PCB Surface Treatment Based on Soldering, Contact, and Delivery Requirements

OSP Organic Solder Protection Film

OSP forms an organic protective film on the copper surface; the key considerations for selection are the soldering process, storage, and operating conditions.

Selection Considerations: Flat Pads and Cost-Sensitive Projects

Avoid touching, scratching, and uncontrolled cleaning; the number of recirculation cycles should be determined based on the specific chemical solution system and process validation.

Hard Gold and Golden Fingers

Hard gold plating is commonly used in contact areas; the specific plating scheme must be determined based on insertion/removal, friction, and structural requirements.

Selection Considerations: Connector Contact Surfaces and Gold Fingers

Since the wear resistance requirements for contact points differ from those for welding, the brazed areas, electrical connections, and edge treatment of the boards must be clearly defined.

Gold Plating (ENIG)

ENIG consists of a chemical nickel layer and an immersion gold layer, providing a smooth surface for the pads.

Selection Considerations: Assemblies with Fine Pitch and Stringent Pad Flatness Requirements

The quality of the nickel layer and the gold plating process must be controlled; electroless gold plating should not be treated as hard, wear-resistant gold, nor should it be assumed to be suitable for all wire bonding processes.

Lead-containing tin plating

Lead-containing HASL uses lead-based solder for hot-air leveling; be sure to clarify the product's material requirements before making a selection.

Selection Considerations: Identify Projects Where the Use of Lead-Containing Solder Is Permitted

Pad height consistency must be verified in conjunction with the device and assembly; materials must not be deemed compliant with product restrictions based solely on their names.

Lead-Free Solder Spraying

Lead-free HASL protects the soldered surface through solder coverage and hot-air leveling.

Selection Considerations: Standard Assembly and Cost Control Requirements

Thermal processes and surface flatness must be evaluated in conjunction with the spacing between panels and components; a single spacing threshold cannot be used to assess all designs.

Sunk Silver

Silver plating forms a layer of silver on the surface of copper; its suitability must be determined based on the welding, storage, and operating environments.

Selection Considerations: Welding areas requiring a flat surface

Avoid contamination and improper packaging; evaluate the impact of the environment on the surface condition; store under the agreed-upon conditions after opening.

Shen Xi

Tin plating forms a layer of tin on the copper surface; therefore, storage, thermal processes, and the final joining method must all be taken into account.

Selection Considerations: Flat Pads and Proven Crimping Applications

Focus on changes in the copper-tin interface over time and during thermal processes, as well as the project’s requirements regarding tin whiskers and reliability.

Nickel-Palladium-Gold ENEPIG

ENEPIG uses a composite layer of nickel, palladium, and gold and is suitable for projects requiring a comprehensive evaluation of both welding and bonding.

Selection Considerations: Packaging Requirements for Both Soldering and Wire Bonding

Verification must be performed based on actual bonding conditions, such as gold, copper, or aluminum wires; the palladium layer cannot serve as a substitute for controlling the overall process quality.

What is the final connection?

Welding, crimping, wire bonding, and repeated insertion and removal place different demands on the surface, so a single board may require different treatments in different areas.

What is the assembly process?

Based on an evaluation of component spacing, pad flatness, reflow processes, cleaning, and rework requirements, no single process can guarantee all assembly results.

How are delivery and storage arranged?

Confirm the packaging, handling after opening, expected storage duration, and operating environment; the shelf life shall be determined based on the actual manufacturing process and agreed-upon conditions.