Adhesion evaluation of adhesiveless metal/polyimide substrate for MCM and high density packaging
Directly metallized polyimide films are being widely used as advanced high-density packaging substrates. Adhesion of metal to polyimide is a key performance requirement of the film. Excellent initial adhesion and good retention after severe process steps and reliability stresses are required. In this paper, the adhesion performances of films with different types of polyimide and tie layer from multiple vendors have been evaluated. The interface failure mechanisms are also examined via SEM micrographs and XPS survey scans. Peel strength and its retention behaviour are characterized in term of tie layer materials, environmental stresses and surface analysis results. The object of this work is to select the proper base material for high-density flexible multilayer substrates, a technology which is under development by FCPT.
Hydrothermal stability of Cr/polyimide interfaces
The hydrothermal stability of both Cr/polyimide and C75Cr2/polyimide interfaces has been studied using Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and peel testing. It was found that RF sputter treatment of the polyimide surface prior to metal deposition leads to an enhancement of adhesion through chemical bonding of the metal with polyimide. Owing to the enhanced chemical bonding at the interface, failure always occurs cohesively in the polyimide. The RF sputter treatment of the polyimide surface also simultaneously modifies the polyimide underneath the surface. The adhesion strength of the Cr/polyimide interface is degraded significantly upon exposure to high temperature and high humidity (85°C/81% relative humidity, T/H) environment. It is suggested that this degradation results from the hydrolysis of polyimide. The hydrolysis is facilitated by the presence of unstable modified polyimide near the interface. This degradation of adhesion strength can be minimiz...
Polyimide insulators for multilevel interconnections
Abstract Polyimide films are reliable high temperature planarizing insulators for multilevel interconnection systems, which may be the key to high yielding bipolar and MOS very large-scale integrated circuits. In this paper we review the chemical, mechanical and thermal properties of polyimides. The important process steps are traced: planarization by coating, adhesion and patterning both by photoresist masking and by photosensitization of the polymide film. Reliability discussions include the influence of sodium ions on h FE at high temperatures and the effect of water contamination of the starting copolymers on the high temperature stability of the final cured resin. Emphasis is placed on the importance of polyimide adhesion to the substrate in order to retard the metal lead corrosion that occurs at high temperatures and under conditions of moisture. Methods to deal with the higher conductivity of polyimide relative to that of ceramic insulators are summarized.