Correlating Circuit Board Deflection/Strain Measurements to BGA Solder Joint Dynamic Performance

Summary form only given. BGA solder joint reliability under flexure and shock environment is one of the main concerns for the electronic packaging industry. Direct stress measurement of solder joints for a BGA assembly in a dynamic impact event is not available at this time. However, many studies have clearly shown that BGA solder joint failure is more directly related to board deflection / curvature than acceleration. Furthermore, the mode in which the board deforms is an important factor. Board deflection and strain measurement has been adopted by the industry to indirectly correlate solder joint stress which cannot be directly measured. To investigate the correlation between board strain measurements and solder joint capability, a board "strain states" method is introduced. This method has proven indispensable in determining the root cause of dynamic failures, comparing design variation to achieve lowest solder joint stress and matching shock profile response between BGA package test vehicles and fully assembled boards and systems. This paper provides theory and specific examples on how the method is applied to a variety of real life scenarios. The examples will illustrate the use and interpretation of board deflection and strain measurements as applied to evaluation of electronic packaging under a dynamic bending event. This paper also discusses the FE model validation based on board deflection and strain measurements across the circuit board