Test Strategy
Background
As the number of solder joints on printed circuit assemblies (PCAs) has increased, so has the potential for defects, thereby increasing the need for both test coverage and process improvement. The electronics manufacturing industry needs test and measurement solutions to address loss of physical access and fault coverage at in-circuit test (ICT). Manufacturers also need improved process measurement capabilities to enable higher levels of quality and efficiency in order to reduce conversion costs.iNEMI's Test Strategy Project addressed these challenges through investigation of automated X-ray inspection (AXI) (2D, 3D and partial 3D) and ICT fault coverage and performance. Activities were organized into three working groups: (1) Test Coverage Analysis, (2) Test Vehicle Analysis, and (3) Test Strategy Return on Investment Model.
The team found that many ICT probe removal techniques allow significant probe reduction with an insignificant decrease in defect coverage. AXI demonstrated the highest defect coverage; therefore, the team recommended a combination of AXI inspection with other techniques to achieve the highest ICT probe removal strategies.
The Test Strategy Project also developed a simple cost modeling tool that can be used to define a manufacturing PCA test strategy by estimating the cost of finding and repairing manufacturing assembly defects using various types of test and inspection strategies. This economic model helps communicate the potential needs and benefits of each test technique and helps users understand the impact of removing test stages vs. sampling strategies vs. 100% inspection or test methods.
Cost Model Files
NEMI Test Strategy Cost Model - Rev. 1.0 (Excel file 3.22 MB)
The NEMI Test Strategy Cost Model has the ability to compare two different PCA test strategies in terms of cost, test effectiveness, test time, yield enhancement savings, defects escaping out of the strategy, DPMOs/yield for each test stage, ROI metrics and time-to-market savings. The model uses a spreadsheet format and is intended for post-reflow PCA test strategies.
Test Strategy Cost Model - User's Guide (PDF 560 KB)
This is the user's guide that was developed to help users understand the capabilities of the tool and learn how to utilize the test cost model. The user's guide is a 72-page document with text and images that describe in detail each of the sections of the test cost model and explains, step by step, how to enter all the required information into the model and how to interpret the results on the outputs section. This user's guide also contains a calculations section that explains in detail all the formulas used in the test cost model.
Test Cost Model Presentation (APEX 2003) (PDF 352 KB)
Download the introductory slide set of the Manufacturing Test Strategy Cost Model. This material was presented by the Test Strategy Working Group Project 3 at APEX 2003 on April 1 in Anaheim, CA, USA.