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Critical parameters of the MIL‐STD‐202 Method 208 and MIL‐STD‐883 Method 2003 component solderability tests were determined from laboratory experiments. Among the variables examined were steam ager atmosphere, steam ager water quality, component drying, flux quantity, static versus wave pots and visual inspection variability. The test results indicate that one of the most important variables is steam ager atmosphere. This was evaluated by vapour temperature vs metal coupon weight gain. Other critical parameters are the drying process and inspection method. Experimental data for some parameters suggest necessary changes to the relevant Military‐Standard test methods. These changes are proposed based on the experimental work presented, and would improve correlation of solderability test results between suppliers and users.

Portable computers have been around just about as long as personal computers, and have always involved serious compromises. The compromises continue, but the computers have improved enormously in true portability, power, and price. You always pay a premium for portability, and more of a premium for the ability to actually work on the road. While the premium has come down, it's still there—but now, you can get almost as much power as you need, if you pay the price. In his second look at the last eight years in DOS computing, Crawford shows how conservative choices in portable computing have evolved, and discusses why conservatism makes more sense when buying a portable.

An outline is given of the purpose and activities of the ISHM‐US Education Program. Guidelines for establishing and operating Student Chapters are provided, together with the benefits of membership, and several of the facilities made available to student members are described.

Develops an original 12‐step management of technology protocol and applies it to 51 applications which range from Du Pont’s failure in Nylon to the Single Online Trade Exchange for Auto Parts procurement by GM, Ford, Daimler‐Chrysler and Renault‐Nissan. Provides many case studies with regards to the adoption of technology and describes seven chief technology officer characteristics. Discusses common errors when companies invest in technology and considers the probabilities of success. Provides 175 questions and answers to reinforce the concepts introduced. States that this substantial journal is aimed primarily at the present and potential chief technology officer to assist their survival and success in national and international markets.

The tenting of via holes has been a controversial issue in the military arena for several years. This issue has gained importance with MIL‐STD‐2000's requirement that all circuitry and vias under components be coated to preclude entrapment of flux. This paper addresses this issue by evaluating the MIL‐Spec thermal shock reliability of solder mask as a hole fill material and as a via tent cover. The relationship of via hole to pad size on tent reliability and solder mask thickness is also investigated. This paper concludes that solder mask as a hole fill material will not pass military thermal shock requirements and that standard dry film solder mask is very sensitive to via hole and pad dimensions. The thinner and more flexible high conformance solder mask is the only material capable of passing MIL‐Spec thermal shock requirements for all via hole to pad relationships.

Wiring requirements and thermomechanical factors related to the design and fabrication of Polymer‐on‐metal constraining core PWBs are discussed. The necessity of small plated‐through‐holes for high‐density surface mount design is shown. Typical MLB constructions are shown with techniques for increasing wiring density. A design methodology for the POM construction is defined. The thermomechanical properties of copper‐Invar‐copper and the interactions of the MLB are described. The reliability of small PTHs is measured over a wide range of module constructions. Sixteen mil. diameter PTHs are reliable if the MLB thickness is kept below 0·040 inch. Through‐substrate PTHs make reliable side‐to‐side interconnections.

For many years, the concern over the use of plastic encapsulated microcircuits (PEMs) has been their capability to survive in harsh environments over a long term with continuous or intermittent operation. The issues centred around operational life limitation, due to failure mechanisms associated with internal corrosion, wires and wire bonds, and surface effects, It has now been conclusively demonstrated that best commercial practices will ensure that PEMs made using best commercial materials, processes, and quality techniques will permit devices to perform reliably in the most severe environments. Missile systems are low volume production items, which use relatively few microcircuits. They are required to operate for very short times after being unpowered (dormant) for very long times (10 to 20 years) and exposed to humidity, temperature cycle, and mechanical shock. This paper will address reliability concerns and provide data from studies which were performed to determine if PEMs could survive such long‐term unbiased applications. These studies include analysis of PEMs (some date coded 1968) from inventory or various storage locations and from applications where the electronic modules containing PEMs were stored for 10‐12 years in various environments. Regardless of the storage conditions, the significant factor is that these early vintage commercial grade PEMs, without screening or incoming inspection, survived assembly and extended storage.

Wireless sensor networks (WSN), as a solution for buried water pipe monitoring, face a new set of challenges compared to traditional application for above-ground infrastructure monitoring. One of the main challenges for underground WSN deployment is the limited range (less than 3 m) at which reliable wireless underground communication can be achieved using radio signal propagation through the soil. To overcome this challenge, the purpose of this paper is to investigate a new approach for wireless underground communication using acoustic signal propagation along a buried water pipe.

An acoustic communication system was developed based on the requirements of low cost (tens of pounds at most), low power supply capacity (in the order of 1 W-h) and miniature (centimetre scale) size for a wireless communication node. The developed system was further tested along a buried steel pipe in poorly graded SAND and a buried medium density polyethylene (MDPE) pipe in well graded SAND.

With predicted acoustic attenuation of 1.3 dB/m and 2.1 dB/m along the buried steel and MDPE pipes, respectively, reliable acoustic communication is possible up to 17 m for the buried steel pipe and 11 m for the buried MDPE pipe.

Although an important first step, more research is needed to validate the acoustic communication system along a wider water distribution pipe network.

This paper shows the possibility of achieving reliable wireless underground communication along a buried water pipe (especially non-metallic material ones) using low-frequency acoustic propagation along the pipe wall.

Public concern over resource depletion, congestion, waste disposal, and various types of pollution has focused increased attention on environmental issues. These environmental issues are expected to broaden the scope of logistics and influence the way in which logistics managers do their jobs. To date, there has been relatively limited empirical research looking at the relationship between environmentalism and logistics management. Reports the findings of a survey of US manufacturers and merchandisers dealing with the role and relevance of logistics to corporate environmental efforts.

In some three-dimensional (3D) printing application scenarios, e.g., model manufacture, it is necessary to print large-sized objects. However, it is impossible to implement large-size 3D printing using a single projector in digital light processing (DLP)-based mask projection 3D printing because of the limitations of the digital micromirror device chips.

A multi-projector DLP with energy homogenization (EHMP-DLP) scheme is proposed for large-size 3D printing. First, a large-area printing plane is established by tiling multiple projectors. Second, the projector set’s tiling pattern is obtained automatically, and the maximum printable plane is determined. Third, the energy is homogenized across the entire printable plane by adjusting gray levels of the images input into the projectors. Finally, slices are automatically segmented based on the tiling pattern of the projector set, and the gray levels of these slices are reassigned based on the images of the corresponding projectors.

Large-area high-intensity projection for mask projection 3D printing can be performed by tiling multiple DLP projectors. The tiled projector output energies can be homogenized by adjusting the images of the projectors. Uniform ultraviolet energy is important for high-quality printing.

A prototype device is constructed using two projectors. The printable area becomes 140 × 210 mm from the original 140 × 110 mm.

The proposed EHMP-DLP scheme enables 3D printing of large-size objects with linearly increasing printing times and high printing precision. A device was established using two projectors to practice the scheme and can easily be extended to larger sizes by using more projectors.