PROCESS AND MATERIALS INTERACTION INVESTIGATION: TEST METHODS FOR ELECTROCHEMICAL CONSISTENCY IN PCB ASSEMBLY PROCESSES - REVISITED

摘要

There are several industry-accepted methods to determine the electrochemical reliability of electronic assemblies. These methods are typically designed to either simulate humid environments in accelerated lifetime testing, or assess the species of ionic residues present on surfaces. Some can be used to test prototypes or test boards, while some are more applicable for quality and consistency testing in a production environment. The increasing complexity of high-density assemblies, along with low standoff components, imposes greater associated challenges related to assessing electrochemical reliability. This has led to the development and adoption of new methods for testing ionic residues that can lead to electrochemical migration. This paper will review traditional and emerging methods to characterize flux residues and cleanliness of finished assemblies, including surface insulation resistance, electrochemical migration, ROSE extraction, and other emerging test methods. Data will be shared to reveal how different methods can detect process variations in different ways, and compare the results. With new revisions to IPC J-standard-001 and proposed changes to Section 8, the philosophy for ensuring assemblies are clean after a cleaning process has evolved. The way we look at the consistency of no-clean process residues for process control may also be evolving.