Pb-free Solder Challenges in Electronic Packaging and Assemblies


Fay Hua


Intel Corporation, Material Technology Operation

3065 Bowers Ave, Santa Clara, CA 95054




Solders have been used in many areas of electronic packaging and assemblies.  They have been used as electrical and mechanical interconnects, such as flip chip bumping and attachment, ball grid array (BGAs), surface mount (SMT), and soldering surface finishes, such as leadframe coating, print circuit board metal surface finish for several decades.  As future electronics become small, fast and cheap, there are several critical soldering technology gaps.


1) Scaling effect.  While flip chip joints became smaller and smaller, the scale of the solder joints is closing the feature of solder microstructure.  The mechanical behavior of solder joints would be different from large solder joints.  The goal is to understand the scaling effect and ultimately be able to predict the solder joint use life.


2) Soft, long fatigue life solde Emerging new technology: New technologies, such as hot chip, needs solder as thermal interface material; Optical assembly, needs reactive/fluxless soldering, etc.  New solders need to be developed to meet different application requirements


3) Low temperature soldering.  The eutectic Sn-Ag-Cu solder chosen by industry has much higher melting temperature as conventional eutectic Pb-Sn solders.  Higher energy consumption during assembly, higher package reliability risk and new product requirements drive in developing low temperature soldering technology.


4) Fundamental understanding of Pb-free solders.  Industry has over 50 years of experience with SnPb solders in electronics packages. Empirical roles for SnPb solders are not automatic applicable to Pb-free solders. Fundamental understanding of Pb-free solders is key task for solder materials researchers for next decade.