Home > Blog > Industry News > What is the plating process in PCB Manufacturing? If you鈥檙e evaluating a PCB Fabrication Service, it helps to understand why plating is one of the most important steps behind PCB reliability. PCB plating is not just 鈥渕etal deposition鈥濃攊t's the process that turns drilled holes and copper features into durable electrical interconnects that survive assembly heat, vibration, and long-term field use. In this guide, we鈥檒l narrate and explain the full PCB plating process, what happens before and after plating, how copper plating differs from surface finishing, and how to choose the right finish for your end application.
PCB plating is the controlled formation of metal layers鈥攑rimarily copper鈥攐n the board surface and inside drilled holes so the PCB traces can carry current, connect layers, and support soldering reliably.
Plating does three practical jobs:
Creates electrical connections between layers by metallizing hole walls (vias and through-holes).
Builds mechanical strength in vias and pads by adding copper thickness where stress concentrates.
Prepares the PCB for assembly by ensuring the board is solderable and resistant to oxidation.
Copper plating builds structural copper鈥攅specially inside holes and on traces.
Surface finishing (ENIG, HASL, OSP, etc.) is the final protective/solderable coat on exposed copper pads.
They hold the roles for each function and cannot be replaced by each other.
Without plating, multilayer PCBs would have no reliable way to connect internal layers, and even simple boards would suffer from rapid copper oxidation, poor soldering, and weak pad durability. In short: plating is what turns a patterned copper board into a functional circuit board.
Plating directly affects the connection between PCB layers:
Vias are not 鈥渉oles鈥濃攖hey are conductive but holes are not. Plating forms that conduction and ensures stable conduction between layers.
A via with insufficient copper thickness might fail under heat cycling. Plating adds the copper on 鈥渟tructure鈥 that support the via intact.
Sometimes solder defects could be traced back to surface condition. A properly controlled plating + finish system improves wetting, reduces rework, and stabilizes quality across lots.
A simplified flow looks like this:
Drilling 鈫 Desmear 鈫 Activation 鈫 Plating 鈫 Imaging 鈫 Etching 鈫 Surface Finish
Drilling creates a mechanical feature. Plating turns it into an electrical interconnect. That鈥檚 why drilling and plating are inseparable in reliability planning.
Copper plating is the foundation. Everything else builds on it.
After drilling, hole walls are non-conductive (epoxy/glass). Electroless copper deposits a thin, continuous conductive layer so the hole can later be electroplated.
Key points:
鈼 Why it鈥檚 needed: electroplating requires conductivity; raw hole walls don鈥檛 have it.
鈼 Principle: an autocatalytic chemical reaction deposits copper evenly on activated surfaces.
鈼 Purpose: create a continuous seed layer for reliable via formation.
鈼 Reliability role: a poor electroless layer can lead to voids, skips, or weak adhesion later.
Once a conductive seed exists, electroplating builds copper thickness using controlled current.
Key points:
鈼 How it works: electrical current drives copper ions to deposit on conductive surfaces.
鈼 Via strengthening: builds copper thickness on the hole wall (barrel) and surface copper.
鈼 Thickness control: managed by current density, bath chemistry, agitation, and time.
Why it can鈥檛 replace electroless copper: electroplating cannot start reliably on non-conductive hole walls.
Plating quality is decided before plating starts. Pre-treatment is where many failures are planted.
Drilling leaves resin smear and debris. If not removed, copper cannot bond properly to the hole wall.
Removes oils and residues from prior processes. Contamination will hurt adhesion and increases void risk.
Creates a controlled surface texture that improves copper adhesion and consistency.
Activation seeds catalytic sites for electroless deposition. Poor activation can cause discontinuities and weak via barrels.
If the copper seed layer isn鈥檛 well-adhered or continuous, later electroplating amplifies the problem鈥攔esulting in voids, thin spots, and reliability failures.
The most common plating function in multilayer PCBs:
鈼 forms conductive barrels in holes
鈼 enables electrical interconnection between layers
鈼 requires consideration of hole aspect ratio for uniform copper deposition
Used for:
鈼 local reinforcement
鈼 repair/rework scenarios
鈼 low-volume adjustments where full replating isn鈥檛 feasible
For edge connectors:
鈼 excellent wear resistance
鈼 low contact resistance
鈼 stable mating performance for repeated insertion cycles
Often used in connector and leadframe-like applications:
鈼 high throughput
鈼 automated, consistent selective deposition
鈼 efficient for mass production of plated contact regions
Many engineers whom are not familiar with fabrication, might mix up PCB copper plating with surface finishing. They鈥檙e related, but they reach different targets鈥攁nd they are different stages of the PCB plating process.
Copper plating is the structural layer of the PCB. It forms:
鈼 Via barrels and plated through-holes so layers are electrically connected
鈼 Copper thickness on traces/pads to meet current, thermal, and reliability requirements
Think of copper plating as the part that makes the board electrically complete and mechanically strong.
A surface finish is the final protective and solderable surface applied to exposed copper pads (and sometimes traces). It exists after copper plating because:
鈼 copper oxidizes quickly in humid environment, which hurts solder wetting and increases resistance
鈼 assembly needs controlled, repeatable solderability (especially for fine-pitch parts)
鈼 some applications require special contact behavior (e.g., edge connectors needing hard gold)
A surface finish does not replace copper plating. Finishes like ENIG, HASL, OSP, immersion silver/tin are typically very thin and mainly serve for solderability/corrosion protection. Copper plating is what ensures layer-to-layer continuity and via reliability. In short:
鈼 Copper plating = connectivity + strength
鈼 Surface finish = solderability + protection
鈼 Strength: cost-effective, widely used
鈼 Limit: planarity can be less ideal for very fine pitch
鈼 Strength: flat surface, good corrosion resistance, fine-pitch friendly
鈼 Consideration: process control is critical to avoid issues like black pad
鈼 Strength: good electrical performance for certain high-frequency needs
鈼 Risk: more sensitive to handling and storage conditions
鈼 OSP: cost-effective for SMT, but storage/handling control is important
鈼 Immersion tin: solderability-focused, requires storage discipline
鈼 ENEPIG: good for advanced assembly needs (fine pitch, wire bonding scenarios)
鈼 Hard gold: best for wear contacts (edge fingers), higher cost
A strong PCB needs proper copper where stress is highest鈥攐ften in via barrels and pads.
High aspect ratio holes are harder to plate uniformly. The risk is thin copper in the center of the barrel.
Current doesn鈥檛 distribute evenly across complex panels unless the process is tuned. Poor distribution causes uneven thickness.
鈥淭hrowing power鈥 describes how well plating reaches deep into holes. Better throwing power improves via reliability.
Adhesion is affected by pretreatment, micro-etch control, activation, and bath stability. Weak adhesion can lead to barrel cracks and delamination.
Often caused by:
鈼 poor desmear/cleaning
鈼 incomplete activation
鈼 trapped air or chemistry issues during deposition
Can result from:
鈼 challenging aspect ratios
鈼 inadequate throwing power
鈼 poor current distribution or time control
Typically linked to:
鈼 contamination
鈼 poor adhesion due to pretreatment gaps
鈼 material compatibility issues under thermal stress
A surface finish defect tied to nickel/gold process control. It鈥檚 not 鈥渃opper plating,鈥 but it鈥檚 part of the finishing system that affects solder reliability.
Usually caused by:
鈼 current crowding
鈼 panel density effects
鈼 inadequate process optimization for mixed feature distribution
Uses controlled pulse current to improve deposit structure, potentially helping uniformity in demanding features.
Improves consistency and throughput for certain production profiles through controlled flow and uniform deposition conditions.
Alternative approaches that reduce dependency on traditional palladium activation systems and can simplify process control in some lines.
Introduction for Microvias:
鈼 smaller diameters
鈼 different geometry (depth/diameter)
鈼 higher sensitivity to voids
Process tuning becomes critical to maintain reliable via fill and consistent copper thickness.
Design vias that are plateable reliably. Extreme aspect ratios increase defect risk and cost.
Over-specifying thickness increases time and risk without improving performance in many designs.
Balanced copper distribution improves:
鈼 plating uniformity
鈼 reduced warpage risk
鈼 consistent thickness across panels
Choose a finish that matches:
鈼 component pitch and assembly method
鈼 shelf life needs
鈼 environment (humidity, corrosion, wear contacts)
Choosing the right PCB plating approach and surface finish isn鈥檛 about picking the 鈥渂est鈥 option鈥攊t鈥檚 about matching reliability needs, assembly risk, and total cost. Below is a buyer-friendly way to decide, without getting lost.
Ask what the board must survive:
鈼 High humidity / corrosive atmosphere: prioritize finishes with stronger corrosion resistance and stable storage behavior.
鈼 High temperature cycling / vibration: focus on via plating robustness (uniform copper thickness, strong adhesion) because mechanical stress shows up first in vias and pads.
鈼 Wear/contact applications (edge connectors): plan for hard gold finger plating rather than standard solderable finishes.
Assembly requirements often narrow the choice quickly:
鈼 Fine-pitch SMT, BGA, dense layouts: you generally need a flat, consistent finish to reduce short and rework risk.
鈼 General SMT / mixed technology: you have more flexibility, choose based on storage, cost, and process stability.
鈼 Multiple reflow cycles or tight yield targets: prioritize finishes that maintain solderability through thermal exposure and handling.
How long will boards sit before assembly鈥攁nd under what conditions?
鈼 Long storage, international shipping, uncertain production windows: choose a finish with more forgiving shelf life and packaging tolerance.
鈼 Fast turn builds with controlled storage: you can consider finishes that demand stricter handling, if they offer benefits for your design.
Instead of comparing unit price only, compare total cost of the whole production:
鈼 scrap/rework risk
鈼 inspection requirements
鈼 field return risk
鈼 schedule stability if a finish is more sensitive to handling
Your Priority | Plating Focus (Copper) | Finish Focus (Surface) | Why it matters |
Highest reliability / harsh use | Tight control of via copper thickness + adhesion | Corrosion-resistant, stable finish | Prevents barrel cracks, oxidation, field failures |
Fine-pitch, high-density assembly | Uniform plating + consistent pads | Flat finish compatible with fine pitch | Improves yield, reduces bridging/rework |
RF / high-speed performance | Consistency and uniformity (avoid discontinuities) | Finish with stable electrical behavior + controlled handling | Minimizes loss variation and assembly defects |
Cost-sensitive but stable production | Standard plating spec, good uniformity control | Practical, widely supported finish | Keeps cost down without risking yield |
Edge connectors / frequent mating | Reinforced copper where needed | Hard gold on fingers | Wear resistance + low contact resistance |
Because drilled hole walls are not conductive. Electroless copper creates the seed layer so electroplating can build thickness reliably.
It depends on reliability class, aspect ratio, and application stress (thermal cycling, current load). The key is consistent barrel thickness, not just an average number.
ENIG is a flat nickel/gold finish suitable for fine pitch; HASL is cost-effective but can be less planar. Selection depends on assembly density and process needs.
ENIG is commonly used for fine pitch due to flatness, but the 鈥渂est鈥 depends on the full assembly profile and reliability target.
Copper layers are internal structure; surface finish and storage conditions determine solderability shelf life. Proper packaging and handling extend usability significantly.
The PCB plating process is where a PCB becomes electrically connected between layers and mechanically strong enough to survive real-world stress. Copper plating builds the via barrels and conductive structure; surface finishes protect solderability and corrosion resistance. When plating is controlled well鈥攕tarting with pretreatment鈥攜ield improves, assembly defects drop, and long-term reliability becomes predictable.
If you鈥檙e selecting a supplier, look beyond 鈥渢hey do plating鈥 and ask how they control it: pretreatment discipline, thickness uniformity, microsection verification, and HDI capability are what separate a basic factory from a reliable partner.
For Benlida鈥檚 capabilities across board types and manufacturing options, you can start with their PCB Fabrication Service and match the plating and finish strategy to your product requirements.
Sonic Yang
As a major of Electronics and Mechanical Automation, Sonic has been engaged in PCB design, R&D, manufacturing of eletronics for around 22 years, as engineering director and coordinates with supply chain(components&CNC parts), providing professional supports and consults for global customers.
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