How to solve Pogo pin head hanging tin？
During the test, the Pogo pin needle often comes into contact with the solder balls or pins, and the tin-hanging condition inevitably occurs. The current method to solve this problem can be effectively controlled by changing the coating material of the needle.
Regarding the coating of Pogo pin needles, most of the materials currently used are Au materials. The adhesion of Au to Sn is relatively strong. To solve the problem of material characteristics, Pdco materials can be used instead of Au. Pico is also the same. It is also a kind of precious metal. Compared with gold, it has the following material properties.
(1) Hardness
Pico has a hardness of 450HV
The hardness of Au is 200HV
The surface hardness of Pdco is higher than that of Au, which makes Pdco have better wear resistance than Au
(2) friction
The friction coefficient of Pdco is .40
The friction coefficient of Au is .65
The lower coefficient of friction can help the needle move more smoothly in the tube wall
（3）Particle size
Pdco size is 50-150 Angstroms
The particle size of Au is 200-250 Angstroms = 0.000000000001 meters
Small particles are more difficult to cause surface oxidation
(4) Toughness
Pico: 3-7% elongation
Au: <3% elongation
Stronger surface toughness Under the collision of the needle and the contact, the surface is less prone to cracks.
From the above data, it can be seen that Pdco is superior to Au in terms of material properties. But all materials are not perfect. The most important aspect of resistance is that Au is higher than Pico!
(5) Resistance (data obtained with the same number of times of use under the same needle, different plating test environment)
Au 19mΩ
Pico 26mΩ
If you encounter products that are more sensitive to impedance data, the test yield of Au is lower than that of Pico.
To sum up, aiming at the respective characteristics of Pdco and Au. KITA has developed a new coating alloy that combines the properties of the two materials 2-2
In terms of electrical resistance, the data of alloy 2-2 is very close to the data of Au, and at the same time it can get the same tin-free characteristics as Pdco, and the hardness of the material is higher than that of Au and Pico.
Contrast hardness:
The hardness of Alloy2-2 is 680HV
Pico has a hardness of 450HV
The hardness of Au is 200HV
In Alloy 2-2, 4 layers of gold are covered based on raw materials to achieve the required performance.
Therefore, the new alloy 2-2 coating can be used to effectively improve the problem when the degree of tin hanging is relatively high. For more information about 2-2, please contact the engineer.