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36 SMT007 MAGAZINE I JULY 2025 Hot air rework: Uses a stream of hot air to heat the BGA and PCB uniformly, enabling solder melting and package removal (Figure 1). While effective, this method requires careful mana- gement to prevent heat damage to adjacent components. Infrared (IR) rework: Employs IR emitters to target the BGA directly, minimizing thermal impact on the surrounding areas. Calibration is crucial for achieving even heating. Vapor phase rework: Involves placing the PCB in a vapor-filled chamber that provides uniform heating. This method offers excellent thermal management but can be cost-prohibitive for high-volume applications. Laser rework: Uses focused laser beams for precise heating, allowing selective reflow while minimizing damage to adjacent components. This technique requires a significant investment in specialized equipment. Precision milling: Primarily for removing underfilled components. This process employs high-precision equipment to remove the BGA one layer at a time. While this method destroys the component, it enables subsequent placement at the same location and reduces the risk of pad damage. Equipment and Skill Requirements Modern BGA rework demands sophisticated equip- ment with precise placement capabilities and highly skilled technicians to operate these systems effec- tively. Inadequate equipment operation or techni- cian inexperience can lead to defects and rework failures. To mitigate these issues, investing in advanced, programmable rework systems with pre- cise temperature and alignment controls is essen- tial, along with continuous training programs to keep technicians proficient in developing technol- ogies. Combining top-tier tools and ongoing skill development enhances the reliability, accuracy, and overall success of BGA rework processes. Typical BGA Rework Challenges BGA rework carries inherent risks that can com- promise the quality and functionality of electronic assemblies. The complexity of handling BGA com- ponents, along with the precision required for effective soldering, increases the chances of mis- alignment, solder defects, and thermal damage. Issues such as PCB delamination, cracking of the BGA packaging, and damage to adjacent compo- nents may arise from improper rework techniques or inadequate thermal management. Additionally, the introduction of contaminants during the rework process can jeopardize solder joint integrity. Below is an overview of the six commonly encountered challenges that occur during BGA rework: Adjacent Device Damage When reworking a BGA, it is crucial to assess the surrounding components, especially those nearby or on the opposite side of the PCB, as they can be affected by heat expo- sure during the process. Sensitive components like capacitors, crystals, and plastic parts are at risk of damage from improper heat, making precise tem- perature control, targeted heating, and strategic cooling essential. Using physical barriers or heat shields helps protect vulnerable areas. Selecting the right heat source, nozzle, and employing pre- heating techniques ensures uniform heat applica- tion, reduces thermal stress, and minimizes dam- age such as warpage or pad lifting. Careful process planning and control are vital to maintaining the integrity of the assembly throughout the rework. Large BGAs As larger BGA packages up to 125 mm x 125 mm become common, they introduce significant rework challenges due to the limitations of existing systems, such as inadequate alignment with split vision prism technology and insufficient bottom heaters, which can cause uneven heating and damage. Maintaining consistent temperature across large surfaces is difficult, with airflow turbu- lence and IR systems often lacking the appropri- ate spot size for uniform heat application. To over- come these challenges, technicians can employ custom supports, utilize stay-in-place stencils, and optimize thermal profiling. These measures enhance stability, improve soldering quality, and increase process reliability for larger BGA rework, even within system constraints. 1 2 1 2 3 4 5