DFT-PD Handoff: Worked Example

Worked example

Worked Example for DFT-PD Handoff focuses on handoff issue count, late-stage DFT ECO volume, closure turnaround. The goal is to convert metric movement into mechanism, owner, and release decision.

A release review shows regression on handoff issue count, late-stage DFT ECO volume, closure turnaround. The strongest first move is to freeze evidence, isolate one failing bucket, and prove mechanism before changing flow knobs.

Sequence under inspection

DFT FLOW - DFT-PD Handoff

scan insertion -> chain stitch -> compression map -> ATPG -> tester apply -> diagnosis
      |                |                |            |             |
 controllability   shift balance    channel use   coverage     silicon correlation

Primary metric: handoff issue count, late-stage DFT ECO volume, closure turnaround

DFT-PD handoff checklist

chain constraints + test clocks + legal placements + signoff criteria
                      -> PD implementation contract

1. Capture failing report and exact run tags.

2. Tag scenario (mode, lot/corner, pattern class).

3. Trace first dependency that changed.

4. Compare against handoff checklist, chain constraint package, ownership matrix.

5. Choose one reversible fix and predefine regression checks.

Did the fix work?

BEFORE / AFTER - DFT-PD Handoff

metric quality
  ^
  |                    --- release target
  |      o regressed
  |           o baseline
  |                o after fix
  +-------------------------------> closure iteration

Prove quality, timing, and test-power all moved safely.

DFT deep dive

Physical integration quality decides whether DFT architecture survives implementation realities.

Concept diagram

PHYSICAL DFT FLOW

chain planning -> floorplan placement -> route -> test timing/power validation

Metric graph

ROUTING BURDEN

poor chain order -> longer routes -> more hold buffers

Reports and artifacts

• scan physical wirelength

• congestion heatmap

• test clock skew

• handoff issue tracker

Mini case study

Late scan reorder reduced route detours and eliminated a major shift hold cluster before signoff.

Debug branches

• Correlate chain order with congestion

• Place compression logic near chain clusters

• Keep DFT-PD handoff versioned

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

Clear DFT-to-PD contracts for chain rules, test clocks, and legal placement constraints prevent expensive late-stage churn.

Metric: handoff issue count, late-stage DFT ECO volume, closure turnaround