Beryllium Copper Strip
Performance of Beryllium Copper
(1) Spring Properties and Downsizing
Beryllium Copper is the ideal spring material because of its high mechanical strength and favorable elastic modulus.
The elastic modulus is a common term for the modulus of longitudinal elasticity and is also known as Young's modulus. This value is the slope of the linear portion of the stress-strain curve obtained by a tensile test. Elastic modulus can also be measured directly in the case of a thin flat spring.
Fig. 1 shows the formula for surface stress and spring load in cantilever system. Elastic modulus is one of the important constants for designing contact springs for connectors and switches. In general, if the value is too large, contact force varies greatly with a slight movement of a contact. On the contrary, if it is too small, required contact force cannot be obtained.
Since the ratio of yield strength to Young's modulus of beryllium copper is greater than stainless steel and phosphor bronze, larger displacement and higher contact force can be obtained.
Fig. 1 Surface Stress and Spring Load in Cantilever System
Making full use of beryllium copper spring properties, we can downsize a phosphor bronze spring part while the contact force remains the same. This may also lead to downsizing of plastic parts or terminals around it, thus, we can expect cost saving in total.
Due to the high tensile strength up to 1,500N/mm2, beryllium copper is used to reduce the pitch of contact arrays without deterioration of spring performance. A connector in a given housing space can be designed to a higher density than with any other copper alloy. In conclusion we can reduce the cost per pin compared to phosphor bronze.
Fig. 2 Downsizing of Battery Contact
Fig. 2 shows an example of downsizing in the design of a battery contact using Beryllium Copper. Due to the reduction of material input and surface area to be plated, total cost compared with phosphor bronze can be lower.
|Part weight (g)||1.14||0.14|