Assembly Work Instruction Content and Control

A work instruction is the document that turns a process into what actually happens on the line. It is written for the operator rather than for the auditor, and the test of a good one is whether a trained person who has not run that product can produce an acceptable board from it.

What Belongs in the Instruction

The instruction carries the operations in sequence, the settings the operator has to enter or verify, the acceptance criteria for what they see, and the response when something is outside the criteria. It does not carry background, theory or a description of the equipment.

Where the instruction includes the acceptance criterion, the operator can make a decision at the station. Where it does not, the decision moves to an engineer, and the line waits. Our board quality notes describe the standard that the criteria come from.

Reading Versus Remembering

An instruction that asks the operator to remember a value from another document does not work. The value belongs where it is used, even if that means it appears twice, and the two copies have to be tied to one source so that a change reaches both.

The practical solution is a document that contains the values and a reference to the master that controls them. A change process that updates one and not the other produces a line that runs to a superseded figure. Our first pass yield notes describe how a drift from that appears in the data.

Revision Control and Its Practical Effect

A revision is only useful if the line is running the current one. The control is a document number and revision that is read at the station, and in a manufacturing execution system the reading is enforced rather than encouraged.

The most common failure is a paper copy that was printed before the change. Removing uncontrolled copies is a discipline rather than a system feature, and it is the reason a shop that prints on demand has fewer of these problems than one that prints in batches.

The operator reads the instruction at the station with limited time, so the order matters more than the prose. An instruction that describes the equipment before the action slows the reading and increases the chance that a step is skipped.

Photographs of the actual board at the actual station are worth more than a drawing, because the operator is comparing what they see with the picture. Our placement capability notes describe how the acceptance on a placement step is quantified.

Acceptance Criteria and the Response

Every criterion needs a response. An instruction that says a defect is not acceptable and does not say what to do next leaves the operator to invent an action, and the actions differ between shifts.

The response is usually one of four: continue, adjust and re-check, quarantine the board, or stop and call for support. Naming them makes the decision repeatable and makes the escalation path visible.

Training and Qualification

An instruction assumes a trained operator, and the training has to cover the standard rather than the product. A person who has been trained on the workmanship standard can move to a new product with the instruction alone.

The qualification record is what makes that assumption auditable. It should name the standard, the date and the person who assessed it rather than a general attendance. Our floor zoning notes describe how the stations are organised around that.

Feedback From the Line

The people who run the instruction find its errors, and the route for reporting them has to be short. A correction that takes a week reaches the line after the problem has been worked around informally.

A simple change request with the page reference, the problem and the proposed wording is enough. The value is in the speed rather than in the format.

Process Control and Verification

On a design of this kind, acceptance criteria is the item that decides how the rest of the board is arranged. Where a value sits close to a process limit, the drawing should say so, since the shop can then open the process window rather than working to a nominal figure that carries no tolerance. A stack-up that is drawn rather than described removes most of the ambiguity from a quotation, and it lets the fabricator price the board against the dielectric and copper weights that will actually be used.

Where the requirement is not written down, the shop supplies its own default, and the default is chosen for the process rather than for the design. The measurements that matter are the repeatable ones: conductor width and spacing, annular ring, finished hole size, plating thickness and surface finish are all verifiable on a coupon that travels with the panel.

Running a first article through the same checks as the production panel confirms that the two agree, and that comparison is the cheapest form of process control available at prototype stage. Keeping a sample from the panel turns a dispute into a measurement, because the same coupon can be re-examined by both parties without rebuilding the batch.

Process Control and Verification

On a design of this kind, acceptance criteria is the item that decides how the rest of the board is arranged. Where a value sits close to a process limit, the drawing should say so, since the shop can then open the process window rather than working to a nominal figure that carries no tolerance. A stack-up that is drawn rather than described removes most of the ambiguity from a quotation, and it lets the fabricator price the board against the dielectric and copper weights that will actually be used.

Where the requirement is not written down, the shop supplies its own default, and the default is chosen for the process rather than for the design.

Process Control and Verification

On a design of this kind, acceptance criteria is the item that decides how the rest of the board is arranged. Where a value sits close to a process limit, the drawing should say so, since the shop can then open the process window rather than working to a nominal figure that carries no tolerance. A stack-up that is drawn rather than described removes most of the ambiguity from a quotation, and it lets the fabricator price the board against the dielectric and copper weights that will actually be used.

Audit and Use

An auditor reads the instruction, watches the operation and compares the two. Where they differ, the finding is a document control issue and the cause is usually that the instruction was written from the process rather than from the work.

Writing from the work means observing the operation and recording what is done, then removing what is unnecessary. That takes longer to produce and it lasts much longer in use.

How long should an instruction be? As short as it can be while still containing the settings, the criteria and the response. Length is not evidence of thoroughness.

Can a video replace a written instruction? It can supplement one, and it is harder to search at the station when a single value is needed.

What does gopcb provide for work instructions? We provide instructions written from the operation with settings and criteria at the step, images of the actual product, a defined response to every criterion, revision control enforced at the station, and a short route for corrections from the line.