C. Cognetti, E. Stroppolo and R. Tiziani
This paper addresses the themes of resistance to soldering heat and heat dissipation as aspects of reliability in relation to surface mounted devices soldered on a plastic…
Abstract
This paper addresses the themes of resistance to soldering heat and heat dissipation as aspects of reliability in relation to surface mounted devices soldered on a plastic substrate by the most common industrial processes. Reliability data are presented for devices soldered by double wave, multiple wave, vapour phase and infra‐red processes and comments given on the reliability results. In terms of heat dissipation, using an internally developed test pattern and suitable test boards, a study was made of the influence of the substrate on thermal dissipation, thermal impedance, and new medium power SO and PLCC packages offering the possibility of cost‐effective power dissipation in the range of 1.5–2 W while still maintaining a standard outline.
C. Travi, M. Albertini* and C. Gemme*
The increasing level of integration in PCB technology demands from the designer a new level ofsensitivity to high electrical field problems and to the degradation processes that…
Abstract
The increasing level of integration in PCB technology demands from the designer a new level of sensitivity to high electrical field problems and to the degradation processes that may be involved. High electrical fields interacting with thermal and mechanical stresses could lead to the growth of ‘latent defects’, not easily identifiable during final stage acceptance tests, that could lead the PCB's failure during service. The paper discusses degradation mechanisms which can lead to dielectric failure, together with first results relevant to a wider research project regarding identification of latent defects in PCBs and the development of new test procedures.
Details
Keywords
R. Blancquaert, Bob Turnbull, G. Forster, Lorna Cullen, Boguslaw Herod, Steve Muckett and James Lawson
ISHM‐Benelux held its 1987 Autumn Conference on 29 October, at the Antwerp Crest Hotel. This one‐day meeting focused on applications of hybrid circuit technology in various fields…
Abstract
ISHM‐Benelux held its 1987 Autumn Conference on 29 October, at the Antwerp Crest Hotel. This one‐day meeting focused on applications of hybrid circuit technology in various fields of electronic and related industries.
New Officers for 1988/89 ‐ CCA administration for the coming two years will be in the hands of the following office‐bearers:
Q.N. Xiao, F. Grunwald and K. Carlson
Modern electronics is characterised by the increasing level of integration in printedcircuit board (PCB) technology and the reduced insulation spacing between adjacentconductors…
Abstract
Modern electronics is characterised by the increasing level of integration in printed circuit board (PCB) technology and the reduced insulation spacing between adjacent conductors. Surface insulation resistance (SIR) measurement has often been used alone to determine the cleanliness of PCB assembly; however, when proper SIR measurement is used in conjunction with surface leakage current (SLC) measurement, the result can reveal the dynamic nature of surface electrochemical migration (SECM) processes at the microscopic level, and the effect of such processes on product quality and reliability. This paper presents a newly developed measurement methodology, which measures SLC per square unit area at a sampling rate that is orders of magnitude higher than that of conventional SIR measurement methods. It is aimed to capture the transient surge of SLC which is detrimental to the functionality of product.
Details
Keywords
Shih‐Wei Yang, Chern‐Sheng Lin, Shir‐Kuan Lin, Shu‐Hsien Fu and Mau‐Shiun Yeh
The purpose of this paper is to propose an automatic optical inspection system for measuring the surface profile of a microlens array.
Abstract
Purpose
The purpose of this paper is to propose an automatic optical inspection system for measuring the surface profile of a microlens array.
Design/methodology/approach
The system set‐up was constructed according to the principle of the Fizeau interferometer. After capturing the ring interference fringe images of the microlens with a camera, the diameter, profile information and optical properties were analyzed through a microlens surface profile algorithm using innovative image pre‐processing with a precision of less than 0.09 micron.
Findings
By integrating with the genetic algorithm, the XY‐Table shortest moving path of the system is calculated to achieve the purpose of high‐speed inspection and automatic microlens array surface profile measurement.
Originality/value
The measurement results of this system were also compared with other systems, including the atomic force microscope and stylus profiler, to verify the measurement precision and accuracy of this system.
Details
Keywords
This paper aims to report the production of 316L-1 Wt.% NiB cubes by using the selective laser melting (SLM) process. The laser used was pulsed, millisecond Nd:YAG system with…
Abstract
Purpose
This paper aims to report the production of 316L-1 Wt.% NiB cubes by using the selective laser melting (SLM) process. The laser used was pulsed, millisecond Nd:YAG system with maximum average power 100 W.
Design/methodology/approach
Densification under different processing conditions (pulse energy, average laser power, laser scan speed, powder layer thickness, pulse frequency) was investigated. Morphology, macro and microstructure of laser melted samples were characterized by digital camera images and by scanning electron microscope. Density of the cubes was determined by Archimedes method in water. Vickers microhardness of samples was determined under the load of 25 g. Corrosion behavior of 316L and 316L-NiB samples was conducted in 5 per cent HCl solution at the testing temperature of 20°C during 240 h.
Findings
Using laser power of ∼60-70 W, lower beam overlap and powder layer thickness of 200 µm, 3D cubical samples were obtained with significant balling in individual layers and an overall porosity being around 30 per cent. By increasing laser power to ∼80 W, with higher beam overlap and lower powder layer thickness of 100 µm, SLM parts with no balling and the presence of small pores of up to 4 per cent (20 Hz) and 9 per cent (40 Hz) were obtained. With further increase of laser power to 90 W, overall porosity rose to around 12 per cent. The addition of 1 Wt.% NiB to stainless steel negligibly lowered its corrosion resistance in 5 per cent HCl solution.
Originality/value
A part from 316L stainless steel with balling-free structure and good density was successfully obtained through pulsed-SLM process with the aid of 1 Wt.% of NiB addition. Aside from significant influence on the improved structure of cubes, NiB had a favorable effect on microhardness values while practically not affecting the corrosion resistivity of the base material in an aggressive surrounding.
Details
Keywords
Rajesh Siriyala, A. Gopala Krishna, P. Rama Murthy Raju and M. Duraiselvam
Since, wear is the one of the most commonly encountered industrial problems leading to frequent replacement of components there is a need to develop metal matrix composites (MMCs…
Abstract
Purpose
Since, wear is the one of the most commonly encountered industrial problems leading to frequent replacement of components there is a need to develop metal matrix composites (MMCs) for achieving better wear properties. The purpose of this paper is to fabricate aluminum MMCs to improve the dry sliding wear characteristics. An effective multi-response optimization approach called the principal component analysis (PCA) was used to identify the sets of optimal parameters in dry sliding wear process.
Design/methodology/approach
The present work investigates the dry sliding wear behavior of graphite reinforced aluminum composites produced by the molten metal mixing method by means of a pin-on-disc type wear set up. Dry sliding wear tests were carried on graphite reinforced MMCs and its matrix alloy sliding against a steel counter face. Different contact stress, reinforcement percentage, sliding distance and sliding velocity were selected as the control variables and the response selected was wear volume loss (WVL) and coefficient of friction (COF) to evaluate the dry sliding performance. An L25 orthogonal array was employed for the experimental design. Optimization of dry sliding performance of the graphite reinforced MMCs was performed using PCA.
Findings
Based on the PCA, the optimum level parameters for overall principal component (PC) of WVL and COF have been identified. Moreover, analysis of variance was performed to know the impact of individual factors on overall PC of WVL and COF. The results indicated that the reinforcement percentage was found to be most effective factor among the other control parameters on dry sliding wear followed by sliding distance, sliding velocity and contact stress. Finally the wear surface morphology of the composites has been investigated using scanning electron microscopy.
Practical implications
Various manufacturing techniques are available for processing of MMCs. Each technique has its own advantages and disadvantages. In particular, some techniques are significantly expensive compared to others. Generally the manufacturer prefers the low cost technique. Therefore stir casting technique which was used in this paper for manufacturing of Aluminum MMCs is the best alternative for processing of MMCs in the present commercial sectors. Since the most important criteria of a dry sliding wear behavior is to provide lower WVL and COF, this study has intended to prove the application of PCA technique for solving multi objective optimization problem in wear applications like piston rings, piston rods, cylinder heads and brake rotors, etc.
Originality/value
Application of multi-response optimization technique for evaluation of tribological characteristics for Aluminum MMCs made up of graphite particulates is a first-of-its-kind approach in literature. Hence PCA method can be successfully used for multi-response optimization of dry sliding wear process.
Details
Keywords
Abdul Maleque and Rezaul Karim
The purpose of this paper is to study the wear behavior of as‐cast (AC) and heat treated (HT) triple particle size (TPS) silicon carbide (SiC) reinforced aluminum alloy‐based…
Abstract
Purpose
The purpose of this paper is to study the wear behavior of as‐cast (AC) and heat treated (HT) triple particle size (TPS) silicon carbide (SiC) reinforced aluminum alloy‐based metal matrix composites (SiCp/Al‐MMC).
Design/methodology/approach
Al‐MMCs were prepared using 20 vol.% SiC reinforcement into aluminum metal matrix and developed using a stir casting process. Stir casting is a primary process of composite production whereby the reinforcement ingredient material is incorporated into the molten metal by stirring. The TPS composite consist of SiC of three different sizes viz., coarse, intermediate, and fine. The solution heat treatment was done on AC composite at 540°C for 4 h followed by precipitation treatment. The wear test was carried out using a pin‐on‐disc type tribo‐test machine under dry sliding condition. A mathematical analysis was also done for power factor values based on wear and friction results. The wear morphology of the damaged surface was also studied using optical microscope and scanning electron microscope (SEM) in this investigation.
Findings
The test results showed that HT composite exhibited better wear resistance properties compared to AC composite. It is anticipated that heat treatment could be an effective method of optimizing the wear resistance properties of the developed Al‐MMC material.
Practical implications
This paper provides a way to enhance the wear behavior of automotive tribo‐components such as brake rotor (disc and drum), brake pad, piston cylinder, etc.
Originality/value
This paper compares the wear behavior of AC and HT TPS reinforced Al‐MMC material under dry sliding condition.
Details
Keywords
Paulraj Sathiya, M.Y. Abdul Jaleel and B. Shanmugarajan
Laser welding under high power, high degree of automation and high production rate is extremely advantageous in automotive application. Super austenitic stainless steel is the…
Abstract
Purpose
Laser welding under high power, high degree of automation and high production rate is extremely advantageous in automotive application. Super austenitic stainless steel is the preferable material for high corrosion resistance requirements. These steels are relatively cheaper than austenitic stainless steel and it is expensive than nickel base super alloys for such applications. The main purpose of this paper is to present the investigations of the microstructure and mechanical properties of super austenitic stainless steel butt joints made by 3.5 kW cooled slab CO2 laser welding using different shielding gases such as argon, nitrogen and helium.
Design/methodology/approach
The tensile and impact tests were performed and the fractured surfaces were analyzed by scanning electron microscope. The hardness across the joint zone was measured. The X‐ray diffraction technique was used to analyze the phase composition. The microstructure of the laser welds were analyzed through optical microscopy.
Findings
The tensile sample fractures indicate that the specimen fails in a ductile manner under the action of tensile loading. The impact fracture surfaces of the different shielding gas laser welded joints show mixed mode fractures, that is, ductile and cleavage fractures. The hardness values of the Helium shielded laser joints in the weld metal regions are much higher than the others.
Research limitations/implications
There is no limitation, except for the availability of the high beam power laser welding machine.
Practical implications
The only practical implication is the laser welding shop hazard during the experiment.
Social implications
Social implication is limited. The only hazard during the laser welding is that it may affect human body tissues.
Originality/value
The research work described in the paper is original.