Automated X-ray inspection

For the on-chip bus, see Advanced Microcontroller Bus Architecture § Advanced eXtensible Interface (AXI).

File:X-Ray Circuit Board Zoom.jpg

X-ray zoom series on an old token ring network adapter card

Automated X-ray inspection (AXI) is a technology based on the same principles as automated optical inspection (AOI). It uses X-rays as its source, instead of visible light, to automatically inspect features, which are typically hidden from view.

The increasing usage of ICs (integrated circuits) with packages such as BGAs (ball grid array) where the connections are underneath the chip and not visible, means that ordinary optical inspection is impossible. Because the connections are underneath the chip package there is a greater need to ensure that the manufacturing process is able to accommodate these chips correctly. Additionally the chips that use BGA packages tend to be the larger ones with many connections. Therefore, it is essential that all the connections are made correctly.

AXI is often paired with the testing provided by boundary scan test, in-circuit test, and functional test.

Process

As BGA connections are not visible the only alternative is to use a low level X-ray inspection. AXI is able to find faults such as opens, shorts, insufficient solder, excessive solder, missing electrical parts, and mis-aligned components. Defects are detected and repaired within short debug time.

These inspection systems are more costly than ordinary optical systems, but they are able to check all the connections, even those underneath the chip package.

Related technologies

The following are related technologies and are also used in electronic production to test for the correct operation of electronics printed circuit boards.

• In-circuit test (ICT)
• Joint Test Action Group (JTAG)
• Automated optical inspection (AOI)
• Functional testing (see acceptance testing)