With the advancement of electronic technology, the integration of active electronic components has significantly progressed from micron to nanometer semiconductor processes. Consequently, there is a growing demand for passive components that can complement these active components. Electronic product market trends emphasize lightweight, compact designs. However, as the number of active components per unit volume increases due to enhanced semiconductor processing capabilities, the accompanying rise in passive component requirements necessitates more space. This inevitably enlarges the overall device footprint, diverging from market preferences. Moreover, since the total cost is directly proportional to the number of passive components used, cost reduction and space efficiency are crucial considerations. Therefore, enhancing passive component performance has become a key focus.
2. Integrated Passive Component Technology
Integrated Passive Devices (IPD) technology integrates various electronic functions, such as sensors, RF transceivers, MEMS, power amplifiers, power management units, and digital processors. It enables the creation of compact IPD products, thereby facilitating miniaturization and improving system performance. Whether reducing the dimensions and weight of entire products or adding functionalities within existing product volumes, IPD technology plays a pivotal role.
In recent years, IPD technology has emerged as a critical aspect of System-in-Package (SiP) implementations. It is poised to support the realization of multifunctional integration beyond the confines of Moore’s Law. Furthermore, integrating IPD technology into PCB board processing can bridge the expanding gap between packaging and PCB technologies.
3. Influence of IPD on PCB Board Technology
IPD integrated passive component technology has evolved from its initial commercial applications to progressively replace discrete passive components. It has experienced steady growth driven by industries such as ESD/EMI.RF, high-brightness LEDs, and digital hybrid circuits.
2. Introduction to thin film IPD technology
IPD technology can be classified into thick film and thin film processes based on manufacturing techniques. Thick film processes include LTCC (Low Temperature Co-fired Ceramics) technology, which uses ceramics as substrates, embedding passive components such as capacitors and resistors within the substrate. This technology forms integrated ceramic components through sintering, significantly reducing component space. However, manufacturing complexity and costs increase with additional layers, limiting LTCC to specific functions. HDI PCB technology embeds components within high-density interconnection boards, primarily suited for digital systems. It supports only distributed capacitors and medium-to-low precision resistors due to challenges with handling increasingly smaller components using SMT equipment. Despite the maturity of embedded PCB technology, product characteristics suffer, and precise tolerances are challenging due to buried components within multilayer boards, complicating repairs and adjustments post-failure. In contrast, thin film IPD technology utilizes semiconductor processes to integrate circuits, capacitors, resistors, and inductors, offering high precision, repeatability, compact size, reliability, and cost-efficiency, positioning it as the future IPD mainstream. This article focuses on introducing thin film IPD technology.
3. Development status of thin film integrated passive component technology
Thin film IPD technology employs processes like exposure, development, coating, diffusion, and etching to fabricate resistors, capacitors, inductors, low-inductance ground planes, and interconnecting transmission lines for passive components. It requires meticulous attention to performance and accuracy while minimizing process complexity, typically employing 6 to 10 masks. Each passive component occupies less than 1 mm² to compete effectively with SMT discrete components in terms of size and cost-effectiveness. Various manufacturers have developed thin film IPD structures:
– Telephus utilizes thick copper processes to enhance performance for passive component-only lines, reducing costs and dimensions, particularly beneficial for wireless communication and integrated RF modules through low-k materials that lower parasitic capacitance.
– IMEC’s thin film technology employs electroplated copper for interconnections, BCB for dielectric layers, and Ni/Au for final surface connections, utilizing up to 4 metal layers.
– Dai Nippon’s IPD resistors primarily use Ti/Cr, capacitors are anodized to Ta₂O₅, and inductors are designed with microstrip lines or spiral configurations.
– SyChip employs TaSi for resistors, Si₃N₄ for capacitor dielectrics, Al for upper electrodes, and TaSi for lower electrodes, with aluminum for inductor and circuit materials. Some companies are exploring MEMS processes for IPD development.
4. Structure and process of thin film integrated passive component technology
Thin film processes differ from thick film primarily in film thickness: thick film exceeds 5μm~10μm, while thin film ranges from 0.01 μm~1 μm. Different processes and materials are required to simultaneously produce resistors, capacitors, and inductors using thin film technology, integrated into semiconductor manufacturing processes with mature technological development. Integration requires material compatibility between components, followed by process design. Thin film IPD integrated passive components can be produced on various substrates like silicon wafers, alumina ceramics, or glass, integrating resistors, capacitors, and inductors into one. Process technologies include lithography, thin film deposition, etching, electroplating, and electroless plating. Active components can also be combined on silicon wafers to meet multifunctional requirements.
– Thin film resistor processing employs sputtering to deposit resistance materials onto insulating substrates, followed by photoresist and etching to create desired resistance patterns. Materials must account for temperature coefficient of resistance (TCR), with fabrication methods including vacuum evaporation, sputtering, thermal decomposition, and electroplating.
– Film capacitors use MIM (Metal-Insulator-Metal) structures for high-frequency applications, minimizing parasitic resistance and depending on dielectric material’s natural frequency. Surface roughness of Ra<0.3 μm on substrates is critical to prevent electrode punctures.
– Thin film inductor processing involves designing to reduce parasitic capacitance and improve component quality factor (Q). Electroplating is used to achieve required inductance wire thickness, with substrate surface roughness affecting high-frequency performance.
5. Impact of IPD technology on PCB board technology development
PCB technology is advancing towards higher precision, density, and integration with IC packaging. Integrating passive components aligns with modern electronic system trends, with IPD as a crucial System-in-Package (SiP) implementation. IPD integrated passive components offer high wiring density, small size, light weight, and integrate resistors, inductors, and capacitors effectively for improved signal transmission and reduced costs. Strengthening IPD passive integrated PCB processes enhances substrate material properties, reduces costs, and accelerates applications in microwave communications and high-density integration, improving overall electronic system efficiency.
6. Conclusion
Thin film IPD integrated passive component technology integrates multiple electronic functions, enabling miniaturization and enhanced system performance, replacing bulky discrete passive components. Introducing IPD technology into PCB processing bridges the gap between packaging and PCB technologies, contributing to practical and industrialized passive integration. This advancement supports diverse applications in aerospace, medical, industrial control, and communications industries, underscoring its significance in enhancing PCB enterprise competitiveness and domestic industry advancement.
