Ultra-fine pitch 3D micro structures by laser direct structuring

A single-component injection-molded part made of a doped plastic serves as a basis for the Laser direct structuring process. Selected surface regions are activated by laser radiation. In a subsequent electroless metallization process, first copper layers and then additional metal coatings such as nickel and gold are deposited on these activated surfaces. Current processes can achieve a pitch of 300 microns (line/space of 150 µm/150 µm). As devices continue to become smaller, the individual processes and the process as a whole face greater challenges. For a miniaturized high-precision MID, high-precision injection-molded blanks made out of a suit-able polymer and exhibiting outstanding surface quality are required. Currently, all plastic-additive combinations have been optimized for laser activation in the NIR range (laser wavelength: 1064 nm). The laser wavelength plays a key role in structuring, especially with respect to focusing ability. In recent development work, the effect of various wavelengths on the LDS materials was investigated, and a wavelength of 532 nm was found to be suitable for the desired structure widths. For LCP, PPA, PEEK, and a few thermosetting plastics, laser parameters that can be used in practice are already available. As the structure widths decrease, the demands on the optical systems increase. Laser structuring utilizes a completely new processing unit de-sign. A special laser source, a new, highly dynamic scanner, and opti-mized optical elements deliver the required precision and performance. A camera in the beam path enables visual inspection of the structuring re-sults during the process. With dimensions of 60 x 60 mm, the scanning field is much smaller than that of conventional processing units. After structuring the metallization is carried out. In this process step, ultra-fine conductor applications present new challenges – inaccurate metallization and debris can quickly lead to short circuits. Dry ice cleaning solves this problem. It removes ablation products from the surface and reduces the surface roughness of the generated structures to produce bondable surfaces. The proven electroless process and bath chemicals are available for cop-per metallization. Suitable filtration is required to ensure that no bridging by copper particles is possible. Whereas conventional components are commonly protected against environmental factors by chemically plated nickel/gold, ultrafine conductor structures have palladium/gold or silver surface finishes. By avoiding use of nickel as a barrier layer, it is possible to minimize line broadening. A number of critical questions have already been answered by now: a processing unit combining a laser source and optical elements is available, tests on key materials are underway, and reliable production parame-ters have already been identified for some of the LDS plastics. Market introduction is planned for the near future.