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AUGUST 2026 I SMT007 MAGAZINE 47 the solder joints reach reflow temperature without overheating exposed surfaces. Importance of Thermal Profiling Regardless of whether hot air or infrared is used, a validated thermal profile is essential to ensure the solder joints reach reflow temperature without over- heating the component, PCB, or surrounding parts. With hot air systems, the profile focuses heavily on nozzle temperature, airflow, bottom-side preheat, and the temperature difference between the component and PCB. Infrared profiling requires additional attention to surface color, emis- sivity, reflectivity, component height, and line-of- sight exposure because these factors can cause different areas to absorb radiant heat at different rates. Thermocouples should be placed at critical locations to confirm actual temperatures rather than relying only on the machine's programmed heater settings. K N O C K I N G D OW N T H E B O N E P I L E Figure 3: Thermal profiling during BGA rework uses thermocouples at critical locations to verify component, PCB, and bottom-side temperatures throughout the heating cycle. Selecting the Appropriate Rework Method Both hot air and infrared systems can produce reli- able BGA rework results when properly applied and thermally profiled. Hot air is generally preferred for localized, predictable heating, while infrared may be advantageous for broader, airflow-free heating or improved production efficiency. The most appro- priate method depends on the component construc- tion, PCB thermal mass, surrounding layout, surface finishes, and production requirements. Ultimately, successful rework depends less on the heating technology itself and more on controlled heat delivery, accurate temperature monitoring, and a repeatable process. SMT007 Nash Bell is president of BEST, Inc. To read past columns, click here.