Commercial-off-the-shelf components, or COTS as they are more commonly called, by definition represent those used in commercial applications and environments. Since 1994, a government mandate has required COTS usage on military electronic applications.

This was done in order to transfer much of the cost associated with development and design of custom systems to the commercial sector, where already highly advanced state-of-the-art electronics reside. With this change, and the usage of commercial components that include

IC analog and linear comparators, multipliers, voltage regulators, and processors, has also come many design issues such as increased component obsolescence, difficulty of traceability, and issues with long-term supply. These issues are essentially due to the vast and rapid evolution of commercial electronic technologies. The life expectancy of these component types is relatively short considering the long life expectancy and service terms of most military platforms.

A typical lifetime for a microprocessor is two years and for linear devices is eight years. The life expectancy for most military systems exceeds 20 years. Obsolescence has become a fundamental problem, and what becomes necessary is to either find a replacement component or create a redesign. The Industrial Advisory Board (IAB) of the EMPF has started a collaboration to focus on two areas of component qualification: 1) Obsolescence of common components, namely, the identification of replacements by sharing non-recurring engineering information and, 2) COTS component qualification, specifically, of those that are either from a non-qualified vendor or are required to be qualified outside of the originally designed environment.

To accomplish this, the IAB will build on the success of the Electronics Miniaturization for Missile Applications (EMMA) program that evaluated the feasibility of COTS incorporation into guidance and navigation electronics for missile applications. Specifically, the program examined the reliability of high I/O pin count advanced package styles such as flip chip components as well as:

• PBGA (plastic ball grid array)
• DBGA (dimpled ball grid array)
• TEBGA (thermally enhanced ball grid array)
• WBCSP (wire bond chip scale package)
• WFRCSP (wafer chip scale package)

The goal of the collaboration is to combine member information and collectively solve both obsolescence problems and COTS component qualification issues. For example: if member A identifies a common component that they must replace, and within the combined pool of information member C has already shown that another component is applicable for that given requirement, then there is immediate benefit.

Member A does not have to perform additional component qualification testing and incur an engineering charge. Additional benefits expected from this effort include substantial savings through the elimination of redundant efforts, plus the risk reduction in both schedule and in the sustainment of fielded systems. In addition, participants could collectively negotiate common part buys and therefore achieve the best price and increase the likelihood of future part availability.

To better define qualification testing, some discussion is necessary, andBoeing has contributed several excellent definitions to the effort:

Qualification Testing - A series of mechanical, electrical, and environmental inspections that is intended to verify that materials, design, performance, and long term reliability of the part are consistent with the specification and intended application, and to assure that manufacturer processes are controlled from lot to lot. Due to the fact that qualification testing encompasses different test programs, each conducted according to its own sampling plan and for its own purpose, it may be helpful to define and briefly discuss each element:

Screening - This is conducted on 100 percent of product of each production lot. Screening includes functional (electrical) testing under ambient conditions plus an abbreviated environmental test program known as Environmental Stress Screening (ESS). The purpose of ESS is to exercise the part sufficiently to remove nonconforming parts, parts with random defects, and parts likely to experience infant mortality. However, the environment should not be too severe so as to induce any latent failure mechanisms nor consume a significant portion of the part's operating life. This concept can be illustrated via the reliability model "bathtub curve" that is depicted in Figure 1.

Temperature Range and Functionality - The purpose of this test sequence is to evaluate both the static and dynamic electrical performance of an electrical, electronic, or electromechanical (EEE) part across its intended operating temperature range. Such testing is typically conducted on a sample basis on every production lot.

Robustness to Assembly Processing - The purpose of this test sequence is to address manufacturing defects that would have a producibility impact at the Circuit Card Assembly (CCA) level. Robustness to Assembly Processing testing typically evaluates a part's resistance to typical cleaning solvents, the ability of its leads to accept solder, and the mechanical strength of leads, terminals, and bond wires (as applicable). Such testing is typically conducted on a sample basis on every production lot.

Life Testing - The purpose of life testing is to simulate intended product operating life by applying static and dynamic electrical stimuli under high-temperature conditions in order to accelerate the aging process. The duration of testing (measured in hours) simulates the number of years a given product is intended to operate reliably. This testing may include High-Temperature Reverse Bias (HTRB) and dynamic burn-in. Such testing is a repeat of a portion of the screening testing except for longer durations that are intended to simulate a parts entire operating life as opposed to just screening out infant mortalities (Figure 1). Testing is typically conducted on a sample basis at certain intervals during the production cycle or after a certain number of production lots.

Environmental Stress Test - The purpose of this testing is to simulate product life in its use and storage environments. Like life testing, the aging process is accelerated, this time by repeatedly cycling the part through typical operating and storage environmental conditions. Such testing may include thermal shock, temperature cycling, moisture resistance testing, vibration, mechanical shock, and hermeticity (as applicable). Such testing is typically conducted on a sample basis at certain intervals during the production cycle or after a certain number of production lots.

These definitions provide a thorough understanding of the type of necessary qualification that components must undergo in order to be qualified for military and demanding commercial applications. Another recent trend is the increasing demand for components that have requirements for space applications. Rad-hard Pentium and PowerPC processors are being developed and SRAM, ASICs, and EEPROMs are already available. These conditions then make for another level of qualification testing with stringent demands.

ACI is working alongside Boeing, Raytheon, Rockwell Collins, ITT, and Honeywell to build a collective knowledge base of part information, requirements, component obsolescence, and qualification data. Doing so will avoid duplicate efforts in resolving design and sustainment issues, the concurrent cost associated with these tasks. For more information on this effort, please contact Mike Frederickson at (610) 362-1200.