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Reviews the traditional use of thermoset (epoxy) adhesives for various bonding applications and highlights some limitations in today’s microelectronics arena. In particular, concerns for thermal and stress management associated with large area silicon bonded to a wide variety of substrate materials has led to an increasing interest in thermoplastic adhesive technology. Thermoplastics are not always the best solution for every application. This paper sets out to address the “pros and cons” of each polymer technology for different microelectronic applications taking into account some of the key physical properties such as Tg, TCE and modulus. In addition, practical issues such as handling, storage and processing are considered in detail.

Today’s emerging markets in the electronic packaging industry require some unique properties in adhesives, especially in die attach applications. In multichip module (MCM) applications, for example, the low temperature reworkability of die bonds is of primary importance, particularly if known good die (KGD) are not employed. If KGD are used in the MCM, a temporary, reworkable die adhesive is also desirable for a KGD testing programme. Large area die on organic substrates, which are key to the more portable, high power computers, require a very compliant adhesive to absorb the high mismatch in expansions. An overview of the present adhesive technologies reveals some serious limitations in their application and performance. Traditional Ag epoxies, primarily because of their irreversible ‘thermosetting’ during cure, do not fulfill all the material requirements. Thermoplastic chemistries are ideal candidates for MCMs because of their reversible melting and resolidification properties. This paper details the development of a novel silver loaded thermoplastic paste that overcomes most of the deficiencies seen in present day adhesives. One of the main obstacles that has hindered the use of thermoplastic pastes as an adhesive has been the slow solvent extraction during the curing step. With current technology, this inherently slow solvent extraction typically requires a complex process of first depositing a flat profile, then removing the solvent with a pre‐drying step, and finally attaching the die by a heat/pressure step. A blend of components, hereafter referred to as DM4030, has been tested and compared against conventional materials in the industry. Functional properties of adhesion, resistivity, wire bonding and others are summarised for various temperature profiles. Long‐term reliability test results are shown for temperature cycling, temperature/humidity (85° C, 85% RH), and high temperature storage. For reworkability applications, die removal force as a function of temperature is also presented.

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.

MANY engineers look upon plastics and allied materials as entirely new to the aircraft industry, but such is not the case. Phenol fibre sheet and resin bonded waterproof plywood have been used for years, and acrylic resin sheet has been in use for transparent enclosures for some time past; yet all come under the above category. The primary difference between the past and present uses of these materials is that they are now used in applications where structural loads are involved, while they were previously used only in non‐stressed parts where special characteristics, such as transparency or insulating qualities, were of paramount importance. If these materials are classified according to their major characteristics they fall into three categories; those made with thermosetting resins, those made with thermoplastic resins, and those made with wood veneer. This classification also in a general way divides them according to their principal uses; thermosetting materials being used mostly in the production of relatively small structural parts, the thermoplastics being used mostly for their transparent properties, and the wood veneer materials being used mostly in relatively large structural parts and assemblies.

Lead frame tape is a crucial support for lead frames in the IC assembly process. The tape residue on the quad flat non-leaded (QFN) could result in low reliability and failure in electrical conductivity tests. The tape residue would affect overall performance of the chips and contribute to low pass yield. The purpose of this paper is to present an in-depth study of tape residue and factors that may affect it.

An experiment using lead frame and tapes from three manufacturers with two types of die bond adhesives, namely, die attach film (DAF) and wafer back coating (WBC), was conducted. Copper (Cu) wire bonding and die bonding performances were measured in terms of process capability, stitch bond strength and die attach strength.

Results showed that no tape residue was observed on the thermoplastic adhesive-based lead frames manufactured by Hitachi after the de-taping process because of the tape’s thermoplastic adhesive properties.

This paper studies the occurrence of tape residue and a viable solution for it through the correct process optimization and combination of semiconductor manufacturing materials. Factors that may affect tape residue have also been studied and further research can be done to explore other options in the future as an alternate solution.

Weld‐bonding combines the physical force‐based process of welding with the chemical force‐based process of bonding or, more properly, adhesive bonding. When done properly, the claim is that a hybrid process results which offers the best of both processes; the high joint efficiency, resistance to diverse and complex loading, and temperature tolerance of welding; the load‐spreading, stress concentration‐softening, and structural damage tolerance of adhesive bonding. And, beyond these individual process attributes, there are claims, or at least predictions, of synergistic benefits in the form of improved energy absorption and fatigue life for demanding applications. However, it is difficult to find reliable data in the open literature to support these real or potential benefits. Furthermore, complications in performing the hybrid process in practice place an even greater premium on process control than normal. This paper explores the question, “Is it all worth it?” The paper delves into the theory underlying weld‐bonding, the facts concerning the process including pluses and pitfalls, and considers where the process could or should go from here.

The Packaging Revolution of the ’90s, powered by the perpetual drive for smaller‐faster‐cheaper products, is placing increasing demands on the electronic materials sector. Down‐sizing, without a cost penalty, requires new materials and processes. Electronic polymers are playing an increasingly vital rôle as area array, chip size components and packageless designs become mainstream technologies. Micro‐Ball Grid Arrays (micro‐BGA), Chip Scale Packages (CSP) and Chip‐on‐Board(COB) require new adhesives and encapsulants that enable the use of low‐cost, high density organic‐based wiring and interconnect structures. Concurrently, new, simplified processes are being developed in order to streamline high volume manufacturing. This paper discusses quick bonding film die attach adhesives, fast‐flow flip‐chip underfills, and a variety of liquid encapsulants as well as new conductive adhesives designed for flip‐chip and micro‐Package assembly. Process innovations include the new Printed Package concept and the appealing simple Polymer Dip Chip method of flip‐chip assembly without paste deposition. The intrinsic versatility and synergy afforded by new and emerging electronic polymers are helping the industry meet the seemingly paradoxical challenge of smaller‐faster‐cheaper.

This review paper aims to provide a better understanding of formulation and processing of anisotropic conductive adhesive film (ACF) material and to summarize the significant research and development work for the mechanical properties of ACF material and joints, which helps to the development and application of ACF joints with better reliability in microelectronic packaging systems.

The ACF material was cured at high temperature of 190°C, and the cured ACF was tested by conducting the tensile experiments with uniaxial and cyclic loads. The ACF joint was obtained with process of pre-bonding and final bonding. The impact tests and shear tests of ACF joints were completed with different aging conditions such as high temperature, thermal cycling and hygrothermal aging.

The cured ACF exhibited unique time-, temperature- and loading rate-dependent behaviors and a strong memory of loading history. Prior stress cycling with higher mean stress or stress amplitude restrained the ratcheting strain in subsequent cycling with lower mean stress or stress amplitude. The impact strength and adhesive strength of ACF joints increased with increase of bonding temperature, but they decreased with increase of environment temperature. The adhesive strength and life of ACF joints decreased with hygrothermal aging, whereas increased firstly and then decreased with thermal cycling.

This study is to review the recent investigations on the mechanical properties of ACF material and joints in microelectronic packaging applications.

Environmental issues have an ever‐increasing influence on the selection of material and processes in electronic manufacturing. This paper discusses the use of conductive adhesives as a replacement for solder on SMT printed circuit boards. As a result of a world‐wide market survey, a number of conductive adhesives have been selected. One of the two key issues of this paper has been to uncover the market for adhesive types and their composition. The other key issue has been the technical investigation of the influence of component termination and printed circuit surface types on adhesive bonding stability. Four different types of adhesives on two different metal surfaces are compared with conventional solder technology. Each adhesive has been applied to the PCBs by either screen printing or dispensing according to the manufacturer's recommendation, followed by curing. All PCBs went through thermal and humidity cycling followed by electrical measurements of resistance. Finally, all variants have been adhesion tested. All adhesive variants have been microsectioned for metallurgical and microstructure examination. Energy dispersive analysis of X‐ray (EDAX) of the metal particles in the adhesive has been carried out and documented. Rework of conductive joints is briefly commented on. Finally, aspects of occupational health are discussed concerning work with adhesive types. Work with epoxy based adhesives has been brouaht into special focus.