Improvements in adhesion using new Cu treatment method for substrates [packaging]

Abstract

This report discusses the differences between the current jet scrub (mechanical) and newly used chemical etch processes in the substrate manufacturing process to etch copper. This newly proposed process is expected to increase package moisture performance by creating a rougher surface finish, resulting in interlocking of the solder mask to the copper. The differences between the two processes are covered in detail. The report discusses moisture results obtained, comparing the two processes with existing package materials in a BGA. The mold compound, nonconductive die attach and jet scrub substrate have achieved moisture sensitivity level 1 at 220/spl deg/C reflow in some cases of optimized substrate design. The process performance is benchmarked using four substrate suppliers used in the industry. Package moisture performance improvements are critical to passing higher reflow temperature requirements such as 240/spl deg/C and 260/spl deg/C for Pb-free solutions for environmentally sensitive products in the wireless and palm pilot communications market. Also included is a discussion of how the chemical etch performs based on other assembly quality measures such as wire ball shear, wire pull, solder ball adhesion and solder joint reliability. This new process is not expected to affect cost or cycle time and is seen as an improvement in overall product quality and reliability. However, due to varying experience with BGA moisture performance, especially in cases of large die to package ratios, it is hopeful that the process will provide more consistent results on the package.