Study of 0.6mil silver alloy wire in challenging bonding processes
With competitive price and superior electrical/thermal conductivity and mechanical properties, more and more IC package industries have adopted copper (Cu) and palladium coated copper (PdCu) wires as the alternative to gold (Au) wire in the past decade. However, the high hardness and the excessive ultrasonic energy and bonding motions required during bonding of Cu wire limit its usage in areas such as memory packages and sensitive devices that are prone to damages on the pads and under-layer dielectrics. Silver (Ag) and Ag-alloy wires emerge as other alternatives since they have similar properties like wire hardness, elongation and breaking load at room temperature as Au wire while having a more competitive price. Process capability of ultra-fine (0.6mil) Ag-alloy wire, including free air balls (FAB) and bonding capability on aluminum (Al) die pads were first investigated. Factors affecting the FAB performance were studied and optimum settings were recommended. Comparison of bonding responses between Au, PdCu and Ag-alloy wires on challenging scenarios, such as overhang dies and die-to-die bonding, were also included in the study. Benchmarked Au process, Ag-alloy wire possesses great portability and wide first bond process window. Ag-alloy wire also demonstrates good bonding capability and loop shape control on challenging applications, such as overhang die and long die-to-die applications. However, further optimization of Ag-alloy process is still necessary to overcome its constrains, such as higher hardness and higher energy required during bonding of Ag-alloy wire.
Study of Ag-alloy wire in thermosonic wire bonding
Lower cost materials, such as copper (Cu) and palladium coated copper (PdCu) are the commonly chosen alternatives of gold (Au) wire in the package industry. However, the high hardness of Cu and PdCu wires brings concerns over the bonding quality and the long-term reliability of the packages. Silver (Ag) has drawn more attention in the package industry since it has similar properties like hardness, elongation and breaking load as Au, while having a comparable price to PdCu. Bondability of Ag-alloy wire, including performance of free air balls (FAB) and bonding capability on aluminum (Al) die pads, was first investigated. Inspection of intermetallic compound (IMC) and unmolded baking of the bonded packages with the Ag-alloy wire were also carried out for further understanding the reliability performance of the wire. Investigations of bonding capability comparison between pure Ag, Ag-alloy, and PdCu wires in processes with stand-off-stitch-bond (SSB) and peel sensitive dies were included in the study as well. Generally, Ag-alloy wire delivers good and stable bonding capability using N2 as the cover gas. For applications with SSB and peel/lift sensitive bond pads which are normally difficult using PdCu wire, Ag-alloy wire also possesses good performance.
Immersive haptic interaction with media
New 3D video representations enable new modalities of interaction, such as haptic interaction, with 2D and 3D video for truly immersive media applications. Haptic interaction with video includes haptic structure and haptic motion for new immersive experiences. It is possible to compute haptic structure signals from 3D scene geometry or depth information. This paper introduces the concept of haptic motion, as well as new methods to compute haptic structure and motion signals for 2D video-plus-depth representation. The resulting haptic signals can be rendered using a haptic cursor attached to a 2D or 3D video display.