Measurement Tool 2, the person conducting the producibility measurement
determines that each board has six elements - RF, digital, etc. By taking the
sixth root of .85 (each root representing a unique independent element) it is
found that the average first-time yield of each element of the board must be
.97327 or 97.327% to meet the specified 85% goal of the board.
Similarly, if the six elements of the board each have four components, then
the fourth root of .97327 is taken and the first-time yield of each component
must average .9932 or 99.32% to meet the 85% goal of the board.
Worked another way; six elements of the board x four components per element
= 24 opportunities for defects. The required component level yield is then
found by taking the 24th root of the 85% overall goal of the board which would
be .9932. In other words, if all the components were to exhibit a first-time
yield of 99.32%, we could expect a first-time board yield of