Conclusion Heating of the solder joints on BGA packages occurs primarily by thermal conduction through the body of the package and through the substrate. Direct convection heating effects only the perimeter balls. Construction materials can cause different thermal response between package styles during reflow. Specific BGA package styles should be evaluated by actual profile tests. Initial appearances may not be accurate in evaluating the thermal response of a specific style.
Thermocouple attachment is critical.
Solder joints at the center of the package must be profiled by drilling through the substrate. Substrate construction under BGA packages can also influence heating characteristics and should be evaluated.