LPKF-LDS Process

It is also possible to prepare plastics for laser direct structuring without the specific LDS additive. LPKF has a product akin to an LDS painting system for this purpose. ProtoPaint LDS is a two-component primer/curing agent system for coating plastic injection moldings with an LDS-compatible skin. Application is by standard spray gun or with a recently developed and more user-friendly aerosol. A coat approximately 30 to 40 pm thick has to be applied in two steps and then cured. The plastic parts prepared in this way can then be structured the results are comparable to those achieved with LDS plastics. This process, however, is intended primarily for prototyping because the constant-use properties are not comparable with those of plastics with LDS additive in the compound [15]. 

FIGURE 3.3 Laser ablation with simultaneous additive activation 

The oldest laser structuring machine from the LPKF company for LDS is the Micro-LineSD 160i as a single-head laser system complete with rotary indexing table for series production. [103] 

The size of an MID part for LDS depends on the maximum scan volume of the laser system. In the case of the MicroLineSD 160i, for example, this is a truncated pyramid with a bottom-face diameter of 160 mm, a height of 24 mm, and a shell-to-base angle of 77.4° [104]. The counterpart truncated pyramid of the entry-level FusionSD 1100, by contrast, measures 120 mm across its base and 50 mm in height [108]. 

The thicker the section the wider the inside diameter of the vertical interconnect has to be for the laser beam to reach all the inside surfaces in the hole. 

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FIGURE 2.17 Current portfolio of materials compatible with the LPKF-LDS process (graphics courtesy of LPKF)... 

This metallization bath is widely used in prototyping, particularly for testing different structuring parameters of the LPKF-LDS process. It has a footprint of 50 x 40 cm and plugs into a standard socket outlet. The fact that it works only with copper is a drawback, as is the short life cycle [106]. 

Sintered models are porous, so infiltrating surface-sealing processes can be used. Sintered parts are not as detailed and are rougher than stereolithographic parts, but mechanically they are stronger and can sustain higher loads [61,186]. Plastics compatible with the LPKF-LDS process for surface structuring (see Section 7.3) are not available for either of these processes. 

Materials The LPKF-LDS process is compatible only with certain materials. The overview of materials approved by LPKF comes right after the introduction to the guideline. 

The main laser-structuring techniques for MID are derivatives from the world of printed-circuit board engineering. For this reason the various techniques are commonly classified as additive, semiadditive, or subtractive. Laser direct structuring is an additive technique, and its most important manifestations are LPKF-LDS and ADDIMID. MIPTEC, a process developed by Panasonic, is one of the semiadditive techniques. Subtractive laser structuring techniques are commonly used on ceramic substrate materials. Figure 3.2 is an overview of the individual structuring techniques and the steps involved. 

ADDIMID is another additive laser structuring technique. It can be employed to structure stereolithographic components or injection-molded plastic bodies. The process was qualified within the framework of a research project at the Bayerisches Laserzentrum, the laser applications research facility of the Friedrich-Alexander University, Erlangen-Nuremberg. The similarities between the LPKF-LDS and the ADDIMID processes are firstly in the resemblance of the process chains and secondly in modification of a plastic by the addition of special fillers. At this time the technology is under development, but initial results of research are indicative of potential for future applications. [3]... 

Smoothing laser-structured flats is possible, but it involves an additional process step and requires the appropriate equipment. Another point to bear in mind is that laser parameters such as frequency and power are responsible for the roughness of the plastic surface. Consequently, if smoothing is a possibility it is also important to look to optimization of LPKF-LDS laser structuring [185]. 

LPKF Laser Electronics AG has developed ProtoPaint LDS, a process by which virtually any plastic body can be structured by the method known as LPKF-LDS [85,86,105], A paint system based on polyurethanes with an isocyanate hardener and laser-activated additives is applied for the LDS-compatible surface modification of a plastic body produced by rapid prototyping. Known as ProtoPaint LDS, this... 

The LPKF design guideline provides a very detailed and user-friendly overview of all the processes associated with the LPKF-LDS method. The design rules and parameters for the laser direct structuring process itself are dealt with in detail in Chapter 3. 

The laser-structured prototypes can then be metallized in a conventional machine for MID. Alternatively, LPKF offers a metallization set consisting of the laboratory containers and equipment, chemicals, and analyzing accessories designed to be installed in a laboratory extractor on the user s premises as a cascade of process containers. Users who do not have laboratory facilities can opt for the ProtoPlate box for chemical copper plating of LDS prototypes. This is a kit in which the electrolyte is ready for use immediately after being mixed and requires no analytical monitoring (Fig. 7.4) [132]. 

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