Patent Application
20120279867
Priority is claimed to German Patent Application No. DE 10 2011 050 131.2, filed on May 5, 2011, the entire disclosure of which is hereby incorporated by reference herein.
The invention relates to a method for producing metal coatings on in particular three-dimensional plastics material parts, in which a conductive layer is selectively produced and, building on said conductive layer, a galvanic reinforcement is produced.
For MID components, electrical and mechanical functions are integrated into a metal-coated injection-moulded part made of a thermoplastic material. In this context, the three-dimensional structures may carry current and also provide shielding or form transmitting surfaces.
In laser direct structuring (LDS), a circuit pattern is applied to the surface of a single-component injection-moulded part by laser beam. At the same, a surface structure is produced which is favourable for the subsequent metal coating and which provides good adhesion of the resulting strip conductors. Another possibility is to ablate an already metal-coated surface with the laser.
In the subtractive technique, also referred to as laser subtractive structuring (LSS), the entire component is metal-coated with copper without an external current. After galvanic copper has been applied, in a further step a resist can be applied, which is subsequently structured by a focused laser beam precisely at the point where the insulation channels will later be positioned. In a further step, the copper is etched away and the surface is refined.
In two-component injection-moulding, the plastics material surface is activated by seeding with preferably palladium. Subsequently, the desired copper layer thickness is applied chemically or electrolytically. The method without an external current has the drawback that it is time-consuming, because of low deposition rates, and a layer thickness of at most 20 μm can be achieved.
These methods share the general process sequence consisting of the steps of injection-moulding, pre-treatment/laser activation and chemical metal coating. Thus, all of the methods share the problems of chemical metal coating, in particular the low metal thickness which can be achieved, the long dwell time of the parts in the metal coating baths and the associated high costs. Moreover, in practice the varied nature of the process steps necessitates highly complex parts handling. This complexity is also increased because component carriers, handling systems, grippers and transport containers have to be configured specifically for the respective constructions.
In the mass market of for example antennas for mobile telephones or modern smartphones, the prior art describes treating the parts for the expedient construction of the metal antenna structures as bulk material in rotating drums in the chemical metal coating baths. Depending on the size of the parts and the drums, drums of this type are often loaded with thousands or tens of thousands of individual parts. A person skilled in the art would recognize that the nature of the parts handling as bulk material in drum assemblies is inherently problematic, or may even be completely impossible, for delicate and mechanically sensitive parts. Moreover, it is apparent that the quality of the metal coating is reduced by the abrasion of the parts against one another in the rotating drums.
MID plastics material parts, such as antennas for mobile telephones, conventionally comprise one or more non-interconnected conductive regions. Depending on the method, these regions are specially treated after the injection-moulding in such a way that copper is deposited selectively only in said regions. For galvanic metal coating of these regions, a number of prerequisites have to be met. First, a continuously conductive starter layer has to be formed in these regions by chemical metal coating or other adapted methods. Second, all of the regions have to be connected to an electric potential. Third, these regions must be electrically insulated from one another at the end of the production process.
In the prior art, the individual method steps such as pre-treatment, chemical metal coating etc., starting from the injection-moulded shaped part, are made more difficult by the fact that the respectively processed components of the individual method steps are collected together as bulk material. Therefore, for further processing, exact positioning in a recess is initially required, there being high requirements on the precision of the positioning during the laser activation.
In an embodiment, the present invention provides a method for producing a metal coating on a plastics material part. Each of a plurality of plastics material parts is connected to a flexible support via a respective connecting part so as to temporarily chain the plurality of plastics material parts together. The connecting part is attached to a respective one of the plurality of plastics material parts on at least one side. An electrically conductive connection is provided between the flexible support and each of the plurality of plastics material parts via the respective connecting part so as to provide a current supply for producing a galvanic metal coating layer on a conductive layer of each of the plurality of plastics material parts.
The present invention will be described in even greater detail below based on the exemplary figures. The invention is not limited to the exemplary embodiments. Other features and advantages of various embodiments of the present invention will become apparent by reading the following detailed description with reference to the attached drawings which illustrate the following:
a is a detailed view of the support shown in
b is a further detailed view of a further configuration of the connection between a connecting part and the support;
In an embodiment of the present invention, the handling of the components is facilitated; in particular, repeatedly laying individual components in corresponding recesses should not be necessary, and the large number of different recesses should be significantly reduced, so as to reduce the setup costs per component type and make rapid, cost-effective construction of thick copper layers by galvanic metal coating possible at a much higher deposition rate than those which can be achieved merely by simple chemical metal coating.
Thus, according to an embodiment of the invention, a method is provided in which the plastics material parts are connected by means of a connecting part to a flexible support, in particular a conveyor band, which is attached to each plastics material part on one or both sides, so as temporarily to chain together a plurality of plastics material parts, in such a way that the electrically conductive connection for the current supply for galvanic metal coating is provided between the support and the plastics material part by means of the connecting part. In this way, the plastics material parts are chained together by means of the support, in a surprisingly simple manner, in a basically continuous band, which can be transported by conveying means. In this context, configuring the process chain in such a way that the support is continuously supplied directly to a plurality of stations of the plastics material part treatment, from the shaping to the galvanic layer construction, is just as conceivable as winding the support which connects the plastics material parts onto a winding form as a semi-finished product, for further use as required, including on other manufacturing sites. Therefore, the MID plastics material components can be interconnected in a simple manner, in such a way that they can be passed on without difficulty from one processing process to the next and galvanically metal-coated, the current being supplied via the support.
A particularly advantageous configuration of the method according to the invention is also achieved by forming a connecting part integrally with each plastics material part. This eliminates the additional working step which would otherwise be necessary for producing the mechanical and electrical connection between the plastics material part and the connecting part, in that the two parts can be produced and further processed in a common manufacturing step as an integral component. Subsequently, a plurality of plastics material parts are connected to the support, so as to form a band, via the connecting part, which is injection-moulded integrally with the respective plastics material part.
It is conceivable in principle, and is also possible in practice, also to produce the support, in addition to the connecting part, together with the plastics material part as a continuous band by injection-moulding, so as to be able to produce all of the required parts together in a single working step. However, a modification whereby the connecting parts are clamped to the support, in particular mechanically, for example at clearances or reliefs in the support, is particularly expedient in practice. This simplifies the production process in that the plastics material parts, including the optionally integrally injection-moulded connecting parts, are produced in a separate working step from the production of the support, in such a way that it is possible with the support to revert back to conventional commercial products. For this purpose, the support is formed for example as a perforated band, in such a way that the connecting part can penetrate through the holes in the support and thus form mechanical clamping by way of an undercut. This produces a connection which can be subjected to a large mechanical load.
Thus, with the regular clearances or recesses, on one hand it is possible to provide a defined advance, in that a drive wheel engages in the clearances, and on the other hand the recesses or clearances which are not needed for the advance are used for mechanically fixing the connecting part. For example, perforations are also suitable for this purpose.
In another configuration which is also particularly promising, the connecting part is connected to the plastics material part along a material weakening which acts as a break-off point, so as to facilitate the subsequent separation of the plastics material part from the connecting part, and in particular to prevent damage to the plastics material part, for example when winding up the support, in that the break-off point prevents the transfer of large forces to the plastics material part.
The formats and dimensions of the plastics material parts which are usually produced in practice often make it possible to fix the plastics material part to a single support on one side. By contrast, it is particularly advantageous for two supports to be connected to a plastics material part positioned between them. Even relatively large plastics material parts can be reliably fixed in this manner, and are additionally optimally protected and fixed in a mechanically stable manner between the external supports.
Similarly, a support which has a recess between two outer edges for the plastics material part is also suitable. By contrast, a configuration of the method in which a plurality of parallel supports are connected by webs, which are arranged between adjacent plastics material parts and hold the supports at a defined distance from one another and can thus have different dimensions depending on the respective plastics material, is particularly expedient. In this way, the supports can be used universally, and connected to webs of different lengths for different plastics material parts.
According to a modification of the method according to the invention in which the webs are connected to the plastics material part, in addition to the function of the webs for mechanically stabilising the supports with a defined spacing, they also perform the task of directly tying down the plastics material parts, in such a way that they can be electrically contacted via the web.
Naturally, with the plastics materials connected to form a band, the process steps can be chained together in a simple manner, whereby the plastics material parts pass through all of the process steps in sequence at a uniform working speed. However, the invention still provides major advantages if the individual process steps are decoupled from one another or even carried out at separate locations. By contrast with the prior art, in which the plastics material parts are separated after each process step and supplied to a further processing station as bulk material, and therefore fixing in a recess is initially necessary, in a further promising embodiment the at least one support is wound up on a winding form together with the connected plastics material parts, and thus prepared for further processing.
For this purpose, in a further embodiment the supports and/or the webs are connected to spacers, which have a height transverse to the primary extension of the support and are dimensioned in such a way that the plastics material parts are at a sufficient distance from one another when the support is wound up. In this way, supports rolled up in this manner can for example be immersed as a whole, that is to say when wound up, in a metal coating bath, in such a way that a plurality of plastics material parts can be treated rapidly at the same time. In this context, the spacers may equally be configured as a separate member or as integral components of the webs or supports. Further, the spacers may also be supplemented as required.
Another configuration which is also particularly expedient is achieved by winding up a separate reusable plastics material strip as a spacer together with the support, resulting in an alternating positioning of the plastics material band and the support. In this case, the plastics material band may have suitable recesses which make it possible to allocate the supports positioned at the front and at the rear in a defined manner appropriate to the positioning. In this way, the spacer can be added as required, making particularly flexible manufacture possible.
The support may consist of an electrically conductive material, in particular a metal, so as to simplify the electrical contacting, which is also made possible by galvanically metal-coating a plurality of plastics material parts. However, a modification of the invention is particularly promising in which at least one support consists of an electrically non-conductive material, for example plastics material, and the conductive connection is produced between the connecting part and the support and/or between the connecting part and at least one, preferably a plurality of conductive regions of the plastics material part, in particular on the basis of a preceding selective activation. In this way, the plastics material parts, the connecting parts and the support are activated and subsequently selectively metal-coated in a common method step. The electrically conductive properties are thus produced as required and can therefore be restricted to defined regions.
Electrically contacting the support by means of a sliding contact makes simple galvanic metal coating possible, in that the required current supply is transmitted to all of the electrically connected plastics material parts via a central power supply. In this case, the sliding contact may for example be provided as an adjacent frictional wheel.
It is further found to be particularly promising in practice for the connecting part to be connected to the support along a contoured line, the length of the line being significantly greater than the width of the connecting part. In other words, the length of the contact line between the connecting part and the support is made significantly longer in that said line is for example wavy, comb-like or zigzagged rather than straight. Similarly, holes, for example a perforation in the connecting part, may also be used as an extension of the contact line in a region lying on the support.
A further advantageous configuration of the method is provided in that the galvanic metal coating is carried out in an electrolytic bath, in which the support is contacted on the end face when wound up. This eliminates the need to unwind the support from the winding form thereof, in such a way that on one hand the compact arrangement of the plastics material parts which are to be metal-coated provides optimum use of space inside the electrolytic bath, and on the other hand the required transport costs can be reduced to a minimum.
In another method which is also particularly promising, the plastics material parts, the connecting parts and the support are coated with a conductive layer over the entire surface thereof in a chemical and/or galvanic metal coating process, subsequently an etch resist in particular made of tin is applied, subsequently insulation paths are made by laser, and finally the regions of the conductive layer which are exposed in this manner are etched.
Using unitary supports with a fixed screen makes flexible manufacture possible, since the different plastics material parts merely require one optionally varied control problem to carry out the method, and meanwhile the need to adapt the process can be largely eliminated.
Thus, the position of the webs and/or recesses in the support can be determined so as further to simplify the position determination on the basis of unitary identification features.
The plastics material parts can be separated in a separate working step, for example including in connection with the assembly of the plastics material part to form a product. In this case it is found to be advantageous if the connecting parts are separated from the plastics material part along the break-off point and/or the material weakening by a mechanical separation process or using electromagnetic radiation. Punching tools and laser cutting systems are suitable for this purpose. The low thermal energy input is found to be advantageous in both methods, and laser cutting makes it possible to change the contour to be cut along the break-off point or the material weakening without difficulty by a simple change to the program, and can therefore be used flexibly in practice.
The method is suitable in principle for application in all MID production methods; LDS, two-component injection-moulding and subtractive processes are merely mentioned by way of example. For example, methods for modifying non-conductive surfaces may also be carried out so as to provide the arrangement of a metal layer by fixing suitable functional chemical groups according to a desired pattern, whereby a conductive material is arranged on these groups. This conductive material subsequently forms the basis for the formation of a metal layer of the desired thickness in accordance with the specific desired pattern. This application of a thicker layer can be provided selectively by using conventional autocatalytic baths for metal coating, and in the context of the method advantageously in galvanic baths.
The method according to the invention for producing metal coatings 8 on in particular three-dimensional MID plastics material parts 3, in which a conductive layer is produced selectively by a chemical process and subsequent galvanic metal coating, is shown in detail in
The invention is based on interconnecting the plastics material parts 3 in such a way that they transition easily from one processing process to the next and can be galvanically metal-coated.
To solve the transport problem, a for example band-shaped support 1 made of plastics material or metal is laid in an injection-moulding tool so as to connect said support to the plastics material part 3 via an injection-moulded connecting part 2. In this context, various variants of the method according to the invention can be distinguished.
In a first embodiment of the invention, the plastics material part 3 is connected laterally to the support 1, which comprises regular recesses 5, formed by a perforation, for the defined transport, as is shown in
By contrast, larger plastics material parts 3 can be provided with a support 1 on each of the two sides, as is shown in
Using webs 6 of this type, the plastics material parts 3 can also be connected by three or four sides to the band structure of the supports 1, as can be seen from
Spacers 10 are preferably provided on the connecting parts 2, which spacers project past the plastics material parts 3 in height and provide a sufficient distance between the individual layers of the plastics material parts 3 when the support 1 is being wound up, as can be seen for example in
As an alternative to these spacers 10, a separate, reusable plastics material band having spacers can be rolled up together with the described support 1, in such a way that the spacers contact the support 1 in the outer region and provide the defined spacing between the individual plastics material parts 3.
It is particularly advantageous for the described supports 1 made of metal or plastics material to be used for galvanically metal-coating the plastics material parts 3. The plastics material parts 3 conventionally comprise one or more non-interconnected conductive regions. Depending on the method, these regions are specially treated after the injection-moulding in such a way that copper is deposited selectively only in said regions. For galvanic metal coating of these regions, a number of prerequisites have to be met. First, a continuously conductive starter layer has to be formed in these regions by chemical metal coating or other adapted methods. Second, all of the regions have to be connected to an electric potential. Third, these regions must be electrically insulated from one another at the end of the production process.
According to an embodiment of the invention, the conductive regions of the plastics material parts 3 are connected to one or more supports 1 on one or more sides via the connecting parts 2, as is shown in
The connecting parts 2 between the support 1 and the respective plastics material part 3 comprise a material weakening 4 in the form of a constriction, by means of which a secure mechanical connection is initially maintained. At the same time, the plastics material part 3 can be released from the composite at the end of the production process by suitable separating methods such as punching or laser cutting along this material weakening 4. Each connecting part 2 can connect one or more conductive regions of a respective plastics material part 3 to the band-shaped metal support 1. For this purpose, the connecting parts 2 are pre-treated and galvanically metal-coated, at least in portions, together with the regions which are made conductive of the plastics material parts 3.
In the proposed method, a distinction should be made between the use of metal and plastics material supports 1.
By pre-treating the connecting parts, for example by laser irradiation with subsequent chemical metal coating, a conductive connection can be produced between the band-shaped metal support 1 and the connecting parts 2 and thus the conductive regions of the plastics material parts 3. This creates the possibility of permanent, reliable current supply to the plastics material parts 3 via the support 1, and thus meets a basic requirement for the galvanic metal coating of the conductive regions of the plastics material parts 3.
It is particularly advantageous for the reliable electrical connection of the support 1 to the connecting part 2 if the connection length of the support 1 to the metal-coated plastics material of the connecting part 2 is increased.
It is also advantageous to perforate the support 1 with holes in the region of the comb structure 9 of the connecting parts, as is shown in
When plastics material bands or bands of other non-conductive materials are used as a support 1, there is no longer the possibility of supplying current via the support 1, and there is thus no need for the conductive connection between the connecting parts 2 and the support 1. Alternatively, however, there is the possibility of spraying around the support 1, continuously over the length thereof, in a sub-region comprising plastics material connecting parts, as is shown in
Chemically metal-coating the connecting parts 2 thus results in a continuous conductive path, which can be used for continuous current supply, along the support 1, as can be seen from
Irrespective of the support material used, one or more, preferably two, supports 1 may be used, and are all used for current supply. They may be connected to webs 6. The webs 6 may comprise a perforation. The connecting parts 2 may be connected to the webs 6 in the same way as to the supports 1, as can be seen in particular from
In one embodiment of the invention, the galvanic metal coating takes place in a container. For this purpose, the winding form 11, together with supports 1 which are wound thereon and which carry the plastics material parts 3, is contacted at the end face via copper fingers arranged in a star shape, as is shown in
Another development of the method provides that the plastics material parts 3 are injection-moulded entirely from metal-coatable plastics material and subsequently coated with copper over the entire surface in chemical and galvanic baths. In a subsequent step, the plastics material parts 3 are coated with a tin etch resist. The conductive layer is structured by introducing insulation paths into the tin layer by laser and subsequently etching the copper regions which are thus exposed. Analogously to the processes described above, the handling between the process steps is simplified in this case too by the connection of the plastics material parts 3 to the support 1 which acts as a conveyor band. The advantages of galvanically reinforcing the copper layer which were disclosed in relation to the method also come into play. The method according to the invention can thus in principle be used in all known MID production methods for metal-coating plastics material parts 3, and thus is not restricted to laser direct structuring.
While the invention has been described with reference to particular embodiments thereof, it will be understood by those having ordinary skill the art that various changes may be made therein without departing from the scope and spirit of the invention. Further, the present invention is not limited to the embodiments described herein; reference should be had to the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2011 050 131.2 | May 2011 | DE | national |
