Reliability of wire-bonding and solder joint for high temperature operation of power semiconductor device

Transactions of The Japan Institute of Electronics Packaging

Yagi

et al. 2009

Three types of inexpensive Pb-free solder joints, namely Zn-based and Bi-based solders, and a CuSn alloy were studied for application to the high-temperature operation of wide band-gap power semiconductor devices using GaN or SiC. ZnAl solder sheets, whose melting point is 380°C were prepared, and then surface oxides were removed by RF plasma etching. Subsequently, Cu thin films were deposited by the DC sputtering method on the solder sheet. After that, joint samples were fabricated using a conventional electrical furnace with H 2 /N 2 gas flow. That the joints were sufficiently dense was confirmed by scanning acoustic microscope. The wettability of the solder was improved due to contact between the pure Zn-Al solder without oxide and the Ni surface of the substrate, and the chemical reaction between the Zn-Al solder and the deposited Cu thin film. Bi with CuAlMn particle solders, whose melting point is 270°C, were fabricated and it was found that the solder has almost double the tensile strength of pure Bi. Excellent wettability was observed with the Ni or Pd thin film deposited on the Cu substrate. It was found that deposited Ni or Pd was not observed in the interface between the substrates after the joint samples were fabricated. CuSn alloy joints were fabricated using Sn thin films deposited and annealed on Cu substrates. The temperature during the annealing was kept at approximately 350°C; therefore, only the Sn film was melted and some chemical reaction occurred between the liquid Sn and solid Cu.Then, Cu 3 Sn alloy, whose melting point is 640°C, appeared in the joint and the composition was confirmed by X-ray diffraction analysis. Furthermore, it was found that the CuSn alloy is harder than Cu as measured by nano indentation analysis. In addition, the joints showed excellent thermal cycle reliability.Finally, the properties of these joints are summarized.

Section: Zn-base Solder Jointmentioning

confidence: 99%

Pb-Free High Temperature Solder Joints for Power Semiconductor Devices

Yamada

Transactions of The Japan Institute of Electronics Packaging

Yagi

et al. 2009

“…Since the details of Bi-based solder properties such as phase relation, microstructure, interfacial reaction, and reliability have already been reported, [19][20][21] only the typical microstructures of an egg-type core/shell and an in situ composite powder particles are shown, in Fig. 5a and b, respectively.…”

Section: Powder Of Pb-free Soldersmentioning

confidence: 99%

Microstructural Evolution of Alloy Powder for Electronic Materials with Liquid Miscibility Gap

Ohnuma

Saegusa

et al. 2008

Journal of Elec Materi

Self Cite

The microstructure of powders that are applicable for electronic materials were studied for some systems in which there is a liquid miscibility gap. The characteristic morphologies of an egg-like core type and a uniform secondphase dispersion are shown in relation to the phase diagram, where thermodynamic calculations are a powerful tool for alloy design and the prediction of microstructure. Typical examples of microstructural evolution and properties of Pb-free solders and Ag-based micropowders with high electrical conductivity produced by a gas-atomizing method are presented.

“…2,3 Moreover, a power module structure using Zn-Albased solder that shows excellent reliability even after thermal cycling test between -40°C and 200°C has been proposed. 4,5 In a previous study, the soldered interface between a Cu substrate and Zn-4Al(-1Cu) alloy (m.p. 380°C) was investigated with a focus on the formation and growth of some intermetallic compounds (IMCs) such as b (A2: disordered bcc) or b¢ (B2: ordered bcc), c (D8 2 : Cu 5 Zn 8 ), and e (A3: disordered hcp).…”

Section: Introductionmentioning

confidence: 99%

Interfacial Reaction between Zn-Al-Based High-Temperature Solders and Ni Substrate

Makino

Watanabe

et al. 2008

Journal of Elec Materi

The Zn-Al(-Cu) eutectic alloys (melting point 381°C) are candidates for use as Pb-free high-temperature solders as a substitute for Pb-based solders, which are suitable for severe working environments such as the engine room of hybrid vehicles equipped with an inverter system as well as a heat engine. In this study, the interfacial reaction between Zn-Al(-Cu) alloys and the Ni substrate during soldering, aging, and thermal cycling was investigated. Semiconductor chips and Ni substrates were soldered with Zn-Al(-Cu) alloys at various temperatures under a nitrogen atmosphere. The soldered assemblies were then heat-treated at 200°C and 300°C to examine the microstructural evolution at the soldered interface. The effect of severe thermal cycles between -40°C and 250°C in air on the microstructure and fracture behavior at the solder joint was investigated. Even after a 1000-cycle test, the thickness of the Al 3 Ni 2 layer formed at the interface between the Zn-Al-based solder and the Ni substrate, which is responsible for the damage of the soldered assemblies, was quite small.