The needle and material are generally selected as Becu or SK. Both have advantages and disadvantages. Becu has good conductivity, but lacks hardness, and SK has high hardness, but it is easy to rust.
Spring, is also more important, SUS SWP, especially now that there are more and more PB free products, it directly causes the pins or BGA solder balls to become soft or hard. During the test process, it was found that the original yield was very high, After changing the solder ball or lead material, the yield rate is extremely poor. The choice of spring pressure is very important. The test environment has very strict requirements on the material of the spring. The high and low temperature test directly affects the working life of the probe.
There are many needles and materials to choose from, and PB materials are generally used.
The main reason for the low yield may be due to the increase of impedance during the test of the probe.
The increase in impedance is mostly caused by the wear of the needle during the test, the damage of the coating, and the tin hanging of the needle.