Like most electronic components, the quality of countless sub components and processes directly affects the quality and performance of the finished product. For PCB level connectors, these factors include pin material, plastic type, quality of molded plastic body, coplanarity of tail, quality of surface finish (electroplating), selecting the correct connector electroplating, manufacturing/assembly process (placing pins in plastic), and packaging.

Electroplating connectors is a critical task. Affects the lifespan and quality of terminals or sockets; It will affect corrosion resistance, conductivity, weldability, and of course, cost.

1、 Why use gold plating

Jintong is commonly used in high reliability, low voltage or low current applications. Gold is used for high cycle applications because it is sturdy, durable, and has excellent wear resistance. Samtec's gold and cobalt alloys increase hardness. Gold is a precious metal, which means it has little response to the environment. Therefore, gold is also recommended for use in harsh environments as it does not produce oxides that may increase contact resistance.

Sometimes, gold is a necessity because with the miniaturization of connectors, the contacts are too small to generate significant normal forces. Therefore, low normal force guides the need for gold plating. The main disadvantage of gold is its cost, followed by the porosity of thinner electroplated coatings and some subtle differences in weldability. Specifically, many customers "successfully" welded these, but they did not weld to Au because Au dissolved in the melted solder. They are welded to nickel under Au. Therefore, technically speaking, it is correct that the weldability of gold is poor.

2、 Why use tin plating

Tin is a low-cost alternative to gold and has excellent solderability. Unlike gold, tin is not a precious metal. Tin plating begins to oxidize when exposed to air. Therefore, the tin plated contact system requires greater normal force and longer contact wiping area to break through this oxide film. Tin is usually the preferred choice because it is relatively low-cost in applications with a small number of coordination cycles with appropriate normal forces.

3、 What is the most popular electroplating option

Selective gold tin plating is Samtec's most popular electroplating option as it provides designers with a win-win solution. The contact area, which is the critical area for contact with terminal pins and signal transmission, has the reliability of gold. Welding the tail onto the board reduces the cost and improves the solderability of tin.

4、 Can gold be soldered

This process should be carefully considered, as gold plating dissolves in the solder, so there is a real risk of contamination and gold embrittlement in the solder tank:

As mentioned earlier, solder paste will not weld onto the gold plate. The gold plate is dissolved in melted solder and welded onto a nickel substrate.

Once the contribution of gold weight to the solder joint is 3% to 5%, embrittlement becomes a problem.

5、 What is the effect of gold plating thickness on electronic contacts and connectors

The price of gold is hovering near historical highs, so it is expected that manufacturers using it will want to reduce costs as much as possible. Therefore, we are often asked if it is possible to reduce the amount of gold. It depends on the situation. There are two methods to achieve this: either reduce the coating area or reduce the thickness of the gold deposit. In some cases, selective electroplating can be used to reduce areas that require gold. As for reducing thickness, it depends on the application, many of which are constrained by MIL or ASTM specifications. This is especially true for gold-plated components used in military and aerospace applications. Commercial and consumer products may be candidates for thinning, but the possibility of sacrificing performance and lifespan must be considered.

It is crucial to specify and maintain appropriate plating thickness for optimal performance from passive electronic components. When specifying thickness, many factors must be considered, including product application, environment, and expected lifespan.

For certain components, the most important concerns may be insertion and extraction force and lifecycle testing. Regardless of the thickness used, nickel hardened gold may be more resilient than its softer pure gold. In this case, thickness is not as important as hardness. However, if lifecycle testing is crucial, then a thicker gold coating of 0.000050 inches will last for more cycles than 0.000030 inches.

For other components, weldability or porosity may be a key characteristic. When porosity is important, it is best to have a heavier gold coating or two layers of gold. However, higher gold thickness can have a negative impact on weldability. Gold exceeding 0.000050 inches can cause solder joints to become brittle, so less gold is most suitable for correctly bonding to nickel substrates.

If high cycling, low force, good porosity, and weldability are required, please do not worry. If the connector is pre tinned before being put into use, a gold deposit with 0.000050 inches of gold will provide all the above functions. Pre tin plating will remove most of the gold and protect the nickel surface with a tin coating. When ultimately welded in its application, any remaining gold will be removed.

Many contact components only fit once in relatively mild environments, which makes insertion/extraction and porosity less important. This is another example where gold is sufficient. So, can thinning save money? In some cases, yes. But we must remember that the main reason for specifying gold for connector components is corrosion resistance and conductivity. These factors must be at the core of any thinning decision.