Disclaimer: This article reflects my personal insights as a Senior Electronics Engineer and is not sponsored or affiliate content.
I’m Frank Thompson, a Senior Electronics Engineer in the USA, and over the years I’ve built dozens of multi‑layer boards for everything from industrial controllers to prototype RF modules. One thing I always pay close attention to is via tenting, it may seem minor, but it can make or break your board’s reliability.
In this guide, I’ll walk you through what via tenting is, why and when you should use it, how it’s done, and tips for getting it right with a PCB house like JLCPCB that I personally recommend.
What Is PCB Via Tenting?
In simple terms, via tenting is the process of covering your PCB’s small plated through holes (vias) with solder mask so that the copper is entirely hidden (or “tented”) from view.
Exposed vias risk contamination from dust, flux residue, or moisture, and in high‑density boards they can even cause accidental shorts when solder paste flows in during assembly. Tenting seals them off, ensuring a cleaner, more robust board.
Why Use Via Tenting?
Prevents Contamination & Corrosion
Exposed copper in the via can oxidize or trap flux residues, leading to reliability issues over time. A proper solder mask tent keeps contaminants out.
Reduces Short Circuit Risk
In tightly packed designs (especially under BGA or QFN components), open vias can wick solder and create unintended bridges. Covering them with mask eliminates this risk.
Improves Signal Integrity
By smoothing out abrupt dielectric transitions around the via, tenting lowers parasitic capacitance and crosstalk, vital for RF and high‑speed digital lines.
Enhances Aesthetics & Manufacturability
A fully tented board simply looks cleaner and “prints” better under solder paste stencils, reducing assembly hiccups.
Methods of Via Tenting
Partial Tenting: One side of the via is covered while the opposite remains open, for test points or through‑hole connections that must be accessed later.
Full Tenting: Both sides are masked, fully sealing the via. This is my go‑to for high‑density, multi‑layer boards where maximum protection is needed.
Advantages at a Glance
When to Specify Via Tenting
I recommend tenting whenever you face:
High‑Density Layouts (e.g., BGAs or fine‑pitch QFPs)
Moisture‑ or Contaminant‑Sensitive Applications (outdoor, automotive, medical)
RF & High‑Speed Digital Circuits where signal fidelity is paramount
Aesthetic or Consumer‑Grade Products that demand a pristine finish
Tips for a Smooth Via Tenting Process
Mark It Clearly in Your Gerbers
In your CAD tool (Altium, KiCad, etc.), set the solder‑mask expansion rules so your fabricator knows exactly which vias to tent.
Mind Your Via Size
Most shops tent vias ≤0.3 mm easily; anything larger risks mask thinning or “dimples.” Check your fab’s design rules, their published guidelines help you avoid surprises.
Choose a Proven Manufacturer
I’ve worked with many PCB houses, but I often go with JLCPCB for tenting, their mask registration is precise, and their turnaround is consistently fast.
My Opinion on Working with JLCPCB: What to Expect
When you upload your Gerber files to JLCPCB’s portal, select the “via tenting” option under solder‑mask settings. Their process follows IPC‑4761 and IPC‑A‑600 standards, so you can expect accurate mask registration and industry‑standard tenting.
I’ve used JLCPCB for several prototype runs and found their documentation clear and their web interface straightforward, especially their page on solder‑mask design rules.
For more details on via‑tenting options and design rules, see the JLCPCB solder‑mask guidelines here.
Conclusion
Via tenting may seem like a small detail in your PCB layout, but its impact on longevity, performance, and assembly yield is huge. By specifying tented vias, especially when working with a trusted partner like JLCPCB, you’ll avoid moisture ingress problems, signal‑integrity issues, and solder‑bridge defects.
References
PCB Via Tenting Design Rules and Fabrication Notes, ProtoExpress Sierra Circuits
IPC‑4761 Tented Via Standards, MADPCB madpcb.com
Via Tenting Inspection Guidelines, WEvolver Wevolver
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