Electronic Design

QML Sets New Standards

Texas Instruments' Military Semiconductor Division is the largest supplier of Qualified Manufacturers List (QML) products to the U.S. military. With over 3500 types of devices, TI is an authority on QML.

According to Richard Biddle, quality and reliability engineer at TI, the current QML process evolved from Defense Secretary William Perry's 1994 mandate to the Department of Defense to replace the use of mil-spec in purchasing components for end systems with specific performance standards. At the same time, the DoD sought to implement "Best Commercial Practices."

One potential limitation of the DoD action was its broad-brush approach covering everything purchased by the DoD and its contractors—from boots to integrated circuits. For commodity items like clothing, it isn't difficult to see the logic in a less rigid, less costly commercial equivalent. However, highly complex ICs are a different matter.

As a result, during the mid-1980s some key industry members began work to develop a new methodology. The goal was to preserve the high-quality, high-reliability ICs that the armed services had come to expect while also incorporating the most advanced commercial qualification and procurement methods.

What came about was a comprehensive process methodology called the Qualified Manufacturers List (QML). In 1995, the government established the QML as a standard titled MIL-PRF-38535. This moved it beyond mil-spec status to meet the definition of a "performance- based specification" as called for in Secretary Perry's mandate.

During the Cold War, military components were procured under the Qualified Parts List (QPL) system, which was administered under the armed services supply center. The joint Army-Navy (JAN) process that evolved under the QPL system was described by two key documents: MIL-M-38510 and MIL-STD-883.

The glory and the curse of MIL-M-38510 was that it was based on "screening-in" quality through a rigid set of tests for each and every device lot, no matter how mature the manufacturing process or how sophisticated the Statistical Process Control (SPC) used to control manufacture.

In contrast, the QML process recognizes that manufacturers apply many process-control techniques to ensure quality and lets them take advantage of the data gathered from the manufacturing and testing process. When the manufacturer can prove a particular step is no longer necessary, it can delete it.

Another advantage of QML is that it qualifies the entire product family via certification of the process flow. Once an IC company's process is certified or listed as QML, the manufacturer must continually meet or improve upon the established baseline under which it qualified.

Under QML, military programs benefit from manufacturers' ability to convert rapidly to new technologies. Reduced screening means reduced cycle times. And because QML makes it possible to eliminate non-value-added manufacturing steps, QML has the potential for cost containment.

In addition to rapid product introduction, reduced cycle time, and potential cost savings, QML devices don't suffer from the defects sometimes induced by an extensive screening process. On the other hand, the QML standard retains configuration control, device traceability, standardized supplier certification, and obsolescence control.

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