Testing and inspection

What is it called when good chips are judged defective and discarded because test limits are too strict or measurements are unstable?

  1. AGuard band
  2. BOverkill (excessive rejection)
  3. CTest escape
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Answer: B. Overkill (excessive rejection)

Overkill means judging good parts as defective, unnecessarily lowering yield and raising cost. Conversely, passing a defective part as good is a test escape, which leads to field failures. Test conditions are set by balancing the two.

  • A. A guard band is the margin of limits tightened beyond specification to allow for error.
  • B. Correct. It is judging good parts as defective.
  • C. A test escape is passing a defective part as good.
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More Testing and inspection questions

  1. In memory testing, what is the main purpose of making a map recording which bits at which addresses failed?
  2. When compressing scan test outputs, why must signals whose value (0 or 1) is undetermined in simulation (unknowns, X) be removed?
  3. In testing high-speed serial interfaces, which method loops the chip's transmitter output back to its receiver so the chip itself verifies communication?
  4. What is the technique called that dynamically changes test items or limits per chip or per lot based on intermediate results and statistics, such as from wafer test?
  5. In AD converter testing, what is the main purpose of inputting a slowly varying sine wave or similar and counting how often each output code appears (a histogram)?