ORIGINAL ARTICLE The influence of Fe 2 O 3 nano-reinforced SAC lead-free solder in the ultra-fine electronics assembly F. Che Ani 1,2 & A. Jalar 2 & A. A. Saad 3 & C. Y. Khor 4 & R. Ismail 2 & Z. Bachok 3 & M. A. Abas 3 & N. K. Othman 5 Received: 14 August 2017 /Accepted: 8 January 2018 # Springer-Verlag London Ltd., part of Springer Nature 2018 Abstract This paper presents the influence of Fe 2 O 3 nanoparticles on the microstructure and fillet height for the ultra-fine electronics assembly in the reflow soldering process. Lead-free SAC solder paste was reinforced with different weighted percentages of Fe 2 O 3 nanoparticles (i.e., 0.01, 0.05, and 0.15 wt.%) using a mechanical solder paste mixer. A new form of nano-reinforced lead- free solder paste was applied to assemble the ultra-fine capacitor (i.e., 01005 size) onto the printed circuit board by applying the reflow soldering method. Focused ion beam (FIB), high-resolution transmission electron microscope (HRTEM) system equipped with energy-dispersive X-ray spectroscopy (EDS), field emission scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (EDS), and nanoindentation tester, were all used to examine the microstructure, hardness, and the fillet height of the solder joints. The experimental results revealed that nano-reinforced solder with the content of 0.01, 0.05, and 0.05 wt% yielded small changes in the intermetallic layers. Furthermore, applying an increment of Fe 2 O 3 to 0.05 wt% also improved the fillet height. The mechanism of the agglomeration of Fe 2 O 3 in the bulk solder is discussed in this study. Moreover, simulation analysis using the volume of fluid (VOF) and discrete phase method (DPM) was both employed to describe the mechanism of nanoparticle distribution in the solder and the reflow soldering process. The findings are expected to provide profound knowledge and further reference towards the reflow soldering process of the miniaturised electronic package. Keywords Fe 2 O 3 nanoparticle . SAC305 . Nano-reinforced lead-free solder . Ultra-fine package 1 Introduction Portability and compact design of electronic devices continue to be the current trend attracting more and more users. The miniature IC package and components (e.g., capacitor and transistor) within a device are designed to fit into a confined space. The strength of the interconnect or solder joint is there- fore necessary and important to ensure that the device func- tions correctly as specified. Thus, the miniature IC package and the passive component, thereby, demand reliable solder joints to maintain performance and overall product reliability and user satisfaction. Many scholars have carried out investi- gations and studies to enhance the material, mechanical, and thermal properties of the lead-free solder using numerous types of ceramic or metal-based nanoparticles added to lead- free solder [1]. Various lead-free solder materials such as Sn- 3.5Ag-0.7Cu (SAC), SnAg, SnCu, and SnZn are commonly used to combine with several types and sizes of nanoparticles. The presence of different nanoparticles in solder material will alter solder properties and characteristics. For example, doping of aluminium oxide (Al 2 O 3 )[2], zirconia (ZrO 3 )[3], and rhodium [4] in lead-free solder content will slightly alter the melting temperature when compared to non-doping and pure solder material. Also, other types of nanoparticles such as NiO [5], Fe 2 NiO 4 [6], diamond [7], and TiO 2 [8] are also used to strengthen the microstructure and mechanical properties of * F. Che Ani fakhrozi_cheani@jabil.com 1 Jabil Circuit Sdn Bhd, Bayan Lepas Industrial Park, Phase 4, 11900 Bayan Lepas, Penang, Malaysia 2 Institute of Microengineering and Nanoelectronics, Universiti Kebangsaan Malaysia, 43600 Bangi, Selangor, Malaysia 3 Advanced Packaging and SMT Unit, School of Mechanical Engineering, Universiti Sains Malaysia, 14300 Nibong Tebal, Penang, Malaysia 4 Faculty of Engineering Technology, Universiti Malaysia Perlis, Level 1, Block S2, UniCITI Alam Campus, Sungai Chuchuh, 02100 Padang Besar, Perlis, Malaysia 5 School of Applied Physics, Faculty of Science and Technology, Universiti Kebangsaan Malaysia, 43600 Bangi, Selangor, Malaysia The International Journal of Advanced Manufacturing Technology https://doi.org/10.1007/s00170-018-1583-z