3.13 Depanelization Choices

Depanelization is the final mechanical process that separates individual Printed Circuit Boards (PCBs) from the large manufacturing array after assembly and soldering are complete. The choice of method is a critical Design for Manufacturability (DFM) decision, directly trading off production volume and cost against the mechanical stress applied to sensitive components and solder joints. Failure to manage stress during this step can lead to hidden failures like micro-cracks in ceramic capacitors or weakened BGA joints.

3.3.13.1 Panel Connection Methods

The method of panelization defines the required depanelization tool. This decision must be locked in during the design phase.

Connection Method	Design Features	Best Use Case	Stress Profile
V-Scoring (V-Cut)	V-shaped groove cut into the top and bottom of the panel (leaving ≈ 1/3 thickness).	High-Volume production with straight-line cuts (rectangular/square boards).	High Stress near the score line; requires careful component spacing.
Tab Routing (Mouse Bites)	Individual boards milled out, connected only by thin perforated break-away tabs.	Irregular shapes and designs requiring high mechanical support during assembly.	Low Stress in the board center; stress is localized at the tab break point.

3.13.2 Depanelization Technologies: Stress vs. Throughput

The technology chosen must minimize stress near sensitive components (e.g., fine-pitch SMT, ceramic capacitors, BGAs). A general corporate limit for acceptable stress near a component is often 200 microstrain (µε).

Method	Mechanism	Advantages	Disadvantages & Stress
Router/Milling	Uses a rotating bit to mill away the tab material between boards.	Low Stress transmission; ideal for complex contours and non-straight lines.	Slower cycle time than V-cut; high maintenance (bit wear); generates dust.
Pizza Cutter / Shearing	A fixed or powered rotary blade separates V-scored boards.	Fast cycle time; low equipment cost; suitable for medium-volume straight cuts.	High Stress near the cut line; limited to straight cuts only.
Punching/Die Cutting	Uses custom die blades to punch out the board in a single press.	Highest Throughput for mass production; excellent speed.	High Fixture Cost (NRE); introduces high, localized mechanical stress.
Laser Cutting (UV/CO2)	Uses a focused laser beam (UV preferred) to ablate the material.	Non-Contact (zero mechanical stress); highest precision; ideal for thin/flexible boards.	Highest CapEx; limited to thin materials (≤ 1 mm); thermal residue possible.
Hand Breaking (Snapping)	Manual bending along a V-score or perforated tab.	Lowest cost; simple; suitable for prototyping or low volume.	Highest and least controllable stress; operator inconsistency; risks cracking ceramic capacitors.

3.13.3 Design for Depanelization (DFD) Mandates

The decision on the separation method must be made at the DFM stage (Chapter 1.1) to ensure component placement accommodates the mechanical risk.

Component Keepout: Critical components (BGAs, ceramic capacitors ≤ 0603 size) must be placed away from the separation line. A minimum clearance of 3 mm from the cut line (V-cut or tab) is typically mandated. Placing capacitors parallel to the edge reduces the risk of cracking compared to perpendicular placement.
V-Cut Depth: The V-groove depth must be consistent, typically ≈ 1/3 of the PCB thickness, to ensure clean separation without excessive force.
Tooling Holes: The final individual PCB must include tooling holes near the edges to allow for post-depanelization alignment during ICT/FCT (In-Circuit Test/Functional Test).

3.13.4 Stress Reduction Strategy

If mechanical methods (routing, V-cut) must be used on sensitive boards, specific process controls are mandatory to reduce the strain profile.

Support and Fixturing: Use custom, rigid fixtures to support the panel during separation, preventing flexing or warping that transfers stress to the components.
Speed Control: For routing, reducing the feed rate (cutting speed) decreases vibration and the resulting mechanical stress transferred to the board edges.
Stress Monitoring: On high-risk NPI builds, use strain gauges (per IPC/JEDEC-9702) near sensitive components to qualify the chosen depanelization method against a 200 to 250µε limit.

Final Checklist: Depanelization DFM Audit

Parameter	Mandate	Rationale
Connection Method	Method (V-Cut or Tab Route) must be chosen based on board shape and volume.	V-Cut for straight high volume; Tab Route for complex contours.
Component Clearance	Critical SMT components (BGAs, ≤ 0603 chips) placed ≥ 3 mm away from the separation line.	Prevents component cracking and solder joint micro-fractures from mechanical stress.
Separation Tool	Router or Laser must be selected for sensitive or irregularly shaped PCBs.	Avoids uncontrolled, high-stress methods like Hand Breaking, which causes hidden defects.
Tooling Integrity	Router bits, punches, or V-cut blades must be maintained and sharpened on a PM schedule.	Dull tools increase mechanical stress and result in rough edges or burrs.
Post-Process Check	Boards must be inspected (AOI/microscope) for burrs or micro-cracks after separation.	Ensures dimensional accuracy and prevents enclosure fitting issues.