Download document () of 20
Send email
Download
You have exceeded the download limit
How hot is too hot? the real maximum temperature of your product
Maximum touch temperature is an important aspect to consider in the end user experience. In the summertime, it’ll be much easier for devices to reach that maximum touch temperature. As thermal designers, we need to account for that.
The maximum allowable temperature of your device relies on a variety of factors such as the environment, your product design and application and how you expect your users to handle your product. Let’s walk through these different parameters to get to the core of maximum temperature.
Touch temperature is based off the limitation of human skin. Human skin can bear some higher temperatures for brief periods of time before pain and cellular damage can set in. These two limitations, pain and damage, are the last things users want to experience. NASA put out an excellent summary of a new approach to touch temperature. NASA conducted empirical data and research on previous studies to develop their own mathematical model of what temperatures are allowable for skin constant contact. Essentially, our pain threshold for heat depends on what area of the skin is heated, but in general that ranges between 42°C (sensitive skin the chest area) to 45°C (on our feet).
Ecma International also specified material type in this table since maximum touch temperature is also influenced by material. Materials with high thermal conductivity are able to quickly transport heat through conduction. The time it takes heat to transfer to skin from a metallic surface compared to plastic is significantly shorter. Since it takes longer for heat to transfer, skin can endure longer periods or higher temperatures with less conductive materials, effectively increasing the allowable touch temperature.
Now that we have an external maximum temperature based off what end users can handle comfortably, we can calculate backwards to our maximum device temperature. If your user is in direct contact with your heat sink for your device, your maximum device temperature is easy to determine.
In some products, your device will be enclosed in a case and dissipating heat is a little more difficult. You need to cool your device for performance and reliability, but you need to do so safely and compromise the user experience with your product. You might need a more complex study in the case of an enclosure. Eaton engineers are well-versed in studying thermal transfer within enclosures and can help you out. Reach out to our design engineers if you’re in need of more help.
MyEatonFAQs
