Adhesive Properties of Siloxane Modified Polyimides and Application for Multi-Layer Printed Circuit Boards

The adhesive properties of various siloxane modified polyimides were studied for the development of suitable adhesive materials with good thermal stability. Their adhesive properties were influenced by siloxane content in the polymer backbone and the structure of the aromatic component. Among them, the copolyimides with small amounts of the siloxane unit showed the better lap shear strength compared with the corresponding all-aromatic polyimides. They had excellent adhesive strength to various substrates. Their adhesive durability under the highly humid condition (25°C, 90%RH) was also improved mainly due to their lower moisture sorption and lower moisture permeability. However, further siloxane modification lowered their adhesive strength and durability. On the other hand, thee T-peel strength of copolyimides was lowered according to the increase of siloxane content. Based on this study, a new type of adhesive film which was composed of a copolyimide as a major component, SPB-505A, was developed and reported. This is useful for multi-layered printed circuit boards due to the excellent adhesive properties, good electrical properties and distinguished reliability under the hot / wet condition (121°C, 2 atm, 85%RH).