Method for determining the wave height of a soldering wave, device for determining the wave height of a soldering wave and wave soldering system

Abstract

Method for determining a wave height (H) of a soldering wave (42), wherein liquid solder (41) is conveyed through a soldering nozzle arrangement (12) to form the soldering wave (42), characterized by the steps: - placing an elastically flexible foil body (18) on the soldering wave (42) in such a way that the foil body (18) floats on the soldering wave (42), - determining the position of the surface of the foil body (18) floating on the soldering wave (42) with respect to a reference point (39), and - Determining the wave height (H) depending on the position of the film body (18).

Description

[0001] The invention relates to a method for determining the wave height of a soldering wave, a device for determining the wave height of a soldering wave and a wave soldering system.

[0002] In the production of populated printed circuit boards, it is known to connect the components arranged on the circuit board to the circuit board by wave soldering.

[0003] In wave soldering systems, a comparatively wide soldering wave of liquid solder is provided, whereby the components to be soldered are moved by the standing soldering wave.

[0004] In selective wave soldering systems, several solder nozzles are often arranged, for example on a nozzle plate, so that the nozzle outlets point essentially vertically upwards in the soldering position. The cross-section of each solder nozzle is shaped specifically for the soldering area, and each solder nozzle is assigned to a specific area of ​​the circuit board to be soldered. For soldering, the solder nozzle or nozzle plate with the solder nozzles arranged on it is moved from below towards the circuit board to be soldered. At the same time, the interior of the solder nozzle is flowed through from below with liquid solder. This liquid solder emerges in a wave-like manner from the nozzle opening, which is located at the top in the soldering position, and wets the soldering points on the circuit board positioned there, creating the desired solder connection between the component to be soldered - or between the wire projection of the component - and the corresponding area of ​​the circuit board's conductor track.

[0005] Precise control of all process parameters, such as temperatures, solder flow rates, spacing, feed rates, etc., is crucial in wave soldering and multi-wave soldering with multiple solder nozzles to achieve high-quality solder joints with high reproducibility. A key requirement in wave soldering is that the height of the wave of liquid solder can be precisely determined and adjusted.

[0006] A wave soldering machine with a wave height test system is known, for example, from DE 10 2015 212 960 A1. There, a needle is used in a reference nozzle, the free end of which defines a test height point. When the free end of the needle comes into contact with the liquid solder, an electrical signal is generated. This device can only determine whether the test height has been reached. It cannot determine by what degree the test height has been exceeded or undershot. Therefore, adjusting the pump drive to achieve a constant test height is not possible or only possible to a limited extent.

[0007] Another wave soldering machine is known from DE 10 2013 225 887 A1, in which a measuring element in the form of a measuring strip is provided, from which the height of the soldering wave is ultimately read.

[0008] DE 44 18 732 A1 discloses a method and device for measuring and / or controlling the height of a solder wave. The wave height is measured in a branch, with the wave height in the branch being determined via a sensor.

[0009] From CN 2 02 591 786 U, it is known to place a float on a shaft of liquid solder in order to determine its height relative to a reference point. The float can be connected via a connecting arrangement to a piston movable in a closed space. Pressure sensors present in the space can measure the changing pressure in the space when the volume of the space changes.

[0010] From DE 10 2018 105 900 A1 it is known to determine the height of the soldering wave via the buoyancy force of a floating body.

[0011] Further systems for determining the height of surfaces of liquids are known from CN 1 02 967 342 A, JP H07-270 216 A, DE 102 43 769 B4 and DE 197 04 764 A1.

[0012] The present invention is based on the object of providing a method for determining the wave height of a soldering wave, a device for determining the wave height of a soldering wave and a wave soldering system for operating such a method, with which the wave height can be measured in a simple and functionally reliable manner.

[0013] This object is achieved by a method having the features of patent claim 1. The method is characterized in particular by the following steps: - Placing an elastically flexible foil body on the soldering wave in such a way that the foil body floats on the soldering wave, - Determining the position of the surface of the foil body floating on the solder wave with respect to a reference point, and - Determine the wave height depending on the position of the film body.

[0014] By placing the elastically flexible foil body onto the soldering wave, it floats on or along the surface of the soldering wave. Due to its elastic design, the foil body can adapt to the surface of the soldering wave, at least in sections, or come to rest on it in a floating manner. The provision of the foil body forms a reference surface that can be easily measured. Even when the liquid solder flows relatively quickly and when eddies or vortexes form in the liquid solder, the surface of the foil body can be used as a reference surface and measuring plane. Because the foil body preferably has a very low thickness, in particular in the range of 0.1 mm to 0.3 mm and preferably in the range of 0.2 mm, it can be ensured that it floats on the liquid solder.Because the foil body has a certain width, which is preferably in the range of 1 cm to 10 cm, and more preferably in the range of 2 cm to 5 cm, the foil body ultimately forms an average value for the height of the area of ​​the solder wave which it covers.

[0015] By determining the position of the surface of the foil body floating on the solder wave relative to a reference point, the wave height of the solder wave can ultimately be determined. The higher the wave height, the greater or smaller the distance from the reference point to the surface of the foil body.

[0016] It has proven advantageous to first measure a reference distance between the reference point and a measuring unit to determine the position of the foil body's surface. A reference measurement is therefore first used to measure how far away the reference point is from the measuring unit. To determine the wave height, a wave distance between the surface of the foil body floating on the soldering wave and the measuring unit is then measured. This measures how far away the surface of the foil body floating on the soldering wave and deflected by the soldering wave is from the measuring unit. The wave height can then be determined from the difference between the reference distance and the wave distance, taking other variables or geometries into account if necessary.

[0017] It is conceivable that the surface of the foil body resting on an edge of the soldering nozzle arrangement is used as the reference point. In particular, when no liquid solder is emerging from the soldering nozzle arrangement, the foil body can be placed on the soldering nozzle arrangement or its tear-off edge. The reference point is then formed by the surface of the foil body. The reference distance is then the distance between the surface of the foil body resting on the edge and the measuring unit. If liquid solder flows through the soldering nozzle arrangement, the foil body changes its position relative to the edge of the soldering nozzle arrangement and floats on the liquid solder. The wave distance from the surface of the foil body deflected by the wave to the measuring unit is reduced compared to the reference distance. In this case, the wave height can be determined by calculating the difference between the reference distance and the wave distance.

[0018] It is also conceivable that the surface of the foil body resting on the edge of the soldering nozzle arrangement is not used as the reference point, but rather that the edge of the soldering nozzle arrangement is used directly. The reference point is then independent of the foil body. Furthermore, it is conceivable that other locations could be used as reference points.

[0019] The measurement of the reference distance and the wave distance can be carried out in particular by means of a radar measuring unit, a laser measuring unit, an optical, inductive or capacitive measuring unit and / or with an ultrasonic measuring unit.

[0020] The object mentioned above is also achieved by a device for determining the wave height of a soldering wave formed from liquid solder and conveyed by a soldering nozzle arrangement, wherein the device comprises an elastically flexible foil body for floating placement on the soldering wave, a measuring unit for determining the position of the surface of the foil body floating on the soldering wave with respect to a reference point, and an evaluation unit for determining the wave height as a function of the position of the foil body. Depending on the wave height, the foil body therefore assumes a different position in space. The measuring unit can detect this position with respect to the reference point. The evaluation unit ultimately determines the wave height from the detected position.

[0021] It is conceivable that the measuring unit and the evaluation unit are designed as a common component, with this one component then containing the measuring function and the evaluation function.

[0022] It is also advantageous if the measuring unit is configured to measure a reference distance between the reference point and the measuring unit, and to measure a wave distance between the surface of the foil body floating on the solder wave and the measuring unit. The wave distance is therefore the distance between the surface of the solder wave or the top side of the foil body floating on the solder wave and the measuring unit. From these two distances, the wave height can then be determined for known geometries.

[0023] For precise positioning of the film body and / or the measuring unit, it is advantageous if the film body and / or the measuring unit are arranged on a holding device. The holding device can position the film body and the measuring unit relative to each other in space. The holding device can also be designed as a holding frame that encloses the measuring unit and / or the film body at least in sections.

[0024] It is also advantageous if the holding device has a displacement mechanism with which the foil body can be displaced between a measuring position, in which it rests floatingly on the solder wave, and a parking position, in which it is in a parking position. While the wave height can be determined in the measuring position, the components can be soldered in the parking position without the holding device interfering with the process.

[0025] The displacement mechanism can be designed as a lifting mechanism for displacing the film body, particularly in a vertical direction, for retraction and extension. In the retracted position, the film body is then located in the parking position, and in the extended position, it is located in the measuring position.

[0026] It is also conceivable that the displacement mechanism is designed as a pivoting mechanism for pivoting the film body around a pivot axis into the measuring position and pivoting it out into the parking position. If the wave height is to be measured, the film body is then pivoted into the measuring position.

[0027] Furthermore, it is conceivable to provide an adapter element that forms an acute angle with a vertical plane, with the foil body being arranged on the adapter element. The adapter element ensures that the foil body, when not floating on the shaft, assumes a position that at least largely corresponds to the surface of the shaft. The foil body can thus be aligned parallel to the shaft surface and thus guided toward the soldering wave.

[0028] It has proven advantageous for the film body to be constructed from sheet metal. However, it is also conceivable to use a plastic material for the film body.

[0029] It is also advantageous if the film body has a surface that is easily detectable by the measuring unit. For this purpose, the film body can, for example, be provided with a suitable coating or a suitable color.

[0030] It is also conceivable that the foil body has a rectangular shape in plan view with two long sides and two short sides. The shape is particularly such that the foil body can rest on the solder wave in a largely free-floating manner.

[0031] It is further advantageous if the film body has a base surface and edge regions with free edges, wherein the edge regions form an angle in the range of 30° to 150°, and in particular in the range of 70° to 110°, and further in particular in the range of 90°, with the base surface. The edge regions are preferably connected to one another in a fluid-tight manner and are designed in such a way that flooding of the film body is prevented, thus ensuring that the film body floats on the surface of the soldering wave.

[0032] The object mentioned at the outset is also achieved by a wave soldering system with a soldering nozzle arrangement, with a pump for conveying liquid solder through the soldering nozzle arrangement to form a soldering wave and with a device according to the invention for determining the wave height of the soldering wave.

[0033] It is advantageous if the wave soldering system has a travel unit that can be moved along an x-direction and / or y-direction, wherein the device for determining the wave height is arranged on the travel unit.

[0034] Furthermore, it is conceivable that not just one device, but several devices could be provided on such a traversing unit. This has the advantage that, with a comparatively wide solder wave, the height of the solder wave can be determined at different points. This can also increase process reliability.

[0035] To prevent contamination or damage to the measuring unit, it is advantageous to provide a protective screen between the film body and the measuring unit. The protective screen serves primarily as splash and heat protection for the measuring unit.

[0036] Further details and advantageous embodiments of the invention can be found in the following description, on the basis of which embodiments of the invention are described and explained in more detail.

[0037] They show: Fig. 1 a wave soldering system with a device for determining the wave height in a reference state; Fig. 2 the wave soldering system according to Fig. 1 in a measuring state; and Fig. 3 a foil body for a device for determining the wave height with an adapter.

[0038] In the Fig. 1 shows a wave soldering system 10 which provides a soldering nozzle arrangement 12 and a pump 14 for pumping liquid solder through the soldering nozzle arrangement 12. In Fig. 1, no liquid solder is pumped by the pump 14 through the soldering nozzle arrangement 12.

[0039] Fig. 1 further shows a device 16 for determining the wave height of a soldering wave, wherein the device 16 has an elastically flexible foil body 18 arranged on a holding device 20. The holding device 20 in turn has a displacement mechanism 22, which is designed as a lifting mechanism for displacing the foil body 18 in the direction of a vertically extending z-axis. The displacement mechanism 22 is formed by a base body 24 with actuators 26 movable therein in the direction of the z-axis. The actuators 26 can therefore be extended and retracted in the direction of the z-axis. An adapter element 28 is provided at the free ends of the actuators 26, to which the foil body 18 is ultimately fastened. The adapter element 28 is arranged such that it forms an acute angle w with a horizontal line 30, so that the foil element 18 is ultimately also arranged obliquely to the horizontal line 30.

[0040] The foil element 18 is in turn designed in particular as a spring steel sheet and has a rectangular basic shape with two long sides 32 and two narrow sides 34. One narrow side 34 is fixedly arranged on the adapter element 28. The other narrow side 34 is a free narrow side, which in Fig. 1 rests against a tear-off edge 36 of the soldering nozzle arrangement 12. The foil body 18 has a thickness of, in particular, 0.1 mm to 0.2 mm. In particular, the wave height H is detectable with a tolerance of + / -0.1 mm to 0.25 mm. The elasticity of the foil body 18 is designed to ensure that it is deflected by a soldering wave 42 and floats safely on it.

[0041] In order to ensure that the free narrow side 34 comes to rest against the tear-off edge 36, the adapter element 28 together with the film body 18 can be moved in the z-direction via the displacement mechanism 22 until the film body 18, or its free narrow side 34, comes to rest against the tear-off edge 36.

[0042] The device 16 further comprises a measuring unit 38 in the form of a laser measuring unit, which measures the distance A1 between a reference point 39, which lies on the surface of the film body 18 resting on the tear-off edge 36, and the measuring unit 38. The distance A 1 is a reference distance, as it is measured without taking into account the soldering wave that forms during operation of the system.

[0043] The surface of the film body 18 is in particular painted or coated to enable an accurate measurement of the distance A by the measuring unit 38.

[0044] The device 16 can be connected to a Fig. 1 only schematically indicated movement unit 40 can be arranged to be movable in a y-direction running transversely to the z-direction.

[0045] During operation of the wave soldering system 10, i.e. when circuit boards are being soldered, the device 16 is in a parking position (not shown).

[0046] If the wave height H of a Fig. 2, consisting of liquid solder 41, generated by the pump 14 and passing through the soldering nozzle arrangement 12, the device 16 is moved from the parking position not shown in the figures into the position shown in the Fig. 2. The device 16 is in the same position as in Fig. 1. Due to the presence of the soldering wave 42 and the placement of the flexible foil body 18 on the soldering wave 42, the foil body 18 floats on the soldering wave 42 and is thus deflected upwards due to the presence of the soldering wave 42.

[0047] This results in a wave distance A between the measuring unit 38 and the surface of the foil body 18 floating on the solder wave 42 2 .

[0048] So in the Fig. 2, the distance between the measuring unit 38 and the surface of the film body 18 is measured, and this distance A 2 with the reference distance A 1 Compared to the wave height H, the wave height can be determined by means of a Fig. 1 and Fig. 2 schematically indicated evaluation unit 44. In the embodiment shown in the figures, the wave height H can be determined by the difference between the reference distance A1 and the shaft spacing A 2 determine: H = A 1 - A 2 The evaluation unit 44 can be integrated into the measuring unit 38.

[0049] The measurement of the distances A 1 and A 2 This preferably takes place in the area of ​​the surface of the foil body 18, the underside of which is in the liquid solder of the soldering wave.

[0050] According to the invention, however, it is conceivable that the reference point 39, as shown in Fig. 1, is not located on the surface of the joint body, but is formed, for example, by the separation edge 36. In this case, geometric conditions, such as the thickness of the film body 18, must be taken into account when determining the wave height H.

[0051] The wave height H determined by the device 16 can, in particular, be displayed to a user or communicated to a higher-level control system. Depending on the wave height H, signals can then be generated and / or measures taken.

[0052] In order to protect the measuring unit 38 from heat and solder splashes, a Fig. 2 indicated protective screen 48 is provided.

[0053] Even if in the figures the distance A 2 between the measuring unit 38 and the surface of the film body 18 is measured at only one point, it is conceivable that the measurement is carried out at several points so that a more precise, possibly averaged, measurement result is achieved.

[0054] In the Fig.3 shows an alternative embodiment of a foil body 18 on an adapter element 28. The foil body 18 has, in the region of its free narrow side 34 and in the region of the sections of the long sides 32 facing the narrow side 34, edge regions 46 which are folded upwards perpendicular to the plane of the foil body 18. The folded regions are fluid-tightly connected to one another at the corners. This improves the floating behavior of the foil body 18 on the soldering wave 42. Furthermore, it is prevented that liquid solder 41 floods the upper side of the foil body 18, which would ultimately falsify the measurement result. Instead of or in addition to the upwardly folded edge regions 46, it is conceivable that further and / or additional elements or means are provided on the upper side of the foil body 18 to prevent the foil body from being immersed in the soldering wave.

Claims

[1] Method for determining a wave height (H) of a soldering wave (42), wherein liquid solder (41) is conveyed through a soldering nozzle arrangement (12) to form the soldering wave (42), characterized by the steps: - placing an elastically flexible foil body (18) on the soldering wave (42) in such a way that the foil body (18) floats on the soldering wave (42), - determining the position of the surface of the foil body (18) floating on the soldering wave (42) with respect to a reference point (39), and - Determining the wave height (H) depending on the position of the film body (18). [2] Method according to claim 1, wherein for determining the relative position of the surface of the film body (18) a reference distance (A 1 ) between the reference point (39) and a measuring unit (38) is measured and that a shaft distance (A 2) between the surface of the foil body (18) floating on the soldering wave (42) and the measuring unit (38) is measured. [3] Method according to claim 1 or 2, wherein the surface of the foil body (18) resting on an edge (36) of the soldering nozzle arrangement (12) is used as the reference point (39). [4] Method according to claim 1, 2 or 3, wherein an edge (36) of the soldering nozzle arrangement (12) is used as the reference point (39). [5] A method according to claim 2, 3 or 4, wherein measuring the distance (A 1 , A 2 ) by means of a measuring unit (38) in the form of a radar measuring unit, a laser measuring unit, an optical, inductive or capacitive measuring unit and / or with an ultrasonic measuring unit. [6] Device (16) for determining a wave height (H) of a soldering wave (42) formed from liquid solder (41) and conveyed through a soldering nozzle arrangement (12), with an elastically flexible foil body (18) for floating placement on the soldering wave (42), with a measuring unit (38) for determining the position of the surface of the foil body (18) floating on the soldering wave (42) with respect to a reference point (39), and with an evaluation unit (44) for determining the wave height (H) depending on the position of the film body (18). [7] Device (16) according to claim 6, wherein the measuring unit (38) for measuring a reference distance (A 1 ) between the reference point (39) and the measuring unit (38) and for measuring a shaft distance (A 2 ) between the surface of the foil body (18) floating on the soldering wave (42) and the measuring unit (38). [8] Device (16) according to claim 6 or 7, wherein the film body (18) and / or the measuring unit (38) are arranged on a holding device (20). [9] Device (16) according to claim 8, wherein the holding device (20) has a displacement mechanism (22) with which the film body (18) can be displaced between a measuring position in which it rests floatingly on the soldering wave (42) and a parking position in which it is in a parking position. [10] Device (16) according to claim 9, wherein the displacement mechanism (22) is designed as a lifting mechanism for displacing the film body (18) in the vertical direction for retraction and extension. [11] Device (16) according to claim 9, wherein the displacement mechanism (22) is designed as a pivoting mechanism for pivoting the film body (18) about a pivot axis into the measuring position and for pivoting out into the parking position. [12] Device (16) according to one of claims 8 to 11, wherein the holding device (20) has an adapter element (28) which forms an acute angle (w) with a vertical plane (30) and on which the film body (18) is arranged. [13] Device (16) according to one of claims 6 to 12, wherein the film body (18) is formed from a metal sheet. [14] Device (16) according to one of claims 6 to 13, wherein the film body (18) has a rectangular shape in plan view with two long sides (32) and two narrow sides (34). [15] Device (16) according to one of claims 6 to 14, wherein the film body (18) has a base surface and edge regions (46) with free edges, wherein the edge regions (46) enclose an angle in the range of 30-150°, and in particular in the range of 70-110° and further in particular in the range of 90° with respect to the base surface. [16] Wave soldering system (10) with a soldering nozzle arrangement (12), with a pump (14) for conveying liquid solder (41) through the soldering nozzle arrangement (12) to form a soldering wave (42) and with a device (16) according to one of claims 6-15. [17] Wave soldering system (10) according to claim 16, with a displacement unit (40) movable along an x-direction and / or y-direction, wherein the device (16) is arranged on the displacement unit (40). [18] Wave soldering system (10) according to claim 16 or 17, wherein a protective disc (48) is provided between the film body (18) and the measuring unit (38).

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