Electrocodeposition of nanoparticle composite films using an impinging jet electrode

An impinging jet electroplating system with controlled hydrodynamics for rapid plating of composite films, was designed, developed, built, and tested. The resulting system enabled electrodeposition with flowrates from 0.5 LPM to 7.0 LPM, current densities of 25 mA/cm2 to 200 mA/cm 2, and particle loading from 20 to 120 g/L. Electrocodeposition of a copper matrix from a 1.0 M CuSO4 + 1.2 M H2SO 4 bath from kinetically controlled to mass transfer limited conditions with a 50 nm gamma-alumina and 1 mum alpha-alumina particles was studied. The resulting particle incorporation ranged from 0.5 up to 7.0 wt% depending on operating conditions. The maximum particle incorporation of 7.0 wt% for 50 nm gamma-alumina was deposited at 2.5 LPM, 25 mA/cm2, and 120 g/L particle loading. The maximum particle incorporation for 1 mum alpha-alumina of 5.3 wt% was deposited at 2.5 LPM, 200 mA/cm2, and 120 g/L particle loading. Particle incorporation increased linearly with increasing particle loading for 50 nm gamma-alumina. The structure of the deposits was analyzed by electron microscopy, which determined average grain sizes as small as 175 nm for a composite film with 50 nm gamma-alumina particles deposited with a current density of 200 mA/cm2. Imaging with a backscatter electron detector showed a random distribution of particles in the deposited films. The resistivity of the deposited films was measured with a maximum resistance of 0.21 muO was measured for a sample with 2.2 wt% 50 nm alumina incorporation with 175 nm average grain size. This was a 75% increase in resistance compared to a pure copper electrodeposited film.