PCB Drill-Comprehensive Guide to PCB Drilling Holes

Introduction to PCB Drill Technology

In modern electronics, printed circuit boards (PCBs) are the backbone of countless electronic devices we rely on daily. PCBs are intricate assemblies that connect electronic components and provide the necessary pathways for smooth data transmission and power distribution. At the heart of these complex boards lies the essential PCB drill technology, which creates precise holes required for various components and interconnections.

PCB drilling is the process of creating precise holes in a PCB. These holes are essential for mounting electronic components onto the board and establishing electrical connections between different layers of the PCB. These holes are mounting points for electronic components like resistors, capacitors, and integrated circuits. Additionally, they enable the creation of vias, which allow pathways to be established between different layers of the PCB, enhancing its functionality and efficiency.

The process of PCB drilling demands meticulous precision, as even the slightest deviation from the desired measurements can lead to the failure of the entire circuitry. As technology advances, the demand for smaller and denser PCBs rises, driving the need for more sophisticated drilling techniques and tools.

The significance of PCB drilling in the manufacturing process cannot be understated. It is one of the primary stages in PCB fabrication, and its accuracy and efficiency directly impact the overall quality of the final product. The drilled holes form the foundation for the entire circuit, making it a critical step in the PCB assembly process.

PCB Drilling
PCB Drilling


PCB drilling is part of the larger PCB production workflow, which includes several other key stages, such as designing the PCB layout, transferring the design to the board substrate, etching the copper layers to create conductive pathways, and soldering components onto the board.

The demand for PCBs with higher complexity and miniaturization has surged in recent years. This trend has spurred advancements in drilling technology, paving the way for automated drilling machines, laser drilling systems, and other innovative solutions. These developments have improved the precision and speed of the drilling process and made it more cost-effective for PCB manufacturers.

In this comprehensive article on PCB drilling holes, we will explore the different types of PCB drill holes, delve into the drilling processes for each type, and provide a step-by-step guide to drilling PCBs effectively. We will also discuss the crucial considerations in drill selection and highlight common drilling challenges and their solutions.


Types of PCB Drill Holes

In the intricate printed circuit board fabrication world, drill holes play a pivotal role in creating the foundation for seamless electronic connections. These drill holes come in different types, each serving specific purposes in the overall design and functionality of the PCB. Understanding the differences between these hole types is crucial for designing and fabricating printed circuit boards that meet specific requirements.

Non-Plated Through Holes

Non-plated through holes penetrate the PCB from one side to the other without any conductive material lining the hole walls. These holes are primarily used to mechanically anchor components on the PCB’s surface and provide interconnections between different board layers.

Non-plated through holes
Non-plated through holes


The drilling process for non-plated holes involves creating pathways for electrical connections or mounting pins. Once the components are placed in these holes, soldering establishes the electrical connection between the component lead and the surrounding copper pad on the PCB surface. Non-plated through holes are widely used for single-layer PCBs and applications where no interconnection between the inner layers is required. However, they are unsuitable for complex multilayer boards with multiple connections.

Plated Through Holes

Plated-through holes (PTH) pass through the entire PCB and have conductive material lining the walls. This conductive lining, typically made of copper, forms a continuous pathway connecting different PCB layers, allowing electrical signals and power to flow seamlessly between them.

Fabricating plated through holes involves an additional step called “electroplating.” After the holes are drilled, the PCB is immersed in an electrolytic bath, and a thin layer of copper is deposited on the walls of the holes, creating the conductive pathway. Plated-through holes offer significant advantages in complex multilayer PCB designs, as they create intricate interconnections between circuit layers. These holes are vital for the functionality and structural integrity of the board, as they provide a reliable means of connecting components across multiple layers.

Plated through holes
Plated through holes


Plated-through holes have become a standard practice in modern electronics manufacturing because they enhance the PCB’s reliability and performance. They play a vital role in ensuring the proper functioning of high-speed and high-density electronic devices.

PCB Drilling Process for Different Drill Holes

In the fast-paced world of electronics manufacturing, precision, and efficiency are paramount when it comes to PCB drilling. The drilling process lays the foundation for seamless electronic connections, making it a critical step in the fabrication journey. Over the years, technological advancements have given rise to various PCB drilling methods, each tailored to suit different drill holes.

Automated Drilling

Automated drilling, or CNC (Computer Numerical Control), is a popular method used in modern PCB manufacturing facilities. This process involves using sophisticated machinery controlled by computer programs to drill holes with exceptional accuracy and speed.

The automated drilling machines have a drill head that holds multiple drill bits of varying sizes. The computer program reads the PCB design data and precisely positions the drill head over the designated hole locations. The machine then automatically changes drill bits as needed and proceeds to drill holes at the specified depths and diameters.

Automated drilling
Automated drilling


Automated drilling offers several advantages, including high precision, reduced human error, and the ability to handle large-scale PCB production with consistency. It is particularly well-suited for non-plated through holes in single-layer or double-layer PCBs.

Mill Machine Drilling

Mill machine drilling, also known as mechanical drilling, is a traditional approach to PCB drilling that predates automated methods. In this process, a drill bit is manually attached to a milling machine spindle, and the operator guides the drill to create holes in the PCB.

While mill machine drilling is less automated than CNC drilling, it remains a viable option for small-scale PCB production or when dealing with specialized materials. It allows for greater flexibility in drilling unconventional hole sizes and shapes, making it ideal for prototyping and custom PCB fabrication.

Mill machine drilling
Mill machine drilling


Laser Drilling

Laser drilling is a cutting-edge PCB drilling method that utilizes the power of lasers to create precise holes on the board’s surface. This non-contact process involves directing a high-intensity laser beam onto the PCB material, which vaporizes and ablates the material, forming the desired holes. Laser drilling offers unparalleled precision and speed, making it ideal for drilling small-diameter holes in multi-layer PCBs. Its non-mechanical nature eliminates the risk of drill bit wear and allows for intricate drilling patterns, such as micro vias.

While laser drilling is highly efficient, it is more commonly used for creating plates through holes and micro vias, as the process can be expensive compared to traditional drilling methods.

Laser drilling working
Laser drilling working


Specific PCB Drilling Process Options for Each Hole Type:

Automated Drilling for NPTH

Automated drilling machines equipped with standard drill bits are ideal for creating non-plated holes in PCBs. The CNC-controlled process ensures precise hole alignment, making it suitable for high-volume production where consistency is critical.

Mill Machine Drilling for NPTH

Mill machines with adjustable settings can be employed for drilling non-plated holes for small-scale production or prototyping. The operator can manually set the machine to achieve specific hole diameters and positions per the design requirements.

Laser Drilling for Plated Through Holes

Laser drilling is the preferred method to create plated holes in multi-layer PCBs due to its high precision and ability to handle intricate designs. Laser systems can create vias with varying diameters and depths, offering unparalleled control over the drilling process.

Step-by-step Guide to Drilling PCBs

Drilling holes in a printed circuit board requires precision and careful execution to ensure a flawless result. Whether you are a seasoned electronics enthusiast or a beginner in PCB fabrication, this step-by-step guide will walk you through the essential aspects of drilling PCBs confidently and accurately.

Drilling Pilot Holes

Before drilling the final holes, it’s essential to create pilot holes. These small guide holes act as markers to ensure the drill bit follows the intended path accurately. To do this, use a tiny drill bit with a diameter of approximately 0.5 mm (or smaller) to create pilot holes at the center points of all the desired drilling locations.

Drilling at an Angle with a Straight PCB Drill Bit

Drill the PCB at a slight angle rather than perpendicular to the board’s surface for best results. This angle helps to prevent drill bits from wandering off the intended path. Carefully position the drill bit at the pilot hole and apply gentle pressure as you start drilling at a low speed. Gradually increase the speed as the drill bit gains traction.

Using the Correct-sized Drill Bit

Selecting the correct drill bit size is critical to achieving precise hole diameters. Refer to your PCB design or drilling guide to determine the drill bit size for each hole type. Avoid using excessive force when drilling, as this may lead to PCB delamination or inaccuracies in hole sizes.

Selecting Drill Bit Speed and Power

Your drill’s speed and power settings play a significant role in the drilling process. For fiberglass-based PCBs, a 10,000 to 20,000 RPM speed is typically suitable. However, softer materials may require lower speeds to avoid damage. High-speed drilling may generate excess heat, potentially damaging the PCB and drill bits. Opt for lower speeds when drilling PCBs to prevent overheating and ensure clean hole edges.

Utilizing a Drill Press

A drill press is valuable for achieving consistent and accurate drilling results. It provides stable support for the PCB, minimizing the risk of misalignment or uneven drilling. Secure the PCB on the drill press platform and align the drill bit with the pilot holes before drilling.

The Operation of a Drill Press for PCBs

Gently lower the drill bit onto the PCB surface, allowing it to enter the pilot hole. Use smooth, steady downward pressure to avoid chipping or splintering the PCB material. Let the drill bit work; excessive force can lead to rough holes.

Drilling PCBs with a Drill Press

Carefully position the drill bit over the pilot hole, aligning it with the desired drilling location. Lower the drill bit gently until it touches the PCB’s surface. Maintain a steady and controlled downward pressure to create the hole. Once the hole is drilled, lift the drill bit slowly to avoid any damage to the hole’s edges.

Safety Precautions During Drilling

Drilling PCBs involve some risks, so taking appropriate safety measures is crucial. Wear safety goggles to protect your eyes from debris, and consider using a dust mask to prevent inhaling particles. Work in a well-ventilated area to disperse any fumes generated during drilling. Additionally, avoid wearing loose clothing or jewelry that may get caught in the drill press.

Cleaning the PCB after Drilling

After drilling, use a soft brush or compressed air to remove debris or dust from the PCB’s surface and drilled holes. This cleaning process ensures the holes remain unobstructed for the following stages of PCB assembly.

Applying Solder to Drilled Holes

If you have plated through holes, the next step is to apply solder to establish electrical connections between different layers of the PCB. Prepare the PCB by thoroughly cleaning and selling the components per your design specifications.

Step-by-step guide
Step-by-step guide

Considerations for the Proper Drill Selection in PCB Drilling

Selecting the right drill for PCB drilling is a critical aspect that significantly impacts the quality and functionality of the final printed circuit board. The choice of drill diameter and the effective utilization of blind and buried vias play crucial roles in ensuring the success of your PCB fabrication. 

Importance of Selecting the Right Drill Diameter

The drill diameter is one of the most fundamental factors when drilling holes in a PCB. Choosing the correct drill diameter ensures that the holes accommodate electronic components perfectly and achieve optimal electrical connections. 

Match the Drill Diameter with Component Lead Size:

When selecting a drill diameter, it’s crucial to match it with the size of the component leads that will pass through the holes. A drill diameter that is too small can cause difficulty in inserting the leads, while a too-large diameter may lead to loose or unstable connections.

Maintain Adequate Annular Ring

The annular ring is the copper pad surrounding the drilled hole. It provides the surface for soldering the component leads. To ensure reliable soldering, it’s essential to maintain an adequate annular ring. This means the distance between the drilled hole’s edge and the copper pad’s edge should be sufficient to provide a robust solder joint.

Consider Tolerance and Accuracy

Drilling machines may have a tolerance for hole size. Ensure that the selected drill diameter falls within the acceptable range to achieve accurate and consistent hole dimensions.

Account for Material Thickness

Consider the thickness of the PCB material when choosing the drill diameter. The drill should be capable of penetrating the entire thickness without causing excessive stress or delamination.

Utilizing Blind and Buried Vias Effectively

Blind and buried vias are specialized drilling techniques used in multi-layer PCBs to achieve higher circuit density and enhance signal integrity. Understanding their advantages and limitations can significantly impact the overall performance of your PCB:

Blind Vias

Blind vias are drilled from the outer layer of the PCB and terminate on an internal layer without passing through the entire board. They enable connections between the surface and one or more inner layers, reducing the number of drilled holes that extend through the entire PCB.

Buried Vias

Unlike blind vias, buried vias are entirely contained within the inner layers of the PCB and do not extend to the outer layers. They provide interconnections between multiple inner layers, offering greater flexibility in routing traces and reducing electromagnetic interference.

Blind vs. Buried Vias
Blind vs. Buried Vias


Effectively utilizing blind and buried vias requires careful planning during the PCB design phase. Since these vias are not visible from the outer surface, accurate drill alignment is critical during manufacturing. Selecting the suitable drill diameter and utilizing blind and buried vias effectively are vital aspects of PCB drilling. Precision in drill diameter ensures proper component fit and robust solder connections, while the strategic use of blind and buried vias optimizes PCB layouts in advanced designs


Common Drilling Disasters and Their Solutions

While PCB drilling is a crucial step in the fabrication process, it can be prone to various challenges that may lead to drilling disasters. These mishaps can significantly impact the quality and functionality of the printed circuit board. 

Drill Breakage

One of the most common drilling disasters is drill breakage. This can occur due to excessive drilling speed, improper feed rate, or using a dull drill bit. A broken drill can damage the PCB and may require halting the drilling process.

Solution: Always use sharp and well-maintained drill bits to prevent drill breakage. Adjust the drilling speed and feed rate according to the material and drill bit size. If a drill breaks during the drilling process, immediately stop the machine and safely remove any broken fragments before continuing.

Misalignment of Holes

Drill bit misalignment can lead to holes being drilled off-center or in the wrong location, compromising the integrity of the PCB design. Misalignment can be caused by inaccuracies in the drilling machine setup or improper handling.

Solution: Ensure the drill press or automated drilling machine is correctly calibrated and aligned before drilling. Double-check the position of the PCB and verify the drill bit’s alignment with the pilot holes before proceeding with the drilling process.

Delamination and Chipping

Delamination and chipping of the PCB material can occur when drilling through multiple layers or when using inappropriate drill settings. Delamination refers to separating layers within the PCB while chipping involves fracturing the board’s surface.

Solution: Use the appropriate drill speed and feed rate for the specific PCB material. Adjust the drilling parameters according to the board thickness and type to minimize the risk of delamination and chipping.

Copper Burrs and Tear-outs

Drilling can sometimes cause copper burrs or tear-outs around the drilled holes. These burrs can lead to short circuits or poor soldering connections.

Solution: Use high-quality drill bits and reduce the drilling speed when working with sensitive materials. After drilling, inspect the PCB for any copper burrs or tear-outs and remove them carefully using a deburring tool or a fine file.

Inadequate Hole Size

Drilling holes with incorrect diameters can be a major disaster, especially if components need to fit correctly or the annular ring is insufficient for reliable soldering.

Solution: Double-check the drill bit size against the PCB design data and ensure the drill bits used are within the specified tolerance. Regularly calibrate and measure the drill bits to maintain accuracy.



In this comprehensive article on PCB drilling, we explored the vital aspects of PCB fabrication. From the significance of PCB drilling to the different types of drill holes and drilling processes, we gained valuable insights into electronics manufacturing.

Understanding the role of non-plated and plated-through holes is crucial for creating reliable electrical connections. We discussed automated drilling, mill machine drilling, and laser drilling as effective methods for achieving precise holes. Our step-by-step guide highlighted the importance of pilot holes, correct-sized drill bits, and drill press utilization for stability. Safety precautions were emphasized for a secure drilling process.

Proper drill selection, including the suitable diameter, was stressed to ensure optimal component accommodation and soldering. We also explored the advantages of blind and buried vias in enhancing circuit density and signal integrity. Finally, we addressed common drilling disasters and their solutions, equipping you with the know-how to confidently produce high-quality PCBs.

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