Part III - The Driving Forces Behind Die Extraction for Reassembly – Increased Temperature Reliabili
Die Extraction for Bare Die Regeneration and Increased High Temperature Reliability-
High temperature semiconductor applications are pushing reliability needs beyond 200C. Previously, devices have utilized ceramic packaging and aluminum bond wire for these needs. However, a desire for reduced footprint and multi-chip module assembly make gold wire bonding desirable. For these applications, an electroless nickel layer may be deposited on the aluminum pad surface to act as a diffusion barrier.
There are many wafer plating companies that can bump full wafers for flip chip or wire bonding applications. These are cost effective when large quantities of die are required. However, prototype builds or Research and Development activity typically do not warrant the expense of full wafer purchases. Additionally, not all die are available for purchase in in wafer form. Some die may be unavailable due to obsolescence. In these cases, smaller quantities of die can be fulfilled with bare die regeneration: Die extracted from the original package, followed by re-plating with an ENEPIG process. These die have a fresh bonding surface accompanied by a nickel diffusion barrier and are ready for installation into a package or multichip module application (see Figure 1 below).
Figure 1: Representative Ni/Pd/Au plated pad with gold ball bond after 1000 hrs at 250C