Pitch Components Research Articles

Envelope-invariant speech coding based on sinusoidal analysis of LPC residuals and with pitch conversion of voiced speech

To conduct pitch control of a voiced speech signal that is to be coded or decoded, the voiced signal is subjected to sinusoidal analysis coding for each coding unit obtained by dividing the voiced signal on the time axis at a predetermined coding unit. A linear predictive residual of the voiced signal is taken out, and resultant voiced signal coded data are processed. A pitch component of the voiced signal coded data coded by the sinusoidal analysis coding is altered without changing the phonemes by a predetermined computation processing in a pitch conversion unit.

Oxidative stabilization of C/C tow pregs studied by light microscopy

Tow pregs obtained from polyacrylonitrile-based carbon fibres and a commercial binder coal-tar pitch were stabilized by oxidation at 548, 588 and 623 K for periods ranging between 1 and 15 h. The microstructural changes involved in the stabilization of tow pregs on the carbonized laminates were studied by light microscopy. Under the conditions studied, the oxidative stabilization of tow pregs produced a significant increase in carbon yield. At the same time, the development of porosity on carbonization was avoided and the size of the optical texture was reduced. However, the extreme oxidation of pitch components at the edges of the carbonized laminate adversely affected pitch binding capability and the sinterizability of the laminates.

The Acquisition of the Pitch Element of Music Literacy Skills by 3-4-year-old Pre-school Children: A Comparison of Two Methods

This study compared the acquisition of the pitch component of music literacy skills between three groups of pre-school children aged 3-4 years. The Control Group received no tuition at all, while the two teaching groups received 20 tenminute teaching sessions. The children in the StimEquiv Group were taught using a method based on stimulus equivalence whilst those in the Context Group were taught using a method based on spatial and contextual information processing. The children in both teaching groups learned up to five notes and were able to play simple, unlearned melodies made up of these notes 3-5 days after the end of the teaching period (post-test). Preto post-test gains in the accuracy of the playing of these melodies were significant (p < 0.001) for both groups. There was no significant difference found between the preand post-test scores of the Control Group. The children in the teaching groups were given a further test seven weeks after completion of the sessions. There was no significant difference for either group between post-test and re-test indicating that learning had occurred. As they had not been exposed to the intervention, the re-test (a measure of learming) was not given to the Control Group.

Optimizing BGA to PCB interconnections using multi‐depth laser drilled blind vias‐in‐pad

Ball grid array (BGA) component packages challenge the circuit board design with signal routing and layout, creating in some cases extra board layers and added vias all resulting in increased costs for the printed circuit board (PCB). As component densities increase and microBGA (μBGA) and other fine pitch components become more common, microvia‐in‐pad technology will ease the transition to these fine pitch components. This paper presents and profiles a cost‐effective solution to interconnecting BGAs on PCBs using laser drilled blind vias connecting the outer three or more layers of a multilayer circuit board. Following a discussion on the design advantages, a comprehensive outline of the PCB fabrication process explores a new procedure for the rapid production of via‐in‐pad multi‐depth blind via laser drilling.

The ‘‘cocktail-party effect’’ viewed through the lens of psychophysics

In an attempt to understand the psychophysical processes underlying the ‘‘cocktail-party effect’’—a phenomenon whereby one speech signal is extracted from the ensemble of other speech signals distributed in space—it has been reduced to the psychophysical task of segregating two concurrent signals X1(t) and X2(t) differing with respect to various attributes. These attributes represent three orthogonal ‘‘canonica’’ dimensions—spatial location, temporal (low-frequency envelope AM) structure, and pitch, although the pitch dimension is split into spectral and virtual pitch components. In any segregation experiment, the two signals differ along at least two attributes; segregation is assumed when each signal is associated with the correct values on each dimension. At segregation threshold, there is a trade-off over a certain range, where an increased difference along one dimension leads to a reduced difference along another. Along each dimension, there is also a ‘‘critical’’ difference at which the trade-off no longer exists. When converted to speech parameter coordinates, these critical differences—for azimuthal, spectral, fundamental frequency, and modulation frequency separation—can provide psychophysical predictions for conditions under which a speech signal could be successfully recovered in a real-life cocktail-party situation. [Work supported by the National Institute on Aging and the VA.]

SOLDER PASTE DEPOSITION THROUGH HIGH SPEED STENCIL PRINTING FOR A CONTRACT ASSEMBLY ENVIRONMENT

Maximizing the throughput of an assembly line while concurrently ensuring good quality and high reliability is the primary focus of a contract printed circuit board assembly environment. Reduction of the cycle time associated with the assembly process, therefore, is of prime importance. The surface mount assembly steps include stencil printing, component placement and reflow soldering. Stencil printing is typically not the bottleneck in the assembly sequence. However, there are specific assemblies in which the stencil printing operation is the bottleneck. This research focused on reducing the cycle time associated with the stencil printing step by increasing the print speed. Designed experiments were carried out on commercially available solder pastes to investigate their ability to be stencil printed at high speeds (76 to 178 mm per second). A wide range of component types, including ball grid arrays and 0.3-mm (12 mil) pitch ultrafine pitch components, were studied. The heights of the solder paste deposits and the print definition obtained were the response variables considered. This study also determined the impact of various squeegee materials and powder sizes on solder paste deposition. It was observed that some newer commercially available solder paste formulations could be consistently and repeatably deposited at print speeds up to 178 mm (7 inches) per second.

Integration steps of a fully-automated remanufacturing cell system for fine-pitch surface mounted devices

Surface mounted components have become the choice of the electronics manufacturing industry to allow the production of complex circuit boards. New components using increased lead counts on finer pitches make successful assembly difficult. The increased complexity, cost, and lead count of the surface mount technology (SMT) components, and also the increasing compactness of the SMT assemblies have demanded the creation of newer rework tools as an essential part of electronics manufacturing. Therefore, it becomes essential to have a well-controlled process to assure that rework is not only possible but that it is consistent and flawless. Automation is the common answer to achieve both efficiency and quality. This paper describes a remanufacturing cell for the automated rework of fine pitch components that is under development at the Center for Integrated Electronics and Electronics Manufacturing (CIEEM) at Rensselaer.

Component registration diagnosis for printed circuit boards using process-oriented basis elements

Modern product and process sensors are capable of making repeated measurements of similar characteristics at multiple locations on a part. Under such conditions, is possible to produce process diagnostic analyzing the multivariate process vector using a process-oriented basis (POB). Many potential production problems will have characteristic signatures that can be detected in the multivariate quality vector. Each pattern (signature) is associated with a basis element in the POB. The multivariate quality vector can be represented as a linear combination of these basis elements. Patterns with large coefficients in the representation suggest particular causes for process problems allowing manufacturing diagnostic information to be derived from the decomposition of the multivariate SPC data. The methodology is applied to the registration problem in fine pitch components for Printed Circuit Boards (PCB). Each PCB panel consists of 16 components, each of them with 8 measurements, resulting in a multivariate vector of 128 components. The suggested control procedure monitors through control charts the representation of each defined pattern to identify time periods in which such patterns are active.

Influence of pitch air‐blowing and thermal treatment on the microstructure and mechanical properties of carbon/carbon composites

This paper discusses the optimization of pitch properties as a matrix precursor of C/C composites by subjecting the pitches to different pretreatments to promote polymerization of the molecular components of pitch, which could improve carbon yield and density of the resultant carbon materials. Two series of pitches were prepared by air‐blowing of impregnating coal‐tar pitches at temperatures between 523 and 573 K, and thermal treatment at temperatures between 673 and 703 K, in an inert atmosphere. Effects of pitch treatments on resultant coke texture and porosity were monitored by polarized light microscopy. Unidirectional laminar composites were prepared using the original and treated pitches and commercial PAN‐based carbon fibres. Effects of pitch treatments on the main microstructural features of composites are determined by scanning electron microscopy and polarized light microscopy, and related to the mechanical properties of composites. Results show an improvement of the mechanical properties of composites in both series, particularly for pitch treatments at 523 K/air in the air‐blown series, and at 698 K–5 h in the thermally treated one.

Donor-acceptor interaction as an effective method for study of the structure of highly condensed components of coal-tar pitch in carbonization

Donor-acceptor interaction as an effective method for study of the structure of highly condensed components of coal-tar pitch in carbonization

THE SOLDERABILITY EVALUATION OF SURFACE MOUNT COMPONENTS THROUGH THE USE OF WETTING BALANCE ANALYSIS

Solderability is an important concern in the surface mount assembly of Printed Circuit Boards (PCBs). It impacts assembly reliability and yield. The solderability requirement of the components and boards used in surface mount PCB assembly is critical since the solder joint needs to provide both the electrical and the mechanical connections. The advent of ultrafine pitch components has only helped to increase the importance of solderability in surface mount assembly. Solderability evaluation for surface mount components and the identification and study of factors that influence it are of primary importance in the surface mount assembly of PCBs. The wetting balance can provide a quantitative investigation of solderability through measurement of wetting speed and the wetting force. It has been used for the solderability testing of through hole components. The use of the wetting balance apparatus for the testing of surface mount components raised several concerns. Some modifications were made to simplify the testing operations, to enhance the precision of the wetting balance apparatus and to enable the collection of more accurate data. The preliminary experiments explored the nature of the wetting balance test and helped identify a standardized process that could provide valid conclusions. A set of validated test parameters and a standardized set of test procedures that could be used to perform the incoming solderability testing of surface mount components were established. While the test procedures used in this research were a derivative of the IPC ANSI J-STD-002 standard, changes were made based upon the experience gained through the test schedule and the results and inferences obtained through preliminary experiments. Various types of mass reflow surface mount components were measured by their relative solderability. The solderability of tape automated bonding components with various plating metallurgy and coating thicknesses was also tested. The specific testing parameters used, the test procedures adopted, the data collected and the inferences made are presented in this paper.

The role of low-molecular-weight components in the pyrolysis of pitches

Two pitches of different volatile contents, obtained from the same coal tar by different procedures, were characterized by elemental analysis, solubility, 1H n.m.r., donor—acceptor ability, FT-i.r., extrography and size-exclusion chromatography. Their pyrolysis behaviour was followed by hot-stage microscopy and thermogravimetric analysis. The pitches were carbonized in a horizontal furnace and the resulting cokes were characterized by optical microscopy. Three partly devolatilized pitches were prepared by thermal treatment of the two pitches and their pyrolysis behaviour was compared in terms of mesophase development and optical texture of coke. The results indicate a significant influence of low-molecular-weight components of pitch on the development of mesophase but no effect on the subsequent optical texture of the coke.

A "CLOSED LOOP" SYSTEM FOR THE REALTIME CONTROL OF SOLDER PASTE STENCIL PRINTING

The move towards fine and ultrafine pitch components in surface mount Printed Wiring Board (PWB) assembly has increased the importance of the solder paste printing process. The quality of the solder paste deposit is influenced by factors such as the characteristics of the board, the solder paste selected, the printer used, etc. These inter-related process and material factors complicate the procedures and the reasoning used to identify and set-up the stencil printing parameters. The increased use of ultrafine pitch components (with lead pitch down to 0.4 mm) in PWB assembly has almost made it mandatory to inspect the solder paste deposit prior to component placement. This inspection process provides the necessary information to correct the printing process in a realtime fashion if printing is out of control or is exhibiting a tendency to go out of control.This research designed and developed a "closed-loop" system for realtime control of the solder paste stencil printing process. This knowledge based process control system interfaces with a stencil printer and a laser based solder paste inspection system to form the "closed-loop". This "closed loop" realtime system insures both proactive and reactive control of the stencil printing process.

High Quality Solder Pastes:

As electronic devices have become more complex and interconnection density has increased, electronics manufacturers are facing new challenges to solder SMD packages with pitches down to 0.3 mm or less. To achieve positive results, all parameters throughout the soldering process have to be optimised. The first step on the SMT line is the application of solder paste. Any faults at this stage (material, equipment or process related) will be carried through the entire production line. Solder paste is one of the most important factors in the whole chain. It is important to understand the influence of the metal powders, activators, solvents and additives on soldering of ultra‐fine pitch SMDs. Special attention must be paid to the powder (fine pitch devices demand a fine grain in the solder paste). The reliability of the soldered joints is mainly dependent (apart from on the solder paste) on the solder quantities applied to the component pads, the tolerance regarding the shape and size of stencils + PCBs + SMDs, the accuracy of mounting and printing, and on the reflow profile. It is important to design the stencil apertures with sufficient surface area to provide enough surface tension (between the paste and the component pad) to pull the solder paste out of the stencil, while keeping the component pad small enough to match the lead of the component. As the wetting of fine pitch components is especially critical, it is necessary to pay more attention to the design of the reflow profile. It is recommended to solder ultra‐fine pitch components under nitrogen, as this enlarges the process window considerably.

Surface mounting of very fine pitch components: a new challenge

In this study the degradation and reliability of a plastic encapsulated RF switching device were assessed by comparing several lots of a device that came directly off the assembly line to several other lots which had been subjected to accelerated stress testing. Comparisons of the structure, die and wirebonds were based on the results of examinations using optical microscopy, X-ray analysis, scanning acoustic microscopy, environmental scanning electron microscopy and wire bond pull tests.

New Products

Du Pont has introduced a new range of low residue solder pastes, specially developed for the attachment of fine pitch and other surface mount components to printed circuit boards and ceramic substrates without the need for post‐assembly cleaning.

PPA-A precise, data driven component tool

This paper outlines the development of a data-driven, fine pitch component placement machine, PPA-A, which is an integrated robotic workcell developed for attaching fine pitch integrated circuit components to printed circuit boards. In particular, the objectives for the machine are reviewed, and an overview of the solution is given. Problems encountered during the development are discussed, and details of the algorithms developed to solve these problems are given. These problems relate to achieving very precise placement of components, and are solved by novel calibration and execution schemes. >

Surface mounting of very fine pitch components: a new challenge

Based on their experience in developing and using 16 and 12.5 mils peripheral pitch custom compact single chip packages, the authors analyze the evolution and today's limits of package and board technologies and assembly techniques, with emphasis on manufacturability. The authors present their manufacturing approach and quality and reliability results when using 16 and 12.5 mils peripheral ceramic leaded packages. A detailed analysis of packaging processes and limitations is performed for high pin count ceramic and plastic packages. Competitive packaging methods, pin grid arrays, land grid arrays, and tape automated bonding are compared, and trends for the future are analyzed. >

Some aspects of a realistic three-dimensional pursuit-evasion game

A three-dimensio nal pursuit-evasion game between a realistic missile and an aircraft is studied employing point-mass models for both vehicles. Since a direct method to solve this complicated mini-max problem is too time-consuming, the study is conducted by carrying out massive simulations in the parameter space of initial conditions and guidance law parameters. The important role of information in the opponent's acceleration to the game and the effectiveness of the strategy in rotating the line-of-sight vector are shown. It is found that there exist very few cases where the aircraft can avoid the missile, among them typical air-combat maneuvers such as linear acceleration, high-£ barrel roll, split-S, and horizontal-S. Nomenclature flcmax = missile lateral acceleration command limit Ompjdmy = missile acceleration components measured in aircraft pitch and yaw axis, respectively ^p^y^pc^yc = missile-pitch and yaw-axis lateral accelerations and their command signals OpttOyt = aircraft-desir ed pitch and yaw acceleration components, respectively Otp9oty = aircraft acceleration components measured in missile pitch and yaw axis, respectively CD = drag coefficient CDO

Nystagmus induced by electrical stimulation of the vestibular and prepositus hypoglossi nuclei in the monkey: evidence for site of induction of velocity storage

Electrical stimulation of the vestibular nuclei (VN) and prepositus hypoglossi nuclei (PPH) of alert cynomolgus monkeys evoked nystagmus and eye deviation while they were in darkness. At some sites in VN, nystagmus and after-nystagmus were induced with characteristics suggesting that velocity storage had been excited. We analyzed these responses and compared them to the slow component of optokinetic nystagmus (OKN) and to optokinetic after-nystagmus (OKAN). We then recorded unit activity in VN and determined which types of nystagmus would be evoked from the sites of recording. Nystagmus and eye deviations were also elicited by electrical stimulation of PPH, and we characterized the responses where unit activity was recorded in PPH. Horizontal slow phase velocity of the VN "storage" responses was contralateral to the side of stimulation. The rising time constants and peak steady-state velocities were similar to those of OKN, and the falling time constants of the after-nystagmus and of OKAN were approximately equal. Both the induced after-nystagmus and OKAN were habituated by stimulation of the VN. When horizontal after-nystagmus was evoked with animals on their sides, it developed yaw and pitch components that tended to shift the vector of the slow phase velocity toward the spatial vertical. Similar "cross-coupling" occurs for horizontal OKAN or for vestibular post-rotatory nystagmus elicited in tilted positions. Thus, the storage component of nystagmus induced by VN stimulation had the same characteristics as the slow component of OKN and the VOR. Positive stimulus sites for inducing nystagmus with typical storage components were located in rostral portions of VN. They lay in caudal ventral superior vestibular nucleus (SVN), dorsal portions of central medial vestibular nucleus (MVN) caudal to the abducens nuclei and in adjacent lateral vestibular nucleus (LVN). More complex stimulus responses, but with contralateral after-nystagmus, were induced from surrounding regions of ventral MVN and LVN, rostral descending vestibular nucleus and the marginal zone between MVN and PPH. Vestibular-only (VO), vestibular plus saccade (VPS) and tonic vestibular pause (TVP) units were identified by extracellular recording. Stimulation near type I lateral and vertical canal-related VO units elicited typical "storage" responses with after-nystagmus in 23 of 29 tracks (79%). Stimulus responses were more complex from the region of neurons with oculomotor-related signals, i.e., TVP or VPS cells, although after-nystagmus was also elicited from these sites. Effects of vestibular nerve and nucleus stimulation were compared.(ABSTRACT TRUNCATED AT 400 WORDS)