Summary of steps to fully test for I/O-to-I/O shorts
A companion table to "Continuity testing," which we published in our August 2005 issue.
C.H. Lim -- Test & Measurement World, 7/26/2005 2:49:00 PM
| Step 1 | Perform parallel continuity testing by setting device grounds to reference potential (usually ground potential).
This step detects continuity open on all singular I/O’s that are not fanned out from an internally shorted plane like the device power supply or ground.
All I/O’s adjacent to the reference ground I/O’s used for this parallel continuity test can be detected when shorted to the ground I/O’s themselves.
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| Step 2 |
Vertically ground alternate columns on the package plus the device ground I/O’s and test for continuity on remaining I/O’s. Note that if the device contains multiple supplies and grounds internally shorted together, all of them will have the same potential when any one of them is grounded.  This step detects I/O-to-I/O shorts horizontally and diagonally. |
| Step 3 | Horizontally ground alternate rows on the package plus the device ground I/O’s and test for continuity on remaining I/O’s. As before, all supplies and grounds internally connected on the die have the same potential when any one of them is grounded.
 This step detects I/O-to-I/O shorts vertically. |
| Step 4 | By doing a logical AND followed by a logical XOR operation on I/O’s with undetectable shorts from steps 2 and steps 3 above, identify the final map of I/O’s that would not fail when shorted to adjacent pins. From here, ground all device supplies and grounds and test for continuity on the identified I/O’s to complete the test iteration.
This final step completes the detection of I/O-to-I/O short on the package.
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