A3: Wire Bonding Fundamentals
Instructor: Lee Levine, Process Solutions Consulting
(*NEW TIME: 10:30am-12:30pm*)
With more than 15 trillion wire bonds produced annually and volume still growing the reliability and productivity of wire bonding makes it one of the most reliable processes in manufacturing. But that does not mean that rigorous attention to details can be ignored. New products must be fully qualified and periodic testing of the weld intermetallic is an important part of assuring high quality bonds. Process changes, materials changes and tool changes must all be tested and reliability confirmed. Long-term aging studies using accelerated high temperature storage, thermal cycling and temperature/humidity tests are not only initial qualification requirements but should be a part of any review when materials s and encapsulation changes are required.
Mechanical testing of wire bonds is normally performed on every lot, at shift changes and if a tool is changed. Pull testing of wire bonds is the most common test performed. The mechanics of the pull test is based on simple resolution of forces but using the pull test to control the process must be done with an understanding of the mechanics. It is not unusual for companies to miss poor bonds because they fail to understand the mechanics and use the pull test incorrectly. A macro-scale model will be used to model the pull test and explain where problems can be missed during standard test procedures.
The shear test provides a good measure of the strength of the intermetallic weld. The use of the shear test for optimizing wire bond process parameters is common. Designed experiments provide good understanding of the effect of process parameters on the bond quality. Shear strength requirements, testing and interferences will be discussed.
Ultrasonic welding is an aggressive process that allows large scale deformation of the ball and wire at much lower temperature and force than would be possible without ultrasonic assistance. However, some wire bond failure modes such as cratering and cracking of interlayer dielectrics in multi-layer die are very sensitive to ultrasonic energy. A discussion of these failures, how to detect them and the effect of bond parameters on these failures will be discussed.
Who Should Attend?
Wire bond process engineers, technicians, quality control engineers and managers should take this course.
Lee Levine is a consultant for Process Solutions Consulting, Inc. where he provides process engineering consultation, SEM/EDS analysis, and wire bond training. Lee’s previous experience includes 20 years as Principal and Staff Metallurgical Process Engineer at Kulicke & Soffa and Distinguished Member of the Technical Staff at Agere Systems. He has been awarded 4 patents, published more than 70 technical papers, and has won both the John A. Wagnon Technical Achievement award and the Daniel C. Hughes award from the International Microelectronics and Packaging Society (IMAPs). Major innovations include copper ball bonding, loop shapes for thin, small outline packages (TSOP and TSSOP, and CSPs) and introduction of DOE and statistical techniques for understanding semiconductor assembly processes. He is an IMAPs Fellow and a senior, life member of IEEE.
Lee is a graduate of Lehigh University, Bethlehem, Pa where he earned a degree in Metallurgy and Materials Engineering.