The Best of Both Worlds (1) - S3-E26
Question: I can't tell if this was a mistake or if there's an explanation. When the Borg are on the Enterprise's bridge, the first two are covered in the green light indicating they're being transported back to the Borg ship, but the 3rd one (the one successfully shot by Worf) has no lights, he just fades away. Why?
Answer: The Borg use technology to cause the dead to disintegrate, presumably as a security measure to prevent their technology from being captured.
But in s05e23, "I, Borg", Riker says "the Borg collect their dead" when they encounter the injured Borg. Worf says to kill it and leave no evidence they were there so that when the Borg return to collect the dead member. Plus, there were 4 dead Borg and none of them disintegrated.
Bishop73
I believe "collect" refers to the disintegration. We see other Borg remove specific pieces of technology from the dead borg, which causes it to disappear.