Additive Manufacturing of Mechatronic Integrated Devices

In this dissertation a new process chain for the Additive Manufacturing  of Mechatronic Integrated Devices (AMMID) is described, which provides a  new way to manufacture 3-dimensional electronic devices based on the  selective laser sintering (SLS) process using laser direct structuring  (LDS) and metallization. The AMMID process chain meets the rising demand  for highly functionalized parts, increasing individualization and  shortening development cycles for electronic products.
The  development for this process chain is based on an extensive literature  review that indicates that an SLS-based process chain has great  potential to produce 3-dimensional electronic devices with properties  and with the future perspective of being suitable for an individualized  mass production. The biggest, initial, technical hurdle is an unstable  SLS process using a conventional LDS additive. The compound of SLS  material and LDS additive was analyzed with DSC, which shows that the  additive changes the melting behavior of the polymer by reducing the  sintering window. A fine metal powder as an alternative additive affects  the sintering window less and enables a stable process. To choose a  suitable particle size and content for the metal powder an analytical  material model is provided, that predicts the additive particle  distribution within the material. This material model deepens the  understanding of the activation mechanism during laser activation,  provides hands-on information for powder preparation and it is applied  for the design of the experiment for the development of the process  chain with the new material.
Preliminary experiments are conducted  along with the insights of the material model, which prove that  redeposition is the main activation mechanism during laser activation  with fine metal powders. Based on this, the process chain is developed,  starting with a determination of a suitable additive content. A suitable  material composition of a PA12 powder containing 2 wt.% of a copper  powder with a mean particle diameter of 3.5 μm was identified. With  regard to the laser activation, working laser parameters are developed  (working parameter set feasible for all used post-process treatments:  PRF = 1 kHz, dh = 25 μm, vs = 25 mm/s, tl = 20ns and P = 1.07 W). In  this parameter development it is shown, that only closely located laser  spots, enabling interaction of the laser pulses, are capable of  activating the surface, while single laser pulses under applied  conditions are not. By adding a post-process treatment as additional  process step into the process chain, the quality of metallization and  the size of design features could be improved. Chemical smoothing  resulted in a complete reduction of unwanted metallization on  non-activated surfaces. Conductor tracks with the minimal width of 300  μm could be realized. The process chain could be applied to demonstrator  parts such as a drone housing and a PSU panel of an aircraft. Thus,  this dissertation has raised the technology readiness level (TRL) from  TRL2 to TRL6.
Finally, an economic consideration provides insights on  the cost structure of parts produced with the AMMID process. A  comparison of AMMID and injection molding shows economic viability for  small lot sizes, 400 parts in case of the drone housing and 150 parts in  case of the PSU panel. Finally, the analysis of the cost structure  gives advice which future developments in the process chain have the  greatest effect on costs and provides prioritization.