Non-Plated Through Hole (N-PTH)

When you look at the printed circuit board in your hands, you may notice the presence of some holes on the board. Don’t worry; this isn’t a case of cost-cutting by the manufacturer or a result of rodent interference. Instead, it’s intentionally designed this way. According to design purposes, these holes can be broadly categorized as PTH and N-PTH. In this TechSparks article, we will focus on N-PTH holes in PCB, helping you understand their concept, significance, and formation process.

Further Reading: What does PTH mean in PCB?

Non-plated through hole

Table of Contents

What is N-PTH in PCB

N-PTH is non-plated through hole. To help you understand its meaning more clearly, we will dismantle and explain this word:

“Plating” refers to the process of placing a PCB in a solution of metal ions and depositing metal ions at specified locations through the application of an electric current.

“Through Hole” refers to a hole that passes through the entire PCB.

Therefore, the concept of N-PTH is quite straightforward—it refers to a through hole in a PCB that does not have a metal layer on its walls.

As known, a printed circuit board is formed through a lamination process involving multiple layers. Its purpose is to serve as a carrier for components and provide electrical connections. In circuits, the pins of components are inserted into these holes, and these metal pins make contact with copper foils to facilitate the transfer of current. While this seems reasonable, there is an overlooked issue: the substrate layer and copper foil layer alternate in the stack, and the substrate material is insulating. This means that certain parts of the component pins come into contact with insulating material, leading to compromised electrical performance. To address this issue, electroplating is performed to ensure that the pins consistently make contact with metal.

However, according to the definition of N-PTH, it is evidently disadvantageous for mounting components. So, what is the significance of N-PTH hole?

Significance of N-PTH

Upon closer inspection, you will notice that, comparatively, N-PTH holes tend to be larger than PTH holes (though not universally). This is primarily because many N-PTH holes serve as fixing points for mechanical components. Mechanical components typically have larger dimensions compared to electronic components and are commonly used for applications such as mounting screws, brackets, and other voluminous mechanical elements.

Comparison chart of PTH and NPTH

On the other hand, N-PTH holes play a crucial role in assembly by serving as alignment guides. Even when the PCB is fixed in a certain position and then transported to the assembly area, it streamlines the entire manufacturing process, enhancing efficiency. Additionally, in earlier stages of SMT assembly, N-PTH holes were used to secure the PCB, although nowadays, clamping methods are more commonly employed for fixation.

Lastly, N-PTH holes contributes to some extent in improving electrical performance. Specifically, it maintains electrical isolation between two circuits, reducing the possibility of signal interference. Furthermore, it provides an additional heat dissipation path, aiding in lowering temperatures for certain high-power components.

Formation Process of N-PTH Holes

The formation process of N-PTH holes is considerably simpler since plating is not required. During the design phase, designers mark the positions of these holes based on project requirements. Subsequently, manufacturers use your design files to proceed with production.

Typically, the hole drilling process takes place after lamination, employing techniques such as CNC or laser drilling. Given that N-PTH holes do not necessitate the installation of electronic components, their requirements are significantly lower compared to PTH holes. To ensure cost-effectiveness for your project, it is recommended to use CNC.

Formation Process of N-PTH Holes

Following the completion of drilling, the PCB surface needs to be cleaned to remove debris, preventing any adverse effects on assembly quality. For high-value projects, additional treatments such as corrosion resistance or enhanced mechanical strength may be applied to the N-PTH holes. Regardless, once the N-PTH holes are formed, a final inspection is conducted to confirm their dimensions and positions align with the design specifications.

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