The definition is clear.

A test that operates devices for long periods at high temperature, high voltage, and high load to bring out early failures in advance.

It has two purposes.

① Removing early failures

② Bringing out latent defects

In other words, breaking them before they reach the market.

The failure rate of semiconductors is not constant over time.

A well-known concept is the bathtub curve.

Transitions in failure rate:

① Early failure period (infant mortality)

② Random failure period

③ Wear-out failure period

The aim of burn-in is:

to remove ① early failures before shipment.

Typical examples:

Microscopic defects

・Wiring cracks

・Gate defects

Foreign matter contamination

・Particles

・Residues

Poor contact

・Bumps

・Wire bonds

Insulation defects

・Film defects

・Pinholes

They do not surface in normal operation, but appear under high stress.

Typical conditions:

● Temperature: 125°C to 150°C

● Voltage: 1.2 to 1.5 times the rating

● Operating mode: actual operation / high-load operation

● Time: tens to hundreds of hours

High temperature, high voltage, long duration. It is an accelerated degradation test.

Components:

● Burn-in boards → test many chips simultaneously

● Sockets → electrical connections

● Heaters → uniform temperature control

● Power and signal supply systems → apply operating loads

In recent years, boards supporting high I/O counts and dedicated equipment for AI chips have also appeared.

If burn-in addresses “early failures,” lifetime testing evaluates “wear-out failures.”

Purpose: to estimate how many hours of operation it takes for a device to fail.

Typical tests:

● HTOL (High Temperature Operating Life) → high-temperature operating lifetime

● TDDB lifetime test → dielectric breakdown lifetime

● EM lifetime test → wiring failure lifetime

● NBTI / PBTI tests → transistor degradation

It is impossible to test 10 years of actual use as is.

So high temperature, high voltage, and high current are applied to accelerate degradation.

A typical model: the Arrhenius model

A 10°C rise in temperature → roughly twice the degradation rate.

In other words, long-term lifetime is predicted in a short time.

Burn-in improves back-end yield.

Effects:

・Fewer field failures

・Removal of early failures

・Greater quality and trust

However, there are trade-offs with:

● Higher test costs

● Lower throughput

● Damage from excessive stress

The difficulty has been rising in recent years.

Reasons:

① Increased power consumption → heat control becomes difficult

② More I/Os → board design becomes complex

③ 3D stacking → uneven heat distribution

④ AI chips → simulating actual operation is difficult

In other words, the test itself has become a design challenge.

The requirements are in a different class.

● Operating temperature range → -40°C to 150°C or more

● Service period → 15 years or more

● Failure tolerance → extremely low (impact on human life)

Therefore:

Longer burn-in times, higher test voltages, and combined tests are carried out.

Directions of evolution:

● Wafer-level burn-in → testing before packaging

● System-level burn-in → testing in the mounted state

● AI load simulation testing → for GPUs / ASICs

● Low-stress, high-precision testing → avoiding excessive degradation

・Burn-in is a technology for removing early failures

・Lifetime testing is a technology for predicting wear-out failures

・The bathtub curve is the basic concept

・Degradation is accelerated with high temperature and high voltage

・Its importance is expanding rapidly in automotive and AI

1.What is the main purpose of burn-in testing?

2.Explain the three regions of the bathtub curve.

3.Why is accelerated testing necessary?

4.Why is burn-in difficult for advanced AI chips?

 

Column Supervisor: Koji Kakumoto (President, OTIS Co., Ltd.)

After studying abroad and working in planning and development at a trading company, he joined OTIS Co., Ltd. in 2011. While primarily working in the Corporate Planning Department, he has also served concurrently in manufacturing and technical divisions, and since 2018 has served as President, working to drive business growth and strengthen the organization.

 

This article is a general technical explanation intended for educational purposes and does not refer to any specific company, product, or technology.