Can a TVS Diode Be Reused After a Surge If It Has Not Shorted?

A TVS diode that remains open on a continuity tester after a surge is not automatically fit for reuse. Transient stress can increase reverse leakage, shift breakdown voltage behavior, weaken clamping, damage a bond connection, or create a local thermal defect that appears during the next event. Engineering samples can be analyzed under a controlled plan; production returns need a documented disposition rather than a buzzer check.

Continuity detects one failure mode and misses several others

A handheld meter applies a small voltage and current. It can reveal an obvious short or open connection, but it cannot establish reverse leakage near the operating voltage, breakdown voltage at the specified test current, clamping behavior during a pulse, or remaining pulse capability. A clean plastic surface also provides little evidence about damage inside the die or bond structure.

After a surge, classify the suspected protector before deciding what to measure:

• hard short, where the line is pulled down or an upstream fuse opens;

• open circuit or damaged connection, leaving the downstream circuit unprotected;

• parametric shift, where leakage, breakdown, or pulse voltage has changed;

• no measured shift under the available static tests, with remaining life still unknown.

The last category should not be relabeled “good as new.” It states the limit of the evidence.

Reconstruct the event before removing the component

The source determines whether the TVS was used within its intended boundary. Record the open-circuit voltage, source impedance or available short-circuit current, waveform, polarity, event count, repetition interval, cable and coupling path, ambient condition, and circuit operating state. If the source was a field failure, preserve the power supply, cable, load, and installation details when possible.

Keep the board intact long enough to capture system evidence. Photograph the entry point, TVS placement, return path, series elements, discoloration, and nearby components. Measure input resistance, standby current, power-rail behavior, and product function. Removing the diode too early can erase a cracked solder joint or board leakage that was mistaken for silicon damage.

A statement such as “the unit saw a 1 kV surge” is incomplete. Two 1 kV sources with different impedance and pulse duration can deliver very different current and energy. Reuse decisions need the event conditions, not the voltage label alone.

Reverse leakage is the first useful parametric comparison

Measure leakage under a defined reverse voltage, temperature, stabilization time, and instrument range. Board-level current includes parallel resistors, capacitors, contamination, and other protectors, so compare the complete board first and remove the device only when separation is necessary.

A retained, unstressed part from the same ordering code and lot is the best reference. If that is unavailable, use controlled datasheet limits while acknowledging lot and measurement differences. Room-temperature leakage at a low voltage can look normal even when the device changes near its maximum continuous operating voltage or at elevated temperature.

For battery and standby products, a leakage increase can be a functional failure long before the diode becomes a hard short. Measure the circuit behavior that matters to the customer, then connect it to component data.

Breakdown comparison requires the conditions, not a single meter reading

Breakdown voltage, or VBR, is defined at a stated test current. Use a current-limited source or curve tracer suitable for the part and preserve polarity. Compare stressed and control devices using the same fixture, current steps, dwell, and temperature.

An efficient laboratory sequence is:

1. Photograph and label the board, device location, and event entry.

2. Capture board resistance, standby current, power rails, and product function.

3. Measure reverse leakage below the suspected working limit using safe conditions.

4. Trace the breakdown region with controlled current.

5. Observe powered thermal behavior and inspect solder joints and copper paths.

6. Remove the device only when component-level separation is required.

7. Apply a controlled pulse only when the analysis plan and safety limits justify it.

This order separates board evidence from damage introduced during removal. It also makes the comparison reproducible when several returned units are involved.

Thermal behavior can reveal a defect that a static check misses

Operate the product at a current-limited input and observe the suspected TVS and surrounding copper with an appropriate thermal method. Compare the stressed board with an unstressed control under the same load and ambient conditions. A local temperature rise can point to increased leakage, a damaged solder joint, carbonized contamination, or another component on the protected rail.

Temperature is evidence, not a diagnosis by itself. Emissivity, airflow, copper spreading, and camera angle affect the image. Confirm any hot spot with electrical measurements before assigning the failure to the TVS.

A second destructive surge does not prove remaining life

One tempting check is to strike the used TVS again and see whether it survives. That test may be useful for failure analysis, but it consumes the sample and does not establish how much capability remains. Passing one additional event cannot prove that the part still meets its original production requirement.

If pulse comparison is necessary, use matched stressed and control samples, the same calibrated generator, the same fixture, and the same voltage and current measurement points. Capture residual voltage, current, waveform, post-pulse leakage, and functional behavior. State clearly that the result describes the tested samples rather than the remaining life of every unit in the lot.

The surrounding circuit may have absorbed part of the event

The TVS is only one part of the surge path. Trace resistance, a fuse, series resistor, common-mode element, connector contact, ground conductor, and downstream IC clamp can all carry current. A TVS can test within its static limits while another part has degraded, or the TVS can be overstressed because the return path forced excessive inductive voltage.

Review these physical details before replacing the diode with a larger package:

• distance from the entry connector to the TVS;

• width and via count in the return path;

• loop area between the incoming conductor and return;

• coordination with fuses, resistors, filters, and upstream protection;

• maximum normal voltage, tolerance, and power-rail overshoot;

• downstream absolute maximum and acceptable residual voltage.

A higher peak pulse power label does not correct a long return path or an incorrect stand-off voltage.

Define a disposition rule before the next return arrives

For production equipment, the conservative rule is to replace a TVS that is known to have absorbed an event beyond the validated product boundary. Replacement cost is usually easier to control than uncertain remaining pulse life. The investigation can still retain selected samples for electrical and physical analysis.

For engineering prototypes, a written disposition can classify the part as failed, suitable only for analysis, or unchanged under the tests performed. The third label must include the test limits. It must not be shortened to “reusable” unless the product owner has an approved validation basis for that conclusion.

ASIM can help review the electrical window, pulse conditions, and layout around a TVS application. The ASIM TVS diode manufacturer hub is a stable entry point for selection information. The final decision should still cite the exact ordering code, its controlled datasheet conditions, and the target board's validation record.

Practical answer

Do not reuse a surge-exposed TVS in production merely because it has not shorted. First compare leakage, breakdown behavior, thermal response, and system function with an unstressed control. Use pulse testing only under a defined analysis plan. If the event exceeded the validated boundary or remaining life cannot be established, replace the device and correct the surge path that caused the stress.