TABLE OF CONTENTS J. Donald Gardner
Northrop Grumman Corporation
Linthicum, Maryland
Metals offer a wide variety of physical and mechanical properties for use in the electronics and electrical industries. Because of the demanding requirements on materials in electronic equipment, many trade-offs have to be made in selecting metals. Electrical conductivity must often be reduced to increase strength, while strength is sometimes reduced to obtain a target thermal expansion. These are only two simple trade-offs made in electronic design. Often, the selection involves even more mechanical and/or physical properties along with decisions on economics and manufacturability.
The process of materials selection involves consideration of the functional requirements with respect to physical and mechanical properties. Feasibility and economics of manufacturing will always be a part of the equation. It does little good to select a material with optimal mechanical properties if the material cannot be fabricated into the desired shape at the required cost. The total design job requires consideration of all the factors of functional material properties and manufacturing processes. Some of the detailed factors to be considered are discussed below.
Chemical composition is the most commonly specified criterion for metals. This determines the basic mechanical properties and physical characteristics of the metal. Fabrication method and heat treatment will influence these properties, but the chemical composition provides fundamental characteristics. Many metals, such as aluminum and titanium, are used in essentially their pure state, with minor impurity elements. Addition of other elements...
