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4.4 Programming & Tuning

Programming and tuning inspection is where raw machine capability turns into reliable judgment. Golden samples and disciplined libraries create a stable foundation, while risk-based limits ensure the system focuses on what truly matters—catching escapes without drowning in cosmetic noise. Iterative feedback, driven by Pareto analysis, keeps false calls under control and makes tuning a structured process instead of a guessing game. Most importantly, inspection programs are not substitutes for process control; they act as sensitive indicators that point back to upstream printing and reflow when patterns emerge.

4.4.1 What “programming & tuning” really means

You’re turning a Golden Board into a repeatable judgment. That’s:

  1. good lighting/slices, 2) lean, reusable library items, 3) sane limits per risk class, and 4) a feedback loop that trims false calls without letting escapes slip through.



4.4.2 Build the right golden set (don’t teach from randoms)

  • Golden board (do not ship): known-good after AOI/AXI/ICT/FCT.
  • Near-limit board: same build, but with “barely OK” features (smallest fillets, highest allowed voids). Teaches the tool what still passes.
  • Bad examples pack: cropped images of real defects (bridges, tombstones, HIP, void clusters) labeled by type.
  • Store top/bottom AOI lighting profiles, AXI slice heights/ROIs, and a one-pager of acceptance limits with each product rev.



4.4.3 Library discipline (the stuff that scales)

  • One package = one library item, reused across products; keep per-finish lighting variants if needed (e.g., ENIG vs OSP).
  • For AOI items: define presence window, pin-1/polarity region, and pad ROIs (solder checks). Avoid using logos/lot text as truth.
  • For AXI items: lock ball count/pitch, slice plane(s), and void % rules (per ball vs total).
  • Naming: <Pkg>_<Pitch/Size>_<Finish if special>_v#. No “temp_final_new2”.



4.4.4 Risk classes & limits (so tuning has guardrails)

  • Class A (must never escape): polarity, missing parts, BGA bridges, critical net shorts → tight limits, review if unsure.
  • Class B (quality/cosmetics): small wetting defects, fillet cosmetics → wider band, bias toward pass with trend tracking.
  • Class C (informational): smudges, silks nicks → chart only; never block WIP.

Put the class on every rule. When in doubt, promote to a stricter class for NPI, then relax after data.



4.4.5 The fast iteration loop (Pareto → change → recheck)

Run 50–200 boards, then:

  1. Pareto false calls by refdes & reason, separate from true defects.
  2. Fix top 3 false-call sources with the smallest change (lighting gain, ROI size, one threshold notch). Avoid global relax.
  3. Re-run a mini-lot (10 boards) → confirm false calls drop and escapes stay flat.
  4. Version-bump the program; add a 1-line “why” in the changelog.

Repeat weekly until false calls settle under your target (e.g., ≤0.5–1.0/board), then switch to monthly trims.



4.4.6 When to touch process, not code

Use inspection as a thermometer, not a hammer:

  • Bridging calls cluster → check SPI area/cleaning and separation (7.5) before widening AOI thresholds.
  • BGA voids high across a lot → revisit QFN/BGA windowing (7.4) or soak/TAL (9.2), not AXI limits.
  • Tombstones → re-balance chip apertures (7.4) and confirm ramp rate (9.1).

If the Pareto smells like a process drift, fix the line and keep inspection tight.



4.4.7 ML/auto-learn without regret

  • Train on diverse lots (mask colors, finishes, vendors).
  • Keep a holdout set (never trained on) for spot checks every rev.
  • Save example images with pass/fail scores; if a model decision isn’t explainable, don’t use it on Class A items.
  • Re-train only on a schedule (e.g., monthly), not mid-shift.



4.4.8 Change control (tie to ECNs so docs match the floor)

  • AOI/AXI program rev increments with any ECN that changes land patterns, silks, or components.
  • Bundle: program file, lighting/slice settings, limits sheet, golden images.
  • Store under the product’s Golden Recipe so stations load by ID, not memory.



4.4.9 Roles & cadence (who does what)

  • AOI/AXI programmer (R): builds/edits libraries, runs Pareto loops.
  • QE (A): sets limits, classes, and approves changes.
  • PE/ME (C): decides when issues are process not program and triggers stencil/profile fixes.
  • Operators (I): log nuisance calls accurately; don’t “teach around” defects.

Daily: clear review queue.
Weekly: Pareto + top-3 trims.
Monthly: program health (false calls/escapes trend) + ML retrain (if used).



4.4.10 Pocket checklists

Before first lot

  • Golden/near-limit/defect packs ready
  • Libraries reused (no one-offs); risk classes set
  • Limits sheet posted; lighting/slices saved in recipe

After 50–200 boards

  • False-call Pareto built (by refdes/reason)
  • Smallest fixes applied; mini-lot verified
  • Program rev’d with a clear “why”

Ongoing

  • Escapes cross-checked at ICT/FCT (with image backlinks)
  • Process drift flagged upstream (SPI/oven) before loosening rules
  • ECN ties intact; Golden Recipe bundle current


When inspection programs are built from trusted golden sets, refined with disciplined iteration, and connected to process feedback, they deliver stable, low-noise performance. The result is inspection that works as an efficient safeguard—quietly filtering risk, accelerating debug, and keeping production flow steady.

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