Assessing the operating reliability of land grid array elastomersockets

The contact resistances of 2300 elastomer button contacts used for LGA (land grid array) package interconnections were measured over a range of contact loads. The experimental data, fitted using three probability distribution functions, show that an inverse Gaussian distribution best describes elastomer button contact resistance behavior. Using this probability function, the minimum operating contact load necessary for a desired socket operating reliability can be determined     

Pharmacokinetics of nicotine carbomer enemas: a new treatment modality for ulcerative colitis

BACKGROUND: Ulcerative colitis is largely a disease of nonsmokers, and transdermal nicotine is of therapeutic value in the active disease. Because side effects are common, we developed a topical enema formulation of nicotine. OBJECTIVE: To study the pharmacokinetics of nicotine complexed with a polyacrylic carbomer and administered by enema to eight healthy volunteers and to eight patients with active ulcerative colitis, verified sigmoidoscopically. PATIENTS AND METHODS: All 16 subjects were nonsmokers. The mean age for normal subjects was 33 years; the mean for patients with ulcerative colitis was 60 years. Median stool frequency for patients with ulcerative colitis was four daily. Patients were taking 5-amino salicylic acid compounds and five were taking oral prednisolone (median dose, 12 mg daily). Nicotine, 6 mg, complexed with carbomer 974P, 400 mg, was administered in a 100 ml enema after an overnight fast, with serial blood measurements taken over 8 hours. Serum nicotine and cotinine were measured by gas liquid chromatography. Area under the concentration-time curves were calculated by the trapezoidal method, and the terminal elimination half-life was derived by extrapolation of the log-linear terminal phase. RESULTS: With the exception of nicotine time to reach peak concentration, which was longer in patients (median of 60 minutes compared with 45 minutes; p < 0.005), other comparisons between normal subjects and patients showed no statistically significant difference, although there was considerable inter-subject variation. Maximum concentration of nicotine, 8.1 +/- 3.5 ng/ml, in the 16 subjects occurred after a median of 60 minutes (range, 30 to 180 minutes); maximum cotinine concentrations of 60.4 +/- 11.5 ng/ml occurred after 4 hours. Side effects in five subjects were mild (four subjects) or moderate (one subject) and included lightheadedness, nausea, and headache; these five subjects were female lifelong nonsmokers of low body weight. CONCLUSION: Because most of the active ingredient of nicotine is converted to continine on the first pass through the liver, substantial concentrations can be achieved at the site of disease with only modest rises in serum nicotine, which are responsible for side effects; cotinine has low pharmacologic activity. Topical administration of nicotine may be useful treatment for distal ulcerative colitis.     

MOEMS chip-level optical fiber interconnect

A package design, fabrication process, and assembly process to hermetically seal the microstructure area of a microoptoelectromechanical system (MOEMS) at the chip level is presented and evaluated. The packaged chip is fabricated using the Bosch deep reactive ion etching (DRIE) process on silicon on insulator (SOI) substrates. The packaging structures are formed during the batch fabrication of the MOEMS device. A hermetic seal is formed via an indium solder ring around the perimeter of the MOEMS chip that span channels etched in the silicon for optical fibers. The seal is made between the device chip, metallized optical fibers, and a cap chip with a fluxless soldering process. The integrity of the package is evaluated through die shear, fiber pull, and highly accelerated life testing (HALT).     

On the use of yielded cost in modeling electronic assemblyprocesses

Yielded cost is defined as cost divided by yield and can be used as a metric for representing an effective cost per good (nondefective) assembly for a manufacturing process. Although yielded cost is not a new concept, it has no consistent definition in engineering literature, and several different formulations and interpretations exist in the context of manufacturing and assembly. In manufacturing, yield is the probability that an assembly is nondefective. To find the effective cost per good assembly that is invested in the manufacturing or assembly process, cost is accumulated and divided by the yield at the end of the process. This paper reviews and correlates existing yielded cost formulations and presents a new approach that enables consistent measurement of sequential process flows. This new approach defines the yielded cost associated with an individual process step (step yielded cost) as the change in the process's yielded cost when the step is removed from the process. This approach is preferred because it incorporates upstream and downstream information and because it provides a prediction of a specific process step's effective cost per good assembly that is independent of step order between steps that scrap defective product     

Optimizing Embedded Passive Content in Printed Circuit Boards

A genetic algorithm's optimization approach is used in conjunction with a size/cost model to study the optimum mix of passives (resistors and capacitors) to embed within a printed circuit board on an application-specific basis. Using the models and solution approach developed in this paper, the effect of board size on the optimum embedded passive solution (minimum cost solution) is studied, and an assessment of whether better system solutions can be found by varying or constraining the size of the board using several different criteria has been performed. Example optimization results for a GSM mobile phone are presented. The analysis has shown that the system size limitation when embedded passives are used is not only dependent on the quantity, type, and electrical properties (capacitance and resistance) of the embeddable components, but is also very sensitive to layout specifications and the placement of the nonembeddable parts.     

Simultaneous determination of azathioprine and 6-mercaptopurine by high-performance liquid chromatography

We investigated whether linear whole-body acceleration along the interaural y-axis influenced the concurrent perception of visual motion direction as has been shown for angular accelerations. A sled running on air bearings along a 7.5-m track was used to accelerate 18 subjects at two different linear accelerations. These young, healthy volunteers, aged 25.50 +/- 7.38 years, used a joystick to indicate whether or not they perceived visual motion to the left within a random-dot kinematogram continuously presented on a monitor moving with them. The percentage of coherently leftward moving pixels presented for a 640-ms period during acceleration was adjusted according to a Modified Binary Search (MOBS) procedure. Six conditions were tested, two acceleration levels of 1 and 2 m/s2 to both left and right with, at the higher acceleration, two different times of visual motion presentation. Conditions were sequenced by means of a 6 x 6 Latin square balanced for order and carry over. A MANOVA did not show any statistically significant effects either for the independent variables acceleration, velocity, and direction of motion of the sled or for their interactions. The results obtained are in clear contrast to those obtained under rotatory stimulation. We conclude that the otolithic contribution to vestibular-visual motion processing is negligible.     

Analyzing multichip module testing strategies

Incorporating test and fault diagnosis as critical design requirements is necessary to achieve high-quality, cost-effective multichip systems. However, evaluating where and when to test, and deciding upon the best test method and level, take considerable study. The authors explore the trade-offs between various MCM test and rework strategies, then analyze the impact of cost, yield, and test effectiveness of the final cost and quality. This analysis of the trade-offs associated with test strategies for complex multichip systems and modules clearly indicate that incorporating DFT and BIST with varying degrees at the chip or MCM levels is economically justifiable. These methods result in cost reduction as well as quality improvement, and indicate that the MCM cost could vary by about 10% to 20%, depending on the test strategy used. However, proper determination of where and how to test, and whether to employ DFT and BIST at the IC or MCM levels, require an evaluation of the economics of the various solutions and the payback. This process is highly dependent on the design under consideration and the parameters associated with the available manufacturing environments     

MESFET simulation oriented toward computer-aided microwave circuitdesign

A MESFET simulator designed to link physically based transistor simulation to microwave circuit simulation within an integrated CAD environment is described. The key features of the simulator are efficient implementation of a large-signal time-domain device simulation kernel; incorporation of extensive postprocessing of raw time-domain data; and an interactive, graphics-oriented user interface. An example that demonstrates the utility of the approach for assessing circuit models is presented