iPadOS 8.4 (build 12H143) is an official Apple over-the-air update for the iPad mini 3 (Cellular), released on 2015-06-30T15:51:15Z. The update package is 392.4 MB. This is a delta (partial) update that requires 8.2 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 46f4bd97ed8288795ee5a6e9ad408115a9207913.zip.