Ultra low CTE (0 PPM/C) polyimide film and its potential application

A CTE gap between a silicon chip and a package substrate is one of the most critical issues in securing reliability for a high-density packaging. We succeeded in a development of a new thermally stable and ultra low CTE polyimide film . The CTE is lower than that of silicon in a wide temperature range. A thick laminate sheet, with the thickness of 250 to 500 micrometers, composed with this ultra low CTE polyimide films shows low CTE as well. Since the sheet can be easily processed by machine cutting or laser drilling with a high aspect ratio, it is highly expected to perform as a core material for a thermally- reliable package substrate. Along with the role of core material, this polyimide film is able to be applied as a dielectric material for wiring layers as well. This paper describes possible applications of this film in a package substrate with early test data of thermal cycle stress.