Modern printed circuit boards rely on vias to create electrical connections between multiple copper layers. While vias are a fundamental part of PCB design, one important decision that often affects manufacturing, assembly, and long-term reliability is whether those vias should be tented or left untented.
Choosing the right approach is more than a cosmetic preference. PCB via tenting can help protect vias from contamination, reduce solder-related defects, and improve assembly reliability. On the other hand, untented vias provide easier inspection, better accessibility for testing, and may be preferred in specific thermal or high-power applications.
Understanding the differences between these two options helps designers make informed decisions based on board complexity, manufacturing requirements, and end-use conditions.
What Is a PCB Via?
A PCB via is a plated hole that creates an electrical connection between different conductive layers of a multilayer printed circuit board. Instead of routing every signal on a single layer, vias allow designers to efficiently transfer signals, power, and ground connections throughout the PCB stack-up.
Depending on the design, a PCB may include several types of vias:
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Via Type
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Description
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Typical Application
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Through-Hole Via
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Extends through the entire PCB
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General multilayer PCB designs
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Blind Via
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Connects an outer layer to an internal layer
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HDI PCB layouts
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Buried Via
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Connects internal layers only
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High-density designs
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Microvia
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Laser-drilled small via
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Smartphones, wearables, aerospace electronics
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What Is PCB Via Tenting?
PCB via tenting is the process of covering the opening of a plated via with solder mask during PCB fabrication. Instead of leaving the copper ring exposed, the solder mask forms a protective layer over the via opening.
This protective coating helps prevent contaminants such as moisture, dust, chemicals, and flux residues from entering the via. It also minimizes the possibility of solder flowing into the via during component assembly.
Unlike via filling or plugging, tenting does not completely fill the hole. The via remains hollow internally while the surface opening is covered by solder mask.
Manufacturers commonly recommend PCB tented vias for standard multilayer boards where improved reliability and assembly performance are desired without adding significant manufacturing complexity.
Why PCB Tenting Is Used?
Covering vias with solder mask provides several manufacturing and performance advantages.
1. Improved Assembly Reliability
During SMT assembly, molten solder can wick into open vias located near component pads. This may reduce solder available for the joint and create weak or inconsistent connections. Tented vias help reduce this risk.
2. Environmental Protection
The solder mask acts as a barrier against contaminants including:
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Moisture
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Dust
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Cleaning chemicals
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Ionic contamination
This additional protection contributes to better long-term reliability, particularly in industrial and outdoor environments.
3. Reduced Risk of Solder Bridging
Closely spaced vias around fine-pitch components can increase the chance of accidental solder bridging. PCB tenting minimizes exposed conductive surfaces, reducing this possibility.
4. Cleaner PCB Appearance
Many OEMs prefer tented vias because they provide a cleaner, more uniform board appearance, particularly on products where visual quality is important.
What Is an PCB Untented Via?
An untented via remains exposed after solder mask application. The copper annular ring around the via opening receives the same surface finish as other exposed copper features, such as ENIG or HASL.
Untented vias are commonly selected when engineers require direct access to the via for electrical testing, troubleshooting, or inspection.
In some applications, exposed vias also improve heat transfer and simplify rework operations.
Unlike PCB tenting, untented vias require designers to carefully consider spacing from nearby pads to avoid solder-related manufacturing issues.
PCB Via Tenting vs. Untented Via
Selecting between tented and untented vias depends on the board's electrical, mechanical, and manufacturing requirements.
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Feature
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PCB Tented Vias
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PCB Untented Vias
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Solder Mask Coverage
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Covered
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Exposed
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Moisture Protection
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Excellent
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Limited
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Dust and Chemical Protection
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Excellent
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Moderate
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Solder Wicking Prevention
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High
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Lower
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Test Point Accessibility
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Limited
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Excellent
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Visual Inspection
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Moderate
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Easy
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Thermal Dissipation
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Moderate
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Better
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SMT Assembly Reliability
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Excellent
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Good
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Cosmetic Appearance
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Clean, uniform finish
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Visible copper rings
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Recommended Applications
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Consumer, Medical, Automotive, Industrial
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Prototypes, Power Electronics, Test Fixtures
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When Should You Use PCB Tented Vias?
PCB via tenting is recommended when reliability, environmental protection, and assembly quality are priorities. By covering vias with solder mask, it helps reduce solder-related defects, protects exposed copper, and improves overall PCB durability. The table below shows the recommended via type for common PCB applications.
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PCB Application
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Recommended Via Type
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Why It's Recommended
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BGA PCB Assemblies
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PCB Tented Vias
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Prevents solder wicking and improves solder joint reliability.
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Medical Devices
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PCB Tented Vias
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Protects against moisture and contamination for long-term reliability.
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Automotive Electronics
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PCB Tented Vias
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Enhances durability in harsh operating environments.
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RF Testing Boards
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Untented Vias
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Provides easy access for probing, testing, and signal measurements.
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Prototype PCBs
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Untented Vias
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Simplifies debugging, inspection, and design validation.
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Industrial Control Systems
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PCB Tented Vias
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Reduces contamination and improves assembly reliability.
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While PCB tenting is ideal for many production designs, the best choice depends on your PCB's performance, manufacturing, and application requirements.
When Should You Leave Vias Untented?
While PCB via tenting is widely used in modern PCB manufacturing, there are situations were leaving vias exposed is the better engineering choice.
Untented vias provide direct access to the plated hole, making them valuable during testing, inspection, and debugging. Engineers often choose untented vias when manufacturing requirements prioritize accessibility over environmental protection.
Common applications include:
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Prototype PCB development
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In-circuit testing (ICT)
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Functional test fixtures
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Power electronics requiring improved heat dissipation
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Designs that require manual probing during validation
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Repairable or serviceable electronic assemblies
For boards expected to undergo multiple inspection cycles or field maintenance, untented vias can simplify troubleshooting and reduce diagnostic time.
Altium Tented Vias: How to Configure Via Tenting
Many PCB designers use Altium Designer to control solder mask settings for vias during layout.
Rather than manually modifying each via, Altium allows designers to define solder mask expansion rules that automatically determine whether vias will be tented or exposed.
When configuring Altium tented vias, designers should:
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Define solder mask expansion values in the PCB Rules Editor.
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Apply consistent design rules across the entire PCB.
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Review manufacturer capabilities before finalizing the design.
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Verify solder mask coverage using 3D and Gerber outputs.
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Include fabrication notes indicating whether vias should be tented, plugged, or left open.
Before releasing manufacturing files, always perform a Design Rule Check (DRC) and consult your PCB manufacturer to ensure the specified solder mask settings align with their fabrication capabilities.
PCB Via Tenting Design Best Practices
Proper via tenting begins during the PCB layout stage. Following proven design practices helps improve manufacturability and reduces the likelihood of production issues.
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Choose Appropriate Via Sizes: Very large vias are more difficult to tent consistently because the solder mask may not completely bridge the opening. Smaller vias generally achieve better solder mask coverage.
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Maintain Adequate Pad Clearance: Avoid placing vias too close to SMT pads unless they are intentionally incorporated into the design. Proper spacing minimizes solder migration and improves assembly quality.
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Consider the PCB Assembly Process: Boards with fine-pitch components, BGAs, or automated surface-mount assembly often benefit from tented vias because they reduce solder-related defects.
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Verify Fabricator Capabilities: Every PCB manufacturer has minimum solder mask tolerances. Review fabrication guidelines before specifying tented vias to avoid unexpected manufacturing limitations.
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Document Manufacturing Requirements: Clearly identify via treatment requirements in fabrication drawings. If certain vias must remain exposed for testing or grounding, note these exceptions to prevent manufacturing errors.
Manufacturing Considerations for PCB Tenting
Selecting between tented and untented vias affects more than PCB appearance. It also influences fabrication, inspection, and assembly processes.
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Manufacturing Factor
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PCB Tented Vias
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Untented Vias
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Solder Mask Process
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Standard solder mask application
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Standard solder mask with exposed openings
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Inspection Access
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Limited
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Excellent
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Assembly Yield
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Higher near fine-pitch components
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Depends on via placement
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Cleaning Resistance
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Better contamination protection
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Requires additional cleaning attention
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Rework Accessibility
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Moderate
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Easier
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Long-Term Reliability
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Higher in harsh environments
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Depends on operating conditions
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Manufacturers frequently recommend tented vias for production assemblies because they help improve process consistency without significantly increasing fabrication complexity.
Common PCB Via Tenting Mistakes to Avoid
Even experienced PCB designers can encounter issues if via tenting is not considered during layout planning.
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Using Oversized Vias: Large via openings may not be fully covered by solder mask, resulting in inconsistent tenting.
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Ignoring Assembly Requirements: Leaving vias exposed near fine-pitch components can increase solder wicking and reduce solder joint reliability.
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Assuming All Manufacturers Use the Same Process: Fabrication capabilities vary between manufacturers. Always confirm solder mask tolerances before finalizing your design.
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Not Reviewing Gerber Files: Always inspect solder mask layers before releasing manufacturing files to ensure vias are treated as intended.
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Choosing Tenting for Every Via: Not every via requires tenting. Testing points, thermal vias, and certain grounding structures may perform better when left exposed.
Applications That Benefit from PCB Tented Vias
PCB tenting is widely used across industries where reliability and environmental protection are essential.
Typical applications include:
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Automotive electronic control units (ECUs)
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Medical diagnostic equipment
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Aerospace and defense electronics
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Industrial automation systems
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Telecommunications infrastructure
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Consumer electronics
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IoT devices
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Networking hardware
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Embedded computing systems
In these industries, reducing contamination and improving assembly reliability helps extend product life and minimize field failures.
How to Choose Between PCB Tented Vias and Untented Vias?
The best choice depends on your design objectives.
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If Your Priority Is...
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Recommended Option
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Preventing solder wicking
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PCB Tented Vias
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Moisture and contamination protection
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PCB Tented Vias
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Easier electrical testing
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Untented Vias
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Better thermal dissipation
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Untented Vias
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Fine-pitch SMT assembly
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PCB Tented Vias
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Frequent rework or inspection
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Untented Vias
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Long-term reliability
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PCB Tented Vias
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Rather than selecting one option for the entire board, many successful PCB designs use a combination of tented and untented vias based on functional requirements.
Why Choose Sierra Assembly for PCB Manufacturing?
Selecting the right via treatment is only one part of achieving a reliable PCB. Manufacturing expertise, design review, and process control are equally important.
At Sierra Assembly, our engineering team works closely with customers to optimize PCB designs for manufacturability, performance, and long-term reliability. From prototype builds to full-scale production, we evaluate via placement, solder mask requirements, and assembly considerations to help minimize defects and improve production yield.
Our capabilities include:
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Advanced PCB assembly services
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Design for Manufacturability (DFM) review
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Prototype-to-production support
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Fine-pitch and BGA assembly expertise
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IPC-compliant manufacturing processes
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Comprehensive electrical testing and quality inspection
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Fast turnaround for complex PCB projects
Whether your design requires PCB via tenting, untented vias, or specialized assembly solutions, our team is ready to support your project with precision and consistency.
Whether you're designing a prototype or preparing for high-volume production, Sierra Assembly provides reliable PCB manufacturing and assembly services tailored to your project requirements. Our engineering team can help evaluate via design, improve manufacturability, and support complex PCB assemblies from concept to production.
Contact us today to discuss your PCB project or request a quote from our experienced engineering team.
Frequently Asked Questions
1. Does PCB via tenting affect signal integrity?
Ans: No. PCB via tenting has little direct impact on signal integrity. Via design, PCB stack-up, and trace routing play a much larger role in signal performance.
2. Can all PCB vias be tented?
Ans: No. Large vias, thermal vias, and test vias may be left untented depending on the design requirements and manufacturing process.
3. How do I specify tented vias in PCB design software?
Ans: In software like Altium Designer, you can specify tented vias by configuring the solder mask expansion settings and including the requirements in your fabrication files.
4. Are tented vias recommended for high-density PCB designs?
Ans: Yes. Tented vias are commonly used in HDI and fine-pitch PCB designs to reduce solder wicking and improve assembly reliability.
5. Should prototype PCBs use tented or untented vias?
Ans: It depends on the project. Untented vias are useful for testing and debugging, while tented vias better represent the final production design and improve assembly reliability.
