during functional testing. This is especially the case with small or partial cracking that can escape testing and cause latent field failures. Even if a component failure is identified, diagnosing the failure mode as pad cratering can be difficult. Conventional nondestructive testing and failure analysis techniques such as visual inspection and X-Ray microscopy may not detect the issue. Electrical characterization is an example of a nondestructive technique that can be useful, however this may not detect an anomaly if there is only partial cracking. Typically, pad cratering is detected or confirmed via destructive testing and failure analysis such as dye and pry, acoustic emissions, cross sectioning, and Scanning Electron Microscopy. Mitigation There are several mitigation techniques that can used to reduce the risk of pad cratering. The appropriate method(s) is often driven by design and resource constraints. Limiting Board Flexure: If cratering is due to mechanical overstress then limiting board flexure is typically the best mitigation technique. Simulation: Modeling and simulation can help proactively avoid pad cratering failures. Relevant examples include ICT failures or products with potential for large shock events (i.e. portable electronics). Finite Element Analysis can be done using a physics of failure approach to determine risk of overstress and pad cratering. This proactive approach can rapidly evaluate multiple designs early on, potentially avoiding expensive design changes or warranty costs later on. Underfill, Edge Bonding, and Corner Staking: Epoxies and underfill materials can be added to provide mechanical support and reduce board and solder strain during flexing. This is more common in cases where the component selection and PCBA design are fixed. There are differences between each technique which makes proper understanding of the environment and application important. Solder Alloy: Solder alloy selection can impact susceptibility to pad cratering. Typically, pad cratering is considered a high strain rate event with minimal creep, however there is still potential for plasticity in the solder. More compliant solders or those with lower yield points will reduce pad cratering potential by providing additional load sharing. Board Thickness and Laminate Material: Board thickness and laminate material properties such as Young’s modulus and Coefficient of Thermal Expansion (CTE) will impact susceptibility to pad cratering. Board Redesign: If pad cratering persists then a redesign may be required. This could include changing component location or adjusting between solder mask defined (SMD) and non-solder mask defined (NSMD) pads. Pad Cratering Images External links Additional information on pad