Identify the process or machine problems affecting yield
With the waveforms, manufacturing engineers are able to identify the root cause of an issue that is resulting in rejects.
In the example on the left, an automotive manufacturer wanted to address failure rates in electronic throttles at end-of-line engine testing.
Analysis of upstream vacuum test signatures on the throttles showed that only the clear failures were being caught (1). Some throttles were passing the tests (2) because only start and stop pressure (shown by the arrows) were being used to determine pass/fail. The outliers resulted in the downstream failures and high repair costs.
The manufacturer was able to adjust the test; it is only with signature analysis could they catch these hard-to-find defects.
Analyze the data from production to quickly identify how changes in the process – materials, operators, etc. – can affect quality.
In the example below, the manufacturer experienced a higher than usual rejection rate on a part. By analyzing the data, it became clear that the issue was due to the switch from a lead (top) to non-lead bearing (bottom). The non-lead bearing created a different curve; the test was adjusted to accommodate the material change.