The Pb-free solder interconnect reliability performance of a wide variety of common SMT component types was measured in an IPC-9701 TC1 thermal cycle (0-100°C / 40 min cycle). Seventeen different Pb-free SMT components were evaluated, including PBGAs, CBGAs, CCGAs, power modules, QFPs, PLCCs, CSPs, chip capacitors and resistors.

This paper was presented at APEX 2006

 

The Pb-free solder interconnect reliability performance of a wide variety of common SMT component types was measured in an IPC-9701 TC1 thermal cycle (0-100°C / 40 min cycle). Seventeen different Pb-free SMT components were evaluated, including PBGAs, CBGAs, CCGAs, power modules, QFPs, PLCCs, CSPs, chip capacitors and resistors.  All were attached to a six layer PCB using SAC387 solder paste according to the HDPug GPLF defined assembly process. This study specifically compares the reliability behavior of these various component types when subjected to expected Pb-free assembly process extremes such as minimum peak reflow temperature and extended reflow soak times.  Microstructural features of as-assembled SAC solder connections are first explored.  Failure data is reported for the various component types and assembly conditions. All SAC solder thermal cycling data was collected along with eutectic SnPb solder controls.

Introduction

High Density Package User Group (HDPug) is a collaborative consortium of industry members intent on identifying and resolving technical challenges associated with producing higher complexity electronic products. The HDPug General Purpose Lead Free (GPLF) initiative evaluates the performance of higher complexity PCBAs through realistic assembly manufacturing conditions.  It necessarily incorporates a substantial range of expected process variability, exploring the minimum solder reflow temperature requirement for reliable SnAgCu (SAC) board level interconnects.  It explores the relation between peak reflow temperature, reflow soak time and the resultant solder interconnect reliability.  It evaluates the  compatibility of a variety of component surface finishes, both Pb free and Pb bearing, that may be encountered in the industry transition to Pb-free card assembly.  It further is intended to generate a set of Pb-free assembly process recommendations supported by appropriate reliability data.

This paper comprises an interim status report of the HDPug GPLF project. Specifically, it provides some metallurgical highlights of the Pb-free solder interconnects on the as-assembled GPLF test boards along with a description of the electrical failures resulting from 6000 cycles of an IPC-9701 TC1 accelerated thermal cycle.

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