What are the Connector Contact Materials and Plating? Base Material Our
Connectors typically use a copper alloy as the base material for their contacts (pins). However, different alloy materials offer various levels of conductivity performance and physical endurance.
Here`s a comparison of the common base materials :
Brass Lowest cost
Good strength and spring properties
Good conductor
Phosphor Bronze
High level of strength and conductivity
Superior elasticity
Excellent fatigue resistance
Berylium Copper (Be-Cu)
High level of strength and conductivity
Highly expansive
Plating Plating affects the connector`s performance, life cycle, quality, and cost.
Plating involves two parts: underplating and finish plating:
Under-plating
Underplating is used to enhance the performance. This process forms an internal diffusion barrier (Zn and Cu through gold) and prevents pollutants from reacting with base metals. It also acts as a medium to help the finish plating adhere to the base material. Nickel is the most common and important under-plate in current use for these reasons:
Corrosion resistance
Wear resistance
Solderability
Finish plating
Finish plating is the second step of the plating process that helps strengthen the electrical conductivity. There are various options for finish plating, depending on the design requirements and budget.
I. Gold Plating:
Excellent resistance to corrosion
Excellent conductivity and low electrical resistance
High cost
II. Tin Plating:
Excellent solderability and conductivity
Low durability and can form an oxide film
High cost
*Tin can be further characterized as bright tin or matte tin.
A. Bright Tin
Bright tin can be easily identified by its glossy texture. It works well against corrosion, while sacrificing its solderability.
B. Matte Tin
Matte tin, as opposed to bright tin, has a dull texture, which is not as appealing as the bright tin. However, it offers a good level of protection against corrosion without sacrificing its solderability.
III. Selective Gold-Tin Plating
This type of plating offers tin plating on the tail and gold plating on the contact area. It offers a good balance between the advantages of gold and the lower cost of tin.
Plastic Insulators
Plastic
Insulators are fundamental to board-to-board connectors. They are used to hold the conductors, or pins, together to create the desired shape of the connectors. Different insulators also perform differently regarding to their strength, weatherability, and chemical resistance.
Here are some of the plastic insulators that can be used in a variety of applications:
Common Insulators
Polybutylene Terephthalate (PBT)
Excellent dielectric strength under high temperatures (230°C) and high humidity
Great formability with low shrinkage rate
Low flammability
Great impact strength
Available in Halogen-free options
Acrylonitrile Butadiene Styrene (ABS)
Good impact toughness even at low temperatures
Great wear resistance against rough surfaces
Shiny appearance
Economical
Insulators for High temperature(SMT-Grade)
High Performance Polyamide (PA 46 , PA 6T)
Temperature rating, PA46 290°C, PA6T 320°C
Good elongation
High rigidity, even at high temperatures
Available in Halogen-free options
Liquid-Crystal Polymer (LCP)
Temperature rating between 290-320°C
Great dimensional stability and weatherability
Chemically inactive
Great moldability, popular for designs requiring high precision and low flammability (UL 94V-0)
Available in Halogen-free options
