Articles

Black’s Equation

Black’s equation for estimating the time to failure due to electromigration is a classic. James Black explored and wrote about electromigration in aluminum metallization within semiconductors since 1969.

He and others have explored other materials used as conductors prone to electromigration. Thus, there are a number of models and constants available to match your particular system.

Let’s take a look at the general equation for a microcircuit conductor after a brief description of the failure mechanisms called electromigration. [Read more…]

Metal is a wonderful, strong, material. Yet under certain types of stresses metal can fail One in particular is fatigue due to cyclic motion.

Metals in a solid state have an atomic level lattice structure. This provides the strength and flexibility. It is the flexibility part that causes trouble. We don’t get the benefit of flexibility for free. As the metal bends it ‘adjusts’ the lattice to accommodate the motion. In doing so, it changes the metal properties becoming a bit more brittle, for example.

In most cases a very small motion causes imperceptible changes and loss of functionality. In some cases, like bending a wire coat hanger with the intent to break it, just a few cycles of dramatic bending is enough to break the wire.

In metal applications that experience cyclic motion and the risk of metal fatigue failure may occur during the expected duration of product use, we may need to characterize the time to failure behavior. An accelerated life test for a metal fatigue failure mechanism is not difficult, yet does take some planning to get meaningful results. [Read more…]

Peck’s Relationship

High temperature & humidity is a common test condition. For specific failure mechanisms, there are models available (or you can create a model) to determine the translation from test to use conditions.

These acceleration models generally only apply to one specific failure mechanisms and do not apply to a system level estimate of life. If the failure mechanism is the dominant failure mechanism for the product, then an ALT exploring just that mechanisms would provide a life estimate.

Peck’s relationship is an acceleration model for the effect of humidity on the metallization elements of integrated circuits within plastic enclosures (typically an epoxy over molding).  [Read more…]