4.3 What to Encode & How

Encoding is where your traceability plan turns into data that systems can trust. The choicecodes you print are the resilient anchors of whata unit's history. The key is to include—serialencode numbers, BOM revisions, lot/date codes, or line details—defines how precisely issues can be isolated later. Equally important is howonly the informationessential isdata carried:and 1Dpair barcodesthe excelcode atwith long-rangethe scansright symbology and placement for maximum readability on railsthe andfactory boxes, while compact 2D codes with error correction keep unit IDs readable through reflow, coating, and handling. Standards like GS1/ISO make codes interoperable across suppliers and customers, while human-readable text ensures audits and debugging don’t stall. Together, these decisions transform a printed mark into a reliable pointer to a unit’s full genealogy.floor.

4.3.1 The dataData dictionaryDictionary: (whatWhat everyMust codeBe should carry)Encoded

PickThe content of your code (the data dictionary) should be the smallest set of fields thatrequired meetsto meet your chosen traceability level (from Chapter 4.1). Every unnecessary character adds size and customer/contract needs, then lock it in your Labeling & Traceability spec in the Golden Data Pack.complexity.

Core Fields (Mandatory for Traceability)

These fields (mostare builds)non-negotiable for proving a unit's identity and configuration:

• SN (serialSerial number)Number): —Unique uniqueidentifier perfor unitthe (orindividual panelunit. IDIf ifpanel-level lot-level).tracking is used, this is the Panel ID.
• BOM Rev / Config IDID: —Crucial exposesfor whichaudits. bill-of-materialsThis revisionimmediately tells the unitscanner matches. Many customers require this onand the visibleMES label.system which Bill-of-Materials version was followed, allowing isolation of parts failures to a specific design release.
• Work orderOrder / Lot / Date codeCode: —Identifies letsthe youbatch and time frame of production, essential for quick quarantine preciselyif whena needed.
• Lineprocess / Station / Shiftfault (compressed)like —a helpsreflow triageoven escapesissue) fast.is found.
  

Optional fieldsFields (addEncode onlyOnly if they earn their keep)

Necessary)

• Variant / Feature flagsFlags: (Use only if one PCB assembly serves multiple SKUs)final product SKUs (e.g., a flag for 'With Wifi' vs. 'Without Wifi').
• RegulatoryRegulatory/Customer IDs: Required if contracts dictate encoding specific customer part numbers or customerregulatory IDsmarks (like specific MAC addresses).

Human-Readable Lines

Always pair the machine-readable code (1D or 2D) with a clear human-readable string (ifusually contractsthe dictate)SN and the BOM Rev).

Checksum orThis internalis recordessential keyfor usedmanual todebug, joinrepair, and auditors when a scanner fails. Ensure the human text format is consistent with MES/ERP.what your MES expects.

4.3.2 Symbology & Durability: 1D vsvs. 2D

The type of barcode you choose dictates how much data you can store in a small space and, crucially, how well the code survives damage (anddurability).

which

Symbology standardsType	Key toFeature	Ideal speak)Placement	Durability/Damage Resistance
1D barcodesBarcode (Code 128, etc.)	Long, aresingle greatstring; forrequires more space length-wise.	Carton labels, long,panel scannablerails, stringspackaging boxes (where space is wide).	Low. andIf one line is scratched, the entire code fails.line-of-travel readers on rails and boxes.
2D codesCode (DataMatrix, QR)	Compact; pack morehigh data into less space and survive damagedensity thanks to built-in errora correctionsmall square.	PCB Unit ID. Use them on the PCB when(where space is tight.tight), small component labels.	High. Built-in Error Correction allows the code to be read even if 20-30% is damaged by splatter, reflow, or etching.

Standards and Verification

• Standards: Choose a GS1/ISO standard flavor(like whenGS1 customersDataMatrix) wantif your product is consumer-facing or needs global consistency. PutThis ensures the choicecodes (1Dare vsinteroperable 2D,across symbology,different field order) in your label spec so scannerssupplier and MEScustomer parsesystems.
• Quiet it the same way.

  Rules of thumb

  • Prefer DataMatrix/QRZone: onEvery thecode PCB for compact, durable unit IDs; keep Code 128 for cartons/pack-out where space is abundant.
  • Keeprequires a quiet zone—a clear, uniform margin of empty space around everythe codesymbol. andFailing sizeto modulesmaintain forthis yourspace cameras;is verifythe readabilitymost incommon yourcause scanningof stepscanner failure.
  • Error Correction: For the PCB unit ID (4.5).
    

  4.3.3 Human-readable lines (for eyes and audits)

  Always pair machine codes withusually a human-readable2D stringcode), (SN and minimal context like WO/Rev). It saves time in debug and still passes audits when a scanner fails. Put formatting examples inensure the spec and keep them consistent with what MES expects.

  4.3.4 Error correction & verification (don’t skip this)

  • 2D codes include error correction by design; pick a level thatis tolerateshigh enough to tolerate your real real-world environment (soldercleaning splatter,solvents, cleaning,handling coatabrasion). glare).
  • Add a verify step step to your route: print/laserPrint/Laser →$\rightarrow$ scanScan to Grade – Accept/Block. WIP must be blocked if the code fails to grade → apply/accept. Failures correctly.block WIP and open a reprint flow; successes write the record via API so there’s no “shadow spreadsheet.” (Details in 4.5.)
    

  4.3.53 Deployment: Placement and Specification

  The decision is not just about the data string; it's about placing the code correctly and documenting every detail.

  
  

  A. Where eachEach codeCode livesLives

  (and

  Code why)Type	Placement Location	Purpose
  Panel railID	Panel Rail: big(Outer edge)	Used for 1D or 2Dupstream fortracking upstream/downstream(solder stationpaste, scans.stencil) and line-of-travel scanners.
  Unit ID	PCB (unit)Consistent Corner)	:Used compactfor 2Ddownstream tracking (AOI, Test, Rework) and customer traceability. Must be in a consistent, easily accessible corner.
  Pack-Out ID	Carton/Box	Customer-facing code, often mirroring the core fields (SN + Rev + WO/Date) in a consistent corner with high contrast (from 4.2). Box/pack-out: customer-facing 1D/2D per contract; mirror core fieldsRev) and includeincluding shipping IDs.

  Tie

  B. allThe ofTraceability them back to the same record in MES/ERP.
  

4.3.6 Put it in writing (spec template)

Specification

YourThe Labeling & Traceability specSpecification shouldis state:a mandatory part of the Golden Data Pack. It removes all ambiguity and serves as the single reference for every labeling station and scanner on the floor.

This spec must detail:

• SymbologiesSymbologies: allowedList every permitted symbology (1D/2D;e.g., GS1/ISO"Primary whereunit required)ID andis dataDataMatrix fieldECC order/lengths200").
• Human-readableField formatOrder: Define the precise order and fonts.length of the encoded fields (e.g., "SN [12 chars], followed by Rev [3 chars]").
• Placement Map: Provide a drawing showing the exact placement coordinates, size (rail vs PCB vs box)min/max), and minimum clearances/quiet zones.zones for all codes.
• VerificationAPI stepMapping: (scannerState gradehow threshold,the reprintscanned flow)data andfields APImap mappingdirectly to your MES/ERP objects.objects (e.g., "The first 12 characters map to the MES object 'Unit_SN'").
  

---

Conclusion: Encoding only the essential fields and pairing machine-readable codes with human-readable lines keeps genealogy precise without adding complexity. When tied into MES/ERP and verified at each step, these marks become resilient anchors for both manufacturing control and customer trust.