How to Reduce Solder Joint Fatigue in Problematic Power Supp
There are several reasons why today’s power supplies can experience reliability issues, including solder joint fatigue as a top contributor. Space constraints and large components in a power supply can prove problematic for solder joints, along with thermal expansion issues that can occur during thermal cycling. To help effectively predict and mitigate potential solder joint fatigue in a device's power supply, an understanding of common problems that can arise, along with a proactive design and analysis strategy, can help conserve engineering resources and speed time to market.
Power supplies have several characteristics that can make them susceptible to solder joint fatigue, including:
1. Large components which can aggravate thermal mismatch between materials
2. Thicker boards, necessitated by the size and number of components, which can induce more strain on the solder joint
3. Very thick copper layers (some designs have up to 6 oz. in certain layers) which can result in a high copper-glass ratio, increasing the coefficient of thermal expansion for the printed circuit board
4. Extensive solid plane areas and embedded heat sinks, used to help remove heat from the board, which can add excess weight and strain
These characteristics can cause excessive stress and strain on solder joints, often leading to deformation and fatigue under thermal cycling. The rate of expansion and contraction of the solder joint itself, which often differs from the materials to which it is connected, can also play a large role in fatigue under thermal cycling. The level or extent of these strains can determine the lifetime of the solder joint.
By using Physics of Failure algorithms, along with the modeling and simulation capabilities of design analysis software, engineers can more efficiently predict the expected lifetime of solder joints under thermal cycling. The information gathered through analysis also provides a comprehensive device overview that can help evaluate potential weaknesses and provide solutions for a more reliable design. This information gives engineers the power to make more informed product design decisions before prototyping, in turn helping to reduce device lifetime warranty claims and speeding up time to market.