Microwave Hybrid Heating As An Alternative Method For Soldering - A Brief Review

The paper reviews the Microwave Hybrid Heating (MHH) method as well as the effect of MHH towards the interfacial reaction and the shear strength at the solder/Cu joint. Previously, reflow soldering process was performed to solder electronic component. Due to its high defect rate, processing time and energy consumption, MHH method are getting more attention among electronics manufacturers to perform industrial process as it is beneficial in modern microtechnology. MHH method has faster heating rate, improve heating uniformity, reduces the chance of thermal runaway, reduce processing temperature, and reduce hazards to human and environment. This approach has proven to yield scallop-like and angular trapezoid structure of Cu6Sn5 and Cu3Sn in the intermetallic compound (IMC). The IMC thickness shows a competitive result (5.337μm and 5.717μm) compared to reflow soldering. However, not many studies were done on the shear strength of the solder joint

Size, Temperature, and Strain-Rate Dependence on Tensile Mechanical Behaviors of Ni 3

This study focuses on exploring the mechanical properties and nonlinear stress-strain behaviors of monoclinic Ni3Sn4 single crystals under uniaxial tensile test and also their size, temperature, and strain-rate dependence through constant temperature molecular dynamics (MD) simulation using Berendsen thermostat. The deformation evolution of the Ni3Sn4 atomic nanostructure during the tensile test is observed. In addition, the tensile yield strains of various Ni3Sn4 single crystals at different strain rates and temperatures are characterized through unloading process. At last, by way of linear regression analysis, the corresponding normal elastic stiffness constants are approximated and then compared with the literature theoretical data. The radial distribution function analysis shows that Ni3Sn4 single crystal in a one-dimensional nanowire configuration would become a highly disordered structure after thermal equilibration, thereby possessing amorphous-like mechanical behaviors and properties. The initial elastic deformation of Ni3Sn4 single crystal is governed by the reconfiguration of surface atoms, and its deformation evolution after further uniaxial tensile straining is characterized by Ni=Sn bond straightening, bond breakage, inner atomic distortion, cross-section shrinking, and rupture. The calculated normal elastic constants of Ni3Sn4 single crystal are found to be consistent with the literature theoretical data

Simulation of Thermomechanical Stress on Potted Electronic Assemblies

107 s., 16 s. příl. :obr., tab., grafy +CD ROMDiplomová práce pojednává o výzkumu termomechanického namáhání SMD kapacitoru na desce plošných spojů vložené do obálky a zalité zalévací hmotou. Ke zkoumání napětí a přetvoření byla použita metoda konečných prvků a pro zpracování celé simulace byl použit program ANSYS. V první kapitole je popsáno celé zařízení, princip jeho poruchy vlivem termomechanického namáhání, materiálové parametry jednotlivých částí a měření neznámých materiálových parametrů. Následující kapitoly popisují MKP, podmínky simulace v ANSYSu a okrajové podmínky. Předposlední kapitola pojednává o teplotní analýze a rozdílech mezi přechodovým a ustáleným stavem teplotní analýzy. Poslední kapitola se věnuje vyhodnocení výsledků ustálené strukturální analýzy. Je zde popsán vliv tvrdosti zalévací hmoty na vnitřní napětí a přetvoření. Další téma této kapitoly je vyhodnocení vlivu umístění rezistoru na desce plošných spojů, vliv výšky vrstvy zalévací hmoty a vliv přítomnosti obálky na vnitřní namáhání. Výsledky simulace jsou zobrazeny především ve formě grafů pro lepší porovnatelnost. Grafické výsledky ve formě obrázků se nacházejí v příloze na přiloženém CD kvůli jejich velikosti

Microstructural and mechanical characteristics of micro-scale intermetallic compounds interconnections

Following the continually increasing demand for high-density interconnection and multilayer packaging for chips, solder bump size has decreased significantly over the years, this has led to some challenges in the reliability of interconnects. This thesis presents research into the resulting effects of miniaturization on the interconnection with Sn-solder, especially focusing on the full intermetallics (IMCs) micro-joints which appear in the 3D IC stacking packaging. Thereby, systematic studies have been conducted to study the microstructural evolution and reliability issues of Cu-Sn and Cu-Sn-Ni IMCs micro-joints. (1) Phenomenon of IMCs planar growth: The planar IMCs interlayer was asymmetric and composed of (Cu,Ni)6Sn5 mainly in Ni/Sn (2.5~5 µm)/Cu interconnect. Meanwhile, it was symmetric two-layer structure in Cu/Sn (2.5~5 µm)/Cu interconnect with the Cu3Sn fine grains underneath Cu6Sn5 cobblestone-shape-like grains for each IMCs layer. Besides, it is worth noticing that the appearance of Cu-rich whiskers (the mixture of Cu/Cu2O/SnOx/Cu6Sn5) could potentially lead to short-circuit in the cases of ultra-fine (<10 µm pitch) interconnects for the miniaturization of electronics devices. (2) Microstructural evolution process of Cu-Sn IMCs micro-joint: The simultaneous solidification of IMCs interlayer supressed the scalloped growth of Cu6Sn5 grains in Cu/Sn (2.5 µm)/Cu interconnect during the transient liquid phase (TLP) soldering process. The growth factor of Cu3Sn was in the range of 0.29~0.48 in Cu-Cu6Sn5 diffusion couple at 240~290 °C, which was impacted significantly by the type of substrates. And the subsequent homogenization process of Cu3Sn grains was found to be consistent with the description of flux-driven ripening (FDR) theory. Moreover, Kirkendall voids appeared only in the Cu3Sn layer adjacent to Cu-plated substrate, and this porous Cu3Sn micro-joint was mechanically robust during the shear test. (3) Microstructural evolution of Cu-Sn-Ni IMCs micro-joint: There was obvious inter-reaction between the interfacial reactions in Ni/Sn (1.5 µm)/Cu interconnect. The growth factor of (Cu,Ni)3Sn on Cu side was about 0.36 at 240 °C, and the reaction product on Ni side was changed from Ni3Sn4 into (Cu,Ni)6Sn5 with the increase of soldering temperature. In particular, the segregation of Ni atoms occurred along with phase transformation at 290 °C and thereby stabilized the (Cu,Ni)6Sn5 phase for the high Ni content of 20 at.%. (4) Micro-mechanical characteristics of Cu-Sn-Ni IMCs micro-joint: The Young s modulus and hardness of Cu-Sn-Ni IMCs were measured by nanoindentation test, such as 160.6±3.1 GPa/ 7.34±0.14 GPa for (Cu,Ni)6Sn5 and 183.7±4.0 GPa/ 7.38±0.46 GPa for (Cu,Ni)3Sn, respectively. Besides, in-situ nano-compression tests have been conducted on IMCs micro-cantilevers, the fracture strength turns out to be 2.46 GPa. And also, the ultimate tensile stress was calculated to be 2.3±0.7 GPa from in-situ micro-bending tests, which is not sensitive with the microstructural change of IMCs after dwelling at 290 °C