How to cut a slot in a PCB prototype board?

27 May, 2022

By ren

What are PCB Slot and Cut-outs PCB prototype?

How to cut a slot in a PCB prototype board? The existence of slots on a circuit board provides several advantages. The impact of circuit board slots cannot be overstated. PCB slots are offered in several varieties. Therefore, it is essential to have a thorough understanding of these areas.

What exactly is a PCB Slot?

A PCB slot is a hole on the circuit board that is too large to be drill file using conventional techniques. Manufacturers must use a routing bit to create these holes during PCB construction. A slot PCB may be either plated or non plated.

How to cut a slot in a PCB prototype board?

Variety of PCB Slots

The two most common kinds of PCB slots are plated slots and unplated slots.

Plated bore

A plated slot in PCB fabrication is copper-plated. The plated slot does not have a round form. A plated PCB slot has copper on both the bottom and the top. This hole is perfect for electrical hookups. Slots with plated through-holes are optimal for component packing. This sort of PCB slot is always included on multilayer PCBs.

There are a variety of component kinds for circuit board assembly in PCB fabrication. The majority of through-hole component designs include circular holes that can accommodate square or round leads. Most through-hole assemblies conform to this design. Several components, however, have rectangular leads that do not fit into square or round holes. Consequently, a plated slot is preferable.

As the size of the pins grows, large blade-style connections must have plate through slots. When the components are tiny, manufacturers may use circular holes with rectangular pins. However, round holes need more room on the circuit board. Plated slots are perfect for designs with limited space.

Non-plated slots

The non-plated slot has a larger hole than the copper size of the pad. Occasionally, there may be no copper. In a slot that is not coated, the copper pad overlaps. The slot is drilled by the manufacturer using the electroless copper technique.

PCB Slot Definition on Circuit Boards

What is a slot on a circuit board or how to cut a slot in a PCB prototype board? If your PCB design has slots, you should place them in the Gerber mechanical layer. This layer is the most secure approach to displaying the circuit board's slots and profile. There are two approaches to this:

  • Employ flashes or draws with the rightmost round edge of the slot

Draw the slots using a 0.50mm line. The line aids in analyzing the clearance between the copper and the edge of the circuit board.

In the Gerber file, you may merge the specification of the slots with the PCB outline. The mechanical layer must be positioned between the copper layers. Nonetheless, verify that the copper layer includes the PCB outline. If no mechanical layer is available, it may be necessary to use an alternative drill layer.

What is the most diminutive PCB slot and How to cut a slot in a PCB prototype board?

Rigid-flex and flex circuits have 0.50 mm slots. The minim slot length is 1 mm. Because of rigid-flex and stiff PCB thickness. So, use mechanical NC milling to make slots. Typical flex circuit thicknesses. Lasers can carve these slots.

Longer slots are straighter. Slot length is double its breadth. A 0.60mm slot will be 1.20mm long.

Slots Milling

How to cut a slot in a PCB prototype board? The slots are milled out of the hard PCB material by the manufacturer. The PCB manufacturing process then utilizes an NC grooving cutter bit. This cutter operates similarly to a CNC machine. In addition, the inner corners of the cuts will include along their edges. In enclosure design, you must be mindful of this factor.

The inside corner's smallest radius is 0.50 mm. The tiniest tool for routing circuit boards is one millimetre wide. Milling holes on a circuit board creates air gaps for voltage isolation.

Using Eagle to Create Slot PCB

You may question whether Eagle supports the creation of slots. Slotted holes are common on printed circuit boards (PCBs) because components must manage growing currents. Numerous components have broad pins. This is because a component with a broad pin has more mechanical integrity.

Manufacturers may design slot PCBs. It is essential to utilize a through-hole pad with a diameter that corresponds to your slot. The Oblong pad is well suited for this procedure.

Draw the slots

To create slotted holes, draw the slot outlines. You may alter this procedure. Using the dimension layer is an excellent method for doing this. This approach has limitations, though. The autorouter is unable to access the inside of the pad. Consequently, there will be dimension inaccuracies.

Ensure that the pad's drill size fits inside the PCB contour of the slot. This will aid in preventing misunderstanding and guarantee a better outcome. The PCB maker will mill the region within the board's outline.

PCB design distinctions between plated and non plated slots

How to cut a slot in a PCB prototype board? A copper sheet is etched during the PCB construction process. After placing this sheet on a substrate, holes are drilled into it. These spaces are non-conductive before plating. Electroless deposition is used by manufacturers for PCBs with several copper layers.

However, designers must be aware that not all slots need plating. Therefore, designers must adhere to the manufacturer's guidelines to determine which slot will be plated. Sometimes, designers anticipate certain circuit board characteristics. In the end, they get a new board. Mounting slots are one example.

For instance, if your design relies on a certain slot being plated, there may be complications. After getting the board, you find that the slot has not been cut. Therefore, we shall highlight the distinction between plated and non plated slots.

How to determine if a slot is coated

Occasionally, certain PCB holes are non-plated for mechanical or electrical reasons. A non-plated slot is any slot that does not fulfil the requirements for a plated slot. A slot PCB is non-plated when the hole is larger than the copper size of the pad. Moreover, when the copper of the pad overlaps the hole and is larger than the hole. Nevertheless, there is a 6 mm clearance between the hole and the copper. These circumstances satisfy the criteria for an non-plated slot.

Slots With and Without a Plating Finish

  • Milling holes produce air gaps on circuit boards for voltage isolation

High voltages may cause transient electrical arcs between traces on a circuit board. Repetitive electrical sparks may lead to the carbonation of PCBs. This may eventually produce a short circuit. PCB designers incorporate a milling PCB slot between suspicious traces as a consequence.

  • Slots with plating are suited for components with square or rectangular leads

These holes accommodate square or rectangular leads as opposed to rounder ones. Slots have a smaller footprint than huge holes. This is because the area between the hole's wall and the lead must be sufficiently filled with solder.

Guidelines for Plated Slots

  • There are numerous component types and footprints for PCB construction. Most through-hole component footprints are designed using round holes. The circular perforations may take either square or round leads. This design is appropriate for through-hole components. Nevertheless, many components utilize rectangular leads. These leads are not compatible with square or circular holes. It is preferable to implement a plated slot footprint.
  • When the component footprint allows greater space around the component leads, the circular hole arrangement is susceptible to faults. This may result in solder joint failure. This problem develops when more solder is used to fill the holes. Manufacturers get more worried when the size of pins grows. Therefore, big rectangular connections should use slotted plating rather than round holes.
  • Some manufacturers can make circular-holed rectangular pins. Round holes take up more space on the PCB. Large circular holes aren't ideal for dense-component architectures. Plating slots may help with restricted space designs.
  • When generating non-circular holes, PCB designers must consider many aspects. Non-circular hole design is easy. Plated slots are common in component footprints. Most PCB design programs allow oval or round holes. Several customers find slot holes in Gerber design layers.
  • Designers may make non-plated slot PCBs. They may label it Mechanical or NPTH in CAD. They may also use Board Outline Gerber. PCB slot criteria must be followed.

Considerations for Creating Plated Slots

To produce plated slots, designers must set a few EDA parameters. The majority of EDA tools enable designers to manually generate plated slots. Rather than inserting a typical pad, the designer specifies all parts of the hole in this instance. The three most crucial considerations for designing a plated slot are:

• The hole's contours

• The form of copper's topmost layer

• The form of copper's bottom layer

Plating distinguishes PCB slots from holes. They're drawn on the board outline layer. PCB makers interpret board outlines as cutting information. The manufacturer will route the PCB inside the outline. If the board outline layer has a shape, this will happen.

A plated slot is a drawn hole in a PCB's bottom and top pads. Designers must build footprint holes on the board outline layer. The slot will show in manufacturing files. Plated slots allow non-circular pins and leads.

Read more:


Slot PCB is an essential component of PCB layout. In PCB design, it is crucial to comprehend how these slots function. Both the plated and unplated slots have a purpose. In contrast, plated slots are more prevalent in the PCB sector.


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