Yield and quality control

Which correctly states Little's law, relating work in progress (WIP), throughput and cycle time in a factory?

  1. AWIP = throughput × cycle time
  2. BWIP = throughput ÷ cycle time
  3. CWIP is unrelated to cycle time
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Answer: A. WIP = throughput × cycle time

Little's law states that average WIP equals the product of throughput (output per unit time) and cycle time. It shows that shortening cycle time at the same throughput requires reducing the WIP in the fab.

  • A. Correct. WIP = throughput × cycle time.
  • B. The relationship is multiplication, not division.
  • C. WIP is closely related to cycle time.
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More Yield and quality control questions

  1. What is the analysis called that statistically identifies, from the manufacturing histories of many lots, the tools, chambers, materials and the like commonly used by low-yield lots?
  2. Which statistical process control technique monitors several mutually correlated characteristics together, rather than one at a time, to detect abnormal combinations?
  3. When there are several tools of the same type, what is it called to adjust and manage them so that processing results differ little between tools and chambers?
  4. A wafer yields 500 chips, of which 450 are good. What is the yield of this wafer?
  5. With the same defect density, what generally happens to yield when chip area is increased?