Electrode structure and its manufacturing method, and semiconductor module
There is a highly reliable semiconductor module having a satisfactory bonding strength in the electrical bonded portion. In the semiconductor module 10 , a semiconductor chip 11 is mounted on a circuit board 20 . In the circuit board 20 , on an insulating ceramic substrate 21 is formed a metal circuit plate 22 on which the semiconductor chip 11 is implemented. The semiconductor chip 11 and metal circuit plate 22 are connected with each other by an aluminum bonding wire 23 . In the connected portion between the metal circuit plate 22 and bonding wire 23 , a coating layer 24 for excellent conjunction therebetween is mounted. The coating layer 24 , as shown in an enlarged diagram, is made up of a nickel (Ni) layer 241 , a P-distributed palladium (Pd) layer 242 , and an Au layer 243 in increasing order. To the P-distributed Pd layer 242 is added P (phosphorous) and, the P concentration on the Ni layer 241 is higher than that on the Au layer side 243.
1. An electrode structure comprising:
a coating layer having a nickel (Ni) layer, a palladium (Pd) layer having phosphorous (P), and a gold (Au) layer sequentially stacked on a metal circuit plate containing Ag, wherein an average P concentration in the Pd layer is in a range of more than 2.6% by mass and not more than 6.0% by mass and wherein the P concentration on a side being in touch with the Au layer in the Pd layer is higher by 1.5% or more by mass than that on a side being in touch with the Ni layer in the Pd layer.
2. The electrode structure according to claim 1 , wherein the Pd layer has an amorphous structure.
3. The electrode structure according to claim 1 , wherein P has been doped to the Ni layer.
4. The electrode structure according to claim 1 , wherein a thickness of the Pd layer is greater than 0.05 μm and less than or equal to 0.2 μm.
5. The electrode structure according to claim 1 , wherein a thickness of the Au layer is greater than 0.05 μm and less than or equal to 0.2 μm.
6. A circuit board wherein the electrode structure according to claim 1 is formed on a ceramic substrate.
7. A semiconductor module wherein a semiconductor chip is mounted on a circuit board stated in claim 6 and the semiconductor chip is electrically connected to the electrode structure.
8. The semiconductor module according to claim 7 , wherein the electrical connection is achieved by a bonding wire.
9. The semiconductor module according to claim 8 , wherein a material for the bonding wire contains any one of aluminum and gold as its main ingredient.
10. The semiconductor module according to claim 8 , wherein the bonding wire is connected to the electrode structure by ultrasonic bonding.
11. The electrode structure according to claim 1 , wherein the Pd layer is thicker than the Au layer.
12. The electrode structure according to claim 4 , wherein a thickness of the Pd layer is greater than or equal to 0.1 μm and less than or equal to 0.2 μm.
13. An electrode structure comprising:
a coating layer having a nickel (Ni) layer, a palladium (Pd) layer having phosphorous (P), and a gold (Au) layer sequentially stacked on a base electrode containing Ag, wherein an average P concentration in the Pd layer is in a range of more than 2.6% by mass and not more than 6.0% by mass and wherein the P concentration on a side being in touch with the Au layer in the Pd layer is higher by 1.5% or more by mass than that on a side being in touch with the Ni layer in the Pd layer.
14. The electrode structure according to claim 13 , wherein the Pd layer has an amorphous structure.
15. The electrode structure according to claim 13 , wherein P has been doped to the Ni layer.
16. The electrode structure according to claim 13 , wherein a thickness of the Pd layer is greater than 0.05 μm and less than or equal to 0.2 μm.
17. The electrode structure according to claim 13 , wherein a thickness of the Au layer is greater than 0.05 μm and less than or equal to 0.2 μm.
18. The electrode structure according to claim 13 , wherein the Pd layer is thicker than the Au layer.
19. The electrode structure according to claim 16 , wherein a thickness of the Pd layer is greater than or equal to 0.1 μm and less than or equal to 0.2 μm.