When planning AOI inspection data integration with MES, settle one question before choosing a protocol: which board, side, inspection and human decision does each record describe? Sending only AOI OK/NG does not establish a trustworthy history if a panel contains several units, a defect is reviewed, or a board is repaired and retested. This guide gives production engineering, QA and IT teams in Thai electronics plants a practical route from requirements and RFP to FAT and SAT.
Define the outcome beyond automated collection
“Collect AOI data automatically” is too weak as an acceptance criterion. A CSV export could satisfy that wording while leaving QA unable to explain a shipped board. Write the outcome as a query: for a selected serial number, can the plant retrieve its material and process context, AOI recipe revision, detection, image evidence, reviewer, repair, retest and final release decision? Decide whether customer audit, containment, yield analysis or prevention at the next process is the first use case. The required identity and evidence depth differ.
Separate the searchable keys from bulky images and agree how long each must remain available. Storing every image indefinitely may create an avoidable storage and access problem; storing no image may leave a quality dispute unresolved. This article concerns the transfer of AOI and human decisions into product history. For model selection and defect recognition itself, see our AI solder-joint inspection article.
Resolve panel, board and unit identity
An AOI machine may transport and inspect a panel containing multiple individual boards. Check whether a label called “board ID” means the whole panel, one unit, or a temporary work-order identifier. MES history must connect to the unit that will be shipped or investigated. A single panel-level OK/NG is insufficient when only one position is defective.
Create an identity map with panel ID, unit ID or position, side, product number, work order, station, and inspection timestamp. If unit serials are assigned after depaneling, specify how panel ID plus position maps to the later serial. Define what happens to missing positions, duplicate scans and bad-marked units. “Skipped” means not inspected; it is not a synonym for “passed.” At the AOI entrance, decide whether a successful barcode read is required before inspection. If a scan fails, the process may stop, quarantine the panel, or issue a controlled temporary ID. An unapproved manual match after the fact is hard to defend in an audit.
Keep machine detection and product disposition distinct
Depending on equipment and options, an AOI event may expose a provisional result, defect location, component reference, inspection item, image reference and recipe. Request actual sample payloads, field definitions, export files, and missing-field behavior from the machine supplier. The claim “CFX compatible” alone does not establish which defect detail is available.
MES should preserve at least two decision layers: the machine’s initial finding and the final product disposition after review. If a reviewer accepts a false call, keep the original NG event and append the review decision and reason. If a board is repaired, link the original defect, work performed and retest. Corrections should preserve who changed what, when and why. Draw separate state paths for “uninspected → AOI pass → next process,” “AOI NG → review → false call accepted,” and “confirmed defect → rework → retest → pass or hold.” During a communication outage the state is unresolved, not implicitly passed.
Write a minimum data contract for AOI result collection
A data contract states field meaning, type, mandatory condition, uniqueness and retry behavior. AOI, MES and plant owners should sign the same table. Start with these areas and mark unavailable fields explicitly rather than assuming all devices support them.
| Area | Data to check | Acceptance question |
|---|---|---|
| Workpiece | Panel ID, unit/position, side, product | Can mixed product IDs be rejected? |
| Execution | Machine, line, timestamps, event key | Does a retransmission avoid double counting? |
| Recipe | Program name and revision | Can records be filtered across revision changes? |
| Detection | Machine result, defect type, location, skip | Is unit-level status preserved? |
| Evidence | Image ID or URL, retention rule | Can missing or expired evidence be detected? |
| Human action | Reviewer, reason, rework, retest, final decision | Is the complete sequence retrievable? |
If the machine supplies no stable event ID, define an ingestion key based on station, workpiece, timestamp and inspection cycle. Test same-second retests and timestamp rounding. Deduplicating by board ID alone loses genuine retests; inserting every retry inflates defect counts. Demonstrate both cases independently in FAT.
Make program revision a quality gate
An AOI program controls inspection regions, thresholds and other conditions. A PASS recorded under the wrong program does not mean the same thing as a PASS under the approved program. Define allowed combinations of product, side, work order, program and revision. If the machine does not expose a simple revision string, retain its approved change identifier or timestamp according to the vendor’s specification. Link local adjustments to approval, effective time and affected lots.
The IPC-CFX version history describes recipe activation and local recipe change messages. That is a useful starting point, but an individual AOI still has to be checked for the topics and fields it implements. A published standard and a specific product’s implementation are separate evidence.
Design evidence retrieval before selecting image storage
Images may stay on the AOI, a file server or object storage while MES retains references. Compare capacity, backup, access and restoration for each choice. Check whether the machine automatically deletes images after a period and whether selected defect evidence must be copied elsewhere. Retention depends on customer contracts, quality policy, product life and information governance; no universal number should be assumed.
Test whether a retrieved image can be tied to the exact unit, side, defect position, inspection time and recipe. Never overwrite a pre-rework image with the post-rework image. Make missing images visible and distinguish a broken link from a permission failure. The public IPC-CFX version history mentions image transfer and out-of-band references, but those mechanisms do not define the plant’s retention or access policy by themselves.
Treat review and rework as a controlled workflow
The review terminal is a decision point, not merely an image viewer. Define reviewer authorization, reason codes, conditions for a second approval, and who may release a board. Keep “false call accepted,” “real defect repaired,” “scrap” and “hold” as different actions. Otherwise yield, repair and escape analysis collapse into one misleading OK count.
Link a rework instruction, material used, operator, time and retest to the original defect. If a controlled exception permits movement without retest, record the authorization and reason. In multilingual Thai operations, map defect names and reason codes consistently across Thai, English and Japanese interfaces. For offline operation, decide whether actions are blocked or temporarily recorded, who owns reconciliation, and how conflicts between terminals are resolved. A communications failure must not silently turn a hold into a pass.
Where IPC-CFX and Hermes fit
IPC-2591 Connected Factory Exchange is an open industry standard for information exchange between assembly processes and host systems. Its public version history includes inspection, recipe, repair and related topics. Ask a CFX-capable supplier for the supported version, published and subscribed topics, sample messages, retry behavior and security setup. IPC also publishes a self-validation and qualification system. Check whether the evidence covers the particular defect and review fields in your contract; qualification does not guarantee every desired use case.
Hermes addresses board information exchange between neighboring SMT machines. It can help carry a panel’s identity along the line, but it does not automatically solve detailed AOI defects, human disposition or MES retention. The plant must join transport identity to the inspection event and the later unit identity. If an existing line uses Hermes, verify the exact unit and position fields in that implementation. A Viscom brochure illustrates possible auxiliary AOI software functions; confirm the installed machine model, license, version and interface before adding those functions to an RFP assumption.
Survey the installed line before specifying integration
For a brownfield line, diagram the AOI, review terminal, barcode reader, line-control PC, MES and image store. Include owners, software versions, licenses, network boundaries and clock synchronization. Verify that advertised communication features are enabled on the installed version. Assign one party to collect the first diagnostic log for each failure point.
Capture real sample cases: pass, obvious defect, false call, one bad unit within a panel, bad mark, scan failure, repeat inspection and repair followed by retest. Vendor demo payloads may hide local product coding or image-path behavior. Protect customer drawings and product data when sharing samples. Examine failure modes: Can the AOI continue during MES downtime? Where are events buffered, for how long, and in what order are they replayed? What happens if only the image store fails? Those are joint equipment and quality-policy decisions.
Give vendors contractible RFP deliverables
Attach the identity map, event table, state diagram, evidence policy, exception rules and acceptance scenarios. Require each supplier to mark a requirement as standard, configurable, custom development or unsupported. For custom work, ask who maintains it after an AOI or MES upgrade. Break the estimate into machine licenses, gateway, MES data model and screens, review stations, image storage, networking, migration, local testing, training and support. A generic fixed budget for “AOI connection” hides these differences.
Define release and physical containment
If one unit on a panel is NG, does the conveyor stop the panel, does depaneling segregate the unit, or does a later station use the bad mark? Walk the actual route with QA, production engineering and line leadership. A board held in MES but placed in a good-product rack is not contained. Specify release overrides, authorization and recovery after mistakes. The factory, rather than the machine supplier alone, owns the disposition policy.
Assign responsibility at every interface
“Machine outputs data” and “MES accepts data” leave open who owns test environments, certificates, time synchronization, character encoding, image shares, monitoring and logs. Put a primary owner and acceptor on every connection. Maintain a versioned mapping table for source defect codes, MES codes, meaning and unknown-value handling. Never map an unknown defect silently to PASS. Show where each transformation runs so a future machine upgrade has a predictable impact.
Test more than connectivity in FAT and SAT
Use FAT to validate the contract and state machine in the supplier environment. Use SAT to repeat with actual line equipment, barcodes, product codes, operators and network. Test duplicate transmission, actual retest, one defective unit in a panel, wrong recipe, missing image, MES outage and reconnection. Retain the AOI source log, MES receipt log, resulting screen, image reference, operator and test time for each case. “Message received” is weaker than “this unit’s sequence is searchable and the next-process gate behaves correctly.”
Test time and order separately
AOI, reviewer and MES clocks may use different time zones. Define whether event timestamps carry offsets, how the server normalizes them, and how local users see them. Test across midnight and with delayed messages. An identical retransmission must not create a second inspection, while a physical second inspection must remain a separate cycle. If the image arrives later than its event, the link should be completed without rewriting history.
Test searches based on QA questions
Ask: Who released this shipped serial? Which products used a given AOI program revision? Can QA open evidence for a specific defect? Which unit on this panel was repaired? Define search keys, output columns, source-log links and export permissions before testing. Use representative data volumes and retention periods. If older images move to archive, verify that MES can still find the correct location. Keep test records distinct from production quality history.
Move the workflow into a Thai plant
Design the review screen, hold rack, repair record and retest route with the local team. Validate Thai reason-code wording against what operators actually say. Set role delegation for night shifts. During cutover, reconcile old records and new MES entries for a controlled period and classify mismatches: scan errors, AOI event timing, missed reviews or image gaps. Separate configuration fixes from changes to work instructions. QA and production leaders should approve the cutover after search, unresolved-unit handling, outage recovery and training have been demonstrated against plant-specific criteria.
To link AOI results back to material and placement history, see our SMT mounter component traceability guide. Shared unit IDs can narrow an investigation, although the available component-to-reel detail still depends on the placement machine data.
Frequently asked questions about AOI–MES integration
Does automatic AOI collection let us retire paper inspection records?
Not automatically. Inventory the decisions and details now captured on paper, including review, rework and concessions. Verify authorization, audit history, search, backup and outage procedure in electronic acceptance tests. Customer record requirements still apply.
Is panel-level board history enough?
If shipped units are individually identified, usually not. Keep panel ID and position even before a unit has a serial, then define the later mapping. Select the level of detail from the product structure and customer traceability requirement.
Should MES erase the original AOI NG after repair?
Keep the original event and append review, work, retest and final disposition. Even a false call remains part of the inspection history. The main screen can show the latest status while preserving access to the underlying sequence.
Does IPC-CFX remove all custom integration work?
Not necessarily. Verify supported topics, mandatory fields, images and the MES state model on the actual products. Request message samples and qualification scope, then run the agreed FAT scenarios.
What belongs in the first rollout?
Choose one line and representative product, and complete identity, AOI event, review, final disposition and search end to end. Phase other images and upstream/downstream links by quality need. Do not start with an identity model that can never map the panel to its shipped units.
Conclusion
AOI–MES integration succeeds when a plant can explain one board: its identity, program revision, machine finding, human review, repair, image, retest and release. Put those facts into the data contract and state diagram, then demonstrate normal and failure cases at FAT and SAT. TOMAS TECH can help assess an installed AOI interface, define identity and MES data, and plan local acceptance in Thailand. If you are still defining the scope, share your line configuration and the history questions you need answered through our contact page.
