Characterizing materials at the component interface can improve reliability

Abstract

Reliability test methods are performed during the manufacturing design phase to validate process conditions, with a goal to build electronic assemblies that meet reliability and product life objectives. Contract manufacturers (CM) build to the original equipment manufacturers (OEM) cleanliness specification in an effort to meet quality, performance and reliability expectations. Manufacturing engineers select the best materials available and match those material sets to process settings that produce high product yields. Highly accelerated life testing is used to validate the process by introducing high stress levels in order to quickly uncover material weaknesses. A weakness of current reliability test methods is that they are performed at the qualification and validation stage. The methods are run on test boards designed to simulate the actual product being built. Both electronic and chemical test methods are typically performed by outside reliability labs. Once the process is signed off by the OEM, CMs do not have a simple test method that they can use to verify that the product is being built to designed test levels. Ionic Testers were commonly used as a process check, but with the emergence of highly dense interconnects and more complex flux designs, this process tool no longer provides an accurate assessment. A novel, real-time test method has been designed to run a performance qualification on boards built with specified soldering materials, reflow settings and cleaning methods. High impedance measurements are performed on break-off coupons designed with same component geometries used to build the assembly. This test method provides a gauge of potential contamination sources coming from the assembly process that can contribute to electrochemical migration. If the process is outside limit values, the CM can do a root cause analysis and correct the problem. The purpose of this research paper is to present ongoing research with the objective to develop the real-time SIR test methodology for ensuring that assemblies are built to the designed specifications.