Electronic Packaging Materials and Their Functions in Thermal Managements

Electrical interconnection, mechanical support and electrical insulation are basic function requirements for printed circuit boards (PCB) in all of electronic products. The current trend toward miniaturization in electronics industry has forced a continuous reduction on conductor spacing. This fact has brought a greater reliability challenge to insulating properties of PCB. Short failure had become one of the most common PCB problems in field. In the present study, the various short failures had been summarized and classified into four typical categories: (1) quality defects of PCB; (2) foreign conductive metal residues on PCB; (3) electrochemical migration (ECM, conductive anodic filament (CAF) is regarded as one type of ECM) (4) ionic residues. The fault features, analysis methods, failure mechanisms and preventive measures were discussed through comprehensive analysis on the real short failure cases of each type. It is suggested identifying fault features first, which is helpful to choose proper analysis methods, then find out root failure causes accurately, and put preventive measures specifically from electronic auxiliary materials controlling, PCB quality controlling, PCB layout design or electronic assembly management.

Sandwiched cellulose nanofiber /boron nitride nanosheet /Ti3C2Tx MXene composite film with high electromagnetic shielding and thermal conductivity yet insulation performance

Metal Matrix Composite Thermal Management Materials

Transparent, high gas barrier films are crucial in the medical, food, and electronic industries. The main properties required for electronic devices such as flexible displays include transmittance of >90% and oxygen transmission rates (OTRs) and water vapor transmission rates (WVTRs) of 10–3 to 10–6 cc(g) m–2 day–1. Herein, we report reduced graphene oxide (rGO)/inorganic and organic/inorganic composites coated on poly(ethylene terephthalate) (PET) film with superior oxygen and water vapor barrier properties and high transmittance. The OTR (at 23 °C, 0% relative humidity) and WVTR (at 37.8 °C, 100% relative humidity) values of the composite films (140 μm) decreased by 8 × 104 times and 6.71 × 102 times, respectively, relative to those of the PET substrate film (125 μm). The transmittance of the composite films at 550 nm was 84%, corresponding to only a 9% decrease compared to that of the PET film. Additionally, with only nanolayers of SiOxNy (100 nm) and rGO (13 nm) coating on the PET substrate, the OTR and WVTR were reduced by 2000 times and 470 times, respectively. A polyvinylidene fluoride/rGO (PVDF/rGO) layer on the SiOxNy/PET substrate showed 8.8 × 105 times lower oxygen permeability and 1.6 × 104 times lower water permeability compared to those of PVDF/rGO on the PET substrate, implying that the inorganic SiOxNy nanolayer is crucial, affording a synergistic effect toward the barrier film. The gas permeabilities of the composite films strongly depend on the design of the coating structure, rGO content, and blend ratio of PVDF and PMMA; this allows efficient control of the nanodefects of the composite film. This study shows the significance of inorganic materials and the synergistic effect of composites on barrier films, which are required for applications in organic electronic devices and packaging materials.

Flame-retardant cycloaliphatic epoxy systems have long been studied; however, the research suffers from slow and unsatisfactory advances. In this work, we synthesized a kind of phosphorus-containing difunctional cycloaliphatic epoxide (called BCEP). Then, triglycidyl isocyanurate (TGIC) was mixed with BCEP to achieve epoxy systems that are rich in phosphorus and nitrogen elements, which were cured with 4-methylhexahydrobenzene anhydride (MeHHPA) to obtain a series of flame-retardant epoxy resins. Curing behaviors, flame retardancy, thermal behaviors, dielectric performance, and the chemical degradation behaviors of the cured epoxy system were investigated. BCEP-TGIC systems showed a high curing activity, and they can be efficiently cured, in which the incorporation of TGIC decreased the curing activity of the resin. As the ratio of BCEP and TGIC was 1:3, the cured resin (BCEP1-TGIC3) showed a relatively good flame retardancy with a limiting oxygen index value of 25.2%. In the cone calorimeter test, they presented a longer time to ignition and a lower heat release than the commercially available cycloaliphatic epoxy resins (ERL-4221). BCEP-TGIC systems presented good thermal stability, as the addition of TGIC delayed the thermal weight loss of the resin. BCEP1-TGIC3 had high dielectric performance and outperformed ERL-4221 over a frequency range of 1 HZ to 1 MHz. BCEP1-TGIC3 could achieve degradation under mild conditions in an alkali methanol/water solution. Benefiting from the advances, BCEP-TGIC systems have potential applications as electronic packaging materials in electrical and electronic fields.

The integrated circuits industry has been continuously producing microelectronic components with ever higher integration level, packaging density, and power density, which demand more stringent requirements for heat dissipation. Electronic packaging materials are used to pack these microelectronic components together, help to dissipate heat, redistribute stresses, and protect the whole system from the environment. They serve an important role in ensuring the performance and reliability of the electronic devices. Among various packaging materials, epoxy-based underfills are often employed in flip-chip packaging. However, widely used capillary underfill materials suffer from their low thermal conductivity, unable to meet the growing heat dissipation required of next-generation IC chips with much higher power density. Many strategies have been proposed to improve the thermal conductivity of epoxy, but its application as underfill materials with complex performance requirements is still difficult. In fact, optimizing the combined thermal-electrical-mechanical-processing properties of underfill materials for flip-chip packaging remains a great challenge. Herein, state-of-the-art advances that have been made to satisfy the key requirements of capillary underfill materials are reviewed. Based on these studies, the perspectives for designing high-performance underfill materials with novel microstructures in electronic packaging for high-power density electronic devices are provided.

With the miniaturization and integration of microelectronic components, the demand for high-thermal-conductivity electronic packaging materials has grown substantially. Diamond/copper (Dia/Cu) composites have become a focus of research due to their ultra-high thermal conductivity and low coefficient of thermal expansion. However, poor interfacial bonding and high interfacial thermal resistance between diamond and copper limit their practical performance. This paper reviews strategies to enhance interfacial bonding, including diamond surface metallization (e.g., electroless plating, magnetron sputtering, molten salt method, vacuum electroplating, and embedding) and copper matrix alloying (e.g., gas atomization and alloy smelting), and evaluates their effects on thermal transport properties. Additionally, the influence of preparation processes—such as vacuum hot-pressing sintering, high-temperature high-pressure sintering, spark plasma sintering, and melt infiltration on the microstructure and thermal conductivity of composites are discussed. Key factors including diamond surface roughness, particle size, volume fraction, and sintering conditions (e.g., temperature, pressure, and dwell time) are analyzed. Experimental and computational studies demonstrate that systematic optimization of these factors enhances the thermal conductivity of Dia/Cu composites, providing critical insights for developing next-generation high-performance electronic packaging materials.

Enhanced thermal conductivity of epoxy composites reinforced with oriented polydopamine-graphene foam complexed by metal ions

Electronic packaging materials and thermal interface materials (TIMs) are widely used in thermal management. In this study, the epoxy composites with core‐shell structure SiC@SiO 2 nanowires (SiC@SiO 2 NWs) as fillers could effectively enhance the thermal conductivity of epoxy composites. The unique structure of fillers results in a high thermal conductivity of epoxy composites, which is attributed to good interfacial compatibility epoxy matrix and bridging connections of SiC@SiO 2 NWs. From neat epoxy to 2.5 wt% loading of SiC@SiO 2 NWs, the thermal conductivity is significantly increased from 0.218 to 0.391 W m −1 K −1 , increased by 79.4%. In addition, the composite with 2.5 wt% filler possess lower coefficient of thermal expansion and better thermal stability than that of neat epoxy. All these outstanding properties imply that epoxy/SiC@SiO 2 NWs composites could be the ideal candidate for TIM.

Review on Brazing of High Volume Faction SiC p /Al Composites for Electronic Packaging Applications

Ni3Sn4 intermetallic compound (IMC) is a critical material in modern electronic packaging and soldering technology. Although Ni3Sn4 enhances the strength of solder joints, its brittleness and anisotropy make it prone to crack formation under mechanical stress, such as thermal cycling or vibration. To improve the plasticity of Ni3Sn4 and mitigate its anisotropy, this study employs first-principles calculations to investigate the mechanical properties and electronic structure of the doped compounds Cex Ni3−xSn4 (x = 0, 0.5, 1, 1.5, 2) by adding the rare earth element Ce. The results indicate that the structure Ce0.5 Ni2.5Sn4 has a lower formation enthalpy (Hf) compared to other doped structures, suggesting enhanced stability. It was found that all structures exhibit improved plasticity with Ce doping, while the Ce0.5 Ni2.5Sn4 structure shows relatively minor changes in hardness (H) and elastic modulus, along with the lowest anisotropy value (AU). Analysis of the total density of states (TDOS) and partial density of states (PDOS) reveals that the electronic properties are primarily influenced by the Ni-d and Ce-f orbitals. At the Fermi level, all Cex Ni3−xSn4 (x = 0, 0.5, 1, 1.5, 2) structures exhibit metallic characteristics and distinct electrical conductivity. Notably, the TDOS value at the Fermi level for Ce0.5 Ni2.5Sn4 lies between those of Ni3Sn4 and other doped structures, indicating good metallicity and conductivity, as well as relative stability. Further PDOS analysis suggests that Ce doping enhances the plasticity of Ni3Sn4. This study provides valuable insights for the further application of rare earth elements in electronic packaging materials.

The effects of dispersion states of carbon nanotubes on thermal conductivity and Micro-hardness of Multi-walled carbon nanotube (MWCNT) reinforced copper nanocomposites were investigated. The nanocomposites were fabricated in a novel method. It involves the synthesis of MWCNT-implanted copper composite spheres and the preparation of the MWCNT/copper bulk materials using vacuum hot pressing and hot rolling. The thermal conductivity of the composites with different concentration of MWCNTs were measured. Although the coefficient of thermal conductivity decreases with the increase of the MWCNT content, it is still high enough to be used as electronic packaging materials even the concentration of MWCNTS in the composite is up to 5 wt%. Furthermore, the microhardness of the nanocomposites are much higher than that of pure copper, which is ascribed to the good dispersion of the MWCNTs in matrix.

High electromagnetic wave absorption and thermal management performance in 3D CNF@C-Ni/epoxy resin composites

High-silicon aluminum alloy (high-Si Al alloy) usually used as the electronic packaging materials on the radar on ships have a susceptibility to corrosion, reducing the life of radar on ships. How to improve the corrosion-resistance ability of high-Si Al alloy is still a challenge. In this paper, we introduced superhydrophobicity on high-Si Al alloy surface by electrochemical etching to improve the corrosion-resistance. The variation of surface wettability with the etching time was subsequently studied. A better superhydrophobicity with water contact angle of 163° and roll-off angle of 5° was obtained at 12 min etching time. This superhydrophobicity can effectively prevent the corrosive solution to corrode the high-Si Al alloy surface and increase the service life.

Current developments in electronic packaging materials