Reviewed by S&M Co.Ltd’s SMT engineering team (founded 2000). This guide reflects common commissioning and audit-prep practices used across multi-vendor SMT lines.
Editorial policy: We prioritize published standards and official specifications. When a detail is an industry convention (not a requirement), we label it as such. We update references when major standard versions change.
Automatic PCB conveyors aren’t background furniture. They decide how safely boards hand off, how reliably data flows across the line, and how audit-ready your operation is. In this guide, we focus on the compliance driver that matters most for modern SMT lines—interconnect and traceability—while showing exactly how conveyor choices and validation practices reduce handling/fixture damage and lift first pass yield (FPY). We’ll stay neutral, standards-anchored, and practical: no proprietary claims, just methods you can implement.
Key takeaways
Interconnect and traceability hinge on how boards and data move together; pairing automatic PCB conveyors with SMEMA or, ideally, IPC‑HERMES‑9852 enables synchronized transfer and richer context for MES.
The fastest FPY wins usually come from damage prevention: edge support and rail alignment, soft start/stop with damped end stops, jam prevention, and ESD-safe materials/grounding consistent with ANSI/ESD S20.20.
For traceability, scan or otherwise assign a BoardId early, propagate it via Hermes, and bind routes/recipes using IPC‑2581 in MES; use IPC‑2591 (CFX) for plant-level events and KPIs.
Audit readiness requires documented validation: interconnect acceptance testing (SMEMA/Hermes), ESD verification and records, and electrical/safety function checks aligned with IEC 60204‑1 and ISO 13849.
Legacy constraints aren’t blockers. You can phase in Hermes with bridges or use barcode/RFID scan gates at conveyors to maintain traceability until full upgrades are feasible.
The standards landscape that drives conveyor requirements
The heart of automatic PCB conveyors compliance is the interplay between mechanical transfer and digital handshakes. Two interfaces dominate machine-to-machine handover: legacy SMEMA (electromechanical signals) and the modern IPC‑HERMES‑9852 protocol (Ethernet/XML). On the factory backbone, IPC‑2591 (CFX) carries richer, bidirectional messages, while IPC‑2581 supplies product and process intent from design to MES.
From SMEMA to Hermes: what changes and why it matters
SMEMA (IPC‑SMEMA‑9851) uses simple, opto-isolated signals to indicate “board present/ready/transfer complete.” It’s ubiquitous and stable, but it carries no board identity or context. Hermes (IPC‑HERMES‑9852) replaces the electrical handshake with TCP/IP and XML, adding board identifiers, dimensions, and structured state handling. According to the official specification v1.6 (2024), messages such as SendBoardInfo, BoardForecast, StartTransport, and TransportFinished create a data-rich handover, enabling downstream systems to auto-select programs and maintain continuous genealogy across the line. See the state charts and message definitions in the official spec for the exact fields and flows in v1.6.
IPC‑2581 and CFX: how product data and event streams complete traceability
IPC‑2581 (often called DPMX) is a neutral, machine-readable model that defines build intent—layers, materials, reference designators, process notes—so MES can bind a scanned or Hermes-propagated BoardId to the correct route and recipe. IPC‑2591 (CFX) complements Hermes by emitting line-wide events and KPIs and by enabling standardized data exchange among machines and software. IPC notes that CFX and Hermes are designed to work together: Hermes orchestrates the board handover and identity, while CFX carries broader factory telemetry and control messages.
Aspekt | SMEMA (IPC‑SMEMA‑9851) | IPC‑HERMES‑9852 v1.6 |
|---|---|---|
Physical layer | Dry-contact electrical I/O | TCP/IP over Ethernet with XML |
Core signals/messages | Ready/board present/transfer complete | StartTransport/StopTransport/TransportFinished + message state charts |
Board identity | Not supported | BoardId with metadata |
Board dimensions | Not supported | Width and Length fields available |
Error handling | Timeouts/sensor heuristics | Structured states including Incomplete |
Traceability | External scans only | Line-native handoff of BoardId to downstream and supervisory systems |
Sources: IPC‑HERMES‑9852 v1.6 (official specification PDF; message definitions and state charts) and IPC resources describing CFX/Hermes cooperation.
Engineering conveyors to prevent handling damage and lift FPY
Here’s the deal: most avoidable FPY loss tied to handling comes from mechanical stress, misalignment, surface abrasion, and collisions. Automatic PCB conveyors can either cause or cure these issues depending on configuration and maintenance.
Edge support, rail alignment, and width adjustment repeatability
Use edge conveyors with uniform rail heights and minimal, consistent overhang to avoid gouging and preserve planarity. Parallel rails reduce skew that leads to stops striking components or board edges.
Lock width-adjust settings and verify repeatability at changeover with gauge blocks or go/no‑go tools. Document setpoints for common panel widths to minimize human error.
Maintain transport height uniformity along the line to avoid step changes. Many SMT lines target a transport height around 900 ± 20 mm as a widely adopted convention; treat it as a practical starting point and confirm the actual spec for your line and each machine interface.
For step-by-step methods and fixtures, see the vendor‑neutral techniques outlined in a comprehensive width‑adjustment guide; these practices ensure repeatable, low-stress transfers.
Soft start/stop, damped stops, and jam prevention
Implement soft-start/soft-stop profiles via PLC/VFD control to limit impulsive loads that can propagate into solder joints and brittle components.
Fit damped stop units or cushioned hard-stops and verify impact forces during acceptance; target gentle deceleration so boards don’t “kiss” end stops hard.
Add anti‑jam sensors: upstream/downstream presence, backup detection, and time-based interlocks tied to SMEMA/Hermes handshakes. Simulate blocked/timeout scenarios to prevent pile‑ups and edge scuffing.
ESD-safe materials, grounding, and ionization aligned with S20.20
Qualify belts, rails, and frames per the site’s ANSI/ESD S20.20 program: measure resistance-to-ground, confirm protective bonding, and ensure reliable ground paths to moving sections (e.g., drag chains/brushes).
Where insulating guides or belts are unavoidable, deploy ionization per the ESD control plan.
Keep periodic verification logs (materials resistance, workstation audits, and training records) to satisfy program audits. Note that conveyor‑specific ESDA technical guidance is in development; until finalized, align to S20.20 program elements, your site ESD control plan, and local work instructions.
For a broader orientation on conveyor components and their behavior, consult an in-depth guide to PCB conveyors that covers variants, modules, and flow control approaches: complete guide to PCB conveyors.
Automatic PCB Conveyors Compliance in practice: interconnect & traceability patterns
You don’t need an overhaul to start. A pragmatic path layers identity assignment, protocol propagation, and MES binding.
Assigning BoardId at infeed (barcode/RFID/vision)
Establish BoardId as early as the loader or printer infeed via 1D/2D barcode, RFID, or vision OCR, and verify readability under normal conveyor speed/lighting.
Store the BoardId with time, station, and lane context in MES; if Hermes is available, prepare to propagate it downstream.
Propagating board context via Hermes; bridging legacy SMEMA
With IPC‑HERMES‑9852, use BoardForecast and SendBoardInfo to pass BoardId, Width, and Length to downstream stations; StartTransport/TransportFinished close the loop.
In mixed lines, use Hermes bridges/adaptors to convert between SMEMA and Hermes where upgrades aren’t yet possible. Validate the bridge with message traces and blocked/timeout tests so that data integrity survives edge conditions.
Binding recipes and routes using IPC‑2581 within MES
Import IPC‑2581 product data into MES so the system can map BoardId to the correct recipe and route. This enables automatic program selection at printers, placement, and inspection.
Use IPC‑2591 (CFX) in parallel for real‑time events, KPIs, and exception signaling; Hermes carries the handover identity while CFX broadens the factory‑level picture.
Validation and audit readiness without proprietary claims
Compliance is proven, not presumed. Build a compact acceptance and verification package you can hand to auditors.
What to hand an auditor (example evidence pack, field-only):
Interconnect (SMEMA/Hermes)
Line diagram showing interface type per station (SMEMA, Hermes, bridge)
SMEMA I/O timing log: signal names, expected polarity, debounce, timeout values, and pass/fail for normal + blocked + E‑stop scenarios
Hermes capture checklist: BoardId present, Width/Length consistent, StartTransport/TransportFinished sequence, and TransportState (Complete/Incomplete) recorded with timestamps and station IDs
Bridge verification notes (if used): firmware version, mapping assumptions, and reconnection behavior test results
Traceability binding (MES / IPC‑2581 / CFX)
BoardId assignment rule (where created, format, uniqueness window)
Data binding record fields: BoardId, product code, route, recipe/program name, revision, timestamp, lane/station
Exception handling rule: what happens when BoardId is missing/invalid or a station reports Incomplete
ESD (ANSI/ESD S20.20 program evidence)
Resistance-to-ground worksheet fields: location, material/belt ID, measured value, meter ID, calibration due date, limit used by your program, and disposition
Grounding/bonding inspection checklist: frame-to-PE continuity points, moving-section grounding method, and corrective actions
Safety (IEC 60204‑1 / ISO 13849)
Risk assessment summary for pinch points and guards
Safety function list with required PL and verification record (test method + result)
E‑stop test record: accessibility, latching/reset behavior, and restart prevention confirmation
Interconnect acceptance tests (SMEMA/Hermes)
SMEMA: Verify I/O signal logic (board available/ready), sensor alignment, and timing under normal, blocked, and emergency-stop conditions. Capture test logs.
Hermes: Record message traces for BoardForecast/SendBoardInfo/StartTransport/TransportFinished, including state transitions (Complete/Incomplete). Test loss/reconnect behavior per v1.6 state charts. Archive packet captures with timestamps and station IDs.
ESD verification and records per S20.20
Qualify belts/rails/frame resistance-to-ground, frame bonding to protective earth, and the use of ionization where insulators persist. Set re-verification intervals and retain calibration certificates for meters.
Keep training and audit records aligned with the site’s S20.20 program materials and local procedures.
Electrical safety and SRP/CS validation (IEC 60204‑1, ISO 13849)
Verify emergency stop devices for accessibility, latching, and reset behavior; confirm electrical realization meets IEC 60204‑1 principles.
Perform risk assessment for nip/pinch points; validate interlocked guards and any safe‑torque‑off functions. Complete PL calculations and verification per ISO 13849‑1/‑2 and retain the results with wiring diagrams and test logs.
A practical workflow (with a neutral S&M example)
Consider a phased deployment on a mixed‑vendor line:
At the infeed, a loader assigns BoardId via 2D barcode. The conveyor hands off boards using SMEMA today, but Hermes is planned downstream.
A mid‑line edge conveyor propagates identity using Hermes to a placement machine; BoardForecast and SendBoardInfo convey BoardId and dimensions, enabling automated recipe selection tied to MES.
Throughout, conveyors use soft‑stop parameters and cushioned end‑stops to limit impact, while anti‑jam sensors prevent collisions.
In an implementation like this, a standard automatic PCB loader or conveyor from a vendor supporting SMEMA and common SMT transport conventions can serve as the starting point. For example, the brand token “S&M” provides product pages that outline SMEMA compatibility and transport geometry; you can review a representative page here for context: S&M. Use it as a neutral reference while specifying your own protocol and validation requirements.
To manage flow distribution and exceptions without manual intervention, plan buffer and shuttle points; for a conceptual illustration of NG/OK sorting and temporary storage in a traceability‑aware flow, see a neutral overview of an NG/OK dual buffer stocker that explains how buffers fit into balanced lines: NG/OK dual buffer stocker.
Operations and maintenance playbook
Changeovers: Standardize width‑adjust setpoints by product family; verify with gauges and record results. Train technicians to perform quick, documented checks. For detailed steps, see this conveyor width adjustment guide.
Preventive maintenance: Inspect belts for wear and glazing, verify bearing play, clean sensors, and re‑align photoeyes. Revalidate handshake I/O (SMEMA) or capture a brief Hermes trace monthly.
ESD program: Recheck resistance‑to‑ground on a defined cadence; inspect bonding straps and ionizer performance; document corrective actions.
Incident drills: Simulate jams and blocked handshakes quarterly; verify that sensors, interlocks, and stop logic prevent collisions and that logs clearly record the event.
Continuous improvement: Track FPY categories tied to handling (edge damage, scuffs, collisions) before and after conveyor adjustments; even modeled comparisons guide which parameters to prioritize next.
References and further reading
According to the official IPC‑HERMES‑9852 Version 1.6 specification (2024), messages like SendBoardInfo and TransportFinished define the data-rich handover and state handling used in modern SMT lines.
IPC describes CFX as the digital factory backbone and explains how CFX and Hermes work together to integrate line-level handover identity with factory-level messaging.
For product/route binding, IPC provides IPC‑2581 overview resources that clarify how design data feeds MES recipe and routing control.
ESD Association training materials outline S20.20 auditing and training fundamentals used to structure conveyor-level ESD controls and records.
Die IEC 60204‑1 official page defines scope for the electrical equipment of machinery; consult purchased clauses and reputable device manuals for emergency-stop realization and protective bonding practices.
Internal resources (vendor-neutral context):
Overview of conveyor modules and flow control: complete guide to PCB conveyors
Width-adjustment SOP concepts: conveyor width adjustment guide
Buffering for line balance and exception handling: NG/OK dual buffer stocker