Original Date: 11/01/2004
Revision Date: 01/18/2007
Best Practice : Parts Selection and Management
The Center for Advanced Life-Cycle Engineering’s Parts Selection and Management methodology helps companies of all sizes implement effective part selection and management procedures. By employing the methodology effectively, an organization does not have to conduct expensive on-site audits and can avoid warranty- and/or product-recall problems that commonly result from selection of sub-par parts.
The Center for Advanced Life-Cycle Engineering (CALCE) has developed a methodology for selecting and managing electronic parts that provides users a means of evaluating the life-cycle risk posed by candidate parts before selecting them for use in their systems. The methodology also enables the capture of lessons learned during use of the selected parts in the application (product) to provide feedback for use in future decisions.
The rapid pace of technology in the area of electronics and the transition from military grade parts to commercial ones have created a new supply chain dynamic that has tremendous impact, not only on the commercial world, but on the Military/Aerospace community and other makers and users of electronic systems requiring high reliability. In the past, the Department of Defense represented a significant part of the electronics market, and was influential in directing developments and standards used to guide their manufacturing processes through MIL SPECs and STDs. During the 1980s and 1990s, the commercial electronics industry began to boom, driven by industry and consumer demand for computers, communication equipment, and consumer electronics. Electronic component packaging trends are now heavily driven by market application requirements and device technology. Considerations include speed, miniaturization, functionality, improved cost and performance, portability, weight, and other factors. At the same time, the supply chain has transformed into a “supply web” as vertically integrated companies that “did it all” (i.e., made the chips, then packaged, tested, and integrated them into products) have given way to a diverse array of companies that specialize in specific steps in the overall design, build, and test process. Although military standards have shifted to improved and more flexible commercial standards, the latter often do not go far enough to control processes and ensure product quality and reliability. The complexity of today’s electronic products and systems and the supply chain that feeds them demand a sound and comprehensive method for selecting and managing parts.
The CALCE Selection and Management methodology (Figure 2-2) helps maximize profits, minimize time-to-profit, provide product differentiation, make effective use of the global supply chain, and enable the assessment, mitigation, and management of life-cycle risks associated with the selection and use of electronic parts. The process consists of the following steps:
1. A product’s Requirements and Constraints are defined by customer demands and the builder’s core competencies, culture, and goals, which enable designers to choose parts that conform to a set of engineering criteria. A product specification can be created and used as a basis for part selection.
2. Technology Sensing determines when a technology is (or will be) available and mature enough for use, and when it will become obsolete. Potentially disruptive technologies are also considered (e.g., the transition to lead-free solders and component lead finishes).
3. A Candidate Part must conform to functional, electrical, mechanical, and environmental requirements and be available at reasonable cost (this is a part pre-selection step).
4. During Manufacturer Assessment, a part maker’s ability to produce parts with consistent quality and provide customer support are evaluated.
5. Part Assessment determines the specific quality and reliability of the part and the adequacy of the manufacturer’s recommended assembly guidelines.
6. Distributor Assessment is conducted to evaluate the distributor’s ability to provide parts without compromising their quality and reliability, and without becoming a bottleneck in the supply chain.
7. If and when the candidate part meets the above criteria, it moves to the Application-Dependent Assessment Phase. (The methodology also provides some criteria for the allowable use of a rejected part when no acceptable alternative can be found.) Application-Dependent Assessment begins with a determination of the local environment – the environment in the vicinity of the part as it is exposed to assembly, storage, handling, and use environments – including its life cycle.
8. Performance Assessment evaluates the part’s ability to meet product functionality and electrical performance requirements. In most cases, the part manufacturer’s ratings (as specified in data sheets) are used to determine limiting values for minimum and maximum loads to which the part can be subjected.
9. Reliability Assessment finds or determines the part’s ability to perform according to specification in the life-cycle environment for a specified period of time. Manufacturer-provided integrity (qualification and reliability monitoring) test data can help in the assessment. Reliability Assessment is conducted through the use of integrity test data, virtual qualification (VQ) physics-of-failure (PoF) simulation methodology results, or accelerated testing if necessary.
10. Assembly Assessment determines if the part can be assembled into the product, if it can be interconnected into its assembly and tested, and reworked during and after assembly if necessary, .
11. Life-cycle Obsolescence Assessment is conducted to determine the availability mismatch between the part and the product in which it will be used. The objective is to prevent the selection of parts that are or will soon be obsolete, or will be difficult to manage once they become obsolete. If no other part is available, an obsolescence mitigation strategy (e.g., life-time buy) may be employed.
Once a part is selected, resources must be applied to risk management of the life-cycle factors including supply chain management, obsolescence management, manufacturing and assembly feedback, warranty management, and field failure and root-cause analysis.
Figure 2-2. Parts Selection and Management Process
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