Untersuchungen zur Serienfertigung von mechatronischen Mikrosystemen auf Basis spritzgegossener Schaltungsträger am Beispiel von Braille-Modulen

The Molded Interconnect Devices (MID) technology offers a high potential for the miniaturization of multifunctional three dimensional plastic devices in communication, medical technology, automotive applications, mechanical engineering and in industrial automation. Manufacturing flexibility, design freedom in three dimensional as well as high mechatronic integration density are the main characteristics underlining the potential of these technologies.

Today, textual information for blind people are provided by speech synthesizers or Braille lines. The needs of blind people grow with the evolution of computer applications beyond pure speech applications. The major disadvantage of electronic Braille lines is that only textual information can be provided. Two dimensional electronic Braille displays have been designed, which consist of novel Braille modules to present graphical information. In each Braille module, pins are driven by 10 piezo actuators at a voltage of 200 V each. Furthermore in each novel module touch sensors are needed, emulating the function of a computer mouse. Additionally, each module requires an integrated circuit with two bare die ASICs and several SMDs for controlling the piezo actuators and the touch sensor as well.

For such highly integrated Braille modules the application of MID technologies combining miniaturization with high functionality is very promising. Due to the costs and metal line pitch of the tooling the 2-shot injection molding is not suited. The hot embossing MID is not suited because it is restricted to planar metal line layout through the stamp geometry, namely only plain surfaces can be processed. Laser based MID technologies such as the laser semi additive (LSA) and the laser direct structuring (LDS) processes are particularly suitable for the complex three dimensional circuitry of the novel MID Braille modules.

This thesis describes the series production of novel mechatronic Braille modules using two MID technologies, the LSA and LDS technology. Manufacturing implementation and quality concepts were developed and used. During each process phase a quality control step has been performed on each Braille module. All test data was compiled in a data base system, therefore it was possible to monitor the yield of the modules e.g. failure causes and failure rate. A total of 12.563 modules in LSA technology and a total of 5.489 modules in LDS technology were processed.