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11 – 20 of over 3000Looks at the adhesive‐bonding process, arguing that quality control is generally lacking. Presents a “bonding chain” and goes on to apply quality assurance tools to the adhesive…
Abstract
Looks at the adhesive‐bonding process, arguing that quality control is generally lacking. Presents a “bonding chain” and goes on to apply quality assurance tools to the adhesive‐bonding process using three case studies to illustrate.
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V. Jankauskaite and R. Barkauskas
Discusses the use of piperylene‐styrene copolymer (PSC) for polychloroprene adhesive modification. States that PSC significantly improves modified adhesive properties ‐ bond…
Abstract
Discusses the use of piperylene‐styrene copolymer (PSC) for polychloroprene adhesive modification. States that PSC significantly improves modified adhesive properties ‐ bond strength, viscosity, high heat resistance, good adhesion to a variety of substrates, compatibility with other adhesive additives. Looks at the advantage of using more environmentally friendly technology for thermoplastic rubber bonding with PSC modified polychloroprene adhesives. Concludes that the new adhesive product can be used for specific combinations of materials and application methods, making it possible to produce cheaper and better products.
The electronics assembly industry has fortunately rediscovered conductive adhesives as the search for lead‐free joining materials and improved performance intensifies. Although…
Abstract
The electronics assembly industry has fortunately rediscovered conductive adhesives as the search for lead‐free joining materials and improved performance intensifies. Although these intrinsically clean bonding agents are often first sought for their favourable environmental attributes, many are surprised to find that conductive adhesives can solve old and new problems. Today, new polymer solders for SMT allow low temperature processing, finer pitch assembly and wider processing latitude while providing compatibility with a very much larger range of materials than solder. State‐of‐the‐art adhesives are oxide‐tolerant and absolutely no fluxing or cleaning is required. Adhesives work where solder cannot be used. What's more, polymer‐based solder alternatives can run on existing SMT lines — no new equipment is needed. Z‐axis, or anisotropic, bonding agents are uni‐directional conductive materials that solve fine pitch interconnect problems in several areas. The anisotropics now dominate the flat panel interconnect field. Nearly every LCD and other flat panel display is connected with a polymer adhesive. The Z‐axis adhesives are also beginning to enable high density multilayer circuits and MCMs to be built more effectively. Finally, Z‐axis appears to offer the simplest and most cost‐effective means for flip chip bonding. However, special equipment is required. The paper compares the metallurgical solder joint, the present de facto standard, with the polymer composite bond to highlight similarities and important differences. All types of conductive adhesives are discussed including the latest — Area Array Z‐axis types. Bonding materials, assembly processes and performance are also covered.
Robert W. Messler, Scot Bohnenstiehl, John Levene, Erika Johnson and Luo Chen
Being inherently a non‐pressure fusion process, laser‐beam welding (LBW) has been shown to have difficulty compared to resistance spot welding for weld‐bonding Al alloy…
Abstract
Being inherently a non‐pressure fusion process, laser‐beam welding (LBW) has been shown to have difficulty compared to resistance spot welding for weld‐bonding Al alloy structures, despite the many structural and manufacturing productivity advantages. Study of laser‐beam weld‐bonding of Al‐alloy structure for automobile assembly has led to a technique that appears to have both technical feasibility and production utility. The use of LBW through a hole in a pressure‐applying probe has proven to allow the production of contamination‐free spot welds through pre‐applied pre‐cured structural adhesive. The general approach, along with some details to still be overcome, is presented for both information and solution.
Andrea Spaggiari and Filippo Favali
The purpose of this paper is to evaluate and exploit the combination of additive manufacturing polymeric technology and structural adhesives. The main advantage is to expand the…
Abstract
Purpose
The purpose of this paper is to evaluate and exploit the combination of additive manufacturing polymeric technology and structural adhesives. The main advantage is to expand the maximum dimension of the 3D printed parts, which is typically limited, by joining the parts with structural adhesive, without losing strength and stiffness and keeping the major asset of polymeric 3 D printing: freedom of shape of the system and low cost of parts.
Design/methodology/approach
The materials used in the paper are the following. The adhesive considered is a commercial inexpensive acrylic, quite similar to superglue, applicable with almost no surface preparation and fast curing, as time constraint is one of the key problems that affects industrial adhesive applications. The 3D printed parts were in acrylonitrile butadiene styrene (ABS), obtained with a Fortus 250mc FDM machine, from Stratasys. The work first compares flat overlap joint with joints designed to permit mechanical interlocking of the adherends and then to a monolithic component with the same geometry. Single lap, joggle lap and double lap joints are the configurations experimentally characterized following a design of experiment approach.
Findings
The results show a failure in the substrate, due to the low strength of the polymeric adherends for the first batch of typical bonded configurations, single lap, joggle lap and double lap. The central bonded area, with an increased global thickness, never does fail, and the adhesive is able to transfer the load both with and without mechanical interlocking. An additional set of scarf joints was also tested to promote adhesive failure as well as to retrieve the adhesive strength in this application. The results shows that bonding of polymeric AM parts is able to express its full potential compared with a monolithic solution even though the joint fails prematurely in the adherend due to the bending stresses and the notches present in the lap joints.
Research limitations/implications
Because of the 3D printed polymeric material adopted, the results may be generalized only when the elastic properties of the adherends and of the adhesive are similar, so it is not possible to extend the findings of the work to metallic additive manufactured components.
Practical implications
The paper shows that the adhesives are feasible way to expand the potentiality of 3 D printed equipment to obtain larger parts with equivalent mechanical properties. The paper also shows that the scarf joint, which fails in the adhesive first, can be used to extract information about the adhesive strength, useful for the designers which have to combine adhesive and additive manufactured polymeric parts.
Originality/value
To the best of the researchers’ knowledge, there are scarce quantitative information in technical literature about the performance of additive manufactured parts in combination with structural adhesives and this work provides an insight on this interesting subject. This manuscript provides a feasible way of using rapid prototyping techniques in combination with adhesive bonding to fully exploit the additive manufacturing capability and to create large and cost-effective 3 D printed parts.
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A Review of the Properties and Applications of High‐Strength Metal‐to‐Metal Joints and Sandwich Constructions Bonded with High‐Strength Adhesives. TODAY'S adhesives are the…
Abstract
A Review of the Properties and Applications of High‐Strength Metal‐to‐Metal Joints and Sandwich Constructions Bonded with High‐Strength Adhesives. TODAY'S adhesives are the complex products of continually expanding technologies. Their applications appear to be limited only by the skill and ingenuity of the designer and his fabricators. Even in a single area such as metal‐to‐metal bonds in aerospace and electronic uses, evaluation and selection of an adhesive requires familiarity with a large number of adhesive systems.
P. Savolainen and J. Kivilahti
Tape automated bonding (TAB) circuits were joined byhot compression bonding to copper or nickel conductors on glass with two anisotropic electricallyconductive adhesives. One of…
Abstract
Tape automated bonding (TAB) circuits were joined by hot compression bonding to copper or nickel conductors on glass with two anisotropic electrically conductive adhesives. One of the adhesives had a thermoplastic polystyrene‐polyester matrix which contained easily deforming metal‐coated polymer particles, while the other was a thermosetting bisphenol (A) based epoxy resin filled with nickel particles. The resistance values and the mechanical strengths of the joints were measured before and after the ageing treatments. The thermoplastic adhesive had the lowest resistance values with copper conductors and the joints produced with this adhesive showed increasing strength values during the ageing tests. The joints between the Ni conductors had smaller values of electrical conductivity irrespective of the adhesive used. The SEM/EPMA technique revealed that particles of the thermoplastic adhesive tended to agglomerate. This may cause problems when components with very fine lead pitch are joined, either by short circuiting or leaving some contacts without particles.
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The purpose of this paper is to investigate the effect of substrate material and thickness on the thermal cycling reliability of flip chip joints assembled with anisotropic…
Abstract
Purpose
The purpose of this paper is to investigate the effect of substrate material and thickness on the thermal cycling reliability of flip chip joints assembled with anisotropic conductive adhesives (ACA).
Design/methodology/approach
Four test lots are assembled using three different substrates. Two of the substrates are made of FR‐4. The thicknesses of these substrates are 600 and 100 μm. The third substrate is made of liquid crystal polymers (LCP) and is flexible. With the thicker FR‐4 substrate two test lots are assembled using both normal and two‐step bonding profiles to study how the bonding profile affects the deformation of the substrate. Four different bonding pressures are used to study the effect of pressure on reliability and the failure mechanism of the ACA joints. The reliability of the test samples is studied using a temperature cycling test.
Findings
The reliability of the test lot with the LCP substrate is considerably better than that of the test lots with the FR‐4 substrates. Additionally, the thinner FR‐4 substrate has better reliability than the thicker FR‐4 substrate. The failure mechanisms found varied among the test lots. The effect of the two‐step bonding process on the deformation of the substrate is found to be minor compared with the effect of the glass fibres.
Originality/value
The work shows that the thermal cycling reliability of ACA flip chip joints is markedly influenced by the thickness and material of the substrate. It is also seen that the substrate used influences the failure mechanisms formed during thermal cycling testing.
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The purpose of this study is to investigate the effect of chip and substrate thickness on the thermal cycling reliability of flip chip joints assembled with anisotropic conductive…
Abstract
Purpose
The purpose of this study is to investigate the effect of chip and substrate thickness on the thermal cycling reliability of flip chip joints assembled with anisotropic conductive adhesives (ACA) on FR‐4 substrates.
Design/methodology/approach
Four test lots were assembled with two substrates and two test chips. The thicknesses of the substrates were 710 and 100 μm and the thicknesses of the chips were 480 and 80 μm. To study the effect of the bonding pressure each test lot contained four test series bonded with four different bonding pressures. The reliability of the test samples was studied using a temperature cycling test.
Findings
The reliability of the test lots varied widely during the test. The test lot with a thin substrate and thin chip demonstrated considerably better reliability than the other test lots. In addition, the test lots had different failure mechanisms. After the test delamination was found in every test lot except the one assembled with the thin chip and the thin substrate.
Originality/value
The work shows that the thermal cycling reliability of ACA flip chip joints can be markedly increased by using thinned chips or reducing the thickness of the substrate.
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R. Aschenbrenner, E. Zakel, G. Azdasht**, A. Kloeser and H. Reichl
During the last few years an increasing number of flip‐chip (FC) interconnection technologies have emerged. While flip‐chip assembly offers many advantages compared with…
Abstract
During the last few years an increasing number of flip‐chip (FC) interconnection technologies have emerged. While flip‐chip assembly offers many advantages compared with conventional packaging techniques, several aspects prevent this technology from entering the high volume market. Among these are the availability of bumped chips and the costs of the substrates, i.e., ceramic substrates with closely matching coefficient of thermal expansion (CTE) to the chip, in order to maintain high reliability. Only recently, with the possibility of filling the gap between chip and organic substrate with an encapsulant, was the reliability of flip‐chips mounted on organic substrates significantly enhanced. This paper presents two approaches to a fluxless process, one based on soldering techniques using Au‐Sn metallurgy and the other on adhesive joining techniques. Soldering is performed with a thermode and with a laser based system. For both of these FC‐joining processes, alternative bump mettallurgies based on electroplated gold, electroplated gold‐tin, mechanical gold and electroless nickel gold bumps are applied.