Second Bond Stitch Width Model as a Trend Solution for Lead Width Reduction

A well known trend in the semiconductor industry is miniaturization while continuously increasing the number of Input Output (IO) connections. This trend introduces new Wire bonding (WB) challenges in the second bond arena, known as the second bond stitch width. As the stitch width scale gets closer to the lead width, the need to accurately predict the second bond width becomes crucial. In order to answer this new need a JMP (ver.7.0) model for second bond stitch width in correlation to the capillary dimensions and Wire Diameter (WD) is introduced. Different designs with changing geometries were optimized, bonded, and measured for their stitch width responses. Geometries such as: Hole (H), Chamfer Diameter (CD), Tip size (Tip), Face Angle (FA), Outer Radius (OR) and WD are part of the tested matrix. A verification test was conducted and custom capillary designs were produced based on a numerical formulation from the model in order to receive a specific stitch width. These capillary designs were bonded and measured in order to verify the credibility of the stitch width model. An important observation out of few interesting results showed, that the main contributors controlling the second bond stitch width are the WD and Tip. Additionally a stitch width formulation as a function of the main capillary geometries and WD is introduced.