PROCESS CONTROL STRATEGIES IN MINIATURE, HIGHLY COMPLEX PCB ASSEMBLY
Author: Sean Griffin Company: Manufacturers’ Services Date Published: 8/23/1998
Surface Mount International
Abstract: The seemingly never-ending demand for mobile electronic devices is driving PCB designs towards increased density, packaging complexity and miniaturization. This is challenging electronic manufacturing services (EMS) providers’ traditional reliance on in-circuit test (ICT). With highly dense and complex board assemblies, ICT is not always an effective and cost-efficient option. In high-volume production of these boards, ICT can be a significant detriment to efficiency, as test time does not keep up with line cycle time. Alternatives, such as visual inspection, which is only about 70% efficient, seldom deliver the accuracy required to support tough yield requirements. In some cases, designs may involve components such as BGAs or shielding for radio frequency components that actually prevent the use of visual inspection. This paper will examine the use of x-ray technology as a process control vehicle, based on data from a high-volume continuous flow manufacturing SMT line, where x-ray inspection was implemented to screen for manufacturing defects on a complex, double-sided board with ultra fine pitch devices. It will explore the alternatives, including the evaluation of performance and accuracy and the process followed to establish the criteria that led to the ultimate selection of x-ray. The piece will discuss the pre-implementation phase as well as the implementation process. The problems overcome and the results achieved will be analyzed. The paper will also outline the next phase of the evaluation to determine the viability of x-ray as a robust volume process alternative.