Issue link: https://iconnect007.uberflip.com/i/1529411
46 PCB007 MAGAZINE I NOVEMBER 2024 2. Conversational Statistics, by Harry V. Roberts, University Business Series-University of Chicago, December 1974. Provided by Hewlett-Packard and Stanford University. 3. NIST Statistical Engineering Handbook. 24 Essential Skills for Engineers, by Happy Holden. 5. "Happy Thoughts: Calculate Your Fabrication Capability Coefficient," by Happy Holden, CircuiTree Magazine, Feb 15, 2006. Happy Holden has worked in printed circuit technology since 1970 with Hewlett- Packard, NanYa Westwood, Merix, Foxconn, and Gentex. He is currently a contributing technical editor with I-Connect007, and the author of Automation and Advanced Procedures in PCB Fabrication, and 24 Essential Skills for Engineers. To read past columns, click here. Constant A determines the slope at the inflec- tion of the yield curve and constant B deter- mines the X-axis location of the inflection. e confidence level in yield predictability is determined by the statistical margin of error in the calculation of A and B. Figure 2 shows the characteristic yield vs. PCB complexity and the influence of the coefficients A and B. Conclusion e FPY model can be applied to new designs or new orders by a fabricator. By applying this model, you can be alerted to concerns over the first fabrication of a particular board. e method of determining your fabrication coeffi- cients (A & B) from electrical test data is avail- able in the I-Connect007 book library 5 . PCB007 References 1. "The Design of Optimum Multifactorial Exper- iments," by R.L. Plackett and J.P. Burman, Biometrika, Vol. 33, Part 1, April 1946. Figure 2: The first-pass yield is reflected in the overall yields in production. Improving the FPY will improve all board yields (move the curve to the right) and DFM feedback and tooling helps simplify a board that moves its complexity to the left.