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978-3-8439-1321-8, Reihe Ingenieurwissenschaften
Ein Beitrag zum Aufbau spritzgegossener Schaltungsträger mittels Heißprägetechnik
146 Seiten, Dissertation Universität Stuttgart (2013), Softcover, A5
This work deals with hot embossing technology, a fast and simple method for MID-manufacturing. Though industrially used for many years, there are still some issues to improve.
The endurance of hot embossing stamps is limited to approximately 800 embossing cycles, than the stamp surface is contaminated and the stamp has to be removed for cleaning. With hard coatings deposited by PVD or PECVD processes the endurance of the stamps could be increased significantly. The investigations show that best results were achieved with DLC coatings, with which up to 4000 embossing cycles were performed without intermediate cleaning step.
For building circuits electrodeposited Cu-foils (ED-foils) are commonly used, the more reasonable rolled and annealed foils (RA-foils) so far are not accessible for hot embossing, because the conductor lines are not separated from the foil during the press cut. In order to make RA-foils still accessible for hot embossing, a process was developed, which pre-cuts the conductor lines with laser technique. It was found, that small fixed links along the cut are the best solution for handling and good embossing results. The feasibility of the technology was evaluated on functional MID-devices.
Hot embossing for circuit manufacturing so far is limited to rigid boards, the process conditions normally leads to a strong deformation of flexible materials. In this work new high temperature resistant flex-materials were investigated and the hot embossing equipment was improved. It could be demonstrated, that with an optimized stamp design and an anvil equipped with vacuum fixation and temperature regulation the warpage of the thin foils could be reduced almost completely and flexible circuits could be produced in good quality. Finally a process for manufacturing of two layer circuits on thin flexible foils with micro welded interconnects was developed successfully.