Manufacturing machine for a production line for electronic assemblies with a "Depth-From-Defocus" optical inspection system

Abstract

A manufacturing machine (100) for a production line for electronic assemblies is described. The manufacturing machine comprises (a) a chassis (102); (b) a manufacturing tool (119) which is attached directly or indirectly, movable or stationary, to the chassis; and (c) an optical inspection system (220) which is attached directly or indirectly, movable or stationary, to the chassis.The optical inspection system comprises (c1) a lighting device (230) for illuminating an object (295) with illumination light (230a), (c2) a camera system (240) for capturing a first image of the illuminated object using a first measuring light (242a) and a second image of the illuminated object using a second measuring light (244a), (c3) optics (250) arranged in a beam path of the illumination light, the first measuring light, and / or the second measuring light, and (c4) an image processing unit (260) connected downstream of the camera system. The lighting device, the optics, and / or the camera system are configured and arranged such that the first image has a first blur and the second image has a second blur. The image processing unit is configured to determine a three-dimensional height map of at least a part of the object based on the first and second images.

Description

Technical field

[0001] The present invention relates generally to the technical field of automated electronics manufacturing. In particular, the present invention relates to a manufacturing machine with an optical inspection system for capturing and processing images, especially images of solder paste deposits, components and / or component carriers. Background of the invention

[0002] Electronic assemblies with multiple discrete components are typically mounted on component carriers, such as printed circuit boards. In mass electronics manufacturing, this is usually done using dedicated production lines that include a component carrier transport system along which several production machines are arranged. The production machines on an electronics manufacturing line include a solder paste dispenser, typically several placement machines arranged in series, and a soldering machine, all positioned along the transport system.

[0003] In a solder paste printing machine, highly viscous solder paste is applied to a component carrier in the form of individual solder paste deposits. This is usually done using a printing stencil.

[0004] In a placement machine, electronic components are placed onto a component carrier. For this purpose, a placement machine typically has a placement head that (i) picks up the components to be placed from a component pick-up position of a component feeder, (ii) transports the picked-up components to a placement area of ​​the placement machine in which the respective component carrier to be populated is located, and (iii) places the components transferred to the placement area onto the component carrier or the corresponding solder paste deposits at a predetermined component placement position. To pick up the components, a typical placement head uses one or more component holding devices, which are, for example, designed as vacuum suction grippers.

[0005] In a soldering machine, the solder paste deposits are melted, so that after cooling, the assembled components are permanently and electrically conductively soldered to the electrical component connection surfaces formed on the component carrier.

[0006] To ensure a reliable soldering process, each solder paste reservoir must contain a predetermined amount of solder paste. If a reservoir contains too little solder paste, the resulting solder joint may be mechanically unstable and / or, in particular, electrically insufficiently conductive. Conversely, if a reservoir contains too much solder paste, short circuits may occur between adjacent component pads during melting in the soldering machine.

[0007] DE 10 2013 216 196 A1 discloses an image processing system for capturing the three-dimensional (3D) structure of a solder paste deposit applied to a component carrier. According to the principle of "photometric stereo", such a deposit is illuminated from three different angles and an image is captured in each case, with each image exhibiting individual intensity distributions that depend on the 3D shape of the deposit.

[0008] A combined image analysis of the three images makes it possible to determine the 3D structure of the respective solder paste deposit and thus also its volume or its amount of solder paste.

[0009] To ensure reliable and precise component placement, it is necessary to optically capture a component held by a component holder using a camera and to determine the exact spatial position of the held component relative to (a tip of) the component holder using suitable image processing. Any deviations from a relative target position can then be detected and compensated for during the placement process by appropriately positioning the placement head and / or rotating the component holder around its longitudinal axis. Furthermore, it can be determined whether a component is held correctly on a main surface or incorrectly on a smaller side surface by the component holder (so-called vertical orientation). It can also be detected if a component is held in an inclined or tilted spatial orientation.Furthermore, it is also possible to detect if the held component has a mechanical defect. Components held in an incorrect orientation or that are defective must not be processed further and must generally be removed from the placement process.

[0010] For reliable and accurate component placement, it is also necessary to determine the precise position of each component tray to be populated. Only then can it be ensured that the components are placed exactly at their designated placement location on the component tray. The position of a component tray is typically determined by optical measurement of at least one marking present on the tray.

[0011] For the aforementioned optical inspection processes of solder paste deposits, components, and component carriers, it is desirable and essential for a fast, accurate, and reliable manufacturing process to acquire not only two-dimensional (2D) images but also three-dimensional (3D) images. In this document, 3D images are also referred to as height maps, and the corresponding spatial 3D structures are called height features.

[0012] In the field of assembly technology, various technologies are known for optical 3D inspections. For example, DE 10 2018 102 288 A1 discloses a method and a device for determining the orientation of a component with curved terminal contacts held by a component holding device based on characteristic optical reflections. The characteristic optical reflections arise when illumination light strikes the different sections of a curved terminal contact at an oblique angle.

[0013] DE 10 2016 122 494 A1 discloses a placement machine comprising an image processing system configured to inspect the placement of electronic components for an electronic assembly at least partially assembled on a component carrier. This inspection utilizes a three-dimensional reference height profile of the electronic components assigned to a reference assembly. A three-dimensional height profile of the components in the placement is captured and compared to the reference height profile. If at least a portion of the height profile deviates from the corresponding portion of the reference height profile, the placement is identified as defective. Otherwise, the placement is identified as free of defects.

[0014] DE 10 2022 108 474 A1 discloses a method for measuring the surface profile of an object, in which a measuring camera captures two images of the object. The measuring camera has an image sensor and a lens that is telecentric at least on the object side, comprising a first optical subsystem, a second optical subsystem, and a pupil plane arranged between them. Only light illuminating a first region of the pupil plane contributes to the first image. Only light illuminating a different second region of the pupil plane contributes to the second image. At least one of the two regions is not point-symmetric with respect to an optical axis of the lens. Subsequently, the surface profile is calculated from a lateral offset between structures in the first image and corresponding structures in the second image.

[0015] DE 10 2024 109 226 A1 discloses a method for capturing a composite microscope image of a sample. The storage process comprises (a) capturing a first image, wherein the sample is illuminated in a structured manner, (b) capturing a second image, wherein the sample is illuminated uniformly, and (c) fusing the first image and the second image, wherein the first image is used for low-frequency image information located in focus and the second image is used for high-frequency image information located in focus.

[0016] The invention is based on the objective of implementing a simple yet reliable 3D inspection (i) of solder paste deposits and (ii) of components to be assembled and / or already assembled in a production line for electronic assemblies. Summary of the invention

[0017] This problem is solved by the subject matter of the independent claims. Advantageous embodiments of the present invention are described in the dependent claims.

[0018] According to a first aspect of the invention, a manufacturing machine for a production line for electronic assemblies is described. The manufacturing machine comprises (a) a chassis; (b) a manufacturing tool which is attached directly or indirectly, movable or stationary, to the chassis; and (c) an optical inspection system which is attached directly or indirectly, movable or stationary, to the chassis.The optical inspection system comprises (c1) a lighting device for illuminating an object with illumination light, (c2) a camera system for capturing (i) a (two-dimensional) first image of the illuminated object using a first measuring light and (ii) a (two-dimensional) second image of the illuminated object using a second measuring light, (c3) optics arranged in a beam path of the illumination light, the first measuring light and / or the second measuring light, and (c4) an image processing unit connected downstream of the camera system. The lighting device, the optics and / or the camera system are configured and arranged such that the first image has a first blur and the second image has a second blur, which is different from the first blur.Furthermore, the image processing unit is set up to determine a three-dimensional (3D) height map of at least part of the object based on the first image and the second image.

[0019] The described manufacturing machine is based on the understanding that, using the already known “Depth-From-Defocus” technology in its own right, particularly good optical inspection results can be achieved in a simple and effective way in the technical field of electronics manufacturing, and especially in or on a manufacturing machine of a production line for manufacturing electronic assemblies.

[0020] In simpler terms, the "Depth-From-Defocus" technology described here, used in the manufacturing of electronic assemblies, constructs a 3D height map from two images taken at different Z-distances. By appropriately selecting the focus settings for the two images, each object pixel exhibits a characteristic blur in both images, reflecting its individual distance from the respective focal plane. The height position of each individual object pixel can then be calculated from these characteristic blurs.

[0021] The "Depth-From-Defocus" technology can be implemented in various ways, as detailed below. However, all the embodiments described below share the common feature that the respective "Depth-From-Defocus" optical inspection system can be built in a simple and, in particular, compact manner. This allows the described optical inspection system to be used even in very confined areas of the described manufacturing machine.

[0022] Furthermore, the described optical inspection system can be implemented with no moving components or with only a few mechanically moving ones. This allows for simple manufacturing and results in high mechanical robustness of the inspection system. Moreover, it is not necessary to move the object between capturing the first and second images. This means that the two images, which may have different levels of sharpness, can be captured within a very short timeframe and sometimes even simultaneously. Compared to known 3D methods, this accelerates the optical 3D inspection process, resulting in a time advantage that is particularly beneficial in electronics manufacturing due to the cost pressures prevalent there.

[0023] Furthermore, an accurate image reconstruction of the object in focus can be calculated from the two images individually. This is because, unlike image reconstruction using only one image, artifacts can be eliminated. Compared to simple and still frequently used 2D scanning methods, this improves the accuracy and robustness of detecting marks, patterns, and barcodes, especially when the object in question is not exactly in focus.

[0024] The described object can be any object that needs to be optically captured in 3D during the manufacturing of electronic assemblies. In particular, as already indicated above, the object can be a solder paste deposit, a component, or a marking formed on a component carrier.

[0025] The manufacturing tool in question can be any type of tool configured to perform, or at least participate in, at least one manufacturing step in the production of an electronic assembly mounted on a component carrier. Examples of manufacturing tools include placement heads on a pick-and-place machine, squeegee devices on a solder paste printing machine, etc.

[0026] The aforementioned image processing unit can be installed or attached to an unspecified housing of the optical inspection system. Alternatively, the image processing unit can also be integrated as a processor within a larger computing unit. Such a larger computing unit could, for example, be a central control computer that controls and / or coordinates at least part of the operation of the production machine. Furthermore, the image processing unit can also be implemented in a non-physical form, such as software, and / or in a hybrid form through a combination of software and hardware components.

[0027] According to one embodiment of the invention, there is no spatial overlap between a first depth of field area of ​​the optical imaging of the first image, which is associated with the first blur, and a second depth of field area of ​​the optical imaging of the second image, which is associated with the second blur.

[0028] The described spatial difference between the two depth-of-field areas can lead to the determination of accurate 3D height maps even for a comparatively tall object, where at least some of the object points have a comparatively large height difference to each other.

[0029] According to a further embodiment of the invention, a first focal plane, which corresponds to the first image, lies in front of an object plane of the object along a propagation direction of the illumination light. A second focal plane, which corresponds to the second image, lies behind the object plane of the object. This means, intuitively, that the two focal planes are located on opposite sides with respect to the object, or more precisely, with respect to an object plane of the optical inspection system. In other words, the object is located between the two focal planes.

[0030] The described spatial arrangement of the object plane in relation to the two focal planes means that determining the 3D height map involves interpolation between the first image information of the first image and the second image information of the second image. Such interpolation advantageously allows for a particularly accurate and, in particular, error-resistant determination of the 3D height map.

[0031] According to a further embodiment of the invention, either the first blur or the second blur is at least approximately zero. This means that the first focal plane associated with the first image, or alternatively the second focal plane associated with the second image, coincides at least approximately with the object plane. In other words, one of the two images is a sharp image. This has the advantage that, in addition to the determined 3D height map, a two-dimensional (2D) image is automatically available when the sharp image is captured. In the described optical inspection, the 2D image information of the sharp 2D image can then be combined with the 3D height map information of the determined 3D height map. This allows features of the object to be optically detected that could not be detected with a 3D inspection without the use of the 2D image information.

[0032] The combined evaluation of 3D elevation map information and 2D image information described here can be used, for example, to reliably detect labels that are normally barely visible due to low contrast and / or labels on a reflective surface.

[0033] In this context, it should be noted that the additional acquisition of the 2D image can be performed without any time delay. A third image acquisition beyond the two required for determining the 3D height map is not necessary.

[0034] According to a further embodiment of the invention, the illumination light strikes the object along a z-axis and the first measuring light and the second measuring light leave the object along this z-axis (in the opposite direction).

[0035] The first and second measuring lights are created when the illumination light is at least partially reflected or scattered at the object's surface. Immediately after this reflection or scattering, the first and second measuring lights may be indistinguishable. Only further along their path can the optical path of the two "measuring lights" split into two spatially separate path segments, so that the first image is captured on the first path segment and the second image on the second path segment.

[0036] The coaxial propagation of illumination and measurement light described here, implemented along a defined z-direction or z-axis, has the significant advantage that the three-dimensional height map can be created without shadowing. This is true at least when the z-direction is vertical with respect to an object plane.

[0037] With other 3D inspection methods (such as triangulation or photometric stereo), shadowing areas caused by interfering object edges can always occur due to differing angles of illumination and measurement light. In such shadowed areas, a 3D height map cannot be calculated accurately, or at all. In contrast, with the "Depth-From-Defocus" technology described in this embodiment, both images are captured "frontally," and the object is preferably illuminated frontally as well. This allows for the calculation of an accurate, shadow-free height map even in areas with high object edges, so that, for example, a small component near a tall component is fully visible in the defined height map. For a particularly high-quality height map, a telecentric camera system or a camera system with telecentric optics can be used on the object side.

[0038] According to a further embodiment of the invention, the optical inspection system comprises a first beam splitter which spatially separates a part of an illumination path of the illumination light from a part of a measurement path of the measurement light.

[0039] The first beam splitter can be a semi- or partially optically transparent mirror or a beam splitter cube. Preferably, the illumination light is reflected by the first beam splitter, and the measuring light passes through the first beam splitter, possibly with a slight parallel offset caused by refraction within the first beam splitter.

[0040] According to a further embodiment of the invention, at least one further illumination light for the object is coupled in via a reflection at the first beam splitter, wherein the further illumination light illuminates the object at a different angle than the illumination light.

[0041] As described above, in this embodiment, the illumination light is directed vertically from above along a z-direction that is perpendicular to the plane in which the object is located. The additional illumination light therefore strikes the object at an oblique angle. Depending on the oblique angle of this other angle, shadowing in this embodiment can only occur with the additional illumination light. Shadowing is not a concern with either the illumination light or the measuring light, since these strike the object and exit the object along the z-direction.

[0042] This document specifies the directions or angles of the various lighting sources in relation to the z-direction. This means that the primary lighting source is a so-called 0° illumination. The other lighting sources can, for example, strike the object at an angle of at least approximately 30°, 60°, 70°, or 80°.

[0043] Preferably, in addition to a first additional light source, there is a second additional light source, possibly a third, or even a fourth. Depending on the number of additional lights, the respective lighting angles can be any selection from the aforementioned angles of at least approximately 30°, 60°, 70°, or 80°.

[0044] Additional oblique lighting, comprising at least one further light source, can advantageously enable a particularly accurate determination of the 3D height map. This is especially true for objects with an "optically problematic surface," such as a glossy surface or a surface with optically matte structural features on a matte surface.

[0045] According to a further embodiment of the invention, the illumination light and the additional illumination light have different light colors.

[0046] By appropriately combining light colors or spectral distributions of different illumination sources, robust inspection results can be achieved, depending on the specific optical conditions. These optical conditions can be determined, in particular, by the optical properties of the object's surface, such as its color and reflectivity (glossy or matte). The same applies to any markings visible (in a 2D image), especially if these markings have low contrast compared to the rest of the object's surface.

[0047] According to a further embodiment of the invention, the optics are at least approximately free from chromatic aberration.

[0048] Without chromatic aberration (the imaging optics include, for example, achromatic lenses), it can be advantageously ensured that each object point is imaged onto a corresponding image point with a small circle of confusion. This is particularly relevant for illumination scenarios with different illumination colors and is especially important when an object point is relatively far from the focal plane for the measuring light.

[0049] According to another embodiment of the invention, the optics are telecentric.

[0050] The telecentric optics can be configured to exhibit object-side and / or image-side telecentricity. In particular, with image-side telecentric imaging optics, the object points are positioned identically in both images. The image scale remains unchanged even when an object point is presented at a different z-distance (distance to the focal plane of the camera system on the object side). This advantageously ensures that the distance between a high and a low object feature is constant across all z-distances. Therefore, shadowing of small components near high object edges is prevented, as only perpendicular measurement light rays contribute to the image formation.

[0051] According to a further embodiment of the invention, the camera system is configured to capture a (two-dimensional) third image of the illuminated object using a third measuring light, wherein the illumination device, the optics and / or the camera system are configured and arranged such that the third image has a third blur which is different from both the first blur and the second blur, and wherein the image processing unit is configured to further determine the three-dimensional (3D) height map based on the third image.

[0052] By considering more than two images taken from different distances, more optical information can be incorporated into the determination or calculation of the elevation map. This not only improves inspection accuracy but also, in particular, extends the height measurement range through additional image acquisition. However, since the information processing of two images by the image processing unit is sufficient for many applications, this document primarily describes the determination of 3D elevation maps from just two images. All statements made here apply analogously to multiple image acquisitions from different focus distances.

[0053] According to a further embodiment of the invention, the manufacturing machine is a placement machine. Furthermore, the manufacturing tool is a placement head configured for (i) picking up electronic components from a component pick-up position of a component feeder, (ii) transporting the picked-up components to a placement area of ​​the placement machine in which a component carrier to be populated is located, and (iii) placing the components transferred to the placement area at a predetermined component mounting position on the component carrier.

[0054] The described production machine, designed as a placement machine, is based on the understanding that the "Depth-From-Defocus" technology described above can be applied particularly advantageously and profitably in the field of placement technology.

[0055] This allows for particularly reliable detection of tilted components. Specifically, an (undesired) tilt angle relative to the longitudinal axis of a component holding device, such as a suction gripper, can be detected. This tilt angle can be precisely determined from the difference in height between two different edges of the component. If this tilt angle exceeds a certain tolerance value, the tilted component should be removed from the placement process to prevent incorrect placement.

[0056] Furthermore, inverted components with bent contact points (so-called gullwing components) can also be identified accurately and reliably. This helps prevent incorrect placement. Additionally, a wear test can be performed on the tip of a component holding device, particularly the front face of a suction gripper. Such a wear test can be used to replace a defective or worn component holding device in a timely manner.

[0057] According to a further embodiment of the invention, the camera system is fixed in space, either directly or indirectly, to the placement head. This has the advantage that movement of the placement head automatically moves the "Depth-From-Defocus" camera system as well. This allows, for example, component carriers to be inspected across their entire surface or at various positions on the carrier, without requiring a separate positioning system for the camera system.

[0058] Furthermore, with a suitable placement machine architecture, components to be placed can be optically inspected in 3D with high accuracy even before being picked up by the placement head or a component holding device of the placement head. The volume and / or shape of a solder paste deposit at the placement point can also be determined before the placement head places a component. In addition, at least part of the assembly can be optically inspected in 3D after placement. In this context, an assembly refers to the entirety of several already placed electronic components.

[0059] According to a further embodiment of the invention, the camera system is fixed in space, either directly or indirectly, to the chassis. This allows components picked up on the placement head or on a component holding device of the placement head to be reliably inspected in 3D using the "Depth-From-Defocus" technology described in this document.

[0060] According to a further embodiment of the invention, the manufacturing machine is a solder paste printing machine. The described manufacturing machine, designed as a solder paste printing machine, is based on the understanding that the "Depth-From-Defocus" technology described above can be applied particularly advantageously and profitably in connection with printing on printed circuit boards or component carriers. In this way, the volume and / or 3D shape of solder paste deposits, which are printed in a known manner using a printing process, in particular a screen printing process, can be examined with regard to the quality of the applied solder paste even before the component carrier is provided, and a component carrier with defective solder paste printing can be prevented from being subjected to a placement process in the first place.

[0061] According to a further embodiment of the invention, the camera system comprises (a) a first image sensor for capturing the first image and (b) a second image sensor for capturing the second image, wherein the two image sensors are fixed in space relative to the optics and / or relative to the illumination device. This has the advantage that no moving components of the optical inspection system are required to capture the two images and the images can be captured simultaneously without any further loss of time.

[0062] The different levels of blur in the two images can be easily achieved by positioning the two image sensors, which could be conventional CCD or CMOS camera chips, at different distances from the lens. In simpler terms, the two image sensors are at different focal distances relative to the object.

[0063] According to a further embodiment of the invention, the optical inspection system further comprises a second beam splitter which spatially separates a part of a first measuring light path of the first measuring light from a part of a second measuring light path of the second measuring light.

[0064] In this context, the spatial separation can be understood as follows: the two measuring lights, i.e., the first measuring light and the second measuring light, initially leave the object along a common measuring light path (the propagation direction of the two measuring lights in the common measuring light path is preferably antiparallel to the direction of at least part of the illumination light incident on the object). The second beam splitter then splits the common measuring light path into the two aforementioned measuring light paths, namely the first measuring light path and the second measuring light path.

[0065] The second beam splitter can also be a semi- or partially optically transparent mirror or a beam splitter cube. Preferably, one of the two measuring lights is reflected by the second beam splitter, and the other of the two measuring lights passes through the first beam splitter, possibly with a slight parallel offset caused by refraction in the first beam splitter.

[0066] The use of the second beam splitter allows for a particularly simple and advantageous solution, eliminating the need for any mechanically moving components in the optical inspection system. This enables the optical inspection system to exhibit high mechanical robustness and / or high thermal stability, ensuring reliable creation of an accurate 3D height map. Furthermore, the second beam splitter allows for simultaneous image acquisition of both images, resulting in exceptionally fast 3D height map generation.

[0067] According to a further embodiment of the invention, the first image sensor is a transparent image sensor which detects the first measuring light and through which the second measuring light penetrates in order to be detected by the second image sensor.

[0068] To put it simply, the first image sensor, with the first measuring light, captures a portion of the total measuring light scattered back from the object and allows the remaining second measuring light to pass through so that it can reach the second image sensor. This means that, along the propagation direction of the measuring lights, the first measuring light, as a portion of the total measuring light, is stopped by the first image sensor.

[0069] The transparent image sensor advantageously eliminates the need for the additional component "second beam splitter" described above, yet allows both images to be captured simultaneously.

[0070] According to a further embodiment of the invention, the camera system has only a single image sensor, which can be spatially positioned with respect to an object plane and / or with respect to the optics, so that in a first position of the single image sensor the first image can be recorded and in a second position of the single image sensor that differs from this the second image can be recorded.

[0071] The described mobility or movableness of the image sensor has the advantage from an equipment point of view that only a single image sensor is required to capture the two images, and the optical inspection system can thus be implemented in a simple and, in particular, cost-effective way.

[0072] Regardless of how the spatial positioning of the single image sensor is implemented, a corresponding “Depth-From-Defocus” measurement sequence (with two image acquisitions) can be implemented as follows: 1. Positioning the single image sensor at a first position Z1. 2. Taking the first picture. 3. Positioning the single image sensor at a second position Z2. 4. Taking the second picture.

[0073] The result is two images, from whose relative blurriness of the object pixels contained therein a 3D height map can be determined.

[0074] According to a further embodiment of the invention, the camera system comprises only a single image sensor, which is fixed in space with respect to an object plane and / or with respect to the optics. Furthermore, the optics are focus-adaptive optics, such that (i) in a first state with a first focus, the first image can be captured by the single image sensor, and (ii) in a second state with a second focus, the second image can be captured by the single image sensor.

[0075] The use of adaptive optics has the advantage that the number of components of the optical inspection system can be kept low, so that the “Depth-From-Defocus” technology can be integrated into the described manufacturing machine in a simple and cost-effective way.

[0076] Adaptive optics can, in principle, be any optically refractive and / or diffractive component capable of changing the focal distance. A liquid lens or a motorized lens are mentioned here merely as examples. A liquid lens, aside from being spatially compact and mechanically stable, has the advantage of allowing the focal plane to be shifted particularly quickly, for example, within 10 milliseconds. In particular, by changing the aperture of the adaptive optics, the sharpness of the images can be altered to obtain two images with different levels of blur. The change in aperture does not necessarily have to involve changing the diameter of a circular aperture. A change in aperture can also be achieved through any spatially dependent transmission within a predefined aperture range.

[0077] Regardless of how the adaptive optics are implemented, a “Depth-From-Defocus” measurement sequence (with two image acquisitions) can be implemented as follows: 1. Adjusting the adaptive optics so that a focal plane is located at a first position Z1. 2. Taking the first picture. 3. Adjusting the adaptive optics so that one focal plane is located at a second position Z2. 4. Taking the second picture.

[0078] The result is two images, from whose relative blurriness of the object pixels contained therein a 3D height map can again be determined.

[0079] According to a further embodiment of the invention, the optics exhibit chromatic aberration, and the illumination light has at least a first illumination color and a second illumination color. Furthermore, the first measuring light is assigned to the first illumination color, and the second measuring light is assigned to the second illumination color.

[0080] This embodiment, which utilizes the physical optical property of chromatic aberration, has the advantage that, on the one hand, no spatially moving components are required to implement the optical inspection system, and on the other hand, the number of optical components can be kept small. This ensures high robustness and high thermal stability of the optical inspection system.

[0081] In this context, "assignment" means that the first image is primarily captured with the first lighting color, and the second image is primarily captured with the second lighting color. A certain degree of "color mixing" is not excluded.

[0082] According to a further embodiment of the invention, (i) the first image is captured in a first operating state of the optical inspection system in which the object is illuminated with the first illumination color and (ii) the second image is captured in a second operating state of the optical inspection system in which the object is illuminated with the second illumination color.

[0083] In simpler terms, this embodiment, which is particularly easy to implement with regard to the camera system, involves a temporal separation of the two image acquisitions. Specifically, this means that the first image is captured with the first illumination color, and then the second image is captured with the second illumination color. This results in two images, and a 3D height map can be calculated from their relative sharpness using "Depth-From-Defocus" technology.

[0084] According to a further embodiment of the invention, the camera system comprises a spectrally resolving image sensor configured to extract the first and second images from a single image of the illuminated object, captured with both the first and second illumination colors. This embodiment has the advantage over the embodiment described above, which is also based on the effect of chromatic aberration, that only a single image acquisition is necessary. This advantage is achieved (at a comparatively low cost nowadays) by requiring the image sensor to have at least a certain spectral resolution.

[0085] The spectral resolution of the image sensor can be achieved, for example, by making the pixels on the image sensor color-sensitive. For instance, the first sensor pixels can preferably detect the first illumination color, and the second sensor pixels can preferably detect the second illumination color.

[0086] Further advantages and features of the present invention will become apparent from the following exemplary description of currently preferred embodiments. Brief description of the drawing Fig. Figure 1 shows a manufacturing machine according to an embodiment of the invention. Fig. Figure 2 shows an optical inspection system with a camera system comprising a first image sensor and a second image sensor arranged at different distances from a beam splitter, wherein the beam splitter divides a common measuring light into a first measuring light assigned to the first image sensor and a second measuring light assigned to the second image sensor. Fig. Figure 3 shows an optical inspection system with a camera system which has a single image sensor that is movable relative to an optic. Fig. Figure 4 shows an optical inspection system with a camera system which has a first image sensor and a second image sensor arranged one behind the other in a common measuring light beam path, wherein the second image sensor is a partially transparent image sensor. Fig. Figure 5 shows an optical inspection system with a camera system which has a single stationary image sensor and adaptive optics. Detailed description

[0087] It should be noted that in the following detailed description, features or components of different embodiments that are identical or at least functionally equivalent to the corresponding features or components of another embodiment are designated with the same reference numerals or with reference numerals whose last two digits are identical to the reference numerals of corresponding identical or at least functionally equivalent features or components. To avoid unnecessary repetition, features or components already explained with reference to a previously described embodiment will not be explained in detail again later.

[0088] Furthermore, it should be noted that the embodiments described below represent only a limited selection of possible embodiments of the invention. In particular, it is possible to combine the features of individual embodiments in a suitable manner, so that a multitude of different embodiments are to be considered obviously disclosed to the person skilled in the art with the embodiments explicitly presented here.

[0089] Furthermore, it should be noted that spatial terms, such as "front" and "back," "top" and "bottom," "left" and "right," etc., are used to describe the relationship of one element to another, as illustrated in the figures. Accordingly, these spatial terms may apply to orientations that differ from those depicted in the figures. However, it goes without saying that, for the sake of simplicity, all such spatial terms refer to the orientations shown in the drawings and are not necessarily restrictive, since the device, component, etc., depicted, when in use, may assume orientations that differ from those shown in the drawing.

[0090] Fig. Figure 1 shows a schematic representation of a production machine 100 designed as a placement machine for placing electronic components 192 onto component carriers or printed circuit boards 190. The production machine 100 has a chassis 102 as its stationary support structure. A stationary support rail 104 is attached to the chassis 102 and extends along the y-direction. A support arm 106 is attached to the stationary support rail 104 and extends along the x-direction. This arm can be moved along the y-direction by means of a drive motor (not shown). The corresponding direction of travel is indicated by a double arrow "Y". A mounting element 108 is attached to the support arm 106 and can be moved along the x-direction by means of another drive motor (also not shown). The corresponding direction of travel is indicated by a double arrow "X".The components carrier rail 104, support arm 106 and mounting element 108 together with the two drive motors not shown constitute a so-called surface positioning system with which a manufacturing tool 130 designed as a placement head can be positioned within an xy-plane.

[0091] The component carriers 190 are assembled in an assembly area 110. Before assembly, the component carrier 190 to be assembled is transported to the assembly area 110 by means of a transport device 112, for example, a conveyor belt. After at least partial assembly with components 192, the component carrier 190 is transported away by means of the transport device 112. The corresponding transport directions are shown in Fig. 1 each marked with an arrow T.

[0092] As from Fig. As can be seen in Figure 1, the placement head 130 is attached to the mounting element 108. By appropriately controlling the drive motors (not shown), the placement head 130 can be moved between component pick-up positions 116 of a component feeding system 114 and the placement area 110. A control unit 118, which is communicatively coupled to the placement head 130 via the data line 118a (shown with dashed lines) and the drive motors (not shown), ensures a smooth placement process in a known manner. The placement head 130 is moved to the component pick-up positions 116, where components 192 are picked up. Subsequently, the placement head 130, together with the picked-up components 192, is moved to the placement area 110, where the components 192 are placed onto the provided component carrier 190.Afterwards, the placement head 130 is moved “empty” back to the component feeding system 114, where components 192 are picked up again.

[0093] As from Fig. As can be seen in Figure 1, the placement machine 100 has two optical inspection systems, a first optical inspection system 120a and a second optical inspection system 120b. However, it should be noted at this point that production machines according to the invention may also have only a single optical inspection system.

[0094] The first optical inspection system 120a is stationary, i.e., fixed in place, on the chassis 102 and, according to the embodiment shown here, serves to perform a 3D measurement of the components 192 picked up by the placement head. For this purpose, the placement head 130 is positioned above the optical inspection system 120a so that the picked-up components 192 enter the detection range of the optical inspection system 120a. This 3D component measurement can, for example, reliably detect whether the components are damaged. Furthermore, it can detect, for example, whether the picked-up electronic components 192 were picked up at an angle by the respective component holding device, which would lead to incorrect placement of the respective component 192. In addition, the exact angular position of a picked-up component 192 can be measured.When the relevant component 192 is placed on the component carrier 190, a deviation in the angular position can be compensated for in a suitable manner by a suitable rotation of a corresponding component holding device, so that the relevant component 192 is placed on the component carrier 190 in a correct angular position.

[0095] According to the embodiment shown here, the second optical inspection system 120b serves to precisely measure markings that are attached to the top surface of the component carrier 190 to be populated. This allows the exact spatial position of the component carrier 190 within the placement area 110 to be determined and taken into account when positioning the placement head 130, ensuring that the components 192 are actually placed precisely at their respective target positions on the component carrier 190. According to the embodiment shown here, the second optical inspection system 120b is attached to the placement head 130 and is moved together with the placement head 130 to measure the markings on the component carrier 190.

[0096] The second optical inspection system 120b can also be used to particularly advantageous effect to measure the so-called component contents, i.e., the assembled components, in 3D after at least partial assembly. This allows any assembly errors to be detected and, if necessary, the affected, at least partially assembled component carrier 190 to be excluded from further processing. Furthermore, the solder pads on which the component leads 192 are placed can also be measured in 3D before the components 192 are assembled. This allows verification that the shape and / or volume of the solder pads is within a prescribed tolerance range.

[0097] Fig. Figure 2 shows an optical inspection system 220 according to a first embodiment of the invention. The inspection system 220 has a lighting device 230 which directs an illumination light 230a onto an object 295 to be inspected. An illumination path of the illumination light 230a runs in reflection across a first beam splitter 262. The lighting device 230 and the first beam splitter 262 are arranged and configured such that the illumination light 230a strikes the object 295 frontally from above.

[0098] As explained above, object 295 can be any preferably three-dimensional spatial physical structure that is to be measured in 3D in the field of electronics manufacturing and, in particular, in the field of assembly technology. This includes, for example, electronic components yet to be placed, electronic components already placed, solder paste deposits, and markings on component carriers to be placed.

[0099] The optical inspection system 220 further comprises a camera system 240, which captures the object 250 from above via an optic 250 and the first beam splitter 262. The camera system 240 has two image sensors: a first image sensor 242 and a second image sensor 244. Above the optic 250 is a second beam splitter 264, which splits a common measuring light 242c, emitted upwards along a common measuring path from the object 295 through the optic 250, into two beams. In this document, these partial beams are referred to as the first measuring light 242a and the second measuring light 244a. The first measuring light 242a propagates along a first optical measuring path that extends (in transmission) from the second beam splitter 264 to the first image sensor 242.In a corresponding manner, the second measuring light 244a propagates (in reflection) along a second optical measuring path, which extends from the second beam splitter 264 to the second image sensor 244.

[0100] The two image sensors 242, 244 are spaced at different distances from the second beam splitter 264. The corresponding distances are shown in Fig. 2 labelled “Z1” and “Z2”.

[0101] According to the embodiment shown here, the optic 250 is a refractive optic with a fixed focus (distance). The optic 250 has several lenses 252, wherein in Fig. 2 Two lenses 252 are shown as examples.

[0102] The optic 250 is preferably a telecentric imaging optic. With regard to the "Depth-From-Defocus" principle described here, a telecentric imaging optic offers the particular advantage of constant magnification. This magnification remains independent of the distance between the object 295 and the imaging optic 250. This means that the image of the object 295 (on the two image sensors 242, 244) retains the same size, even if the object 295 is slightly displaced. The same applies if the object 295 has a three-dimensional structure with a comparatively large height. Furthermore, no perspective distortions occur in a telecentric optic, since the optical axis of the telecentric optic always remains parallel to the light rays. Objects therefore appear the same size from every viewing angle and do not appear smaller when they are further away from the camera system 240.Since telecentric optics do not cause distortion, the edges of a 3D object can be recognized better and more accurately, which facilitates 3D image processing and makes it particularly robust.

[0103] The focus (distance) of the optics 250 is chosen such that (i) a first focal plane F1, which is assigned to the first image sensor 242, is in Fig. 2 above the object 295, and that (ii) a second focal plane F2, which is assigned to the second image sensor 244, is located in Fig. 2 lies below object 295. This results in a blurred image of object 295 being generated on each of the two image sensors 242 and 244. These two images are processed by an image processing unit 260, which calculates a 3D height map of object 295 by means of "optical interpolation" based on the first image information of the first image and the second image information of the second image.

[0104] According to the embodiment shown here, the optical inspection system 220 further comprises an (optional) additional lighting device 232, which illuminates the object 295 along a further lighting path with a further illumination light 232a at an oblique angle. According to the embodiment shown here, the further illumination light 232a has a different color temperature compared to the illumination light 230a. As already explained above, robust inspection results can be achieved by a suitable combination of illumination light colors, depending on the respective optical conditions. The optical conditions can be determined in particular by the optical properties of the object's surface, such as its color and reflectivity (glossy or matte).

[0105] Fig. Figure 3 shows an optical inspection system 320 according to a further embodiment of the invention. The inspection system 320 differs from the optical inspection system 220 in that Fig. 2 only in that (i) there is no second beam splitter and (ii) a different camera system 340 is used. As from Fig. As can be seen in Figure 3, the camera system 340 has only a single image sensor 342. To nevertheless produce two images of the object 295 with different levels of focus, the single image sensor 342 is movable relative to the optic 250. This movableness is shown in Fig. 3 indicated by a dashed vertical double arrow.

[0106] When the single image sensor 342 is in an upper position, it is located at a distance Z1 from the optics 250. Here, the first blurred image of the object 295 can be acquired using a first measuring light 342a along a comparatively long first measuring path. When the single image sensor 342 is in a lower position (here, the single image sensor 342 is shown with a dotted line), it is located at a distance Z2 from the optics 250. Here, the second blurred image of the object 295 can be acquired using a second measuring light 344a along a comparatively short second measuring path.

[0107] Fig. Figure 4 shows an optical inspection system 420 according to a further embodiment of the invention. The inspection system 420 differs from the optical inspection system 320 in that Fig. 3 merely in that in a camera system 440, instead of a single movable image sensor along a straight optical measurement path, two image sensors are optically connected one behind the other. A first image sensor at the end of the straight optical measurement path is in Fig. 4 is designated with reference numeral 442. The second image sensor, designated with reference numeral 444, is a partially transparent image sensor. This means that the common measuring light 246, which is in Fig. When the light from the first sensor 442 strikes the second transparent image sensor 444 from below, it is only partially captured by this sensor. Specifically, part of the common measuring light 246, in the form of a second measuring light 442a, is used by the second transparent image sensor 444 to generate the (blurred) second image. The other part of the common measuring light 246, in the form of a second measuring light 442a, passes through the second transparent image sensor 444 and is used by the first image sensor 442 to generate the (blurred) first image.

[0108] Fig. Figure 5 shows an optical inspection system 520 according to a further embodiment of the invention. The inspection system 520 differs from the optical inspection system 420 in that Fig.4 in that a camera system 540 (again) has only a single image sensor 542 onto which all the measuring light 246 falls. In order to nevertheless be able to generate two blurred images with a single (stationary) image sensor, which are transmitted for the calculation of a 3D height map of the object 295 based on the "Depth-From-Defocus" technology, the optical inspection system 520 has an adaptive optic 550 (with variable focus) instead of an optic with fixed focus. With a first focus setting of the adaptive optic, the (blurred) first image can be taken and with a second focus setting of the adaptive optic, the (blurred) second image can be taken.

[0109] It is noted that the term "have" does not exclude other elements and that "a" does not exclude a plurality. Elements described in connection with different embodiments may also be combined. It should also be noted that reference numerals in the claims should not be interpreted as limiting the scope of protection of the claims. REFERENCE MARK: 100 Production machine / Placement machine 102 chassis 104 stationary support rail 106 movable support arm 108 movable mounting element 110 Assembly area 112 Transport device 114 Component feeding system 115 Component feeding devices 116 component pickup locations 118 Control unit 118a Data line 119 Manufacturing tool / Placement head 120a Optical inspection system for components (stationary) 120b Optical inspection system for printed circuit boards (movable) 190 component carriers / printed circuit board 192 electronic components 220 optical inspection system 230 Lighting device 230A Lighting light / Lighting path 232 additional lighting devices 232a Additional lighting light / additional lighting path 240 camera system 242 first image sensor 242a first measuring light / first measuring path 244 second image sensor 244a second measuring light / second measuring path 246 common measuring light / common measuring path 250 Optics 252 lenses 262 first beam splitter 264 second beam splitter 260 image processing units 295 objects Z1 Distance to the first image sensor Z2 Distance to the second image sensor F1 first focal plane F2 second focal plane 340 camera system 342 single image sensor 342a first measuring light / first measuring path 344a second measuring light / second measuring path 440 camera system 442 first image sensor 442a first measuring light 444a second measuring light 444 second image sensor (transparent) 444a first and second measuring light 540 camera system 542 single image sensor 550 Optics (adaptive) 552 lenses (adjustable) 552a Displacement movement

Claims

[1] Manufacturing machine (100) for a production line for electronic assemblies, comprising the manufacturing machine (100) a chassis (102); a manufacturing tool (119) which is attached directly or indirectly, movable or fixed to the chassis (102); and an optical inspection system (120a, 120b, 220, 320, 420, 520) which is attached directly or indirectly, movable or fixed to the chassis (102), wherein the optical inspection system (120a, 120b, 220, 320, 420, 520) has a lighting device (230) for illuminating an object (295) with illuminating light (230a), a camera system (240, 340, 440, 540) for recording of (i) a first image of the illuminated object (295) using a first measuring light (242a, 342a, 442a) and (ii) a second image of the illuminated object by means of a second measuring light (244a, 344a, 444a), optics (250, 550) which is arranged in a beam path of the illumination light (230a), the first measuring light (242a, 342a, 442a) and / or the second measuring light (244a, 344a, 444a), and an image processing unit (260) which is connected downstream of the camera system (240, 340, 440, 540), wherein the illumination device (230), the optics (250, 550) and / or the camera system (240, 340, 440, 540) are configured and arranged such that the first image has a first blur and the second image has a second blur which is different from the first blur, and wherein the image processing unit (260) is set up to determine a three-dimensional height map of at least part of the object (295) based on the first image and the second image. [2] Manufacturing machine (100) according to the preceding claim, wherein a first depth of field area associated with the first blur of the optical imaging of the first image and a second depth of field area of ​​the optical imaging of the second image, associated with the second blur. do not overlap. [3] Manufacturing machine (100) according to one of the preceding claims 1 to 2, wherein along a propagation direction of the illumination light (230a) a first focal plane (F1), which is assigned to the first image, lies in front of an object plane of the object (295), and a second focal plane (F2), which is assigned to the second image, lies behind the object plane of the object (295). [4] Manufacturing machine (100) according to one of the preceding claims 1 to 2, wherein either the first uncertainty or the second uncertainty is at least approximately zero. [5] Manufacturing machine (100) according to one of the preceding claims, wherein the illumination light (230a) strikes the object (295) along a z-axis and the first measuring light (242a, 342a, 442a) and the second measuring light (244a, 344a, 444a) exit the object (295) along this z-axis. [6] Manufacturing machine (100) according to the preceding claim, wherein the optical inspection system (120a, 120b, 220, 320, 420, 520) has a first beam splitter (262) which spatially separates a part of an illumination path of the illumination light (230a) from a part of a measurement path of the measurement light (246). [7] Manufacturing machine (100) according to the preceding claim, wherein in particular at least one further illumination light (232a) is coupled in for the object (295) via a reflection at the first beam splitter (262), wherein the further illumination light (232a) illuminates the object (295) at a different angle than the illumination light (230a). [8] Manufacturing machine (100) according to the preceding claim, wherein the illumination light (230a) and the further illumination light (232a) have different light colors. [9] Manufacturing machine according to one of the preceding claims, wherein the optics (250, 550) are at least approximately free from chromatic aberration. [10] Manufacturing machine (100) according to one of the preceding claims, wherein the optics (250, 550) are telecentric. [11] Manufacturing machine (100) according to one of the preceding claims, wherein the camera system is configured to record a third image of the illuminated object using a third measuring light, wherein the lighting device, optics and / or camera system are configured and arranged such that the third image has a third blur which is different from both the first blur and the second blur, and wherein the image processing unit is set up to further determine the three-dimensional (3D) height map based on the third image. [12] Manufacturing machine (100) according to any one of the preceding claims 1 to 11, wherein the manufacturing machine is a placement machine (100) and wherein the manufacturing tool is a placement head (119) which is configured to (i) Picking up electronic components (192) from a component pick-up position (116) of a component feeder (115), (ii) Transporting the collected components (192) to a placement area (110) of the placement machine (100) in which a component carrier (190) to be placed is located, and (iii) Placing the components transferred to the assembly area (110) at a predetermined component mounting position on the component carrier (190). [13] Manufacturing machine (100) according to the preceding claim 12, wherein the camera system is fixed in space, directly or indirectly attached to the placement head. [14] Manufacturing machine (100) according to the preceding claim 12, wherein the camera system (240, 340, 440, 540) is fixed in space directly or indirectly attached to the chassis (102). [15] Manufacturing machine according to any one of the preceding claims 1 to 11, wherein the manufacturing machine is a solder paste printing machine. [16] Manufacturing machine (100) according to any one of the preceding claims 1 to 15, wherein the camera system comprises a first image sensor (242, 442) for capturing the first image and a second image sensor (244, 444) for capturing the second image, wherein the two image sensors (242, 442; 244, 444) are arranged in a fixed position relative to the optics (250) and / or relative to the illumination device (230). [17] Manufacturing machine (100) according to the preceding claim 16, wherein the optical inspection system (120a, 120b, 220) further comprises a second beam splitter (264) which spatially separates a part of a first measuring light path of the first measuring light (242a) from a part of a second measuring light path of the second measuring light (244a). [18] Manufacturing machine (100) according to the preceding claim 16, wherein the first image sensor is a transparent image sensor (444) which detects the first measuring light (444a) and through which the second measuring light (442a) passes in order to be detected by the second image sensor (442). [19] Manufacturing machine (100) according to any one of the preceding claims 1 to 15, wherein the camera system has only a single image sensor (342) which can be spatially positioned with respect to an object plane and / or with respect to the optics (250), so that in a first position of the single image sensor (342) the first image can be recorded and in a second position of the single image sensor (342) different from the first image sensor (342) the second image can be recorded. [20] Manufacturing machine (100) according to any one of the preceding claims 1 to 15, wherein the camera system (540) has only a single image sensor (542) which is fixed in space with respect to an object plane and / or with respect to the optics (550), and wherein The optics (550) are an adaptive optics (550) with respect to focus, such that (i) in a first state with a first focus from the single image sensor (542) the first image is captured and (ii) in a second state with a second focus from the single image sensor (542) the second image is captured. [21] Manufacturing machine (100) according to any one of the preceding claims 1 to 15, wherein the optics exhibit chromatic aberration and the illumination light has at least a first illumination color and a second illumination color, and wherein The first measuring light is assigned to the first illumination color and the second measuring light is assigned to the second illumination color. [22] Manufacturing machine (100) according to the preceding claim 21, wherein (i) the first image is captured in a first operating state of the optical inspection system in which the object is illuminated with the first illumination color and wherein (ii) the second image is captured in a second operating state of the optical inspection system in which the object is illuminated with the second illumination color. [23] Manufacturing machine (100) according to the preceding claim 21 or 22, wherein the camera system has a spectrally resolving image sensor which is configured to extract the first image and the second image from a total image of the illuminated object, taken with both the first illumination color and the second illumination color.

Images