| abstract |
To achieve good solder performance with Pd-free solder to a BGA design, a layer assembly comprising first, second and, optionally, third sub-layers is provided, wherein said first sub-layer comprises a first material, said first material comprising nickel and phosphorus and said first sub-layer being in contact with said second sub-layer; said second sub-layer comprises a second material, said second material comprising palladium and phosphorus and said second sub-layer being in contact with said first sub-layer and said third sub-layer and wherein said second sub-layer is at least 0.1 µm thick; and said third sub-layer comprises a third material, said third material consisting of gold or a gold alloy and said third sub-layer being in contact with said second sub-layer. Such layer assembly is coated to the copper structure which is provided on one or on both sides of the carrier corpus of a circuit carrier. |