Many PCB manufacturers have mistakenly delayed the incorporation of Ball Grid Array (BGA) packages into their product designs because of concerns over increased cost and complexity. Incorporating BGAs will not only require additional expenditures in equipment, but will also require additional skills training for employees. The increasing I/O capacity of BGAs and the need to provide more sophistication in less space, has forced many manufacturers to convert to BGA practices or risk losing their competitive advantage. As with any other component package, BGA rework capability is a necessary reality, and must be considered. Some important considerations for successfully reworking BGAs will be examined.Removal Equipment
In selecting BGA rework equipment, some key elements are essential in obtaining versatility, reliability, and repeatability. Equipment available for BGA rework should incorporate the use of a split-vision alignment system to ensure the exact alignment of the component to the substrate. There should also be a programmable localizer reflow system, preferably one that uses hot-air convection while providing underside heating to ensure the correct reflow of the BGA. Some typical examples are the
standard "hot gas" method, the sealed oven method, the horizontal flow method, and the conduction method. Also required will be an assortment of tools including a solder wick, a soldering iron with a wide chisel tip, and a micro-stencil for the application of solder paste if necessary. Finally, one very important factor in successful rework of any BGA begins in the design stage of the assembly. Ensuring enough free area (“keep-out distance”) around the periphery of the BGA is important to provide enough clearance for rework tooling and fixturing. In most cases, a "keep out distance" of 0.100in. is sufficient.