Development of an Ultralong Ultralow n-Loop for Wire Bonding

In this paper, we describe an innovative method to form an ultralong ultralow loop for wire bonding. A resister was used to form kinks and simplify the capillary trace, which yielded a loop-like “n”-shape with two kinks immediately above the first and second bonds that can support the entire long-span loop. A 3-D finite element model was developed to simulate the n-loop formation, and the loop profiles of an n-loop, M-loop, and standard loop were compared. In this paper, we show that this novel n-loop can almost halve the looping time compared to that for the M-loop; and the n-loop can avoid wire sag for a 5000-μ m-long span. Furthermore, the loop height and wire verticality near the second bond can be modified by regulating the horizontal and vertical positions of the resister.