Why Is The Solder Ball Getting Smaller in Advanced Packaging?

What does the solder ball do?

Three main functions: electrical connection, mechanical support, heat transfer.

The picture above shows the development process of different tin ball technologies, and the size of the tin ball is gradually reduced. 1, SnPb C4 Bump (SnPb C4 tin ball) Traditional tin-lead (SnPb) alloy tin ball, diameter 75-200 µm. Tin-lead alloy has good reliability, but due to the harmfulness of lead, it is gradually replaced by lead-free materials. 2, Pb-Free C4 Bump (lead-free C4 tin ball) Lead-free tin ball, usually using tin silver (SnAg) alloy, diameter 75-150 µm, in line with environmental requirements, instead of lead alloy. The mechanical and electrical properties of lead-free tin balls are similar to those of lead alloys. 3, Cu Pillar + Pb-free Cap (Cu Pillar + PB-free cap) The lead-free tin cap (SnAg) is added to the bottom of the copper pillar (Cu Pillar), with a diameter of 50-100 µm, the copper pillar reduces the volume of the tin ball and improves the heat dissipation performance. Suitable for higher density integrated circuit packages. 4, Cuμ-Pillar + Pb-free Cap (micro-copper column + lead-free cap) A micro-copper column (Cuμ-Pillar) with lead-free tin cap (SnAg), diameter 10-30 µm. The interconnect size is further reduced to meet the needs of extremely high density packaging, such as 3D IC packaging technology.

Why are tin balls getting smaller and smaller?

With more and more functions of integrated circuits, the chip size is relatively reduced, and smaller tin balls are needed to achieve high density interconnection. The miniaturized tin ball with copper column has better heat dissipation performance and ADAPTS to higher power chip requirements.

Common tin ball making method?

Screen printing, laser ball planting, electroplating, etc.