Surface morphology and residual stress of electroplated and electroless copper deposits

Abstract

In this work, surface morphology characterisation and residual stress measurements have been carried out on electroplated and electroless copper deposits. The surfaces of the solution and substrate sides of the freestanding electroplated copper deposits from stainless steel substrates have been studied at as-deposited condition and after heat treatment at 140°C for 1 hour. Electroless copper deposits with different substrates (copper cladded and laminated polymers, and screen-printed dielectric substrate) have also been studied at the two conditions. The surface morphology has been characterised using optical microscopy and scanning electron microscopy (SEM). Residual surface stress measurements were performed using the sin2Ψ technique of X-ray diffraction method. The morphology of the as-deposited electroplated copper film on the substrate side includes numerous small voids scattering across the surface of the deposit, with relatively large cracks at some portions. No voids were observed in the deposit on the solution side. These features remained after heat treatment. In the electroless copper deposits, the granular particles developed on the heat-treated deposit were the most intensive, followed by the deposits on the laminated and on the copper cladded substrates, respectively. No significant amount of residual surface stress has been detected in the as-deposited electroless copper deposits.