The critical advantage of pre-coating resin in a lead frame is to provide a solderability indicator for the QFN package during AOI inspection after board assembly. This indicator is realized through a “wettable flank” built into the lead frame to avoid a complicated back-end assembly process for the same purpose.
When designed with multiple rows, this lead frame offers an ideal alternative to the laminate substrate in a wire-bonding BGA assembly where electrical/ thermal characteristics, reliability, and package form factors can be significantly improved.
