CH719575A2 - Process for the additive manufacturing of a three-dimensional shaped body. - Google Patents

Abstract

A method for the additive manufacturing of a three-dimensional shaped body with metallized areas comprises the following steps: providing a photopolymer (PP) containing additives (A), which can be used in a laser direct structuring process for producing the metallized areas (M); Additive manufacturing of the three-dimensional shaped body (F) based on a lithography process with a process heater to heat the photopolymer (PP); Carrying out the laser direct structuring process on the additively manufactured three-dimensional shaped body (F); and metallization of the areas to be metallized (M) of the three-dimensional shaped body (F).

Description

Field of invention

The present invention relates to a method for the additive manufacturing of a three-dimensional shaped body, as well as a three-dimensional shaped body.

Background of the invention

[0002] Three-dimensional shaped bodies, be they made of metal, plastic, or ceramic, can be produced using 3D printing, which manufacturing process is also referred to as additive manufacturing or generative manufacturing. Here, a starting material is built up in layers to form a shaped body. For example, a CAD model of the molded body to be created can serve as the basis for later controlling the 3D printer.

The counterpart to additive manufacturing processes are subtractive manufacturing processes or injection molding processes. Injection molding processes can also be used to produce circuit boards. Three-dimensional circuit carriers manufactured using an injection molding process are referred to as Molded Interconnect Devices (MID). In a first step, a molded part is produced using a single- or multi-component injection molding process. The injection molding material is a plastic. If metallized areas are subsequently to be produced on the molded part using so-called laser direct structuring (LDS), the plastic is mixed with additives necessary for the LDS process. The desired areas are then activated and structured using a laser. For this purpose, a laser beam is directed onto the molded part. The laser energy from the laser activates the additive in the plastic material. This creates metallic germs. If these metallic seeds subsequently come into contact with metal such as copper, this results in metallization of the desired areas. This creates an additive conductor track structure. The injection-molded and metallized molded part can then be equipped with the desired components to obtain an assembled molded interconnect device.

[0004] In additive manufacturing, different processes are used depending on the material/starting material. The so-called fused deposition modeling (FDM) can additively process a plastic that is also used in the injection molding process to produce MIDs, for example an ABS plastic. Here, the thermoplastic ABS plastic is extruded, heated at the desired grid points and then hardened by cooling, whereby a layer of the three-dimensional molded body is created. However, fused deposition modeling does not have sufficient process precision as required for the production of circuit boards. This is due to the extrusion process used to apply the plastic.

This leads to an irregular surface, which does not guarantee sufficient reproducibility for the smallest metallized structures, for example in the range of <100 μm, as are required for the production of highly integrated circuit carriers. A smaller extruder nozzle may ensure a more uniform surface of the extruded material. Apart from the fact that even such a measure still does not provide the required process accuracy, this measure also slows down the process time significantly, since significantly more extruder tracks are now required to generate a layer. In this respect, the FDM process, regardless of training, is not suitable for producing three-dimensional circuit boards as an alternative to MID technology.

Another process belonging to the additive manufacturing process is stereolithography (SLA), in which a plastic in the liquid phase is used to build up the layer. The partial molded body created so far is lowered into the plastic bath to create a further layer or fed to the plastic bath. A laser irradiates the grid points that are to form the next layer, thereby hardening the plastic. However, the applicant's experiments have shown that the conventional SLA process is not suitable for the addition of additives such as those required for the application of laser direct structuring. The plastics used in the SLA process are not viscous enough for the added additives to not settle due to gravity. However, in additive manufacturing this can lead to areas that only have a low concentration of additives. In these areas, sufficient metallization nuclei cannot be formed in the laser direct structuring, so that consistent metallization is not guaranteed.

Presentation of the invention

It is therefore the object of the present invention to provide a method for the additive manufacturing of three-dimensional circuit carriers which maintains the required process precision and ensures the metallization of areas or conductor tracks using laser direct structuring (LDS).

[0008] This object is achieved by a method according to claim 1.

[0009] Thus, a method for lithography-based additive manufacturing of three-dimensional molded bodies is proposed, which molded bodies represent three-dimensional circuit carriers in the sense of Molded Interconnect Devices (MID), which, however, are not injection molded but are additively manufactured. The stereo-lithography-based additive manufacturing process (SLA) used uses process heating. It is therefore also called the hot lithography process. In order to make the hot lithography process compatible with the LDS process, additives are added to a photopolymer suitable for the SLA process, which allow laser direct structuring.

With this method, the process steps before the laser structuring process are sufficiently precise and process-reliable and reproducible. The additively created molded part has sufficient layer resolution and surface quality. According to the invention, it is therefore proposed to use a hot lithography process instead of fusion deposition modeling for the process steps before the laser structuring process, i.e. H. a lithography-based process with a process heater. The process heating serves to heat the thermoplastic photopolymer used for the additive creation of the three-dimensional shaped body to a target temperature that has a second viscosity V2 that is sufficiently low for the lithography process, and thus uniform wetting of the previously created layer by the photopolymer SLA process ensures., By heating the photoactive starting material present in its first, high viscosity V1, its viscosity is reduced to the second viscosity V2, which is lower than the first viscosity V1, and which in particular represents a liquid phase of the photopolymer, whereas the first viscosity represents a viscous phase of the photopolymer. Preferably, the second viscosity V2 is less than 10<3>mPa*s, whereas the first viscosity V1 is greater than or equal to 10<3>mPa*s.

The photopolymer preferably has the first, high viscosity V1 at room temperature. Preferably, the process heater heats the photopolymer to a temperature greater than room temperature. Preferably, the target temperature that the photopolymer reaches due to heating is greater than 40 °C, preferably greater than 50 °C or 60 °C.

[0012] In addition, photopolymers typically have low chemical reactivity in the high-viscosity state, and are only chemically reactive in the low-viscosity state. Compared to standard stereo lithography, more heat-resistant photopolymers can now be used. This is particularly advantageous if, as intended, the molded part created is used as a circuit carrier. Components are usually soldered onto this circuit board, including onto the molded part under the influence of heat.

By heating the photopolymer shortly before curing in SLA production, the photopolymer can in turn be stored in its highly viscous form, transported and made available as a starting material. This high viscosity ensures that the uniform distribution and/or uniform spatial concentration of the added additives required for laser direct structuring is maintained, once the additives have been introduced and are evenly distributed in the starting material. This also achieves the uniform distribution and/or uniform spatial concentration of the additives in the low-viscosity state shortly after heating and thus during exposure/curing.

[0014] According to the invention it is therefore achieved that the LDS additives cannot separate in the resin (i.e. the photopolymer). This allows a safe LDS process with a homogeneous distribution of the additives in the molded body or component to be achieved.

According to the invention, a modified stereo-lithography process is used to convert photopolymers or resins which have LDS additives into a desired three-dimensional shaped body in lithography-based additive manufacturing. This means that highly viscous resins can be used as starting materials for layer construction in generative processes, which in turn enable bond-free embedding of LDS additives. The high-viscosity resins are converted into low-viscosity resins required for the SLA process by heating using a process heater, preferably associated with a 3D printer intended for additive manufacturing. The heating therefore preferably takes place as part of the supply of the resin into the construction space of the 3D printer, or as part of the supply to the location in the construction space where the resin, in its then liquid phase, comes into contact with the previously created layer of the previously created layer created molding occurs. This makes it possible to produce MID-like shaped bodies using a special stereo lithography process [SLA], e.g. the hot lithography process.

Preferably, the following steps in the additive manufacturing of the molded part are carried out repetitively per generation of a layer: a) heating the photopolymer present in the state of its first viscosity V1 by means of the process heating; b) providing the photopolymer present in its second viscosity V2 as a result of the heating at the location of a previously generated layer of the shaped body; c) curing the photopolymer provided by exposure using a first laser to generate a new layer on the previously generated layer.

[0017] Preferably, steps a) to c) are repeated for each layer to be created. Preferably, steps a) to c) are all carried out in the installation space. However, in one embodiment, the process heating can also be located outside the installation space and the already heated resin can be supplied to the installation space, for example via a line. In a further development of the invention, the process heating comprises a heatable cartridge, which heats the photopolymer guided through the cartridge and outputs it in a low viscosity V2. The cartridge can be arranged in the installation space or outside the installation space. The installation space is typically defined as the container in whose volume the molded part is built up additively, preferably arranged on a movable platform. The latter can be moved in a controlled manner, in particular vertically, in order to bring the layer into contact with the liquid phase of the photopolymer in the container after it has hardened in order to create the next layer, or in order to further lower the partially manufactured molding in the plastic bath so that the Bath covers the last hardened layer. All of these variants should fall under the expression of “providing the low-viscosity material at the location of the previously created layer”; So in particular the variants: feeding the partial molded part to the low-viscosity material; feeding the low-viscosity material to the molded part; Heating the highly viscous material at the location of the previously created layer. According to the last variant, the provision of the low-viscosity material at the location of the previously created layer can also include the provision of the high-viscosity starting material at this location and the heating at this location, for example when heating the entire installation space, or when heating this location selectively. The process heating can be constantly active, or pulsating and active at least at the times when the high-viscosity material is to be converted into its low-viscosity state.

In another development, the process heater is designed to heat the entire installation space either alone or in conjunction with a separate heater for dedicated heating of the highly viscous material. In the first variant, the highly viscous resin is introduced into the construction space and heated continuously while the layers are being built up. In this version, too, the resin can be stored and transported in a highly viscous form. Once the amount of high-viscosity photopolymer, which is preferably sufficient to completely create the molded part, has been introduced into the construction space, it is heated there continuously, either until all layers of the molded part have been created, or as long as the material in the construction space has been used up.

In another development, however, the resin is supplied in portions either to the installation space or to the above-mentioned location, preferably as a portion for one or a few (less than or equal to five) layers. This reduces the tendency of the additives to settle in the low-viscosity material in the installation space due to only a short residence time in the low-viscosity state.

In an advantageous development, in particular if the resin is heated in portions and/or the heating takes place by a separate process heater and/or outside the construction space, the construction space is nevertheless also continuously heated during additive manufacturing in the construction space. It is advantageous to keep the molding that has already been partially created by exposure at the same or similar temperature (+/-20%) as the low-viscosity resin provided. This avoids mechanical stresses in the molded part induced by a temperature gradient.

Preferably, the low-viscosity material/the low-viscosity photopolymer is exposed at the location of the new layer to be built up, preferably by means of a laser, and thereby hardened and solidified. This creates a further layer in the layer structure of the shaped body, with a spatially essentially evenly distributed concentration of the additives for the later laser direct structuring.

Preferably, the production of the layers, i.e. additive manufacturing, is carried out computer-aided, preferably fully automated in a construction space of a corresponding 3D printer, and preferably by an appropriately programmed control of the 3D printer.

With regard to direct laser structuring, it is preferred to remove the additively created three-dimensional molded part from the 3D printer, preferably using suitable robotics, and transport it to another workstation outside the 3D printer to produce the metallized areas on the surface of the molding. At this other workstation, a second laser (in the nomenclature compared to the first laser of the 3D printer) is preferably provided. This second laser is used to irradiate the molded part in the areas that are to be metallized, e.g. conductor tracks are “written” with the second laser. As a result, the added additives in the molded body are activated in these areas, i.e. metal nuclei are split off from the additive. In a further step, preferably at another workstation, metal, for example copper, is then fed to the surface of the shaped body. The metal selectively binds to the areas previously irradiated by the second laser through chemical reductive catalysis, so that these areas become metallized areas on the shaped body.

[0024] Such metallized areas can serve as circuit carriers in the later use of the three-dimensional molded body as conductor tracks, or contact points, or antennas, or thermal conductive surfaces, or electromagnetic shielding.

According to a further aspect of the present invention, a three-dimensional shaped body with metallized areas is provided, produced by a method according to one of the preceding exemplary embodiments.

According to a further aspect of the present invention, a three-dimensional shaped body is provided which has a layered structure. On the one hand, the shaped body has metallized areas, preferably on its surface. The material of the shaped body is a hardened photopolymer. This photopolymer and thus the shaped body contains additives which can be used in a laser direct structuring process to produce the metallized areas, even apart from the metallizations.

The shaped body is therefore a three-dimensional circuit carrier and is designed three-dimensionally in that, compared to a planar two-dimensional circuit carrier such as the conventional printed circuit board (PCB), it has an extension into the third/vertical dimension, which goes beyond the usually small thickness of a conventional printed circuit board . The 3D circuit board as such has conductor tracks and conductive surfaces. The functionality of the three-dimensional circuit carrier is comparable to a three-dimensional MID (Moulded Interconnect Device). However, it is not injection molded, but rather additively manufactured before the desired areas are metallized using LDS.

The proposed method is advantageous because it can be used to create almost any three-dimensional structures and design them into circuit boards. The present method can also be used to produce metal surfaces that lie inside the 3D circuit board and serve, for example, as a ground surface. For example, a molded body is produced additively. Areas of this molded body are then subjected to laser direct structuring to create metallized areas on its outer surfaces. This partially metallized molded part can then be placed in the 3D printer again. Additional layers are then built up additively on the metallized areas as well as on other non-metallized areas. The resulting molded part is then directly laser-structured on its outer surfaces to create the metallized areas.

Further embodiments of the invention are the subject of the subclaims.

Brief description of the drawings

Advantages and exemplary embodiments of the invention are explained in more detail below with reference to the drawing. Fig. 1 shows a flowchart of a method according to a first exemplary embodiment, Fig. 2 shows a flowchart of a method according to a second exemplary embodiment, Fig. 3 shows a laser direct structuring method according to a third exemplary embodiment, and Fig. 4 shows a diagram representing the method according to another embodiment.

Detailed character description

1 shows a flowchart of a method according to a first exemplary embodiment. According to the first exemplary embodiment, a lithography process is used for the lithography-based additive manufacturing of three-dimensional shaped bodies. For this purpose, a three-dimensional CAD model of the shaped body to be produced is created in step S1. In step S2, the three-dimensional model is divided into a plurality of layers. In step S3, the lithography system is prepared. In step S4, lithography-based additive manufacturing of the three-dimensional shaped body takes place based on the layers determined in step S2. In step S5, the shaped body produced is removed and in step S6, the shaped body is cleaned and, if necessary, reworked. In step S7, further post-processing of the molded body produced takes place in a laser direct structuring process LDS.

2 shows a flowchart of a method according to a second exemplary embodiment. The steps for lithography-based additive manufacturing of the three-dimensional shaped body from step S4 are described below. In step S41, the photoactive polymer (e.g. a photopolymer) is introduced into a coater in layers, for example from a cartridge. The cartridge can have a heating unit so that the material can be introduced into the coater from a heated cartridge. In step S42, a building platform is approached into or to the material platform up to a defined distance and the photopolymer is irradiated with light or electromagnetic radiation. In particular, the construction platform is lowered to the height of the layered ceiling and the material is exposed, for example, by a laser. In step S43, the build platform is raised after exposure to remove the exposed material from the material platform and apply new material using the coater. In step S44, this process is repeated until the desired shaped body is obtained. In step S45, the molded body is cleaned to remove unwanted material. In step S46, the material is hardened, for example by UV irradiation and/or by heating the material.

According to one aspect of the present invention, the system for additive manufacturing of the three-dimensional shaped body has a process heater so that the photopolymer can be heated or warmed to the required temperature during the manufacturing process. This can be done by using a heatable cartridge for the polymer or by heating the polymer after it exits the cartridge.

3 shows a laser direct structuring method according to a third exemplary embodiment. In Fig. 3, the post-processing according to step S7 is further defined. In step S71, the shaped body is structured with a laser based on a laser direct structuring method LDS. While in the standard laser direct structuring process the molded part or the molded body is produced in a one-component injection molding process, this molded body according to the invention is produced as described in FIG. 2 based on a lithography process with a process heater. In step S72, the desired conductor track and contacts are metallized on or in the molded body.

[0035] In step S73, a final metallization with NiP-Au can optionally take place. An optical and/or electronic test can then be carried out in step S74. The manufacturing process of the shaped body can then be ended.

4 shows a diagram which illustrates the method according to a further exemplary embodiment. This references (1) a 3D printing workstation, (2) an LDS station and (3) a metallization station, for example an electroplating shop. The 3D printing workstation has a construction space 1, with a slidably mounted platform for carrying the molded part F to be created, or its predecessor stages (partial molded parts pF). The molded part F is manufactured additively from layers S in installation space 1. In the present example, a storage container 5 is provided outside the installation space 1, which is filled with a photopolymer PP mixed with additives A in a highly viscous form. The high-viscosity photopolymer is fed via a line 51 to a heatable cartridge 12 within the installation space 1, in which cartridge 12 the high-viscosity photopolymer PP is heated and delivered into the installation space 1 as a low-viscosity photopolymer PP, still with essentially spatially evenly distributed additives A. In particular, the platform 11 is controlled in such a way that the last layer produced at location O is wetted by the bath of low-viscosity photopolymer PP. Using a first laser 13, the low-viscosity photopolymer is cured at location O and forms a further layer on the partial molded body F. In addition, a schematically drawn heater 14 can be provided for the entire installation space 1, which keeps the installation space 1 at an approximately constant temperature. Once the molded body F is additively completed with all layers S, it is transported to the LDS station (2). There, a structure for a later conductor track is written into the surface of the molded part F using the LDS process using a second laser 2. The molded part F treated in this way is then exposed to metal particles in the metallization station (3), which chemically bind to the laser-structured areas and thus form metallized areas M.

Laser direct structuring LDS can be used to produce a three-dimensional circuit carrier. In the first step, a molded part is produced. The material here is a plastic with additives. Laser activation and laser structuring can then take place. For this purpose, a laser beam is directed onto the molded part. The laser energy from the laser activates the additives in the thermoplastic material. This creates metallic germs. Laser treatment can achieve a micro-rough surface onto which, for example, copper can be applied during metallization. An additive conductor track structure can be achieved for metallization. The molded part can then be equipped with the desired components in order to obtain the three-dimensional circuit board.

The molded parts are therefore not produced by an injection molding process, but rather by lithography-based additive manufacturing (for example using hot lithography).

The method according to the invention for the lithography-based additive manufacturing of three-dimensional shaped bodies thus initially involves additive manufacturing of a shaped body based on a hot lithography process in which process heating takes place. Additives are added to the photopolymer used here, which enable a laser direct structuring LDS process. After the three-dimensional shaped body has been produced using the hot lithography process, laser activation and structuring takes place. The desired metallization sections are then metallized. The molded body can then optionally be equipped with the desired components.

[0040] A method for the lithography-based production of three-dimensional shaped bodies using a stereo lithography process with a process heater is shown in WO 2018/032022. Such a method can be used to produce the shaped body of step S4. A material that can be solidified by electromagnetic radiation is provided on a permeable material support. A building platform is positioned at a distance from the material support. Material located between the component shape and the material support is heated and, in the heated state, is irradiated and solidified in a location-selective manner by a radiation source. The radiation occurs from below through the material layer, which is at least partially transparent to the radiation from the first radiation source, into the material. The material can be heated by irradiating the material support with electromagnetic radiation from a second radiation source.

In the hot lithography process, the material which is to be solidified using electromagnetic radiation is heated. The hot lithography process therefore represents a stereo lithography process with a process heater that heats the material to be solidified. The process heating in the hot lithography process allows different materials to be used than in a standard stereo lithography process. Thus, according to one aspect of the present invention, a high viscosity, low reactivity, photoactive polymer may be used as a material for lithography-based additive manufacturing. In contrast, the standard stereo lithography process SLA can only use low-viscosity, highly reactive, photoactive polymer. According to one aspect of the present invention, molded parts with higher accuracy and higher reproducibility can thus be made possible. Due to the high viscosity of the material, an additive required for the LDS process can be better distributed in the material for additive manufacturing.

The polymer used in additive manufacturing is a photoactive polymer, which is highly viscous and low reactive. An example of such a photoactive polymer is described in EP 3 632 941 A1.

According to one aspect of the present invention, a three-dimensional shaped body can be produced based on the hot lithography process (stereo lithography process with a process heater). The material used for additive manufacturing has additives that correspond to an LDS additive or enable an LDS process.

Cubicure Thermoblast or Cubicure Evolution FR can be used as the photopolymer.

Merck Iriotek 8850 or Merck Iriotek 8825 can be used as LDS additives.

Claims (9)

1. Method for the additive manufacturing of a three-dimensional shaped body with metallized areas, with the steps Providing a photopolymer (PP) containing additives (A), which can be used in a laser direct structuring process for producing the metallized areas (M), Additive manufacturing of the three-dimensional shaped body (F) based on a lithography process with a process heater to heat the photopolymer (PP), Carrying out the laser direct structuring process on the additively manufactured three-dimensional shaped body (F), and Metallization of the areas to be metallized (M) of the three-dimensional shaped body (F). 2. Method according to claim 1, in which the photopolymer (PP) is a photoactive polymer with a first viscosity (V1), in which the photopolymer (PP) assumes a state with a second viscosity (V2) smaller than the first viscosity (V1) as a result of its heating by the process heating, in which the photopolymer (PP) is cured in the state of its second viscosity (V2) by irradiation, preferably in which the first viscosity (V1) is greater than or equal to 10<3>mPa*s, and the second viscosity (V2) is less than 10<3>mPa*s. 3. Method according to claim 2, in which the additive manufacturing takes place using the following computer-aided steps, which are repeated per generation of a layer (S) of the three-dimensional molded body (F): a) heating the photopolymer (PP) present in the state of its first viscosity (V1) by means of the process heater; b) providing the photopolymer (PP) which is in the state of its second viscosity (V2) as a result of the heating at the location (O) of a previously generated layer (S) of the shaped body (F); c) curing the photopolymer (PP) provided by exposure using a first laser (13) to generate a new layer (S) on the previously generated layer (S); preferably in which all steps a) to c) are carried out in one installation space (1) of a device for additive manufacturing. 4. Method according to one of the preceding claims, in which the process heater contains a heatable cartridge (12) for heating the photopolymer (PP) guided through the cartridge (12). 5. Method according to one of the preceding claims, in which the additive manufacturing takes place in a construction space (1), in which the installation space (1) is continuously heated during additive manufacturing. 6. Method according to one of the preceding claims, in which areas (M) of the additively manufactured molded body (F) to be metallized are irradiated with a second laser (2) to activate the additives (A) in the molded body (F) in these areas (M), in which a metal (Me) is supplied to the shaped body (F) and selectively binds to the areas previously irradiated by the second laser (2) to metallize them, in which the metallized areas (M) represent conductor tracks, or contact points, or antennas, or thermal conductive surfaces, or electromagnetic shielding. 7. Method according to one of the preceding claims, in which process the three-dimensional molded body (F) with metallized areas (M) is produced as a pendant to a molded interconnect device. 8. Three-dimensional shaped body with metallized areas, produced by a method according to one of the preceding claims. 9. Three-dimensional shaped body, made up of layers (S), with metallized areas (M), from a hardened photopolymer (PP) containing additives (A), which can be used in a laser direct structuring process to produce the metallized areas (M).