You've probably designed plenty of boards with a single cutout—a slot for a connector, a hole for a mounting screw, a notch to clear a component. But sometimes, one cutout isn't enough. Sometimes your board needs two separate openings, or a complex shape that leaves thin bridges of material between voids. That's where double cutout comes in.

Here's the thing: adding internal cutouts isn't as simple as drawing shapes on your layout. Every opening affects the structural integrity of the board. Too close together, and the material between them becomes a weak point. Too close to the edge, and the board can crack during assembly. Get it wrong, and your board might not survive fabrication.

Let's talk about what double cutouts actually are, why you'd need them, and how to design them so your boards come back in one piece.

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What Is a Double Cutout?

A double cutout is exactly what it sounds like: two openings cut out from the interior of a PCB. Unlike the outer board edge, which defines the shape of the board itself, cutouts are holes or slots that go completely through the board but don't touch the outer perimeter.

Think of it like a piece of paper with two holes punched in the middle. The outer edge stays the same, but now there are voids inside the board.

Double cutouts can be:

• Simple cutouts: Two separate holes or slots, not connected

• Complex cutouts: Two openings with a narrow bridge of material between them

• Connected cutouts: Two openings that are actually one irregular shape

The bridge between cutouts is the critical part. If it's too thin, it can break during fabrication, assembly, or normal use.

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Why Would You Need Double Cutouts?

There are plenty of reasons to put multiple internal cutouts in your PCB:

Cable pass-through. If your board sits between two sections of an enclosure, cables might need to run through it. Multiple cables, multiple cutouts.

Component clearance. Sometimes a component on the board needs to sit over an opening—maybe a display that needs to be visible from the other side, or a sensor that needs an unobstructed view. Two components, two cutouts.

Mounting features. Some designs use cutouts to snap into plastic housings or to accommodate mounting hardware. Sometimes you need two separate mounting points.

Thermal management. Cutouts can allow airflow across hot components. Sometimes one opening isn't enough to get the airflow you need.

Weight reduction. In aerospace or portable applications, every gram counts. Removing material where it's not needed lightens the board.

Strain relief. Multiple cutouts can be used to create flexible sections that absorb mechanical stress, protecting solder joints.

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Design Considerations for Double Cutouts

Adding internal cutouts isn't just about drawing shapes. Here's what you need to think about:

Minimum Material Bridges

When you have two cutouts close together, the material between them—called the bridge—has to be strong enough to survive fabrication and assembly. If the bridge is too thin, it can break during handling, depaneling, or even normal use.

The minimum bridge width depends on your manufacturer's capabilities, but a common rule of thumb is at least 1.5mm to 2mm for standard boards. For flexible circuits, you might need even more because the material is less rigid.

Pro tip: If your design calls for a very narrow bridge, consider whether you can combine the two cutouts into one larger opening. A single larger cutout is often stronger than two small cutouts with a thin bridge between them.

Distance from the Board Edge

Cutouts that are too close to the board edge can weaken the outer perimeter. If the distance from the cutout to the edge is less than the board thickness, you risk breaking during fabrication or use.

Corner Radius

Internal corners should be rounded, not sharp. Sharp corners concentrate stress and can become starting points for cracks. A radius of 0.5mm to 1mm is typical, though smaller radii are possible with more advanced manufacturing.

Copper and Component Keepouts

You can't route copper or place components inside the cutout area—that's the point of the cutout. But you also need to leave clearance around the cutout for manufacturing tolerances. Typically, keep copper and components at least 0.3mm to 0.5mm away from the cutout edge.

Tab Routing vs. Punching

Internal cutouts are typically created with tab routing—a CNC router mills out the opening. For very high volume, custom dies can punch the cutouts, but this adds tooling cost and is only economical for large runs.

Plating Considerations

If the cutout is intended for electrical connection (like a mounting hole with plating), it needs to be designed as a plated cutout. This requires special consideration because the plating process expects holes, not arbitrary shapes. Most manufacturers can plate simple cutouts, but complex shapes may not be platable.

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Manufacturing Challenges with Double Cutouts

From the manufacturer's perspective, double cutouts add complexity. Here's what happens on the production floor:

Material removal. Cutting internal voids takes time. Each cutout adds to the routing time, which increases cost.

Deburring. After routing, the cutout edges need to be deburred to remove sharp fibers and copper burrs. This is an extra step.

Handling during assembly. Boards with large cutouts can be flimsy. If the cutouts remove too much material, the board might flex during solder paste printing or component placement, causing misalignment.

Panelization. If your board has internal cutouts, it might need more support tabs to hold it in the panel during assembly. These tabs get routed away later, but they need to be there to keep the board stable.

Bridge integrity. The material between cutouts is especially vulnerable. If the bridge is too thin, it can crack during depaneling or even during normal handling.

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Double Cutouts in Flexible Circuits

Flexible circuits add another layer of complexity. Polyimide flex materials are less rigid than FR-4, so cutouts can make the board even more delicate.

For flex circuits, cutouts are usually laser cut rather than routed. Lasers provide cleaner edges and don't stress the material the way a router bit does. However, laser cutting is slower and adds cost.

When designing cutouts for flex circuits:

• Use larger corner radii to prevent tearing

• Avoid narrow bridges between cutouts

• Consider adding stiffeners near cutouts if the area will be handled

• Remember that flex circuits are often populated with components after cutouts are formed

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Common Double Cutout Problems (And How to Avoid Them)

Problem: Bridge Breaks During Depaneling

The thin strip of material between two cutouts snaps when the board is separated from the panel.

Prevention: Increase bridge width. If the design allows, combine the two cutouts into one larger opening. Use rounded corners to reduce stress concentration.

Problem: Board Warps After Cutouts

The board bends or twists after cutouts are routed, especially if the cutouts are asymmetrical.

Prevention: Keep cutout placement balanced. If you have cutouts on one side of the board, consider adding dummy features on the opposite side to balance copper distribution.

Problem: Cracking at Cutout Corners

Cracks start at sharp internal corners and propagate through the board.

Prevention: Always use rounded corners. A radius of 0.5mm to 1mm is a good starting point. The larger the radius, the less stress concentration.

Problem: Cutouts Too Close to Board Edge

The board cracks from the cutout to the edge during handling or assembly.

Prevention: Keep cutouts at least 1.5mm to 2mm from the board edge, depending on board thickness.

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How Kaboer Handles Double Cutouts

At Kaboer, we've been manufacturing custom PCBs since 2009. Based in Shenzhen with our own PCBA factory, we understand that sometimes your design needs more than a simple rectangle. We've seen every kind of cutout—simple, complex, multiple, and everything in between.

What we offer:

• Rigid PCBs with complex internal cutouts, from simple slots to intricate shapes

• Flexible circuits where laser-cut cutouts preserve material integrity

• Rigid-flex boards where cutouts may span both rigid and flexible sections

• Design review: Our engineers check bridge widths, distances from board edges, and corner radii before production

• DFM feedback: We'll flag potential issues before they become expensive problems

• Fast prototyping: Need to validate a complex cutout design? We can get you prototypes quickly

Our process:

1. We review your design, paying special attention to cutout placement and bridge integrity

2. We check that bridge widths meet manufacturing requirements

3. We verify that cutouts are at safe distances from board edges and other features

4. We confirm that corner radii are adequate for your board material

5. We flag any potential issues before production starts

We work with the full range of boards—rigid, flexible, rigid-flex, HDI—and we understand that cutout requirements change with the board type.

If you're designing a board with double cutouts and want to make sure it's manufacturable, send us your requirements or Gerber files. We'll review your design, give you honest feedback, and get back to you with a quote. We've been at this for over 15 years, and we believe the best partnerships start with straightforward conversations.

And if you're ever in Shenzhen, we'd be happy to show you around our factory and walk you through how we handle complex cutouts on both rigid and flexible boards.