Table of Contents
Every PCB contains vias, but not every via is treated the same. For instance, a manufacturer might leave the vias on a PCB exposed, cover them with solder mask, plug them with resin, or completely fill and plate them before proceeding to other steps. The different ways that vias are treated can have major impacts in solderability reliability, signal integrity, thermal performance, and even manufacturing cost.
Among the options that most often confuse people are via tenting, via plugging, and via filling. Although they all look to the same end of protecting the via or somehow modifying it, each process is quite different, and each is used in different circumstances. If choose a improper technique, you may end up with solder misting, voids under BGAs, contamination, or excess production cost.
Here, we will discuss via tenting vs plugging vs filling, describing how each process is done, their pros and cons, applications, and most important factors to remember when you have to decide on the treatment of a via for your PCB design.
Via Tenting vs Plugging vs Filling: Quick Comparison
All via treatments offer benefits and limitations, and this quick comparison indicates how they differ in the areas of performance, use, complexity to manufacture, and total cost.
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Parameter
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Via Tenting
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Via Plugging
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Via Filling
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Process
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Covered with solder mask
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Sealed with resin
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Completely filled and planarized
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Solder Wicking
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Reduces
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Prevents
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Eliminates
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Surface
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Uneven
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Nearly flat
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Completely flat
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BGA Support
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No
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Limited
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Yes
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Reliability
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Good
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Very Good
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Excellent
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Applications
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Standard PCBs
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Multilayer & industrial PCBs
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HDI & via-in-pad PCBs
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Complexity
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Low
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Medium
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High
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Cost
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Low
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Medium
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High
|
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Via tenting uses maximum speed and minimum cost because it just puts a solder mask over the via hole.
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Via plugging uses a special resin to fill the drilled hole before the solder mask is placed over the via hole, providing better protection against contamination and loss of solder.
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Via filling is the most advanced option. It fills the via completely with either resin or conductive material before being cured and planarized for a perfectly flat surface for use with via-in-pad designs and high-density electronic assemblies. However, it takes the longest time to manufacture and is the most expensive process.
What is Via?
A via is a small hole that has a layer of metal around it, and it allows electrical connections to happen between layers of printed circuit boards (PCB). Via allows power, signals and ground to cross different layers of a PCB without using wires outside of the PCB.
With the use of multi-layered PCBs, vias are an important aspect of designing compact circuits. Based on the application of a certain product, manufacturers will modify how vias are treated. By properly treating vias, one can prevent manufacturing problems, have quality solder, extend the life of the product, and aid in advanced technology such as fine-pitched BGAs and high-density interconnects (HDI).
What is Via Tenting in PCB?
Covering a via opening with a solder mask during PCB fabrication is referred to as via tenting. A solder mask provides a barrier to contamination of the via and minimises solder wicking when assembling the PCB. The hollow via remains, making via tenting one of the simplest and most cost-effective via treatments. Via tenting is primarily used in consumer electronics and standard designs that do not require high-density routing.
How It Affects PCB Assembly
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Reduces the complexity of applying the solder mask.
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Reduces the amount of solder that can wick back out of the via.
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Protects the via from contaminants such as dust and debris.
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May cause the solder mask to rupture in some cases during the fabrication process.
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Not recommended for vias used with via-in-pad designs.
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Not recommended for fine-pitch BGAs.
What is Via Plugging in PCB?
Via plugging involves filling the via hole with an epoxy-based non-conductive resin or another specialised plugging material before applying a solder mask. This is a more effective means of sealing the internal portion of the via as it provides increased protection from contamination, solder loss, and moisture as compared to tenting. Via Plugging also improves the consistency of soldering and is used throughout multilayer PCB designs that require a greater degree of reliability when assembled.
How It Affects PCB Assembly
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Significantly reduces the amount of solder that can be lost during the assembly process.
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Improves the yield of SMT assemblies.
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Prevents the entrapment of flux and other chemicals within the vias.
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Provides the via with improved moisture protection.
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Provides increased mechanical reliability.
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Appropriate for PCBs with mid-density assembly of components.
What is Via Filling in PCB?
Via filling completely fills the plated via to achieve a level surface by planarizing the filled area and creating a flat surface over the entire PCB. This process allows for the implementation of via-in-pad technology, making it suitable for use in HDI boards, fine-pitch BGA designs, or advanced electronic components. While this treatment is more costly than either tenting or plugging, via filling will deliver the greatest level of assembly quality, reliability, and mechanical strength.
How It Affects PCB Assembly
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Provides a reliable method for the use of vias in pads.
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Creates a completely flat PCB surface.
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Creates the highest quality of solder joints.
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Improves the accuracy of automated component placement.
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Eliminates the possibility of voids in solder joints near BGAs.
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Provides excellent mechanical and thermal properties.
When Should You Choose Each Via Treatment?
PCB’s via treatment should be chosen based on PCB design specifications, production cost constraints, assembly procedures during production and expected reliability from the final product.
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For example, tented vias are okay for normal consumer products, but plugging will provide better performance and reliability in industrial applications.
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For high-density interconnect (HDI) designs, fine-pitch ball grid array(BGA) devices and other high-performance electronic devices, where maximum reliability is essential. Filled vias become the best choice where manufacturing tolerances are critical.
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The correct method should be selected at the design phase to reduce production defects, improve assembly quality and ultimately reduce total manufacturing costs.
Recommended Selection Guide
Here’s the short description of the best fit and reason behind choosin the respective via’s.
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Design Requirement
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Best Choice
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Reason
|
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Low-cost PCB
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Via Tenting
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Lowest manufacturing cost
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Consumer Electronics
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Via Tenting
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Adequate protection for simple designs
|
|
Industrial Equipment
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Via Plugging
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Better reliability and contamination protection
|
|
Medium-density SMT
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Via Plugging
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Improved soldering consistency
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Fine-pitch BGA
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Via Filling
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Prevents solder defects
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HDI PCB
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Via Filling
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Supports via-in-pad routing
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High Reliability
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Via Filling
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Best mechanical strength
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|
Medical Devices
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Via Filling
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Maximum reliability
|
|
Aerospace Electronics
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Via Filling
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Excellent durability
|
|
High-Speed PCB
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Via Filling
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Better signal integrity and flat surface
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PCB Via Treatment Design Tips
Selecting improper via treatments during the manufacturing process can cause problems with both PCB assembly and the manufacturing of the PCBs. By avoiding these common mistakes, an increase in reliability, yield, and overall performance of PCB designs can be achieved.
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Using tented vias for fine-pitch BGA designs.
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Solder wicking should be considered when laying out the PCBs.
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Fill the vias even on low-cost boards.
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Always specify how the vias are to be treated on the fabrication drawings.
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Aviod assuming all manufacturers treat the vias in the same manner.
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Proper thermal performance should be considered when selecting the via treatment.
Conclusion
Choosing the proper via treatment involves considerations beyond design onlyit can much affect your PCB’s manufacturability, reliability, and overall cost.
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Via tenting is an economical solution for standard PCB designs.
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Via plugging is better for protection and solderability during assembly.
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Via filling gives the highest level of reliability, which makes it the best choice for HDI boards and fine-pitch BGA applications.
Deciding on the right method at the very beginning could save you from expensive production troubles.
ELEPCB can offer you industrial-grade PCB manufacturing support for various types of via technologies. Our design-for-manufacturing (DFM) team analyzes every layout to verify that the PCB satisfies both the functional and fabrication aspects.
Need help selecting the right via treatment for your next PCB project?
Get in touch with us today at ELEPCB either to talk over your design or to ask for quick and competitive PCB manufacturing quote.
FAQs
A1: No, it is not needed to use via filling on all PCB designs. Via filling should only be used when designing for high reliability, using fine pitch BGA components, or using via in pad technology. For regular low-cost PCBs, either tenting or plugging will generally be adequate. The best method to use is based on the PCB’s overall complexity and performance requirements, along with the PCB’s manufacturing budget.
A2: A “via in pad” means that the via is located within the solder pad of a part. In order to not allow the solder to flow down into the via hole, and to provide a level surface for solder, a complete fill and planar surface must be created with the adjacent surface. This will also guarantee the strength of the solder joint as well as provide a stable method of mounting the fine pitch BGA device.
A3: Choose a treatment based on the PCB application, component density and reliability requirements, along with the available budget. If PCB will be typical standard boards, then tent the vias. If there is a need to improve soldering, provide additional protection, or use plugging. If it is for designing an HDI PCB with fine pitch BGAs or an application that requires the highest performance and enduring quality, then use fill.
A4:
Yes. When you fill vias with material, it creates a better thermal pathway from all of the heat-generating parts to the PCB’s internal copper layer, allowing the spread of heat more effectively. As a result, component temperatures are decreased. Therefore, the reliability and life of thermally demanding electronic devices are increased.
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