What Are Plated Through Slots in PCBs?

Plated through slots are elongated, metallized holes in printed circuit boards that serve specialized functions beyond standard circular vias. These rectangular or oval-shaped through-holes feature full copper plating along their interior walls, creating continuous conductive pathways between board layers. At FanyPCB, we manufacture precision plated slots for high-current applications and secure component mounting in power electronics, automotive systems, and industrial equipment.

Applications of Plated Slots

1. High-current paths: Handle greater current than round vias (50A+ in some designs)

2. Component mounting: Secure large connectors/power devices with screw fastening

3. Thermal management: Improve heat dissipation in power electronics

4. Board stacking: Align and interconnect multilayer assemblies

5. Shielding: Create grounded partitions between board sections

Manufacturing Process for Plated Through Slots

Creating reliable plated through slots requires a carefully controlled fabrication process. It begins with precision routing, where CNC machines cut the slot shapes with exceptional accuracy (±0.05mm tolerance). The slots then undergo deburring to remove any rough edges that could interfere with plating uniformity. Next, the boards receive electroless copper deposition, which forms a thin conductive base layer (1-2μm) across all surfaces, including the slot interiors.

The critical electroplating stage follows, where electrical current builds up the copper thickness to the specified 25-50μm range needed for current handling. This step demands precise control of solution chemistry and current density to ensure even plating throughout the entire slot length. After plating, boards undergo rigorous quality checks, including automated optical inspection to verify plating integrity and thickness measurements via cross-section analysis. Finally, the slots receive any required surface finish (such as ENIG or HASL) to ensure proper solderability for component mounting.

Design Guidelines for Plated Slots

Designing effective plated slots requires attention to several key parameters. For reliable manufacturability, slot width should be at least 0.8mm, while the length-to-width ratio shouldn't exceed 4:1 to prevent plating solution trapping during fabrication. Plating thickness significantly impacts performance - we recommend minimum 25μm copper for standard applications and 35μm+ for high-current designs.

Board thickness also affects slot quality - while possible up to 3.0mm, best results come with 1.6-2.4mm thick boards. Always maintain at least 0.5mm clearance between slot edges and internal copper layers to prevent potential short circuits. For high-current applications, consider adding multiple parallel slots to distribute current flow and reduce localized heating. These design rules collectively ensure robust performance while maintaining manufacturability.

FanyPCB's Advanced Plated Slot Capabilities

Our specialized manufacturing capabilities enable superior plated slot performance. We produce high-aspect-ratio slots up to 6:1 length-to-width ratio for unique design requirements, with custom copper plating options ranging from 18-50μm to match your current needs. All production undergoes microsection analysis to verify plating uniformity meets IPC-6012 Class 3 reliability standards.

For power electronics designers, we offer complimentary DFM reviews to optimize your slot designs before production. Our engineers can recommend ideal slot configurations, plating specifications, and layout strategies tailored to your application's current requirements and thermal management needs. With advanced process controls and extensive experience in high-current PCB manufacturing, FanyPCB delivers plated slots with unmatched reliability for demanding applications.

Need expert guidance on plated slot implementation? Contact our FanyPCB engineering team for a consultation.