Die Chipping; Die Chip-outs

Die Chipping

Die chipping is a failure mechanism wherein a part or parts of the die break away from the die itself. The damage on the die is referred to as a 'die chip-out' (see Figure 1).

Die chip-outs are often caused by purely mechanical means, although some cracks can be propagated by thermo-mechanical stresses until a fragment chips off the die, resulting in a chip-out. The die corners are most vulnerable to chipping, since they are more physically exposed than the edges of the die.

Die chip-outs that extend into the active circuit of the die will obviously make a device fail. Die chip-outs that are just confined to a small area in the periphery of the die, on the other hand, will probably not immediately result in electrical failures, but these can lead to a reliability failure later on.

Such chip-outs, being surrounded by microcracks, can serve as initiation points for full-blown die crack propagation when the device is subjected to thermo-mechanical stresses. These chip-outs may also have some glassivation damage that allows moisture and contaminant ingress, leading to die corrosion. Thus, die chip-outs that do not result in immediate electrical failures must not be ignored.

Figure 1. A Die Chip-out

Die chip-outs are often due to mishandling. For instance, picking up a die carelessly with a tweezer for eutectic die attach can result in the tweezer slipping out of position, chipping the die edge in the process. Manual capping of ceramic packages prior to sealing may also cause a die chip-out, if the cap or lid hits a corner of the die during capping.

Improper equipment set-up can also cause die chipping. Probe needles, die attach dispense tools, wirebond tools, and the like can inadvertently land on the die with force and chip off a part of it. Improper set-up can likewise cause wafer saw blades to induce die edge chipping.

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