TABLE OF CONTENTS Much of the remainder of this chapter focuses on the use of basic statistics and problem-solving methods that can be used to improve the quality of microelectronics packaging manufacturing processes. In this context, the term quality can be defined loosely as fitness for use. From the point of view of manufacturing, the most relevant aspect of quality is quality of conformance, or how well manufactured products conform to the specifications and tolerances required by their design and intended use. Every packaging product possesses a number of elements which collectively describe its fitness for use. These elements are referred to as quality characteristics.
Perhaps the major barrier to perfect quality in a manufacturing process is variability. Variability is inherent in every product, and no two products are ever identical. For example, the dimensions of two thin metal films used for interconnection on a packaging substrate will vary according to the precise conditions and equipment used to deposit and pattern the films. Small variations might have negligible impact on the final product, but large variations can lead to final products which are unacceptable. Quality improvement may be defined as the reduction of such variability in processes and products. Since variation can only be described in statistical terms, statistical methods are necessary for quality improvement efforts.
Statistics allow decisions to be made regarding a process or population, based on the analysis of a sample from that population. For example, two well-known statistics are the sample average and sample variance
