Failure modes of diodes: If a diode is destroyed it measures as an open (infinite impedance). When a diode is damaged by overheating, what is the more likely failure mode observed in circuit testing?

Introduction / Context:
Understanding typical semiconductor failure modes accelerates troubleshooting. Overstress can push a diode into catastrophic failure that reveals itself either as a short circuit or an open circuit. Knowing which scenarios tend to produce which outcome helps interpret meter readings rapidly.

Given Data / Assumptions:

• Thermal damage due to excessive current or poor heat dissipation.
• Post-failure measurement with an ohmmeter or diode tester.
• We compare likely outcomes.

Concept / Approach:
Overheating can melt junctions or cause metallization migration, frequently shorting the junction and package leads. While opens do occur (bond-wire fuses), thermal overstress more commonly “welds” structures together, creating a low-impedance path observed as a short both directions on a meter.

Step-by-Step Solution:
Apply excessive current or inadequate heat sinking → die temperature rises above safe limits.Metallurgical degradation and silicon damage occur.Post-failure, continuity appears both directions → shorted junction.Circuit symptoms: blown fuses, excessive current draw, low rail voltage.

Verification / Alternative check:
Field experience and failure-analysis reports show many overstressed rectifiers fail short first; protection devices then open (fuse, breaker), removing power.

Why Other Options Are Wrong:
Conduct more / less: imprecise and not standard failure descriptors.Open: more typical of mechanical damage or bond-wire fusing, but the prompt contrasts this with thermal damage.

Common Pitfalls:
Assuming every dead diode is open. Always test both polarities; a shorted diode reads low both ways.

Final Answer:
short