Testing BGA Devices
BGA devices differ from normally-packaged devices in that all of their external connections are made through balls of solder between the bottom face of the device and the circuit board rather than through pins protruding from the side of the device.
The testing of circuits containing BGA devices has been one of the driving forces in popularising JTAG testing. With the connections between the device and the circuit board no longer accessible and visual inspection being equally affected, the only non-JTAG form of testing that can provide any form of useful information is X-ray inspection. This costly and time-consuming process requires that each board be X-rayed and the images inspected to check each solder ball has been correctly placed and the contact between the board and the device is intact but has not spread to cause short circuits. This process, while providing some information, still relies on visual inspection, whether manual or automated, and consequently cannot be fully relied upon to locate all errors.
Under these circumstances, JTAG connection testing has moved from being a useful alternative to bed-of-nails testing to a significant money-saving tool that eliminates the need for costly X-ray technology.
With XJAnalyser, you can see the values and properties of all the pins on your JTAG-enabled BGA devices in real time. Using XJTAG to test your circuits means that you can treat leaded and BGA devices in the same way.