4.5 SPC & Dashboards

4.5.1 SPC Fundamentals in Production

ThinkSPC ofinvolves itmonitoring key performance indicators (KPIs) to distinguish common cause variation (inherent, acceptable process noise) from special cause variation (a sudden, specific problem like a car:clogged nozzle or broken sensor).

• SpeedometerProcess Control: →SPC SPIis transferabout efficiency (are we printingcontrolling the rightmean volume?(µ) and the variation (σ) of critical parameters like Solder Paste Transfer Efficiency (TE).
• FuelThe lightGoal: →The Mounteraim starvation/miss rates (are feeders aboutis to bitemaintain us?)
• Engineprocesses temp → Reflow TAL/peak/ΔT (are we cooking the board right?)

If any gauge moves, you nudgein a knobstate of nowstatistical control, notensuring afterthat AOIthe screams.process is consistently

4.5.2 TheKey “few,Process vital” metricsMetrics (byBy station)Station)

StartEffective withSPC these.requires Addtracking morethe only"few, ifvital" theyparameters changethat decisions.predict downstream failure, rather than monitoring everything.

4.5.3 SimpleDashboards chartsand thatAlarm operatorsTiers

Effective readdashboards use visual alerts to enforce a standardized response protocol. Every deviation must be tied to a documented action (the "if this, then that" playbook).

A) Visualization

• Control Charts: The I-MR (Individuals &and Moving Range) chart is standard for tracking continuous data like SPI TE and Reflow TAL/peakPeak, pershowing panel.the process mean (µ) and the variation (σ) over time.
• p-chartsTraffic Lights: forGreen/Yellow/Red AOIstatus falseindicators calls/board.
• Runclearly chartscommunicate (sparklines)the forhealth starvationof minutes,each misses/retries, wipes/board.parameter.

B) Alarm Tiers

KeepAlarms must be tiered to prevent nuisance alerts from overwhelming the visualsoperator, dumb-clear:ensuring trafficonly lightscritical (green/yellow/red),issues lasthalt 50 panels, and a vertical line labeled “change made” whenever someone tweaks a recipe or cleans optics. If people can’t read it at 2 meters, it’s too fancy.production.

4.5.4 Alarm tiers (decide once, use everywhere)

Make the MES or line PC enforce this—humans forget when the line is hot.

4.5.5 Closing the loop (the “if this, then that” map)

Tie each dashboard needle to a small, specific action:

• SPI TE low on chips (Cpk <1.0) → reduce blade pressure one notch and shorten clean interval; recheck next 3 panels.
• SPI area creep near fine pitch → slow separation 10–20%; if persists, wet+vac, then inspect apertures at next stencil spin.
• PnP miss spikes on Feeder 12 → verify peel path, run 20 dry picks; if still bad, swap feeder; quarantine reel lot.
• Starvation minutes climbing on constraint → pull next splice earlier (countdown threshold), load spare pre-threaded feeder.
• TAL short on cold TC → slow belt a touch (time first), then re-aim late zone by +3–5 °C.
• ΔT at peak > target → add soak 10–20 s via mid-zone setpoints; tick blowers up one step.
• AOI bridges rising in one region → check printer separation and cleaning; don’t widen AOI until print is fixed.
• AXI QFN voids trending up → verify paste lot/date; lengthen soak slightly; consider N₂ A/B run.

These moves should be printed next to the screen. No guessing.

4.5.6 Roles & views (one dashboard does not fit all)

• Operator view (per station): 3–5 gauges, next-action button (“Add clean now”, “Check Feeder 12”), and clear pass/stop banner.
• Lead / Supervisor: line balance (cycle time per machine), red/yellow counts per hour, top 3 issues to clear this shift.
• QE/PE weekly: Cp/Cpk trend by family, escapes vs AOI/AXI limits, before/after of any recipe or stencil change.
• Management: OEE (Availability/Performance/Quality) plus first-pass yield. No microscope photos.

4.5.7 Make data trustworthy (plumbing that matters)

• Everything gets an ID: recipe revs (printer/PnP/oven), stencil ID, paste lot, feeder IDs, operator badge, WO/panel/SN.
• One time base: all stations sync to the same clock so panel histories align.
• Auto-attach evidence: SPI/AOI/AXI images and reflow plots stored against the panel ID; no screenshots in chat apps.
• Annotate changes: pressing “changed belt speed +5 mm/min” drops a vertical line and a note on charts.
  

4.5.8 Start small (a rollout that sticks)

1. Pick one product and wire SPI TE Cpk, wipes/board, PnP misses, TAL/peak, AOI false calls.
2. Agree alarm tiers and the first corrections (Section 10.5.5).
3. Run two weeks; collect “we touched X, chart did Y” stories.
4. Freeze the layout; clone to the next product with only limit tweaks.
   

4.5.9 Common traps (and quick escapes)

• Too many charts. Result: no one looks. Trim to the five that drive actions.
• Alarms with no playbook. Result: people mute them. Add the button that does the first fix.
• Averages across families. Result: masked trouble. Always split by feature family (chips/QFN/BGA/thermal).
• Goal-post moving. Result: pretty charts, bad product. Change the process, not the spec, unless customer agrees.

4.5.10 Pocket checklists

Designing the dashboard

• 5–7 metrics total; split by feature family where relevant
• Green/Yellow/Red bands defined; MES enforces Stop tier
• One-clickrecommend first correction per(e.g., alarm"Wipe Stencil Now").

Supervisor enforces immediate corrective action.

DailyRed use(Stop)

Any

• Operatorsdata clearpoint warns withexceeds the buttonedSpecification action;Limit notes(USL/LSL) auto-loggedor a sustained violation of the C_pk floor.

  Hard stop of the line, mandatory engineering sign-off to resume.

  Open Non-Conformance Report (NCR) and conduct root cause analysis.

  4.5.4 Closing the Loop (The Corrective Cycle)

  The primary function of the SPC system is to enable the closed-loop feedback that drives continuous process improvement.

  1. Detection: An alarm tier (Yellow or Red) is triggered by a metric drift (e.g., SPI TE µ drops 5 points).
  2. Correction:Leads reviewThe topoperator 3executes issuesthe atpredefined break;First assignCorrection quick(e.g., fixesincrease squeegee speed slightly). This must be a simple, single-parameter fix.
  3. Annotation:QE samplesThe escapesaction vstaken AOI/AXIis andautomatically feedslogged backagainst tothe processtime/product ifon trend
     

Changethe control