Medical Electronics Symposium Conference Proceedings


Authors: Lucian Kasprzak, Milind M. Sawant and Mario Santan
Company: Dade Behring Inc
Date Published: 9/12/2006   Conference: Medical Electronics Symposium

Abstract: Dade Behring uses SMT PCBs in Diagnostic Chemistry Instruments. The SMT PCBs are used to control position, aspiration, aliquot and analysis in a distributed processing environment. A CAN communication bus structure facilitates the command and control by computer, as well as ionic and photometric analysis techniques. A typical instrument has in excess of 50 SMT PCBs, with about 15 unique form factors and function sets. The function sets are tied to the specific sample path through the instrument. A typical path involves introduction of the sample, aspiration, aliquot, reagent delivery, analysis, etc. An ancillary part of the path is the physical positioning and plumbing, which requires motor drives, sensors, solenoids, valves and pumps. This paper will focus on our approach to assessing the reliability of the SMT PCBs. During stress test, we exercise all the functions the board can perform in a temporal sequence identical to that required by the function in the instrument. Our procedure is to execute these functions during the stress test, followed by either an accelerated or life test. For each temporal cycle of functions performed, a log of measured evidential data is stored with date and time stamp as a data file of either successful performance or failure. All errors are also logged in a separate file. The duration of the stress test is approximately one week, covering extremes of temperature, humidity, voltage and also power cycling. The duty cycle is maintained as close as possible to 100% during 24/7 operation. The subsequent accelerated or life test is extended to represent product life. Because the SMT PCBs provide many functions and generate large amounts of analytical data, we store the data files in a database for posttest analysis. Failures are analyzed for root cause. Parametric trend analysis is used to identify potential parameters for Condition Based Maintenance. Keywords: SMT, PCB, Reliability, Diagnostic chemistry

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