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X-ray picture of good solder joints. Good solder joints between BGA and PCB. Ball grid arrays (BGA) and chip scale packages (CSA) present special difficulties for testing and rework, as they have many small, closely spaced pads on their underside which are connected to matching pads on the PCB. Connecting pins are not accessible from the top ...
A grid array of solder balls on a printed circuit board after removal of an integrated circuit chip. Cross-cut section of BGA mounted circuit. A ball grid array (BGA) is a type of surface-mount packaging (a chip carrier) used for integrated circuits. BGA packages are used to permanently mount devices such as microprocessors.
For example, in the case of a ball grid array (BGA) package, the pre-deposited solder ball on the package and the solder paste applied to the circuit board may both melt, but the melted solder does not join. A cross-section through the failed joint shows a distinct boundary between the solder ball on the part and the solder paste on the circuit ...
Dye-n-Pry is a useful failure analysis technique to detect cracking or open circuits in BGA solder joints. [2] This has some practical advantages over other destructive techniques, such as cross sectioning, as it can inspect a full ball grid array which may consist of hundreds of solder joints. Cross sectioning, on the other hand, may only be ...
The chip is then wire bonded and protected from mechanical damage and contamination by an epoxy "glob-top". Chip-on-flex (COF), a variation of COB, where a chip is mounted directly to a flex circuit. Tape-automated bonding process is also a chip-on-flex process as well.
It is a useful test for all pad geometries and is sensitive to board design and materials. The ball pull test is specifically design for BGA components and has a large sensitivity to the solder alloy and joint formation. The ball shear test is also specified for BGA components and involves shearing the solder balls of the BGA.
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.
The solder balls can be placed manually or by automated equipment, and are held in place with a tacky flux. [2] A coined solder ball is a solder ball subject to coining, i.e., flattening to a shape resembling that of a coin, to increase contact reliability. [3] Ball grid array, chip-scale package, and flip chip packages generally use solder balls.