Increasing IO counts have led to ever increasing solder performance expectations. A predominant measure of solder joint integrity is gained through HSS testing. This article will statistically evaluate the solderability of final finishes after substrate and IMC ageing. Lead free solder balls will be used in this exercise to simulate lead free production. The finishes selected are: Immersion tin, Organic Surface Protection (OSP), Electroless Nickel/ Immersion Gold (ENIG), Electroless Nickel /Electroless Palladium and Immersion Gold (ENEPIG) and Electroless Palladium / semi Autocatalytic Gold (EPAG).

Where necessary, the adaptions of the final finishes will be included for testing. An example of this is ENEPIG with thin nickel. This is a measure to enable high frequency and or improve flexibility.

For the purpose of the paper, the evaluation will endeavor to relate HSS performance and physical and chemical characteristics of the related deposit layer. To ensure that a comparative analysis is possible, an “as received” (ASR) population will be used as a base line.

This fully data driven evaluation will aim to increase the understanding of key indicators that can ensure good quality soldering performance. In the field, there are assertions that the IMC is a good indicator of the solder joint integrity. However this is usually as far as this particular statement is taken. A key question that is still outstanding is what particular attribute of the IMC is important for solder joint reliability. The shape and size of the IMC is often cited as crucial to quality assurance. Such indicators may be valid but this study will couple this kind of observation with elemental quantification (EDX), high resolution microscopy and finally mechanical failure techniques.

A comprehensive test plan will be executed to more fully understand the role of IMC formation in terms of solder joint reliability, (SJR).

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