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JULY 2026 I SMT007 MAGAZINE 63 the wrong land, insufficient connection, or reduced electrical clearance • Missing or broken balls: Missing or damaged solder balls prior to placement X-ray Inspection Transmissive, real-time X-ray with a tilt function should be used to document several potential defects during BGA inspection. Solder bridges are the most common defect detected by this tech- nique. Gross voids are visible at higher power and magnification levels. Defects such as opens and voids can sometimes be difficult to discern even with high-quality X-ray equipment. Inspection technicians need adequate training to interpret X-ray images and identify all types of defects. In addition, the concentricity, pitch, circu- larity, and solder ball diameter can also be measured as part of the BGA inspec- tion process. With the proper equip- ment, which either tilts the sample or the detector, even head-in-pillow defects can be noted. Endoscopic inspection is a valuable supplemental tool for BGA inspection because it allows inspectors to view beneath the BGA and assess visible solder joint surfaces that may not be fully characterized by X-ray alone. It can help determine whether reflow produced an accept- able joint condition or signs of defects by revealing surface characteristics such as texture, uniformity, smoothness, color, brightness, wetting, and possible micro-cracking. Endoscopes also provide useful documentation through captured images and video, supporting inspection findings, customer review, process improvement, and failure analysis. Conclusion The ability to rework and inspect hundreds of BGA types across a wide range of board designs, using both industry-standard and customer-specific acceptance criteria, is essential. A robust BGA inspection protocol should combine proven X-ray inspection expertise with the latest X-ray tools and techniques to reliably identify the full range of potential BGA defects. It is also important to avoid excessive X-ray expo- sure during inspection, particularly when working with commercial off-the-shelf semiconductor devices, where radiation effects may be a concern. Methods for minimizing the impact of X-ray radia- tion will be discussed in a future column. SMT007 Nash Bell is president of BEST, Inc. To read past columns, click here. Figure 3: Common BGA defects, including cold solder, excessive voiding, misalignment, and missing solder balls. Figure 4: BGA solder bridge between adjacent balls as detected by X-ray inspection. K N O C K I N G D OW N T H E B O N E P I L E