Common Materials used for Spring Contacts
The choice of the base materials for each component of a spring contact or test probe is dependent on the performance demanded of each individual component, as well as the final assembled product.
PLUNGERS AND BARRELS
Phosphor Bronze is a choice for barrel material due to its excellent wear property. Brass is a very good electrical conductor, easy to machine and will accept all plating types. Nickel Silver proven as a good electrical conductor and provides excellent dimensional repeatability.
HyperCore™ is a base material offered by Xcerra which provides you with longer life as there is no plating required. It offers high durabiity for plungers also offers very good chemical resistance, and has a hardness range of 400 - 600 HV, which prevents contamination build up on points and edges. It is ideal for aggressive tip styles, and is only used on semiconductor probe styles.
Brass is sometimes used for passive tip styles and for machined barrels. The high percentage of copper makes it an ideal electrical conductor. Brass, however, is too soft for aggressive tip styles.
Steel is used for practically all aggressive tip styles, and provides a high degree of hardness and sharpness of the points and the flanks. This ensures good durability and reliable contacting.
BeCu (Beryllium Copper) is used because it is an excellent electrical conductor and is easily machined and hardened. Stainless Steel provides a much harder base material and is mainly used on medium to aggressive tips styles to provide longer lifetime.provides a good combination and compromise between brass and steel: The high percentage of copper makes it an ideal electrical conductor and the small percentage of Beryllium allows the base material to be hardened (up to 435 HV). This ensures good durability and optimises the aggressiveness of the plunger tip.
Nickel silver (NiAg) and bronze are mainly used for receptacles and the barrels of the test probes. These materials have a high tensile strength, which is ideal for the long-term life of test probes. Furthermore, these materials provide elasticity to the crimps on the receptacles. Spring steel of the highest possible quality is used for the manufacturing of the springs.
Environmental Plating materials are used to plate spring contacts and test probe components. The plating choices depend on which functional features are required.
Hard Gold provides excellent electrical performance for low-resistance applications, and provides the a very high level of chemical resistance. Gold typically has a hardness range of 150 - 200 HV, and is resistance to oxidation.
Rhodium is a very hard corrosion resistant plating material. It is a preferred plating when maximum tip life is preferred.is extremely resistant to abrasion, has a hardness range of 600 - 1000 HV, but it is very brittle. Therefore, this plating material is not suitable for aggressive tip styles in conjunction with high spring forces. Rhodium is used when plunger tips are required to be especially durable.
Chemical Nickel is a relatively hard plating and is used on probes as a barrier plate, and for its very good chemical resistance. Nickel only plating is not as conductive as the precious metals and is generally a low cost method of plating.
Primeguard is a very hard plating option offered by Xcerra and is only used on Semiconductor probes to extend life and cleaning cycles on 100% tin or palladium based applications.
Aurun is a gold-alloy plating material which was developed by Ingun especially for test probes, has very good chemic resistance
and a hardness range of 300 - 350 HV. It is used for aggressive
tip styles to test unwashed PC boards.
All plating materials guarantee the best contacting reliability due to their very low, specific resistance values.
LFRE is aproprietary hard plating alloy offered by Xcerra. Used on lead-free (RoHS) PCB boards and contact points. Approx. 5 times harder than gold plating to extend tip lifetime. Less prone for solder transfer on 100% Tin applications.
Stainless Steel is used for high and low temperature ranges, certain high-alloyed spring steels (i.e. stainless steel) are used.
WIRE GAUGE REFERENCE
American Wire Gauge (AWG) Cable / Conductor Sizes and Properties
[Ohms / 1000 ft]
[Ohms / km]
| Max Current
for 100% skin depth
|0000 (4/0)||0.46||11.684||107||0.049||0.16072||302||125 Hz|
|000 (3/0)||0.4096||10.40384||85||0.0618||0.202704||239||160 Hz|
|00 (2/0)||0.3648||9.26592||67.4||0.0779||0.255512||190||200 Hz|
|0 (1/0)||0.3249||8.25246||53.5||0.0983||0.322424||150||250 Hz|
|16||0.0508||1.29032||1.31||4.016||13.17248||3.7||11 k Hz|
|17||0.0453||1.15062||1.04||5.064||16.60992||2.9||13 k Hz|