The Effect of Ultrasound on the Gold plating of Silica Nano-particles for Composite Solders

1. The Effect of Ultrasound on the Gold plating of Silica Nano-particles for Composite Solders Timothy J Mason1, Andrew Cobley1, Mohammed Alarjah1, Roya Ashayer2 and Samjid H Mannan2 1 The Sonochemistry Centre, Faculty of Health and Life Sciences,Coventry University, Priory Street, Coventry, CV1 5FB, UK e-mail: a.cobley@coventry.ac.uk 2 Department of Mechanical Engineering, Kings College London Strand, London, UK www.coventry.ac.uk/researchnet/sonochemistry Seeded at 850 kHz, 15 minutes Seeded without Ultrasound 850 kHz, 15 minutes Seeded at 850 kHz, 2 hours Seeded at 1176 kHz, 2 hours 850 kHz, 2 hours 1176 kHz, 2 hours Nano-silica particles (positively charged) (1) (2) Functionalization with a linker Nano-silica particles (negatively charged) Nano-gold particles negatively charged (3) (4) Reduction (5) Gold nucleation sites Gold nanos-hells No Ultrasound Effect of High Frequency Ultrasound on Stage 1 of process Introduction In the modern World electronic devices are expected to function in extreme environments, survive rapid changes in temperature and endure repeated mechanical stress. These conditions put enormous strain on solder joints and can result in fatigue and mechanical failures. One approach to overcoming these problems is the development of composite solders, for example, the dispersion of inert particles into the solder matrix. These particles can modify the grain structure to prevent ‘slippage’ between grain boundaries, inhibit crack propagation and obstruct dislocation movement. This approach does, however, suffer from the issue of how to incorporate the inert species into the solder matrix. Kings College London are developing a process whereby silica nano-particles are coated with a nano-gold ‘shell’ and then integrated into the solder during reflow. Effect of High Frequency Ultrasound on Stage 2 of process Silica nano-particles embedded in solder matrix Original Plating Process • Preparation of nano-silica particles • Functionalization of silica nano-particles • Preparation of colloidal gold nano-particles • Attachment of nano-gold onto silica nano-particles (stage 1) • Growth of gold nano-shell (stage 2) Conclusions • High frequency ultrasound improves the gold ‘seeding’ of the silica • nano-particles particularly at 850 kHz • Silica nano-particles ‘seeded’ at 850 kHz for 2 hours produced almost • a full ‘shell’ of gold. • Ultrasound enhances plating process by: Preventing agglomeration • Improving dispersion • Efficient mixing • Improving adhesion of gold ‘seeds’ by sonochemically forcing them into • the surface of the functionalized silica With the original plating process agglomeration and dispersion cause problems at every stage The Sonochemistry Centre, Coventry University “The Home of Sound Science”