Quad-Flat, Non-leaded (QFN) packages are considered CSPs because they are often no more than 20% larger than that actual chip built inside.  They combine the simple construction and economy of leadframe-based packaging with the flexibility and density of matrix-array substrates.  Because finished packages of different sizes are cut from a common matrix, new outlines and pincounts can be tooled far more easily than with conventional leadframe packages like QFPs.  Short interconnections and exposed metal give QFNs superior electrical and thermal performance, often good for applications requiring up to 12 GHz, and their solid, compact design gives them robust reliability.

QFNs are typically used for analog, RF and mixed signal chips, and are supplanting the need for more conventional packaging of memory and smaller logic ICs.  Due to their miniature size and RF-class performance, they are most often found in portable wireless applications like cell phones and wireless LAN products, as well as all types of handheld electronics such as digital cameras and PDAs.