Process Audit and Walkthrough in Electronics Assembly

An audit that only checks whether documents exist tells you very little. An audit that watches the process run and compares it with what the documents say produces findings, and the findings are where the value is.

What to Observe

The audit should follow the product rather than the department, from the incoming material to the packed board. At each station the question is what the operator does and what the instruction says.

The sequence matters, because a defect at one station often originates at the one before. Our yield analysis notes describe the same chain.

Instruction Against Practice

Where the two differ, the finding should be recorded as a difference rather than as a fault. A step that nobody performs is usually a step that does not need to be performed or cannot be.

The instruction should be corrected when it is wrong. Our work instruction notes describe the revision control.

Records and Their Use

A record that is filled in after the shift is not a record. The audit should check the timing as well as the content, and a record that is always perfect deserves a closer look.

The records that matter are the ones someone would read. Our traceability notes describe which those are.

Measuring Against the Specification

Where a parameter is specified, the audit should measure it rather than read the display. A profile, a print volume and a torque are all worth measuring independently at least once.

Our measurement notes describe the technique.

Writing the Finding

A finding states what was observed, what it was compared with and what the consequence is. A finding that states only a deviation leaves the reader to guess whether it matters.

Our quality notes describe the acceptance that gives the comparison its basis.

Closing the Finding

The closure should address the cause rather than the instance. Re training an operator when the instruction was wrong produces the same finding at the next audit.

The effectiveness check is what distinguishes a closure from a promise. Our floor control notes describe where the change is held.

Verification

The verification is an audit that follows the product, a finding written against a specification rather than an opinion, a closure that addresses the cause, and an effectiveness check at the next audit.

Our quality notes describe how the records are kept.

Additional Considerations for This Build

Practical attention to process audit pays for itself here, because it decides whether the finished board behaves as the drawing intended. Where the requirement is not stated on the fabrication drawing or in the assembly notes, the shop has to assume a default, and that default is rarely the value the design was simulated with. Stating process audit explicitly, together with the tolerance that applies, removes the assumption and keeps the result predictable from batch to batch.

Deliberate attention to walkthrough pays for itself here, because it decides whether the finished board behaves as the drawing intended. Where the requirement is not stated on the fabrication drawing or in the assembly notes, the shop has to assume a default, and that default is rarely the value the design was simulated with. Stating walkthrough explicitly, together with the tolerance that applies, removes the assumption and keeps the result predictable from batch to batch.

Careful attention to nonconformance pays for itself here, because it decides whether the finished board behaves as the drawing intended. Where the requirement is not stated on the fabrication drawing or in the assembly notes, the shop has to assume a default, and that default is rarely the value the design was simulated with. Stating nonconformance explicitly, together with the tolerance that applies, removes the assumption and keeps the result predictable from batch to batch.

Consistent attention to corrective action pays for itself here, because it decides whether the finished board behaves as the drawing intended. Where the requirement is not stated on the fabrication drawing or in the assembly notes, the shop has to assume a default, and that default is rarely the value the design was simulated with. Stating corrective action explicitly, together with the tolerance that applies, removes the assumption and keeps the result predictable from batch to batch.

Methodical attention to observation pays for itself here, because it decides whether the finished board behaves as the drawing intended. Where the requirement is not stated on the fabrication drawing or in the assembly notes, the shop has to assume a default, and that default is rarely the value the design was simulated with. Stating observation explicitly, together with the tolerance that applies, removes the assumption and keeps the result predictable from batch to batch.

Process Control and Verification

On a design of this kind, observation is the item that decides how the rest of the board is arranged. 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.

Reviewing the design before the data is released is cheaper than correcting it after the panel is in the tank, because every step downstream inherits the decision made at the front end. Documenting the assumption is part of the design work, and a short note on the drawing prevents a question that would otherwise arrive a day later and cost a day of schedule.

The process window is set by the narrowest step in the flow, so an improvement anywhere else shows up as margin rather than as yield until that step is addressed. A short note on the drawing about handling, storage or packaging is often worth more than an extra decimal place on a tolerance.

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.

FAQ

Should the audit be announced? An announced audit checks readiness and an unannounced one checks practice. Both have a place and they answer different questions.

How many findings are normal? A first audit of a stable process usually finds several instruction differences and a few practice ones. None at all usually means the audit was too shallow.

What does gopcb provide in an audit? We provide an audit that follows the product from material to pack, findings written against the specification with the consequence stated, a closure that addresses the cause rather than the instance, and an effectiveness check at the following audit.