Residual stress estimation of NCF-bonded COG packages during manufacturing process

Nonconductive film (NCF) is more and more used for chip-on-glass (COG) bonding instead of anisotropic conductive film (ACF), due to its advantages of finer bump pitch and cost reduction. However, the chemical reaction of NCF requires, and experiences show that excessive warpage and residual stress will usually be induced because NCF curing requires higher temperature and bonding pressure than ACF, which is one of the major reliability problems encountered in industry. In this paper, an internal force analysis model of the metal-coated polymer bump is presented, and the effect of bonding parameters on residual stress is investigated, and an improved ZGS´s mechanical model, characterizing various viscoelastic behaviors of polymer, is proposed to estimate the residual stress in metal-coated polymer bumps. After that, the effects of NCF´s material properties and the bonding parameters on the deformation and residual stress distributions are discovered.