We often talk about the importance of Design for Reliability (DfR) and the impact it has on overall project efficiencies and success. Let’s take a look at DfR fundamentals, and how companies employ it to its best advantage.
What is DfR?
Essentially, DfR is a process for ensuring a product or system performs the specified function, within the customer’s use environment, over the expected lifetime. DfR occurs at the design stage before physical prototype, and is often part of an overall Design for Excellence (DfX) strategy.
Why is DfR critical?
The complexities of today’s technologies make DfR more significant – and valuable – than ever before, for several reasons:
- Product differentiation: As electronic technology reaches maturity on many levels, there are fewer opportunities to set products apart from the competition through traditional metrics, like price and performance
- Reliability assurance: Advanced circuitry, sophisticated power requirements, new component and material technologies, and less robust parts make ensuring reliability increasingly difficult
- Cost control: 70% of a project’s budget is allocated to design
- Preserving profits: Products get to market earlier, preventing erosion of sales and market share
When is DfR used?
Most companies apply DfR at the design and development stage of a given project. However, this common practice comes two steps late in the process. DfR is most effective in the Concept Feasibility Stage:
Who should be involved with DfR?
With the goal of simultaneous design optimization, the typical engineering-silo process flow is counterproductive. Instead, concurrent engineering hinges on contributions from all essential project team members, including:
- Component engineers manage the component library (AVL, packaging data)
- Systems engineers set up system constraints for assembly
- Layout engineers are assigned CAD responsibilities
- Manufacturing engineers are responsible for DFM assembly/box connections
- Thermal engineers develop boards based on power requirements
- Test engineers establish ESS/ICT testing parameters
- Reliability engineers are occasionally engaged, but they may focus too heavily on statistical techniques and environmental testing than is necessary for the design phase
How is DfR implemented?
Here are some DfR best practices that apply to nearly all projects, and guide the process:
- Set reliability goals based on survivability. This is often bound by confidence levels, such as 95% reliability with a 90% confidence level over 15 years
- Avoid MTTF and MTBF because they do not measure reliability. MTTF/MTBF validates data, or the measurements may be customer-mandated. However, this “industry best practice” isn’t always the best.
- Employ Physics of Failure (PoF). Applying PoF requires a deep understanding of how the desired lifetime and use environment affects the design. It also takes substantial effort, but there is valuable return in:
- Determining average and realistic worst-case scenarios
- Identifying all failure-inducing loads, such as:
- Power cycling
- Electrical loads and noise
- Mechanical bending
- Random and harmonic vibration
- Including all environments:
- Keep dimensions loose at this stage. A large number of hardware mistakes are driven by arbitrary size constraints
Sherlock Automated Design Analysis™ software augments DfR. It uses PoF to simulate testing variables, helping engineers identify and correct failure risks during the design stage to optimize reliability and realize substantial time and cost savings.
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