Calibration tool for a selective soldering unit, selective soldering system and calibration procedure

Abstract

The present invention relates to a calibration tool (1) for a selective soldering system (100) comprising at least a workpiece carrier unit (2) for receiving at least one workpiece (3), such as a circuit board (4), and at least one distance measuring unit (5) which can be accommodated within the workpiece carrier unit (2) for calibrating a distance (2b) of a support surface (2a) of the workpiece carrier unit (2) to at least one soldering nozzle (6) of a soldering unit (102); and / or at least one temperature measuring unit (7) which can be accommodated within the workpiece carrier unit (2) for calibrating at least one heating power of a preheating unit (101); and / or at least one wave height measuring unit (8) which can be accommodated within the workpiece carrier unit (2) for calibrating the wave height (9) of the solder at at least one soldering nozzle (6) of the soldering unit (102).The invention further relates to a selective soldering system (100) and a method for calibrating the selective soldering system (100).

Description

[0001] The present invention relates to a calibration tool for a selective soldering system, a selective soldering system with a calibration tool and a method for calibrating a selective soldering system.

[0002] Selective soldering of components, e.g., onto printed circuit boards, is carried out industrially, for example, using automated selective soldering systems. The printed circuit boards are first placed in workpiece holders, then preheated to the required temperature, and then the components are selectively soldered. A mini-wave soldering process is often used, in which the liquefied solder is continuously transported to the soldering point using a soldering nozzle. For optimal soldering results, the wave height resulting from the continuous solder flow at the soldering nozzle and the distance between the printed circuit board and the soldering nozzle must be precisely adjusted to the desired values. Furthermore, the preheating temperature must correspond to the desired value.

[0003] The individual parameters of a selective soldering system, such as soldering temperature, distance between the soldering nozzles and the circuit board, and the wave height of the solder at the soldering nozzle, must be recalibrated for each workpiece. Currently, this is primarily done manually by the user. For this purpose, an empirical value is initially assumed for each individual parameter, such as the heating power of a preheating pyrometer. The circuit board is then heated and removed, and the preheating temperature of the circuit board is then measured manually. The heating power of the preheating pyrometer is then adjusted and monitored until the desired target value is reached. Parameters such as the heating power are always adjusted based on the experience of the user calibrating the selective soldering system. The other parameters are also calibrated in a similar manner, making the calibration of the individual parameters time-consuming.Especially with small or medium batches, this leads to long downtimes and high personnel costs, which make the selective soldering system uneconomical to operate.

[0004] It is therefore the object of the present invention to reduce the downtime of a selective soldering system and thereby increase the economic efficiency of the selective soldering system.

[0005] The object is achieved by a calibration tool for a selective soldering system having the features of claim 1 and a selective soldering system having the features of claim 12, as well as a method for calibrating the selective soldering system having the features of claim 13. Advantageous developments are the subject of the subclaims. Further properties and advantages will become apparent from the general description and the description of the exemplary embodiments.

[0006] The calibration tool according to the invention for a selective soldering system comprises at least: - in particular a workpiece carrier unit for receiving at least one workpiece, such as a printed circuit board; and - at least one temperature measuring unit, which can be accommodated within the workpiece carrier unit, for calibrating at least one heating power of a preheating unit; and / or - at least one distance measuring unit, which can be accommodated within the workpiece carrier unit, for calibrating a distance between a support surface of the workpiece carrier unit and at least one soldering nozzle of a soldering unit; and / or - at least one wave height measuring unit, which can be accommodated within the workpiece carrier unit, for calibrating the wave height of the solder on at least one soldering nozzle of the soldering unit.

[0007] The invention has many advantages. A significant advantage of the invention is that the calibration tool allows the key parameters of the selective soldering system to be measured and calibrated directly, particularly in situ, i.e., the individual parameters of the selective soldering system can be set to target values. Fast calibration is essentially independent of the operator's experience, as the operator always receives rapid feedback when the settings are changed. This advantageously reduces the downtime of the selective soldering system, resulting in greater overall economic efficiency of the selective soldering system. Advantageously, by combining the temperature measuring unit, the distance measuring unit, and / or the wave height measuring unit, calibration can be performed using a single calibration tool, further increasing the economic efficiency of the selective soldering system.

[0008] Preferably, at least one test workpiece, such as a circuit board or a component with a circuit board shape, is comprised by the temperature measuring unit, the distance measuring unit and / or the wave height measuring unit, which can be accommodated or is accommodated in the workpiece carrier unit.

[0009] The temperature measuring unit preferably comprises a plurality of temperature measuring sensors in order to be able to detect a temperature at various locations, in particular on the test workpiece. This advantageously allows a temperature distribution on a test workpiece within the preheating unit to be detected and directly adjusted.

[0010] Particularly preferably, the temperature sensors are designed as thermocouples, in particular type K, which are attached to the test workpiece in order to measure the temperature there, in particular directly at the soldering points. These elements are particularly sensor-based and preferably consist mostly of the nickel-chromium / nickel-aluminum compound and are designed for the temperature range of preferably -200°C to 1260°C. The temperature measuring unit preferably comprises at least two or four or six or even more thermocouples. Advantageously, the thermocouples are particularly robust and cost-effective. Furthermore, the thermocouples can directly detect the temperature of the test workpiece.

[0011] The distance measuring unit preferably comprises at least one laser sensor for distance measurement. The laser sensor advantageously has a high measurement resolution and high repeatability, making it particularly suitable for distance measurement. This advantageously allows for setting an optimal distance between the workpiece carrier unit, and thus a workpiece, and the soldering nozzle(s) of the selective soldering system.

[0012] The distance measuring unit preferably comprises at least one support unit with at least one support body of a defined thickness that is movable along a vertical direction. The support body preferably rests on the soldering nozzle for distance measurement. Advantageously, the laser sensor can also be arranged on a side opposite the soldering nozzle to measure the distance. Advantageously, the support body can also rest on multiple soldering nozzles, so that a distance to multiple soldering nozzles can be determined.

[0013] In particular, the support unit comprises at least one spring element for preloading the support body against the soldering nozzle. Advantageously, the support body is preloaded against one or more soldering nozzles by the spring element, enabling precise measurement of the distance between the support surface of the workpiece carrier unit and the soldering nozzle.

[0014] The wave height measuring unit preferably has at least one measuring point and preferably a plurality of measuring points for measuring the wave height of the solder of one or more soldering nozzles. This advantageously allows the wave height of different soldering nozzles to be calibrated simultaneously.

[0015] Preferably, the wave height of the solder of a soldering nozzle is measured using contact measuring sensors. In particular, at least two or four or more contact measuring sensors are included, which are attached to the calibration tool in such a way that they contact the solder wave at the outer edges, and in particular in the corners of the soldering nozzle. This advantageously allows the wave height of the solder of a soldering nozzle to be precisely measured and calibrated.

[0016] At least one evaluation unit is expediently included for evaluating a measurement signal from the temperature measuring unit, a measurement signal from the distance measuring unit, and / or a measurement signal from the wave height measuring unit. Advantageously, the measurement results can be evaluated directly in the calibration tool. Advantageously, the evaluation unit is designed as a microprocessor, in particular as an Arduino microprocessor. Furthermore, the measurement signals from all measuring units can be evaluated by an Arduino microprocessor. Particularly advantageously, a measured value can be compared with a target value within the evaluation unit.

[0017] The calibration tool preferably comprises at least one display unit for indicating whether a setpoint for the temperature, the distance, and / or the wave height of the solder is calibrated and corresponds to the respective setpoint. Particularly advantageously, an evaluated measurement value can be directly displayed by the display unit and interpreted by the user. In particular, the display unit comprises various LEDs, and in particular at least one LED per sensor. Preferably, for example, the color of the LEDs can indicate whether a measured value corresponds to a setpoint or not. Advantageously, the user calibrating the parameters of the selective soldering system can thereby receive direct feedback on the current setting and a change to a parameter.

[0018] Preferably, at least one housing unit is included for accommodating at least the evaluation unit and / or the display unit. Advantageously, the housing unit provides mechanical and, in particular, thermal protection for the evaluation unit and / or the display unit. Particularly advantageously, the housing unit can be arranged on or at the workpiece carrier unit.

[0019] The selective soldering system according to the invention comprises at least one preheating unit for preheating a workpiece, such as a printed circuit board, before a soldering process and / or at least one soldering unit with at least one soldering nozzle for selectively producing a solder connection on a printed circuit board, and at least one calibration tool as described above. Further developments and advantages of the selective soldering system according to the invention are apparent from the entire application.

[0020] The method according to the invention for calibrating the preheating unit and / or the soldering unit of a previously described selective soldering system using a previously described calibration tool comprises at least the following method steps: - measuring a preheating temperature by means of the temperature measuring unit and adjusting a heating output of the preheating unit, in particular until a setpoint is reached; and / or - measuring the distance of the workpiece receiving surface of the workpiece carrier unit by means of the distance measuring unit and adjusting the distance of the workpiece receiving surface to at least one soldering nozzle, in particular until a target value is reached; and / or - Measuring the wave height of the solder of at least one soldering nozzle and adjusting at least one wave height on the soldering nozzle on the soldering unit, in particular until a target value is reached.

[0021] The method according to the invention also has many advantages. A significant advantage of the method is that calibration of the selective soldering system can be performed considerably faster using the calibration tool than previously known in the prior art, thus reducing downtime and personnel costs and improving the economic efficiency of the selective soldering system. Further developments and advantages of the method according to the invention are set out in the entire application.

[0022] Further features and advantages of embodiments of the invention are described below with reference to the drawings. The same reference numerals are used for identical or similar parts and for parts with identical or similar functions. They show: Fig. 1 a purely schematic process diagram of a selective soldering system according to the invention; Fig. 2 a purely schematic view of a calibration tool according to the invention with a temperature measuring unit; Fig. 3 a purely schematic view of a calibration tool according to the invention with a distance measuring unit; and Fig. 4 a purely schematic view of a calibration tool according to the invention with a wave height measuring unit.

[0023] Fig. 1 shows a purely schematic process diagram of a selective soldering system 100 according to the invention. For the selective soldering of components onto workpieces 3, such as a printed circuit board 4, the latter is inserted into a workpiece carrier unit 2.

[0024] The workpiece 3 is then heated in a preheating unit 101. Pyrometers 101 are used for this purpose. Subsequently, a flux is applied by a flux application unit 103. The workpiece 3 is then gradually heated to the temperature required for soldering in two further preheating units 101 using pyrometers 101.

[0025] In the soldering unit 102, components are selectively soldered into the workpiece 3. Subsequently, a two-stage cleaning of the soldering points takes place by brushing units 104 before the finished soldered workpiece 3 is cooled in a controlled manner in a cooling unit 105.

[0026] Fig. 2 shows a purely schematic view of a calibration tool 1 according to the invention with a temperature measuring unit 7. The temperature measuring unit 7 here comprises a test workpiece 3 in the form of a printed circuit board 4, which is accommodated in the workpiece carrier unit 2. Six temperature measuring sensors 10 in the form of type K thermocouples are applied to the test workpiece 3. The temperature measuring sensors 10 are distributed over the test workpiece 3 and connected to an evaluation unit 13. The evaluation unit 13 records the measurement signals of all temperature measuring sensors 10 and evaluates them. For this purpose, the evaluation unit 13 comprises an analog-to-digital converter. The evaluation unit 13 is designed here as an Arduino microprocessor. The evaluation unit 13 further performs a setpoint comparison between the measured temperature and a predetermined setpoint temperature for each temperature measuring sensor. The result of the setpoint comparison is transmitted to a display unit 14.The result of the setpoint comparison is displayed via LEDs 14a. Each temperature sensor is assigned an LED. Depending on the color of the LED, the user receives feedback indicating whether a setpoint temperature has been reached, is below, or has already been exceeded. Accordingly, the user can adjust the heating output of a pyrometer 101 of a preheating unit 101 and thus calibrate the preheating unit 101 of the selective soldering system 100 directly, in situ.

[0027] Fig. 3 shows a purely schematic view of a calibration tool 1 according to the invention with a distance measuring unit 5. The distance measuring unit 5 is accommodated in the workpiece carrier unit 2. The distance measuring unit 5 comprises a support unit 12. The support unit 12 here comprises a contact body 12b which is movable in a height direction, transversely to a plane of a support surface 2a of the workpiece carrier unit 2 and which, preloaded by a spring element 12a, rests on soldering nozzles 6 of the soldering unit 102. The distance measuring unit 5 rests on the support surface 2a of the workpiece carrier unit 2. The support body 12b has a defined thickness here, so that a distance 2b between the support surface 2a and the soldering nozzles 6 can be determined by means of a measurement by a laser sensor 11, which is arranged at a defined height. The optimal distance 2b here is, for example, B. between 0.5 mm and 1 mm depending on the selective soldering system 100.The evaluation unit 13 evaluates the measurement signal from the laser sensor 11 and compares it with the target value. The result of the comparison is displayed via LEDs 14a on the display unit 14. The distance 2b can be adjusted by screwing in or out adjustment elements 102a, which are designed here as threaded rods with cap nuts 102a, to directly calibrate the distance 2b.

[0028] Fig.4 shows a purely schematic view of a calibration tool 1 according to the invention with a wave height measuring unit 8 for measuring the wave height 9 of the solder. The wave height measuring unit 8 is accommodated in the workpiece carrier unit 2. There is a measuring point for each soldering nozzle 6. Each measuring point has several contact measuring sensors 12c, which are arranged at an optimal distance at the corners of the soldering nozzle 6 with a rectangular cross-section. In this way, a solder flow in the soldering nozzles 6 can be adjusted so that an optimal wave height 9 of the solder is present for the soldering process at each soldering nozzle 6. The measurement signals of the contact measuring sensors 12c are evaluated by the evaluation unit 13, and the result is displayed to the user by the display unit 14 via LEDs 14a, so that the user can directly calibrate the wave height 9 of the solder.

[0029] Advantageously, the calibration tool 1 enables efficient and rapid calibration of the individual parameters of a selective soldering system 100. During use, a user receives direct feedback on the current parameter setting and can adjust it directly, i.e., in situ, to optimally calibrate the parameters of the selective soldering system 100. The influence of the user's experience is thus minimized, since the user receives direct feedback on a change in the parameter setting. Advantageously, this can at least significantly reduce the downtime of a selective soldering system 100, thus increasing the economic efficiency of the selective soldering system 100. List of reference symbols 1 calibration tool 2 workpiece carrier unit 2a Support surface 2b Distance between contact surface and soldering nozzle 3 Workpiece, test workpiece 4 Printed circuit board, printed circuit board shape 5 Distance measuring unit 6 soldering nozzle 7 Temperature measuring unit 8 Wave height measuring unit 9 Wave height of the plumb line 10 temperature measurement sensor, thermocouple 11 Laser sensor 12 support unit 12a spring element 12b Support body 12c contact measuring sensor 13 Evaluation unit 14 Display unit 14a Display element, LED 15 Housing unit 100 selective soldering system 101 Preheating unit, pyrometer 102 soldering unit 102a Adjusting element, threaded rod with cap nut 103 Flux application unit 104 Brush unit 105 Cooling unit

Claims

[1] Calibration tool (1) for a selective soldering system (100) at least comprising: - a workpiece carrier unit (2) for receiving at least one workpiece (3), such as a printed circuit board (4); and - at least one distance measuring unit (5), which can be accommodated within the workpiece carrier unit (2), for calibrating a distance (2b) between a support surface (2a) of the workpiece carrier unit (2) and at least one soldering nozzle (6) of a soldering unit (102); and / or - at least one temperature measuring unit (7), which can be accommodated within the workpiece carrier unit (2), for calibrating at least one heating power of a preheating unit (101); and / or - at least one wave height measuring unit (8), which can be accommodated within the workpiece carrier unit (2), for calibrating the wave height (9) of the solder on at least one soldering nozzle (6) of the soldering unit (102). [2] Calibration tool (1) according to claim 1, wherein the temperature measuring unit (7) comprises a plurality of temperature measuring sensors (10) in order to be able to detect a temperature at different locations within the workpiece holding unit (2). [3] Calibration tool (1) according to the preceding claim, wherein the temperature sensors (10) are at least partially designed as thermocouples (10), in particular of type K. [4] Calibration tool (1) according to one of the preceding claims, wherein the distance measuring unit (5) comprises at least one laser sensor (11) for distance measurement. [5] Calibration tool (1) according to one of the preceding claims, wherein the distance measuring unit (5) comprises at least one support unit (12) with at least one support body (12b) movable along a height direction, wherein the support body (12b) rests with a defined thickness on the soldering nozzle (6) for distance measurement. [6] Calibration tool (1) according to the preceding claim, wherein the support unit (12) comprises at least one spring element (12a) for preloading the support body (12b) against the soldering nozzle (6). [7] Calibration tool (1) according to one of the preceding claims, wherein the wave height measuring unit (8) has a plurality of measuring points for measuring the wave height (9) of the solder of a plurality of soldering nozzles (6). [8] Calibration tool (1) according to one of the preceding claims, wherein a measurement of the wave height (9) of the solder of a soldering nozzle (6) is carried out by means of, in particular four, contact measuring sensors (12c). [9] Calibration tool (1) according to one of the preceding claims, comprising at least one evaluation unit (13) for evaluating a measurement signal of the temperature measuring unit (7), a measurement signal of the distance measuring unit (5) and / or a measurement signal of the wave height measuring unit (8). [10] Calibration tool (1) according to one of the preceding claims, comprising at least one display unit (13) for displaying whether a target value for the temperature, the distance (2b) and / or the wave height (9) of the plumb line has been reached. [11] Calibration tool (1) according to one of the two preceding claims, comprising at least one housing unit (15) at least for accommodating the evaluation unit (13) and / or the display unit (14). [12] Selective soldering system (100), comprising at least one preheating unit (101) for preheating a workpiece (3), such as a printed circuit board (4) before a soldering process and / or at least one soldering unit (102) with at least one soldering nozzle (6) for selectively producing a solder connection on a printed circuit board (4) and at least one calibration tool (1) according to one of the preceding claims. [13] Method for calibrating the preheating unit (101) and / or the soldering unit (102) of a selective soldering system (100) according to the preceding claim using a calibration tool (1) according to one of claims 1 to 11, comprising at least the following method steps: - measuring a preheating temperature by means of the temperature measuring unit (7), and setting a heating power of the preheating unit (101); and / or - measuring the distance of the workpiece receiving surface (2a) of the workpiece carrier unit (2) by means of the distance measuring unit (7) and adjusting the distance of the workpiece receiving surface (2a) to at least one soldering nozzle (6); and / or - Measuring the wave height (9) of the solder of at least one soldering nozzle (6) and setting at least one wave height (9) of the solder on the soldering nozzle (6) of the soldering unit (102).

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