Wire Sweep Improvement for Tuning Wires in RF Power TO288 Packages

Abstract

RF Power packages have complex bonding diagram (BD) with high loop and long length of tuning wires which are very critical to achieve the resonance frequency of the device. The high loop and long length of tuning wires are very sensitive to wire sweep occurrence after molding process. Lately, the RF Power devices are becoming more complex with additional tuning wires and ground wires [1]. The height of tuning wires plays a critical role to ensure proper efficiency of the device at the same time prone to wire sweep at molding process. During initial startup of the RF Power devices, pre sway was implemented at wire bond (WB) process. The tuning wires are swayed 3° so that after molding the wires will be sweep by the mold compound flow into the package and eventually the wires will be become straight after molding [2]. However, the latest RF Power TO288 package has longer tuning wires up to 180mils and tuning wire height up to 60mils [1]. The pre sway at wire bond cannot be applied as wire bonders do not have the capability to perform pre-sway for such a long and high loop wires. Due to limitation at WB, mold process has to find strategies to minimize the wire sweep occurrence. This particular paper discusses how molding process have optimized their molding parameters to minimize the wire sweep occurrence. This paper will give a complete summary of wire sweep improvements done for RF Power TO288 package in terms of process optimization and mold gate location. The learnings of RF TO288 wire sweep study was implemented to upcoming RF packages.