Brandon Gore, Richard Mellitz, Jeff Loyer, Martyn Gaudion, Jean Burnikell and Paul Carre
The aim of this paper is to demonstrate that root impulse energy (RIE) testing is a practical and robust “go/no go” test technique for PCB material losses that can be deployed on…
Abstract
Purpose
The aim of this paper is to demonstrate that root impulse energy (RIE) testing is a practical and robust “go/no go” test technique for PCB material losses that can be deployed on the PCB production floor.
Design/methodology/approach
The study used the RIE method, employing time domain reflectometry techniques on industry standard impedance test coupons modified to include short reference lines and longer test lines. Practical considerations for the use of the methodology on the production floor, such as coupon design, probe layout and environmental conditions were investigated.
Findings
RIE with a 250 ps reflected risetime appears suitable for discerning significant differences in material loss properties provided proper coupon design is incorporated into the panel design and frequencies of interest are limited to a limit commensurate with high reliability and repeatability.
Research limitations/implications
The RIE test proposed does not replace conventional impedance control techniques that are currently in use. However, a suitable standard for loss and cross test equipment calibration is key and will need to be established before this new measurement technique can gain widespread trust throughout the industry.
Originality/value
The paper shows RIE testing is a practical and achievable test method; it is easily deployed and offers repeatable, reliable discrimination between PCBs fabricated with a range of varying base material loss characteristics.
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L.J. Turbini, J. Schodorf, J. Jachim, L. Lach, R. Mellitz and F. Sledd
Today's emphasis on alternative flux technology as an approach to eliminate the use of chlorofluorocarbons (CFCs) requires an understanding of the corrosion potential of the new…
Abstract
Today's emphasis on alternative flux technology as an approach to eliminate the use of chlorofluorocarbons (CFCs) requires an understanding of the corrosion potential of the new fluxes. In 1989, Dr David Bono proposed that monitoring the effect of different soldering fluxes on the rate of corrosion of a copper wire printed on a circuit board would provide quantitative information on the corrosion potential of a flux. Further analysis of this testby Turbini et al. revealed that the degradation mechanism associated with Bono's test is the growth of conductive anodic filaments along the glass fibres of the epoxy‐glass boards. The original test method has been revised, and the test coupon redesigned with the goal of developing a standard, quantitative test method to characterise soldering fluxes. This paper will describe the equipment, test coupon and electrical circuitry associated with this proposed test method. Procedures chosen to reduce error sources associated with electrical noise will be reported and explained.
J. Guinet, X. Lambert and D. Bono
The corrosive power of solder pastes is studied by implementing a new method compatible with the common rules of use. The entire methodology is fully described. The results show…
Abstract
The corrosive power of solder pastes is studied by implementing a new method compatible with the common rules of use. The entire methodology is fully described. The results show evidence of corrosion with some solder pastes that have been identified by microscopic and EDX analysis. The corrosion mechanism is ‘mouse bite’ and conductive anodic filaments. A ranking of the different solder pastes tested is given and pass criteria for this new method of evaluation are proposed.
For a number of years electronic manufacturers of printed circuit assemblies have used rosin‐based soldering fluxes. Post‐solder cleaning was accomplished with chlorinated or…
Abstract
For a number of years electronic manufacturers of printed circuit assemblies have used rosin‐based soldering fluxes. Post‐solder cleaning was accomplished with chlorinated or chlorofluorocarbon (CFC) solvents. With the elimination of these solvent options due to their destructive effect on the stratospheric ozone layer, manufacturers are considering alternative cleaners for rosin flux or new flux choices which can be cleaned with water or left uncleaned. Many of the flux formulations are relatively new and their long‐term effect on the performance of products manufactured with them is unknown. Although ionic contamination testers can alert one to the ionic levels remaining on an assembly, there is no direct relationship between the total ionic level and the corrosivity of the soldering flux. Surface insulation resistance testing is used in the industry, but the results are misunderstood by many. This is due to the fact that SIR data represent a complex dependency on a number of factors including (1) the test conditions (temperature, humidity, bias), (2) the area of interactions (often referred to as the number of squares), (3) the separation between lines on the interdigitated comb pattern, (4) the presence or absence of bias voltage during the test and (5) the nature of the substrate. All of these factors have been the driving force to develop a quantitative screening test for soldering flux residues. This test, originally reported by Dr David Bono, is being modified and developed at Georgia Tech to provide a quantitative evaluation of flux residue corrosivity. This work, in collaboration with the work being performed by the French UTE, will result in a new international standard. This paper reports the latest data on this important test development.
Surface insulation, electrochemical migration and various other insulation resistances are terms which are often glibly used, sometimes even incorrectly. This paper categorises…
Abstract
Surface insulation, electrochemical migration and various other insulation resistances are terms which are often glibly used, sometimes even incorrectly. This paper categorises different types of insulation resistance and catalogues about twenty practical applications of insulation resistance measurement, each with its ideal general conditions of measurement (test voltage, bias voltage, bias polarity, test voltage period, test frequency, test duration, temperature, humidity, test pattern type, test pattern dimensions, voltage gradients, tolerances, etc.) This description is independent of any of the nearly forty known, often contradictory, standards, most of which no longer correspond to the practical printed circuit or assembly of today. Also discussed are the different technologies of insulation resistance measurement, starting with the original non‐electronic ‘Megger®’ types through to modern laboratory electrometers and, finally, instrumentation specific to the practical measurement of printed circuit insulation resistances, including static and dynamic types. The importance of automatic statistical analyses is emphasised, especially with production testing as well as qualification procedures. This paper is aimed not only at those wishing to learn what modern insulation resistance testing is all about, but also at experienced persons wanting to marshall their thoughts about the fundamental meanings of insulation testing for different applications and specifications.
The need to use cleaning methods other than traditional CFC‐113 solvent for hi‐rel electronics imposes more rigid cleanliness testing. In the past, this was mainly limited to…
Abstract
The need to use cleaning methods other than traditional CFC‐113 solvent for hi‐rel electronics imposes more rigid cleanliness testing. In the past, this was mainly limited to ionic contamination control, but this is probably insufficient by itself when using other methods. This paper discusses the various methods for which instrumentation is available, from the practical standpoint. This should satisfy all the requirements of both procurement agencies and manufacturers. Particular emphasis is placed on the fact that most existing standards are out‐of‐date and should be urgently revised. It is suggested that the standards be based on statistically valid test results rather than the simpler, but risky, go/no‐go methods. These probability limit levels should be modulated according to the use to which the circuitry will be put and the technology used in its manufacture. Above all, emphasis is placed on testing methods that are more scientifically based with less empirical guesswork.
Chong Wang, Yingjie Wang, Kegu Adi, Yunzhong Huang, Yuanming Chen, Shouxu Wang, Wei He, Yao Tang, Yukai Sun, Weihua Zhang, Chenggang Xu and Xuemei He
The purpose of this paper is to establish an accurate model to quantify the effect of conductor roughness on insertion loss (IL) and provide improved measurements and suggestions…
Abstract
Purpose
The purpose of this paper is to establish an accurate model to quantify the effect of conductor roughness on insertion loss (IL) and provide improved measurements and suggestions for manufacturing good conductive copper lines of printed circuit board.
Design/methodology/approach
To practically investigates the modified model of conductor roughness, three different kinds of alternate oxidation treatments were used to provide transmission lines with different roughness. The IL results were measured by a vector net analyzer for comparisons with the modified model results.
Findings
An accurate model, with only a 1.8% deviation on average from the measured values, is established. Compared with other models, the modified model is more reliable in industrial manufacturing.
Originality/value
This paper introduces the influence of tiny roughness structures on IL. Besides, this paper discusses the effect of current distribution on IL.
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The paper aims to examine some of the requirements for an industrial strength loss measurement technique in FR4 laminate printed circuit boards and, in particular, to take a…
Abstract
Purpose
The paper aims to examine some of the requirements for an industrial strength loss measurement technique in FR4 laminate printed circuit boards and, in particular, to take a closer look at one new candidate method.
Design/methodology/approach
The paper highlights some of the issues in transferring an essentially laboratory‐based measurement technique to high volume manufacturing, i.e. the shop floor. The paper uses the newly proposed SET2DIL method of characterizing loss, comparing results with established laboratory methods and discusses the practical issues, such as the design of new test probes and coupons, in its implementation.
Findings
The paper shows that current time‐consuming laboratory methods of loss measurement using vector network analysers (VNAs), with their associated high skill requirements, though accurate and reproducible, are not viable for the factory floor, with its challenging environment and, occasionally, lack of specialized expertise. The SET2DIL method of loss measurement appears to offer a robust and reliable method of measuring and predicting loss in FR4 and should achieve wide approval across the board manufacturing industry.
Originality/value
The results of extensive testing are compared favourably with the results of established reference methods using VNAs, showing good correlation, and the SET2DIL method is recommended as being suitable for use in a high volume production environment.
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The 1980s and 1990s have seen the development of new andinteresting soldering flux formulations. Many of these fluxes exhibit improved solderingperformance or are favoured because…
Abstract
The 1980s and 1990s have seen the development of new and interesting soldering flux formulations. Many of these fluxes exhibit improved soldering performance or are favoured because of their reduced environmental impact. In order to further the understanding of these new fluxes and their interaction with the metallisation on the printed wiring board, as well as the substrate itself, one needs to examine test methods carefully and begin to correlate the data among the existing test methods. At Georgia Tech a variety of data have been collected on a number of fluxes including water soluble, low solids and activated rosin fluxes. Test methods for flux characterisation include surface insulation resistance testing, corrosion test measurements and recently impedance spectroscopy at low frequencies. This paper will review the variety of fluxes available, report on results of testing these fluxes using the techniques mentioned above and will define the important information related to soldering flux interactions which each test method uncovers.
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Legal standards that allow teens to make health care decisions, or any important decisions, must account for the contingency and variability of minors’ capacity. Traditional law…
Abstract
Legal standards that allow teens to make health care decisions, or any important decisions, must account for the contingency and variability of minors’ capacity. Traditional law denied minors’ legal authority to make any decisions, giving all power to parents. This rule goes too far; the Supreme Court has held that minors have constitutionally protected autonomy-based rights, and modern views about adolescence are inconsistent with the rule. The question is how and where to draw lines.
Legal standards are based on minors’ evolving maturity, policy favoring decisions that follow medical advice, and policy supporting parental authority. This paper uses four hard cases to show how these considerations factor into legal rules.