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Over the last few years, the electronics industry has gone through a major paradigm shift as Moore’s law has plateaued and ultimately been laid to rest with the last ITRS edition published in 2016. Starting with the 22 nm CMOS node the increased process complexities raised the cost per transistor despite being able to cram more transistors into a given footprint and with sub-10 nm nodes reaching the limits of what is physically possible. The industry started to realize that shifting from CMOS scaling to a packaging focus would allow a continuation of Moore’s law and economic growth for decades to come: continuing miniaturization by cramming more functionality onto a smaller and smaller footprint using heterogeneous integration with a system level focus which Moore too predicted already in his seminal paper in 1965. That has led to the new Heterogeneous Integration Roadmap (HIR) founded by three IEEE sections with the first edition published in 2019 efectively replacing the ITRS and the “old” Moore’s law. Electronic packaging is a very complex field placing very different materials (hence the “heterogeneous”) in close proximity that has magnified a large number of compatibility issues with the two key aspects being CTE mismatch and heat dissipation. The packages are not only heterogeneous by material, but also by component type, circuit type, node and bonding/interconnect method. Materials are the key drivers to solve heat dissipation and thermal expansion issues as well as I/O contact miniaturization and a variety of processing challenges. The industry is now starting to realize that traditional solders can no longer serve as contact materials due to their relatively low electrical and thermal conductivity, high CTE, proclivity for IMC formation, low melting point, tendency toward creep and potential for wicking and shorts due to whisker growth especially in the case of SAC solder. The fact that it liquifies during reflow limits how small features can be made reliably to avoid shorting. Analyses have shown that we need a copper interconnect material to enable the performance increases desired by many and to fully utilize new miniaturization technologies such as Cu-pillar/bump and to maximize I/O density to exceed 200,000 in current silicon interposers. The key problems to be solved and the desired characteristics of such a material are: 1) High electrical and thermal conductivity – ideally like copper 2) No liquidus phase: sintered material – ideally copper 3) CTE adjustable over a wide range: Si to Cu i.e. 3-17 4) Short solder reflow profile (fast, moderate temperature, benign atmosphere) 5) No creep, robust electromigration, no whisker growth, no IMC 6) Ideally room temperature storage & shipping 7) Little to no pressure for high volume production Kuprion Inc. has develop and matured such a material with its ActiveCopper™ system that fulfills all those desired properties and has already been proven to work in numerous spaces. In 2022 interest exploded in a wide variety of bonding applications including but not limited to: 1×6 mm power devices, 10×10 mm large die, direct large heat sink to component attach, 2 inch DBC AlN and SiN to AlSiC base plate attachment, large thermal via formation, large area glass via and TSV fill, high density copper pillar attach, EMI shielding, and true 3D integration and component stacking. ActiveCopper is incredibly versatile, allows for CTE tailoring over a wide range, comes in a wide variety of pastes and inks, and will continue to garner increased interest in 2023.

Direct bond copper (DBC) substrates, composed of aluminum nitride (AlN) or silicon nitride (SiN) ceramics with copper (Cu) directly bonded to one or both sides, are used to dissipate heat due to their high thermal conductivity (200 W/mK and 50 W/mK respectively) and consequently high heat dissipation ability. However, to adhere copper to such ceramic surfaces requires a high-temperature process, as high as 1000°C. The CTE mismatch between Cu (17 ppm) and AlN (4.5 ppm) or SiN (3 ppm) leads to high mechanical stresses on cool-down that can cause cracking and failure after just a few cycles of heating and cooling. While SiN is strong enough to handle thousands of thermal shock cycles, its thermal conductivity is 5 times lower than AlN. However, AlN is weaker than SiN and tends to yield to mechanical stresses and breaks quickly, which has greatly limited its utility. Kuprion’s ActiveCopper™ materials provide a robust and less costly solution. ActiveCopper™ sintering materials exhibit extremely high conductivity (up to 393 W/mK) and easily bond directly to AlN and other ceramics at temperatures below 250°C. Kuprion’s innovative ActiveCopper™ materials can be formulated with CTE values that closely match a variety of ceramics and wide-bandgap (WBG) substrates including silicon carbide (SiC) and gallium nitride (GaN). Recent test results show superior reliability and performance by surviving more than 4,000 thermal shock cycles in air (-55°C to +150°C) without delamination or voiding, achieving a world record for DBC AlN.

According to embodiments of the present invention, an ink composition is provided. The ink composition includes a plurality of nanostructures distributed in at least two cross-sectional dimension ranges, wherein each nanostructure of the plurality of nanostructures is free of a cross-sectional dimension of more than 200 nm. According to further embodiments of the present invention, a method for forming a conductive member and a conductive device are also provided.

DuPont Microcircuit and Components Materials (MCM) business today announced a strategic collaboration with Kuprion Inc. to launch the ActiveCopper™ thick film paste suite of products to the electronics industry. “The addition of the ActiveCopper™ suite of products enhances our robust thick film paste portfolio and enables us to further create new solutions for the electronics materials market,” said Fallyn Flaherty-Earp, global marketing leader, Microcircuit and Components Materials, DuPont.  “The Kuprion team brings 13 years of R&D and formulation experience to these product lines. Combined with MCM’s extensive technical knowledge, we will be able to create unique and innovative solutions for our customers in key growth areas. ”Thick film pastes and inks developed with ActiveCopper™ maintain excellent thermal and electrical conductivity, while helping to address the effects of thermal expansion during the processing of and usage in electrical circuits and components. Another added benefit is the ability to effectively “tune” the thermal expansion of the copper for optimal performance and reliability when matched with a variety of materials such as ceramics, silicon, silicon carbide, and more.  The ActiveCopper™ family of pastes and inks provide solutions for a wide range of applications such as via fills, die attach, EMI shielding, conductive adhesive, and more.

Managing heat in electronics has become increasingly difficult as modern electronic systems become ever more powerful. Excess heat causes under performance and early failure in electronic devices. These issues are exacerbated in extreme environments like automobiles, aircraft and spacecraft where options for heat dissipation are limited. Electronic boards made from glass fiber-epoxy resin composite FR4 are poor thermal conductors and hence further impede waste heat removal. Kuprion is developing technologies to rapidly print and assemble electronic boards using Aluminum Nitride AlN which has a thermal conductivity up to 200 times that of FR4. All heat in electronics is generated by the components mounted to the board. Providing a higher thermal conductivity platform will increase the efficiency of waste heat removal, keeping electronics cooler. This will also make better use of existing downstream thermal management systems such as heat pipes and radiators.

Kuprion and Lockheed Martin Corp. joined forces to propose the use of a novel nanocopper materials technology that allows the use of copper as a versatile and effective thermal interface material. Kuprion’s nanocopper converts to bulk copper at temperatures 195-240°C in 5-8 min using standard solder reflow equipment under benign nitrogen environment, preventing oxidation during fusion. No pressure required. It has demonstrated drop-in replacement for solder. Thermal interface layers as thin as 2 micron have been achieved already via hand assembly of LED systems and have 20-25% improvement of Rth compared to AuSn solder. Bulk measurements revealed an intrinsic thermal conductivity of 277 W/mK. Coupled with RMS expertise in die attachment techniques and companion electronics, this system provides an ideal solution for realizing high performance TIM for power electronics. The material is readily dispensable and stencil printable for die bonding and PCB assembly. The small amounts of additives and surfactants completely evaporate during fusion, eliminating any post cleaning requirements. It lacks a liquid transition state, which eliminates wicking during processing allowing for very close spacing of components/leads / contacts. The formulation will be modified to reduce CTE to increase stability to thermal cycling for maximize life under harsh operating conditions.

Silicon carbide and gallium nitride power devices promise the ability to operate at high temperatures, however, power packaging has hit a plateau in thermal performance due to current die attach materials. Kuprion has developed a novel nanocopper-based die attach material that can be processed at traditional solder temperatures (200 C) yet enable operation at temperatures exceeding 300 C. Phase I efforts proved a 100% survival rate of SiC die on AlN substrates in both thermal cycling (-30 to +250 C) and thermal shock (-20 C to +195 C). Phase II will define the stability of fused nanocopper interfaces over a broader temperature range (-30 to +300 C) and develop methods to ensure long lifetime in relevant conditions. A functional power module will also be built as a demonstrator for future commercial and military partners.

An ink adapted for forming conductive elements is disclosed. The ink includes a plurality of nanoparticles and a carrier. The nanoparticles comprise copper and have a diameter of less than 20 nanometers. Each nanoparticle has at least a partial coating of a surfactant configured to separate adjacent nanoparticles. Methods of creating circuit elements from copper-containing nanoparticles by spraying, tracing, stamping, burnishing, or heating are disclosed.

According to embodiments of the present invention, a method of interconnecting nanowires is provided. The method includes providing a plurality of nanowires, providing a plurality of nanoparticles, and fusing the plurality of nanoparticles to the plurality of nanowires to interconnect the plurality of nanowires to each other via the plurality of nanoparticles. According to further embodiments of the present invention, a nanowire network and a transparent conductive electrode are also provided.

Vias may be established in printed circuit boards or similar structures and filled with a monolithic metal body to promote heat transfer. Metal nanoparticle paste compositions may provide a ready avenue for filling the vias and consolidating the metal nanoparticles under mild conditions to form each monolithic metal body. The monolithic metal body within each via can be placed in thermal contact with one or more heat sinks to promote heat transfer.

Metal nanoparticles and compositions derived therefrom can be used in a number of different applications. Methods for making metal nanoparticles can include providing a first metal salt in a solvent; converting the first metal salt into an insoluble compound that constitutes a plurality of nanoparticle seeds; and after forming the plurality of nanoparticle seeds, reacting a reducing agent with at least a portion of a second metal salt in the presence of at least one surfactant and the plurality of nanoparticle seeds to form a plurality of metal nanoparticles. Each metal nanoparticle can include a metal shell formed around a nucleus derived from a nanoparticle seed, and the metal shell can include a metal from the second metal salt. The methods can be readily scaled to produce bulk quantities of metal nanoparticles.

Current printed circuit boards (PCB) manufacturing technology forms the backbone of all modern electronics. However, today’s PCBs have two major limitations. First, they are made by a long and complicated subtractive manufacturing process using toxic chemicals and producing much waste, which inhibits rapid prototyping. Second, they are by nature thermal insulators with 0.25 W/mK thermal conductivity preventing the use of embedded component designs. This makes heat dissipation very difficult, especially when faced with the demands of today’s high-power electronics designs. Therefore, thermal management has become the key limitation to further improve performance of electronic systems, making the current PCB technology totally inadequate. Kuprion’s patented solution allows rapid prototyping of high thermal conductivity (up to 200 W/mK) multilayer printed circuit boards (PCBs) based on AlN ceramic technology. It provides up to 1000X improvement over FR4 technology (glass-fiber reinforced epoxy laminate). Circuit designs and vias can be directly printed with our patented nanocopper material. Extensive use of embedded components can be realized for improved functionality and increased compactness. Multiple layers can then be bonded together in one step using moderate processing conditions for rapid prototyping of multi-layer Ceramic Circuit Boards (CCBs) in just a few hours.

Kuprion and Ozark joined forces to propose the use of a novel nanocopper materials technology that allows the use of copper as a surface mount and thermal interface material. This material converts to bulk copper at temperatures around 200°C enabling high operating temperatures of up to 900°C. Coupled with Ozark ICs advances in die attachment techniques and companion electronics, this system provides an ideal solution for realizing high temperature power electronics. Initial tests using commercial LEDs have shown it to be thermally superior to solder running significantly cooler than AuSn enabling a 37% higher efficiency and light output. Bulk measurements revealed an intrinsic thermal conductivity of 277 W/mK. The material is readily dispensable and stencil printable for die bonding and PCB assembly. The small amounts of additives and surfactants completely evaporate during fusion, eliminating any post cleaning requirements. It lacks a liquid transition state, which eliminates wicking during processing allowing for very close spacing of components and leads / contacts. The paste formulation will be modified to inhibit grain growth at elevated temperature and to reduce CTE to increase stability to thermal cycling for maximize life under harsh operating conditions.

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A novel nanocopper-based packaging material was developed for robust, void-free thermal interfaces between LEDs and heat sinks/spreaders and other high-power components and devices allowing sub-10 micron thermal interfaces ensuring high heat transfer rates. Other applications are in TSV & wafer level packaging, embedded chip packaging, direct print of Si and glass interposers, wafer level bonding and die attachment as well as printed and flexible electronics. This solder-free nanocopper material overcomes the fundamental limitation of traditional solders, where the processing temperature sets an upper bound to the maximum possible operating temperature. Since nanocopper reverts to bulk copper upon fusion, it is capable of operating at temperatures above its original processing temperature making it the ideal high temperature packaging technology. Being pure copper in its fused state, the material can form contacts with 5-10x the thermal and electrical conductivity of typical solder systems. The material’s rheology can be tuned for drop-in replacement of solder paste on standard PCB assembly lines and other industrial dispensing and printing equipment. The resulting copper-based interconnects can exhibit improved creep resistance and enhanced reliability and robustness in low- and high-temperature operating environments.