DFT / ATPG · All levels

Test Signoff Reports: Comparison Matrix

Comparison Matrix for Test Signoff Reports.

Comparison matrix

Shift speed, capture strategy, and pattern scheduling trade risk and throughput.

diagram

+------------------+----------------+----------------+----------------+
| Approach         | Strength       | Weakness       | Best when      |
+------------------+----------------+----------------+----------------+
| Conservative     | safe           | higher cost    | ramp-sensitive |
| Balanced         | practical      | needs rigor    | production     |
| Aggressive       | fast           | escape risk    | schedule pressure |
| Architecture     | durable        | slow           | repeated pain  |
+------------------+----------------+----------------+----------------+

When to choose each approach

Tie approach to product risk and tester constraints

Interview traps

Optimizing one metric only
No regression ownership

Evidence comparison

diagram

DFT EVIDENCE MATRIX - Test Signoff Reports

+-------------------+------------------------+--------------------------+-------------------------+
| Evidence           | Tells you              | Does not prove           | Next action             |
+-------------------+------------------------+--------------------------+-------------------------+
| coverage report    | fault detect trends    | silicon root cause       | inspect bucket details  |
| pattern diff       | generation changes     | architecture quality     | replay suspect patterns |
| timing/power report| test closure margin    | diagnosis confidence     | correlate fail logs     |
| diagnosis summary  | likely defect classes  | ownership decision       | assign action owner     |
| signoff checklist  | process completeness   | correctness of evidence  | peer review artifacts   |
+-------------------+------------------------+--------------------------+-------------------------+

DFT deep dive

Test signoff fails when shift/capture timing and test power are treated independently.

Concept diagram

diagram

TEST SIGNOFF LOOP

test SDC -> shift/capture timing -> power-aware ATPG -> IR validation -> release

Metric graph

diagram

TEST CURRENT

functional current  baseline
scan shift current  peak-risk zone

Reports and artifacts

test-mode STA report
shift/capture split
test power IR map
waiver tracker

Mini case study

At-speed patterns passed timing but failed in production due to peak shift IR; staggered capture and power-aware fill resolved.

Debug branches

Tag test and functional corners separately
Check hold in shift mode
Correlate fail bins with power hotspots

Senior review question

Ask: what evidence proves this DFT decision is safe for production?

Key takeaways

State metric, lot/corner context, and pattern tag with every claim.
Treat timing, power, and quality as one signoff problem.

Common pitfalls

Chasing coverage without legality checks.
Ignoring test-power side effects of pattern changes.
Debugging silicon without reproducible tags.

Principal DFT review addendum

Test signoff consolidates coverage, timing, power, and diagnosis evidence into a release decision with explicit ownership and waivers.

Metric: test readiness score, unresolved waivers, production release risk

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