Surface finish classification of PCB
A surface finish goes over the copper parts on printed circuit boards. This layer keeps the pcb safe from rust and helps with soldering when putting it together. The best surface finish makes every pcb work better and last longer. LT CIRCUIT has special choices for different needs in circuit boards and pcb surface finish.
Key Takeaways
Picking the right PCB surface finish keeps the board safe from rust. It also helps with soldering. This makes the PCB last longer and work better.
Metallic finishes like ENIG and ENEPIG give strong protection. They have flat surfaces and last a long time. Organic finishes like OSP cost less but do not last as long.
LT CIRCUIT gives expert help and many surface finishes. They help you choose the best one for your project’s needs, budget, and how reliable it must be.
PCB Surface Finishes
Printed circuit boards need a layer to protect copper. This layer is called a surface finish. There are two main types of pcb surface finishes: metallic and organic. Each type has special features that change how the board works and lasts.
Metallic Surface Finish
Metallic surface finishes use metals like tin, nickel, gold, or silver. These metals cover the copper pads on a pcb. They stop the copper from rusting and help with soldering. Metallic finishes also let electricity flow well and protect for a long time.
Hard gold plating gives great electrical flow and does not wear out fast. It is used for edge connectors and contact points because it lasts long.
ENIG uses a nickel layer with a thin gold layer on top. This finish is flat, stops rust, and is good for small parts.
ENEPIG adds a palladium layer between nickel and gold. This finish stops rust even better and makes strong solder joints. ENEPIG works with both lead-free and regular solder.
Immersion silver and immersion tin are also metallic finishes. Immersion silver lets electricity flow well and does not cost much, but it does not last long. Immersion tin gives a smooth surface and is easy to solder, with a thickness of 20 to 50 microinches.
Industry data shows metallic finishes like ENIG and ENEPIG work very well in important jobs. For example, ENEPIG has no pores and strong bonds, so it is used in advanced devices. Hard gold finishes, with gold from 30 to 50 microinches over 100 microinches of nickel, last long and are tough.
Tests show metallic finishes let electricity flow better than organic ones. Hard gold and immersion nickel gold finishes give steady flow and do not wear out, which is needed in hard places.
Organic Surface Finish
Organic surface finishes use a thin organic layer to protect copper pads. The most common type is OSP. OSP is water-based, flat, and good for the environment. It is lead-free and works well for small and surface mount parts.
OSP finishes do not cost much and are easy to use. They keep copper pads ready for soldering. But OSP does not last long and can be hurt by touching. Studies show OSP can help solder joints not break when dropped, but copper pads can wear out over time.
Making osp means putting a thin organic coat on copper pads. This is fast and does not need fancy tools, so it is used for making lots of pcbs.
Common Types
There are many pcb surface finishes today. Each one has its own good points and best uses. Here are the most common types of pcb surface finishes:
HASL (Hot Air Solder Leveling)
HASL covers the pcb with melted solder and blows off extra with hot air. This finish is cheap, easy to get, and solders well. But it can make the surface bumpy, which is not good for small parts.Lead-Free HASL
This finish is like HASL but uses lead-free solder. It meets RoHS rules and is safer for nature. Lead-free HASL lasts long and solders well, but the surface can still be bumpy.ENIG (Electroless Nickel Immersion Gold)
ENIG gives a flat, smooth surface and stops rust. It is great for small parts and important jobs. ENIG costs more but works well and lasts long.ENEPIG (Electroless Nickel Electroless Palladium Immersion Gold)
ENEPIG adds a palladium layer for even better rust protection and strong solder joints. It works with both lead-free and regular solder. ENEPIG is a top pick for advanced electronics.Immersion Silver
Immersion silver lets electricity flow well and does not cost much. It is easy to damage and does not last long.Immersion Tin
Immersion tin gives a smooth surface and is easy to solder. It meets RoHS rules and is good for small parts. The finish is 20 to 50 microinches thick.OSP (Organic Solderability Preservative)
OSP is a thin organic layer that protects copper pads until soldering. It is lead-free, flat, and good for the environment. OSP is best for small and surface mount parts but does not last long.
LT CIRCUIT offers all the common pcb surface finishes listed above. The company uses new technology and strict checks to make sure each pcb is high quality. LT CIRCUIT helps customers pick the right surface finish for their needs, like for electronics, phones, or machines.
The table below shows the main features of these finishes:
Surface Finish | Cost | Lead Time | Solderability | Lead-free Solder Compatibility | Fine Pitch Components | Corrosion Resistance | Typical Thickness (microinches) |
|---|---|---|---|---|---|---|---|
HASL | Low | Short | Good | Yes | No | High | N/A |
ENIG | High | Moderate | Excellent | Yes | Yes | Excellent | Nickel: ~100, Gold: thin layer |
ENEPIG | High | Moderate | Excellent | Yes | Yes | Excellent | Gold: 30-50 over Nickel: 100+ |
Immersion Silver | High | Moderate | Excellent | Yes | Yes | Low | N/A |
Immersion Tin | High | Moderate | Excellent | No | Yes | High | 20-50 |
OSP | Low | Short | Good | No | Yes | Moderate | Very thin |
PCB surface finishes are very important for how well circuit boards work and last. Picking the right finish depends on what you need, how much you want to spend, and the job. LT CIRCUIT’s many choices and skill help every customer get the best finish for their project.
Surface Finish Selection
Comparison Table
A surface finish comparison helps people pick the best one for their pcb. Each surface finish has its own features, price, and uses. The table below shows how each finish does in things like shelf life, soldering, flatness, and strength.
Surface Finish | Cost | Shelf Life | Solderability | Flatness | RoHS Compliance | Durability |
|---|---|---|---|---|---|---|
HASL | Low | Medium | Good for large parts | Uneven | No (leaded) | Moderate |
Lead-Free HASL | Low-Medium | Medium | Good for large parts | Uneven | Yes | Moderate |
ENIG | High | Long (years) | Excellent | Very flat | Yes | High |
ENEPIG | Very High | Long (12+ months) | Excellent | Very flat | Yes | Very High |
Hard Gold | Very High | Very Long | Limited | Flat | Yes | Extremely High |
Immersion Silver | Medium | Short (6-12 months) | Excellent | Flat | Yes | Moderate |
Immersion Tin | Low-Medium | Short (30 days) | Excellent | Flat | Yes | Low |
OSP | Very Low | Short (3-6 months) | Good (temporary) | Flat | Yes | Low |
Another table shows how finishes work for different pcb assembly types:
Surface Finish | BGA and μBGA | Connector | Fine Pitch SMT | Flip Chip | Wire Bonding | Solder Joint Integrity |
|---|---|---|---|---|---|---|
ENIG | Yes | Yes | Yes | Yes | Yes | Good |
ENEPIG | Yes | Yes | Yes | Yes | Yes | Good |
Hard Gold | Yes | Yes | Yes | Yes | No | Poor |
Soft Gold | Yes | No | Yes | Yes | Yes | Poor |
Silver | Yes | No | Yes | Yes | No | Excellent |
Tin | Yes | No | Yes | Yes | No | Good |
These tables show ENIG and ENEPIG are very flat and easy to solder. This is important for small parts and BGA components. OSP and immersion tin do not last as long, so they are best for quick builds.
Choosing the Right PCB Surface Finish
Picking the right surface finish depends on many things. Each job has its own needs. Here are some important things to think about:
Cost: Try to get good performance without spending too much.
Application: Use ENIG for most electronics. Pick ENEPIG for things like planes or medical tools.
Reliability: ENEPIG protects better and lasts longer for important jobs.
Environment: ENEPIG and lead-free HASL are safe for nature and follow rules.
Shelf life: ENEPIG and ENIG last longer and stop rust.
Soldering and wire bonding: ENEPIG is good for wire bonding and soldering, which helps high-speed circuits.
Design: Use the right board size and materials to save money but keep quality.
Production: Making lots of boards at once can lower the price for each pcb.
Trade-offs: ENIG costs less but does not last as long as ENEPIG. ENEPIG costs more but is stronger and lasts longer.
Flatness: ENIG and ENEPIG are best for small parts and BGA.
Handling: OSP and immersion tin need to be used fast because they do not last long.
Environment: Use strong finishes for places with heat or lots of movement.
Tip: Always pick a finish that fits how the pcb will be used. For example, medical and plane parts need finishes that last long and work well.
LT CIRCUIT Advantage
LT CIRCUIT is special because it offers many surface finish choices. The company uses new technology and checks each pcb to make sure it is good. LT CIRCUIT gives:
Custom finishes for different jobs, like home electronics or factory machines.
Expert help to pick the best finish for your pcb, based on price, strength, and safety.
High soldering quality for all finishes, so connections are strong.
Fast making and testing, like flying probe and E-tests, to make sure you get your boards quickly.
LT CIRCUIT works hard to give customers the best finish for every pcb. The company’s skills and many products make it a good choice for strong and advanced pcb solutions.
Knowing about pcb surface finish classification helps people choose well. Picking the right surface finish makes the pcb last longer and work better. It also helps the pcb stay strong and reliable. The table below shows how ENIG and immersion silver are great for letting electricity flow and stopping rust. LT CIRCUIT gives smart pcb solutions for all kinds of needs.
Surface Finish | Conductivity | Corrosion Resistance | Shelf Life |
|---|---|---|---|
ENIG | Excellent | Excellent | Long |
Immersion Silver | Outstanding | Good | Very Long |
OSP | High | Low | Short |
LT CIRCUIT helps customers by giving good advice and strong pcb surface finishes for any use.
FAQ
What is the most common PCB surface finish?
Most PCBs use HASL or ENIG. HASL costs less and works for many uses. ENIG gives a flat surface and strong protection.
How does LT CIRCUIT help with surface finish selection?
LT CIRCUIT offers expert advice. The team reviews project needs and suggests the best finish for performance, cost, and reliability.
Can all surface finishes support lead-free soldering?
ENIG, ENEPIG, immersion silver, and lead-free HASL support lead-free soldering.
OSP also works with lead-free processes.
Some finishes, like standard HASL, do not.
See Also
Understanding HASL Finish Process And Quality In PCB Production
Essential Skills Required For Designing Multi-Layer PCB Layouts
How Panasonic Copper-Clad Laminates Are Used In PCB Fabrication
Comparing Single, Double, And Multilayer PCBs: Key Differences
Materials Commonly Used In The Construction Of Printed Circuit Boards
