MIL-PRF vs. AEC-Q200: What Engineers Need to Know

Kevin Palmer

With the growing electronic content in commercial space and avionics systems comes a continued push to lower costs and make components more affordable. This is especially true in higher volume, non-mission critical applications, as well as in equipment that can follow regular service and/or upgrade cycles.

To address increased demand and price pressures, component manufacturers have put into place high yield and high efficiency production processes; however, these are predominantly based on the needs of the large-volume commercial market. These quality standards may be sufficient for this market, but they don’t necessarily meet the requirements of commercial space or avionics customers.

At the same time, the aerospace, military and space (AMS) market has a growing need for products that provide consistently high performance in harsh environments over a longer service life. In the past, this market relied on very specific components that were manufactured to a defined military/aerospace standard, mission profile or MIL-PRF / DLA drawing.

More recently, however, some AMS companies have developed high-volume commercial innovations such as electric vertical take-off and landing (eVtol), unmanned aerial vehicles (UAVs), low-earth orbit satellites (LEOS) and new forms of electronic warfare equipment. The specific requirements of these designs have challenged engineers to evaluate and, eventually, consider alternative-grade products in order to meet their cost targets. Although these applications can be considered non-mission critical and very budget-conscious, the risk and consequences of failure means they demand significantly better performance and reliability than commercial-grade products.

Some years ago, the military market explored the use of commercial off the shelf (COTS) components to reduce costs for non-critical applications. At that time, the main issue was the lack of knowledge concerning the long-term performance of COTS products. Since those components were sold “as is,” they did not receive additional lot testing in order to identify infant mortality.

Engineers have recognized the need for a product category between COTS and MIL-PRF. In response, some manufacturers have released COTS+ products that allow engineers to select specific product testing based on the end application. COTS+ products have been successful and have a role to play in the market, but as yet they are not widely available.

Understanding the Meaning of “AEC-Q200 Qualified” and “Automotive Grade”
The rapid increase in the amount of electronic content in automobiles has resulted in significant development in components to serve this sector. Under-the-hood applications require components to perform at much higher temperatures, temperature cycles, humidity, vibration and sulfur levels due to their proximity to the engine and exhaust system gasses.

At the same time, the high cost of failure in terms of recalls and potential liability requires lower failure rates and longer lifespans. With these performance levels, higher volumes and longer production platform timescales, these automotive-grade components have attracted the attention of the AMS market as potential alternative solutions for non-mission critical applications.

However, before assuming that an automotive product will meet the specific requirements of the AMS market, it’s important to understand both automotive-grade specifications and quality standards behind them.

In the early 1990s, the Automotive Electronics Council (AEC) was established by Chrysler, Delco Electronics and Ford to create a common part qualification and quality standards system. At the start, AEC consisted of two committees, the Component Technical Committee and the Quality System Committee (the latter is no longer active and has deferred all quality specifications to IATF 16949).

For passive electronics devices, the AEC created the AEC-Q200 standard that defines the minimum, stress test-driven qualification requirements and reference test conditions. Once approved, AEC-Q200 production processes are tightly controlled in order to provide parts consistently manufactured to that agreed-upon standard; they are also subject to a two-year qualification maintenance timeline.

All AEC-Q200 Qualified Parts Are Not Created Equal
Testing procedures are well-defined within AEC-Q200, with sample sizes for test lots. However, instead of creating a specific standard for all producers, the specification notes that the measured parameters, values and workings of each acceptance criteria for each test should be agreed upon between the user and supplier.

This is an important point to note. For example, one supplier can define the acceptance criteria for an operational life test at 1 percent, while another can define the acceptance criteria at 5 percent. As a result, although manufacturers publish data sheets noting AEC-Q200 qualification, the actual parts are not necessarily direct and exact equivalents. Different production lines, manufacturing processes and test methodologies can result in variations from supplier to supplier. This is particularly true because manufacturers can define their own sets of test limits to match their optimized production processes.

Understanding IATF-16949 Certification
Created as the international standard for automotive quality management systems in production facilities, IATF-16949 is an important certification for automotive production. IATF-16949 emphasizes the development of a process-oriented quality management system that provides for continual improvement, defect prevention and reduction of variations and waste in the supply chain.

It’s important to note that IATF-16949 certification is not required to produce AEC-Q200 qualified products. As a result, depending on the manufacturer there may be important differences in the components produced in terms of comparative quality, reliability and performance.

Due to the harsh environmental requirements of automotive applications, the stress test levels for AEC-Q200 parts are very demanding – they even exceed military standards in some areas. However, some military requirements (such as established reliability) have load-life testing up to 10,000 hours per part and cumulative test hours exceeding 96,000,000 hours in a twelve-month period (S failure rate) – requirements that provide unrivalled performance/quality levels. The basis of AEC-Q200 relies on process controls in high-volume manufacturing and a statistical base at the sub-ppm level to achieve reliability goals.

By comparison, in addition to process controls, military products incorporate a series of part treatments, screenings under accelerated conditions and a post-production quality gate for 100 percent screening of production lots.

Another important consideration for parts used in high-reliability applications is termination material. In commercial applications tin-lead (SnPb) are strictly restricted. Similarly, most AEC-Q200 parts are produced with pure SnPb-free terminations. However, some manufacturers can specifically offer SnPb terminations for AEC-Q200 devices in order to provide an alternative solution for the AMS market. This is especially important in applications that might suffer from tin whiskers.

However, as this option is only available on a few product series (resulting in a much smaller production run), the cost for these components can be much higher than for standard lead (Pb)-free AEC-Q200 production parts.

Conclusion
Using AEC-Q200 parts in high-reliability applications can achieve the desired level of quality under the right circumstances, but not always at the volume or the level of specific testing required for military, aerospace or space applications.

Engineers must evaluate their application requirements and environmental characteristics, and should perform an in-depth evaluation of each supplier in terms of production processes and product performance based on tests completed, conditions of the test, test limits for the product, and quality systems and certifications in place. All this information needs to be considered when selecting the most appropriate solution.