BGA (Ball Grid Array) packaging, also known as ball grid array packaging, utilizes an array of solder balls arranged as pins for surface-mounted devices. There are primarily four basic types of BGAs: PBGA, CBGA, CCGA, and TBGA, with solder ball arrays serving as I/O connection points typically located on the bottom of the package. The typical pitch of these packaged solder ball arrays is 1.0mm, 1.27mm, or 1.5mm, with common solder compositions including 63Sn/37Pb and 90Pb/10Sn.
Of course, BGA packaging comes with many advantages, such as more pins, smaller form factors, and improved electrical and thermal properties. However, it’s worth noting that BGA’s drawbacks lie in the complexity of solder joint inspection and rework, with stringent reliability requirements for solder joints, limiting the application of BGA devices in many fields.
Moreover, if a properly soldered BGA proves to be malfunctioning, it needs to be removed from the PCB and replaced without affecting other components that have already been soldered. This is where the star of this discussion comes into play—the BGA rework station.
BGA rework stations are divided into optical alignment and non-optical alignment types. Optical alignment utilizes an optical module with prism imaging, while non-optical alignment relies on manual alignment of the BGA with the aid of PCB silk-screen lines and dots to achieve alignment for rework. For larger BGA components, non-optical alignment is sufficient, as the surface tension of solder paste ensures that even with misalignment up to 50%, the BGA component will still solder into place during reflow soldering. However, for finer and smaller BGA components, relying solely on the naked eye becomes more challenging. Here, we introduce a typical optical alignment principle.
Please note that in the optical alignment principle diagram, the red and blue represent two imaging paths. The solid and dashed red lines represent the imaging paths of the solder balls of the BGA chip to be soldered, while the solid and dashed blue lines represent the imaging paths of the solder pads of the PCB to be soldered. Both images are reflected by the prism mirror into the CCD camera and displayed on the monitor, thereby assisting operators in achieving optical alignment.
BGA rework involves localized heating of the PCB. To ensure soldering without damaging the device due to uneven heating or affecting the soldering of surrounding components, this operation requires not only special design heating hoods on the top but also a PCB preheating device at the bottom. Even so, it’s essential to protect the surrounding components during reheating to prevent re-melting and affecting the quality of previously soldered joints.
The design of the heating hood aims to ensure efficient and effective removal and soldering of BGA components. It consists of inner and outer layers, with the outer layer providing excellent shielding to ensure that the working hot air is not affected by external temperatures, maintaining stable temperature control. The inner layer of hot air flows out through the gap between the inner and outer layers and exhaust holes, ensuring relatively stable airflow during work and minimizing mechanical impacts on the components.
For different BGA devices, variations in thermal performance arise due to differences in pin count and device substrate material, resulting in different rework parameters. Therefore, it’s recommended to strengthen the collection and organization of BGA rework soldering parameters in daily operations to form a valuable database.
