Learning objectives
- Compare V score, routing, punch and laser depaneling methods
- Support boards during separation so bending stress stays out of the joints
- Explain why components near the break edge are at risk, especially ceramic parts
- Dress, inspect and clean separated edges before boards move on
Lesson
Boards travel through the line as panels, and at some point each panel must become individual products. That is depaneling, and it deserves more respect than it usually gets, because mechanical stress applied carelessly here can destroy boards that passed every inspection and test upstream. The methods trade cost, speed and stress against each other. A V score line, a shallow groove cut into both faces of the panel, is broken apart with a wheel or guillotine style separator, fast and cheap for straight edges. A router cuts through the tabs, called mouse bites, that hold boards in a routed panel, and can follow any outline, but it generates dust that must be extracted and its bits wear and must be managed. A punch shears boards out in one stroke for suitable high volume shapes. Laser depaneling cuts with no mechanical contact at all and is the low stress option for delicate assemblies.
The physics of the stage is bending. When a scored panel is snapped or a tab is cut, stress travels through the board. Ceramic capacitors and crystals are brittle, and solder joints near an edge are stiff, so both can crack under stress that the board appears to survive. Industry writing carries a cautionary tale every trainee should hear: a board passed every electrical test, then depaneling stress cracked components near its edge, and the failure only appeared later as unreliable product in the field. Design defends against this by keeping sensitive components at a safe distance from break edges, and the operator defends against it in person, supporting the board fully during the break, breaking in the correct direction and sequence, and never forcing, twisting or levering a panel apart by hand because the schedule is pressing.
After separation, edges are inspected and dressed where mouse bite remains are rough, dust from routing is removed, and the separated boards are handled with the same ESD and edge handling discipline as every other stage. Edge cracks, haloing and delamination at the break line are dispositioned honestly, never hidden inside a stack of good boards. James Onsomu teaches standard work and careful adherence to process throughout his writing on lean manufacturing. Depaneling is a short stage with a long shadow: the last mechanical act of the line either protects everything the previous stages built, or quietly breaks it.
Key numbers
- Component clearance: sensitive parts, especially ceramic capacitors and crystals, kept at the safe distance from break edges set by the design
- Board support: the board fully supported through 100 percent of every break or cut
- Router condition: bit wear checked and bits changed on schedule, since worn bits raise stress and roughen edges
- Stress rule: force, twisting and hand levering of panels are prohibited, with zero exceptions for schedule pressure
Defects to spot
- Edge cracks and delamination: excess bending stress during the break
- Haloing along the break line: worn cutting tools or force used instead of a clean cut
- Cracked components near the edge: depaneling stress reaching brittle ceramic parts
- Cracked solder joints near the edge: stress travelling into joints after every test had passed
- Rough mouse bite edges: router bit wear or skipped edge dressing
- Dust contamination: routing dust not extracted or cleaned from the boards
Stage check, self test
Answer each question, then open the answer to check yourself. Passing standard: 80 percent, at least 4 of 5 correct.
1. Why can depaneling ruin a board that passed every test?
A. It erases the test results
B. Bending stress can crack ceramic components and solder joints near the break edge
C. It makes the board too clean
D. It changes the firmware
Show answer
Answer: B
2. Which depaneling method applies no mechanical contact stress to the board?
A. V score snapping
B. Punching
C. Laser depaneling
D. Hand twisting
Show answer
Answer: C
3. A panel resists separation near the end of a shift. What is correct practice?
A. Twist and lever it apart by hand to keep the schedule
B. Stand on the fixture for more force
C. Skip the check and let packing sort it out
D. Support the board fully and use the correct tool and sequence, never forcing the break
Show answer
Answer: D
4. Rough mouse bite edges are getting worse across a run of routed panels. What should be checked?
A. Router bit condition and wear
B. The colour of the tabs
C. The label stock
D. The humidity in the packing area
Show answer
Answer: A
5. Why does design keep ceramic capacitors and crystals away from break edges?
A. They are heavy
B. They are brittle and crack under depaneling stress
C. They are expensive to insure
D. They block the conveyor sensors
Show answer
Answer: B
Previous: Stage 15: Conformal coating
Next: Stage 17: Final assembly, final inspection and packing