Eiichi Ide

Study of Bonding Technology Using Silver Nanoparticles

We investigated a new bonding technique utilizing nano-scaled particles for use in high-temperature environments. The results of our investigations revealed that the method could be used to form bonds by simultaneously applying heat and pressure. Moreover, compared to a conventional Pb–5Sn-solder bond, a nanoparticle-based bond suffered no degradation in bonding strength over an elevated-temperature holding period of 1000 h at 250 °C, and its discharge characteristics were improved (i.e., increased) threefold. It is possible to extend this bonding technique to mounting components in devices that operate in high-temperature environments, e.g., it can be used to mount components such as silicon carbide (SiC) devices, which are expected to be applied in environments with temperatures exceeding 250 °C.

Joint strength and interfacial microstructure between Sn–Ag–Cu and Sn–Zn–Bi solders and Cu substrate

Abstract In the present research, in order to fundamentally investigate the strength and interfacial microstructure of the joints between Sn–3.5Ag–0.7Cu (SAC) and Sn–8Zn–3Bi (SZB) solders and Cu, examinations using the standardized solder joint specimen for measuring the shear strength were performed. The effects of the addition of Ag, Bi and Pb to the solders, which are the ingredients of possible lead plating materials of quad plat package, solder layer thickness and aging treatments ranging from 358 to 423 K were investigated. The SAC base solder joints, whose strength hardly degraded after aging, were more reliable than the SZB base solder joints. Since no detrimental effect of the Bi or Pb addition was recognized, the lead plating materials are found to have no significant effect on the strength of the SAC solder joints. Although the SZB base solder joints had higher strength than the SAC base solder joints in as-soldered condition, a significant degradation of the joint strength occurred after aging. In the case of thinner solder layer of 20 μm, the Cu6Sn5 layer that formed at both the solder/Cu5Zn8 and Cu5Zn8/Cu interfaces after aging caused the fracture of the solder joints and resulted in the degradation of the joint strength. In the case of thicker solder layer of 100 μm, the Cu5Zn8 interfacial layer continuously grew during aging, which caused the fracture of the solder joints and resulted in the decrease in the joint strength. As for the effect of the addition elements, while Pb addition caused a marked degradation of the joint strength, Ag addition and Bi addition had no detrimental effect on the strength of the solder joints. In particular, the joint with the Ag addition solder had the better strength in the case of thinner solder layer. Thus, as for lead plating for the SZB solder, Sn–Pb should be avoided and Sn–Bi or Sn–Ag as Pb-free plating has no detrimental effect on the joint strength. In particular, Sn–Ag plating is preferable in the viewpoint of the joint strength.

A novel metal-to-metal bonding process through in-situ formation of Ag nanoparticles using Ag2O microparticles

The metal-to-metal bonding has been successfully achieved via the bonding process using Ag metallo-organic nanoparticles at a bonding temperature of around 300-, which can be alternative to the current microsoldering in electronics assembly using high-temperature solders. However, further reduction of bonding temperature and/or bonding pressure is needed. In the present research, a novel bonding process through in-situ formation of Ag nanoparticles instead of the filler material of the Ag metallo-organic nanoparticles has been developed. The Ag nanoparticles can form by the reduction of Ag2O particles. In this study, the Ag2O particles were mixed with triethylene glycol as a reducing agent to form a paste for bonding. The Au coated cylindrical specimens were bonded using the paste. The Ag nanoparticles formed at around 130 to 160 through the reduction process of Ag2O particles with triethylene glycol. The Ag nanoparticles were immediately sintered each other due to a great surface energy per volume. A transmission electron microscope observation revealed that the sintered Ag metallurgically bonded to the Au substrate at around 160 and a dense Ag layer formed after further heating. The tensile strength of the joint bonded at 250 under a bonding pressure of 5MPa was around 60MPa

Low-Temperature Bonding Using Silver Nanoparticles Stabilized by Short-Chain Alkylamines

In this paper, we report on low temperature bonding using silver nanoparticles stabilized by short-chain alkylamines with different numbers carbon between 8 to 12. The bonding can be achieved by simultaneous heating and pressurization. The shear strength increased as the decomposition temperature of the stabilizer decreased. In the case of silver nanoparticles stabilized with n-octylamine (having the lowest decomposition temperature among the three stabilizers), the shear strength was 24 MPa for bonding at 400 °C. The difference in the shear strength is probably related to the amount of residual organic material in the sintering layer; the residual organic material would hinder the sintering of the silver nanoparticles, which was suggested by thermogravimetric analysis (TGA) results.

Bonding of Various Metals Using Ag Metallo-Organic Nanoparticles-A Novel Bonding Process Using Ag Metallo-Organic Nanoparticles-

We propose a novel bonding process using Ag metallo-organic nanoparticles, of which the average particle size is around 11 nm. In this paper, Al, Ti, Ni, Cu, Ag and Au disc joints were made using the Ag metallo-organic nanoparticles in order to investigate the bondability of the various metals. These joints are evaluated based on measurement of the shear strength, and the observation of the fracture surfaces and the cross-sectional microstructures. The shear strength of the various metal joints increased in the following order: Al, Ti, Ni, Cu, Ag and Au. This corresponds to the order of the standard-free energy value of the oxide formation for each metal. In particular, while the strengths of the Cu, Ag and Au joints, in which the oxides can be reduced by carbon, were the same level, those of the Al and Ti joints, of which the oxides were more stable than carbon oxides, were extremely low. This result suggests that the carbon atoms or organic elements generated by the decomposition of the organic shell of the Ag metallo-organic nanoparticles may play a role in deoxidizing the oxide film on the metal surface. This can promote chemical bonding between the Ag nanoparticles and metals at low temperatures.

Effects of Solvents in the Polyethylene Glycol Serieson the Bonding of Copper Joints Using Ag2O Paste

The effects of reducing solvents on the bonding process using silver oxide paste in a copper joint were investigated. Three solvent types were tested: diethylene glycol (DEG), triethylene glycol (TEG), and polyethylene glycol (PEG). The strength of the joints was assessed by fracturing, which occurred at the interface of the copper oxide layer and the copper substrate in DEG and TEG samples and at the bonded interface in the PEG sample. Analysis of the samples revealed that, in the DEG and TEG samples, the copper substrate was oxidized during the bonding process, which compromised the shear strength of the joints. In contrast, the PEG sample exhibited nonuniform sintering of the silver layer while retaining good shear strength. It was found that the combination of DEG and PEG produced optimum shear strength in the copper joint, as PEG suppressed the growth of copper oxide and DEG promoted the formation of a dense sintered silver layer. The bonding strength achieved was higher than that of the gold-to-gold joint made using standard Pb-5Sn solder.

Low Temperature Sintering Bonding Process Using Ag Nanoparticles Derived from Ag2O for Packaging of High-Temperature Electronics

A novel bonding process using Ag2O paste composed of Ag2O particles and a reducing agent has been proposed as a Pb-free alternative of high melting point solders in electronics packaging. Ag2O paste formed Ag nanoparticles through the redox reaction in the bonding process and in-situ formed Ag nanoparticles sintered immediately. While the bonding process using Ag metallo-organic nanoparticles, which have been proposed, was unfavorable to the bonding at 250 degree Celsius or lower in terms of requiring removal of stable organic shells, the bonding process using Ag2O paste demonstrated the possibility of further low-temperature bonding.

The Sintering Process of Ag Metallo-Organic Nanoparticles and the Influence of the Joining Parameters Upon Cu-to-Cu Joining

We propose a novel bonding process using Ag metallo-organic nanoparticles as a new application of nanotechnologies. The average size of the Ag nanoparticle is approximately 11 nm, and each nanoparticle is covered with an organic shell. Usually, the agglomeration of metallic nanoparticles is unavoidable due to its large surface energy. However, on the account of the organic shell, these Ag nanoparticles exist individually, and once the organic shell has been removed, these Ag nanoparticles turn activated and abruptly agglomerate. We analyzed its thermal characteristics, applied the agglomerating of the nanoparticles to Cu-to-Cu joining, and researched the influence of the bonding condition, such as bonding pressure, temperature or holding time, upon the joint strengths. The joint strengths using the nanoparticles were 30–40 MPa, which is strong enough to be applied as a solder. In addition, it came to the conclusion that the strengths increased in accord with the aforesaid three parameters.Copyright

The Bondabilities of Various Metals Using Ag Metallo-Organic Nanoparticles and These Bonding Mechanisms

A novel bonding process using Ag metallo-organic nanoparticles has been proposed. This process is applicable to the alternative to the current high temperature solders, such as Pb-10Sn or Pb-20Sn. In this paper, Al, Ti, Ni, Cu, Ag and Au disc joints were made using the Ag metallo-organic nanoparticles in order to investigate the bondability of the various metals. These joints were evaluated based on the measurement of the shear strength, and the observation of the fracture surfaces and the cross-sectional microstructures. The shear strength of various metal joints increased in the following order: Al, Ti, Ni, Cu, Ag and Au joints. This corresponds to the order of the standard free energy value of the oxide formation for each metal. This result suggests that the carbon atoms generated by the decomposition of the organic shell of the Ag metallo-organic nanoparticles may play a role in deoxidizing the oxide film on the metal surface.Copyright