Next-Generation Solder Plating Chemistry for Optimizing Post Reflow Coplanarity in Mixed Feature Die Designs

Industry trends in advanced packaging are clear: increase interconnect counts by driving both higher interconnect density and larger die size. While the direction is clear, the approaches to achieving these goals are diverse, often involving complex designs with mixed feature sizes and densities. At the same time, these packages impose increasingly stringent requirements for within-die uniformity to mitigate stress accumulation across larger package sizes and ensure long-term reliability.

These evolving demands require more robust and uniform interconnects, placing increased pressure on electroplating chemistries to deliver consistent performance across challenging designs. In particular, mixed feature sizes across a die present a significant challenge for electrodeposited solder. When post-reflow height uniformity is required, variations in feature diameter result in differences in final bump height, as larger features expand more upon reflow. Achieving uniform post-reflow height therefore requires an intentional height offset from the electrodeposition process. To address these requirements, Qnity Electronics has developed a new lead-free (SnAg) solder plating chemistry engineered specifically for these advanced packaging challenges. This chemistry enables controlled height offsets through tuning of bath composition and plating parameters tailored to the die design. Further, the chemistry delivers tight coplanarity, compatibility across a wide range of feature sizes (C4 bumps to microbumps), and uniform deposition across regions with varying pitch. This versatile chemistry demonstrates strong performance across various die designs, positioning it as a compelling solution for next-generation advanced packaging interconnects.

Key Technologies Covered 

• Lead-free solder
• Electroplating chemistry
• Mixed CD die design
• 2.5D integration
• Advanced Packaging
• Tin-Silver Alloy