Cu wire bonding in Ni/Pd/Au-Ag and roughened Ni/Pd/Au-Ag pre-plated leadframe packages

摘要

Copper wire bonding on an Ni/Pd/Au-Ag alloy-plated Cu leadframe surface and a roughened Ni/Pd/Au-Ag alloy-plated Cu leadframe surface is studied in terms of stitch pull after the wire-bonding process and after being subjected to package reliability stresses. The package reliability stresses include pre-conditioning at a moisture sensitivity level 3 (MSL3) test with three cycles of reflow at 260 °C (peak temperature), temperature cycling (TC) for 1000 cycles, autoclaving (AC) for 96 hours, and high temperature storage (HTS) at 175 °C for 1000 hours. The results show that the Cu wire can be wire bonded on Ni/Pd/Au-Ag-plated and roughened Ni/Pd/Au-Ag-plated surfaces. The stitch pull shows positive results after the wire-bonding process and after reliability stress testing. Cross-sectioning and scanning electron microscopy (SEM) were done after assembly and after reliability stress testing to check the interface of the Cu wire and leadframe surface. It was observed that no intermetallic compounds (IMCs) formed at the interface between the Cu wire and leadframe. Scanning acoustic microscopy (SAM) was also performed to check whether there was any delamination at the various interfaces at zero hours and after stress testing. The results reveal that the package with Ni/Pd/Au-Ag-plated leadframe shows delamination at the top of the die paddle after stress testing while the package with roughened Ni/Pd/Au-Ag-plated leadframe shows positive results after the stress testing.