May 22, 2003
The NEMI Test Strategy Project was organized to address the loss of physical access and fault coverage at in-circuit test (ICT) caused by the physical space constraints of increasingly dense interconnections and packaging designs. Project activities were organized into three working groups: test coverage analysis, test vehicle analysis and test strategy cost model.
Reduced fault coverage, combined with limited diagnostic resolution at ICT and functional test (FT), can lead to excessive debug times. Electronics manufacturers are finding that they can no longer use a single method of test for PCAs and are increasingly combining ICT with AOI (automated optical inspection) and AXI (automated x-ray inspection) techniques. However, it is often difficult to know which method - or combination of methods - will provide the best results.
"Our team's goal was to develop a simple cost modeling tool that could be utilized to make decisions between manufacturing test strategies," said Rosa Reinosa, test program manager for HP and leader of the test cost model team. "Our approach was to create a generic, industry-standard economic model, leveraging our companies' respective economic models to produce a common solution."
Six companies participated in the test cost model project team: Agilent Technologies Inc., Delphi Delco Electronics Systems, HP, Intel Corporation, Solectron Corporation and Teradyne Inc. The cost model they developed estimates the cost of finding and repairing manufacturing assembly defects using various types of test and inspection strategies. Users of this model should be able to define the potential advantages and disadvantages of each test technique, and to understand the impact of removing test stages vs. sampling strategies vs. 100% inspection or test methods.
The NEMI test strategy cost model is intended to enable companies to make trade-off analyses and decisions based on the financial impact that a strategy may have on an organization. The model has the ability to compare two different PCA test strategies and, for each strategy, provide cost, yield enhancement savings, defects escaping out of the strategy, DPMO or yield for each test stage, ROI (return on investment) metrics and time-to-market savings.
Several cost variables are considered in the model, including equipment, maintenance, scrap, repair and field return costs. To determine the ROI, the tool utilizes the initial investment, payback, net present value and internal rate of return calculations. For the time-to-market analysis, investments in R&D, cost of goods sold (COGS), sales and marketing, and general administrative costs are factored into the equation. A detailed user's guide (also available on the NEMI website) walks users through all of the steps and the inputs required for the calculations.
"The model can compare two different test strategies and provide visibility to strategy costs and potential savings in warranty costs, test effectiveness and yield improvement," explained Carlos Michel, test engineer for HP and co-leader of the test cost model team. "The user enters into the spreadsheet detailed information about the PCA to be tested and about the test strategies under evaluation. Of course, the more complete and accurate the information entered, the more accurate the outputs of the model will be. However, if an input is unknown due to lack of data because there is no history on the product's strategy, the user can enable the model's default values, which are built into the tool."
The output of the model provides a description of the yield and defect levels achieved at each test stage, a summary of costs, a graphical cost comparison of the strategies, ROI metrics and time-to-market savings.
"We would like to see industry-wide adoption of this test strategy cost model," said Michel. "The methodologies utilized across industry today generate different results because they are not based on a common set of financial drivers. Standardization of the economic analysis of production test strategies will bring consistency to the overall approach for determining the financial impact of various test techniques."
About NEMI
The National Electronics Manufacturing Initiative's mission is to facilitate leadership of the North American electronics manufacturing supply chain. Based in Herndon, Va., the industry-led consortium is made up of approximately 65 electronics manufacturers, suppliers, industry associations and consortia, government agencies and universities. NEMI roadmaps the needs of the North American electronics industry, identifies gaps in the technology infrastructure, establishes implementation projects to eliminate these gaps (both business and technical), and stimulates standards activities to speed the introduction of new technologies. The consortium also works with government, universities and other funding agencies to set priorities for future industry needs and R&D initiatives. For additional information about NEMI, visit http://www.nemi.org.
For further information:
Cynthia Williams
207-871-1260
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