- They are the residues of the manufacturing process. At the beginning, there are many pins on one single metal sheet. Then it dies, and the casings are installed on the pins. At last, these pins are cut into single ones, and this process leaves the bumps on the pins.
- Besides, they are designed like this to protect the LED. If the LED flushes against the PCB when the temperature is high, the LED may split. This is because the CTE of epoxy and PCB is different, so the contact part will be under stress and thus damaged.
More reading: About LED Light Assembly You Have to Know