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What will I choose? A guide for Vias in PCB design

How much do you really know about roads, one of the basic components of PCB design?

Vias are a basic element of PCB design. But before you can decide whether to use buried, blind or through vas, you must understand what they really are and what they do for your board.

This article will serve as a guide through basic information.

Via Basics

What is a va?

The Vias are used to electrically and thermally join traces, pads and polygons in different layers of a PCB. Vias are copper cylinders that are placed or formed in holes that have been drilled in a PCB.

What is a Via Pad?

The Vias require a minimum amount of copper in a layer for proper connection, so that, in most cases, a pad (copper circle called an annular ring) is placed at the end of narrow traces to increase the available material for a connection.

What is an antipad?

Around the pad goes there is a copper-free area known as "antipad," which roams the pad of the surrounding copper.

Two traces (left) that belong to the same network are in adjacent layers of a PCB. The traces expand in the connection area with the va pads and join with a va (right).

How are the roads made?

Unless you are at home with a DIY through a rivet gun on a 2-layer board, the vases are created during the PCB manufacturing process.

Briefly, the holes are drilled through copper pads on the PCB, a chemical is placed in the hole to dissolve the epoxy in the inner layers to further expose the copper pads of the inner layer. Finally, a little copper is placed in the hole with electroplating.

To see an animation of how the tables are made (including valas), watch this video:

Most PCB manufacturers will place slaughter vessels on their PCBs in a section of the production board. Then the vas are cut and the sections are examined to determine the effectiveness of the electroplating process.

A cross section of a va. Image used courtesy of Data Respons

When should I use Vias?

Vias provides a path for electrical and thermal energy to move from one layer to another on its board. In general, the more energy dissipates an IC, the more you must have to connect your thermal pad to the underlying copper layers that can distribute the thermal energy.

A thermal pad for the QFN IC has 64 vas! Image used courtesy of Bittele Electronics Inc.

For parts of your circuit that carry energy, or fast signals, use several vas to connect layer by layer. In general, it is better to have several smaller ones than one large one. The design option reduces the inductance and provides additional routes for the current in case one of the vas fails.

Road types

There are three basic types of vas: