HTRB vs H3TRB: What Each Test Proves
Both stress a device at high temperature with reverse bias. The humidity is the difference, and it is the difference between a dry failure mode and a wet one.
OCENME Engineering · Published November 7, 2026 · 4 min read
HTRB applies reverse bias at high temperature in dry conditions and stresses junction termination stability. H3TRB adds 85% relative humidity and stresses moisture-driven failure modes — ionic migration, corrosion and delamination. Equipment in humid or outdoor environments needs H3TRB data; HTRB alone does not predict those failures.
Key points
- HTRB: high temperature, reverse bias, dry. Proves blocking stability over time
- H3TRB: same, plus 85% RH. Proves resistance to moisture-driven leakage and corrosion
- Neither test predicts mechanical fatigue — that is what temperature cycling is for
- A report without duration, temperature, sample size and read points is not evidence
The two tests, side by side
| HTRB | H3TRB | |
|---|---|---|
| Temperature | 150 °C typical | 85 °C typical |
| Relative humidity | dry | 85% RH |
| Bias | reverse, at or near rated voltage | reverse, at or near rated voltage |
| Duration | 168 / 500 / 1000 hours | 168 / 500 / 1000 hours |
| Primary failure mode | termination instability, leakage walkout | ionic migration, corrosion, delamination |
| Relevant application | any | humid, outdoor, non-airconditioned |
The distinction is not academic. A device that passes 1000 hours of HTRB has proved it blocks voltage in dry heat. Put the same device in a telecom cabinet in a coastal climate and the failure mechanism is entirely different — moisture, not temperature, is the aggressor.
What HTRB actually catches
Passivation defects and mobile ionic contamination. During blocking, the high field at the junction termination interacts with charge in the passivation layer, and the breakdown voltage can drift down over hundreds of hours. A part with a marginal termination shows it here.
The read points matter. A report that says “passed 1000 hours HTRB” without listing the electrical measurements at 168, 500 and 1000 hours hides whether the parameter drifted and recovered, or stayed flat. Drift and recovery is a warning sign, not a pass.
What H3TRB actually catches
Moisture ingress through the mould compound to the die surface, where it does three things:
- Ionic migration between adjacent metallisation, creating a leakage path that grows with time.
- Corrosion of aluminium metallisation and bond pads, raising resistance and eventually opening a bond.
- Delamination at the compound-to-die interface, which creates a path for more moisture and a stress concentrator for later thermal cycling.
All three are latent and progressive, which is why a 168-hour pass is weak evidence for a ten-year life. The failure typically appears at 300–800 hours, not at 100.
Why package choice changes the result
Two devices with the same die can have very different H3TRB results, because the failure is at the package level:
- Mould compound chemistry determines moisture diffusion rate and adhesion.
- Lead frame plating affects corrosion at the wire bond interface.
- Package geometry sets the distance moisture must travel to reach the die.
- Die attach voids create paths and stress points.
This is why a family-level qualification report that covers a different package is not evidence for your ordering code. When you ask for a report, name the package.
How to read a report you are given
A usable report contains six things. If any is missing, ask for it:
- Exact ordering code and package.
- Die revision or lot reference.
- Stress conditions: temperature, humidity, bias voltage.
- Sample size per read point.
- Electrical parameters measured at each read point, with pass/fail limits.
- Failure analysis for any units removed, not just a count.
The sixth is the one most often omitted, and the one that matters. A unit that fails at 500 hours with delamination visible on C-SAM tells you something; a line that says “2 failures” tells you nothing.
What none of this proves
Neither HTRB nor H3TRB tests mechanical fatigue. Die attach cracking and wire-bond lift-off from thermal expansion are the domain of temperature cycling and thermal shock. A complete reliability picture for a power supply application usually needs all three: bias stress (HTRB), humidity bias (H3TRB) and thermal cycling (TCT).
Nor do they prove anything about dynamic behaviour. Switching loss, avalanche ruggedness and body diode recovery are separate characterisations, and a device can be flawless in all three reliability tests and still be the wrong part for a high-frequency design.
A practical evidence checklist
For equipment sold into a humid or outdoor environment, ask for this and nothing less:
| Evidence | Why |
|---|---|
| H3TRB 500+ hours, exact ordering code | Predicts the dominant field failure mode |
| TCT 500+ cycles, stated temperature extremes | Predicts joint and bond fatigue |
| Lot test record with measured values | Shows the part shipped matched the qualification sample |
| PCN procedure in writing | Prevents a silent die or compound change |
| C-SAM images from failure analysis, if any failures occurred | Proves the analysis was done, not just counted |
We run HTRB, H3TRB, HT/HU, high-temperature storage, temperature cycling, thermal shock, solderability, RSH and HPC in-house — the reliability testing page describes each test and states plainly what it does not cover. Reports are issued per part number and lot on request through the contact form.
This article describes general manufacturing practice for machined and fabricated components. It is not a substitute for a drawing-specific engineering review — tolerances, material selection and process capability depend on the individual part.