Showing papers in "Circuit World in 1989"
TL;DR: In this paper, a new technology is proposed that offers the user unparalleled resolution, a completely aqueous system, and complete, uniform, three-dimensional coverage of the panel.
Abstract: Line widths are rapidly shrinking and the complexities of boards place increased demands on the resolution capabilities of the photoresists. A new technology is emerging that offers the user unparalleled resolution, a completely aqueous system, and complete, uniform, three‐dimensional coverage of the panel. The unique properties of this system result from the extraordinary method of application of the photoresist. Electrophoresis, or electrocoating, allows the deposition of a very thin, uniform, highly chemically resistant photoresist layer. Any exposed conductive surface, including scratches or other panel imperfections, are coated. The combination of a very thin layer and no cover sheet allows the printing of sub‐mil geometries without the need for a collimated light source. This new application offers the user high yields, both from the chemistry and in circuit yields. Even more so, the resolution capabilities offer opportunities beyond the limitations of dry film and other liquid resists. The photoresist no longer needs to be the gating factor in process capability.
17 citations
TL;DR: In this paper, the performance of laminate materials is taken into account when designing and fabricating high speed PWBs and various combinations of polymer resins and reinforcements used in these applications.
Abstract: This paper reviews some of the technology trends making it necessary to take the performance of laminate materials into account when designing and fabricating high speed PWBs. It also reviews the available materials for current matched impedance circuitry and discusses the various combinations of polymer resins and reinforcements used in these applications. Additionally, it provides a look at the new materials technologies being applied to high speed applications and what candidates hold most promise for achieving greater signal speeds via lowered dielectric constant while maintaining the compatibility with existing fabrication processes.
8 citations
TL;DR: The role of chlorofluorocarbons (CFCs) in the observed depletion of the Earth's stratospheric ozone, plus details of the Montreal Protocol that restricts the production and consumption of CFCs are given in this article.
Abstract: An earlier paper gave the background to the role of chlorofluorocarbons (CFCs) in the observed depletion of the Earth's stratospheric ozone, plus details of the Montreal Protocol that restricts the production and consumption of CFCs. In this paper, recent data on both the ozone depletion and the global greenhouse warming that result from CFC emissions are given. The progress by the chemical companies to identify replacements for CFCs is also discussed.
6 citations
TL;DR: In this article, a study has been carried out employing a vibratory motor, offering amplitudes of 0·4-4 mm at 50 Hz in acid copper sulphate as a model electrolyte in which α-Al2O3 particles are suspended for co-deposition, yielding a composite electrodeposit.
Abstract: A study has been carried out employing a vibratory motor, offering amplitudes of 0·4–4 mm at 50 Hz in acid copper sulphate as a model electrolyte in which α‐Al2O3 particles are suspended for co‐deposition, yielding a composite electrodeposit. Using a horizontal disc vibrator at the bottom of the container, perforated discs have been shown to give superior agitation and a laminar/turbulent transition has been identified. Incorporation of particles is a maximum at the transition. In the laminar regime Sh‐Re0·037 and in the turbulent regime Sh‐Re0·82. Mass transport enhancement was measured for a variety of disc and tank diameters and enhancement factors for electrodeposition of 3–40 times were obtained. In these circumstances a modified Reynolds number Re1 was employed Re1 = 100 ad2(d1−d2)/υd2 and, assuming a conventional dependence upon Sc, a full correlation of the type Sh1 = constant Re1a Sc0·33 was obtained where the constant took values of 10–40 and ‘a’ took values of 0·83–1·1 depending upon precise location within the tank of the mass transfer probe.
6 citations
TL;DR: In this article, the major causes of changes in composition of deposits plated from solutions based on fluoboric acid and organic sulphonic acid are examined and the methods available for measuring the deposit composition are also discussed.
Abstract: Alloys deposited from plating solutions vary in composition with changes in solution constituents and processing parameters. With the increasing demand on miniaturisation and quality of subsequent solder joints made to plated tin‐lead alloys, it is important to ensure stable deposit composition and also to know to what extent changes in operating conditions will affect the composition. This paper examines the major causes of changes in composition of deposits plated from solutions based on fluoboric acid and organic sulphonic acid. The methods available for measuring the deposit composition are also discussed.
6 citations
TL;DR: In this paper, a sensitive and quantitative wetting balance method has been studied with the purpose of developing a better alternative to the "dip and look" procedure, which is subjective, so the results can vary from person to person and from day to day.
Abstract: With the increased use of surface‐mounted devices, both the component density and the board complexity are greatly increased on many circuit pack assemblies. Good solderability for the components as well as for the printed circuit boards has become one of the most important elements in achieving the ultra‐high efficiency and quality required of an assembly soldering process in today's competitive environment. Solderability evaluation generally uses the ‘dip and look’ method that relies entirely on the individual inspectors' often inconsistent interpretations resulting from the examination of the specimen dip‐tested in a molten solder bath. This method is subjective, so the results can vary from person to person and from day to day. In addition, the sensitivity of such a method is inadequate in discerning the differences in solder wetting characteristics of very small device leads and terminations. Consequently, components with marginal or even bad solderability may pass through inspection and move onto the production line to cause many easily avoidable defects and their subsequent repairs. A sensitive and quantitative wetting balance method has been studied with the purpose of developing a better alternative to the ‘dip and look’ procedure. Special sample holders and test conditions have been developed for testing various types of components and printed circuit board coupons. Examples of solderability testings are provided to illustrate the capability of the instrument when proper testing procedures are followed. More effort is under way to simplify the test procedure, and to establish a practical solderability test standard for the wetting balance method.
6 citations
TL;DR: In this paper, the exact SIR per square correlation has been found over an order of magnitude of pattern conductor space widths, and critical experimental techniques to modify the FR•4 epoxy surface appropriately and an important theoretical hypothesis involving shadowing are developed.
Abstract: For reliable telecommunication systems, Bellcore recommends that Surface Insulation Resistance (SIR) be monitored at key points in printed wiring board and circuit pack manufacturing. The Bellcore SIR criteria are based on the old ‘Bell System’ test pattern having 0·025 inch conductor line widths, and 0·050 inch conductor spacings. Since divestiture, many equipment suppliers have suggested using different test patterns, or even conductors on actual product for SIR testing. Also, with the trend to high density packaging and smaller conductor spacings, the Bellcore pattern now represents old technology. This work confirms and advances prior work suggesting pattern translation based on the SIR per square concept. Essentially exact SIR per square correlation has been found over an order of magnitude of pattern conductor space widths. Critical experimental techniques to modify the FR‐4 epoxy surface appropriately and an important theoretical hypothesis involving shadowing (proven experimentally) are developed in this work.
6 citations
TL;DR: In this article, both destructive and non-destructive test methods for evaluation of TAB bonds are analysed and criticised, and the key parameters and general guidelines of a destructive beampull test set-up are identified and presented.
Abstract: Tape automated bonding (TAB) is one technology which is becoming widely adopted for interconnecting integrated circuits to a substrate or package. Both destructive and non‐destructive test methods for evaluation of TAB bonds are analysed and criticised. The key parameters and general guidelines of a destructive beampull test set‐up are identified and presented. The key features of four different non‐destructive test methods are described and discussed. It is found that no universal solution exists for non‐destructive evaluation of TAB bonds although some methods may be more useful than others under certain conditions and constraints. Data and experimental procedure are presented for correlation of scanning laser acoustic microscopy and beampull data.
5 citations
TL;DR: The chemistry of the deposition of white residues is complex; the deposits themselves are of a number of types and origins, and their incidence is associated with both materials and process parameters as discussed by the authors.
Abstract: Visible surface residues, commonly referred to as white residues, on soldered printed circuit assemblies are a very common but intermittent and unpredictable problem. Such residues, which are insoluble in normal solvents, are generally a rejectable condition. The chemistry of the deposition of white residues is complex; the deposits themselves are of a number of types and origins, and their incidence is associated with both materials and process parameters. This paper attempts to identify the different causes of the problem and suggest ways in which avoidance or removal is possible.
5 citations
TL;DR: In this paper, the major techniques for inspection of electronic components, assemblies, and interconnections are discussed and summarised, and the difficulties of detecting some flaws with some techniques are highlighted and the reasons considered.
Abstract: There is an increasing requirement for inspection of electronic components, assemblies and interconnections, and to meet this demand there are new developments in inspection techniques. None of the techniques is universally applicable, but many are capable of consistent and reliable results. This paper outlines the major techniques which are available and summarises their capabilities. The limitations on types of component and boards which may be examined are listed, and the difficulties of detecting some flaws with some techniques are highlighted and the reasons considered.
4 citations
TL;DR: A general survey of the methods of contamination control related to assembled printed circuits is given in this paper, with particular emphasis on those aspects of the subject which are currently in a state of change because of environmental difficulties, notably those due to the curtailment of use of chlorofluorocarbon solvents.
Abstract: This paper gives a general survey of the methods of contamination control related to assembled printed circuits. Particular emphasis is given to those aspects of the subject which are currently in a state of change because of environmental difficulties, notably those due to the curtailment of use of chlorofluorocarbon solvents.
TL;DR: The arrival of low solids content flux on the electronics production market represents something of a revolution as discussed by the authors, and it is therefore surprising to find that today fluxes containing between 2% and 10% rosin can be both efficient and cost-effective.
Abstract: The arrival of low solids content flux on the electronics production market represents something of a revolution. Traditionally, the electronics industry has used, and is still using, successfully rosin fluxes containing between 15% and 35% solids content, for wave soldering electronics assemblies (PTH and single‐sided PCBs). It is therefore surprising to find that today fluxes containing between 2% and 10% rosin can be both efficient and cost‐effective.
TL;DR: In this paper, the application of a unique pulsed current technique to the acid copper Electrolyte used in the PCB industry is described. But the application is limited to a single circuit.
Abstract: The paper outlines the application of a unique Pulsed Current technique to the Acid Copper Electrolyte used in the PCB industry. It discusses some of the inherent difficulties associated with conventional DC plating and how these pulsing techniques can overcome them to enable the production of a higher quality product despite the ever increasing demands being placed on manufacturers for better distribution and through‐hole plating.
TL;DR: In this paper, the history of an investigation of white residue on solder masked printed wiring assemblies was presented. But the residue was determined to be flux related by experimentation and spectroscopic chemical analysis.
Abstract: Residues associated with soldering operations are common throughout the electronics manufacturing industry. Prevention is necessitated by MIL specs which require soldered assemblies to be free of all residues. Because of the large number of variables which contribute to residue formation, residues frequently appear under seemingly constant conditions, and detailed understanding of the materials and processes involved is needed for corrective action implementation. This paper presents the history of an investigation of white residue on solder masked printed wiring assemblies. The residue was determined to be flux related by experimentation and spectroscopic chemical analysis. Process modification testing was performed to evaluate the roles of flux identity, preheater temperatures and several cleaning process variables. Assemblies were subjected to humidity and temperature cycling, including periodic examination and electrical testing. Additionally, information learned during this investigation about a numb...
TL;DR: In this article, the authors present some of the concerns encountered in wave soldering of surface mount assemblies and present a solution to these concerns using surface mount technology, which is the most popular and economical method for mass soldering.
Abstract: For over 30 years, wave soldering has been the most popular and most economical method for mass soldering of electronic assemblies. For conventional circuits, this is a mature technology. Training, proper board design, process control during board fabrication, assembly and soldering and, finally, an awareness of the need for solderability have resulted in very high manufacturing yields in some companies with the associated high quality and much improved profits which result by doing it right the first time. With the introduction of surface mount technology, the same concerns need to be addressed. However, due to the smaller size of components and higher densities, new problems arise. This paper presents some of the concerns encountered in wave soldering of surface mount assemblies.
TL;DR: In this article, a computer program was used to predict the coefficient of thermal expansion (CTE) of four printed wiring board (PWB) designs, which consisted of low CTE materials, E glass/epoxy and copper.
Abstract: A computer program was used to predict the coefficient of thermal expansion (CTE) of four printed wiring board (PWB) designs. Designs consisted of low CTE materials, E glass/epoxy and copper. Twenty PWBs were fabricated to duplicate four computer models. CTE was measured by a strain gauge technique developed at Boeing. The measured CTE was then compared with the predicted CTE value and a design curve developed. Following CTE verification, the PWBs were assembled with 20, 44, 68, and 84 I/O leadless ceramic chip carriers. The printed wiring assemblies were then thermal shocked from −55 to 125°C and continuously monitored to detect the first solder failure for each I/O chip carrier. The results illustrate the dependence of solder joint life on PWB CTE and verify the use of a computer model to design surface mount PWBs.
TL;DR: In this article, the current problems of finding substitutes for chlorofluorocarbon (CFC) solvents which are becoming regulated for environmental reasons are described, mainly from the points of view of air and water pollution and operator health and safety.
Abstract: This paper describes the current (April 1989) problems of finding substitutes for chlorofluorocarbon (CFC) solvents which are becoming regulated for environmental reasons. The cleaning products discussed are hydrochlorofluorocarbons, hydrochlorocarbons, chlorocarbons, water, aqueous saponifiers, light hydrocarbons and terpene/surfactant mixtures. These are examined primarily from the points of view of air and water pollution and operator health and safety. Secondarily, the factors of cost and cleaning efficiency are discussed.
TL;DR: In this article, a peel test was performed to quantitatively measure the adhesion of dry film photoresist on copper surfaces, and the results led to the following conclusions: a tin-silane (SNS) treated copper surface with a peeling strength of 4-7 lbs/in.
Abstract: This study describes a peel test to quantitatively measure the adhesion of dry film photoresist on copper. Using this peeling method, the adhesion effects of: (a) the copper surface treatments, (b) the UV radiation of a laminated resist, and (c) the baking of a resist laminated coupon were measured. Adhesive tape with rectangular or wedge‐shaped openings was placed between the photoresist and copper surfaces with the adhesive side facing the resist. The openings in the tape allowed for contact between the copper surface and the resist, and the opening dimensions determined the width and length of contact. With the aid of the adhesive tape, a better grip of the resist was obtained during the peeling. The results of this study led to the following conclusions: A tin‐silane (SNS) treated copper surface with a peeling strength of 4–7 lbs/in. was the most effective surface treatment. A UV radiation dose below or equal to 32 mJ/cm2 produces an adhesion of the resist with micro‐etched copper of 38±03 lbs/in; above this dose, adhesion increases. Thermal baking improves adhesion; the calculated activation energy of a micro‐etched copper surface with the resist is 65 kcal/mole.
TL;DR: In this paper, a new method, Scanned Beam Laminography (SBL), is used to take 3D X-ray slices of solder joints, enabling thorough inspection of each joint.
Abstract: Solder quality is a critical issue in circuit board production. However, the manufacturing process of today has few built‐in controls to ensure good solder quality. Instead, attention is only paid when a defect is found. The solution lies in the integration of inspection, test and process control. Now a new method, Scanned‐Beam Laminography, takes 3‐dimensional X‐ray slices of solder joints, enabling thorough inspection of each joint. Special software algorithms measure and report the solder joint conditions, creating a system which provides real‐time process control.
TL;DR: The Palexpo Exhibition and Conference Centre close to Geneva Airport was the location for this timely event organised by the EIPC and sponsored by Du Pont Electronics as mentioned in this paper. Participants, including speakers, chairpersons and press, totalled approximately 190.
Abstract: The Palexpo Exhibition and Conference Centre close to Geneva Airport was the location for this timely event organised by the EIPC and sponsored by Du Pont Electronics. Participants, including speakers, chairpersons and press, totalled approximately 190—perhaps a slightly lower figure than anticipated for this first European symposium on an issue of considerable significance for the industry.
TL;DR: In contrast to other types of laser processing in which material is removed by localised heating, excimer laser processing involves a non-thermal ablative material removal mechanism.
Abstract: Excimer lasers are finding increasing use in the electronics manufacturing industry. In contrast to other types of laser processing in which material is removed by localised heating, excimer laser processing involves a non‐thermal ablative material removal mechanism. This is due to the ultra‐violet output and short pulse duration of these unique light sources. The result is a high precision means of patterning thin dielectric films, removing such films from metal substrates, or removing thin metal films from underlying dielectrics. Through proper selection of operating parameters it is possible to achieve smooth sidewall profiles with selectable amount of taper while leaving the surrounding and, in the case of film removal, the underlying material virtually untouched. This paper will review the growing use of excimer lasers in applications such as the skiving of access holes and windows in flexible wiring, the drilling of via holes for multilayer boards, the stripping of microwires and other chip bonding applications. The differences between excimer laser processing and conventional laser based techniques will be highlighted.
TL;DR: In this paper, the authors present a statistically-based, four-phase strategy aimed at better organizing and facilitating the characterisation of a manufacturing process and provide analytical insight into a new statistical methodology aimed at establishing coupon-to-board correlation.
Abstract: This paper addresses two fundamental issues with regard to the production of printed circuit boards (PCBs). First, the paper presents a statistically‐based, four‐phase strategy aimed at better organising and facilitating the characterisation of a manufacturing process. The fact that the case study addresses copper plating thickness of PCBs is secondary to the characterisation strategy. In this sense, the strategy is universal by nature. Second, the paper provides analytical insight into a new statistical methodology aimed at establishing coupon‐to‐board correlation. The general concepts surrounding these two issues are embodied within the given PCB case study. Essentially, the case analysis systematically progresses through all four phases of the parameter characterisation strategy, highlighting the key aspects of each phase. In addition, the aforementioned technique for assessing coupon‐to‐board correlation is given substantiative discussion. However, it should be pointed out that a thorough narration pertaining to many of the statistical and engineering details of the case analysis has been deliberately omitted for the sake of brevity and reading ease. As a result of such considerations, it is assumed that the reader has a working knowledge of descriptive and inferential statistics, as well as experiment design. The benefit of this approach is simple—focus is easily given to the analytical strategy and order of execution without the usual clouding imposed by mathematical explanations.
TL;DR: The use of copper-clad Invar as a substrate material for military applications is generally accepted and welcomed because of their availability, reliability and relative ease of assembly as discussed by the authors, however, polyimide has superior physical properties that make it more suited to SMT and should not be discarded without fully understanding the penalties that may occur with alternative polymers.
Abstract: For military applications the use of LCCCs is generally accepted and welcomed because of their availability, reliability and relative ease of assembly. Moreover, the problems of TCE mismatch, substrate flatness and thermal management have been overcome by the use of copper‐clad Invar as a substrate material. The cost and availability of such substrates lead to a continuing search for more suitable materials or refinements in the present‐day manufacturing processes. The emergence of the new epoxy based laminates such as BT and High Temperature is encouraging designers to move away from the more expensive‐to‐make polyimide materials. However, polyimide has superior physical properties that make it more suited to SMT and should not be discarded without fully understanding the penalties that may occur with alternative polymers. The further development of VHSIC and gallium arsenide integrated circuits means that future substrates will not only have to provide solutions to present problems but will also need to accommodate the increase in signal speeds, control of impedance and other properties. Thus substrate design will see a move towards finer line widths, low‐loss dielectric material, stripline construction and special copper foils.
TL;DR: In this article, the authors evaluated the peel adhesion of an epoxy filleting compound and Parylene C conformal coating to plasma treated, solder mask coated substrates and the apparent contact angle of water on the treated surfaces.
Abstract: Peel adhesion of an epoxy filleting compound and Parylene C conformal coating to plasma treated, solder mask coated substrates and the apparent contact angle of water on the treated surfaces were evaluated. No significant improvement was achieved in the case of the epoxy filleting adhesive for most solder mask coatings studied. On the other hand, Parylene C peel adhesion significantly increased after substrates were treated with air plasma and reached the level of Silane coupling agent primed substrates. This was in contrast to the decrease in Parylene adhesion to argon plasma treated substrates in comparison with the non‐treated substrates. This was related to the oxygen functionalities created on the surfaces by the air plasma versus the ablative nature of the argon plasma. No clear correlation was found between peel strength and the water contact angle in the case of the epoxy adhesive, while for the Parylene conformal coating peel strength achieved its maximum value at the middle of the contact angle range which resulted from the pretreatments applied in this study. It is concluded that air plasma is a very efficient solder mask pretreatment for Parylene conformal coating that can replace Silane primer. Also, if a calibration curve is established for each solder mask‐adhesive and solder mask‐coating system, the apparent water contact angle can serve as a convenient quality control tool for printed circuit finishing processes.
TL;DR: In this article, the authors describe how changes in the quality of copper plate can be monitored with a hot rupture mechanical test method, which is used to detect and evaluate harmful effects such as fissuring before the electroplated copper is used in a PWMLB assembly.
Abstract: Multilayer printed wiring boards make use of electrodeposited copper from two sources. Copper for conductor traces comes from foil manufacturers through thin laminate suppliers. Copper plating for layer interconnection is performed in an in‐house PTH process. Each source makes use of plating chemicals that are obtained from industry suppliers, but production requirements inherent in foil manufacture or in PTH processing can cause variations that occasionally result in copper deposits that exhibit poor hot strength. In a PWMLB, this can result in corner cracks, barrel cracks and inner layer cracks because some of the copper deposits will be susceptible to fissuring under thermal stress conditions. The phenomenon of hot fissuring is caused by the presence of co‐deposited impurities that degrade the hot strength of the deposit due to easy grain boundary separation at elevated temperatures. Stresses imposed by a solder float test, by soldering or by thermal cycling are then sufficient to cause microcracking in a copper plate that is in this condition. In this paper, the author describes how changes in the quality of copper plate can be monitored with a hot rupture mechanical test method. By testing plated copper samples before board fabrication, it is possible to detect and evaluate harmful effects such as fissuring before the electroplated copper is used in a PWMLB assembly.
TL;DR: In this article, the feasibility of replacing the weak assembly step with ultrasonics was investigated and the results showed that with certain preferred directions of ultrasonic weld, weld preload and weld time bond strengths obtained compare very favourably with those achieved with the present surface mount technology reflow process.
Abstract: The potentially highly automated process of surface mounting electronic components directly onto a substrate or printed circuit board possesses a very weak link. Component movement subsequent to placement and before or during solder reflow leads to defect conditions such as tombstoning or rotational misalignment. This work investigates the feasibility of replacing this ‘weak’ assembly step(s) with ultrasonics. The selection and modification of suitable ultrasonic equipment is described as in the bonding of chip components onto PCBs. Reliability analysis of the resultant bonds along with bond quality in terms of shear strength and appearance under scanning electron microscope and optical microscope is studied. The results show that, with certain preferred directions of ultrasonic weld, weld preload and weld time bond strengths obtained compare very favourably with those achieved with the present surface mount technology reflow process, hence establishing the feasibility of ultrasonics for this application.
TL;DR: In this paper, the first use of Mo30Cu foils, a material produced by powder metallurgy consisting of 70% molybdenum and 30% copper, was reported.
Abstract: The thermal management of printed circuit boards with high component density is increasingly becoming an important factor in the efficiency and reliability of electronic systems. A well‐proven technique, which has been used to produce multilayer circuit boards in quantity for several years, is to incorporate metal foils. The metal foils significantly improve heat removal and impart to the circuit board a thermal expansion behaviour closely matching that of the ceramic chip carrier. Roll‐clad Copper‐Invar‐copper (CIC) and copper‐molybdenum‐copper (CMC) foils have been used for this purpose. This paper reports on the first use of Mo30Cu foils, a material produced by powder metallurgy consisting of 70% molybdenum and 30% copper. Contraves AG manufacture SMT multilayer circuit boards incorporating Mo30Cu foils produced by Metallwerk Plansee GmbH. With regard to machinability and physical characteristics, Mo30Cu foils are superior to roll‐clad foils. First of all, the high elastic modulus of Mo30Cu foils is worth mentioning. It positively influences thermal stability and mechanical stiffness of the circuit board.
TL;DR: In this paper, the authors discuss the new technology of centrifugal cleaning where ACCEL Energy™ is harnessed inside an enclosed chamber to provide significant cleaning benefits, such as superior washing, effective rinsing, superior drying, reduced solvent consumption by orders of magnitude, small footprint, and compatibility with H2O, saponifiers, chlorocarbons, fluorocars and terpenes.
Abstract: Cleaning or defluxing of populated printed circuit boards has become a very difficult problem as component stand‐off clearances have become smaller, line spacings tighter, and solvents limited because of the CFC/ozone issue. This paper discusses the new technology of Centrifugal cleaning where ACCEL Energy™ is harnessed inside an enclosed chamber to provide significant cleaning benefits. Among these benefits are: superior washing, effective rinsing, superior drying, reduced solvent consumption by orders of magnitude, small footprint, and compatibility with H2O, saponifiers, chlorocarbons, fluorocarbons and terpenes.
TL;DR: In this article, the possible causes of inner layer junction cracks on multilayer PCBs are discussed and the problems that cracks can cause under rework conditions, along with guidelines on the possible ways to eliminate the cracking problem and on testing procedures to ensure a reliable product.
Abstract: The possible causes of inner layer junction cracks on multilayer PCBs are discussed and the problems that cracks can cause under rework conditions. The procedure to identify the cracks and their exact location within and around the electroless copper junction is shown, along with guidelines on the possible ways to eliminate the cracking problem and on testing procedures to ensure a reliable product.
TL;DR: For those arriving in Paris the weekend before Pronic, what could almost be described as a holiday atmosphere prevailed. as mentioned in this paper The visit by the Prince and Princess of Wales had left its mark in the proliferation of front-page features of ‘Lady Di’ displayed on news stands.
Abstract: For those arriving in Paris the weekend before Pronic, what could almost be described as a holiday atmosphere prevailed. The visit by the Prince and Princess of Wales had left its mark in the proliferation of front‐page features of ‘Lady Di’ displayed on news stands. The Champs Elysees looked elegant and resplendent with a profusion of French tricolours marking the royal visit combined with commemoration of Armistice Day. Autumn sunshine—and green leaves still on the trees—brought throngs of Parisians onto the streets. At present the Arc de Triomphe is closed to the public for cleaning and restoration, but on 11 November there was the unique opportunity, taken by lengthy queues of people, to visit the Tomb of the Unknown Warrior and view the floral wreaths laid there during the commemorative ceremony.