Micro Cold Spray Direct Write Process

Abstract

Gas dynamic cold spray was first discovered in the 1980s and has since been used as a surface coating process for depositing metals, metal-ceramic composites, metal-carbon nanotube composites and other composite materials onto both flexible and rigid substrates. We recently developed a focused cold spray material deposition tool termed Micro Cold Spray (MCS). MCS is a direct-write tool applicable for printed electronics and has been used to print conductive trace patterns as thin as 50 μm wide using copper, aluminum and tin micro powders. Unlike conventional aerosol processing at 10–100 m/s, aerosol particles in the MCS process are accelerated to speeds greater than 500 m/s. In this paper the possibility to accelerate, focus, collimate, and deposit aerosol particles is theoretically explored using a finite difference approximation method to simulate the flow of Helium through a symmetric converging-diverging nozzle of throat diameter 200 μm. A Lagrangian particle tracking algorithm is used to calculate the particle trajectories and corresponding velocities. This paper presents a comparison of the effect of Stoke’s drag force and Saffman’s lift force on the trajectory and velocity of copper particles 3 μm in diameter.