Assembled board testing

Graves and Willems [48] provide an example of a network model to determine safety stocks in a supply chain at Eastman Kodak. The supply chain involves a high-end digital camera in which the camera, procured from an outside vendor, came with lens, shutter, and focus functions. The imager, circuit board assembly, and many other parts were assembled and tested. The final product was then moved to a distribution center and shipped against demands. The parts in the camera were classified into two groups, one with a lead time of under 60 days and the other set with a lead time of over 60 days. 

The work of the panels began in 1980, when the Department of the Army asked the Committee on Toxicology in the Board on Toxicology and Environmental Health Hazards of the National Research Council s Assembly of Life Sciences (now the Commission on Life Sciences) to review the Edgewood experimental studies and advise on the long-term or delayed health effects that the volunteer test subjects might have sustained. 

Figure 4(a) shows details of the test chamber. The teflon jacket-copper block assembly was mounted on a stainless steel plate. The sprayed liquid was drained back to the reservoir installed below the test section. Thermocouples to measure the liquid temperature were installed both upstream of the flow meters and downslream of Ihe orifiee plate. Another thermocouple was used to measure the ambient temperature. The HAGO nozzle and the orifiee plate (for microjets) were attached to the end of a pipe whieh eould be moved up and down. Thus the distance between the sprays or jets and the heated surfaee eould be varied. The liquid pressure was measured using a pressure transducer (0 - 2.07 MPa, 0.25% aeeuraey) just before the sprays or jets were formed. All the data were recorded using two lOTech 16-bit data aequisition boards. 

For sensor applications, printed circuit boards are manufactured and assembled in larger sized batches. If possible, testing and trimming are also done in the same way. Finally, the PCB is devided into individual sensor modules. This approach is key to minimizing cost. 

In one of the leading UK pharmaceutical companies, a printed circuit board assembly in a plant controller was replaced after a failure with an ostensibly identical unit. To everyone s complete surprise, this simple action, regarded as relatively routine, led to a major operational incident. The cause was found to be an EPROM chip on the replacement board. This chip not only carried an upgraded version of the software on the original but also possessed different operational parameters. Despite the fact that the replacement printed circuit assembly had been successfully tested (in accordance with quality procedures), it was the lack of effective configuration management that allowed the change in the software to elude detection, which led directly to the failure. 

The first specifications for adhesives were generated by the staff of NASA and the DoD who were prompted by the high reliability that was required of microcircuits used in aerospace programs. These specifications covered primarily die and substrate attachments for hermetically sealed integrated circuits, hybrid microcircuits, and multichip modules. Subsequently, with the increased use of surface-mount adhesives in the assembly of commercial printed-wiring boards and underfills for flip-chip devices, industry associations took the lead in generating the requirements and test methods. 

Thermal testing Voids or disbands in both metallic and nonmetallic materials, location of hot or cold spots in thermally active assemblies Laminated structures, honeycomb, and electronic circuit boards Produces a thermal image that is easily interpreted Difficult to control surface emissivity poor discrimination... 

NRC. 2000. Evaluation of Demonstration Test Results of Alternative Tech-nologies for Demilitarization of Assembled Chemical Weapons A Supplemental Review. Committee on Review and Evaluation of Alternative Technologies for Demilitarization of Assembled Chemical Weapons, Board on Army Science and Technology. Washington, D.C. National Academy Press. 

This economical test exposes die climatically unstable points of electronic components. Due to the nature of the test, the entire board is evaluated. This test accelerates the mechanisms of electrochemical migration. Consequently, faults that previously would appear after months or even years can be detected during the development process. To identify potential weak points, the assembly is operated in standby mode and immersed in deionized water. Testing while the assembly is in full operation is even more effective. The sensitivity of the circuit to moisture exposure is assessed on the basis of flie recorded test current, combined with a subsequent examination of the assembly. Through weak point analysis, a Yes/No decision can be determined concerning the expected service life, of the assembly. 

Bonded assemblies are made from straight-grained spruce with a density of (425 25) kg/m at (12 1)% moisture content, free from knots. 4 lamellae are prepared from one board and matched according to Fig. 6(a) in order to obtain 2 specimens, one glued with the PUR adhesive to be tested and the other with a PRF adhesive already approved according to EN 301 (Fig. 6(b)). A total of 5 pairs of... 

The specimen (a complete unit, its sub-assembly or component) and the test conditions (the material in the normal environment or underlaid with a pinewood board covered by tissue paper) are identical to the former standard. The igniting source is a 35 mm long burner tube with a bore of 0.5 0.1 mm and an outer diameter not exceeding 0.9mm(e.g. a hypodermic needle with the tapered end cut off). In the vertical position of the burner, the length of the flame is adjusted to 12 1 mm. The test flame is applied at 45 deg. to the specimen, in most unfavourable position of normal use (Fig. 3.119) preferably for 5, 10, 20, 30, 60, or 120 s. The exact site and duration of ignition may be given by the relevant specification of a particular product. Unless otherwise specified, the specimen is considered to have withstood the needle-flame test if one of the following four situations applies ... 

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