Issue link: https://iconnect007.uberflip.com/i/1507822
SEPTEMBER 2023 I PCB007 MAGAZINE 91 1. If Kp < 1, we have minimum Y if n=0: erefore, no inspection or test. (is is the cost to inspect and correct the final product, Np [k 2 + k 1 /q].) 2. If Kp > 1, we have minimum Y if n = N: erefore, 100% inspection or test. (is is the cost to test all bare boards, Nk 1 /q.) e two conditions of n=0 or no testing, and n=N or 100% testing can be plotted in Figure 3. is is the curve of Kp=1, the point of indif- ference. It is the values of p and the reciprocal of p, 1/p=k 2 /k 1 . By calculating the ratio k 2 /k 1 and estimating p, any point above the curve in Figure 3 represents the need to electrical test. Below the curve, no testing is required. Figure 2: Electrical failure rate compared with number of test points. (Source: Testerion Inc., August 1983) Figure 3: Optimum decision on inspection of PCBs. (Source: W.E. Deming to HP, 1981)