As electronics get smaller and smaller, electronic component manufacturers have innovated in order to keep pace. BGAs are one way to increase connection density and keep PCB footprints small.
What is a BGA?
Ball Grid Arrays are a surface mounted integrated circuit that offers many benefits from other IC packages. The usage of balls for leads allows BGA integrated circuits to have a higher pin density along with a lower thermal resistance and inductance. BGA components are able to do very complex functions in a small form factor but they can be tricky to work with without the proper techniques and knowledge.
How is BGA Installed?
These components are installed similarly to other SMT components but there are several differences that need to be taken into account for proper installation. A stencil is first used to apply solder paste to a PCB. Proper placement of the BGA is next which is done by an SMT placement machine or by hand. BGA components have a property where they will self-align as the solder liquifies and hardens which helps with imperfect placement. The component is then heated to connect the leads to the PCB. A mount can be used to maintain the position of the component if soldering is done by hand. If the PCBA is going through a reflow oven, proper precaution to adjust oven settings will ensure good solder connections.
BGA Quality Control methods
Testing of a properly installed BGA can be extremely hard to gauge due to the ball leads being under the IC and not being visible. To address this issue, an x-ray machine is used to catch solder defects. Solder defects that can occur are solder bridges, poor solder weld, solder ball damage, and solder ball oxidation. The issue with x-ray is that most work top-bottom and are only able to show the outline of the solder rather than the cross section. Cross-section x-ray machines are much more capable of showing defects that would otherwise be hidden but can be highly cost-prohibitive. These issues can be rectified prior to the quality control step through proper placement of solder paste and the BGA component along with proper reflow oven settings. Proper care to have all settings correctly applied is essential to saving time reworking BGA chips,
BGA components are notoriously hard to rework due to their leads being on the underside of the package. A proper workstation with tools specific for BGA rework are essential for a success rate of uninstalling and reinstalling BGA components. BGA work stations use an IR heater or hot air to be able to heat up specific components. IR heaters can range vastly from ceramic heaters to IR focused beams. Ceramic heaters do not do a good job focusing heat to one area while IR focused beams are able to properly target one component on a PCB. Hot air uses various nozzles to guide hot air to heat up a component evenly. There is a learning curve with hot air but it can be very effective with BGA rework. A microscope and a mount for the PCBA will be necessary for a technician to properly work on a BGA component. The process of removing and replacing a BGA component uses tweezers, flux, and some form of heat. Heat is applied specifically to the BGA component through whichever method selected while a technician applies flux to the sides of the component. Tweezers are used to lift the component with slight pressure. More flux and heat are to be applied until the solder leads separate from the PCB and the tweezers are able to lift the component off. From there, some balls from the BGA component will still be on the PCB and will need to be removed. This can be done with heat, flux, and desoldering wick. Solder paste can then be applied and a new component can be placed and soldered on. If the same component is to be reinstalled, a reballing machine has to be used to reapply balls.
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