Miniaturization efforts and increasing demands regarding reliability of mechatronic systems require new materials and processes for the 3D mechatronic integrated devices (3D-MID) technology. Currently, in the area of 3D-MID mostly thermoplastic materials are in use in the industry, which are metallized using the LPKF-LDS® process. This paper is supposed to demonstrate the eligibility of thermoset resins as a new material class for 3D-MID applications and as a packaging option for silicon chips which are currently encapsulated using transfer molding of thermosets. The reliability of the conductor tracks made using a LDS-additive free process as well as the adhesion forces are investigated. Different laser parameters for structuring of two different substrate materials are compared. For reliability testing a thermal shock test is applied. Furthermore, the adhesion is tested using Hot-Pin-Pull testing. The conductor tracks surpass 2000 cycles thermo-mechanical load without showing strong deterioration of the track resistivity. The incorporated approach enables electrically reliable functionalization of packaged dummy chips including vias for connection to terminals on the chips. The results of the tested injection moldable thermoset resins are comparable to state-of-the-art 3D-MID thermoplastic substrates and thus, suited as circuit carrier material in electronic packaging.
Power electronics is concerned with the use of electronic devices to control and transfer electric power from one form to another. Power electronics can be found in laptop chargers, electric grids, and solar inverters. Die-attach interconnections form a critical part of power electronics devices. Silver sintering is traditionally used for die-attach interconnections because of its high melting point and ability to form very thin thicknesses. However, the processing time compared with soldering is very long. Sintered layers might contain large voids that affect the mechanical stability of the structure. Stresses caused by mechanical and environmental conditions might cause degradation and possibly early failures. This work focuses on studying the combined effect of process factors on the shear strength of small-area die-attach interconnections in silver sintering. Design of Experiments (DoE) tools were used to build an experimental matrix with a 95% confidence level. The results have shown that holding time has a considerable effect on the mechanical stability of the die-attach interconnections. Intermetallic compounds formed in the sintered joints at higher holding times resulted in lesser voids. Furthermore, the treatment level of the holding time highly affects the shear strength under the other factors of temperature and pressure.
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