The chip utilizes a Ball Grid Array. (BGA) Each dot is a contact. To attach it to the board a special solder/flux ball is placed on each contact. The chip is then placed on the board by a robot and heated with air hot enough to melt the solder. When it works it will result in a nice solid connection. When it fails it won't. The problem is that many times it will work fine during testing and for a period of time after. Once the connection breaks then you will either get intermittent problems or sudden failure. A common do it yourself fix for a circuit board with a failed BGA chip connection is to put it in an oven at around 400 degrees for 5 to 10 minutes to remelt the solder. This was a common fix on the HP LJ 3005. To properly fix this problem the chip has to be removed from the board, the solder balls are removed and replaced with new ones and then re attached to the board and baked. This obviously will never happen on airpods as it would be more expensive to repair then to just scrap the entire device.