Large-scale integrated (LSI) circuit chips are made in one department of an elec
ID: 423907 • Letter: L
Question
Large-scale integrated (LSI) circuit chips are made in one department of an electronics firm. These chips are incorporated into analog devices that are then encased in epoxy. The yield is not particularly good for LSI manufacture, so the AQL specified by that department is 17% while the LTPD acceptable by the assembly department is 50%. Assume the company is willing to accept a consumers risk of 10 percent and a producer's risk of 5 percent. Use Exhibit 10.16. a. Find the sample size. (Round up your answer to the next whole number.) Sample size b. How would you tell someone to do the test? Randomly sample LSI using the sample size from part a, reject the lot if more than defectiveExplanation / Answer
c is the acceptance number, that is, the maximum number of defectives which can be tolerated. Any number of defectives above c will reject the sample.
The table given in exhibit 13.10 gives the method to calculate the ideal sample size when the consumer risk is 5% and producer risk is 10% based on the values of AQL and LTPD. As per the given values, we need to calculate the range of acceptance number,c, which is based on LTPD/AQL. Here,
LTPD/AQL=50/17=2.94, so, c should be between 2 and 3.
From above table, sample size is given by n/AQL. For c=2 and c=3, n is 82 and 137 respectively. We can choose any value out of them, and this ensures that the producer risk of 10%.
Answers are
a.82, b.2 OR a.137, b.3
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