Understanding PCB via types — through-hole, blind, and buried vias — is essential for intermediate and advanced PCB designers. Vias are the conductive holes that connect copper traces between different PCB layers, and choosing the right via type affects your board’s size, cost, and manufacturability. This guide explains each via type, when to use them, and how they affect your JLCPCB or PCBWay fabrication cost in India.
Table of Contents
- Via Basics: What Are Vias?
- Through-Hole Via: The Standard Choice
- Blind Via: Surface to Inner Layer
- Buried Via: Inner Layers Only
- Micro Via (HDI): Laser-Drilled
- Via-in-Pad: Dense Component Placement
- Cost Comparison at JLCPCB
- Frequently Asked Questions
Via Basics: What Are Vias?
A via (from Latin, “way”) is a plated-through hole in a PCB that creates an electrical connection between copper layers. Unlike component holes (which hold component leads), vias are purely for electrical interconnection. A via consists of:
- Drill hole: The physical hole bored or laser-drilled through the PCB
- Copper barrel: Electroplated copper lining the hole wall, connecting top and bottom (and inner layer) pads
- Annular ring: Circular copper pad on each layer the via connects to
Via dimensions:
- Drill diameter: Hole size after drilling. JLCPCB minimum standard: 0.3mm
- Finished hole size: Drill diameter minus copper plating thickness (typically 0.025-0.05mm per side)
- Pad diameter: Annular ring diameter. Must be drill + 2 × minimum annular ring width (0.1mm at JLCPCB)
Through-Hole Via: The Standard Choice
A through-hole via (or through via) passes completely through the entire PCB stackup from top surface to bottom surface. It creates electrical connections to ALL copper layers it passes through (or only the layers where it has a pad, if inner layer clearance is specified).
Characteristics
- Connects: Any combination of F.Cu, inner layers, and B.Cu
- Manufacturing: Mechanical drill + electroplating. Well-established, lowest cost.
- Minimum drill size: 0.2mm (laser), 0.3mm (mechanical) at JLCPCB standard service
- Typical sizes used by Indian makers: 0.3mm drill, 0.6mm pad (matches KiCad default via settings)
- Cost: Included in standard PCB price — no extra charge for through-hole vias
When to Use Through-Hole Vias
- 99% of all 2-layer and most 4-layer PCB designs
- Any connection between F.Cu and B.Cu
- Test points (vias with larger pads for probe access)
- Component mounting holes that also make electrical connections
Limitations
- The via occupies space on ALL layers — you cannot route under a through-hole via on inner layers (creates “via shadow” that must be avoided)
- Minimum diameter limited by mechanical drill capabilities (0.3mm in standard service)
- On dense BGA designs, through-hole vias take too much space — require HDI micro-vias instead
Blind Via: Surface to Inner Layer
A blind via starts from an outer surface (F.Cu or B.Cu) and terminates at an inner layer without going all the way through. Viewed from the opposite side, you cannot see the via — it is “blind” from that perspective.
4-Layer PCB cross-section:
F.Cu ============================== (top copper)
| |
Prep1 ==|===================|======== (prepreg)
| (buried via) |
In1 ============================ (inner 1 - GND plane)
| |
Core ==|==========================|= (core)
| |
In2 ========================== (inner 2 - PWR plane)
|
Prep2 ============================|= (prepreg)
|
B.Cu ============================== (bottom copper)
Blind via: F.Cu → In1 only (starts at top, ends at In1)
Buried via: In1 → In2 only (both ends inside)
Through via: F.Cu → B.Cu (passes all layers)When to Use Blind Vias
- Dense PCBs where routing on inner layers requires access from one side
- BGA (Ball Grid Array) packages with fine pitch — standard through-hole vias create too much congestion
- High-frequency designs where minimising stub length is critical
Cost at JLCPCB (2026)
- Blind vias add approximately $20-50 to order cost depending on design complexity
- Available only on 4+ layer boards
- Most Indian hobbyist projects do not require blind vias — through-hole vias are sufficient
Buried Via: Inner Layers Only
A buried via connects two or more inner layers but does not reach either outer surface. It is invisible from both the top and bottom of the PCB.
When to Use Buried Vias
- Extremely dense routing where inner layer connections must be made without consuming outer layer space
- Memory module PCBs (DDR4/DDR5 BGA connections)
- Advanced high-frequency RF designs requiring shortest possible interconnects
Limitations
- Significantly higher manufacturing cost (requires sequential lamination — the board must be partially assembled, drilled, plated, then laminated again)
- At JLCPCB: buried vias add $50-100+ to order cost
- Not available at all PCB manufacturers. Verify before designing with buried vias.
- Extremely rarely needed for Indian maker projects — almost exclusively used in telecommunications ICs and military-grade boards
Micro Via (HDI): Laser-Drilled
A micro via is a blind via with a very small diameter (typically 0.1-0.15mm) drilled using a UV laser rather than a mechanical drill. HDI (High Density Interconnect) PCBs use micro-vias extensively.
- Drill diameter: 0.1-0.15mm (vs 0.3mm minimum for mechanical drill)
- Depth: Limited to one dielectric layer (cannot go deep like through-hole)
- Applications: Smartphone PCBs, laptop motherboards, any design with fine-pitch BGA components
- Cost: Significantly higher — HDI PCBs at JLCPCB start at $20-40 extra for 5 pieces
- Stacked micro-vias: Multiple micro-vias stacked to connect 3+ layers — even higher cost and complexity
Via-in-Pad: Dense Component Placement
Via-in-pad means placing a via directly underneath a component pad (SMD pad or BGA ball). This allows much denser component placement as the via doesn’t need to be routed away from the pad.
Types of Via-in-Pad Filling
- Open via-in-pad: Via hole remains open. Solder can flow through and create poor solder joints. Generally avoided.
- Plugged via-in-pad: Via hole filled with conductive or non-conductive epoxy. Solder cannot flow through. More expensive but solderability is maintained.
- Capped (HASL) via-in-pad: After plugging, the via pad is covered with solder finish. This is the standard specification for JLCPCB via-in-pad service.
JLCPCB Via-in-Pad Pricing (2026)
- Plugged via-in-pad: Extra charge of approximately $15-25 for small order
- Available on both 2-layer and 4-layer boards
- Minimum via size for via-in-pad: 0.3mm drill, 0.5mm pad
Cost Comparison at JLCPCB
| Via Type | Extra Cost (JLCPCB) | When Needed |
|---|---|---|
| Through-hole via | Free (standard) | All standard designs |
| Blind via | +$20-50 | Dense 4-layer designs |
| Buried via | +$50-100+ | Very high density, rare |
| Via-in-pad (plugged) | +$15-25 | BGA, fine-pitch SMD |
| HDI micro-via (laser) | +$20-40 | Ultra-dense layouts |
Frequently Asked Questions
How many vias can I put on a PCB?
There is no practical upper limit on through-hole via count for JLCPCB standard service. Tens of thousands of vias are common in complex boards. All are included in the standard PCB price.
What is a thermal relief via?
In KiCad, when connecting a via to a copper pour (GND plane), the via is connected through a thermal relief pattern (thin spokes) rather than solid copper. This prevents the GND plane from acting as a heat sink during soldering, ensuring good solder joints. Enable “Thermal Relief” in pad properties or it will be applied automatically when adding vias to copper zones.
Should I use 0.3mm or 0.2mm vias?
For most designs, 0.3mm drill with 0.6mm pad is the standard. Use 0.2mm (laser micro-via) only when routing space is extremely constrained and your PCB manufacturer supports it. JLCPCB’s standard service minimum is 0.3mm mechanical drill. The 0.2mm and smaller vias require HDI service at extra cost.
Can I use blind vias in KiCad?
Yes. In KiCad 8, when placing a via, you can specify which layers it connects (F.Cu to In1.Cu only = blind via). The DRC will verify the via layers are valid. Blind via support requires selecting the correct option in Board Setup > Physical Stack Up.
Add comment