Coating and Process to Minimize Water Adsorption on Polyimide Laminate
Original Publication Date: 1978-Mar-01
Included in the Prior Art Database: 2005-Feb-20
Composite laminates of polyaramide fiber (such as KEVLAR 49*) and polyimide can be used as a replacement for metallized ceramic or multilayer ceramic substrates. Integrated circuit chips can be attached to this laminate by the solder reflow, flip chip process. The ability to continue to match the expansion coefficient of the integrated circuit chips is imperative, as then the fatigue life of the solder joints is not a design factor, although polyaramide fiber-polyimide composite laminates can be made which initially match the expansion coefficient of integrated circuit chips in the X-Y plane, the expansion coefficient of the laminate increases with loss of water. This phenomenon is clearly shown by the difference in expansion coefficients on two consecutive heating cycles. The process that overcomes this problem is: 1.