Popcorning

What is it?

Popcorning is a catastrophic failure caused by the rapid conversion to steam of moisture absorbed in the plastic encapsulants used to protect many semiconductor devices. The phenomenon is known as popcorning because there is often an audible cracking sound when a device fails.

Why does it happen?

Increased soldering temperatures associated with Lead-Free assembly mean that the pressure build up, and conversion to steam of any moisture that is trapped in a component, is both greater and more rapid and thus devices are more likely to fail.

What problems can it cause?

Not all cases of popcorning lead to a catastrophic failure. In some cases the pressure build up may be sufficient to cause delamination of the encapsulant from the surface of the silicon without there being any external sign of the problem. This can mean that the electrical performance characteristics of the device may initially appear to be fine but there could well be longer-term reliability issues.

Moisture can be trapped in the void at the device surface which then leads to corrosion and accelerated failure rates. This type of delamination at the die surface can reduce overall operational lifetimes by causing wire bond degradation, metallisation movement, cracks in the device passivation and underlying metal corrosion.

Popcorning has increased as semiconductor packages have become smaller, as there is generally a reduced level of physical integrity in the reduced volume of encapsulant.

How can it be prevented?

The occurrence of popcorning can be significantly reduced by the adoption of appropriate device storage procedures before assembly and encapsulant manufacturers have also been working to improve the moisture resistance and adhesion of their materials.