Fig. 3 Bubble expansion process. (a) Illustration of the apparatus
including a 50 mm circular die with epoxy solution deposited on the
top surface, and bubble expansion in gas flow directed upward using
a ring connected to a motor. Wafers are fixed near the bubble for BBF
transfer. (b), (c), (d) Snapshots of the initial, middle, and final stages of
bubble expansion and coating of BBF on two 150 mm wafers.