The term sperm implantation is actually incorrect and we suppose it refers to egg fertilization. What implants is the embryo after the sperm reaches the egg, and they fuse together. After that, the resulting embryo travels through the Fallopian tube toward the uterus. Once there, it will adhere to the endometrial lining, which is what we know as embryo implantation.
You can learn more about this process here: Sperm's journey to the egg.