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64 SMT007 MAGAZINE I SEPTEMBER 2025 K N O C K I N G D OW N T H E B O N E P I L E Component Removal Component removal must be performed with pre- cision using a controlled heat source to preserve device integrity. The primary methods are hot air rework systems and infrared (IR) rework systems. • Hot air systems: These deliver a directed stream of heated air to raise both the com- ponent and the surrounding PCB to solder reflow temperature. Operators must carefully manage airflow, temperature, and dwell time to prevent thermal damage or PCB warp- ing. Preheating the board before removal reduces thermal shock and helps maintain component reliability. • Infrared systems: These radiate heat directly into the component, minimizing thermal exposure to nearby devices. However, this method is dependent on component color, reflectivity, and board material. Precise calibration and thermal profiling are critical to avoid overheating or incomplete reflow. Regardless of the method, adherence to mois- ture sensitivity device (MSD) handling procedures per IPC-J-STD-033 is essential to prevent com- ponent failure. In addition, thermal profiling must be performed to ensure heating remains within manufacturer-recommended specifications. When selecting a rework system, operators should evaluate several factors in advance: • Is the PCB itself to be preserved, or is it scrap? • Will the PCB thickness present challenges for achieving proper reflow? • What materials and characteristics does the component have? Answering these questions helps determine which rework method will deliver the best results with minimal risk. Component Reconditioning Once removed, components must be reconditioned to restore leads, pads, or solder balls and prepare them for reuse. This can be performed manually or using robotic hot solder dip (RHSD) systems, particul- arly for ball grid array (BGA) devices. Reconditioning typically involves removing the original solder balls to expose the interposer pads, cleaning and prepar- ing the pads to remove oxidation, accurately placing new solder balls, and performing controlled reflow and cooling. Nitrogen-assisted reflow is often recommended for high-reliability applications. C o n s i d e rat i o n s fo r S a l va g e Rewo r k Syste m s Feature/Consideration Hot Air Rework Systems Infrared (IR) Rework Systems Heating Metho d C ontrolle d stream of hot air IR emitters radiate heat dire ctly into the c omp onent Heat Distribution Uniform heating of the component and PCB Lo calize d heating minimizes impact on adjac ent c omp onents B est Use Cases General-purp ose removal; c ompatible with most PCBs D ense b oards; near heat-sensitive dev ic es; tight thermal toleranc es Pro c ess C ontrol Re quires airflow, nozzle, and dwell time management Re quires pre cise calibration; c omp onent c olor and refle ctiv it y affe ct results Risk Factors PCB warping or overheating of nearby parts Uneven IR absorption; refle ctive surfac es may re duc e efficiency Preheat Re quirements Often b enefits from PCB preheating Re c ommende d for thick or multilayer PCBs Equipment C ost Lower initial c ost Often higher b e cause of pre cision c ontrols O p erator S kill Level Mo derate to high High: re quires knowle dge of IR absorption and profiling MSD Pre cautions Follow J-STD-033; pre-bake high-MSL dev ic es Same as hot air; pre-bake high-MSL devices