Wire bond encapsulant control method

Abstract

A method of depositing encapsulant on a line of wire bonds to a die is described, the die having a back surface in contact with the support structure and an active surface opposing the back surface, the active surface having electrical contact pads and functional elements spaced from the contact pads. The method involves the steps of providing a die mounted to the support structure, positioning a barrier between the contact pads and the functional elements, the barrier being proximate to, but spaced from the active surface, depositing a bead of encapsulant onto the electrical contact pads while the barrier remains stationary such that the barrier prevents the encapsulant from contacting the functional elements, removing the barrier when the bead of encapsulant has been deposited. The fluidic resistance generated by the gap between the barrier and the active surface means that the amount of encapsulant that flows into the gap and onto the active surface is almost constant. The reduced flow variations make the encapsulant front closely correspond to the shape of the barrier. Greater control of the encapsulant front allows the functional elements of the active surface of the die to be closer to the contact pads.