Advanced soldering processes (original) (raw)

Room temperature soldering of microelectronic components for enhanced thermal performance

EuroSimE 2005. Proceedings of the 6th International Conference on Thermal, Mechanial and Multi-Physics Simulation and Experiments in Micro-Electronics and Micro-Systems, 2005., 2005

A novel fluxless soldering process is presented, that enables lead-free soldering of semiconductor die-to-heat spreader (and heat spreader-to-heat sink structures) a t room temperature. The process is based on the use of reactive multilayer foils to locally melt the solder interface. Silicon-copper samples joined with indium solder are thermally characterized for a range of die sizes and bond line thicknesses. The thermal resistance of the solder joints is found to be an order of magnitude lower than for conventional thermal interface materials (TIMs), with good thermal fatigue resistance. The predicted thermo-mechanical behavior of the solder interface in a central processing unit (CPU) application indicates that such joints would survive application environments without causing die cracking. The soldering technology employed could greatly enhance the thermal performance of power IC packages such as CPUs, by enabling the adoption of a solder-based TIM between the die and integrated heat spreader.

Soldering & Surface Mount Technology

Abstract Purpose – This study aims to synthesize polyethylene glycol (PEG)-rosin derivatives from rosin and PEG for the production of solid soldering fluxes. The PEG-rosin derivatives would be water soluble, and the resulting solid soldering fluxes would have reasonable wetting ability when combined with a low-halide-content activator. Design/methodology/approach – This paper presents a synthetic process for PEG-rosin derivatives. The reaction conditions (including catalyst type, catalyst concentration, reaction temperature and PEG type) were optimized for the synthesis of PEG-rosin derivatives. The chemical and physical properties of PEG-rosin derivatives were characterized by Fourier transform infrared spectroscopy, carbon-13 nuclear magnetic resonance spectrometry, differential scanning calorimetry and gel permeation chromatography. The production and characteristics of water-soluble rosin fluxes (WSRFs) were studied according to the standards of the Japanese Industrial Standards (JIS) Committees. Findings – WSRs were successfully synthesized from rosin and PEG using 2 per cent ZnO as a catalyst, with a 2:1 molar ratio of rosin:PEG at 250°C over 9 h. The resulting WSRs were completely soluble in water. As the PEG3000-rosin had the highest melting point (55.2°C), it was chosen for the preparation of the WSRFs. Activators such as succinic acid, glutaric acid, ethylamine hydrochloride and diethylamine hydrobromide were selected for use in the production of the fluxes. It was found that WSRF 09 and WSRF 04 gave the best performance with the lead-free Sn-0.7Cu solder alloy in terms of good solderability, low halide content (less than 1,500 ppm), high insulation resistance and low corrosion. These fluxes were applied to produce solder pastes with Sn-3.0Ag-0.5Cu alloy and they passed the performance tests as expected for solder paste. Research limitations/implications – Further studies are necessary on large-scale production and to compare the performance of these fluxes to those from conventional water-soluble fluxes currently available in the market. Application of these fluxes on low-temperature solder alloys such as SnZn and SnBi (Ren et al., 2016) worth further study. Originality/value – The classification of flux systems according to the JIS 3283 standard does not specify PEG-rosin derivatives in the flux; nevertheless, ranking of the flux systems based on the halide content and corrosion properties of activators would be useful information when selecting flux systems for electronics soldering in water-washable applications. The application of these fluxes in solder paste gave very promising results and is worth investigating into more detail, as well as field test. Keywords Flux, Sn-Ag-Cu, Solder, Solder paste, PEG-rosin, Polyethylene glycol, Rosin, Sn-Cu

Principles of Soldering

ASM International, The Materials Information Society, 2004

Principles of Soldering serves as a problem-solving guide for engineers who work with soldering processes and soldered components and assemblies. It begins with a review of key process parameters, including surface energy and tension, wetting and contact angle, fluid flow, filler spreading characteristics, dissolution of parent materials, and intermetallic growth. It then examines the factors that influence the functional integrity of soldered joints and the practicality of the process employed. It discusses the metallurgy of solder alloy systems, the effect of metallic impurities, and the use of phase diagrams to better understand and control the soldering process. It explains how joining atmospheres influence chemical reactions and how fluxes help remove surface oxides and other films. It describes the benefits of fluxless soldering and the role of materials in defining process constraints. It also covers lead-free solders, bump bonding, amalgams, and diffusion soldering as well as mechanical property testing, joint characterization and modeling techniques, and solderability standards.

Advancement in Soldering Technology Main Issues and Its Perspectives - Part 1

The advancement of electronics and related instrumentation would be possible in mass production of electrical and electronics components/equipments with accomplishment and advances in soldering technology. With the advent of different components like resistors, capacitors, diodes, transistors and especially integrated circuits have changed the electronics world completely. As there is an intensive demand for package miniaturization and the density of surface mount components and other interconnects continues to advance, the technology for solder attachment methods must also improve and continue to evolve. This paper discusses the evolvement of soldering techniques, its applications and the criteria to select proper soldering techniques for specific applications.

Room temperature lead-free soldering of microelectronic components using a local heat source

2004

This paper describes a new joining process that enables fluxless, lead-free soldering of similar and dissimilar materials at room temperature with no thermal damage to surrounding components. The joining process is based on the use of a reactive multilayer foil as a local heat source. The foils are a new class of nano-engineered materials, which consist of thousands of alternating nanoscale layers comprised of elements with large negative heats of mixing. With a small thermal or electrical stimulus, a controlled, self-propagating reaction can be initiated in these foils at room temperature. By inserting a multilayer foil between two solder layers and two components, heat generated by the reaction melts the solder and consequently bonds the components. Since the heat generated is localized to the bonding interface, components are not exposed to high temperature and hence thermal damage is avoided. Materials with dissimilar coefficients of thermal expansion can also be joined, due to the localized heating of the components. This paper focuses on an application where surface mount connectors are joined to printed circuit boards using a eutectic Au-Sn solder alloy. Details on thermal exposure of the components during joining, performance verification testing, and the process advantages are presented.

Selective Solder Fine Pitch Components on High Thermal Mass Assembly

2019

The number of through-hole components on printed circuit boards (PCB) has declined significantly over the last decade. Miniaturization in electronics has resulted in less THT (through-hole technology) and leads with a finer pitch. For this reason, the soldering of these components has also changed from wave soldering to Point-to-point selective soldering. Soldering these small, fine-pitch components is a challenge when surface mount components (SMD) are positioned very close to THT components on the PCB layout. This study, done in cooperation with a large automotive EMS customer, defines the process windows for through-hole technology for fine-pitch components. It determines what is feasible to solder and defines layout design parameter that make soldering possible with SMD areas and other components on the assembly.