In electronics assemblies components and substrates are mechanically and electrically interconnected via soldering processes, and since the solder joint is the weakest point in the assembly, it usually determines the lifetime of the assembly. Hence estimates of the lifetime of electronics assemblies are often made by monitoring the degradation (and eventual failure) of solder joints.
Solder joint failures are a common failure mode observed in electronic packages. The formation of a reliable solder joint depends on several factors such as the ability of the molten solder to rapidly and uniformly wet the surface finish and interact with it to form a consistent intermetallic layer at the interface. The wetting behavior, interface chemistry, and metallurgical microstructure of the solder joint are determined predominantly by the reflow temperature. In addition, overall solder joint reliability is determined by a combination of operating environment and system design.
In order to study the joint microstructure and any cracking that occurs, it is essential to examine carefully prepared microsections of suitable joints.
Our cross-section tests are destructive tests, in which we cut out a small “test coupon” portion of the assembly in question and check multiple attributes to determine the product’s overall quality. This microsection analysis can be conducted at any point in the manufacturing process, including the prototyping stages. It can also be done after assembly, to test components for thermal stress and proper solder connections. In failure analysis cross-section testing, we check a number of factors to determine what caused the product to fail. Cross-section testing has a wide array of applications throughout the industry, and is the second most common test method for determining the overall quality of products during the manufacturing process.
Maintaining PTH integrity is one of the most important factors to assure success with press-fit interconnects. Cross-section analysis is used to prove the basic integrity of press-fit pins for use within specified production parameters.
After environmental stress testing, microsection samples with press-fit pins fully inserted into the PCB are prepared and then visually analyzed and measured at key transverse and longitudinal locations in order to determine if any deformation has occurred.