Introduction to Breakaway Tabs PCBs

A breakaway tabs printed circuit board (PCB) is a convenient way to panelize and depanelize PCBs for manufacturing. The individual circuit boards are connected together into a larger panel by small tabs. After assembly, the individual boards can be easily snapped apart or “broken away” from the main panel along the tabs.

Breakaway tab PCBs offer several advantages:

• Allow multiple smaller PCBs to be produced on one panel, reducing manufacturing cost
• Boards stay securely connected during assembly
• Individual boards can be easily separated after assembly
• No special depaneling tools or equipment needed

In this guide, we’ll cover everything you need to know about designing, manufacturing, and using breakaway tab PCBs, including:

• PCB Panelization basics
• Designing breakaway tabs
• Specifying breakaway tabs to your manufacturer
• Depaneling techniques
• Tips and best practices

Whether you’re an electrical engineer, PCB designer, or electronics hobbyist, understanding breakaway tabs is a useful skill for cost-effective PCB manufacturing. Let’s dive in!

PCB Panelization Basics

Before we get into the specifics of breakaway tabs, it’s important to understand the basics of PCB panelization. Panelization is the process of laying out multiple individual PCBs onto a larger panel for production.

Why Panelize?

The main reason to panelize PCBs is to reduce manufacturing costs. It’s generally more economical to produce a larger number of smaller PCBs on one big panel than to manufacture them individually.

Some specific benefits of panelization include:

• Reduced tooling and setup costs by processing multiple PCBs at once
• Faster assembly since components can be loaded on several boards simultaneously
• Easier handling of boards during manufacturing

Panelization Methods

There are a few different ways that PCBs can be panelized together:

Method	Description
V-Score	Shallow grooves cut or scored in between boards, allowing them to be snapped apart after assembly
Tab Routing	Individual boards connected by short tabs that are milled away after assembly
Perforations	A series of drilled holes between boards that allow them to be broken apart
Breakaway Tabs	Small joining tabs designed into the PCB that can be snapped off after assembly

Each method has its own pros and cons in terms of ease of design, manufacturing cost, and depaneling. In this guide we’ll be focusing specifically on using breakaway tabs.

Designing Breakaway Tabs

Now that you understand the basics of panelization, let’s look at how to actually design breakaway tabs into your PCB. There are a few key factors to consider.

Tab Placement

The first step is to decide where to place the breakaway tabs around the perimeter of your individual board. Some tips:

• Place tabs symmetrically on opposite sides to balance connection strength
• Avoid placing near sensitive components or connectors
• Ensure tabs won’t interfere with the final enclosure or case
• Leave room for any required tooling holes or fiducials
• Follow any specs provided by your contract manufacturer

In general, 2-4 tabs per board is sufficient, with tabs on each side for larger boards. Placing near board corners can minimize wasted material.

Tab Size

Next you need to determine the size of your breakaway tabs. This primarily depends on the thickness of your PCB – thicker boards require larger tabs.

Typical tab sizes for common PCB thicknesses:

PCB Thickness	Min. Tab Size
0.8 mm	0.8 mm
1.0 mm	1.0 mm
1.2 mm	1.2 mm
1.6 mm	1.6 mm

The tab size is the minimum width of the tab at its narrowest point. Wider tabs are stronger but more difficult to separate cleanly.

In addition to the width, you’ll need to specify the tab length, which is typically 2-3x the tab width.

Tab Shape

The shape of the breakaway tab determines how it will snap off after assembly. There are a few common options:

Shape	Description
Straight	Connects at board edge, may leave some material behind when depaneled
Notched	Recessed connection point encourages clean break inside board edge
Perforated	Series of drilled holes define break line, can snap off very cleanly
Snap-Off	Narrowed neck triggers break right at edge when levered up and down

Your CM may have a standard tab shape they prefer, or you can specify based on your depaneling and appearance requirements.

Clearance

Finally, ensure there is adequate clearance around your breakaway tabs – at least 3-5x the tab width. This empty space prevents components from interfering with the tabs and gives room to get snips or other tools around the tabs during depaneling.

Specifying Breakaway Tabs

Once you’ve designed your breakaway tabs, you need to clearly communicate your specifications to your PCB contract manufacturer.

Mechanical Layer

The first step is to draw the tabs on a dedicated mechanical layer of your PCB design files. This is typically a separate Gerber layer from your copper and mask layers.

Draw the tabs as uncovered copper with no soldermask. Use dimensions to specify the widths and lengths. Clearly label the layer as breakaway tabs or panelization.

Fabrication Drawing

In addition to the design files, it’s a good idea to provide a fabrication drawing that spells out your panelization and breakaway tab requirements. This can be a simple PDF or image file showing:

• Number of boards per panel
• Tab locations and spacing
• Tab size and shape
• Any special instructions

Err on the side of over-specifying to avoid confusion or manufacturing issues.

Communicate with CM

Before beginning production, ensure your contract manufacturer understands and can meet your breakaway tab specifications. They may have suggestions or feedback on your panelization approach.

Request a design for manufacturing (DFM) check and review any comments carefully. Ensure a final pre-production proof matches your specifications before giving approval to begin fabrication.

Depaneling Breakaway Tabs

After your boards are fabricated and assembled, the last step is separating or “depaneling” them from the main panel. Breakaway tabs are designed to make this easy.

By Hand

The simplest depaneling method is to just snap the individual boards off by hand. To do this:

1. Grip the board firmly on each side of the tab
2. Apply sharp pressure down and up to fatigue the tab
3. Bend the board back and forth until the tab breaks off
4. Repeat for any remaining tabs

Straight or notched tabs are best for hand depaneling. Be careful not to damage any components near the edges of the board. Wear safety glasses in case a tab flies off unpredictably.

Cutting

For thicker boards or perforated/snap-off tabs, you may need to use cutting tools to depanel. Options include:

• Shears or snips
• Nippers
• Razor knife
• Depaneling saw or router

Ensure tools are appropriately sharp and sized for your tabs and board thickness. Avoid cutting into the board itself. Cut over a protective surface in case a tab flies off. Again, wear proper safety equipment.

Machines

For large volumes, you may want to invest in automated depaneling machines. These use lasers, saws, routers, or punches to quickly separate many boards at a time.

Work with an equipment vendor to spec a depaneling solution appropriately sized for your boards, panel design, and volume. Look for machines with adjustable depth control and dust/debris extraction.

Tips and Best Practices

A few final tips to keep in mind when using breakaway tabs:

• Symmetric tab arrangement to balance cutting force
• Design footprint for worst case component placement
• Ensure fab and assembly houses are comfortable panelizing
• Clean up any tab remnants after depaneling
• Factor in depaneling labor and yield loss to NRE
• Order spare PCBs to account for depaneling mistakes
• Double check CM specs before production

Conclusion

Breakaway tabs are a cost-effective and efficient way to panelize PCBs for manufacturing. By understanding the design considerations, specifying clearly to your manufacturer, and following best practices for depaneling, you can take advantage of this useful technique in your own PCB projects.

FAQ

Q: When should I use breakaway tabs vs. other panelization methods?

A: Breakaway tabs are best for simpler 2-layer or 4-layer PCBs under 1.6mm thickness. For thicker, multilayer, or higher density boards, scoring, routing, or perforations may be preferable. Weigh factors of design effort, fab cost, depaneling ease, and aesthetics.

Q: Are there any situations where I shouldn’t use breakaway tabs?

A: Avoid using breakaway tabs for very thin boards under 0.8mm, thick boards over 2.0mm, high voltage/current designs, boards with edge plating, or designs where space is extremely tight. Tabs also may not be suitable if you need a perfectly clean board edge after depaneling.

Q: What problems can arise from designing breakaway tabs incorrectly?

A: Common issues include tab placement interfering with components, tabs that are too small and break prematurely, and unclean snapping. Following the tab size and clearance guidelines in this guide will help you avoid these problems.

Q: How much do breakaway tabs add to PCB fabrication cost?

A: The cost impact is generally small, especially compared to the savings of producing multiple boards on one panel. Simple straight breakaway tabs impose no added cost beyond the panelization labor. More complex notched, perforated, or snap-off tabs may incur a small additional routing, drilling, or lamination charge.

Q: Where can I find more resources on breakaway tab design?

A: Many PCB manufacturers and design software companies (Altium, Cadence, Mentor) offer detailed guides and tutorials on panelization and breakaway tab design. The IPC also publishes standards on this topic. Consult with your CM for their specific breakaway tab guidelines and capabilities.