DE102019205289B4 - System for the production of electrical contact elements with selectively refined electrical contact surfaces - Google Patents

Abstract

Plant for the production of electrical contact elements with selectively refined electrical contact surfaces, in which at least the following production devices are arranged in series in a production line: - a forming device (2) through which the supplied metallic strip material (3) is mechanically converted into one for forming the contact elements (4) - a cleaning device (6) which is designed for the selective removal of oil residues on the contact surfaces (5), - a pressure device (8) with which a layer with microparticles and / or nanoparticles of a noble metal is selectively applied Contact surfaces (5) is applied, - a drying device (19) which is designed to dry the applied layer, and - a laser processing device (21) for functionalizing the applied layer, - the laser processing device (21) at least one continuous laser radiation and at least one pulsed laser radiation emitting La ser (22) and is designed so that the layer applied to the contact surfaces (5) is first sintered with pulsed laser radiation and the sintered layer is then completely melted with continuous laser radiation in order to form a homogeneous layer of the noble metal and with the contact surface (5) to fuse, and- wherein the printing device (8) is designed as a device for pad printing, which is adapted for printing with cycle rates of the production line and in which several pads (9) are arranged on a circumferential guide (10) that tampon printing and material take-up from a cliché (13) for at least two tampons (9) take place simultaneously with a lifting or rotary movement.

Description

Technical field of application

The present invention relates to a system for producing electrical contact elements with selectively refined electrical contact surfaces, in which a number of production devices for producing the electrical contact elements are arranged in series in a production line.

To increase the electrical contact and transition conductivity on electrical contact surfaces and also to reduce the susceptibility to corrosion, the electrical contact surfaces can be refined with a noble metal. The finishing takes place by applying a suitable noble metal layer to the contact surfaces, for example by means of electroplating, PVD or CVD processes.

The production of the electrical contact elements has hitherto been carried out in several separate production steps. These are divided into forming and separating processes for the production of the base body of the contact element and into chemical, electrochemical or physical coating processes for contact finishing. These individual production steps cannot be integrated into a common production line, or only with great effort. The reasons for this lie in addition to the requirements of the coating processes in terms of process times and installation space, as well as their process requirements, such as vacuum chambers and upstream cleaning steps. An inline coating of the contact elements with noble metals is therefore not possible or only possible to a limited extent. The resulting interruption of the production line due to additional outward and inward transfer of the components leads to increased production costs.

State of the art

One problem with contact finishing is the often high consumption of precious metals, the use of large amounts of chemicals or - for PVD coatings - the use of energy-intensive vacuum processes. To avoid this problem, it is known to selectively use micro- or nanoparticulate layers made of the precious metal to apply to the electrical contact surfaces and then to sinter or melt by processing with laser radiation. However, microparticulate gold layers, for example, are influenced by the so-called Balling effect when they are melted by means of continuous laser radiation. In the liquid state, the gold contracts to form spheres due to the surface tension, which prevents the formation of a homogeneous gold layer. Adhesion between the contact area and the solidified gold is also insufficient due to this effect. With the laser-based sintering of microparticulate gold layers with pulsed laser radiation, there is, in turn, only slight adhesion between the contact surface and the gold layer.

In the press release of the Fraunhofer Institute for Laser Technology, ILT, dated March 27, 2019, examples are given of the post-treatment of coatings with laser radiation that were applied to a component using pad printing, among other things. The layers are first dried with the laser beam and then the remaining functional particles, for example made of gold, are partially or completely melted in order to obtain a coherent layer. For example, plug contacts can be locally gold-plated.

Out M. Khan et al., "Selective Laser Melting (SLM) of Gold (Au)", Rapid Prototyping Journal, Vol. 18, 2012 On pages 81 to 94, a method for coating a metallic surface with gold is known, in which a layer with microparticles of gold is applied to the surface and completely melted with continuous laser radiation in order to coat the surface with the gold. In this process, an attempt was made to minimize the balling effect by adjusting the scan speed and power of the laser beam.

From the US 2015/0093516 A1 a system for producing contact-enhanced contact elements is known which also uses laser radiation for the functionalization of an applied noble metal layer. In this publication, metallic strip material is unwound from a drum and fed via a deflection roller to a punching and bending device in which the metallic strip material is mechanically brought into a shape suitable for forming the contact elements. The necessary pre-treatment process for the further processing of the strip material is divided into three steps. In the first step, the strip material is passed through a chemical cleaning bath. The strip is freed from punching oil with the help of carbon-based solvents. In the second step, the entire material is passed through another bath in order to reduce the wetting properties of the surface. A fluorine- or silicone-based agent is used for this. The coating is then dried using a hot wire heater. Finally, the coating and native oxidation layers are locally removed from the contact surfaces to be coated with the noble metal by a selective laser treatment and the surface is activated. The coating with the liquid-repellent agent is intended to result in subsequent wetting of the strip material with the dispersion or ink used during printing outside the contact areas prevent. The selective laser treatment for local removal of the layer and activation of the surface should enable the dispersion or ink to adhere to the contact surfaces. A noble metal nanoparticle dispersion is then deposited on the contact surfaces in a printing device with the aid of an inkjet printer or a dispenser. The applied layer is dried in a drying device with the aid of an infrared heater. Part of the solvent contained in the dispersion / ink is intended to be evaporated. Alternatively, an electric oven can also be used. The printed layers are then sintered in a laser processing device using a laser sintering process. The strip material is then rolled up again and can be transported to the finished product.

A challenge in such systems is the coupling of the individual process steps due to the different and sometimes competing demands on the process times. The process times for the individual process steps must be short enough to achieve a high cycle rate for the entire production line.

The object of the present invention is to provide a system for the production of electrical contact elements with selectively refined electrical contact surfaces, in which all production facilities required for production are integrated in a common production line, which enables a high cycle rate and with which a firm, material connection of the for contact finishing applied noble metal layer is achieved with the contact surface.

Presentation of the invention

The object is achieved with the system according to claim 1. Advantageous configurations of the system are the subject of the dependent claims or can be found in the following description and the exemplary embodiment.

In the proposed system, at least the manufacturing devices described below are arranged or integrated in series in a manufacturing line. The start of the production line is formed by a forming device, preferably a punching and bending device, by means of which the supplied metallic strip material is mechanically brought into a shape suitable for the formation of the contact elements. This can already be the final shape or a shape that is not yet final if the contact surfaces in the final shape are not sufficiently accessible for contact refinement. In the latter case, a further forming device is then additionally arranged at the end of the production line, with which the contact elements are then brought into their final shape. A cleaning device arranged following the shaping device is designed in such a way that it removes oil residues on the contact surfaces which have reached the contact surfaces as a result of the previous shaping. After cleaning, a printing process takes place in a printing device, in which a layer with microparticles and / or nanoparticles of a noble metal, for example as a paste or as a sol-gel material, is selectively applied to the contact surfaces. The applied layer is then freed from the solvent or dried in a subsequent drying device. After drying, the applied layer is functionalized in a laser processing device. The system is primarily characterized in that, on the one hand, the laser processing device has at least one continuous laser radiation and at least one laser emitting pulsed laser radiation and is designed so that the micro- and / or nanoparticulate layer applied to the contact surfaces is first sintered with pulsed laser radiation and the sintered layer is then completely melted with continuous laser radiation in order to form a homogeneous layer of the noble metal and to fuse it with the contact surface. On the other hand, the printing device is designed as a device for pad printing which is adapted to the high cycle rates of the production line. In the device for tampon printing, several tampons are arranged on a circumferential guide so that tampon printing and material pick-up from a cliché, preferably also tampon cleaning, can be carried out for different tampons at the same time with just one stroke or rotation. The guide can be, for example, a band-shaped guide that revolves around two rollers or a circular plate (or a wheel) that rotates about its axis of symmetry or center point.

A device for pad printing designed in this way meets the requirements for high cycle rates of, for example,> 50 components / minute. In contrast to the conventional design of devices for pad printing, in which only one pad is used, which alternately picks up a paste with the precious metal and prints it, in the present embodiment several pads are arranged on a circumferential guide in such a way that printing, preferably pad cleaning and material pick-up take place synchronously on each tampon. If a cliché plate with several, for example, circularly arranged cliché depressions is also used, the material pick-up by a tampon and the filling of a cliché can also be carried out simultaneously. The printing process can also be quickly adapted to changed geometries of the contact surfaces by exchanging the cliché plate.

The use of a continuous and a pulsed laser in the laser processing device enables the applied layer of the microparticles and / or nanoparticles to be sintered and then the sintered layer to be melted. The previous sintering of the layer avoids the problems of balling that often occur during subsequent melting, while complete melting then leads to a homogeneous layer and a metallurgical bond between this layer and the material of the contact surface. A reliable and firm connection between the noble metal layer and the contact surfaces is thus achieved.

The proposed system thus enables the inline production of electrical contact elements with refined electrical contact surfaces in a single production line at a high cycle rate, a reliable connection of the refining layers with the contact surfaces being achieved. The contact elements can thus be produced without interrupting the production line. The modular design enables the integration of all system components or production facilities on a common machine body and the activation and process control via a central control system. The process for applying the precious metal layer is integrated into the system. This closes the production line and eliminates the need to discharge the material for conventional coating processes. In contrast to alternative processes such as dispensing printing, the pad printing process used offers the possibility of printing even complex print field geometries using a corresponding cliché with just one stroke movement. This is a prerequisite for implementing high clock rates. By adapting the cliché plate, changing requirements of the print pattern can be quickly addressed. Furthermore, the pad printing process can be used to print microparticulate pastes, which are generally more cost-effective to produce than nanoparticulate pastes / inks.

Figure list

• 1 eine schematische Darstellung einer beispielhaften Fertigungslinie der vorgeschlagenen Anlage mit den einzelnen Fertigungseinrichtungen;
• 2 eine schematische Darstellung einer beispielhaften, in der Anlage einsetzbaren Trocknungseinrichtung im Querschnitt; und
• 3 eine schematische Darstellung einer beispielhaften, in der Anlage einsetzbaren Tampondruckeinrichtung.

The proposed system is described in more detail below using an exemplary embodiment in conjunction with the drawings. Here show:

• 1 a schematic representation of an exemplary production line of the proposed system with the individual production facilities;
• 2 a schematic representation of an exemplary drying device that can be used in the system in cross section; and
• 3 a schematic representation of an exemplary pad printing device that can be used in the system.

Ways of Carrying Out the Invention

The example of a production line of the proposed system described below represents an advantageous combination of production facilities, all of which can be integrated on a common machine body. The system has a modular structure, with all production facilities or production processes carried out with them being highly flexible with regard to the geometric design of the contact element. Cleaning, printing, drying and functionalization processes can be adapted directly to changed component geometries. An adjustment for the printing process is possible by exchanging the cliché plate. The component design is adapted by retrofitting the punching and bending device, which is preferably modular in this case.

In the system described in this example, a punching and bending process is used to reshape the metallic strip material. This punching and bending process must be designed in such a way that, on the one hand, the forming processes on the contact surfaces are completed before the process steps of cleaning, printing and functionalization. On the other hand, sufficient accessibility of the contact surfaces for these subsequent process steps must also be guaranteed. This can make it necessary to split the stamping and bending process into several stages, as shown in the present example. The division of the punching and bending process required to produce electrical contact elements with hard-to-reach contact surfaces is implemented by a machine body which - through the use of servo-driven punching and bending units - removes the mechanical coupling of the individual forming and cutting steps. In this way, the shaping of the contact surface can be completed before the contact surface is cleaned, printed, dried and functionalized. Subsequently, after carrying out the last-mentioned process steps for contact finishing, a further forming and separating step can then be carried out on the same machine body in order to complete the contact element. This fulfills a prerequisite for the inline production of electrical contact elements with selectively refined contact surfaces that are difficult to access.

1 shows schematically an exemplary representation of the production line of such a system. Via a role that does not belong to the system 1 , on which the metallic strip material is wound, is the first punching and bending device 2 the metallic band material 3 fed. The tape material 3 can for example have dimensions from 10 to 100 mm wide, 0.1 to 2.0 mm thick and 100 to 500 m long and made of nickel-plated copper ( 2 to 4th µm thickness of the nickel layer). The tape material shows on the sides 3 preferably a series of holes for belt movement and positioning. With the punching and bending device used 2 > 50 contact elements / minute can be formed from the strip material. This first reshaping takes place in such a way that the contact surfaces are easily accessible for the subsequent refinement, but the contact elements do not yet have their final shape. Below the punching and bending device 2 are in the 1 for example, contact elements shaped according to the stamping and bending process 4th with their contact surfaces 5 shown.

The cleaning of the contact surfaces 5 for the subsequent printing process, an in 1 schematically indicated cleaning device 6th carried out. In this example, this cleaning is carried out using a compressed air-assisted, laser-based process without the use of chemical cleaning agents. By means of compressed air, in particular in the form of an air blade, a large part of the is on the contact surface 5 existing punching oil removed from the surface. Compressed air cleaning alone does not, however, meet the requirements for the cleanliness of the contact surface for the downstream printing process, as a thin, homogeneous oil film remains on the surface. This oil film is used in the present cleaning device 6th on the contact surfaces 5 selectively removed by means of laser radiation, as shown in 1 with the laser 7th is indicated. This can for example be a pulsed laser with a wavelength of 1064 nm. Without the use of compressed air pre-cleaning, the laser cleaning process would be significantly more difficult due to the inhomogeneous distribution of the oil film. A quick sequence of cleaning and subsequent printing processes prevents the oil film from being pulled back onto the selectively cleaned surface. This selective cleaning also enables the cleaning process to be carried out in an energy-efficient manner and corresponds to the requirements placed on the process times for a high cycle rate. The use of such a physical cleaning process replaces chemical cleaning processes. This eliminates the need for storage, handling and disposal of cleaning agents.

Following the cleaning, the printing process then takes place in the printing device, which acts as a pad printing device 8th is trained. With this pad printing device 8th are several tampons 9 on a circular guide 10 arranged as shown schematically in 2 is shown. The 2 also shows that through the pad printing device 8th running metallic tape 3 in cross section perpendicular to the transport direction, in this example in a guide rail 11 to be led. The pad printing device 8th also has a cleaning device 12 for cleaning the tampon surfaces, in the present example an adhesive tape stretched between a winding and an unwinding roller, as well as the cliché designed for receiving the layer material 13 on. The cliché 13 is in this example with a paste 14th filled with microparticulate precious metal. The direction of movement 15th the leadership 10 with the tampons 9 is indicated by an arrow. With a simple lifting movement of the guide, as indicated by the double arrows in the 2 is shown, the paste uptake, pad cleaning and pad printing can take place at the same time, as shown in the 2 can be seen. With pad printing, a layer with a thickness in the range between 1 and 50 µm is applied to the contact surfaces. By using a cliché plate with several clichés 13 the clichés can also be filled in at the same time as the paste is absorbed by a tampon 9 respectively. About an exchange of clichés 13 or the cliché plate, the print job can be quickly adapted to changed component or contact surface geometries.

Before the laser functionalization of the selectively printed contact surfaces, a drying step is required in order to remove the solvents necessary for printability from the printed layer. Without this step, the printed precious metal particles would be removed from the contact surface as a result of the explosive evaporation of the solvent. For drying, the printed contact surface must be exposed to a temperature for a period of time that is sufficient to evaporate the solvent. Since the evaporation rate of the solvent is a temperature-dependent variable, the drying temperature (in combination with the cycle rate) significantly determines the length of the drying path. For this reason, the highest possible temperatures are required, which, however, must be limited to maintain the structure of the base material. In the present system, a drying temperature in the range between 300 ° C. and 500 ° C. is preferably used, for example T = 300 ° C. on a drying section 1.5 m in length. The drying process must also be designed in such a way that the highest possible heating rates are achieved in the dry goods. Heating rates that result from a purely radiation-based heat input into the strip material with the help of IR radiators do not meet these requirements due to the high degree of reflection of the usually nickel-plated substrate material of> 85% (at λ = 2 µm). For this reason, in one embodiment of the Drying device 19th modified so that the heat input into the strip material indirectly via means of IR radiation 18th heated metal guide 16 for the tape material 3 occurs as it is in 3 together with an IR emitter 17th is shown schematically. The metal guide 16 is selected from a material such as copper, which has a high thermal conductivity and also a sufficiently low reflection for IR radiation. The good heat conduction of the metal guide 16 leads to the fact that the printed contact surfaces are exposed to the temperature necessary for drying quickly and independently of the optical properties. The metal guide 16 is also designed in such a way (double C-profile) that buckling of the strip material 3 is prevented by the feed. As an alternative to IR irradiation, a heating plate can also be used, for example, to heat the metal guide 16 used or the strip material can be fed directly over a corresponding heating plate. It is also possible to integrate heating elements (e.g. heating wire) into the metal guide. Due to the high heat capacity of the metal guide 16 the system reacts very tolerantly to fluctuations in enthalpy flow due to variable clock rates As the metal guide 16 and the tape material 3 are in thermal equilibrium after a short time due to the high heating rate, it can be assumed for the temperature control that the temperature of the strip material 3 the temperature of the metal guide 16 corresponds. This means there is no need for complex optical temperature monitoring. A pure heating of the strip material 3 by IR irradiation without the metal guide 16 is basically also possible, but leads to longer drying times.

To achieve reproducible drying results that are independent of cycle rates, a laser system can also be used instead of the IR path, as shown schematically with the laser as an alternative 20th the drying device 19th in the 1 is also indicated. A laser emitting in the UV, VIS or NIR can be used as the laser. When using a laser, the drying times are between 0.01 and 10 s, and when using an IR radiator it is around 20 to 60 s.

The drying process follows in the laser processing facility 21st the laser functionalization process. The printed and dried contact surface is first treated with pulsed and then with cw laser radiation. In the 1 is schematically just a laser here 22nd indicated, whereby both a pulsed laser and a cw laser are used. Both lasers preferably emit laser radiation with the same wavelength, for example with a wavelength of 1064 to 1070 nm. With the pulsed laser radiation, the applied layer is first sintered. The sintered layer is then completely melted with the cw laser radiation in order to produce a homogeneous noble metal layer which is firmly bonded to the contact surface by means of melt metallurgy. As a result, a noble metal layer fused to the contact surface is then obtained.

The contact elements are then placed in a further punching and bending device 23 first bent and then separated. A correspondingly separated, fully formed contact element 4th is in 1 in cross section below the punching and bending device 23 shown schematically. The individual production facilities of the in 1 The production line shown can be integrated on a common machine body and thus enable a very compact design of the system.

List of reference symbols

1

Roll of tape material

2

Stamping and bending device

3

Tape material

4th

Contact elements

5

Contact surfaces

6

Cleaning facility

7th

Laser for cleaning

8th

Pad printing device

9

tampon

10

guide

11

Guide rail

12th

Cleaning device

13

cliche

14th

Precious metal paste

15th

Direction of rotation

16

Metal guide

17th

IR emitter

18th

IR radiation

19th

Drying device

20th

Laser for drying

21st

Laser processing device

22nd

laser

23

Stamping and bending device

Claims (10)

Plant for the production of electrical contact elements with selectively refined electrical contact surfaces, in which at least the following production facilities are arranged in series in a production line: - A shaping device (2) by means of which the supplied metallic strip material (3) is mechanically brought into a shape suitable for the formation of the contact elements (4), - a cleaning device (6) which is designed for the selective removal of oil residues on the contact surfaces (5), - A printing device (8) with which a layer with micro- and / or nanoparticles of a noble metal is selectively applied to the contact surfaces (5), - A drying device (19) which is designed to dry the applied layer, and - a laser processing device (21) for functionalizing the applied layer, - The laser processing device (21) having at least one continuous laser radiation and at least one laser (22) emitting pulsed laser radiation and being designed so that the layer applied to the contact surfaces (5) is first sintered with pulsed laser radiation and the sintered layer is then sintered with continuous laser radiation is completely melted in order to form a homogeneous layer of the noble metal and to fuse with the contact surface (5), and - wherein the printing device (8) is designed as a device for pad printing, which is adapted for printing with clock rates of the production line and in which several tampons (9) are arranged on a circumferential guide (10) that with a lifting or Rotary movement of pad printing and material take-up from a cliché (13) for at least two pads (9) take place simultaneously. Plant after Claim 1 , characterized in that the cleaning device (6) comprises at least one laser (7) which emits laser radiation with which the oil residues on the contact surfaces (5) are removed. Plant after Claim 2 , characterized in that the cleaning device (6) also comprises at least one compressed air device with which the contact surfaces (5) are acted upon with compressed air immediately before being irradiated with the laser radiation. Plant according to one of the Claims 1 to 3 , characterized in that the drying device (19) has a metallic guide (16) for the metallic strip material (3), which reflects IR radiation less strongly than the metallic strip material (3), and an IR irradiation device (17) which the metallic guide (16) is heated. Plant according to one of the Claims 1 to 3 , characterized in that the drying device (19) has a metallic guide or metallic support for the metallic strip material, into which heating elements for heating the metallic guide or metallic support are integrated or which are in contact with a heating device for heating the metallic guide or metallic support is. Plant according to one of the Claims 1 to 5 , characterized in that the drying device (19) has at least one laser device with a laser (20) which is designed and arranged for laser drying of the layer applied to the contact surfaces (5). Plant according to one of the Claims 1 to 6th , characterized in that the production line, following the laser processing device (21), has a further forming device (23) in which the contact elements (4) are brought into a final shape and / or are separated. Plant according to one of the Claims 1 to 7th , characterized in that a central control is connected to the production facilities of the production line and controls these to carry out the production with a predefinable production cycle. Plant according to one of the Claims 1 to 8th , characterized in that the forming device (s) (2, 23) is or are designed as a punching and bending device (s). Plant according to one of the Claims 1 to 9 , characterized in that the production facilities are arranged on a common machine body.

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