The high-frequency data line interface USB3.1typeC studied the reliability of connectors

The high-frequency data line interface USB3.1typeC studied the reliability of connectors

Failure Mechanism Analysis of USB3.1typeC

For many years, JCE has been focusing on the reliability analysis and research of electrical connectors, and has achieved fruitful results. We have summarized the reliability of electrical connectors. USB plugins have complex electromechanical dual characteristics during use, and their common failure modes and mechanisms are as follows:

1) Excess

The excess material inside the electrical connector can cause random signal failures. The main reasons are:

a. The selection of design materials and structure is unreasonable. Due to the use of different materials with significant differences in hardness for plugs and sockets, the structural form is inherently insufficient, posing a hidden danger of redundancy.

b. Poor adhesion of the polar layer, poor pre-treatment of the shell surface before foaming and peeling electroplating, prolonged residence time after copper plating, surface oxidation or abnormal composition of the plating solution can lead to easy peeling of the film after interchangeability inspection, especially at the assembly connection parts.

c. When checking the interchangeability of poor machining accuracy and dimensional consistency, it was found that there were residual machining burrs or tight tolerance fit dimensions in the assembly connection parts, resulting in excess material generated by cutting interference metal.

2) Poor contact

Poor contact can lead to high contact resistance and poor conductivity, which are also fatal defects of electrical connectors. From a microscopic perspective, any smooth surface is uneven. Therefore, when two contact points come into contact, it cannot be the entire contact surface, but a limited number of contact points. Obviously, the actual contact surface is smaller than the contact surface, and the difference depends on the surface smoothness and contact pressure. The actual contact surface is divided into two parts: one is the direct contact between metals, and the other is the deposition film formed by oxide film, organic gas adsorption film, or dust. Therefore, the main reasons for high contact resistance and poor conductivity are:

a. High concentrated resistance

Concentrated resistance refers to the resistance displayed by the contraction of the current line when current passes through the contact surface. It is the resistance formed by the direct contact between metal and metal formed by the contact pressure or thermal damage interface facial mask. Its size is related to the characteristics of the material itself, production process (such as roughness, electroplating quality, and performance after heat treatment), and contact pressure.

When the contact pressure increases, on the one hand, the number and area of contact points gradually increase, and on the other hand, when the pressure on the contact surface exceeds the yield limit of the material, the contact point will transition from elastic deformation to plastic deformation. Therefore, the concentrated resistance will decrease and eventually stabilize. Excessive socket size or relaxation of contact spring stress can reduce contact pressure and increase concentrated resistance.

To ensure reliable contact and a certain contact pressure, check the insertion force (separation force) of the socket and pin before assembly of the electrical connector. After assembling the finished product, the single hole and total insertion force should also be checked according to the technical conditions.

b. High film resistance

Membrane resistance refers to the resistance of the contact surface to form a film due to the influence of surrounding environmental conditions and harmful gases. When the electrical connector socket pins are silver plated, harmful elements such as carbon, sulfur, zinc, oxygen, etc. will appear on the contact surface. Produce an oxide film on the surface, making the contact resistance unstable. The growth of oxide film is closely related to temperature and humidity. The higher the temperature and humidity, the faster the growth rate, which is one of the main sources of membrane resistance. Another source of membrane resistance is dust, rosin, oil stains, etc. Mechanically attached to the contact surface, deposited on the contact surface, forming a loose surface film. Due to the ease with which these particulate matter can embed into the micro pits on the contact surface, the effective contact area decreases, the contact resistance increases, and is extremely unstable.

3) Poor insulation (leakage, low insulation resistance, breakdown)

There are pollutants such as wet dust and flux on the surface of the connector, organic sediment and harmful gas adsorption film dissolve with the surface water film, forming ion conductive channels.

4) Elastic element fracture

Due to poor material quality or improper heat treatment quality control, accidents such as brittle fracture and fatigue damage of elastic components such as springs and pressure springs are used as locking devices for electrical connectors. After the production of the electrical connector is completed, the fault mode and mechanism have been fixed. Only by strictly adopting reliability technical measures on the production line based on reliability design, such as strict control of production processes, control of production environmental conditions, and testing of various processes, can the reliability and stability of electrical connectors be guaranteed.