Reliable ultrasonic aluminum wire bonding of cylindrical lithium-ion battery cells depends strongly on the cleanliness and chemical state of the cell terminal surfaces. Residual organic contaminants and native oxide layers originating from manufacturing and handling can impair bond formation and reduce process yield. Laser cleaning is a promising non-contact surface preparation method; however, its effects on terminal surface chemistry and integrity under manufacturing-relevant conditions require further clarification. In this work, a single production-relevant pulsed laser cleaning parameter set was applied to commercially available cylindrical lithium-ion battery cells. The surfaces were characterized in terms of elemental composition, surface morphology, and residual organic contamination using complementary analytical techniques, including XRF, SEM-EDX, and LC-MS. The results show that laser cleaning induces measurable surface changes consistent with improved wire bondability while preserving nickel and aluminum terminal metallization. These findings support laser cleaning as a scalable pre-bond surface preparation method for battery pack manufacturing.
This paper focuses on developing a contactless jetting technique to apply a microparticle-based silver (Ag) sintering paste suitable for pressureless sintering of miniaturized optoelectronic components. Traditional soldering methods are limited by their lower thermal conductivity and the risk of remelting at elevated operating temperature (>200 °C), which can be addressed by employing advanced sintering techniques. We detail the optimization of a contactless jet dispensing process and analyze the influence of key parameters, such as cartridge pressure, needle lift, rising-time, and open-time, on the precision and reliability of material deposition. A volumetric flow model is developed as a qualitative framework to identify parameter dependencies. Through experimental validation using square-footprint LED dice, we demonstrate a linear correlation between open-time and dot volume while highlighting falling-time as a free parameter affecting dot morphology. The reliability of both the developed jetting process and the microparticle-based paste is confirmed through shear testing of LED dies on Direct Copper Bonded (DCB) substrates, achieving shear strengths exceeding 60 MPa after 1000 hours of storage at 200 °C. This methodology demonstrates the potential for the accurate and efficient application of sintering pastes in optoelectronic packaging and paves the way for future advancements in microelectronic assembly.
The continuous scaling of semiconductor devices, driven by Moore’s Law, demands advancements in interconnect technologies. Cu-to-Cu direct bonding has emerged as a critical solution for enabling ultra-fine pitch, high-density interconnections with superior electrical and thermal performance compared to traditional Cu-to-solder joints. This bonding method is pivotal for applications such as 3D integration, FOWLP, and 2.5D/3D packaging, supporting miniaturization, high-speed data transfer, and improved thermal management. However, Cu oxidation during processing presents a significant barrier, degrading bond integrity, increasing interfacial resistance, and complicating backend-of-line (BEOL) packaging integration. To address these challenges, we developed an ultra-thin (2–5 nm) Cu-selective oxide-suppression coating using standard industry-compatible techniques, including chemical vapor deposition (CVD) and liquid-phase deposition (LPD). The coating effectively prevents Cu oxidation during high-temperature thermal compression bonding (TCB) without requiring high-vacuum equipment or costly metal coatings, enabling scalability for heterogeneous packaging. RAIRS-QCM metrology validated the coating’s chemical stability and persistent oxidation resistance even after two months of ambient storage. Oxidation suppression efficiency of ~53% was confirmed by RAIRS characterization following an annealing at ~300°C in ambient air for 1 hour. Bonding evaluations were performed on 5 nm passivated Cu substrates under optimized bonding conditions. Shear testing revealed an average force of 40.7 ± 4.2 kgf/cm 2 , exceeding MIL-STD-883 requirements. Cross-sectional STEM confirmed a defect-free Cu-Cu bonded interface, while STEM-EDX analysis verified that the coating effectively suppressed oxidation without impeding Cu-to-Cu bonding. This work establishes the developed coating as a scalable, high-throughput solution to enhance Cu-to-Cu bonding reliability, enabling next-generation semiconductor packaging with improved electrical, mechanical, and thermal performance.
Despite advances in 2.5D and 3D packaging, ultrasonic wedge (stitch) bonding remains the industry standard due to its cost-effectiveness. However, the transition to copper (Cu) and palladium-coated copper (PCC) wire introduces reliability challenges, traditionally mitigated by expensive and environmentally concerning silver (Ag) plating on leadframes (LF). To address this, we developed a low-cost, ultrathin Cu-selective passivation coating that suppresses oxidation, enabling direct Cu-Cu bonding without Ag. This process-compatible coating was evaluated on Cu-LFs using 25 µm Al-1 wt% Si and PCC wires under varying thermal conditions (125 °C-200 °C). Optimization of bonding force, time, and ultrasonic power yielded substantial improvements in pull strength. Notably, while bare-Cu bonds failed at the oxidized interface, passivated samples failed at the wire neck, confirming superior bond integrity. This work highlights a promising, environmentally sustainable alternative to Ag plating, enabling reliable Cu-Cu stitch bonding for next-generation, low-cost IC packaging solutions.
This study reports, for the first time, the fully additive fabrication of miniaturized, embedded triple-stacked copper spiral inductors—an unprecedented achievement in multilayer inductor manufacturing. Using our novel Sequential Build-Up–Covalent Bonded Metallization (SBU–CBM) method, we demonstrate a etch-free, room-temperature process capable of producing complex 3D inductor architectures with sub-10 μm features and high vertical integration. Unlike conventional additive, subtractive or hybrid subtractive–additive techniques, the SBU–CBM method enables high-resolution laser-defined patterning, selective electroless copper deposition, and accurate optical alignment—completely eliminating the need for vacuum systems, chemical etching, or thermal sintering. The successful fabrication of three vertically interconnected spiral inductors through 10 μm copper microvias confirms the method’s unmatched capability in fabricating intricate multilayer geometries through a fully additive process. Optical microscopy and X-ray Computed Tomography (XCT) imaging validate the structural integrity, precise interlayer alignment, and continuous electrical connectivity across all layers. Critically, the method achieves uniform miniaturized copper strip widths of 10 μm, underscoring its strength in high-density packaging and next-generation integrated systems. This breakthrough establishes SBU–CBM as a transformative approach for realizing compact, high-performance, and scalable 3D embedded components in future electronic applications.
