Effect of the reflow process on IMC growth for different devices and complex components

Abstract

Intermetallic compound (IMC), as an inevitable part between pad and solder, has a severe effect on the strength and reliability of microelectronic interconnection. Here, an investigation was carried out on IMC growth for different devices and complex components. The device-level experiments were conducted with five factors: peak temperature, time duration above solder liquidus temperature, the thickness of solder paste, surface finish types, and package types including BGA and QFP. Meanwhile, four complex components with the same reflow profile were conducted and compared for component-level experiments. A scanning electron microscopy was used to measure the thickness and determine the spatial distribution of the elements through the intermetallic compound. The multivariate analysis of the formation and growth of IMC during reflow soldering was studied based on Nernst-Shchukarev's equation and the results of the experiments. The difference in IMC thickness between BGA and QFP with different factors was discussed and compared separately. The results showed that the peak temperature and time above liquidus played a vital role in the IMC growth and the solder paste thickness and different pad metallization could not be ignored. SEM pictures of the solder and statistical results were revealed that the surface finish type has a marked impact on the formation of the IMC. For PCB with numbers of components, the IMC thickness and uniformity of solder joints at corner and center positions showed some regularity differences. Meanwhile, the bump shape (Cu1-xNix)6Sn5 IMC was observed for small size BGA with ENIG during the reflow process. The results have a significant meaning to optimize its reflow process parameters for complex components, to improve the interconnection reliability in engineering.

Delamination of Plasticized Devices in Dynamic Service Environments

“…The non-airtightness of the plastic seal causes the intrusion of a large number of nonpolar molecules and polar molecules along the micropores, including O2, which can undergo oxidation reactions, and H2O, which can undergo corrosion reactions [44,45. One of the well-established mechanisms in the research field is the oxidation of the copper substrate in the plasticized copper substrate or the RDL (ReDistribution Layer) in the presence of O2 and water molecules carrying Na + , Cl − , and other impurity ions through the chip passivation layer, and the metal-layer corrosion reaction [13][14][15][16][17][18][46][47][48], as shown in In 1972, Sharpe proposed the interphase concept to describe the transition regi the interface between two phases of different materials [50]. At the EMC/Cu inte when the oxide thickness of the Cu substrate is in the range of 20-30 nm, the increa surface roughness leads to the enhancement of the binding at the two-phase inte In 1972, Sharpe proposed the interphase concept to describe the transition region at the interface between two phases of different materials [50].…”

“…Researchers’ studies on delamination mechanisms have mainly focused on thermal stress damage and moisture damage. Explaining the delamination phenomenon from the stress–strain perspective alone, it has been found that, at the delamination interface, mainly due to the interface between the two phases of the material, the plastic deformation of the two-phase material is formed under the action of the alternating shear stress, which ultimately leads to the failure of delamination [ 8 , 9 , 10 , 11 , 12 , 13 , 14 ]. At the same time, under the intrusion of moisture, ionic contaminants corrode the chip, and moisture thermal expansion is also the main reason for the device to appear to suffer from the “popcorn” effect [ 15 , 16 , 17 , 18 , 19 ].…”

“…Chemical Damage by MoistureThe non-airtightness of the plastic seal causes the intrusion of a large number of non-polar molecules and polar molecules along the micropores, including O 2 , which can undergo oxidation reactions, and H 2 O, which can undergo corrosion reactions[44,45]. One of the well-established mechanisms in the research field is the oxidation of the copper substrate in the plasticized copper substrate or the RDL (ReDistribution Layer) in the presence of O 2 and water molecules carrying Na + , Cl − , and other impurity ions through the chip passivation layer, and the metal-layer corrosion reaction[13][14][15][16][17][18][46][47][48], as shown in Figure4. However, the effect of thermal oxidation of epoxy resin in the presence of O 2 and H 2 O on its adhesion is less mentioned.Micromachines 2024, 15, x FOR PEER REVIEW 8…”