Using removable spacers to ensure adequate bondline thickness

Abstract

A method is provided for die bonding a semiconductor device to a substrate, which method provides adequate and consistent bondline thickness and assures that the die is spaced from the substrate a predetermined amount. Embodiments include removably attaching a flexible spacer of a predetermined thickness, such as a strip of paper or plastic, to the bonding pad of a substrate, such as an organic lead frame, so that it partially covers the bonding pad while leaving other parts of the bonding pad exposed. Die attach material, such as epoxy paste, is then applied to the exposed areas of the bonding pad, and a die is placed over the bonding pad in contact with the epoxy and the spacer. Due to the presence of the spacer, the die cannot sink when it is placed on the epoxy paste, resulting in a consistent bondline thickness equal to the spacer thickness. Thereafter, the epoxy paste is cured and the spacer removed, leaving a gap between the die and the lead frame of the predetermined spacer thickness, which is underfilled with plastic encapsulant material when the die is encapsulated. Thus, an ideal bondline thickness is consistently achieved, improving reliability at minimal additional cost, and no additional materials are introduced into the finished device which could adversely affect reliability.