Actual disassemble and temperature test iPhone X, revealing hidden technology highlights!

The iPhone X, Apple's flagship device celebrating the 10th anniversary of the iPhone, has captured global attention with its groundbreaking design and innovative features. During the recent "Black Friday" weekend, it sold an impressive 6 million units in the U.S., highlighting its immense popularity. As a thermal design engineer, I conducted a hands-on disassembly and temperature testing to analyze the hardware’s thermal management system. **Machine Architecture** The iPhone X follows a similar two-piece structure to the iPhone 8 and 8 Plus, with the motherboard and battery sandwiched between the display and back cover—resembling a layered structure. This layout is visually represented below. **Two Heat Transfer Paths: Screen and Back Cover** A double-layer graphite sheet, measuring 0.1mm in thickness, is attached to the inside of the screen for heat dissipation. The screen acts as one of the primary heat transfer paths, with a thin-wall heat transfer capacity of 0.06 W/K. This value is calculated based on standard thermal conductivity formulas discussed in previous analyses, such as the “iPhone 8 Cooling Solution Analysis.” On the back cover, the design mirrors that of the iPhone 8: a glass layer combined with a steel plate. A central hole accommodates the wireless charging coil, and a copper foil graphite layer is placed over it. The copper foil overlaps the aluminum plate by 2mm to maintain even heat distribution around the hole. However, due to the steel plate's minimal thickness (0.15mm), its heat transfer capability is very limited, at approximately 0.02 W/K. Compared to other smartphones like the Maimang 5, the iPhone X’s back cover has significantly weaker heat dissipation, about 1/9th of the latter’s capacity. **Motherboard Design** The top surface of the motherboard, near the screen, has a small graphite sheet attached to the shield cover. This graphite helps transfer heat from the CPU to the SIM card slot. However, its limited size (around 40mm long) and narrowest point (only 4mm wide) restricts its effectiveness. On the bottom side of the motherboard, a large single-layer graphite sheet (45mm x 25mm x 0.07mm) covers the entire area. This sheet helps spread out hot spots from the CPU, reducing localized heat concentration. One of the most notable innovations in the iPhone X is its two-layer motherboard, which reduces the footprint by 30% compared to the iPhone 8 Plus while increasing component density by 135%. Although this design allows more components to be packed into a smaller space, it lacks a traditional thermal solution for the CPU. Typically, CPUs are connected via TIM (thermal interface material) to either a middle plate or the back cover for heat dissipation. Without this, the CPU may run hotter, potentially reaching up to 85°C during intensive tasks like gaming. However, Apple’s closed iOS system doesn’t allow users to monitor internal temperatures directly, so we focus more on surface temperatures instead. Despite this, the iPhone X’s thermal performance during testing showed some shortcomings, especially in terms of surface temperature uniformity. **Cooling Capacity Comparison** To better understand the iPhone X’s thermal performance, I compared its heat transfer capabilities with two well-designed smartphones: the Samsung C7 and the Maimang 5. The results are summarized in the chart below. **Test Verification** During a one-hour session of playing “King of Glory” at high frame rates in an ambient temperature of 25°C, the maximum surface temperature of the iPhone X’s back cover reached 44°C, with a 7°C difference between the hottest and coldest spots. This uneven temperature distribution suggests that the cooling system could be improved, confirming the earlier analysis of its relatively weak thermal design. **Conclusion** While the iPhone X’s thermal design is not optimal and leaves room for improvement, it’s important to recognize that cooling solutions are part of a broader balance involving hardware architecture, cost, software optimization, and user experience. The iPhone X remains one of the best smartphones available, and its design choices reflect a thoughtful trade-off between performance, aesthetics, and functionality. This article aims to provide a detailed thermal analysis from a design perspective for readers’ reference.

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