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72 SMT007 MAGAZINE I JULY 2024 materials is reduced, which in turn lowers the environmental impact associated with manufacturing and disposing of electronic parts. is practice helps in minimizing electronic waste, promoting a more sustainable approach to electronics production and consumption. • Technological failures oen involve the separation or cracking of BGA balls, leading to poor electrical connections between the BGA and the PCB substrate. ese issues are mainly caused by mismatched coefficients of thermal expansion (CTE) between the BGA and the PCB, as well as mechanical, material fatigue, and thermal stresses on the assembled board. e balls at the edges of the BGA package are particularly susceptible to cracks. Of course, there are other applications in which BGA re-balling makes sense, such as defense/aerospace sectors and R&D work. In industries like defense and aerospace, designs that use Pb-based soldering are oen required to continue using the same well-established technology and materials. If the BGAs used have been manufactured with ROHS- compliant materials, they must be converted to Pb-based ball materials. Conversely, there may also be a need to convert from Pb to ROHS- compliant ball materials. Meanwhile, research and development centers, where numerous proof of concept (POC) designs are often developed, may want to reuse expensive BGA components. Re-balling provides a straightfor ward and cost-effective way to enable this reuse. Main Techniques for BGA Re-balling ere are several techniques for BGA re-balling widely used in the industry. e three most common ones are: • Manual stencil placement: is method uses a small, dedicated stencil to accurately position the balls on top of the de-balled package. • Robotic ball placement with laser soldering: In this technique, a robot places the balls and then uses laser soldering to secure each ball individually. • Robotic ball placement with reflow: is technique involves robotic dispensing of flux selectively, followed by robotic placement of balls, and finally, a reflow process to solder the balls to the package. e manual re-balling process, which involves the use of a small stencil mask, is time-consuming and has a lower probability of successfully completing the BGA re-balling process. e main types of defects in the manual process are: 1. Missing balls: As part of placing the balls through the mask, a few balls may be missed. 2. Misalignment of balls: Inaccurate manual alignment can lead to balls being misaligned by the grid. Figure 1: Breakdown of the BGA package.