A Brief Discussion on the Application of Beryllium Copper in Electrical Connecto

Abstract: This paper introduces the classification of beryllium copper alloys, along with the commonly used grades, chemical compositions, properties, and the current development status at home and abroad. It further discusses the application prospects and development directions of beryllium copper in the electrical connector industry.

Keywords: Beryllium copper; Electrical connectors

1. Introduction

Elastic materials are diverse in types, widely used, precisely processed, and uniquely functional. Copper-based elastic alloys are widely used in various conductive elastic components due to their excellent electrical and thermal conductivity as well as good mechanical properties. According to elastic performance, copper-based elastic alloys are generally classified into: high elasticity, medium elasticity, low elasticity, and composite elastic copper alloys.

The elastic material of electrical connectors is a key factor in ensuring stable insertion and retention forces. Currently, high-elasticity copper alloys are commonly used, which can be strengthened by heat treatment. A typical example is beryllium copper, a precipitation-hardened high-conductivity, high-elasticity alloy. Elastic components made from beryllium copper exhibit minimal elastic hysteresis and high resilience, making it a superior elastic copper alloy in terms of comprehensive performance.

This paper provides a basic overview of commonly used beryllium copper alloys, including their classification, grades, chemical composition, and properties. It also compares the development of beryllium copper at home and abroad and discusses its application potential and limitations in electrical connectors.

2. Research Overview of Beryllium Copper Alloys

2.1 Classification of Beryllium Copper

After solution and aging heat treatment, beryllium copper alloys exhibit high strength, hardness, and elastic limit. They also offer low elastic hysteresis, good stability, fatigue resistance, corrosion resistance, wear resistance, low-temperature performance, non-magnetic properties, high conductivity, and do not produce sparks under impact. Hence, they are known as the “king of non-ferrous elastic materials.”

Based on performance, beryllium copper alloys can be divided into:

• High strength and high elasticity alloys (Be content: 1.6%–2.1%)

• High conductivity alloys (Be content: 0.2%–0.7%)

Based on forming method, they are classified as:

• Wrought alloys: produced through pressure processing into sheets, strips, tubes, rods, wires, etc., and mainly used for elastic components like switches, springs, and contacts

• Cast alloys: feature high strength and hardness and are used in aerospace, electronics, and mechanical engineering—for example, bushings in aircraft, drill bits, etc.

2.2 Grades and Chemical Composition

This study focuses on high-strength and high-elasticity beryllium copper. The commonly used domestic grade is QBe2, a wrought beryllium copper alloy. Table 1 shows its chemical composition compared with similar Japanese and American grades. The differences lie in the presence of Co in the Japanese and American grades, while the Chinese grade contains more Ni.

Ni and Co play similar roles in suppressing over-aging during heat treatment and increasing alloy strength. The Japanese grade also contains a small amount of Si, which, when combined with Co in proper proportions, forms strengthening compounds such as CoSi or Co₂Si. However, Si content must be controlled to avoid forming hard and brittle Be-containing eutectic phases, which would significantly reduce alloy toughness.

Table 1: Comparison of Chemical Compositions of Domestic and Foreign Grades

QBe2 has seen widespread use; however, due to its high tendency for softening and adhesion during machining, it is prone to bonding with the tool surface, affecting heat dissipation and shortening tool life. To improve machinability, many countries have introduced Pb into the alloy. Pb forms dispersed particles during solidification, which are brittle and help break chips and reduce adhesion and welding, thus improving cutting performance.

Typical free-cutting beryllium copper grades include C17300 (USA) and QBe1.9-0.4 (China), which share the same chemical composition. According to GB/T 5231-2012, QBe1.9-0.4 is a direct reference to C17300.

Table 2: Free-Cutting Beryllium Copper Chemical Composition

2.3 Development Status

Currently, the world’s leading beryllium copper producers are Brush Wellman (USA) and NGK (Japan). China started relatively late in this field and still lags behind in terms of technology due to smaller production scales, outdated equipment, and low automation levels.

Major differences between domestic and foreign production processes include:

• Melting:

  Foreign producers use non-vacuum induction furnaces with nitrogen degassing and bottom pouring, resulting in fewer defects and stable ingot quality.

  Domestic producers mostly use vacuum melting with tilting ladles, which tends to introduce gases and oxidation, leading to porosity and slag inclusions.

• Hot Rolling:

  Foreign mills have higher rolling force, allowing for large ingots and fewer passes with good temperature control, resulting in tight tolerances.

  Domestic mills have lower rolling force, smaller ingots, more passes, and poor temperature control, leading to wide tolerance ranges.

• Heat Treatment:

  Foreign producers use bright annealing furnaces with gas protection and air-float quenching, achieving bright surfaces and stable mechanical properties.

  Domestic producers mostly use resistance or box furnaces without protection gas, leading to unstable properties.

Nonetheless, in recent years, China’s beryllium copper industry has made significant technological progress. Many large copper alloy manufacturers have improved their processing technology and equipment, enhancing product precision, appearance, and mechanical stability. Several domestic materials are now developed to replace C17200 and C17300, with successful market adoption.

3. Application Prospects of Beryllium Copper in Electrical Connectors

Electrical connectors are widely used fundamental components for electronic and electrical systems. Their separability distinguishes them from other components. The key part of a connector is the contact, which ensures the reliable transmission of electrical signals. Without reliable contacts, a connector loses its function.

The selection of contact materials should focus on performance, considering elastic limit, modulus, strength, elongation, and fatigue resistance. In design, to prevent bending loss during plug-in of rigid pins and ensure reliable mating without permanent deformation or stress relaxation, high-strength, high-elasticity beryllium copper like QBe2 is typically used.

The authors believe that with material advancement, free-cutting QBe1.9-0.4 will gradually replace QBe2 and see broader application.

However, beryllium is toxic and expensive, and Pb used in free-cutting grades poses additional environmental and health hazards. Be and Pb dust generated during production are highly dangerous and incurable, and the strict manufacturing requirements further drive up costs, which limits its application in civilian electrical connectors.

4. Conclusion

Beryllium copper alloys are already widely used in military electrical connectors. Whether free-cutting grades can be widely adopted in the future remains a key research topic. At the same time, due to environmental and cost considerations, finding alternative materials for civilian electrical connectors will also be a major focus of future research.

Authors:

Hou Jinqiu, Wang Yinglin, Sun Haihang, Han Jixian, Jiang Ruizhi, Hao Jiannan

Shenyang Xinghua Aviation Electric Co., Ltd.

Third Military Representative Office of the Air Force Equipment Department in Shenyang Region