Fabrication Traveler: Route Cards and Process Sign-Off

A fabrication traveler is the document that moves with a lot of panels through the shop, and it names every operation in sequence with a place to record the result. It is called a route card, a job card or a process sheet depending on the shop, but its job is the same everywhere. The document is only as good as the discipline behind it, and a lot that is not signed at the station has no history worth reading.

It is also the only single record that shows what happened to a specific lot from material release to final inspection. When a question is asked about a delivered board, the traveler is the document that answers it. Every stage in a PCB shop leaves evidence on the panel, and the traveler is what turns that evidence into a record.

What a Fabrication Traveler Carries

The traveler carries the part number, the revision, the stack-up, the material and the quantity, and then a line for every operation the lot will see. Each line has a space for the operator, the date and an accept or reject decision. The traveler should also name the material lot, so that a laminate or a prepreg batch can be connected to the panels it went into.

It also carries the customer requirements that are specific to the order, such as a finish, a tolerance or a special inspection. Those notes are what stop a standard process from being run over a non-standard requirement. Special notes should be flagged in a way that cannot be missed, because an unusual requirement buried in a paragraph will be skipped.

Route Card Sequence

The sequence on the card follows the physical route: inner layer imaging, lamination, drilling, plating, outer layer imaging, mask, finish and routing. The order is not arbitrary, because each operation depends on the state the previous one left the panel in. A route that skips a step will usually be discovered at final inspection, when the panel can no longer be corrected economically.

A lot that has missed a step will often still look correct at the next station, which is why the card is signed rather than assumed. Those operations are described across the fabrication guides, including layer registration control work. The sequence should be reviewed whenever a new product is introduced, because a route copied from an old part can hide a missing operation.

Operation Sign-Off

Sign-off is a short entry that records who ran the operation, when it ran and what the measured result was. A signature alone is weak evidence, while a signature beside a measured value is a record that can be compared with the specification. An entry that says only pass or fail is less useful than one that carries the number, because the trend is lost.

Entries should be made at the station rather than at the end of the shift, because a card completed from memory records assumptions rather than measurements. Where a measurement is recorded it should be recorded in the units the specification uses, so that no conversion is needed later.

Deviations and Rework Routing

Deviations happen, and the traveler is where they should be visible. An out-of-specification reading that was accepted, or a rework that was carried out, belongs on the card with the reason and the authority for the decision. A deviation should name the person who authorised it, because accepting a non-conformance is a decision rather than an accident.

Rework also changes the route, because a panel that goes back through drilling has a different history from one that did not. That extra pass should be recorded, since it changes the thermal and chemical exposure of the lot. Rework should be followed by the same inspection the original operation required, and the card should show that it was done.

Traveler and the Specification

The engineering drawing and the fabrication notes set what is required, while the traveler records what was done. The two are linked by the revision number, so a traveler quoting the wrong revision is worse than no traveler at all. A revision change in the middle of a lot should be recorded against the panels that were built to each revision.

Where the drawing and the process sheet disagree, the drawing governs unless a documented deviation says otherwise. That rule should be written into the traveler itself, so the operator does not have to interpret it. Requirements are set out in fabrication specifications work. Process sheets stored separately from the traveler should be referenced by number, so that the correct version can be found.

Traveler in the Shop and in the Record

On the shop floor a paper traveler travels in a pocket with the lot and is signed at each station. In a digital system the same entries are made at a terminal, and the lot is scanned rather than signed. Scanning a lot at each station gives the same information as a signature and takes less time, provided the scans are made.

The digital version is easier to search, while the paper version is harder to lose in the middle of a process. Many shops run both for a period, and the entries have to agree while they do. Records kept in a single system are searchable by material lot, which is what makes a recall or a containment exercise possible.

Traceability Through the Lot

Traceability means being able to connect a delivered board to the material, the process and the people involved. The traveler is the spine of that connection, and the incoming inspection record is the other end of it. Traceability also covers the operator and the equipment, because a fault that follows a person or a machine is easier to find.

Where a lot is split, or where two lots are merged, the traveler has to show the relationship, because a lot code that cannot be resolved into actual material defeats the purpose. Incoming records are described in incoming inspection notes. A traveler should not be closed until every operation on it has a result, even when the result is that the operation was not needed.

Records and Verification

The traveler should be reviewed before the lot is released, and any gap in the sequence resolved rather than signed over. Completed travelers are kept for the period the customer or the standard requires. Reviewing the traveler before release is the last chance to catch a missing step, and it is cheaper than a returned shipment.

Acceptance of the finished board follows the criteria in the published IPC documents. A traveler with a missing sign-off is an open question about the board, even when the board itself measures correctly. Keeping the traveler with the lot until release is the simplest control, because a document that travels with the panels cannot be filled in from memory.

FAQ

Why does a lot need a traveler if the process is fixed? Because it records what was actually done to that lot, including the deviations, which is what a delivered board has to be able to answer for.

Is a signature enough for sign-off? No. A sign-off that carries a measured value, the operator and the date is worth far more than a name on its own.

Where should rework be recorded? On the traveler, with the reason and the authority, because a panel that has been through an extra pass has a different history.