Title :
Thermosonic flip-chip bonding system with a self-planarization feature using polymer
Author :
Tan, Qing ; Schaible, Brian ; Bond, Leonard J. ; Lee, Yung-Cheng
Author_Institution :
Semicond. Product Sector, Motorola Inc., Austin, TX, USA
fDate :
8/1/1999 12:00:00 AM
Abstract :
Thermosonic flip-chip bonding is a wire bonding technology modified for flip-chip assembly. Compared with the soldering technology, it is simpler, faster and more cost-effective. Unfortunately, the yield of thermosonic bonding is low and unreliable because it is difficult to control the ultrasonic energy transmission. A small planarity angle between the bonding tool and stage can result in a nonuniform ultrasonic energy distribution. A self-planarization concept was proposed to solve this problem. A layer of polymer was placed between the bonding tool and the chip to smooth the nonplanar contact. Experimental measurements and finite element modeling were used to study the effect of the polymer layer. Results showed that the polymer layer could assure a uniform ultrasonic energy distribution; however, it also reduced the energy transmission efficiency. A case study for optimization was conducted based on finite element modeling. For a 1000-I/O flip chip assembly with a 250 μm pitch using a bonder with a 0.01° planarity angle, polymer thickness of 350 μm and a Young´s modulus of 2 GPa were selected
Keywords :
Young´s modulus; finite element analysis; flip-chip devices; integrated circuit packaging; lead bonding; polymer films; ultrasonic bonding; 250 micron; 350 micron; Young´s modulus; energy transmission efficiency; finite element modeling; nonplanar contact; nonuniform ultrasonic energy distribution; planarity; planarity angle; self-planarization feature; thermosonic flip-chip bonding system; ultrasonic energy transmission; uniform ultrasonic energy distribution; wire bonding technology; Assembly; Bonding; Finite element methods; Flip chip; Polymers; Semiconductor device measurement; Semiconductor device modeling; Soldering; Ultrasonic variables measurement; Wire;
Journal_Title :
Advanced Packaging, IEEE Transactions on
DOI :
10.1109/6040.784501