A call for performance-centric materials specifications.
The combination of rising performance expectations and intense commercial pressures means choosing the right substrate materials for new-product designs is more important than ever. A wider selection of materials, with more finely nuanced properties, increasingly complicates making the “right” choice. Help is available from suppliers and industry bodies. But designers can also help themselves by being more willing to share information with their suppliers.
As PCB industry veterans, we know well the board is typically the last part of the project specified when a new product is designed. On the other hand, it’s the first item needed when serious development begins. Designing the circuitry to go on the PCB obviously gets most of the attention, but the substrate itself is usually the lowest priority in engineers’ minds. When the time finally comes to consider it, teams will often simply default to the same materials used previously. As performance demands imposed on successive product generations continue to intensify, and factors such as conductive anodic filament (CAF) formation that seriously affect reliability become more critical, this approach is increasingly unsatisfactory.
As the industry has come to understand more about how the substrate properties influence performance and reliability under various operating conditions, so the number and diversity of material types available has increased. In the past there were only a handful of options open to designers. Today, international specifications offer over 100 different material categories to choose from. Designers, understandably, struggle to connect the specifications with the properties sought. It doesn’t help that these specifications are usually based on chemical composition. As the breadth of choice on offer continues to increase, it’s almost impossible for electronics engineers to relate to them. I have been calling for some time for the industry to move to performance-centric specifications that are easier for engineering communities to interpret.
Getting help is essential, because struggling alone risks underspecifying or overspecifying the material for the application at hand. Neither is good: underspecifying risks the product coming up short in a way that could be beyond any realistic remedy. Overspecifying, to be “on the safe side,” can be commercially disastrous in ultra-competitive markets such as consumer technology. The chosen materials also need to be readily available in any location globally where the product is to be manufactured. Some resins, for example, are only available in certain domestic markets and are difficult to procure elsewhere.
So, what to do? Qualifying or testing materials helps to understand their performance and properties but is expensive and time-consuming for companies to undertake independently. Pooled testing, where groups of companies get together to do specific tests and share the results, is one response. Also, the HDP User Group (hdpug.org) has several active programs including the Lead-Free PWB Materials Reliability project, which is currently in phase 6. I have run various phases of this project. It benefits from pan-industry participation and has established a comprehensive set of analyses that cover Dk and Df, CAF, thermal stress, and other tests on standardized test coupons. Ventec has contributed several materials to this program, including one of the materials in the latest phase 6 tests.
Designers can also take advantage of another emerging trend among suppliers, which is to present carefully curated sets of materials for specific application areas. Our material guides, for example, bring together products with properties suitable for automotive or aerospace and further subdivide them according to target applications and operating environments, such as under-the-hood or in-cabin. In this way, suppliers effectively contribute their expertise to help customers short-list products that can meet their requirements. This helps by simplifying and accelerating selection, narrowing the focus to materials that are fundamentally suitable.
Helpful though this is, as suppliers we often need designers to express their requirements directly if we are to provide the right material for the right task. During my time in the industry, I have been involved in a few cases where large OEMs have been too sparing with information, particularly about the intended application and operating environment, and ultimately were obliged to recall large numbers of units from the field. With just a little more willingness to share information, the problem could have been avoided, rather than remedied at high financial and reputational cost.
While it’s understandable for any OEM to be wary of sharing information about its IP and product strategies, cases like these highlight the value of trust between OEMs and their suppliers. I have called before for greater openness and trust. As materials selection becomes more complex and, at the same time, more important to get right the first time, there is more to gain by finding ways to be open and more to lose by keeping traditional barriers in place.