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Aspect Ratio and Thermal Expansion of Through-Hole Vias

Thermal Expansion of Through-Hole Vias

The aspect ratio of a PCB via plays an important role in its function, signal integrity, manufacturability, and reliability. Aspect ratios determine the size of holes drilled in different layers and impact etching, plating, and mechanical stress issues. Aspect ratios can also influence the quality of a PCB’s solder joints. This article will explore how the aspect ratio of a through-hole or microvia impacts its performance and how to handle thermal expansion.

The term “aspect ratio” refers to the ratio of two dimensions: the width of a hole (drill diameter) and its height (via length or copper weight). PCB manufacturers have limitations on what via aspect ratio they can drill, so it’s important to double-check with your manufacturer’s specifications before designing your board.

Depending on the design and layout of a PCB, there are several types of vias that can be used. The main types include blind, buried, and through-hole vias. Blind vias establish connections between the outer layer and inner layers without extending to any other layer, while buried vias connect the inner layers with each other without extending into the outer layers. Through-hole vias connect the inner layers to components on the board, and are typically plated in two stages. The first step is to fill the via with conductive epoxy, followed by the second step of plating the through-hole.

Aspect Ratio and Thermal Expansion of Through-Hole Vias

As the PCB temperature rises, the copper in the via expands. This expansion can cause the metallization in the through-hole to crack, resulting in poor solder joints with the component leads. This problem is more common with smaller vias, which is why it’s a good idea to use larger ones when possible.

The size of a via’s annular ring also affects its performance. A smaller annular ring can weaken the joint with the component lead, while a larger one will strengthen it. It’s also important to consider the thickness of the component pads when choosing an annular ring size. The pad’s thickness must be able to accommodate the via’s length and the plated through-hole.

Larger vias are also better able to handle the effects of thermal cycling, as they have greater mechanical strength and conductivity. This is particularly true for buried and blind vias, which are more susceptible to damage due to their long length.

“Via aspect ratio” refers to a fundamental concept in various visual mediums, including photography, film, and digital content creation. It represents the proportional relationship between an image or video’s width and height. Understanding and effectively utilizing aspect ratios is crucial for achieving desired visual effects, conveying specific moods, and ensuring compatibility across different platforms.

JHD is a top-tier PCB manufacturer with excellent drilling capabilities and precise Aspect Ratio drilling. Their experienced team and advanced equipment enable them to meet even the most complex Aspect Ratio requirements. In addition, they adhere to strict industry standards and guidelines to ensure high-quality products. For more information on their PCB manufacturing services, contact them today.


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