Improved etching recipe for exposing Cu wire allowing reliable stitch pull

The AECQ-006 (Automotive Electronics Council Qualification Requirements for components using Cu wire) requires stitch pull tests on decapsulated Cu wire devices after TMCL and HAST/THB testing. The challenge is to perform decapsulation that exposes the complete interconnect without damaging the wires, leads or bondpads. A new method was developed in NXP to achieve this goal. An existing Cu wire decapsulation recipe was improved to protect the leads by adding Benzotriazole or AgNO3 to the nitric/sulphuric acid mixture.