This provided a longer soak time, which allowed the BGA to achieve a temperature closer to the other components before entering reflow. The final profile, summarized in Table 4, allows all of the solder joints at all locations on the BGA package to achieve adequate soldering time and temperature with only a slight increase in the hottest 0805 chip. Component Location Peak Temp. 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.