Decapsulation of silver wire bonded packages with known techniques often results in damaged silver wires. The chemical properties of silver and silver compounds make silver bond wire inherently susceptible to etching damage by acid, conventional plasma, and oxygen-based Microwave Induced Plasma (MIP). In this paper we solve this problem by developing a specific decapsulation chemistry, based on a hydrogen-containing MIP, for artifact-free decapsulation of silver wire bonded packages.

Decap methods which have been used for copper wire packages are not effective for silver wire packages, and the authors recognized the need for the development of a novel method. This paper discusses the development of various processes to decap silver wire packages with acid. The first decap method developed for a silver wire package was to add hydrochloric acid to fuming nitric acid. This method proved insufficient to prevent silver wire from dissolving when solution temperature is 60 degree. The authors then developed the Saturation Etch method for decapsulating silver wire packages using a chemical solution. When dissolution amount of silver wire put in normal fuming HNO3 is defined as 100%, the authors were able to achieve its reduction to less than 3% by using saturated acid. This method is also effective for copper wire packages, and damages to wires can be minimized by dissolving copper into acid.

LASER techniques are widely used for pre-opening in combination with a final manual or automated wet chemistry decapsulation. Even if most of the ICs may be opened today, and if opening the recently introduced Ag wires packages have been solved with novel chemical recipes, the need for a greener and safer solution is still there. Plasma techniques combined with LASER can be a promising solution to these challenges. In this paper, after a presentation of the state of the art of the different techniques available in laboratories nowadays, the latest solution combining LASER and acid or plasma etching is presented. The paper compares the results obtained with these solutions on Cu an Ag wires devices with pros and cons for each solution. The results presented show the benefits, the constraints and the limitations of each technique regarding the different types of wires used in industry.

Over the past several years there has been a large industry wide effort to change over from gold bonding wires to copper in order to minimize production costs. In certain cases this is not possible due to the relatively high hardness values of Cu [1], which leads to reliability issues in the manufacturing process. Silver (Ag) wire has been proposed and successfully implemented in many instances where Cu wire was not practicable. Unfortunately, currently integrated decapsulation methods severely damaged or destroyed the silver wires and bonds, making it impossible to perform production controls and failure analysis. In this article we present a reliable and repeatable automated method to expose these die and wire bonds. By adding a dilute iodine solution to the nitric acid in an acid decapsulator, these packages can be fully opened without degrading the silver wires, allowing both mechanical and electrical testing on these devices.