Study of Gold-To-Gold Contact Assemblies

Project Number: C95-06

Point of Contact: osterman@calce.umd.edu

Objective

Examine potential reliability issues associated with gold-to-gold compressed contact connections between rigid and flex circuit boards in a stack.
 

Background

Gold-to-gold compressed contact connection have the potential for high usage. The development of reliability assessment models will allow designers and manufactures to understand the effects of design changes and process variations. A proposed assembly of four rigid boards connected with flex using gold-to-gold contact connections poses the following reliability concerns:

• The physical size of the gold contacts;
• Material composition of gold contact (e.g. Gold/Copper-Nickel);
• Characterization of the contact pressure across the assembly;
• Susceptibility to in-plane motion; and
• Effect of thermal and vibrational cycling.

Most of the product design variables that affect part reliability are under the control of the product engineer, but tools are not available to evaluate the reliability of the part in relation to the product design variables and the environmental stresses that the part will encounter.
 
 

Work Accomplished

• Selected a gold bump on flex to gold finger on rigid board connector hold down structure for examination.
• Measured electrical resistance versus load curves between clean gold surfaces.
• Compared two design options for a gold to gold contact connector.
• Performed finite element analysis of the two designs.
• Performed a temperature cycling test to observe potential failure mechanisms for one design alternative.
• Outlined potential reliability problems with the design of gold to gold contact connectors.