Wireless data transmission is already a part in almost every area of daily life. Portable user devices like laptops, smartphones, smartwatches, headphones and many other devices use cellular networks, Wi Fi, Bluetooth, and other standards to wirelessly transmit and receive data. Micro acoustic radio frequency filters (RF filters) are the key components to empower the frequency related wireless communication as they provide good filter performance at reasonable component size. Just as in the entire semiconductor industry, there is also a demand for the further miniaturization of surface acoustic wave (SAW) and bulk acoustic wave (BAW) RF filters. The miniaturization of components, which are manufactured at wafer level reduces the costs and increases the functional density. The RF filter size, the electrical performance, and the costs are key to commercially succeed on the market. A package protects the sensitive micro acoustic structures on RF filters against environmental impacts. One of the thinnest commercially available SAW and BAW RF filter components use the wafer level manufactured Qualcomm TFAP™ * (Thin Film Acoustic Package). Solder bumps (SBs) on the TFAP ensure the mechanical and electrical joint to the printed circuit board (PCB) after component assembly and solder reflow. The SBs with a diameter of 140 µm consume a lot of valuable space on the small components. A simple reduction of the SB size is limited because the remaining gap (stand off) between the soldered RF filter component and the PCB would get too small to apply an underfiller in the gap during the final encapsulation process. The encapsulation additionally protects the components. In this thesis the actual SBs on RF filter components with TFAPs were successfully replaced by the space saving copper pillar bump (CPB) interconnection technology. CPBs are built of a cylindrical copper base with a spherical solder cap on top. In contrast to SBs, the height of CPBs and therefore also the remaining stand off, can be broadly adjusted independently from the CPB diameter. The CPBs on TFAPs have a height of 75 µm and a diameter of 65 µm. Depending on the RF filter component size and the number of CPBs up to 26 % of additional free space is gained using CPBs instead of SBs on one component under current design rules. This allows a component miniaturization, the increase of functional density, novel design approaches (e.g. heat sinks, reduction of redistribution layers, combination of various CPB sizes and shapes), and a significant reduction in costs. The CPBs were manufactured with commercial tools by thin film metal deposition, lithography, wet and dry etching, electroplating, and wafer singularization. For component reliability testing a solder paste was stencil printed on the test PCBs prior the RF filter assembly and soldering process. The reliability requirements of damp heat steady state (DHSS), dry heat (DH), unbiased highly accelerated stress test (uHAST), and temperature cycling (TC) on the CPB interconnection were fulfilled. In addition, component shear tests confirmed a sufficient mechanical connection to the PCB by CPB interconnections. A detailed understanding of failure modes after prolonged reliability test durations and the formation of intermetallic compounds in the solder was gained by failure and component analyses. This work proves, that the replacement of SBs by CPBs on micro acoustic RF filters with a TFAP allows a significant component miniaturization and a reduction in costs still fulfilling the performance and reliability requirements. (* Qualcomm TFAP is a product of Qualcomm Technologies, Inc. and/or its subsidiaries.)      «

Wireless data transmission is already a part in almost every area of daily life. Portable user devices like laptops, smartphones, smartwatches, headphones and many other devices use cellular networks, Wi Fi, Bluetooth, and other standards to wirelessly transmit and receive data. Micro acoustic radio frequency filters (RF filters) are the key components to empower the frequency related wireless communication as they provide good filter performance at reasonable component size. Just as in the enti...     »