Depanelisation Methods and Breakaway Tab Design

A board that has to be depaneled is at its most vulnerable during the separation, because the force applied to break a tab is transmitted into the material around it. Designing the depanelisation step is therefore part of designing the board.

Routing, Scoring and Punching

Routing cuts the board out with a rotating tool and follows any contour, leaving a burr and a gap between adjacent boards. Scoring cuts a shallow V groove on both faces, leaving the material connected until it is broken. Punching removes the material in a single stroke with a shaped tool.

The choice follows from the outline and the volume. A rectangular board at high volume suits scoring or punching, while an irregular outline requires routing. Each method imposes a different clearance along the edge. Our board outline notes describe the tolerances.

Breakaway Tabs and Their Geometry

A tab is a short bridge of material left between the board and the frame, and its dimensions control how the force is distributed. A tab that is too narrow breaks unpredictably; one that is too wide requires a force that damages the surrounding laminate.

Perforations or a pair of closely spaced holes are often placed at the ends of a tab to define the break line and to concentrate the stress where it does no harm. The pattern is part of the design rather than a shop preference. Our breakaway tab notes describe the geometry.

Keep-Outs Along the Break Line

Components and their joints must be kept a defined distance from the break line, because the bending that precedes the break produces a strain that falls off with distance. The keep-out distance depends on the component size and on the stiffness of its joint.

The keep-out applies to both the component body and the solder fillet. A large ceramic capacitor placed close to the line is at risk of a crack that does not appear until the product has been thermally cycled.

Support During Separation

The board should be supported on both sides of the break line during separation, so that the bending is confined to the narrow region intended rather than distributed across the assembly. A fixture that supports the board and applies a controlled moment along the line produces a repeatable result.

Where the separation is done by hand, the result depends on the operator. A snapping motion that works on one board may crack another, which is why the fixture is worth using even at low volume.

Edge Quality and Burrs

A routed edge carries a burr, and a burr on copper can lift the mask and detach a conductor. A scored edge is cleaner but leaves a small ridge that can interfere with a component that overhangs the board edge.

The edge quality requirement should be stated rather than assumed. Where the board edge is visible to the user, the burr removal is a cosmetic requirement as well as a functional one.

Depanelisation Before or After Assembly

Separating the boards before assembly gives a smaller unit to handle and removes the break line from the assembly area, at the cost of losing the panel’s rigidity and requiring a carrier. Separating afterwards keeps the panel rigid but exposes the assembled components to the separation force.

The choice interacts with the assembly equipment limits. Where the panel exceeds the machine’s size, the separation has to come first and the carrier becomes mandatory.

Designing the Tab Pattern

The number and position of the tabs should be chosen so that the board is held rigidly during processing and released without distortion. Too few tabs and the board moves during assembly; too many and the force required to separate it rises.

A tab in the middle of a long edge is usually necessary to stop the board flexing during processing, even though it is far from the corners where the stress is concentrated during separation.

Records and Instructions

The depanelisation method should be stated on the fabrication drawing, together with the tab dimensions and the keep-out. Where the customer depanelises, the instructions should state the method and the fixture requirement.

Leaving the method to the shop produces a panel designed for the shop’s convenience rather than for the assembly requirement. Our fabrication notes guidance lists the entries.

Process Control and Verification

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

Process Control and Verification

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

Process Control and Verification

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

FAQ

Is scoring or routing better? Scoring is cheaper and cleaner for a straight edge and cannot follow a contour. Routing handles any shape and leaves a burr. The choice follows from the outline, and a board with one straight edge and one curved one may use both.

How far should a component be from the break line? Far enough that the bending strain at the component is below the level that would crack it, which in practice means several millimetres for a large ceramic part and less for a small one. The requirement should be stated in the assembly notes.

What does gopcb confirm about depanelisation? We confirm the outline, the method, the tab dimensions, the score depth where applicable and the keep-out around the break line. Where the panel is assembled before separation we also confirm that the tabs can support the panel through the assembly equipment.