Challenges in Fine Feature Solder Paste Printing for SiP Applications

Abstract The rapid development in the Internet of Things (IoT) has seen a surge in demand for System-in-Package (SiP), which is capable of packing more functionality into a single package with a small form factor. This continues to push miniaturization to an even greater level, therefore creating assemblies with smaller components and greater density. 01005 passive components are being used in most of the current SiP technology and the industry is looking at utilizing 008004 passive components for the next generation SiP. The stencil aperture design for 008004 will likely be about half of 01005, and a finer powder size solder paste will be used. The stencil design, stencil thickness, and the types of stencils being used, are crucial in achieving good solder paste printing performance. Due to the need of squeezing more components into a SiP, the gap between neighboring pads can be as close as 50μm; hence, it is crucial to avoid solder bridging for such applications. This paper will discuss the challenges in achieving consistent solder paste printing performance for fine feature applications using Type 6 (5–15μm) powder size solder paste. Test results with different stencil designs, printing parameters, and different solder pastes will be discussed in detail.