Highly Accelerated Life Testing (HALT)
Highly Accelerated Life Testing (HALT) is a stress testing methodology used during the engineering development phase of a product to quickly reveal design weaknesses.
Progressively higher levels of thermal and mechanical stress are applied to the product in a cyclic procedure, beyond normal operating levels the product would be expected to experience. In an accelerated timeframe, failures are encouraged that highlight weaknesses in the design.
The product must be stimulated and monitored to identify limits and any failure points; these can be both soft and hard failures. A soft failure occurs when a product under test ceases to operate correctly, but resumes correct operation when the stressing environment is eased - for example failing at extreme temperatures but resuming normal operation once the product is returned to within its normal operating temperature range. A hard failure occurs when normal operation cannot be achieved even under normal operating conditions.
In the event of hard failure, TT Electronics has its own investigative and micro-sectioning capability to quickly identify the nature of the failure and advise the customer on remedial action.
HALT is not a compliance test nor is it attempting to simulate the product’s environment. It is complementary to existing reliability and environmental testing, yet it does not replace them. It should be viewed as an additional tool in the engineer’s quality and reliability toolbox.
The results of HALT testing allow visibility of:
- Thermal design weakness
- Mechanical design weakness
- Operational component limitations
- Gap between product’s required operating limits and actual maximum limits
Giving the following benefits to your design:
- More robust and rugged design with greater reliability
- Reduced time to market: any design weaknesses are identified earlier in product lifecycle, reducing development time and cost
- More reliable product results in reduced warranty costs and improves customer confidence
TT Electronics offers several levels of support for HALT, from use of our equipment with operator support to full consultancy advising a HALT strategy at design followed by a Highly Accelerated Stress Screening (HASS) strategy if required at production.
Highly Accelerated Stress Screening (HASS)
The goal of Highly Accelerated Stress Testing (HALT) is to identify design weaknesses and to take remedial action early in the product lifecycle. As your more robust, rugged product moves into production, you now face a new set of challenges to ensure that the production process does not compromise reliability.
Taking the information from the HALT, thermal and vibration limits are set between the extreme failure points of HALT and the normal operating limits. The goal is now to quickly apply limited stress to the product so that you avoid customers experiencing Dead on Arrival (DOA) or early failure.
These limits are not fixed and should be reviewed during the life of the production to ensure that products are not being under or over stressed. Under stressed would result in a customer experiencing a DOA or early failure and over stressed would result in a shortened product life.
HASS can be applied to all manufactured products, and is typically used for high reliability applications, new product introduction or when a production process is changed. For other applications or where the production process is mature, this can be reduced to a batch sampling to reduce costs.
Environmental Stress Screening (ESS)
For some applications, for instance where the operational limits are already extreme, a different approach is taken. Here Environmental Stress Screening (ESS) is applied, in which the key difference is that the stresses applied are within the normal operating parameters of the product being tested.
The goal of both HASS and ESS is to ship a more reliable product to the customer. However, each method achieves the goal differently, depending on application specific timescales and costs.