Almost all of the handsets especially smartphones heat up when they are used for a longer time. Some smartphones may heat up much more than the others, there are many reasons that might lead to the heat build up.
There are 4 main reasons why your handset may be heating up too much.
In very few cases it will be linked to a hardware defect. In most cases you might immediately notice it even with normal usage and mostly likely within the first few days of buying the handset. This means you an easily get a replacement and that is what you should be doing. And in a very rare case the hardware may fail ultimately lead to heat up i.e. after few months or years.
The smartphones today are like a mini computers, the moment you get it, you will start downloading new apps and games. Some apps may not be properly optimized and may even be working in the background (almost all handsets supports multitasking). This could lead to heat up. So you need to watch out for the apps you are installing and if you find abnormal performance / heat up remove the last app that had installed.
Keeping the Wi-Fi, GPS or even data networks on when not required may lead to heat up. Take the example of GPS, the moment you start using the handset the GPS will try getting a lock and if you are indoor it will never happen. Same goes with the Wi-Fi, it will keep checking for new Wi-Fi networks in case you are not connected.The best bet is to disable these features when not required. It will not only reduce heat build up but also improve battery backup.
Many smartphone users don’t realize that surrounding temperature plays a very important role in the smartphone performance and heat build up. Also since the smartphone is a portable device it moves with you wherever you go.
What happens to your body when you are in a hot or a cold environment, well in hot environment you get hot, start sweating and when in a cold environment you get cold, start freezing. The same rule applies to any gadgets you may be using. In cold environment the smartphone will hardly heat up and in a hot environment it will get hotter much faster. The maximum comfortable smartphone temperature is 48 to 50 degrees.
Now imaging you are in a room with 23 degree temperature the handset will not heat up much probably the max temperature might be between 38 to 48 degrees. Now if you perform the same task as you did in the 23 degree environment; outdoor in 35 to 45 degree temperature you cannot expect the same temperature rise, heat build up will be much faster and might reach over 48 degrees in a matter of minutes.
Using the camera outdoor (under direct sunlight) will also make the handset heat up faster. The best option would be to avoid using the handset outdoor in extreme heat, unless necessary.
When you buy a new handset..
Use it without installing any applications for few days to get an idea about the performance and heat-up. If you feel it’s good you can go ahead and start installing the applications, but do keep track of the apps that you have installed recently, just in case if you face any issues later on.
Facing some other issues check this out – Android trouble shooting guide.