SMTA International Conference Proceedings


HOW DEFECT COVERAGE AS A VARIABLE CAN BE USED TO DETERMINE TEST AND INSPECTION STRATEGIES

Author: Stig Oresjo
Company: Agilent Technologies, Inc.
Date Published: 9/25/2005   Conference: SMTA International


Abstract: Compared to just ten years ago, selecting the optimal test / inspection strategy today is a more challenging task. With the new automatic inspection technologies such as postreflow Automatic Optical Inspection (AOI) and Automatic X-ray Inspection (AXI) more tools are available to find defects.

Also the use of Solder Paste Inspection (SPI) and pre-reflow AOI as defect prevention tools makes creating a test / inspection strategy with optimal test coverage a challenging task. This paper will cover the concepts of PCOLA (Presence, Correctness, Orientation, Live, and Alignment) coverage for component defects and the SOQ (Short, Open, and Quality) coverage for connection defects.

The paper will show how these characteristics can be scored for electrical test as well as imaging inspection. It will also describe how a combined AOI, AXI, and ICT (In-circuit test) strategy coverage number can be calculated, and used to give a coverage score to provide information on the right trade-offs in coverage on the different platforms. Examples on how inspection complements electrical test will be covered as well.

Key words: Test coverage, scoring, combined coverage, ICT, AOI, AXI, PCOLA, SOQ



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