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This paper illustrates the influence of Au addition on the phase equilibria of Sn-Ag-Cu (SAC) near-eutectic alloys and on the interface reaction with the Cu substrate. From the thermal and microstructural characterization of Sn-3.8Ag-0.7Cu alloys containing various amounts of Au, it is found that the Au promotes the formation of a quaternary-eutectic reaction at 204.5°C Ϯ 0.3°C. The equilibrium phases in the quaternary-eutectic microstructure are found to be AuSn 4 , Ag 3 Sn, βSn, and Cu 6 Sn 5 . While the addition of Au to Sn-3.8Ag-0.7Cu alloys is also found to increase liquidus temperature and the temperature ranges of the phase equilibria field for primary phases, such influences from Au are found to be less pronounced when the alloys were reacted with the Cu substrate. Because of the formation of the Au-Cu-Sn-ternary interface intermetallic, it is found that a majority of Au added to the solder is drained from the melt. The drainage of Au reduces the impact of Au on the phase equilibria of the solder alloys in the joint. It is further found that the involvement of Au in the interface reaction results in a change of the interface phase morphology from the conventional scallop structure to a compositelike structure consisting of (AuCu) 6 Sn 5 grains and finely dispersed, βSn islands.

Embedded passives provide a practical solution to microelectronics miniaturization. In a typical circuit, over 80 percent of the electronic components are passives such as resistors, inductors, and capacitors that could take up to 50 percent of the entire printed circuit board area. By integrating passive components within the substrate, embedded passives reduce the system real estate, eliminate the need for discrete components and assembly of same, enhance electrical performance and reliability, and potentially reduce the overall cost. Moreover, it is lead free. Even with these advantages, embedded passive technology is at a relatively immature stage and more characterization and optimization are needed for practical applications leading to its commercialization. This paper presents an entire process from design and fabrication to electrical characterization and reliability test of embedded passives on multilayered microvia organic substrate. Two test vehicles focusing on resistors and capacitors have been designed and fabricated by Packaging Research Center (PRC) and Endicott Interconnect Technologies (EI). Resistors are carbon ink based Polymer Thick Film (PTF) andNiCrAlSi, and capacitors are made with polymer/ceramic nanocomposite material. High frequency measurement of these capacitors was performed. Furthermore, reliability assessments of thermal shock and temperature humidity tests based on JEDEC standards are presented.

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