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Tented Via: Advantages and Disadvantages

Published Date
Author Cadence PCB Solutions

Key Takeaways

  • The term "tented via" refers to a via covered by a solder mask or similar material, usually on both sides of the PCB. In this article, we examine the advantages and disadvantages of tenting vias.

  • PCB design and manufacturing use several types of via-tenting techniques, including complete and partial tenting or tenting with Coverlay or other material.

  • The right PCB design software is crucial to successfully incorporating via tenting into your board.

Knowing your vias and pads makes the decision about using tented vias easier

Knowing your vias and pads makes the decision about using tented vias easier.

The term "tented via" refers to a via covered by a solder mask or similar material, usually on both sides of the PCB. Vias are plated holes that allow signals to pass between layers of a PCB. Tenting a via involves applying a solder mask to its pad and hole, covering it with a nonconductive material. A tented via has advantages and disadvantages, as shown in the table below. These should be carefully considered based on the specific requirements and constraints of the PCB design project.

Tented Via: Advantages and Disadvantages

Advantages

Disadvantages

Provides electrical isolation between nets

Difficult to probe or repair connections

Protects via from environmental factors

Impedes heat transfer if thermal dissipation is needed

Reduces risk of solder bridging

Potentially increases cost (depending on manufacturer)

Prevents accidental short circuits

Can trap air or gas during assembly, affecting reliability

Types of Tented Via Techniques

PCB design and manufacturing use several types of via-tenting techniques. They can be classified into the following types:

Types of Via Tenting Techniques

Complete Tenting

Using this technique, the top and bottom sides of the PCB are covered with a solder mask, enclosing the via completely and providing maximum protection and isolation for the via.

Partial Tenting

When partial tenting is used, only one side of the PCB is covered with a solder mask, leaving the other side exposed, which can be useful when thermal dissipation is needed through the via or for accessibility.

Tenting with Coverlay

This technique involves covering the via with Coverlay, a flexible dielectric material, instead of a solder mask; rigid-flex or flexible PCBs are commonly made of this material.

Tenting with Cap Plugging

This method involves tenting the via with a solder mask and applying a non-conductive material, such as resin or epoxy, to completely seal it, providing additional protection against environmental factors and mechanical damage.

Tenting with Copper Fill

When tenting a via with a solder mask, copper fill can be used instead of leaving the via entirely hollow, which provides additional structural integrity and can help improve the thermal performance of the via.

Via Plug

Instead of tenting the via with a solder mask, conductive or non-conductive plugs can be inserted into the via to seal it; this method is typically used for high-density interconnect PCBs where space is limited.

The choice of tenting technique depends on the specific requirements of the PCB design, such as thermal management, signal integrity, and manufacturing constraints.

How To Incorporate Via Tenting Into Your PCB

So you've weighed the advantages and disadvantages and decided which via tenting technique is the best option for your PCB. What should you do next? You should follow these steps:

PCB Design Software

Using PCB design software, specify which vias you want to tent. Most PCB design software tools allow you to determine whether vias should be tented or left open.

Design Specifications

In your PCB design specifications, you should explicitly state that certain vias should be tented. Fabrication notes or specifications provided to PCB manufacturers usually include this information.

Gerber Files

Once your PCB design is complete, generate Gerber files, including the solder mask layers that specify where a solder mask should be applied. Solder mask layers in Gerber files (usually titled "top solder mask" and "bottom solder mask") indicate which vias to tent. Pads or shapes are typically placed over the via in the solder mask layers to indicate this information.

PCB Manufacturing

As part of the manufacturing process, the manufacturer will use Gerber files and specifications to fabricate the PCB, including applying solder mask to specified vias. Once the PCB is manufactured, inspect it to ensure the vias are tented according to your specifications.

Following these steps and communicating your tenting requirements clearly to the PCB manufacturer will ensure that the vias on your PCB are properly tented.

Incorporate Tented Vias Using Cadence Tools

With Cadence's suite of design tools, you can incorporate tented vias in your layout and analysis processes. You can be confident that our tools will produce a PCB that conforms to your vision and is easy to implement. OrCAD PCB Designer is a strong option for layout with respect to design for manufacturing. 

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