Alternative Laser Structuring Processes

FIGURE 3.8 Sample design guidelines for the MIPTEC process according to [124] 

There are more process steps involved in laser subtractive structuring (LSS) than in the additive or semiadditive processes (Fig. 3.2). Injection molding is followed by short surface activation to permit electroless copper or nickel plating. This chemical premetallization is followed by a galvanic process to build up the plating to target thickness. The next step is structuring as such, by application of an activatable etch resist. 

Etch resists can be of the photoresist or galvanoresist type. Photoresists react chemically to UV energy input, and galvanoresists are removed by laser energy. Photoresists can be further categorized as positive or negative. A positive photoresist is soluble after exposure and washes off, whereas exposure decreases a negative resist s solubility (Fig. 3.9). 

FIGURE 3.9 Process differences between positive and negative resists 

The durability of photomasks is limited on account of the high intensity of the UV radiation. On the other hand, laser-patterned photomasks make layout changes a relatively simple and cost-effective matter, assuming that there is no need for alterations to the injection-molding toolset. The benefits of this flexibility always have to be weighed against the higher costs of consumption [48]. 

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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]. 

It was found that the azirine-nitrile ylide isomerization was a completely reversible process. The unlabeled nitrile ylide showed a prominent band at 1926 cm that underwent a 66-cm shift with N substitution. This shift was interpreted as being consistent with an allene-like skeleton (8) rather than the alternative pwpargyl-like stmcture (9). This conclusion was supported by the spectra from the C- and H-labeled variants. Warming the nitrile ylide in a xenon matrix from 12 to 82 K provided no new absorptions suggesting that the allene-like structure may also be adopted in solution. Some absorption spectra for benzonitriho benzylide (DPNY) and some substituted benzonitrilio methylides obtained via pulsed-laser photolysis of azirines are given in Table 7.1 (5). 

Surface modification/treatment of textile materials by chemical finishing processes is not environmentally friendly, as a result of which an alternative technology, laser irradiation has been widely adopted. By using laser irradiation, the textile materials can be structurally modified and their surface can be functionalized and textured. Here, two different examples of textile materials are presented and discussed in terms of laser treatment cotton,... 

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