V-Scoring vs Mouse Bites vs Tab Routing vs Milling: Complete PCB Depaneling Guide

If you’ve ever held a freshly assembled PCB panel in your hands and wondered how to separate those boards without cracking solder joints or damaging components, you’re in the right place. After 15 years designing and manufacturing circuit boards, I’ve seen every depaneling disaster imaginable—from shattered ceramics to stress-cracked BGAs. This guide breaks down the four major depaneling methods so you can pick the right one for your next project.

Quick answer: V-Scoring works best for high-volume rectangular boards. Mouse Bites suit irregular shapes and prototypes. Tab Routing handles complex outlines with edge components. Milling delivers the lowest stress for sensitive assemblies. Most production panels use a combination of methods.

What Is PCB Depaneling and Why Does It Matter?

PCB depaneling (also called singulation) is the process of separating individual circuit boards from a larger manufacturing panel. During fabrication and assembly, multiple PCBs are arranged on a single panel to improve efficiency and reduce costs. Once assembly is complete, these boards need to be separated—and this is where method selection becomes critical.

The wrong depaneling method can introduce mechanical stress that damages components, cracks solder joints, or causes latent failures that show up months later in the field. I’ve seen entire production runs scrapped because someone chose V-Scoring for a board with edge-mounted BGAs.

Key Factors in Choosing a Depaneling Method

Before diving into each method, consider these decision factors:

• Board shape: Rectangular vs. irregular outlines
• Component placement: How close are parts to the board edge?
• Production volume: Prototype vs. high-volume manufacturing
• Stress sensitivity: Are there fragile components like ceramic capacitors or fine-pitch BGAs?
• Edge quality requirements: Does the final product need smooth edges?
• Cost constraints: Tooling costs vs. per-unit processing costs

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V-Scoring: The Workhorse of High-Volume Production

V-Scoring (also called V-Cut or V-Groove) is the most common depaneling method in the industry. It involves cutting V-shaped grooves into both the top and bottom surfaces of the PCB panel, creating a weakened line where boards can be easily separated.

How V-Scoring Works

A specialized scoring machine uses two rotating blades positioned point-to-point—one above and one below the panel. As the PCB passes between the blades, they cut V-shaped grooves at the predetermined separation lines. The standard approach removes approximately one-third of the board thickness from each side, leaving one-third as a connecting web.

V-Scoring Design Specifications

Parameter	Specification	Notes
V-Groove Angle	20°, 30°, 45°, or 60°	30° is most common
Residual Thickness	0.3mm–1.0mm	Typically 1/3 of board thickness
Minimum Board Thickness	0.6mm (0.8mm recommended)	Thinner boards risk breakage
Residual Thickness Tolerance	±0.1mm	Per IPC-6012E standards
Blade Alignment Tolerance	±0.05mm	Critical for clean breaks
Component Clearance	1mm minimum from V-groove edge	2mm for ceramic capacitors
Maximum Panel Size	600mm × 1200mm	Varies by equipment
Minimum Panel Size	60mm × 45mm	Varies by equipment

When to Use V-Scoring

V-Scoring excels in these scenarios:

• Rectangular or square board shapes with straight edges
• High-volume production runs (10,000+ units)
• Boards where components are at least 1mm from the edge
• Projects where processing speed is critical
• Cost-sensitive applications where minimal material waste matters

V-Scoring Advantages

• Fast processing: Panels pass through the scorer in seconds
• Minimal material waste: V-grooves add almost no additional space between boards
• Low tooling cost: Standard blades work for most applications
• High panel density: More boards fit per panel compared to tab routing
• Automated separation: Compatible with automated depaneling equipment

V-Scoring Limitations

• Straight lines only: Cannot accommodate curves or complex shapes
• Mechanical stress during separation: Breaking the web creates bending stress
• Edge quality: May leave slightly rough edges requiring post-processing
• Component restrictions: Not suitable for parts hanging over board edges
• Panel strength: Deep scores can cause warping in wave soldering

V-Scoring Best Practices

1. Keep traces 1mm from the V-groove edge to prevent damage during separation
2. Pull back inner layer planes 1mm from the score line
3. Use jump scoring on leading/trailing panel edges to prevent sagging in wave solder
4. Orient chip components parallel to the score line to minimize separation stress
5. Communicate with your fabricator about V-groove angle requirements

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Mouse Bites: Flexibility for Irregular Shapes

Mouse Bites (also called stamp holes or perforated breakaway tabs) use a series of small drilled holes to create a perforated line—similar to the tear-off edge of a postage stamp. After assembly, boards are snapped apart along this perforation.

How Mouse Bites Work

During PCB fabrication, the manufacturer drills a line of small holes (typically 5-8 holes per tab) at strategic locations along the board outline. These holes are positioned close together, leaving only thin strips of material between them. When force is applied, the board breaks cleanly along the perforation, leaving small nubs that can be filed smooth if needed.

Mouse Bites Design Specifications

Parameter	Specification	Notes
Hole Diameter	0.5mm–1.0mm	0.5mm (0.020″) standard
Hole Spacing	0.35mm–0.4mm edge-to-edge	Minimum 0.3mm for strength
Holes Per Tab	5–8 holes	5 holes minimum recommended
Tab Spacing	60mm–90mm apart	77mm center-to-center recommended
Component Clearance	2mm minimum	3mm for sensitive parts
Panel Spacing	1.6mm–2.0mm	Minimum 1.2mm
Board-to-Rail Distance	Mouse bites on one side only	Two sides for board-to-board connections

When to Use Mouse Bites

Mouse Bites are ideal for:

• Irregularly shaped or round PCB outlines
• Low-to-medium volume production
• Prototype runs and hand assembly
• Boards that need flexibility in panelization
• Projects where V-Scoring isn’t feasible due to shape

Mouse Bites Advantages

• Shape flexibility: Works with any board outline—circular, curved, or complex
• Low tooling cost: Uses standard CNC drill bits, no special equipment needed
• Easy hand separation: Boards snap apart with minimal tools
• Compatible with routing: Often combined with tab routing for best results
• No specialized equipment: Can be separated manually or with basic tools

Mouse Bites Limitations

• Rough edges: Leaves visible “bite marks” requiring filing or sanding
• Panel space consumption: Tabs require additional clearance between boards
• Weaker than V-Scoring: May break prematurely during handling
• Post-processing: Edge cleanup adds labor time
• Not ideal for cosmetic products: Visible edge imperfections

Mouse Bites Best Practices

1. Use staggered hole patterns for more predictable breaks
2. Place mouse bites in blank areas away from traces and vias
3. Add at least 2 tab sets per board edge for boards up to 30mm wide
4. Maintain 0.125″ clearance from mouse bites to nearby components
5. Consider board thickness: Thicker boards may need larger holes or wider spacing

Read more: A Step-by-Step Introduction of PCB Manufacturing :

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Tab Routing: Precision for Complex Designs

Tab Routing (also called route and retain) combines CNC routing of the board outline with small connecting tabs that hold boards in place during assembly. These tabs—often reinforced with mouse bites—are removed during depaneling.

How Tab Routing Works

A CNC router mills around the entire PCB outline, leaving only small tabs (typically 3mm wide) to connect the board to the panel frame. These tabs can be solid or perforated with mouse bites for easier separation. After assembly, boards are removed by breaking the tabs or re-routing them with a depaneling router.

Tab Routing Design Specifications

Parameter	Specification	Notes
Tab Width	3mm ±0.25mm	Standard width
Tab Location Tolerance	±0.5mm	Position accuracy
Router Bit Diameter	2mm–3.175mm	2mm common for tight spacing
Board Spacing	2mm minimum	To accommodate router bit
Tab Spacing	75mm ±12mm apart	3-5 tabs per board side
Distance from Corners	9mm minimum	Avoid weak corner areas
Distance from Radii	6mm minimum	Prevents tab breakage issues
Component Clearance	2mm–3mm from routed edge	3mm for stress-sensitive parts
Perforation Holes	4–5 holes per tab	If using perforated tabs
Perforation Diameter	0.5mm (0.02″)	Standard size

When to Use Tab Routing

Tab Routing is the right choice for:

• Non-rectangular board shapes (round, curved, irregular)
• Boards with components hanging over the edge
• Designs requiring smooth, clean edges
• Mixed panels with different board designs
• Applications where edge quality is critical

Tab Routing Advantages

• Shape freedom: Handles any board outline—curves, radii, complex shapes
• Clean edges: Routed edges are smooth and consistent
• Edge component friendly: Accommodates overhanging connectors and parts
• Lower separation stress: Less mechanical stress than V-Score breaking
• Mixed panel support: Different board designs can share a panel

Tab Routing Limitations

• Slower processing: Routing takes significantly longer than V-Scoring
• More panel waste: Router paths consume material between boards
• Tab remnants: Small nubs may remain after separation
• Higher cost: More machine time and potential for tooling wear
• Dust generation: Routing creates FR4 dust requiring vacuum extraction

Tab Routing Best Practices

1. Never place tabs near component holes or traces to prevent fracturing
2. Align tabs along X-Y axes when possible for cleaner breaks
3. Use perforated tabs for manual separation to reduce stress
4. Avoid placing tabs under overhanging components
5. Extend perforation break axis to panel edge for even pressure distribution
6. Keep all perforations along a single break line to prevent perpendicular stress

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Milling (Router Depaneling): Lowest Stress Solution

Milling or router depaneling uses a high-speed CNC router to completely cut boards from the panel—either by removing tabs or performing a full cut-out. This method generates the lowest mechanical stress of any depaneling technique.

How Milling Depaneling Works

A precision CNC router with a high-speed spindle (30,000–60,000 RPM) follows programmed cutting paths to separate boards from the panel. The router bit mills through the connecting material without bending or flexing the PCB, eliminating the mechanical stress associated with breaking or snapping boards apart.

Milling Equipment Specifications

Parameter	Specification	Notes
Spindle Speed	30,000–60,000 RPM	Higher speed = cleaner cut
Router Bit Diameter	1.0mm–2.0mm	1.2mm common
Feed Rate	15–100mm/sec	Material dependent
Cutting Accuracy	±0.02mm	High precision capability
Positioning Accuracy	±0.02mm	CCD vision alignment common
PCB Thickness Range	0.4mm–3.0mm	Equipment dependent
Typical Cutting Stress	<500 µε (microstrain)	Lowest of all methods

Stress Comparison: Milling vs Other Methods

Research data from strain gauge testing shows significant differences in mechanical stress across depaneling methods:

Depaneling Method	Stress Level (Parallel to Cut)	Stress Level (Perpendicular to Cut)
Router/Milling	Lowest	Lowest
Die Cutting	Low-Medium	Medium
V-Score Rolling Blade	High	Highest
Hand Breaking	Very High	Very High

Source: Strain gauge measurements on 1.2mm FR4 PCB samples

When to Use Milling Depaneling

Milling is the preferred method for:

• High-density boards with components near the edge
• Assemblies with stress-sensitive components (ceramic caps, BGAs)
• Medical, aerospace, and automotive reliability requirements
• Complex board shapes requiring full cut-out
• Applications where zero mechanical stress is mandatory

Milling Advantages

• Lowest mechanical stress: Eliminates bending stress on components and solder joints
• Highest precision: Achieves ±0.02mm cutting accuracy
• Clean edges: Produces smooth, burr-free cuts
• Shape flexibility: Cuts curves, radii, and complex outlines
• Consistent results: Automated process ensures repeatability
• Non-linear cutting: Handles any geometry unlike V-Scoring

Milling Limitations

• Equipment cost: CNC routers represent significant capital investment
• Slower than V-Score: Processing time is longer per panel
• Dust generation: Requires effective vacuum extraction system
• Bit wear: Router bits need regular replacement
• Not ideal for thin/flexible boards: Better suited for rigid PCBs
• Heat generation: High-speed routing may require process control

Milling Best Practices

1. Use vacuum fixturing to secure boards and prevent movement
2. Implement dust extraction at the cutting point for cleanliness
3. Monitor bit wear and replace before precision degrades
4. Program optimal feed rates based on board material and thickness
5. Use vision alignment for maximum positional accuracy

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Advanced Milling Techniques and Considerations

Inline vs Offline Router Systems

Production environments typically choose between two router configurations:

Inline Routers integrate directly into the SMT production line, depaneling boards immediately after assembly. These systems offer:

• Continuous flow production without operator intervention
• Reduced handling and potential for damage
• Higher initial investment but lower per-unit labor costs
• Best for high-volume, dedicated product lines

Offline Routers operate as standalone stations where panels are manually loaded and unloaded:

• Lower capital investment
• Flexibility to handle multiple product types
• Better for low-to-medium volume or high-mix production
• Easier to implement quality checks between stages

Vision Alignment Systems

Modern router depaneling machines use CCD camera systems to:

• Automatically locate fiducial marks on each panel
• Compensate for panel registration errors
• Adjust cutting paths in real-time
• Achieve positioning accuracy of ±0.02mm

This vision-based alignment is critical when cutting close to components or when panel-to-panel variation exists.

Dust Control and Contamination Prevention

Router depaneling generates significant FR4 dust that can:

• Contaminate sensitive components
• Create electrical shorts
• Pose health hazards to operators
• Accumulate in equipment causing maintenance issues

Effective dust management requires:

• Vacuum extraction at the cutting point
• ESD-safe vacuum systems to prevent static discharge
• Regular filter maintenance
• Ion air guns to remove residual particles from finished boards

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Complete Comparison: V-Scoring vs Mouse Bites vs Tab Routing vs Milling

Criteria	V-Scoring	Mouse Bites	Tab Routing	Milling
Board Shapes	Rectangular only	Any shape	Any shape	Any shape
Edge Quality	Rough	Rough (nubs)	Smooth	Smooth
Mechanical Stress	Medium-High	Medium	Low-Medium	Lowest
Processing Speed	Fastest	Medium	Slow	Medium-Slow
Tooling Cost	Low	Low	Medium	High
Panel Utilization	Highest	Medium	Lower	Medium
Edge Components	Not suitable	Limited	Suitable	Suitable
Production Volume	High volume	Low-Medium	Medium	Medium-High
Post-Processing	Minimal	Filing needed	Minimal	None
Equipment Cost	Low	Low	Medium	High
Dust Generation	None	None	High	High
Best For	Simple, high-volume boards	Prototypes, irregular shapes	Complex shapes, edge parts	Sensitive assemblies

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Hybrid Approaches: Combining Depaneling Methods

In real-world production, many panels use multiple depaneling methods to optimize results. Common combinations include:

V-Scoring + Tab Routing

• V-Score the straight edges
• Tab route the irregular sections
• Best of both worlds for mixed geometry

Tab Routing + Mouse Bites

• Route the board outline
• Add mouse bite perforations to tabs for easy hand separation
• Ideal for prototype and low-volume production

V-Scoring + Mouse Bites

• V-Score the main panel breaks
• Add mouse bites for internal board-to-board connections
• Good for maximizing panel density with some shape flexibility

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How to Choose the Right Depaneling Method

Use this decision flow to select the optimal method for your project:

Step 1: Board Shape

• Rectangular with straight edges → Consider V-Scoring
• Irregular, round, or complex → Go to Step 2

Step 2: Edge Components

• Components overhanging edges → Tab Routing or Milling
• No edge components → Go to Step 3

Step 3: Stress Sensitivity

• Ceramic capacitors, fine-pitch BGAs near edge → Milling
• Standard components with 2mm+ clearance → Go to Step 4

Step 4: Production Volume

• High volume (10,000+) → V-Scoring (if shape allows) or Milling
• Low-medium volume → Mouse Bites or Tab Routing

Step 5: Edge Quality Requirements

• Cosmetic/precision edges needed → Tab Routing or Milling
• Edge quality not critical → V-Scoring or Mouse Bites

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Cost Analysis: Understanding the True Cost of Each Method

When evaluating depaneling methods, consider both direct and indirect costs:

Direct Costs

Cost Factor	V-Scoring	Mouse Bites	Tab Routing	Milling
Equipment Investment	$5K–$20K	Included in fab	$15K–$50K	$30K–$150K
Tooling Per Panel	~$0.01	$0	~$0.05	~$0.10
Cycle Time (per panel)	5–10 sec	N/A	30–120 sec	20–60 sec
Labor for Separation	Low	Medium	Low–Medium	None
Consumables	Blade sharpening	None	Router bits	Router bits

Hidden Costs to Consider

• Scrap rate: Higher stress methods may increase component failures
• Rework costs: Damaged boards during separation require repair or replacement
• Quality inspection: Some methods require additional edge inspection
• Field failures: Latent stress damage can cause warranty returns
• Panel efficiency: Methods requiring more spacing reduce boards per panel

Total Cost of Ownership Example

For a production run of 100,000 boards:

• V-Scoring might cost $0.02/board but risk 0.5% stress-related failures
• Milling might cost $0.08/board but reduce failures to 0.05%
• If each field failure costs $50 in warranty service, milling could save $22,500 despite higher upfront costs

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Useful Resources and Tools

IPC Standards for PCB Depaneling

• IPC-2221: Generic Standard on Printed Board Design
• IPC-6012E: Qualification and Performance Specification for Rigid PCBs
• IPC-7351: Generic Requirements for Surface Mount Design

Design Software with Panelization Support

• Altium Designer (Embedded Board Array tool)
• KiCad (KiKit plugin for panelization)
• Eagle (ULP scripts for panelization)
• OrCAD PCB Designer

Online Panelization Tools

Most major PCB manufacturers offer free online panelization tools:

• JLCPCB Panel Builder
• PCBWay Panelization Service
• Eurocircuits Panel Editor

Equipment Manufacturers

• V-Score Equipment: Manncorp, Fancort, CAB
• Router Depaneling: IPTE, Sayaka, Genitec
• Laser Depaneling: LPKF, Coherent, Han’s Laser

Frequently Asked Questions About PCB Depaneling

What is the difference between V-Scoring and Mouse Bites?

V-Scoring cuts V-shaped grooves into the PCB panel to create a weakened breaking line, while Mouse Bites use drilled holes to create a perforation. V-Scoring produces cleaner edges and works only for straight lines, while Mouse Bites accommodate any board shape but leave rough edges requiring post-processing. V-Scoring is faster and wastes less material, making it preferred for high-volume production of rectangular boards.

Can I use V-Scoring for irregularly shaped PCBs?

No. V-Scoring can only create straight-line separations because the scoring blades must travel in a continuous line across the panel. For irregular, curved, or complex board shapes, you need Tab Routing or Mouse Bites. Some manufacturers combine V-Scoring for straight edges with Tab Routing for curved sections on the same panel.

How close can components be to the board edge for each depaneling method?

Component clearance requirements vary by method:

• V-Scoring: Minimum 1mm, 2mm recommended for ceramic capacitors
• Mouse Bites: Minimum 2mm, 3mm for sensitive components
• Tab Routing: Minimum 2-3mm from routed edges
• Milling: Can accommodate components as close as 1mm with proper fixturing

Always consult your manufacturer’s DFM guidelines for specific requirements.

Which depaneling method causes the least stress on components?

Milling (router depaneling) generates the lowest mechanical stress because it cuts through material without bending the board. Strain gauge testing shows milling produces stress levels 1/10th of rolling blade V-Score cutters and 1/100th of hand breaking. For assemblies with stress-sensitive components like ceramic capacitors or fine-pitch BGAs near board edges, milling is the safest choice.

Is laser depaneling better than mechanical methods?

Laser depaneling offers the ultimate in precision and zero mechanical stress, but comes with trade-offs. It excels for thin/flexible boards, HDI designs, and applications requiring extreme precision. However, laser systems have higher equipment costs and may be slower for thick FR4 boards. For standard rigid PCB production, mechanical methods like milling often provide the best balance of quality, speed, and cost.

Conclusion

Choosing the right PCB depaneling method isn’t just a PCB manufacturing detail—it directly impacts your product’s reliability and your production costs. V-Scoring remains the go-to choice for high-volume rectangular boards where speed and panel density matter most. Mouse Bites provide flexibility for prototypes and irregular shapes without expensive tooling. Tab Routing handles complex designs with edge components that other methods can’t accommodate. And Milling delivers the lowest-stress separation for your most sensitive assemblies.

In most real-world scenarios, the best approach combines multiple methods on a single panel—V-Score where you can, tab route where you must, and mill when component integrity is paramount.

The key is communicating early with your PCB manufacturer about your specific requirements. Share your board shapes, component placements, and production volumes so they can recommend the optimal panelization strategy. A few hours of upfront planning can save weeks of debugging field failures down the road.