PROCESSING AND RELIABILITY OF HIGH PERFORMANCE FLIP CHIP ON FLEX MODULES
Authors: Daniel F. Baldwin, Ph.D., Jennifer Muncy, Paul Houston and Brian Lewis Company: Georgia Institute of Technology Date Published: 1/17/2006
Pan Pacific Symposium
Abstract: Over the last several years, high density flexible substrates have been introduced into high performance electronics applications. These high density substrates have found a good match with a number of commercial, military and medical applications. A key advantage of the flex circuits is their ability to route high IO density devices with lines and space capability down to 20 µm. Flex circuits also offer impedance matching for high performance designs and a significant weight reduction over rigid high-density microvia circuit boards. Another significant advantage of high density flex circuit assemblies is their ability to conceal form and function while maintaining the appearance of conventional packages. As with any new technology, there are challenges that arise in processing, reliability testing, material selection, and fixturing flex circuits during assembly. One of the main assembly issues with flex circuits is warpage due to the CTE mismatch between the laminated materials and non-uniform heating of the substrate. The goals of this research were to investigate out of plane deformation of a flip chip on flex assembly during reflow, evaluate locating principles and fixturing strategies for flip chip on flex assembly, and assess the reliability of a flip chip on flex TBGA package construction. Additional examples of flip chip on flex system in package modules are also discussed including a digital multi-flip chip module with 0201’s and CSPs for a high speed computing application, a large area 200+ element flip chip on flex panel for military surveillance, a high speed flip chip on flex optoelectronic module, and a implantable retina incorporating flip chip on flex assembly.