In Part 1, background information on mechanical properties and metallurgy of solder alloys and soldered joints has been presented. In Part 2, mechanisms of damage and degradation…
Abstract
In Part 1, background information on mechanical properties and metallurgy of solder alloys and soldered joints has been presented. In Part 2, mechanisms of damage and degradation of components and soldered joints during soldering, transport and field life have been discussed, the most important mechanism being low cycle fatigue of the solder metal. In this third part, the determination of the fatigue life expectancy of soldered joints is discussed. Accelerated testing of fatigue is needed, as the possibilities of calculations are strongly limited. A temperature cycle test under specified conditions is proposed as a standard. A model is worked out for the determination of the acceleration factor of this test. A compilation of a number of solder fatigue test results, generated in the author's company, is presented.
In Part 1, background information on mechanical properties and metallurgy of solder alloys and soldered joints has been presented. In this part, mechanisms of damage and…
Abstract
In Part 1, background information on mechanical properties and metallurgy of solder alloys and soldered joints has been presented. In this part, mechanisms of damage and degradation of components and soldered joints during soldering, during transport, and during field life are discussed. Thermal shock damage of components and excessive dissolution of metallisations are the major effects during soldering. During transport, fatigue of leads and fracture may be caused by vibration and mechanical shocks respectively. During field life, degradation is governed primarily by low cycle fatigue of the solder and incidentally also by formation of intermetallic diffusion layers between solder and base metals. This article contains an extended illustration of solder fatigue of joints on a variety of component and board types. Finally, the influence of the variety of soldered constructions in electronic circuits on solder fatigue is discussed.
Damage to components during soldering and degradation of soldered joints is determined to a large extent by the mechanical properties and the metallurgy of solder alloys and…
Abstract
Damage to components during soldering and degradation of soldered joints is determined to a large extent by the mechanical properties and the metallurgy of solder alloys and soldered joints. Knowledge of these properties is required for understanding of the mechanisms of damage and degradation. A compilation of this background knowledge is presented in this first article. It comprises the elastic, strength, creep and fatigue characteristics of tin/lead solders. Further, the metallurgy of tin/lead solders and soldered joints is discussed in terms of solidification structures, formation of intermetallic compounds, ageing of structures and effects of different solderable metallisations and soldering technology.
E.E. de Kluizenaar and M.M.F. Verguld
Strength measurements of soldered joints in electronics are widely used for the assessment of joint quality. However, a variety of experiments, reported in this article, clearly…
Abstract
Strength measurements of soldered joints in electronics are widely used for the assessment of joint quality. However, a variety of experiments, reported in this article, clearly show that a strong relationship between initial strength and joint quality does not exist. Far more important for joint reliability is the resistance of soldered constructions to low‐cycle fatigue of the solder metal, caused by thermal expansion differences upon temperature cycling during use. A temperature cycling test is proposed as a standard accelerated ageing method for the prediction of the low‐cycle fatigue life of soldered joints in electronics.
Colin Lea, E.E. de Kluizenaar and W. Rubin
‘Fluxing and Cleaning in Electronics Soldering’ The Grosvenor Hotel, London, 22 February 1989. ‘To clean or not to clean?’ ‘Aqueous or solvent cleaning?’ ‘What is the future for…
Abstract
‘Fluxing and Cleaning in Electronics Soldering’ The Grosvenor Hotel, London, 22 February 1989. ‘To clean or not to clean?’ ‘Aqueous or solvent cleaning?’ ‘What is the future for CFCs and other chlorinated solvents?’ The electronics assembly industry is ringing with such questions that make the cleaning of electronic assemblies the key issue for 1989—an issue that urgently requires answers that have the stamp of authority based on fact rather than speculation. This BABS seminar was therefore very timely and attracted a large audience to listen to eight presentations from speakers representing the cleaning equipment manufacturers, flux manufacturers, MoD quality assurance, and users' experience, as well as background on solvents in the environment.
Ultrasonic cleaning is an effective aid in the removal of flux residues from surface mounted circuits. However, an over‐intensive and too extended ultrasonic load of…
Abstract
Ultrasonic cleaning is an effective aid in the removal of flux residues from surface mounted circuits. However, an over‐intensive and too extended ultrasonic load of surface‐mounted electronic circuits, on ceramic substrates, occasionally causes the fracture of component leads. In a metallurgical study, it was found that the fracture mechanism is fatigue. The fundamental cure for this problem is to limit the ultrasonic load to a level below the fatigue limit of the leads. This can be achieved by limiting the ultrasonic power input in the bath. Other beneficial measures are to limit the cleaning time and the ultrasonic frequency, and to prevent the components from coming into contact with other parts during cleaning.
Tape automated bonding (TAB) is a powerful technique for connecting fine‐pitch integrated components to the corresponding substrates. This paper describes the specific example of…
Abstract
Tape automated bonding (TAB) is a powerful technique for connecting fine‐pitch integrated components to the corresponding substrates. This paper describes the specific example of hot‐bar soldering TAB components with an outer lead bonding (OLB) pitch of 0.150 mm to FR‐4 printed wiring boards. The prerequisites to be taken into account, the outer lead bonding process parameters, the hot‐bar soldering results and recommendations are presented.
R.J. Klein Wassink and J.A.H. van Gerven
During reflow soldering the applied solder paste is melted and the components, previously placed on the solder paste, move into their final position. This process, however, may be…
Abstract
During reflow soldering the applied solder paste is melted and the components, previously placed on the solder paste, move into their final position. This process, however, may be accompanied by various unwanted movements of components and solder. Components may move horizontally along the surface of the board (this is called swimming or floating), or may move vertically and stand on their ends (this is called drawbridging or Manhattan effect). On the other hand, the molten solder may move to places other than those intended, e.g., into metallised holes (PTH) connected to the solder lands, or upwards along component leads away from the joint area; this effect is called solder wicking. Moreover, isolated small solder balls are often found on the board surface after melting of the paste. Experiments show that all these effects depend on the heating method, vapour phase soldering often being the most prone. The driving forces of the displacements can be explained in terms of forces and pressure caused by the surface tension of the molten solder, whereas the observed influences of the heating method are the result of the direction from which the heat is transported to the solder paste to be melted. From this, important conclusions for vapour phase soldering, infra‐red soldering and hot‐belt soldering may be drawn.
Toshihiro Miyake, Masaru Ishida and Satoshi Inagaki
The purpose of this paper is to develop a new ionic compound free soldering process.
Abstract
Purpose
The purpose of this paper is to develop a new ionic compound free soldering process.
Design/methodology/approach
The ability of hydrocarbons including 9,10‐dihydroanthracene, eicosane, 2,6,10,14‐tetramethylpentadecane, cyclooctane, and dicyclopentadiene to reduce cuprous or cupric oxide was investigated. The applicability of hydrocarbons as ion free flux reagents was experimentally examined. The hydrocarbons were applied to the soldering of pre‐oxidized copper electrodes under practical conditions.
Findings
A 9,10‐dihydroanthracene was found to be efficient at reducing cuprous or cupric oxide powder under an argon atmosphere at 300°C for 2 min. The high‐reducing ability of the hydrocarbon is in agreement with the low‐homolytical C−H bond dissociation energy calculated based on the density functional theory. A 9,10‐dihydroanthracene was shown, by the highest soldering efficiency and sufficient reliability in the environmental testing, to be applicable as an ion‐free soldering flux.
Originality/value
The findings of this paper suggest a new method for an ionic compound free soldering process.
T. Kwikkers, J. Lantaires, R.B. Turnbull, H.T. Law, Barry George and Dave Savage
On 20 April ISHM‐Benelux held its 1988 Spring meeting at the Grand Hotel Heerlen. This meeting was totally devoted to implantable devices, in particular to the technologies used…
Abstract
On 20 April ISHM‐Benelux held its 1988 Spring meeting at the Grand Hotel Heerlen. This meeting was totally devoted to implantable devices, in particular to the technologies used for these high reliability, extremely demanding devices. For this meeting ISHM‐Benelux was the guest of the Kerkrade facility of Medtronic. Medtronic (headquartered in Minneapolis, USA) is the world's leading manufacturer of implantable electronic devices. Apart from the assembly of pacemakers and heart‐wires, the Kerkrade facility acts as a manufacturing technology centre for Medtronic's European facilities.