Technology with the Environment in Mind

Materials Technology for Environmentally Green Micro-electronic Packaging

INTRODUCTION

Intel's drive to "get the lead out of the package" began over five years ago when we produced a Pb-free tin-silver-copper (SAC) solder for 2LI applications that complied with European Union Restriction of Hazardous Substances (EU RoHS) requirements. Continuing on this path to deliver "Pb-free" packaging, Intel recently reached a critical milestone by eliminating Lead (Pb) from the FLI solders in its next-generation 45nm Silicon technology roadmap products. Intel is among the first semiconductor companies to deliver Pb-free FLI solutions in high-volume manufacturing. In order to meet the stringent integration challenges of transitioning to Pb-free-compliant packages, Intel has also successfully developed substrate, FLI flux, and underfill (UF) materials technologies that are compliant with higher Pb-free processing temperatures. Intel has been working with suppliers, customers, and several industry consortia to develop and provide EU RoHS-compliant products. Intel has completed certification of EU RoHS-compliant materials and processes and is manufacturing and shipping many EU RoHS-compliant products today. Additionally, in anticipation of the RoHS regulations, Intel pro-actively worked to develop pioneering Pb-free STIM materials to meet the challenging needs of heat dissipation from the silicon die.

Intel's drive to enable halogen-free (HF) substrate technology entailed a careful evaluation of HF material properties to identify robust materials sets in order to meet manufacturing, assembly, performance, and use condition-based reliability criteria. The selected HF substrate materials sets were fungible with existing manufacturing and assembly processes used previously with nHF (not halogen-free) cores. Several technical challenges were overcome in enabling the HF substrate technology. Mechanical drilling of HF cores, as well as substrate warpage, was evaluated to verify that their performance was on a par with nHF cores, from a manufacturing and assembly perspective. The electrical properties of the HF core material were also evaluated and it was determined that the impact on performance compared to that of nHF cores was negligible. From a reliability perspective, the key concern with HF substrates was delamination, which can occur due to moisture release at Pb-free reflow temperatures from the HF core material. To verify that adequate reflow delamination margins exist for HF substrates, relative to use condition requirements, a component reflow accelerated test was developed by Intel and used to assess Intel's HF product lineup. The drive to enable HF materials has continued with the development and successful introduction of HF-compliant packaging materials such as molding compounds, underfill materials, and Polymer TIMs.

In the first half of this paper, we discuss Intel's qualification of Pb-free packaging solutions in the first-level interconnect (FLI), second-level interconnect (2LI) and solder thermal interface materials (STIM) applications. In the second half, we address the enabling of halogen-free (HF) substrates and accompanying reliability challenges.

A schematic of a lidded ball grid array (BGA) Intel package is shown in Figure 1 which depicts the FLI, 2LI, TIM, and substrate materials technologies that are undergoing the environmentally green transition in Intel's micro-electronic packaging.

Figure 1: Schematic of Intel's lidded BGA package
click image for larger view
 

Back to Top