Accelerated life Testing

With well-designed reliability testing the behavior of products and materials under different operation conditions can be verified, and life-cycle of the products can be estimated.

Thermal testing

Temperature – high, low or temperature change – has huge effect on the reliability of products.

      • High temperature accelerates chemical reactions and ages materials
      • Low temperature may cause the materials to become brittle
      • Thermal cycling adds the effect of stresses caused by materials having different coefficient of thermal expansion (CTE) values.

Examples of test methods:

Thermal cycling and thermal shock cause cyclic thermomechanical stresses to interconnections, components and devices and is widely used with electrical devices. Thermal shock, with quicker temperature change rate, causes also thermal gradients.

Thermal aging can be used to analyze aging and behavior of devices and materials under high temperatures for short or long time periods. It is commonly used in lifetime estimation testing.

Humidity testing

Humidity impairs performance of many polymers and in electrical structure may cause for example swelling, delamination, corrosion and popcorning.

Humidity testing often combines elevated temperature and humidity conditions, in which temperature accelerates the effect of humidity. Products are, for example, often exposed to similar environments during transportation and storage.

Examples of test methods:

Thermal cycling and thermal shock cause cyclic thermomechanical stresses to interconnections, components and devices and is widely used with electrical devices. Thermal shock, with quicker temperature change rate, causes also thermal gradients.

Thermal aging can be used to analyze aging and behavior of devices and materials under high temperatures for short or long time periods. It is commonly used in lifetime estimation testing.

Mechanical testing

Mechanical testing studies how mechanical stresses affect structures. Typical stresses are various impacts for example due to dropping and different types of vibrations. Additionally, dynamic methods, for example, stretching, bending and torsion testing, can be used to analyse mechanical properties.

Several test methods can be used for mechanical testing. For example vibration, drop and dynamic bending and stretching testing can be used.

Mechanical durability is affected by use conditions and consequently, combinatory testing can be used.

Corrosion testing

Corrosion testing is required when components are used in corrosive environments, such as marine or heavily polluted areas. Several different methods can be used to analyse the effect of different corrosive elements.

Examples of test methods:

Mixed flowing gas testing (MFG) is used to imitate atmospheric corrosion by various corrosive gases. We can test H2S, SO2, NO2 and Cl2 gases and simultaneously control temperature and relative humidity.

Salt spray testing is used to study the corrosion caused by salty environments. Examples of these are road salt or human sweat. Testing can be conducted with several different constant and cyclic tests and salt levels.

Flowers of Sulfur testing (FOS) is a test designed especially for the printed circuit boards used in harsh environments. The corrosive environment is achieved with sulfur powder, sodium hypochlorite, and salt solution. Consequently, harsh environment with sulfur and chlorine-bearing gases is achieved. To ensure constant corrosion rate samples are circulated in the chamber.

Corrosion rate monitoring. For all tests monitoring of the corrosion rate using silver and copper corrosion coupons is possible. This system offers further knowledge of testing and its effects.

Dust testing

Dust is often a reason for failures. It can cause for example overheating or prevent air ventilation. Additionally, dust may cause short circuits and corrosion.

Dust testing is used to study how different impurities affect the reliability of a product and how to design devices to minimise the effects of dust.    

Settling dust testing can be used especially for various electronics structures and devices. Several different dusts can be used including electrically conductive dusts and corrosive dusts.

 

Electrical testing

Electrical stresses are one of the major reasons for failures.

Electrical testing can be used to study how changes in supply voltage can affect the reliability of, for example, power electronics. These methods include under and overvoltage, voltage fluctuation and intermittent power failures.

 

Combinatory testing

In use conditions, your product seldom faces a single stress at a time. Therefore, combinatory testing can be used to combine several environments.

Combinatory testing can be performed using sequential testing (exposing the same tested structures first to one environment and then to another) or simultaneous testing (combining several environments at the same time).

The idea behind combinational testing is that stresses may significantly affect and accelerate each other. Therefore, the results of combinational testing are often more severe than the sum of two separate stresses.

A common example of combinatory testing is high humidity – high temperature testing. However, several other combinations may also be used to both accelerate testing and better imitate the use environments.

Real-time monitoring and data analysis

It is typical that the behaviour of products and devices changes before they fail in test conditions. Sometimes, products do not function in test conditions but seem to be fine after the test. Consequently, it is critical to measure the behaviour of the products during testing.

Monitoring the behavior in-situ gives a much better understanding for the behavior of products in test environments. This was major benefit compared to functionality testing at room condition in between tests can be achieved.

Data analysis of the real-time monitoring often provides crucial information for the early signs of failure and indication about failure mechanisms.

Design and manufacturing of test set-ups

Sometimes testing requires sophisticated electrical or mechanical test set-ups to ensure correct test conditions.

In mechanical tests it is typical that different jigs are needed to ensure suitable attachment of a product. For example, vibration testing often requires specifically designed jig and support.

Electrical measurements require also often specific set-ups for example, to ensure functionality and correct measurements during testing.