Defect-Fault Mapping Problems

Using the Defect-Fault Mapping Calculator solve the following problems:

Problem 1

Assume you have characterized your tester for the assembly of a particular bare die to a thin film interconnect.  The characterization is as follows 75% of wirebond defects appear as open circuits, 5% of placement errors appear as short circuits, and 85% of placement errors appear as open circuits.  If the placement process is 300 ppm (1 placement per board) and the wirebonding process is 90 ppm (400 I/O on the die your are interested in),

a) What fault coverages are necessary to obtain a defect coverage of 2.9% for wirebond defects?

b) What is the defect coverage for placement defects?  Does it depend on the fault coverages, why or why not?

c) Does the solution depend on whether the remaining wirebond and placement defects can be mapped to a particular fault (other than open or short circuit) or not?

Problem 2

In problem 1 above, suppose that we desire a defect coverage of 40% for placement errors. 

a) What quality (in ppm) is needed in the placement process?  Explain.