Solder Fillers Research Articles

Mechanical Bonding Properties of Solderable Anisotropic Polymer Composite containing Low-Melting-Point and High-Melting-Point Solder Fillers

In this papers, to enhance the mechanical bonding properties of solderable anisotropic polymer composites (SAPCs) containing low-melting-point solder filler only, a new low-melting-point solder and high-melting-point solder mixed filler filled SAPCs (LH-SAPCs) was proposed, and the influence of the high-melting-point solder filler on the conduction path formation and mechanical bonding properties of the LH-SAPC were investigated. Two types of LH-SAPC were synthesized by adding high-melting-point solder within the low-melting-point solder/high-melting-point solder mixed filler at mixing ratios of 0 and 50 vol% (the volume fraction of low-melting-point solder/high-melting-point solder mixed filler in the polymer composite was 20%), and a bonding test was conducted using QFP. The results exhibited that the LH-SAPC containing high-melting-point solder formed a wide and stable conduction path due to the proper selective conduction path formation behavior by the interaction between molten low-melting-point solder and solid-state high-melting-point solder fillers within the polymer composite with low viscosity condition. Furthermore, the mechanical bonding properties of the LH-SAPC joints containing high-melting-point solder were enhanced compared to that of LH-SAPC containing low-melting-point solder only owing to the precipitation hardening and dispersion strengthening effects due to the increase of fine Bi-rich, Cu<sub>6</sub>Sn<sub>5</sub>, and Ag<sub>3</sub>Sn intermetallic compound particles inside the conduction path.

An analytical review on interfacial reactions in high-temperature die-attach: The insights into the effect of surface metallization and filler materials

This review aims for a comprehensive insight into the interfacial reactions and the effects of surface metallization in high temperature die-attach, which is critical in governing the reliability of resultant interconnects of power electronic modules. With the emerging high-temperature filler materials, the interfacial interactions and microstructural evolutions exhibit various distinctive features, which demands detailed examination in order to identify suitable surface finishes. The metallization is not always beneficial to improving the quality and reliability of the interconnects, and consideration should also be given to the cost-effectiveness and manufacturability. The intermetallic compounds (IMCs) formed during interfacial reactions are of prime concerns for an extended discussion, together with the formation of solid solution at interfaces which can also be an important topic to explore. In this work, five commonly-encountered high temperature solder fillers are examined, including high-Pb, Au-based, Bi-Ag, Zn-Al solders and nano Ag paste, the emphasises are put on the interactions with different metallized surfaces in die-attach. The effects of metallization on interfacial reactions and formation of interfaces are discussed. Finally, the recommendations of suitable metallization are outlined to enable cost-effective and reliable interconnects for the related applications.

Mechanisms for the formation of conduction paths in a solderable epoxy composite with a mixed low- and high-melting-point solder filler

Mechanisms for the formation of conduction paths in a solderable epoxy composite with a mixed low- and high-melting-point solder filler

Bonding mechanism of ultrasonically soldered silica glasses using tin-titanium solder filler

In this work, the ultrasonic assisted active metal soldering of silica glasses was successfully achieved using Sn-2Ti solder filler at a low soldering temperature of 250 °C in ambient atmosphere. A nano-crystalline layer of R-TiO2 with an average thickness of 7.6 nm formed at the interface between silica glasses and Sn-2Ti solder filler, which verified that a sono-oxidation reaction has occurred during the ultrasonic assisted active metal soldering process. The soldered butt joints exhibited an average tensile strength of 25.3 MPa.

Adsorption and interface reaction in direct active bonding of GaAs to GaAs using Sn–Ag–Ti solder filler

Adsorption and interface reaction in direct active bonding of GaAs to GaAs using Sn–Ag–Ti solder filler

Effect of Characteristic of Resin on Coalescence Behavior of Solder Fillers in Self-Organization Assembly Method

Effect of Characteristic of Resin on Coalescence Behavior of Solder Fillers in Self-Organization Assembly Method

Evolution of the microstructure of Sn–Ag–Cu solder joints exposed to ultrasonic waves during solidification

Cu/SAC405/Cu solder joints were fabricated using a modified reflow-soldering procedure. The samples were first maintained at 260°C for 320s, following the conventional reflow-soldering methodology. The reflow process was then interrupted and the samples were exposed to ultrasonic waves (USW) while they were cooling in air. Compared with a sample reflow-soldered conventionally, the solidification of the Sn–Ag0.04–Cu0.005 (SAC405) solder filler metal alloy under the influence of USW resulted in significant changes to the microstructure of the solder joints. The thickness of the Cu6Sn5 intermetallic layer at the Cu/SAC interface of the USW-solidified soldered joint decreased by as much as 76%. The β-Sn dendrite width was also reduced by as much as 67%, and the SAC matrix was filled with bundles of acicular Cu6Sn5 crystals. The formation of Ag3Sn plates was also prevented, and the size of the rod-like SAC ternary eutectic matrix was reduced from 700nm to 50nm. This behaviour is attributed to the effect of cavitation and liquid metal streaming induced by the USW on nucleation and the whole solidification process. The presence of Cu6Sn5 bundles and the refined eutectic and β-Sn dendrites in the matrix led to an average improvement in the hardness of the solder bulk by 45%.

Movement of solder fillers because of the unevenness of interfacial tension in self-organization assembly process

Soldering or anisotropic conductive adhesives (ACAs) are used for assembling of devices with high-density area-array terminals. However, solder bump processes are high-cost and interconnects of ACAs are less-reliable. The purpose of this study is to develop a novel method. Self-organization assembly method that uses active resin containing solder fillers may allow reliable interconnects at low-cost. Fundamental process of Self-organization assembly are movement, coalescence, and wetting of molten fillers in resin. The focus of this paper is on the movement of fillers. In-situ observations of coalescence behavior for 40μmϕ molten fillers in the resin revealed irregular movement of the fillers at a velocity of several μm/s. Numerical analysis, using improved volume fraction method, indicated that a 10% degradation of interfacial energy on one side of a 40μmϕ filler could move the filler at a velocity of several mm/s. This degradation of the interfacial energy was resulted the remaining oxide film.

Solder Filler Motion Driven by Interfacial Tension in Self-Organization Assembly Process

Soldering and anisotropic conductive adhesives (ACAs) are widely used for assembling electronic devices with narrow-pitch terminals. Solder bump methods need a number of processes, while interconnects of ACAs are less reliable. The purpose of this study is to develop a novel assembling method. The Self-organization assembly method using active resin containing solder fillers may allow reliable interconnects by simple process. The focus of this paper is on the movement of fillers, one of the fundamental processes of the Self-organization assembly method. In-situ observations on the behavior of 40 µmφ molten fillers in the resin revealed irregular movement of the fillers at a velocity of several µm/s. Numerical analysis, using improved volume of fluid method, indicated that even 10% difference of interfacial energy between half sides of a 40 µmφ filler could move the filler at the velocity of several mm/s. The inhomogeneous distribution of the interfacial energy is thought to be caused by the remaining surfactant elements.

Numerical Analysis of Self-Organizing Interconnection Process by 3 Dimensional Flow Dynamics

The growing importance of high integration on electronics demands novel interconnection methods replacing high-cost solder bumping or less reliable conductive adhesives. Self-organizing interconnection process using resin containing solder fillers has a possibility to achieve high-density joints satisfying both needs. Numerical study visualized the process and revealed that surface tension of molten fillers and resin viscosity determine the speed of conductive path formation.

Effect of solder filler thickness on the mechanical stability of fiber-solder-ferrule joint under temperature cyclic loading

The base materials of package and ferrule are often gold-coated Kovar and Invar, they both have relatively low coefficient of thermal expansion (CTE). Solder 63Sn37Pb dissolves Au substantially and forms brittle AuSn4, which may cause catastrophic failure in the fiber-solder-ferrule (FSF) joint in the long-term application. It is well known that thermal fatigue creep is one of the crucial factors affecting the life and reliability of a solder joint in electronic and optoelectronic assemblies. Therefore, it is important to understand the behavior of the FSF joint under thermal cyclic loading. In this study, four different thicknesses of solder filler in a FSF joint were examined. By using the finite element method (FEM), the equivalent creep strains of eutectic lead-tin solder were compared. The joints were subjected to 5 cycles of temperature cycling test, i.e., −65 to 150∘C. It was found that the thicker solder filler is subjected to a larger equivalent creep strain than the thinner solder filler. It is discussed the vertical shift of the optical fiber, which is sensitive to temperature and has effects on the power loss coupling. Modeling and experimental results show that 0.5 mm is the best inner diameter of ferrule that provides the lowest displacement and, thus, the lowest power loss under temperature cycle.

Modeling joining materials for microelectronics packaging

Modeling of solder-substrate interactions together with careful experimental work can provide a good basis for developing new materials such as conductive adhesives and Pb-free solders as well as fluxless soldering processes for microelectronics packaging. The modeling of the solder-substrate interactions will in effect lead to a rationalization of the trial and error methods commonly employed and hence minimize the number of experiments required. It provides useful information on the chemical reactions, stabilities of various microstructures and growth rates of reaction products during joining or in use of electronic devices. This is of particular importance in the case of small solder volumes, since the compositions and microstructures of solder alloys can be entirely altered by the solder-substrate reactions during the joining. As specific examples the solder-substrate reactions have been investigated in the Sn-Bi/Cu and Sn-Bi-Zn/Cu systems with and without adhesives. The solder-substrate-environment interactions under high purity reducing gases have been studied also with the meniscograph. The reduction of surface oxides, formation and the stability of the intermetallic layers, Cu/sub 3/Sn and Cu/sub 6/Sn/sub 5/, and the growth of brittle Bi layer in the microjoints due to the change of the composition of the solder filler was studied both theoretically and experimentally. Moreover, an explanation concerning the strong dewetting effect of zinc-containing solders found experimentally is given. An emphasis was placed also on the solder-substrate-environment interaction by studying the effect of humidity on chemical stability of microjoints in an epoxy-based adhesive.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>