cooling a printed circuit board 10 after an oven-assisted soldering process. The embodiment is basically the same as that shown in the Fig.The embodiment shown in Figure 3 is designed as follows. Reference numerals denote identical features and terms. In the illustrated embodiment, the printed circuit board 10 is actively cooled during the application of force in the pressing device 2. For this purpose, a cooling device 6 is provided. Specifically, the printed circuit board 10 is cooled by means of a cooling gas. For this purpose, at least one channel 7 is provided in the pressing device 2, which is configured to supply the cooling gas to the printed circuit board 10. Specifically, the channel 7 is formed in at least one of the pressing tools 3, 4 and / or in a cover plate 12, in particular by means of bores and / or milling in at least one of the pressing tools 3, 4 and / or in the cover plate 12.In particular, at least one conveying unit 8 is provided, which is configured to convey the printed circuit board 10 into and / or out of the pressing device 2 and / or to position it in the lower pressing tool 3. In particular, the at least one conveying unit 8 comprises pneumatic cylinders which are configured to move the printed circuit board 10. In the illustrated embodiment, at least one temperature sensor 11 is provided. In particular, the temperature sensor 11 is configured to detect the temperature of the printed circuit board 10. A signal from the temperature sensor 11 is supplied to the control unit 9, which uses this signal to detect and / or verify whether the predetermined target temperature has been reached. Reference symbol list 1 Device 2 Pressing device 3 lower pressing tool 4 upper pressing tool 5 stamps 6 Cooling device 7-channel 8 Funding 9 Control unit 10 circuit boards 11 Temperature sensor 12 Cover plate 100-108 process steps

Claims

A method for cooling a printed circuit board (10) after an oven-assisted soldering process, wherein the temperature of the printed circuit board (10) after the soldering process is greater than a predetermined target temperature of the printed circuit board (10), comprising: - feeding the printed circuit board (10) to a lower pressing tool (3) of a pressing device (2), - arranging the printed circuit board (10) in the lower pressing tool (3), - closing the pressing device (2) by bringing together an upper pressing tool (4) of the pressing device (2) and the lower pressing tool (3), whereby punches (5) of the pressing tools (3, 4) contact the printed circuit board (10) at predetermined positions, - applying a force to the printed circuit board (10) by means of the punches (5), - cooling the printed circuit board (10) to the predetermined target temperature during the application of the force, so that the printed circuit board (10) solidifies in a predetermined shape, - ending the application of the force, characterized in thatthat the printed circuit board (10) is assembled in a press-fit process after cooling to the specified target temperature, wherein a press device used for the press-fit process is identical or structurally equivalent to the press device (2) in the cooling process, at least with regard to the positions of at least one part of the punches (5) of the press tools. Method according to claim 1, characterized in that the circuit board (10) is actively cooled during the application of force in the pressing device (2). Method according to claim 2, characterized in that the circuit board (10) is cooled by means of a cooling gas. Method according to one of the preceding claims, characterized in that the printed circuit board (10) is removed from the press (2) after cooling to the predetermined target temperature and cools or is cooled to a predetermined final temperature outside the press (2) and / or during a subsequent process step. Method according to claim 4, characterized in that the cooling to the predetermined final temperature takes place during a printed circuit board test. Method according to one of the preceding claims, characterized in that the pressing device (2) executes a predetermined path-time profile from which the applied force results. Device (1) for cooling a printed circuit board (10) after an oven-assisted soldering process, wherein the temperature of the printed circuit board (10) after the soldering process is greater than a predetermined target temperature of the printed circuit board (10), comprising: - a pressing device (2) configured to cool the printed circuit board (10) to the predetermined target temperature, - the pressing device (2) comprising an upper pressing tool (4) and a lower pressing tool (3), - the lower pressing tool (3) configured to hold the printed circuit board (10), - the pressing tools (3, 4) each comprising punches (5) configured to apply a force to the printed circuit board (10) at predetermined positions, - the pressing device (2) configured to move the pressing tools (3, 4) relative to each other, and - a control device (9) configured to control the movement of the pressing tools (3, 4).4) to control each other and which is designed to terminate the application of force after reaching the specified target temperature, characterized in that the printed circuit board (10) is assembled in a press-fit process after cooling to the specified target temperature, wherein a press device (2) used for the press-fit process is designed to be identical or structurally equivalent to the press device (2) in the cooling process, at least with respect to the positions of at least one part of the punches (5) of the press tools (3, 4). Device (1) according to claim 7, characterized by at least one temperature sensor (11) which is configured to detect a temperature of the circuit board (10). Device (1) according to claim 7 or 8, characterized by at least one channel (7) formed in the press device (2) which is configured to supply a cooling gas to the circuit board (10). Process arrangement comprising a soldering oven for oven-assisted soldering of the printed circuit board (10) and a device (1) for cooling the printed circuit board (10) according to one of the preceding claims 7 to 9 .

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