Gel encapsulation is gradually replaced by epoxy encapsulation for power modules due to the miniature of epoxy encapsulation. The epoxy and the copper substrate form a dissimilar bond. Generally, the mismatch of the coefficient of thermal expansion (CTE) is thought as the reason for the bond failure. Here, we investigated the influence of copper/epoxy interface interaction on reliability under various reliability tests. It shows that besides the mismatch of CTE, the interfacial interaction also influences greatly. Copper diffuses into epoxy. The diffused copper causes epoxy degradation under high temperatures and humidity, which fails the copper/epoxy bond.
In this paper, a two-step plasma-treated copper-copper direct bonding performed in ambient condition, followed by pressure-less annealing, is reported. A decent shear strength of ~38 MPa is achieved. The hermeticity of the bonded copper dies degrades with prolonged exposure in the ambient. No undesirable materials are observed at the copper-copper bonding interface, which suggests the formation of high-quality bonding. This bonding technology would be applicable for high-throughput 3D heterogeneous integration and advanced packaging.
Vacuum ultraviolet (VUV, λ = 172 nm) excimer radiation can be used to hydrophilize polymer surfaces and remove contaminants. This method allows for the formation of stronger interactions, which improve the adhesion between the treated surface and a coating without reliance on the conventional anchor effect. Herein, the surface modification of cyclo olefin polymer films using VUV light was explored, and the effect of this treatment on the adhesion strength was evaluated. Under suitable conditions, the adhesion strength between electroless-deposited copper and the cyclo olefin polymer substrate can be significantly improved by VUV pre-treatment. Furthermore, we investigated the adhesion mechanism of electroless plating on surface reformed resin by VUV irradiation using a scanning transmission electron microscope.
growing interconnect technology scales by variety, topology, counts, mandate improved and efficient techniques for their handling. Table based formats proved most robust for this function regardless of the exact geometrical pattern involved. The methodology outlined can support description of any desired geometrical pattern, as well as secondary properties of the interconnects. The secondary properties can be also processed for derived functionality such as interconnect mirroring or associated metal grids.
Single circle diameter bump wafer is generally used. Recently, 2 circle diameter (2CD) wafer is on the rise. 2CD wafer is a kind of wafer which has two different size vias. In the conventional 2CD wafer, solder layer such as SnAg alloy is electroplated on Cu bump. However, it has become difficult to adjust the bump height. Because the size of the via has become smaller and the density has increased. These changes result in the difference in the thickness on the small and large diameters. Thus, SnAg alloy is plated again on the small vias to adjust the bump height in the reflow process. Considering these circumstances, it is desired that the bump thickness of small vias is thicker than large vias. In order to breakthrough this problem, we made height difference by increasing Cu thickness of small vias only with one Cu electroplating step.
In this research, the interfacial reactions between solid silver and solid indium are discussed. The samples are fabricated by electroplating indium on silver substrates and then underwent aging at 80, 100 and 120℃. After aging, two intermetallic compounds (IMCs) layers, Ag2In and AgIn2, were found at the interface of silver and indium. Both I MCs grow with time during the aging process. The growth rate of Ag2In and AgIn2 increases with temperature and follows parabolic law, implying that the growth of Ag2In and AgIn2 are both diffusion-controlled reactions.
The demand for power modules is increasing year by year due to increases in the number of electric vehicles, renewable energy plants etc. The new generation of power modules are made of SiC, GaN and Ga 2 O 3 because of their wide band-gap. These semiconductors can be used under higher temperature than Si, and packaging materials like molding resin, die-attaching materials etc., that can withstand high temperatures, are being developed in many countries. The material strength of an interface between molding resin and a metallic substrate is one of the most important topics for the reliability of power modules. Thermal cycle testing is a popular method to evaluate the reliability of electronic packaging including power modules, but it requires a long testing time. To reduce the testing times of thermal cycle tests, we need to elucidate the crack extension law of the interface. We performed mechanical fatigue tests, and investigated the crack extension law of the interface under low-cycle fatigue.
The effect of the binder chemical composition on interfacial microstructure and the electrical connection property of the adhesion interface between silver (Ag) micro-flakes filled electrically conductive adhesives (ECAs) and metal electrodes were investigated. The effect of binder chemical composition was also shown on the change in electrical conductive property through post-annealing. Furthermore, the interfacial electrical resistivity after curing and post-annealing and the interfacial microstructure after post-annealing were changed depending on the binder chemical composition. Post-annealed specimens showed progressive sintering of silver micro fillers in the cured resin binder and inter-diffusion of silver and copper at the adhesive interface. These results will be one of the essential keys to the material design of ECAs having favorable interfacial properties.
Transient liquid phase bonding is one solution for high temperature die attachment of power modules. The fracture behavior is critical to evaluate the reliability of the bonded joints. In this study, the failure process of an Ag-In sandwich joint with shear strength of 29.7 MPa obtained by transient liquid phase bonding were analyzed during the shear test. Ag 9 In 4 was the only intermetallic compound formed in the joints. Fracture happened inside the Ag 9 In 4 layer in the upper joint and crack propagated along the Ag 9 In 4 grain boundaries. The failure process and the influence of the sandwich structure were also analyzed through finite elemental modelling.
Double-sided <111>-oriented nanotwinned copper foils with 99% highly <111> orientation and low roughness on both surfaces are fabricated for diffusion bonding. We succeed to use them to bond copper substrates and silicon substrates at 300 °C for 30 min with excellent bonding quality and bonding strength. With the high melting point, thermal conductivity, and bonding strength, the Cu foils show great potential for thermal interface materials in high power electronics.
Cu signal transmission line with a flat and smooth substrate/copper interface and high adhesion strength was fabricated on a low-loss type rigid substrate by using newly developed silver-seed plating technique. The microstrip lines by silver-seed method showed better transmission characteristics than that fabricated with commercial CCL of same PPE type substrate. The importance of the surface morphology of conductor line for low signal transmission loss is experimentally confirmed. Silver-seed plating technique, which enables the formation of flat and smooth electric conductors, is expected to be useful for the formation of high-speed transmission wiring on a rigid substrate.
In package use, the feed-in and lead-out points of the power supply are not fixed positions, and some components that require large operating currents require an independent power supply to ensure normal operation, so there may be multiple power supply pins on the circuit board, which means The position of the noise source is also not fixed, so this paper designs a sample with multiple power feed-in points, and reserves a chip placement area in the center of the sample to simulate the chip position of the actual product. This paper will use the commonly used system circuit As a research when the system line changes layers, the upper signal line will refer to the ground layer of the second layer and the lower layer signal line will refer to the power layer of the third layer. At this time, the return path will also be due to the gap between the ground layer and the power layer. They are degraded by being non-conductive to each other, which in turn introduces more power supply noise.
This paper examined the effect of triethanolamine (TEA) and related surfactants on the electrical conductivity and reliability of copper-filled electrically conductive pastes. The TEA surfactant effectively enhanced the electrical conductivity but not the electrical reliability in an 85°C/85%RH environment. When the TEA surfactant was used, the co-applying of oleic acid improved electrical reliability. The tris(2-amino ethyl)amine (TREN), which has a molecular structure with amino groups by substituting TEA hydroxyl groups, enhanced electrical conductivity and reliability. Because the surfactants can sensitively control the electrical conductivity and reliability, the molecular design will be critical in developing advanced Cu-filled pastes.
Transport behavior of copper ions in polyelectrolyte phase during electrodeposition has been kinetically analyzed for novel solid electrodeposition (SED) process using polyelectrolyte membranes attached on cathode surface. Both experimental and theoretical study including in situ UV-vis spectroscopy for SED under constant applied voltage demonstrate that the transfer of copper ions can be determined by ion penetration at polyelectrolyte/solution interface, depending on the applied voltage as well as concentration of ions in the electrolyte phase.
We had developed the novel photo imageable film for interlayer insulation application. Small vias up to 8 µm could be formed through photo image process, and electroless copper plating could be applied to form copper wiring. This film was superior to epoxy-based interlayer insulating films in that it was easy to open small-diameter vias and did not require desmear process. It was also superior to liquid photo imageable polyimide in that it was less prone to warpage due to its low curing temperature and CTE, and could be formed by film lamination, ensuring surface flatness in a single process.
Good solder resist (SR) opening uniformity can effectively avoid electrical defect in the connection between the chip and substrate, including device short, open issue and bump crack issue. The main objective of this research is to propose an optimized process control to improve SR uniformity by controlling queue time through DOE test, including the queue time of tear off PET film after exposure, exposure to development queue time and development chemical renew time. Among them, queue time of tear off PET film after exposure were selected from 1min. to 20min. The exposure to development queue time was set to 1hr to 4hr. The development chemical renew timing was also set. The best SR opening uniformity was revealed by tolerance of opening size, which can be reduced from ±5um to ±3um when queue time of tear off PET film after exposure were set to ≤1min of tear off PET after exposure. The DOE test result sheds light in improving the performance between chip and IC substrate.
The adhesion of small scale conductive trace patterning is critical to the quality and reliability of advanced electronic packaging. The current study is part of an iNEMI project to define a testing standard for trace features 20μm and below. This paper demonstrates designs and initial application of peel and shear testing on small traces and shows that the strength of fine circuitry patterns does not scale linearly with size. Further analysis on shear test parameters shows how the measurement setup can impact the final results.
With growing interest in millimeter-wave (mmWave, 30 GHz – 300 GHz) technologies, researchers and manufacturers need standard reference materials and best practices for measurement validation, material acceptance, and quality assurance. Today, there is no standard reference material for dielectric permittivity and loss tangent in the mmWave regime. Here, we show the results of round robin experiments that evaluate the current state-of-the-art methods in dielectric measurements. Due to the wide spread in these results, we identify the need for a standard reference material at mmWave.
