PCB Depanelising Tooling Selection

Depanelising is the step where the finished boards are separated from the panel, and it is also the step that damages more assemblies than any other mechanical operation. The tooling choice determines the edge quality, the stress on the components and the cycle time.

The decision follows from the panel design, since the break method has to match the tab or the score that the fabrication data specified. Choosing the tool after the panel is designed often means living with a compromise.

Manual Snapping

Snapping by hand with a simple fixture is the cheapest method and the one with the most variation. The result depends on the operator, on the fixture and on the panel, and the edge quality varies between shifts.

It is acceptable where the edge is not visible and the components are far from the break line. Where either condition fails, another method is needed.

Routing Machines

A router cuts the tabs with a rotating bit, which gives a clean edge and a repeatable result. The bit follows a program derived from the panel data, and the cut depth and speed are controlled.

The method produces dust and static, both of which affect a sensitive assembly, so extraction and ionisation are part of the installation rather than accessories.

Laser Depanelling

A laser cuts without mechanical contact, which removes the stress entirely and allows a complex outline. The cut edge is clean and the method suits a brittle component or a flexible assembly.

The cycle time is longer and the capital cost is higher, so the method is used where the value of the assembly justifies it.

V-Cut Breaking

A V-cut is broken with a bar or a roller, which applies a controlled bending moment along the score. The result is a straight edge with a bevel, and the method is fast.

The limitation is the geometry, since the score must be straight and the components must be clear of the line. Both constraints are described with the panel design in panelisation and tab routing.

Stress and Component Damage

Every depanelising method applies force to the board, and the force travels to the nearest components. A ceramic part near a break line is the component most likely to be damaged.

Supporting the board directly under the break line is the most effective measure, and it is cheaper than changing the method. The damage mechanism is the one described for chip component cracks.

Edge Quality

The edge may need to be free of burrs, of loose fibres and of roughness, depending on whether it is visible or whether it slides into a housing. The requirement should be stated rather than assumed.

A routed edge and a snapped edge are visibly different, and a customer expecting one will reject the other. The drawing should specify the method or the acceptance criterion.

Throughput and Changeover

The cycle time of the method determines how many operators are needed, and the changeover determines how the method handles a mix of products. A router needs a program per panel, while a manual fixture needs a different fixture.

Where the product mix is wide, the changeover time can exceed the cutting time, which is the argument for a programmable method.

Handling After Separation

Boards that have been separated are loose units, and they are handled individually from that point. The handling should be defined for the equipment that follows, since the loose part of the process is where damage occurs.

Where possible, the depanelling should occur as late as possible, so that the boards are handled as a panel for as long as the process allows.

Records

The method, the tooling and the support arrangement should be recorded for each product, together with any damage found. Where a crack appears in the field, that record is where the investigation starts.

It belongs with the process evidence described for manufacturing processes.

Process Control and Verification

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.

Checks Before Release

The checks that matter are the ones performed on the product rather than on a sample kept for the purpose, because a coupon that travels with the panel is the only evidence about that panel. Where a requirement can be measured, it should be measured at the point of manufacture and recorded against the board or the lot it applies to.

A parameter that is set once and never re verified drifts, and the drift is usually discovered by a defect rather than by the record. The tooling, the material and the profile form one system, and a change to any of them should be assessed against the other two before it is released.

Where the process window is narrow, the measurement resolution has to be better than the window, or the data cannot distinguish a good part from a marginal one.

FAQ

Which method damages components least? A laser, because it applies no mechanical force, followed by routing with proper support.

Can a router cut a curved outline? It can follow any path in the program, which is one of its advantages over a V-cut.

Does depanelling create static? Router dust and the separation itself can, so ionisation is used on the machine.

When should the method be chosen? At panel design time, because the break feature and the tooling have to match.