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Process window of thermosonic palladium wire bonding on electroplated gold layers for high temperature applications

Presentation held at MiNaPAD Forum 2012, 2nd Micro/Nano-Electronics Packaging & Assembly, Design and Manufacturing Forum; April 25-26, Grenoble, France
: Heiermann, Wolfgang; Heß, Jennifer; Geruschke, Thomas; Bauer, Jochen; Ruß, Marco; Kappert, Holger; Vogt, Holger

Micro/Nano-Electronics Packaging & Assembly, Design and Manufacturing Forum (MiNaPAD) <2, 2012, Grenoble>
Fraunhofer IMS ()
wire bonds; Pd wire; high temperature microelectronics; harsh environment; process window

For the development of high temperature stable wire bond interconnections capable for operation temperatures over 250 °C the processes performances of thermosonic palladium (Pd) and gold (Au) wire bonding to Au pads are determined and compared to each other. The bond pad metallisation is processed by electroplating a copper (Cu) / nickel (Ni) / gold (Au) stack on silicon (Si) Wafer. The 1.5 µm thick Ni barrier layer prevents degrading reactions between the Cu and the Au layers. The process windows of the Pd and the Au wire bonding processes are determined by a detailed DOE (Design of experiment). The present work shows that the shear strength of Pd bonds on electroplated Au pads clearly exceeds the lower shear strength limit of 67 MPa, as defined by JEDEC Standard JESD22-B116A, for a wide range of ultrasonic power and bonding force settings. The process window of Pd wire bonding is larger and overlaps the Au wire process window completely. In comparison to Au the Pd bond shear strength is up to 80% higher.