Reliability of PCB assemblies in products with high reliability requirements during a long expected life

Important results from the project

Evaluate if new high-reliability solders increase the life of solder joints to various components and how reliability is affected by PCB build-up and surface finish on solder pads. Evaluate if new coatings provide better environmental protection than older coatings without impairing the life of solder joints. Evaluate how much underfill can improve life of solder joints and if it is sufficient to apply underfill under corners of components. Develop recommendations for accelerated testing for various field environments regarding solder joint life and environmental protection.

Expected long term effects

The new solders did not generally provide an improvement in the life of solder joints. In some cases they gave an improved life but in other cases a reduced life. Two new coatings provided good protection with minimal negative impact on solder joints. Another coating provided good protection but with a greater negative impact on solder joints. For testing the life of solder joints, the temperature should not exceed 100°C. When testing environmental protection, test methods with exposure to salt fog or condensation of water provide decisive evaluations of environmental protection.

Approach and implementation

Sixteen companies participated in the project, which included EMS companies, OEM companies with own assembly manufacturing and OEM companies without own assembly manufacturing to cover a large part of the production chain. The companies represented automotive, space and military industries. Coordinator for the project was RISE. The evaluations were done partly with specially designed test boards and partly with functional assemblies from participating companies. In this way, several different combinations of test cycle, component types and coatings have been tested.