Cu2 Process Development For Cost Effective SOT Package

Commodity discrete package SOT faces tremendous cost reduction pressure among integrated chip & packaging manufacturers. Low cost per piece is desired to create better gross margin. Cost analysis found that direct materials (leadframe, bonding wire, compound etc) contributed >50% package cost per piece. Therefore, one of the rock bottom ideas will be exploring on bare copper leadframe with copper wire bonding. Current SOT package material sets are NiFe42, silver plated leadframe bonded with gold wire. This could easily reduce leadframe & bonding wire cost by 50%. This paper will discuss details feasibility study & development of Cu2 (bare Cu leadframe + Cu wire) backend process on SOT. Material sets selection, technical challenges understanding, equipment setup, feasibility study & design of experiment, failure analysis etc are performed to assess process manufacturability. Meanwhile, thermo-mechanical & moisture related reliability assessment (HTS/TC/PCT etc) also will be performed prior to official qualification & customer build.