Test Process Problems

Using the Test Process Step Calculator solve the following problems:

Problem 1

Assume you have a process that expends $150 per part and produces parts with 200 ppm defects.   

a) What is the incoming yield?

b) If the test cost is $20/part and the fault coverage is 90% (assume the test yield is 100%), what are the cost and yield of parts passed by the test step?

c) If 500 parts enter the test step, how many are scrapped by the test step described above?  How many pass the test step?

Problem 2

Re-create the plot of Output Yield versus Fault Coverage presented in the lecture using the calculator.

a) At 100% fault coverage, why is the output yield always 100% independent of the input yield?

b) At 0% fault coverage, what is the value of the output yield, why?

c) What is the output yield as a function of fault coverage when input yield is 100%?

Problem 3

Notice that in the calculator, the minimum value of the incoming yield is limited to 1% (rather than 0%).  This is because the equations derived for describing the basic test step (notably the equation for Cost out) do not support this limit.  Re-derive the relation for Cost out of a test step for the limiting case as the input yield approaches zero.