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Ink is not a supporting role in high-speed circuit design; its material properties directly affect signal integrity. The table below summarizes several main types of ink and their key impacts on high-speed signals, helping you quickly understand the differences between them.
|
Ink Type |
Core Characteristics |
Main Impact on High-Speed Signals |
Typical Application Scenarios |
|
Carbon Ink (Conductive Ink) |
Low dielectric constant (Dk=3.5±0.2) and low dielectric loss (tanδ=0.008); controllable surface roughness (<0.5μm). |
Significantly reducesdielectric loss and conductor loss (due to skin effect); reduces signal attenuation, beneficial for maintainingsignal integrity. |
Antenna and transmission lines for 5G base stations/routers (28GHz frequency band); low-power scenarios in the 10-40GHz range. |
|
Solder Mask Ink |
Covers the surface of the circuit board, forming a protective layer. Its dielectric constant and loss factor are critical. |
If performance is poor, it will introduce significantdielectric loss, leading to signal distortion and attenuation. |
PCB solder mask layers in 5G communication devices, smartphones, etc. |
|
Nano-Silver Conductive Ink |
Contains 65–85% nano-silver, sheet resistance 5–50mΩ/□; often paired with specific dielectric layers. |
Achieves high-frequency signal (>5GHz)transmission loss<0.5dB/cm; improves impedance control accuracy through gradient deposition processes. |
Microstrip lines in 3D printed PCBs; high-density interconnect (HDI) boards; AI chip packaging. |
|
Liquid Metal Silicone (LMSG) Ink Ink |
Fully inorganic system, high conductivity(1.1×10⁶ S·m⁻¹),excellent thermal stability (resistant to 300℃). |
Excellent thermal stability ensures circuitreliability at high temperatures; good flexibility, suitable for bendable circuits. |
Flexible electronic devices, soft robotics; stable circuits in high-temperature environments. |
|
Low-Dk Packaging Ink |
Designed for display panel packaging, with a dielectric constant as low as2.5@100kHz. |
Reducesloss during signal transmission, improving response speed. |
Thin film packaging for flexible OLED panels. |
How Ink Affects Signals: An In-Depth Mechanism
In addition to the summary in the table, understanding the intrinsic mechanisms by which ink affects high-speed signals can help you make better decisions during design.
Controlling Signal Loss: Signal loss mainly comes fromdielectric loss and conductor loss.
Dielectric loss depends on the ink’sdielectric constant (Dk) andloss tangent (tanδ). The lower these two values, the less absorption and obstruction to high-speed signals. This is why, in the5G high-frequency band, the lowerDk and tanδ of carbon ink can significantly reduce losses compared to traditional materials (such asFR-4).
Conductor loss is especially critical at high frequencies whereskin effect is pronounced. The rougher the surface of the conductor, the greater the resistance encountered by high-frequency currents. The controllable surface roughness of carbon ink (<0.5μm) can reduce conductor loss by about20% compared to copper foil..
Ensuring Impedance Matching and Signal Integrity: High-speed circuits require thecharacteristic impedance (such as50Ω) of transmission lines to remain stable. The dielectric constant of the ink is a key parameter for calculating characteristic impedance, and its uniformity and stability directly affectimpedance control accuracy. If impedance is mismatched, it can lead to signal reflection and distortion. In 3D printing PCB technology, by optimizing the deposition process of conductive ink, the impedance accuracy of 50Ω microstrip lines can be controlled within±5%.
Enhancing System Reliability: Thethermal stability and mechanical properties of the ink are crucial for long-term reliability.
The inorganic liquid metal silicone (LMSG) ink developed by Southeast University can maintain circuit integrity at300℃ with minimal changes in conductivity.
In the multilayer stacked structures of 3D printing, matching thecoefficient of thermal expansion (CTE) of the ink with the substrate can effectively manage thermal stress. After1000 thermal cycles, the wall cracking rate can be reduced from12% to0.3%.
Design Considerations for High-Speed Applications
By integrating theoretical knowledge into design practice, you can focus on the following points:
Material Selection is Fundamental: For the 10-40GHz frequency range and low to medium power scenarios, carbon ink is a good choice for balancing performance and cost.
If extreme flexibility, high thermal conductivity, or exceptional temperature resistance (such as in aerospace or automotive electronics) is desired, consider liquid metal ink.
Process Innovation Empowers Design: 3D printing conductive ink technology allows forgradient deposition processes to dynamically adjust line width and spacing, achieving more precise impedance control and reducing development cycles from months to weeks..
Collaborative Design and Simulation: Modern electronic design requires considering materials, processes, and circuit structures together. During the simulation phase, the accurate parameters of the ink used, such asDk, tanδ, etc., should be input to predict system performance and reduce later iterations.
I hope this in-depth analysis provides valuable references for your high-speed circuit design. If you can share specific application scenarios (such as operating frequency, circuit structure, etc.), I can try to provide more targeted suggestions.
Previous Highlights:
Clarifying PCB Material Selection
Do You Really Understand Marks in PCBs?
Multilayer High-Level Board Stacking Design and Material Selection