U3101 Big Audio IC for iPhone 7/7 Plus/6s Plus/6s

Audio faults on iPhone 7, 7 Plus, 6s, and 6s Plus boards almost always trace back to one component: the U3101 Big Audio IC. Also labeled 338S00105 on the board, this chip acts as the audio codec, managing both speaker output and microphone input for the handset. When a customer brings in a phone with no sound on calls, dead earpiece audio, or a mic that stopped picking up voice during calls, this IC is one of the first things you check after ruling out the flex cables and connectors. You'll run into this fault pattern most often on liquid-damaged boards, since corrosion under the U3101 pins is one of the most common failure points on these logic boards. It also shows up after a bad software update or failed restore where the audio codec stops responding even though the rest of the board tests fine. In both cases, swapping the chip resolves the issue where cleaning and reflowing alone won't. This is a 144-pin BGA component, so installation is board-level work, not a connector swap. You need a hot air rework station capable of controlled reflow, a reballing stencil matched to the 144-pin footprint, and flux suited for fine-pitch BGA work. Preheating the board evenly before you touch the IC matters here — uneven heat on a board this dense risks lifting nearby components or warping the pads under U3101. If you're already running reballing kits for other iPhone-series ICs, this chip fits the same workflow with no extra tooling required. Before reballing, always check continuity on the board pads first. A shorted or lifted pad under the old IC can mimic an audio IC failure, and reballing a chip onto damaged pads wastes both the part and your time. Clean the site fully with flux and isopropyl alcohol, confirm the pads are flat and free of corrosion, then proceed with reballing using solder balls matched to the original pitch. Once mounted, test speaker and mic function directly — play a test tone through the earpiece and loud speaker, then record a short clip to confirm mic pickup on both the primary and noise-cancelling microphones where applicable. If the board still shows partial audio issues after a clean reball, check the flex cable and connector first before assuming a second IC fault, since flex damage produces similar symptoms. This part is compatible across iPhone 7, iPhone 7 Plus, iPhone 6s, and iPhone 6s Plus boards, since Apple carried the same audio codec design across these two generations. That shared compatibility makes it worth stocking in bulk if you handle repair volume across both models, rather than sourcing separately for each. For shops in Lahore, Karachi, and Islamabad running high-volume board repair, audio faults are a steady share of walk-in complaints, especially on older 6s and 7-series units still active in the market. Keeping this IC on the shelf means you're not turning away no-sound or no-mic repairs or waiting on a supplier reorder mid-job. Reballing your own boards instead of outsourcing to a chip-level shop also keeps your turnaround time and margins under your control.