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May 2014 • SMT Magazine 69 The high level goals that served as the dri- ving requirements behind the project consisted of four major elements: 1. A zero footprint concept that allows in- stallation of the electrical test components into standard size automation equipment—without adding extra length to the assembly line. 2. A multisite concept that allows expan- sion of the electrical test throughput capacity of the ICT system without the need to add new test systems. 3. A selectable receiver concept that allows the test system to be configured with a variety of high integrity test fixture connection schemes. 4. A "clean connect" concept that simplifies maintenance and repair activities of the electri- cal components of the test system. The engineering team designing the new brand of ICT system incorporated a number of key changes that contributed toward achieving these design concepts. Shrinking Equipment Size One of the biggest obstacles to fitting an ICT system into the standard 19'' space typically re- served for automated test and inspection equip- ment is the infrastructure built-into the tester to support testing of complex PCB assemblies with more than 3000 nets. An electrical test sys- tem capable of testing large net count boards requires a large switching subsystem that takes up a lot of space. Historically, ICT system manufacturers have developed test systems with a one-size-fits-all approach, capable of testing the highest com- plexity PCB assemblies. This resulted in electri- cal test systems with large receiver interfaces, large instrument backplanes, numerous user power supplies and all of the related infrastruc- ture that is required to support high complexity test applications. During market discovery activities, it was determined that the majority of manufacturers building high-volume products on automated assembly lines do not generally require high pincount capacity test systems. It was learned that most high-volume automated manufactu- rers are building products that have less than 2000 nets and often less than 1000 nets. It was also learned that these applications seldom re- quired more than three user power supplies. Based on those discoveries it was decided to optimize the design of the new brand of auto- mated electrical tester around pincounts of 640, 1280 and 2560, and to reduce the maximum nu- mber of user power supplies from 14 to 5. These optimization decisions allowed the designers to reduce the size of the tester backplane by 66% and 83% compared to traditional test systems, and it significantly reduced the mechanical and electrical infrastructure associated with sup- porting large pincount test systems. By tuning the tester electrically and mechanically to the typical size of the products they are building, high-volume manufacturers building smaller pincount products are not burdened with the overhead of accomodating test features that they never intend to use. Increasing the Density of the Pin Fields In a typical in-line production environment, the dimension of width matters much more to the manufacturer and the automation equip- ment supplier than the dimensions of depth or height. It is the width of the assembly and test equipment more than anything else that de- termines the total length of the assembly line and the amount of floorspace that is required. Manufacturers often have extra space directly above or behind the automated assembly line that is not being utilized. With this knowledge in mind, the high-den- sity pin boards utilized in the new brand of au- tomated ICT system optimizes the number of pins available in the depth dimension so that less space is required in the width dimension. With this approach the designers were able to support approximately 400 test pins per linear inch of width and 2560 test pins in less than 6.5 linear inches, which effectively doubled the density of previous systems and ensured that fully configured test systems would fit easily within 19'' automation equipment enclosures. Implementing Flexible Fixture options Discussions with automated PCBA manu- facturers revealed no consensus with regard to THE CHaNGING ECoNomICS oF IN-CIRCUIT TEST continues feATuRe