Test unit for checking a solder joint

Abstract

The present invention relates to a testing unit (10) for checking a solder joint (12), comprising a laser unit (14) and a microphone (16), wherein the laser unit (14) is configured to irradiate at least one component (18) of a plurality of components (20) of an electronic unit (22) having the solder joint (12) with a predetermined light beam, so that the solder joint (12) can be mechanically excited by means of the predetermined light beam, forming a propagating structure-borne sound, wherein the microphone (16) is configured to receive a sound wave formed by the radiation of the structure-borne sound, which represents the excitation of the solder joint (12), wherein the solder joint (12) has a first part (24) on a first side (26) of a printed circuit board (28), wherein the solder joint (12) has a second part (30) on a second side (32) of the printed circuit board (28), which is remote from the first side (26),wherein the testing unit (16) is configured to determine at least a first property of the first part (24) and a second property of the second part (30) by means of the received sound wave.,

Description

State of the art

[0001] The present invention relates to a test unit for checking a solder joint and a vehicle.

[0002] Currently, there are a variety of different solutions for inspecting solder joints. Due to the increasing number of solder joints in the automotive sector and the increased quality and durability requirements, the need for innovative and robust methods for inspecting solder joints is continuously growing.

[0003] The constant weight reduction in the vehicle sector for fuel consumption calculation as well as increasing competition are creating cost pressure, so that cheaper and more efficient components for vehicles are in greater demand. Disclosure of the invention

[0004] The test unit according to the invention for checking a solder joint with the features of claim 1 has the advantage over known ones that correct contacting can be checked very quickly using non-destructive testing. Only a very small sensor head is required, and the test unit can be used for both small and large components. More preferably, even defects or deviations in the solder joint can be visualized using appropriate process steps. A further advantage is that the test unit can be used over a very wide measuring range, and that production noise does not impair the measurement, as is the case with conventional acoustic microphones, for example.

[0005] This is achieved according to the invention in that the testing unit for checking a solder joint comprises a laser unit and a microphone, in particular an acousto-optical microphone. The laser unit is configured to irradiate at least one component of a plurality of components of an electronic unit having the solder joint and / or the region of the solder joint with a predetermined laser beam or light beam, such that the solder joint can be mechanically excited by means of the predetermined light beams, forming structure-borne sound that propagates in the components of the electronic unit.Furthermore, the microphone is configured to receive a sound wave which maps the mechanical excitation of the solder joint by radiating the structure-borne sound formed to the immediate surroundings, wherein the solder joint has a first part on a first side of a printed circuit board, wherein the solder joint has a second part on a second side of the printed circuit board which faces away from the first side, wherein the test unit is configured to determine at least a first property of the first part and a second property of the second part by means of the received test beam.

[0006] Based on the mechanical excitation of the solder joint and the resulting emitted sound wave, the testing unit can determine, in particular, a first property of a first part of the solder joint located on the top side of a circuit board and a second property of a second part of the solder joint located on the underside of the circuit board. This makes it possible, for example, to determine whether sufficient solder could be applied to both sides of the circuit board to form a secure solder joint. The microphone can, in particular, be a microphone that uses an acousto-optical principle. The laser unit can apply a laser pulse to the electronic component to be tested in order to cause the material to vibrate. The sound wave of this sound shock pulse subsequently emitted into the air is then measured.The sound wave oscillations cause a change in air pressure, which in turn influences the wavelength of the light beam in the acousto-optical microphone. The sound wave is transmitted in a very compact interferometer in the sensor head, only approximately 2 mm long. It influences the wavelength and thus changes the brightness of the light beam in the interferometer, which can then be measured. This means that a good quality solder joint emits a different sound wave than a damaged solder joint or an incomplete solder joint. This allows both the first and second properties of the solder joint to be determined. The electronic component, such as a circuit board with an optical element, can therefore preferably be arranged on the circuit board using through-hole contact, so that the circuit board lies on one level.Although the circuit board rests on one level, both the front and back of the solder joint can be inspected using the laser beam.

[0007] The subclaims show preferred developments of the invention.

[0008] Preferably, the testing unit is configured to compare the received sound wave with a plurality of reference sound waves in order to determine one type of the first properties and / or one type of the second properties.

[0009] An advantage of this embodiment is that each sound wave received by the microphone has a very specific signal signature, which can then be used to determine the type of soldered joint by comparing the received sound wave against a database containing a plurality of reference sound waves assigned to known, specific test points. For example, a first sound wave is received by the test unit, and the comparison with the database can determine that the solder joint contains insufficient solder.

[0010] Further preferably, an optical element can be arranged on the circuit board by means of a through-hole mounting, wherein the soldering point is designed to connect the optical element to the circuit board at a through-hole, wherein the first part of the soldering point faces the optical element, wherein the second part of the soldering point faces away from the optical element.

[0011] An advantage of this design is that for a control process to verify successful contact between the optical element and the circuit board, the board does not need to be turned over, since the received sound wave can be used to inspect both the front and back of the solder joint. Another advantage is that even hidden solder joints, for example, those covered by a housing part or similar, can be inspected.

[0012] Preferably, the optical element and the circuit board can be arranged relative to one another based on a predetermined orientation and the optical element can be irradiated by a test beam of the laser unit along a predetermined optical axis, wherein the test unit is configured to determine a delta between a current orientation of the optical element to the circuit board and the predetermined orientation by means of the received test beam.

[0013] An advantage of this embodiment is that if the predetermined orientation is not met by the optical element, this can be easily corrected using the received test beam from the laser unit. Preferably, the optical element and the circuit board are positioned relative to one another before a soldering process connecting them until an resulting optical path of the test beam between at least one lens of the optical element and a detector on the circuit board corresponds to a predetermined detector signal. Preferably, the optical element is fixed relative to a housing in a predetermined position, in particular coaxially to a housing opening receiving the optical element, wherein the circuit board is positioned relative to the optical element in a soldering position that images the predetermined detector signal.During the positioning process, the test unit is configured to repeatedly emit the test beam as a correction signal in order to determine, by means of the measured detector signal, a deviation between the predetermined orientation and the current orientation between the optical element and the circuit board and to minimize it by means of a corresponding positioning movement, in particular until the predetermined detector signal is imaged.

[0014] In this way, rejects during the soldering of the optical element and the circuit board are actively avoided.

[0015] Further preferably, the optical element has at least one pin, wherein the circuit board has an opening, wherein the pin can be arranged in the opening, wherein the soldering point is designed to form a connection between the pin and the opening, which positions the optical element and the circuit board in a fixed position relative to one another.

[0016] An advantage of this design is that a very long service life can be ensured by means of the solder joint and the correct inspection of the front and back of the solder joint.

[0017] Further preferably, the first part of the solder joint is a first meniscus, wherein the second part of the solder joint is a second meniscus.

[0018] An advantage of this embodiment is that the first part is a first meniscus and the second part is a second meniscus and can be determined based on the formation of the menisci or conclusions can be drawn about the quality of the solder joint.

[0019] Preferably, the first property and / or the second property is a distance between a center of the pin and a center of the opening and / or is a degree of wetting with solder of the solder joint.

[0020] An advantage of this embodiment is that if the center of the pin is too far from the center of the opening, it can be concluded that there is not enough solder around the pin. For example, if the pin is too far to the right, there will be too much solder on the right and too little on the left. Furthermore, the degree of solder wetting can be determined, for example, to determine sufficient strength between the optical element and the circuit board.

[0021] Preferably, the inspection unit is configured to inspect a plurality of solder joints by means of the predetermined light beam, wherein the inspection unit is configured to inspect the plurality of solder joints using a predetermined pattern.

[0022] An advantage of this embodiment may be that the laser unit can inspect a plurality of solder joints using a predetermined light beam and / or a plurality of predetermined light beams simultaneously or sequentially. More preferably, only a subset of a plurality of solder joints can be inspected. For example, the predetermined pattern can be configured such that only every 10th solder joint is inspected, or, for example, only one solder joint that is typically prone to deviations.

[0023] Further preferably, the testing unit is configured to adapt the predetermined pattern based on the first property or the second property.

[0024] An advantage of this embodiment is that the testing unit can independently adapt the predetermined test pattern if, for example, the first property and / or the second property lie outside a predetermined deviation range. For example, if a defect or deviation is detected at a solder joint, the testing unit can increase the test frequency.

[0025] A further aspect of the invention relates to a vehicle having a camera comprising an optical element soldered to a circuit board, which is connected to the test unit as described above and below. Short description of the drawings

[0026] Embodiments of the invention are described in detail below with reference to the accompanying drawings. In the drawing: Fig. 1 to 3 a test unit according to an embodiment, Fig. 4 a vehicle according to an embodiment. Embodiments of the invention

[0027] Preferably, all identical component elements and / or units in all figures are provided with the same reference numerals.

[0028] Fig. 1 shows a test unit 10 according to one embodiment. The test unit 10 comprises a laser unit 14 and a microphone 16, in particular an acousto-optical microphone. The test unit 10 is configured to generate a laser beam 60 or a light beam by means of the laser unit 14 in order to irradiate a component comprising a plurality of components 20 of the electronics unit 22. The irradiation mechanically excites the solder joint 12, forming structure-borne sound that propagates through the plurality of components 20. The structure-borne sound is ultimately radiated in the form of a sound wave into the environment of the test unit 10, so that a microphone 16, in particular an acousto-optical microphone, can receive a sound wave 62 that maps the previously mechanical excitation of the solder joint 12.Further preferably, the testing unit 10 is configured to determine at least a first property of the first part 24 on a first side 26 of a circuit board 28 and a second property of the second part 30 on a second side 32 of the circuit board 28 using the received sound wave 62. In this case, the electronics unit 22 can in particular comprise at least one optical element 34. In this case, the optical element 34 can in particular define an optical path 68 such that the arrival of the light rays on the optical element 34 is refracted or guided to a detector 70 on the circuit board 28. Further preferably, the optical element 34, the circuit board 28 and the detector 70 can have a predetermined orientation 36 relative to one another.Further preferably, the test unit 10 is configured to determine a delta between a current orientation 38 of the optical element 34 and the circuit board 28 relative to one another and the predetermined orientation 36 by means of a test beam radiated onto the optical element 34. Further preferably, the test unit 10 can output a signal comprising the delta or an instruction as to how the delta is to be minimized by a relative positional movement of the circuit board 28 and the optical element 34 relative to one another. For example, the electronics unit 22 with the optical element 34 can in particular form part of a camera unit 102. The laser unit 14 can be used to emit the test beam. The aforementioned detector can be used to output the delta.

[0029] Fig. 2a shows a test unit 10 according to one embodiment. The test unit 10 comprises a laser unit 14 and a microphone 16. The laser unit 14 can emit a laser beam or light beam 60 onto a holder 72 of the optical element 34, which has at least one pin 40. The pin 40 can in particular be inserted into an opening 42 of the printed circuit board 28. Thus, the holder 72 can be fastened to the printed circuit board 28 by means of through-hole mounting, in particular by means of the pin 40 through the opening 42. For permanent, stationary positioning, a solder joint 12 is formed between the pin 40 and the opening 42. A detailed view 64 is shown in the Fig. 2b.

[0030] Fig. 2b shows a detailed view 66 of the solder joint 12 according to one embodiment. The solder joint 12 has a first part 24 on a first side 26 of a printed circuit board 28. Furthermore, the solder joint 12 has a second part 30 on a second side 32 of the printed circuit board 28. As shown in FIG. Fig. 2b, the first portion 24 of the solder joint 12 may be a first meniscus of the solder joint 12 and the second portion 30 of the solder joint 12 may be a second meniscus. More preferably, the first property and / or the second property may be a distance between a center point 44 of the pin 40 and a center point 46 of the opening 42 and / or a degree of solder wetting of the solder joint 12. As shown in Fig. 2b, the pin 40 is positioned in an opening 42 by means of through-hole mounting to the circuit board 28. Furthermore, a solder joint 12 is formed between the pin 40 and the opening 42. In this way, the pin 40 can be secured in a fixed position to the circuit board 28. The pin 40 or the optical element 34, to which the pin 40 can be connected, can have a predetermined orientation 36. More preferably, the test unit 10 can determine a delta between a current orientation 38 of the optical element 34 and the circuit board 28 relative to one another by means of a test beam emitted by the laser unit 14 onto the optical element, in particular by evaluating the detector signal, which is determined by a current orientation 38 of the optical element 34 and the circuit board 28 relative to one another. The current orientation 38 can in particular be influenced by the solder joint ordeviate from a predetermined orientation 36, since the optical element 34 may tilt relative to the circuit board 28 due to manufacturing tolerances. Further preferably, the test unit 10 can repeatedly emit the test beam as a correction signal during a positioning process, which is configured to minimize the delta by a relative positioning movement of the optical element 34 and the circuit board 28 to one another, in particular until the predetermined orientation is reached, at which a predetermined detector signal is imaged. The positioning process can comprise the solder joint 12 being softened at least temporarily in order to bring the current orientation 38 closer to the predetermined orientation 36 by means of the aforementioned positioning movement.

[0031] Fig. Figure 3 shows a test unit 10 according to one embodiment. The test unit 10 includes a laser unit 14 and an optical microphone 16.

[0032] Fig. 4 shows a vehicle 100 having a camera unit 102 comprising an optical element soldered to a circuit board 28, which was tested by means of the test unit 10 as described above and below.

Claims

[1] Test unit (10) for checking a solder joint (12), comprising: - a laser unit (14), - an optical microphone (16), wherein the laser unit (14) is configured to irradiate at least one component (18) of a plurality of components (20) of an electronic unit (22) having the solder joint (12) and / or the region of the solder joint with a predetermined light beam, such that the solder joint (12) can be mechanically excited by means of the predetermined light beam, wherein the optical microphone (16) is configured to receive a sound wave that images the excitation of the solder joint (12) in its immediate vicinity, wherein the solder joint (12) has a first part (24) on a first side (26) of a printed circuit board (28), wherein the solder joint (12) has a second part (30) on a second side (32) of the printed circuit board (28), which is remote from the first side (26), wherein the testing unit (16) is configured to determine at least a first property of the first part (24) and a second property of the second part (30) by means of the received sound wave. [2] Testing unit (10) according to claim 1, wherein the testing unit (10) is configured to compare the received sound wave with a plurality of reference sound waves to determine a type of the first property and / or a type of the second property. [3] Test unit (10) according to one of the preceding claims, wherein an optical element (34) can be arranged on the printed circuit board (28) by means of a through-hole mounting, wherein the soldering point (12) is designed to connect the optical element (34) to the printed circuit board (28) at a through-hole location, wherein the first part (24) of the soldering point (12) faces the optical element (34), wherein the second part (30) of the soldering point (12) faces away from the optical element (34). [4] Test unit (10) according to claim 3, wherein the optical element (34) can be arranged on the basis of a predetermined orientation (36) relative to the circuit board (28) and the optical element (34) can be irradiated by a test beam of the laser unit (14) along an optical axis, wherein the test unit (10) is configured to determine a delta between a current orientation (38) of the optical element (34) relative to the circuit board (28) and the predetermined orientation (36) by means of the received test beam. [5] Test unit (10) according to claim 4, wherein the test unit (10) is arranged to repeatedly emit the test beam as a correction signal which is arranged to minimize the delta. [6] Test unit (10) according to one of claims 3-5, wherein the optical element (34) has at least one pin (40), wherein the printed circuit board (28) has an opening (42), wherein the pin (40) can be arranged in the opening (42), wherein the soldering point (12) is designed to form a connection (44) between the pin (40) and the opening (42), which positions the optical element (34) in a fixed position relative to the printed circuit board (28), in particular with the minimum delta. [7] Test unit (10) according to claim 6, wherein the first part (24) of the solder joint (12) is a first meniscus of the solder joint (12), wherein the second part (30) of the solder joint (12) is a second meniscus. [8] Test unit (10) according to one of claims 6-7, wherein the first property and / or the second property is a distance between a center point (44) of the pin (40) to a center point (46) of the opening (42), and / or a degree of wetting with solder of the solder joint (12). [9] Test unit (10) according to one of the preceding claims, wherein the test unit (10) is configured to test a plurality of solder joints (12) by means of the predetermined light beam, wherein the test unit (10) is configured to test the plurality of solder joints (12) using a predetermined pattern. [10] Testing unit (10) according to claim 9, wherein the testing unit (10) is configured to adapt the predetermined pattern based on the first property and / or the second property. [11] Vehicle (100) having a camera unit (102) which has been checked with the checking unit (10) according to one of the preceding claims.

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