During the initial stages, BGA technology was a matter of concern. People had doubts on solderability and reliability of BGA components. In BGA, the pads are under the device and not visible and hence it is necessary to ensure the correct process of soldering and inspection.
Today, BGA solder techniques is tried and tested and has been proved and trusted to be very reliable. It has also been learnt that once the process is set up correctly, BGA solder reliability is mush higher than that for quad flat packs (QFP) or any other SMD Package.
Reflow Soldering techniques is used to solder BGA. Reflow soldering technique is used to solder BGA because it helps the whole assembly to be brought up to a fixed temperature in order to melt the solder or solder balls underneath the BGA components.
For any BGA soldering, the solder balls on the package have controlled amount of solder. Solder ball in various sizes of 18 mil, 24, mil 30 mil etc are available. When the Board with the solder balls and BGA Package is placed in the reflow oven, it gets heated and the solder melts. Surface tension causes the molten solder to hold the package in the correct alignment with the circuit board. It in important to take care of the composition of the solder alloy and the soldering temperature so that the solder does not completely melt, but stays semi-solid , so that the solder balls stay separate from each other and do not result in any bridging.