DE202020101145U1 - Device for stacking, aligning and connecting layers of printed circuit boards - Google Patents

Abstract

Device for stacking, aligning and connecting circuit board layers (8, 9) which have electrically conductive layers or structures (6, 7) and are connected to one another in a stacking space (16) of the device, comprising a holding device (22) for holding an upper one Circuit board layer (8) and an alignment device for aligning the upper circuit board layer (8) relative to a lower circuit board layer (9) located in the stacking space (16), characterized in that the alignment device is a parallel kinematic movement device (18) with six or more linear actuators (19 ), which act together on the holding device (22) for holding the upper circuit board layer (8).

Description

The invention relates to a device for stacking, aligning and connecting circuit board layers, which have electrically conductive layers or structures and are connected to one another in a stacking space of the device, according to the preamble of claim 1.

Multilayer circuit boards often include several circuit board layers in the form of inner layers, which in particular consist of so-called cores and are glued to one another by means of prepreg layers.

Prepregs often consist of a resin-impregnated glass fabric that is pre-dried but not hardened so that the resin, when activated by heating, flows again, sticks and then completely cross-links. Prepregs are therefore heat-activated adhesive layers that are usually reinforced with glass fabric.

Printed circuit board cores are usually referred to as pre-pressed layers with the structure: copper foil-prepreg-copper foil.

During the production of the circuit boards, the individual circuit board layers and the prepreg layers in between are laid one on top of the other in the correct order, exactly aligned with one another and initially only locally limited or connected to one another at certain points (pre-laminated) in order to create a coherent stack of circuit board layers with precisely positioned circuit board layers for further processing receive. The final lamination of the circuit board layers takes place later in a heating press.

It is known that the handling of the printed circuit board layers, i. the feeding and alignment, to be carried out with machines that have mixed forms of serial and parallel kinematics that have a maximum of four degrees of freedom, i.e. Movements around four axes. The printed circuit board layer to be aligned can thus be shifted in the z-direction (up and down), in the xy-direction (shift in the horizontal plane) and rotated around the z-axis. With serial kinematics, several actuators are connected in series so that one actuator has to move another actuator. In this context, parallel kinematics are understood to mean several actuators that are arranged next to one another and act simultaneously on the same part.

The disadvantage of these known devices is that the printed circuit board layer to be aligned can only be moved with four degrees of freedom. Inequalities in the machine frame can therefore not be compensated for to the desired extent. Furthermore, it would be desirable to improve the repeatability of such devices during the alignment process and to increase the speed when handling the circuit board layers.

The invention is therefore based on the object of creating a device for stacking, aligning and connecting layers of printed circuit boards, with which the stacking and aligning process in particular can be carried out with the highest possible accuracy and speed.

According to the invention, this object is achieved by a device having the features of claim 1. Advantageous embodiments of the invention are described in the further claims.

The device according to the invention is characterized in that the alignment device comprises a parallel kinematic movement device with six or more linear actuators, which act together on the holding device for holding the upper circuit board layer.

In the context of the present invention, the term "lower circuit board layer" refers to that circuit board layer that is already in the stacking space, while the term "upper circuit board layer" refers to that circuit board layer which is subsequently, in particular together with a prepreg layer arranged on its underside, is placed on the lower circuit board layer and aligned relative to this.

The parallel kinematic movement device according to the invention with six or more linear actuators improves the dynamics, precision and speed of the stacking and aligning process considerably. The repeatability of the positioning that can be achieved is much higher than with serial mechanics. The purely parallel kinematics with six or more linear actuators not only enable alignment with a maximum of four axes (displacement in x, y, and z directions as well as rotation around the z axis), but also alignment by rotation around the x- and y-axes (tilting the alignment planes), so that a total of six degrees of freedom are given. In this way, inaccuracies from the machine base frame can be compensated for in a very simple and quick manner. By using more than six linear actuators, kinematic redundancy can be created, which further increases the precision and safety of the alignment process. Furthermore, the energy balance of the parallel kinematic movement device according to the invention is improved compared to serial mechanisms or hybrid designs.

According to an advantageous embodiment, the linear actuators are lifting cylinders that are moved by an electric motor. Such linear actuators can make changes in length in a very fast and extremely precise manner.

According to an advantageous embodiment, the alignment device has at least one camera system for optical position detection of the upper circuit board layer relative to the lower circuit board layer, the camera system generating control signals for activating the parallel kinematic movement device. The actual position of the circuit board layer already in the stacking space and / or the circuit board layer to be placed on this circuit board layer can in this way be recognized by the camera system, in particular through orientation markers placed on the circuit board layers. The parallel kinematic movement device is then controlled in such a way that it carries out compensatory movements until the deviation of the actual position from the target position is minimal. A plurality of camera systems, in particular two camera systems, are preferably provided to increase the accuracy.

According to an advantageous embodiment, the device comprises a transport device for transporting the printed circuit board layers from a receiving station to the stacking space, the parallel kinematic movement device being part of the transport device. This means that the parallel kinematic movement device can be moved between the receiving space, in which the printed circuit board layer to be stacked, optionally together with one or more prepreg layers, either manually or by means of a robot, and the stacking space.

According to an advantageous embodiment, the holding device for holding the printed circuit board layer comprises vacuum suction cups which are designed to suck in and hold the printed circuit board layer by means of negative pressure. As a result, the printed circuit board layer to be transported and stacked can be picked up in a very simple and rapid manner and safely transported to the stacking space. However, other holding devices, for example mechanically or magnetically acting gripping devices, are in principle also conceivable.

The holding device is expediently attached to a lower base plate of the parallel-kinematic movement device, one end of each linear actuator being connected in an articulated manner to the base plate. If the parallel kinematic movement device is a hexapod, for example, the movement of the lower base plate of the hexapod can be transmitted directly to the holding device and from there to the printed circuit board layer to be aligned.

According to an advantageous embodiment, the device comprises a prepreg activation device in the form of an ultrasound generating device with at least one sonotrode for locally activating a prepreg layer arranged between the upper and lower circuit board layers by means of ultrasound.

Such an ultrasonic generating device offers the advantage that the pre-lamination of the stack of layers, i.e. the locally limited heating and hardening of the prepreg layer (s) and thus the locally limited connection of the individual printed circuit board layers of the stack of layers can take place at very high speed. Only a fraction of the time required for conventional devices that work with conventional heating elements is required for heating and curing the prepreg layers. The production times for the circuit boards can therefore be shortened accordingly or the throughput can be increased accordingly. Furthermore, the energy expenditure required for pre-lamination is significantly lower than with known methods, since less waste heat is lost due to the shorter bonding time and the efficiency is higher. Less waste heat is generated that is not used for the pre-lamination process. Another advantage is that no special copper patterns are required on the circuit board to optimize heat transfer. The area in which the bond is made can be very narrow or small, which helps to improve the utilization of the raw material.

According to an advantageous embodiment, the ultrasound generating device comprises a plurality of sonotrodes which are arranged in the stacking space around the parallel kinematic movement device and are attached to a common lifting device for lowering and placing the sonotrodes on the upper circuit board layer and removing them from the upper circuit board layer. In this way, a relatively simple design can be implemented with a few components. However, it is also possible to provide the sonotrodes independently of one another on separate lifting devices.

The prepreg activation device advantageously comprises a sonotrode that can be moved within the stacking space by means of a movable robot arm. This makes it possible to position the sonotrode as desired in the stacking space and to glue the stacked circuit board layers to one another at any point. Such a freely movable sonotrode can in particular be provided in addition to further sonotrodes which carry out the prelamination in the edge regions of the stack of layers.

According to an advantageous embodiment, the holding device for holding the circuit board layer comprises clip units which are designed to clamp the prepreg layer and the circuit board layer together during transport from the receiving space to the stacking space. This makes it possible in particular to provide a stack of one or more prepreg layers and a printed circuit board layer with at least one conductive layer or structure, for example a core layer, in the receiving space, this stack then being held together by the clip units during the transport of the stack to the stacking space.

According to an advantageous embodiment, the device has clamping units for fixing the stack of layers located in the stacking space. This ensures that the printed circuit board layers, which are exactly aligned with one another, remain exactly positioned with one another and are not shifted when the sonotrodes are placed.

• 1: eine schematische Darstellung eines Lagenaufbaus einer Leiterplatte mit sechs Leiterplattenlagen, die leitende Schichten oder Strukturen aufweisen,
• 2: eine räumliche Darstellung von Komponenten der erfindungsgemäßen Vorrichtung zum Ausrichten und Vorlaminieren von Leiterplattenlagen;
• 3: einen Vertikalschnitt durch einen Teil der Komponenten von 2 in vergrößertem Maßstab; und
• 4: die Einzelheit IV von 3 in vergrößertem Maßstab.

The invention is explained in more detail below with reference to the drawings. Show it:

• 1 : a schematic representation of a layer structure of a circuit board with six circuit board layers, which have conductive layers or structures,
• 2 : a three-dimensional representation of components of the device according to the invention for aligning and prelaminating circuit board layers;
• 3 : a vertical section through part of the components of 2 on an enlarged scale; and
• 4th : the detail IV of 3 on a larger scale.

In 1 a cross-section through a six-layer printed circuit board is shown as an example to illustrate a conventional layer structure. The thicknesses of the individual layers are not shown true to scale.

In the 1 illustrated circuit board 1 comprises two inner or core layers 2 , 3 , which by means of an intermediate prepreg layer 4th are connected to each other.

The inner layers 2 , 3 each consist of a prepreg core 5 , which has electrically conductive structures on both sides 6th , 7th is coated from copper. The electrically conductive structures 6th , 7th are usually made of copper foils with a thickness of 18 µm to 210 µm, in the thick copper range up to 400 µm. The thickness of the prepreg core can vary widely and, for example, be between 50 μm and 3200 μm. The inner layers 2 , 3 are usually made from pre-pressed layers in which the prepreg core 5 and the copper layers applied on both sides are firmly connected to one another and are available on the market in this state.

The thickness of the prepreg layer 4th to connect the two inner layers 2 , 3 can also vary widely and be from less than 100 µm to more than 3000 µm. It is also possible that the prepreg layer 4th is formed from several individual prepreg layers.

Above the upper inner layer 2 is an upper outer circuit board layer 10 arranged by means of a prepreg layer 11 on the upper inner layer 2 is attached and can be made for example from an electrically conductive copper foil. The upper circuit board layer 10 can partially with a solder mask 12 be covered, which leaves predetermined solder points free and protects the remaining areas from wetting with solder.

Furthermore, in the embodiment shown, it is below the lower inner layer 3 a lower outer circuit board layer 13 arranged, which can be formed from an electrically conductive copper layer and by means of a prepreg layer 14th with the lower inner layer 3 connected is. The lower outer circuit board layer 13 can in turn by means of a solder mask 15th be partially covered.

Based on 2 to 4th a device is described below which is particularly advantageously suitable for the production of printed circuit boards such as the printed circuit board 1 several inner layers ("cores") such as the inner layers 2 , 3 to be stacked on top of one another, to be aligned precisely to one another and then at predetermined limited locations by heating the prepreg layer in between 4th to connect or glue together. This creates a cohesive stack of layers which enables the stack of layers to be processed further without the inner layers shifting towards one another 2 , 3 to risk. In addition, however, the device according to the invention can also be used for stacking the outer circuit board layers 10 , 13 and for locally limited connection with the inner layers 2 , 3 by means of the prepreg layers in between 11 , 14th suitable.

In the 2 Components shown are part of a device or machine with which the inner layers 2 , 3 one after the other from a receiving station, not shown, to a stacking room 16 transported by the device, stacked on top of one another, precisely aligned with one another and then at predetermined locations by means of the in between lying prepreg layer 4th connected (glued) together.

For this purpose, the device has a transport device 17th for transporting the inner layers provided manually or by machine in the receiving station 2 , 3 and laying down the inner layers 2 , 3 in the stacking room 16 on.

The transport device 17th comprises an alignment device for aligning the subsequent inner layer 2 relative to that already in the stacking room 16 located inner layer 3 . This alignment device comprises a parallel kinematic movement device 18th with six variable-length linear actuators 19th , the upper end of which is attached to an upper holding plate 20th is hinged, while its lower end on a lower base plate 21st is hinged. The parallel kinematic movement device thus forms a hexapod. This construction enables the lower base plate 21st relative to the upper retaining plate 20th can be moved with six degrees of freedom, namely with three translational and three rotational degrees of freedom. Such a movement device 18th is also known as a steward platform.

With the linear actuators 19th it is expediently to lift cylinders moved by an electric motor, which are controlled in the desired manner by a suitable control device (controller). The linear actuators 19th are mostly arranged vertically and hang on the upper retaining plate 20th .

The upper retaining plate 20th is a circular disk in the illustrated embodiment, but can also have a different shape. Further is the upper retaining plate 20th expediently attached to a carriage, not shown, which runs along a horizontal running rail, not shown, of the device between the receiving space and the stacking space 16 is movable. Other systems for moving the parallel kinematic movement device 18th between the receiving space and the stacking space 16 are basically also possible, for example an attachment of the movement device 18th on a robotic arm.

On the lower base plate 21st is a holding device 22nd for holding the printed circuit board layers to be transported and aligned. In the exemplary embodiment shown, this holding device comprises a plurality of vacuum suction cups 23 that are placed on the corresponding circuit board layer from above and can hold it by applying negative pressure. Appropriately, these are vacuum cups 23 in the edge areas of the holding device 22nd arranged. Additionally or alternatively, however, it is also possible to use vacuum suction cups 23 to be provided at other locations remote from the edge areas. It is also useful if the vacuum suction device 23 are attached to a common support plate.

From the 2 and 3 are still parentheses 24 evident. These bracket units 24 are expediently in the four corner areas of the holding device 22nd attached and serve to clamp together several layers, which are simultaneously from the receiving space to the stacking space 16 be transported. For example, by means of the clamp units 24 a stack of layers are clamped together from one of the vacuum cups 23 held inner layer 2 and one or more prepreg layers arranged underneath 4th consists.

2 also shows two camera systems 25th that are on opposite sides of the stacking area 16 are arranged. The camera systems 25th are designed in such a way that they reflect the actual position of the lower inner layer 3 top inner layer to be attached 2 relative to the lower inner layer 3 recognize, for example over on the inner layers 2 , 3 etched orientation markers. The signals from the camera systems 25th are then used to move the parallel kinematic motion device 18th to be controlled in such a way that the deviation between the actual position and the target position is minimal. Number and arrangement of the camera systems 25th can vary widely and depend on the particular application.

The device also has clamping units 26th to fix one in the stacking room 16 located stack of layers 27 on. The clamping units 26th are on a work table 28 arranged and each comprise a clamping jaw 29 standing on a rail 30th slidable in the y direction and adjustable in the z direction, ie in height. The clamping units 26th prevent the individual layers, after they have been precisely aligned by means of the alignment device, from being able to shift again during the subsequent connection process. The clamping takes place automatically. Is an upper layer on a lower layer by means of the parallel kinematic movement device 18th have been deposited and aligned, the clamping jaws 29 on the aligned stack of layers 27 past upwards and then moved in the y-direction so far that it removes the aligned stack of layers 27 overlap. By subsequently moving the clamping jaws 29 The stack of layers is then clamped downwards 27 .

Appropriately, the four clamping units 26th can be moved independently of each other. This means that the lower layers can be closed using two clamping units 26th remain fixed, while the top layer with the other two clamping units 26th can be fixed before the first two clamping units 26th also overlap the upper layer.

After the top inner layer 2 together with the prepreg layer arranged below 4th on the lower inner layer 3 is placed and precisely aligned relative to this, the stack of layers thus formed 27 Glued together at individual points (pre-laminated). For this purpose, as from the 2 to 4th visible, several sonotrodes 31 on the stack of layers 27 placed on the prepreg layer using ultrasound 4th to activate locally, ie to heat, liquefy and harden. Sonotrodes are known to be tools that are set into resonance vibrations by the introduction of high-frequency mechanical vibrations (ultrasonic vibrations) that are generated by an ultrasonic generator. The sonotrodes 31 are with pressure on the stack of layers 27 placed and thus transmit the ultrasonic vibrations to the stack of layers 27 .

The means of the sonotrodes 31 Ultrasonic vibrations applied preferably have a frequency greater than 10 kHz and an amplitude in the micrometer range (1 µm - 50 µm). In particular, the sonotrodes 31 work with a frequency of 40 kHz and an amplitude of 35 µm. It is characteristic here that the direction of oscillation is perpendicular to the stack of layers 27 is. The stack of layers 27 is thereby compressed and relieved again. The resulting friction generates heat that is needed to make the resin of the prepreg layer 4th to harden.

The sonotrodes 31 have a relatively narrow, somewhat elongated contact or working surface, which in the illustrated embodiment is near the edge of the stack of layers 27 be placed on this. The four sonotrodes 31 are in the illustrated embodiment in the vicinity of the corner areas of the stack of layers 27 arranged, but can also be located in other places depending on the application. The sonotrodes are at their upper end 31 attached to a lifting device, not shown, with which the sonotrodes 31 between a raised position and one on top of the stack of layers 27 applied contact position can be moved.

In the following, the procedure for ultrasonic bonding is illustrated using two inner layers as an example 2 , 3 by means of an intermediate prepreg layer 4th described.

First is the lower inner layer 3 placed either manually or by machine in a receiving space of the device according to the invention. This lower inner layer 3 is controlled by the parallel kinematic movement device 18th or from the vacuum cups attached to them 23 recorded and to the stacking room 16 transported where the lower inner layer 3 is filed.

Then the next inner layer is 2 with underlying prepreg layer 4th (or several prepreg layers) placed in the receiving space of the device. The inner layer 2 is back from the vacuum cups 23 sucked in and the prepreg layer underneath 4th of the four bracket units 24 seized. Then the inner layer 2 together with the prepreg layer 4th to the stacking room 16 transported.

In the stacking room 16 is the prepreg layer first 4th on the underlying inner layer 3 filed. Then the top inner layer 2 to the one already in the stacking room 16 located lower inner layer 3 aligned. This is done with the help of the camera systems 25th and the linear actuators 19th . The saved position of the already inserted lower inner layer is thereby used 3 with the top inner layer to be placed 2 compared and aligned accordingly.

The target position of the upper inner layer 2 becomes from the positioning of the previous inner layer 3 certainly. Have already been several layers in the stacking area 16 stored, the target position can either be the position of any position of the stack of layers 27 be, a mean value that is determined from the layers already deposited, or some other predetermined value.

When the alignment process is complete, the position of the stack of layers 27 via the clamping units 26th fixed.

Then the ultrasonic transducers, ie the sonotrodes 31 , via a suitable lifting device onto the stack of layers 27 lowered, with the working surfaces of the sonotrodes 31 with a predetermined pressure on the stack of layers 27 be put on.

The bonding process then takes place with the aid of the sonotrodes 31 . Here, the mechanical vibrations in the ultrasonic range are applied to the stack of layers 27 upset. The prepreg layer 4th is limited locally at those points where the working surface of the sonotrodes 31 on the stack of layers 27 rests, heated and hardened. This will make the inner layers 2 , 3 connected to each other at these points.

After this bonding process, if additional layers are added to the stack of layers 27 are to be placed, the process is started again with the material supply, ie by the inclusion of a further layer and an underlying prepreg layer in the receiving space. This is repeated until the layer build-up is complete. The pre-laminated layer structure is then made by the parallel kinematic movement device 18th with the holding device attached 22nd from the stacking room 16 away.

A large number of variants are possible within the scope of the invention. The number of ultrasonic transducers (sonotrodes 31 ) can vary depending on the application, so that more or fewer bonding points in the stack of layers 27 be generated. As an alternative or in addition, the ultrasonic transducers can also be used at other locations in the stack of layers 27 be arranged. The number of camera systems 25th can also vary depending on the application. The parallel kinematic movement device 18th can have more than six linear actuators 19th so that a kinematic redundancy is created. Furthermore, it is possible that the ultrasonic bonding is not carried out in every layer, but for example only in every second or third layer. It is also possible to begin with all the layers of a layer stack 27 to be arranged and aligned on top of one another and then the entire stack of layers 27 to be connected by a single bonding process.

Claims (11)

Device for stacking, aligning and connecting circuit board layers (8, 9) which have electrically conductive layers or structures (6, 7) and are connected to one another in a stacking space (16) of the device, comprising a holding device (22) for holding an upper one Circuit board layer (8) and an alignment device for aligning the upper circuit board layer (8) relative to a lower circuit board layer (9) located in the stacking space (16), characterized in that the alignment device is a parallel kinematic movement device (18) with six or more linear actuators (19 ), which act together on the holding device (22) for holding the upper circuit board layer (8). Device according to Claim 1 , characterized in that the linear actuators (19) are lift cylinders moved by an electric motor. Device according to Claim 1 or 2 , characterized in that the alignment device has at least one camera system (25) for optical position detection of the upper circuit board layer (8) relative to the lower circuit board layer (9), the camera system (25) generating control signals for controlling the parallel kinematic movement device (18). Device according to one of the preceding claims, characterized in that the device comprises a transport device for transporting the printed circuit board layers (8, 9) from a receiving station to the stacking space (16), the parallel kinematic movement device (18) being part of the transport device. Device according to one of the preceding claims, characterized in that the holding device (22) for holding the circuit board layer (8) comprises vacuum suction cups (23) which are designed to suck in and hold the circuit board layer (8) by means of negative pressure. Device according to one of the preceding claims, characterized in that the holding device (22) is attached to a lower base plate (21) of the parallel kinematic movement device (18), one end of each linear actuator (19) being articulated to the base plate (21) . Device according to one of the preceding claims, characterized in that the device uses a prepreg activation device in the form of an ultrasound generating device with at least one sonotrode (31) for local activation of a prepreg layer (4) arranged between the upper and lower circuit board layers (8, 9) Includes ultrasound. Device according to Claim 7 , characterized in that the ultrasound generating device comprises a plurality of sonotrodes (31) which are arranged in the stacking space (16) around the parallel kinematic movement device (18) and on a common lifting device for lowering and placing the sonotrodes (31) on the upper circuit board layer ( 8) and removing it from the upper circuit board layer (8). Device according to Claim 7 or 8th , characterized in that the prepreg activation device comprises a sonotrode (31) which can be moved within the stacking space (16) by means of a movable robot arm. Device according to one of the Claims 6 to 9 , characterized in that the holding device (22) for holding the circuit board layer (8, 9) comprises clip units (24) which are designed to hold one or more prepreg layers (4) and together with the circuit board layer (8, 9) from the receiving space to be transported to the stacking area (16). Device according to one of the preceding claims, characterized in that the device has clamping units (26) for fixing the stack of layers (27) located in the stacking space (16).

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