HALT and HASS - Electronics reliability testing

Introduction

The reliability of electronic devices depends on numerous interrelated factors. The main ones include:

• Proper product design. I recommend applying the principles of DFX, particularly the concepts of DFM, DFA, and DFR. A key method in the design phase should also be Failure Mode and Effects Analysis - DFMEA.
• Quality of electronic components. Proper component selection and sourcing from reputable, established suppliers are essential.
• Quality of materials. Reliability is significantly influenced by factors such as the type of solder alloy (lead-based or lead-free), flux, SMT solder paste, etc. Electronics are often additionally protected through coating, potting, or sealing with resins or silicones.
• Process control. For electronics soldering, it is crucial to apply the correct SMT reflow profile and wave soldering profile. The implementation of quality methods like PFMEA, control plans, SPC, MSA, etc., is also important.

Implementing the above strategies, especially for critical applications such as IPC class three products, can be a significant challenge.

Achieving high reliability can sometimes be difficult, especially when dealing with underestimated design margin or hidden component defects that standard functional tests cannot detect.

In this context, it is worthwhile to familiarize ourselves with two interesting test methods that, if properly implemented, can significantly improve the quality of products both at the design phase and during subsequent series production. These solutions are:

• HALT - Highly Accelerated Life Testing
• HASS - Highly Accelerated Stress Screening

HALT and HASS are considered "extreme testing" techniques. They differ in application scope and in the phase of the product life cycle they target, but they share a common goal: ensuring the highest possible quality in electronics.

This article introduces the concepts of HALT and HASS and discusses relevant standards.

Enjoy the read.

What is HALT?

HALT (Highly Accelerated Life Testing) is an accelerated testing methodology designed to quickly identify the durability limits of a device under design. Unlike traditional reliability testing that simulates typical usage conditions over a longer period, HALT subjects prototypes to extreme environmental and operational stressors over a short period—until failure occurs. In the context of DFMEA, this is referred to as a “test to failure.”

HALT testing includes:

• Extreme temperatures: from very low (e.g., -40°C) to very high (e.g., +100°C or more), then with rapid thermal cycling.
• Vibrations: high-amplitude random vibrations in 6 degrees of freedom.
• Electrical loading: power cycling, overvoltage, voltage spikes, etc.
• Combined testing: a combination of the above to apply cumulative environmental stress.

A typical HALT profile (excluding electrical testing) includes:[3]

1. Cooling stress - progressive temperature decrease.
2. Heating stress - progressive temperature increase.
3. Rapid thermal transition - series of rapid thermal cycles.
4. Vibration stress - vibration tests with increasing amplitude, without temperature change.
5. Combined environment - simultaneous application of vibrations and rapid thermal changes.

The various steps of the HALT test are shown in the animation below:

The core premise of HALT is to cause the product to fail - not to simulate actual usage, but to identify design weaknesses. For example, if a solder joint fails, engineers might switch to a more stress-resistant lead type.

HALT is iterative: after each failure, when a design modifications are introduced - then the tests should be repeated to verify if the required reliability level is achieved.

What is HASS?

HASS (Highly Accelerated Stress Screening) is a method used during serial production. It is based on data gathered during HALT, but its objective is not design refinement—instead, it is to detect production defects in finished products.

HASS uses intense yet controlled stress tests covering the same parameters as HALT (temperature, vibration, electrical load), but within the limits established during HALT. This ensures the test doesn't damage the product but reveals units with latent defects, such as:

• Assembly errors.
• Material defects (e.g., component or solder joint failures).

Typically, a sample from each production batch is tested. If failures occur, root cause analysis and corrective actions shall follow. If the sample passes HASS, the batch may be shipped.

Standards

Although HALT and HASS are not governed by a single, comprehensive international standard, their application is supported by several industry standards, like:

• IEC 62506 - general principles of accelerated reliability testing, including HALT.
• IPC-9592 - design and test guidelines for power supplies, covering HALT and HASS.
• JEDEC JESD22 - standards for testing electronic components (e.g., Section A110 - Highly Accelerated Temperature and Humidity Stress Test).

In practice, many companies develop their own HALT and HASS procedures tailored to their products and operating environments.

Summary

HALT and HASS are two essential elements of the DFR strategy—the former focused on the design phase, the latter on the production phase. HALT enables engineers to identify and eliminate design weaknesses before the product hits the market. HASS serves as a "quality filter", removing potentially defective units from the production line.

Implementing these methods requires specialized equipment (e.g., environmental chambers, vibration tables) and expertise, but the benefits are substantial: fewer returns, lower repair costs, and higher customer satisfaction.[1][2][3]. This approach is especially crucial for critical applications where reliability is paramount.

In my view, with increasing miniaturization and complexity of electronic devices, HALT and HASS may become indispensable test methods in the design and production of reliable electronics.