Lead-Free reliability

Introduction

One of the key concerns when converting to Lead-Free assembly is long-term reliability of solder joints. There are several important factors that may influence the reliability of Lead-Free assemblies. Material, component and process parameter combinations can influence the longer-term reliability of Lead-Free joints. These variables include, amongst other things, the type of printed circuit board laminate, the solderable finish used, the Lead-Free alloy, the component type and choice of its solderable finish, as well as the assembly equipment, soldering process and, importantly, the subsequent operational service conditions. Consequently, making overall predictions about Lead-Free reliability can be difficult and there is conflicting evidence from various testing programmes; simply changing one variable may result in completely different reliability results. Lead-Free reliability is effectively application-specific and can only be established by generating failure information from appropriate accelerated testing procedures followed by careful extrapolation to the in-service conditions required for a particular application.

The good news is that if done carefully and correctly then Lead-Free reliability can surpass that of tin-lead joints. However, it is important to remember that the use of inappropriate conditions and materials combinations can severely compromise long term solder joint reliability. This section gives a short overview of some of the important factors that can influence long-term Lead-Free assembly reliability.

Factors impacting long term reliability

Testing

General observations

Reliability summary