Q+A: What is (Still) Causing Electronic Devices to Overheat?

phone with thermometer

Recent reports about new iPhone 15s overheating when running apps like Instagram and Uber have spurred Apple to release a patch in its next operating system to address the issue. While this issue is rooted in a different problem than the battery malfunction that in 2016 caused Samsung Galaxy phones to dangerously overheat, the challenge of managing heat in electronic devices persists, particularly as technology becomes increasingly sophisticated.

Ioannis Savidis, PhD, a professor in Drexel University’s College of Engineering, is looking at design strategies to manage power consumption in electronic devices to maximize efficiency and mitigate overheating. His lab is developing circuits that can dynamically adjust to a changing workload distributed across computing cores so they can maintain a high level of performance without becoming overloaded, which can lead to diminished performance and failure.

The work of Savidis’ Integrated Circuits and Electronics Lab is guiding the integration of complex circuits that will enable the development of smaller and more powerful devices, where thermal management is critical for operation. Savidis recently shared his insight on the iPhone’s current overheating challenges and how engineers are working to keep heat in check.

Apple is reporting that running certain third-party apps – including Instagram and Uber – can cause their new iPhone 15s to overheat. Why might running an app or piece of software cause hardware to overheat?

Hardware and software are interlinked in our devices. So, when you run software on a phone or laptop, you’re actually running the programs or applications on hardware powered via integrated electric circuits.

These circuits have transistors on them, and the transistors require an electric current to operate. The electrical current that is required varies based on the application, because certain applications require more transistors to execute its operations.

For applications, like Instagram or Uber, the active transistors may have to draw a greater amount of current, or operate over a longer period of time – either of which can cause them to heat up due to the natural resistance of an electric current moving through circuits. This is what causes phones and laptops to warm or, in some cases, get so hot that built-in protective measures are employed to actually shut them down.

How does this overheating differ from battery overheating (which has previously caused problems with Samsung’s Galaxy smartphones)?

This overheating differs from the troubles we saw with Samsung Galaxy phones a number of years ago as that issue was related to the design of the batteries in the phones.

Although there is a concern when designing batteries that the demand for power can cause it to operate at a high level for a long period of time, the issue with the Samsung batteries back in 2016 was an error in the design of the positive and negative terminals of the batteries. Two of the battery suppliers Samsung used for the Galaxy Note 7 had issues with the electrodes, which resulted in short circuits, overheating, and battery fires.  For the battery design of one supplier, the curvature of the phone was not properly accounted for, and therefore, caused shorting between the positive and negative terminals, while the other supplier did not provide adequate insulation between the two terminals of the battery.

How is heat typically managed in computing technology like phones and laptops? What sorts of strategies are used to prevent devices from overheating?

There are a number of strategies being used for thermal management in electronic devices. Physical techniques are available, such as heat distribution across material that absorbs and disperses heat – specifically, a heat sink. Fans are used in laptops and desktops to cool the hardware when executing a computing workload.

But in phones, since it’s a little bit more of a tight space, there isn’t as much room to include a large fan to increase air flow through the device.  So instead, phones use active power management techniques. 

One such technique is to distribute the workload among a set of computing cores so that no one area of the circuit bares the entire load.

Another technique uses built-in power and thermal sensors to detect when a core is overheating, and then reduces the amount of current being drawn by the core by lowering the voltage and/or frequency that the core is operating at. You could think of it like shifting gears on a bike when it gets hard to pedal, so you don’t wear your legs out.

The patch Apple is releasing to fix the overheating problem likely includes an adjustment to the power management system of the phones – either reducing the frequency of use or the voltage set for the computing cores, both of which will lower the peak power level drawn by the phones.

Why is thermal management still a problem in new devices?

The thermal management of devices is always a challenge, more so for size-constrained devices such as cellphones, where the thermal design point is much lower than a laptop or desktop.

For these devices, even the design of the heat sink — the material that dissipates heat within the device — is critical. If the phone is designed differently than prior generations, or the heat sink material used for a particular device is changed, the thermal operation may vary.

Different materials have different thermal properties. Some are better at spreading heat than others, and others are better, depending on the dimensions being used. As an example, for the iPhone 15 Pro, the material for the case was changed to titanium.

Ultimately, if you change materials for the heat sink and actual body of the phone, it can affect the thermal properties of the device — which is not necessarily a problem, as long as this has been accounted for by adjusting the power and thermal management systems accordingly.

What amount of heating is normal for a device? 

While it depends on the type of device and the actual thermal management system, the generally accepted operating temperature for the integrated circuits included in commercial electronics is 80-85 C.

Devices can still operate above this temperature, but the design goal is to maintain this range during peak operation, so any temperature above this range could result in diminished performance and a reduction in the lifetime of the circuit. Note that this is not the temperature of the phone itself, which should be much lower, but rather, the computing cores included in the brains of the phone. 

For the iPhone 15 Pro, people are reporting that their phones are running between 105-120 F — that is what you’re feeling on the outside of the device. But this means the cores are operating at a much higher temperature inside, because that heat is being dissipated through the package of the cell phone.

How can overheating affect the performance of a device – both in the short and long-term?

Overheating in the short term can potentially cause errors in the execution of an instruction, which causes the app to operate incorrectly. While there is some margin for overheating, there is no guarantee that an app will work properly if the computing cores are operating outside of the maximum permitted heat range. This is not necessarily happening with the iPhone 15 Pro as we know that the maximum temperature of the cores is not the same as the temperature felt on the outside of the device.

If phones are running at temperatures above what the circuits are designed for, in the long term it can reduce the lifetime of the device, as the circuit is potentially being physically damaged in the process.

Reporters interested in speaking with Ioannis Savidis should contact Britt Faulstick at bef29@drexel.edu.