Here at DfR Solutions, we perform hundreds of design review projects a year. Sometimes companies come to us when they are considering a new electronic product and have only the initial designs. In other instances, companies approach us only after their product has already been configured, requesting a review of the final design before moving forward to the manufacturing stage. Ideally for the client, they are in the former group, partnering with us as early in design process as possible. It’s much more efficient (time- and cost-sensitive) to gather all available information and thoroughly check for potential failures of a design before nailing parts down, rather than to complete an assembly only to discover it doesn’t function properly in its use case scenarios.
When designing electronic products, there is an abundance of variables to consider. When we work with our clients, we find out as much information as possible about the product. What is its purpose? Who is going to be using it? What conditions will the product be subjected to? How is it expected to perform? What is the desired life expectancy of the product? A standard design review goal is to identify risks related to:
- Component selection
- Board (layout, finish, stackup)
- Electrical stresses
- Mechanical stresses
- Material issues (pottings, finishes, conformal coating, etc.)
- Life requirements
- Possible manufacturing challenges
- Field/use environment
The challenge in today’s competitive market is that companies are very protective of their ideas and tend to disclose as little information as possible. We understand sensitivity of intellectual property, however, we also caution that not providing enough information to those who are reviewing a design (or even those who are designing the product, as often companies outsource the electronics design to 3rd parties) prohibits them from identifying all possible risks. This leaves potential for a completed assembly failing at costly or even catastrophic rates.
To provide designers with a blueprint for navigating the dichotomy between protecting intellectual property and ensuring the reliability of a product via a reliability consultant, here is the design review process that we use when working with clients across various industries.
Establish reliability goal
Establishing your reliability goal is a simple enough notion. However, this step needs to be exhaustive in the sense that the desired life expectancy of a product must be identified clearly and with specificity to align with business goals such as projecting warranty expenses.
If you know the reliability goals of a design, you’ve taken a proactive leap toward identifying the possible failures that a product could encounter throughout its life cycle. The more effort that is put into establishing reliability goals, the easier the rest of the process of ensuring reliability becomes.
Quantify the use environment
This is one of the most important steps in ensuring reliability. Designers need to think through all the possible use scenarios for the product. You must consider not only the final use but also the surrounding conditions for that product to get to that point. For example, if you’re designing a tiny camera that will be attached to an astronaut’s suit while she’s exploring Mars, you might be thinking about the need for the camera to withstand freezing temperatures. But what you also need to address is the vibration that camera will be subjected to on the takeoff of the rocket. To give you an idea of just how thorough this step should be, even the shipping environment of the camera, getting it from point A to point B, should be taken into account when identifying the use environment.
Thermal analysis, and assessment and evaluation of the shock and drop levels relative to the use environment are core steps in evaluating electronic designs.
Component stress review
Before subjecting an assembly to tests and evaluation, it can be insightful to know how individual components perform under stress. Are all components of a board compatible? Are there any components you can eliminate from consideration from the start? Similar to establishing your reliability goal, a component stress review is a small step you can take to make your overall review process operate more smoothly and quickly.
Design for Manufacturing (DfM) and Design for Reliability (DfR)
When striving for optimal reliability, you need to consider the manufacturer’s abilities and limitations as well. You can simulate, test and design for the perfect product, but what if your manufacturer is not able to achieve the completed design? You have a product that is either incapable of being constructed or that falls short of reliability expectations.
For example, depending on the product, designers may need to consider the surface finish attributes that a manufacturer will apply. Sometimes surface plays a simple role in the aesthetics (whether it’s a silver or brass finish). Other times, the surface serves as a protective barrier and it is essential to the reliability performance of a product. A surface that is prone to rust could hinder overall performance if the product is meant to perform in moisture-conducive environments.
There are various surface options with different attributes. A table below provides helpful information when considering surface finish attributes and their performance based on the intended use.
Stress test to define design margins
Design margin is a measure of the difference between what the maximum capacity a part can operate at compared to what it will actually operate at. Measurements are taken of the operating temperatures and are then compared to the ratings of the individual components. If individual components are operating close to their upper limits, the analysis team works with a variety of parts of varying capacities, and tests to see which one is most likely to sustain enough clearance to prevent early termination. In performing stress tests, you take the components and test them at increasing temperatures until they fail. What this does is provides a cushion so that the design specifically addresses its use environment while acknowledging extreme circumstances.
Virtual qualification is the simulation portion of the design review process. Simulation is so valuable because it utilizes limited assets. Physical testing is costly and time-consuming, while simulation allows design teams to understand the functionality of a design without wasting physical components or overusing testing material/equipment. Simulation should not entirely replace physical testing, but it limits the dreaded cycle of “test-fail-fix-repeat. “
At DfR Solutions, we’ve developed our Sherlock Automated Design Analysis to be the leading failure analysis software. Sherlock users consistently find that their simulation becomes more efficient, ultimately improving time-to-market and overall robustness of their products while saving them money.
Perform the applicable product qualification tests
- Accelerated life test (ALT) to validate the life prediction model (VQ): This test essentially simulates your product’s life cycle. Without doing so, it is nearly impossible to be confident in a product’s life expectancy prediction.
- Temperature-Humidity-Bias (THB) tests to check for contaminants: This test addresses environmental effects to board that may not be picked up in other tests or simulations. For example, you can virtually design a board, but that board has not experienced the atmosphere of the design lab or manufacturing warehouse. Without a THB test where applicable, boards may have failure risks that simply were not identifiable any other way.
- Mechanical loading (Vibration, Mechanical Shock): Mechanical loading tests serve to identify many of the physical hurtles your board will need to withstand from simple use to accidental drops.
Perform failure analysis on test failures and field returns to initiate feedback loop
When performing failure analysis, you do not want to limit your analysis to assemblies that failed preliminary tests. In such a scenario, you are only discovering what doesn’t work before the product ever hits the field, when the ultimate goal is to determine the reliability of a product in its use environment. Failure analysis should include studying test failures as well as field returns should they exist, in order to more accurately understand field environments as well as exhaustively identify use cases you may not have considered in initial reliability qualifications.
If you would like to learn more about DfR Solutions' design process review services or failure analysis, contact us today.