Question

Testing Of Digital Systems

A digital system board uses 40 ICs manufactured with two different independent

processes. 25 ICs are manufactured using process 1 that has 80 % yield and 90 % fault

coverage. The cost of these ICs is 10 KD each. The remaining ICs (15) are manufactured

using process 2 with 85 % yield and 95 % fault coverage. The cost of these ICs is 20 KD

each. The board manufacturer spends 50 KD on the design and test of each board (even

those who are found defective). Assume all boards found defective are discarded and the

test used to detect such boards is perfect, what is the average cost of manufacturing a good

board? Hints: The cost of the defective boards need to be included in the total cost. Also,

use the DL for the unclustered random defects.

Answer 1

Plotted fallout rate function, 1 - Y(T), given by: Fitting yields Af=2.1 and β=0.083. This gives f = Af/A = 2.1/(0.94*0.88) = 2.54 faults/sq. cm. Using these values, Eq (5) gives Y = 76.23 and (6) gives DL = 168 for T=0.9979