Surface mount technology. Capabilities and requirements

Surface mount technology has accelerated over the past 2 years. It includes high I/O (input/output) density packages which are now being used routinely in non-aerospace applications. Although some avionics packages are incorporating the newer technology, there are a number of issues which need to be considered prior to their wide spread use for space applications. The issues which need to be addressed include the long term integrity of the package attachment, the types of interconnect boards which need to be qualified or developed, and the assembly and inspection processes. This paper reviews the status of space qualification of the package to board interconnect for this technology, distinguishing between different types of mission scenarios, e.g., low earth orbit (LEO) versus geosynchronous earth orbit (GEO). Analytical models, developed and reported in the literature, which relate thermal cycle robustness to component and board configurations, are applied to high density surface mount packages. Limited experimental data on thermal cycling of plastic ball grid array packages is presented and results are compared to the predictions based on analytical models. Analysis results indicate that within a reasonable range of package sizes, the new technology can be made robust and reliable for LEO and GEO missions. The choice of the proper combination of package types with interconnect board materials is critical to reliability.