What is BS EN IEC 60749-4 - Damp heat, steady-state, HAST of semiconductor devices about?   
BS EN IEC 60749 is an international standard covering damp hear, steady-state, HAST of semiconductor devices, ensuring stable operability, and longevity in semiconductor applications.
BS EN IEC 60749 provides a highly accelerated temperature and humidity stress test (HAST) for the purpose of evaluating the reliability of the non-hermetic packaged semiconductor devices in humid environments.
Who is BS EN 60749-4 - Damp heat, steady-state, HAST of semiconductor devices for?  
BS EN 60749-4 on damp heat, steady-state, highly accelerated stress test is relevant to:  
- Semiconductor device manufacturers
- Dealers and importers of semiconductor devices
- Manufacturer of electronic devices
- Product design engineers
- Automobile industry
- Electrical engineers
Why should you use   BS EN 60749-4 - Damp heat, steady-state, HAST of semiconductor devices?   
Semiconductor devices are electronic components that rely on the electronic properties of semiconductor materials for their function. They are usually made of semiconductor materials such as silicon, germanium, and gallium arsenide for their function.
BS EN 60749-4 provides users guidance on HAST test that employs severe conditions of temperature, humidity, and bias that accelerate the penetration of moisture via external protective material or along with the interface between the external protective material and the metallic conductors, enabling users to assess the operability in different atmospheric conditions.
The test methods provided under BS EN 60749-4 helps users to avoid any mechanical damage such as cracking, chipping, or breaking that leads to overall product/application failure.  
Test apparatus requirements, test conditions are described in BS EN 60749-4 helps users in maintaining a specified temperature and relative humidity continuously while providing electrical connections to the devices.
According to the failure criteria specified in BS EN 60749-4, a device is regarded to have failed the highly accelerated temperature and humidity stress test if parametric limits are exceeded or functionality cannot be shown under nominal and worst-case conditions.
Overall, BS EN 60749-4 can help users to minimize the release of contamination, degradation due to corrosion and other mechanisms and maintain operational efficiency and the service life of the end application.  
What’s changed since the last update?  
BS EN 60749-4:2017 supersedes BS EN 60749-4:2002, which is withdrawn.   BS EN 60749-4:2017 includes some technical changes with respect to BS EN 60749-4:2002. This includes:  
- Clarification of requirements for temperature, relative humidity, and duration detailed in Table 1
- Recommendations that current limiting resistor(s) be placed in the test set-up to prevent test board or DUT damage
- Allowance of additional time-to-test delay or return-to-stress delay
