The logic board is the brain of the operation in your iPhone. It contains the processor, memory, and other controllers. It’s the part of your phone that makes the other parts of your phone work. Therefore, when there’s a problem with your logic board, it’s a serious one. iPhone 8 owners may have noticed their phones misbehaving. The devices might lock up or restart without cause. These aren’t your average iOS 11 bugs, they’re a sign of something more serious.
If you bought an iPhone 8 (not an iPhone 8 Plus) between September 2017 and March of 2018, you may be eligible for a free repair. Head over to Apple’s repair page to enter your serial number. If Apple determines that there’s an issue with your phone, you’ll be able to have them repair it.
Source: Roger Fingas, AppleInsider