Alan J. Albee
North Reading, Massachusetts
Many manufacturers employ one or more In-Circuit Test (ICT) systems in their PCB manufacturing facilities to help them detect manufacturing process and component defects. These "bed-of-nails" electrical test systems are highly valued for providing the qualities of simple program generation, high fault coverage, fast test throughput, low false fail rates, and exceptional diagnostic accuracy as compared to other available test and inspection techniques.
Advancements in PCB technologies, along with changing test philosophies and manufacturing business models in recent years have created new and diverse requirements for manufacturers of in-circuit test systems. Particular challenges that ICT manufacturers have had to address include the erosion of test point access in certain product sectors; the progression of ultra-low voltage components; the variable test requirements of different product applications; the varying test philosophies of different market segments and different manufacturing regions; and the demanding throughput requirements of high volume production facilities.
This paper highlights how in-circuit test systems have evolved in recent years to include innovations and advancements to address these challenges and trends. Topics that will be covered include boundary scan and functional test integration strategies; advancements in vectorless test techniques; incorporation of limited access electrical test techniques; test strategy analysis tools; high accuracy pin drivers and sensors; concurrent test throughput improvement options; scalable test performance capability architecture; and program development accelerators.
The paper describes how these new ICT advancements contribute to lowering overall manufacturing test costs by improving the fault coverage, reliability, and throughput of in-circuit production tests.
ICT systems have evolved to address the technology and business challenges of modern PCB manufacturing and their capabilities have advanced far beyond when they were first introduced. Reduced access test techniques, integration of boundary scan and embedded testability tools, advanced pin electronics capable of testing low voltage technologies, concurrent test capabilities, functional test capabilities, and scalable test system configurations have all combined to extend the life of ICT systems and make them one of the tools that is still most valued by high volume PCBA manufacturers.
Taking into consideration how the in-circuit tester has evolved since its introduction and all the electrical test capabilities that are now at its disposal that do not require actual physical test access, it may be time for the industry to stop categorizing these test systems as "In-Circuit Testers" because that name no longer reflects all the things that the tester has evolved to do.
It may be more appropriate to now start categorizing these versatile test systems as "Electrical Test Controllers" because the most capable ones can support in-circuit, boundary scan, PLD programming, cluster and functional testing techniques all in a single consolidated test platform.
Initially Published in the IPC Proceedings