Key Technology Research on Advanced Packaging Low-Loss Dielectric Materials in High-Speed and High-Frequency Applications

Introduction: Evolution of Performance Requirements for Dielectric Materials in the 5G Era

With the rapid evolution of 5G communication technology into the millimeter wave band (above 24GHz) and future explorations into terahertz frequencies with 6G technology, the electronic packaging field is facing unprecedented challenges regarding signal integrity. In scenarios involving high-speed digital transmission and high-frequency analog signal processing, traditional dielectric materials like FR-4 can no longer meet increasingly stringent performance requirements. This technological bottleneck has directly driven a wave of innovation and research development for low-loss dielectric materials.

In modern electronic systems, signal transmission loss primarily consists of conductor loss and dielectric loss. Conductor loss can be effectively controlled by improving copper foil manufacturing processes (such as using reverse copper foil technology to reduce surface roughness to Ra<0.3μm), while optimizing dielectric loss requires fundamental innovations at the molecular structure level. Particularly in the millimeter wave band, polarization relaxation effects in dielectric materials are significantly enhanced, causing drastic fluctuations in both dielectric constant (Dk) and loss factor (Df) with increasing frequency; this imposes extremely high stability requirements across a wide frequency range.

Key Performance Indicator System for Low-Loss Dielectric Materials

Core Importance of Electrical Performance Parameters When evaluating low-loss dielectric materials, it is essential to establish a multidimensional performance evaluation system. In terms of electrical performance, absolute values of Dk and Df along with their frequency stability are core indicators. Ideal high-frequency dielectric materials should maintain Dk values between 2.5-3.5 within a range from 10-100GHz without exceeding ±5% fluctuation; meanwhile, Df should be kept below 0.003. Such stability arises from precise control over polar functional groups within the material—for instance, introducing fluorinated structures or cyclic molecular chains to suppress dipole moment orientation polarization.

Synergistic Optimization of Thermal Mechanical Properties In addition to electrical characteristics, matching thermal mechanical properties is equally crucial. A low coefficient of thermal expansion (CTE<20ppm/℃) ensures thermal compatibility with silicon chips while avoiding interfacial delamination caused by temperature cycling; an appropriate Young's modulus (1-3GPa) provides sufficient mechanical support without leading to brittle fracture due to excessive rigidity. Notably, controlling volume shrinkage during material curing must remain strictly under 5%, as excess shrinkage could lead to internal stress accumulation and warping—critical factors for large-area packaging applications.

Engineering Considerations for Environmental Stability Under complex working conditions, moisture absorption rates must remain below 0.3%, since water ingress significantly increases dielectric losses (with water molecules having Df values exceeding 0.1). Additionally, materials need at least twelve months' storage stability—a challenge for polymer formulation design that modern solutions typically address through dual curing mechanisms: initial cross-linking via UV initiation forms stable structures followed by heat curing which completes final property development.

Innovations Progress Made by International Leading Companies on Material Development

Molecular Design Innovations from Japanese Firms Japanese chemical companies exhibit significant technical advantages in this domain.Namics Corporation developed silica-filled composite materials utilizing unique surface treatment technologies that achieve copper foil bonding strengths up to 7N/cm while maintaining excellent filler dispersion properties.Their innovative spherical SiO2 filler particle size distribution control technique(D50=1 .2μm ) stabilizes material’s Dk value around3 .0±0 .1at2 GHz ,while CTE can be precisely adjusted downwards towards25 ppm /℃ . Toray Industries has designed PI-B type polyimide material through accurate molecular structural designs achieving exceptional performances such asD k =2 .7/D f =0 .002at20 GHz based upon rigid-flexible block copolymer architecture.Key aspects involve incorporating bulky side groups which inhibit chain packing density whilst ether linkages preserve moderate chain flexibility. n **Systematic Solutions Offered By European And American Enterprises ** nDuPont’s XP -Formulation B photosensitive dielectrics represent important breakthroughs beyond acrylic systems.This new class employs novel cationic photoinitiators yielding impressive resolution( down-to ≤2 μm line widths )and retainsDf <0 .003even at77 GHz mm-wave bands.Its distinctive cross-linked network achieves glass transition temperatures reaching170 ℃ ,whilst boasting industry-leading moisture uptake limitedto just o.o13%.The joint venture between Hitachi-DuPont presents another leap forward concerning temperature stabilities whereby optimized imidization procedures allow maintainedD k levels remainingwithin±o.l even after320 ℃high-temperature cures throughout varying degrees(Figure ).This reliability stems largely from meticulous arrangements found among rigid aromatic ring frameworks embedded inside respective polymer chains combined alongside terminal end-capping techniques employed therein! n ### Trends Of Material Development & Future Challenges **Research Directions For Multi-band Compatible Materials **Analyzing technological trajectories suggests prospects ahead where next five years might witnessDielectrics’Df metrics potentially breaking past thresholds set around≤o.o015sought mainly via ultra-low polarity polymers engineered accordingly.Examples include fully-fluorinated alkyl side-chain modifications or nano-pores introduced(pore ratios <o/o05%)aimed further reducing overall polarization levels.Simultaneously broad bandwidth compatibility emerges emerging focus area necessitating consistent performances spanning sub-six gigahertz right up until300 gigahertz ranges! Matching Demands On Integrated Manufacturing Processes As heterogeneous integration technologies advance,the corresponding dielectrics require adaptability amidst more intricate process conditions encompassing features such as:low-temperature cure compatibilities(<180 °C )in alignment w/ TSV methods,sensitivity tailored specifically suited towards laser direct imaging applicable RDL fabrication standards&ultra-thin film deposition capabilities(<five microns ),all requiring tighter collaborative efforts established amongst developers plus assembly manufacturers alike! Enhancing Reliability Validation Systems Long-term reliability assessment criteria surrounding these advanced HF-dielectrics still remains unestablished particularly addressing accelerated aging testing protocols specific targeting mm-wave spectrums.Investments aimed developing dedicated real-time monitoring devices capable tracking shifts occurring amid extreme environments(hot/humid cycles(85°C/85%RH))are necessary alongside constructing predictive lifespan models relevant critical applications including autonomous driving radar systems! ### Conclusion : Interdisciplinary Collaboration Driving Technological Breakthroughs Innovation pathways surrounding low-loss dielectrics hinge upon deep integrations bridging fields ranging across material sciences,electromagnetic theories,surface chemistries,and mechanical engineering domains.Currently witnessed advancements emerge prominently illustrated three distinct dimensions comprising heightened precision pertaining molecular architectures(such application-controlled radical polymerizations),interface engineering optimizations(concerning core-shell structured fillers),alongside progressive manufacturing innovations(e.g.,aerosol-deposited films).As quantum computing/thz communications evolve,new frontiers beckon wherein dielectrical components strive towards ultra-low losses(Df<o.o01)&tunable attributes paving way forth next-gen electronics foundations.