V-score, router or punch: where depaneling stress starts

Panels come apart three ways: a V-score that gets sheared or snapped, routed tabs that get milled or broken, and a punch die that blanks the boards out in one stroke. The stress a board sees at separation is largely decided when the panel is designed, before any machine is chosen. Here is where the stress actually starts in each family.

V-score: the technique decides everything

A V-scored panel has a groove machined into the top and bottom faces at fabrication, leaving a thin web of laminate holding the boards together. The score itself is benign. What matters is how the web is broken, and the spread between good and bad technique is wider in this family than in either of the others.

Hand-snapping the panel is the worst case. The board bends around the groove until the web fractures, and that puts the most strain into the board exactly where the groove runs. Hand-guided circular cutters, a rolling blade with no opposing edge, push the board sideways as they roll, and the strain changes with feed rate. An opposing-blade shear cuts the web between two edges, so the force stays inside the groove instead of bending the board around it. Our VPD5-330 does it with an average board strain under 120 microstrain (µε), measured with strain gauges during the cut.

Same panel, three techniques, and a wide gap between the best and the worst. No other separation family has that spread.

Routed tabs and mouse bites

Routed panels hold boards with small tabs, often perforated as mouse bites. A depaneling router mills the tabs away along a programmed path, and it is the lowest-strain mechanical method: the bit removes material rather than displacing it, and the board is fixtured while it happens.

The stress in this family starts when the router is skipped. Tabs twisted or nipped off by hand bend the board locally at every tab position, and each stub left proud of the edge is a stress raiser waiting in the housing. The costs of doing it properly are a program per panel design, bits that wear, dust extraction, and a cycle time that scales with outline length.

Punch dies

A punch die separates every board on the panel in one press stroke. Done right it is fast and consistent: the die is matched to the panel, the boards are supported through the stroke, and the cut happens everywhere at once. The stress profile depends on die sharpness and on how well the board is supported, and it degrades as the tool wears, so the die becomes a maintenance item the way a blade does.

The cost profile is the mirror image of the router. Cycle time is close to nothing, and the money sits in hard tooling cut for one panel design. Every panel revision is a new die, which is why punching suits high volumes of a design that does not change, and very little else.

What decides between them

The panel decides first. Tabs and irregular outlines cannot be V-cut, and a V-scored panel needs neither a router program nor a die. Volume decides the rest: routing and punching each carry per-design overhead, while a V-score shear takes whatever scored panel arrives, with no program and no tooling.

When a strain number has to be proven rather than assumed, IPC/JEDEC-9704 defines how to measure it, with strain gauges at the components during the cut. If you build with ceramics and BGAs on the board, that measurement is worth having before the method argument starts.

Where to go deeper

The depaneling guide compares the four machine classes, manual and pneumatic V-cut, router and laser, on cost, throughput, board types and stress. For V-scored panels specifically, our VPD3-1M is a hand-operated circular-over-linear shear cutting scored panels up to 290 mm (11.4 in), and the VPD5-330 is a foot-pedal pneumatic dual-linear shear cutting up to 330 mm (13 in) on boards 0.6 to 2.54 mm (0.024 to 0.100 in) thick. Both live in the depaneling collection.