In ST, we are committed to delivering products with robust and reliable performance in line with customer expectations, industry requirements and end user imperatives.
Product reliability is checked using accelerated stress tests able to reproduce in shorter time the field stress conditions that will occur in the lifetime of the product taking into account the assembly environment and the customer mission profile.
The mission profile describes the conditions of use of our products by a customer and notably conditions of stress that may occur during the product lifecycle. This includes operating temperature and frequency, number of write/erase cycles, mechanical and voltage stress and other similar parameters.
Stress test conditions accelerate the failure mechanisms that may occur within the mission profile. This allows us to estimate product reliability and improve our reliability performance. The reliability tests are based on internal and industry wide knowledge of failure mechanisms aiming to ensure that no failure will occur during the lifetime of a product. If new failure mechanisms are identified during these tests, they are analyzed to determine the root cause and corrective actions are taken to remove any potential reliability issues.
Design controls and approvals by product maturity stage
Reliability testing is integrated into the product qualification process. We perform an extensive Reliability Evaluation to assess product/process failure modes at each step of the product development cycle and determine their potential impact on product reliability.
At the start of the project, particular care is taken to identify all requirements related to the future use of the devices on top of the key characteristics. The industry domain(s), such as automotive, as well as specific customer requirements are identified and controls and tests are inserted to ensure compliance.
During product design, the reliability evaluation is split in two phases: prevention/projection and preliminary evaluation.
Design phase 1: Prevention/projection
We analyze the new product specification to forecast its reliability performance. In this phase, the evaluation is based on:
- Historical data and similarity criteria
- Customer mission profile when applicable
- Failure mode and risk information from existing data, including field return data
- Expected failure modes, defining constraints and warnings
- Process knowledge and similar product knowledge
- Reliability results, in product qualification and manufacturing monitoring, of similar devices
- Failure analysis data from internal trials as well as field returns and knowledge
- Process FMEA and Design FMEA
- Correlation between process variables and reliability results
- Device simulation results from design
- Customer specific requirements
The results allow us to define the reliability plan, set reliability design rules and predict failure rates for operating life test using Arrhenius’ law and other applicable models.
Design phase 2: Preliminary evaluation
The purpose of evaluation at this phase is to detect potential reliability issues and put into place solutions to overcome them, such as layout changes and technology improvements. Preliminary evaluation is based on:
- Selection and implementation on the first silicon samples of the test suitable to put in evidence the main potential failure mechanisms
- Statistical analysis of electrical parameter drifts as indicator of fast parametric degradation (such as retention tests)
- Failure analysis on failed parts to clarify failure modes and mechanisms and identify the root causes
- Physical destructive analysis on good parts after reliability tests when required
- ESD and Latch-up sensitivity measurement
When all of the criteria defined for the acceptance of the prototypes are met, a Design Approval Certificate is released and the product can then move to the next phase.
In ST, we run a global evaluation of the performance of the new product to guarantee reliability in our customers' manufacturing process and in the final application of use. This evaluation consists of:
- Full implementation of the reliability plan defined during the design phase
- Analysis by attributes (number of failed parts) and by variables (electrical parameter drift - test limits
- Physical destructive analysis on failed and good parts
- Test vehicle selection based upon similarity rules for production monitoring.
The results of the evaluation are used to issue a Product Qualification Certificate (PQC). Once the PQC is released, the product can move to production. The PQC can be released only if all results fall within the acceptance limits which are aligned to governing standards – for example, the Automotive Electronics Council Q100 and Q101 for the automotive products – and the industry domain for which the product is intended. Results are summarized in a Qualification Report, available to our customers on demand.
During production, reliability is monitored through real-time control, wear-out tests and burn-in as well as accelerated life tests. This allows us to keep the manufacturing process under strict control, guaranteeing constant performance, and to continuously improve design rules.
More information and contacts
For more information please contact your local sales representative or contact our technical support .