Solution to the reduction of test yield due to tin hanging on the top of pogo pin needle

　　During the test, the pogo pin needle often contacts with the solder ball or pin, which inevitably leads to tin hanging. At present, the method to solve this problem can be effectively controlled by changing the coating material of the needle.

　　In terms of the needle coating of pogo pin, most of the materials currently used are au materials, and AU has strong adhesion to SN. In order to solve the problem of material properties, PdCo materials can be used to replace Au. PdCo is also a precious metal, which has the following material properties compared with gold.

　　(1) Hardness

　　The hardness of PdCo is 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) Rub

　　The friction coefficient of PdCo is. 40

　　The friction coefficient of Au is. 65

　　The lower friction coefficient can help the needle move more smoothly in the tube wall

　　(3) Particle size

　　The size of PdCo is 50-150 angstroms

　　The particle size of Au is 200-250 angstroms angstroms = 0.0000000001 M

　　Small particle materials are more difficult to cause surface oxidation

　　(4) Tenacity

　　Pdco：3-7% elongation

　　Au：<3% elongation

　　Stronger surface toughness. Under the collision between the needle and the, the surface is less prone to cracks.

　　From the above data, it can be seen that PdCo is better than AU in material properties. But all materials are not perfect. The most important aspect of resistance is that Au is higher than PdCo!

　　(5) Resistance (data obtained by using the same needle for the same number of times under different coating test environments)

　　Au 19mΩ

　　Pdco 26mΩ

　　If a product sensitive to impedance data is encountered, the test yield of Au is lower than that of PdCo.

　　To sum up, according to the respective characteristics of PdCo and Au. Kita has developed a new coating alloy 2-2 combining the characteristics of the two materials

　　In terms of resistance, the data of alloy 2-2 is very close to that of Au. At the same time, it can obtain the same characteristics without Tin hanging as PdCo, and the hardness of the material is higher than that of Au and PdCo.

　　Comparative hardness:

　　The hardness of alloy2-2 is 680hv

　　The hardness of PdCo is 450hv

　　The hardness of Au is 200hv

　　Alloy 2-2 is covered with 4 layers of gold on the basis of raw materials to achieve the required properties.

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