Bad cell phone signal? Maybe the PCB material was not chosen correctly!

 

 

Having “signal problems”? Ever wondered why your phone have poor signals at home or in the office?

It’s not just about the cell sites—the circuit board (PCB) in side your phone also plays a big role.

With advanced materials that cut down on signal loss, your mobile network and Wi-Fi signal can offer more stable connections.

 

 

(Source : Pexel.com)

 

“Hello? Can you hear me? Sorry, the signal's bad…” Sometimes it's real—sometimes it's just an excuse.

 

In drama, this scene often happens when a character wants to hang up at an awkward moment.

 

But have you ever thought about this? The material inside your phone can actually decide your phone's signal.

 

 

Think back to the earliest mobile phones, when antennas were big, protruding rods. Later, they became built-in, and now phones feature sleek metal bodies—but signal strength has become more stable than ever. The key behind this improvement isn't just more cell towers; the materials inside the phone are quietly making a difference.

 

 

Modern smartphones require high-performance materials primarily due to demands in signal transmission, heat resistance, and durability. The internal printed circuit boards (PCBs), responsible for high-speed signal transmission, must employ materials with a low dielectric constant (Dk) and low dissipation factor (Df) to reduce signal delay and energy loss, ensuring the stability of high-speed networks such as 5G and Wi-Fi 6. Traditional plastic materials tend to interfere with signals, whereas high-performance materials help maintain signal clarity and prevent attenuation.

 

 

Even under severe internal heating, high-temperature-resistant and low-moisture-absorption materials ensure stable circuit operation, preventing PCB deformation or degradation while protecting performance in humid environments. At the same time, these materials offer high mechanical strength and durability, enabling smartphones to be lighter yet more resistant to drops. Such characteristics make high-performance resins an indispensable material in product design!

 

Modern PCBs must possess properties such as low loss, low dielectric constant (Dk), high thermal resistance (Tg), and strong mechanical strength to support high-frequency applications like 5G, Wi-Fi 6E, and millimeter-wave communications. These properties are achieved through the combination of four key components: resins, fillers, copper foils, and additives. Next, let's take a closer look at how these materials influence the signal quality in smartphones!

 

 

Resin: The key material that determines PCB signal transmission

 

Resin is the fundamental material of PCBs (Printed Circuit Boards), influencing signal transmission speed, stability, and durability. In high-frequency applications, the dielectric constant (Dk) and dissipation factor (Df) of the resin are the most critical indicators. A lower Dk results in less signal attenuation, while a lower Df reduces energy loss, enabling smoother operation of technologies such as 5G and Wi-Fi 6E. Beyond signal transmission, resin also affects thermal resistance (Tg), mechanical strength, and moisture absorption, ensuring that PCBs remain stable even in high-temperature environments. Therefore, selecting the right resin is the key to enhancing PCB performance!

 

(Extensive reading: Low Dielectric Resins (2): Features that are often used in product development in the electrical and electronic field !!)

 

The following is a comparison of the relevant properties of these four types of resins, which can be used as a reference. Possible materials can then be selected according to the specific application requirements.

 

 

Table 1. Comparative Analysis of Four Types of Resins

 

Property	Biphenyl Epoxy Resin	PPO (Polyphenylene Oxide)	Hydrocarbon Resin	PTFE (Polytetrafluoroethylene)
Dk (Dielectric Constant)	3.2 – 3.5	2.5 – 2.7	2.3 – 2.6	2.0 – 2.1 (Lowest)
Df (Dissipation Factor)	0.002 – 0.008	0.001 – 0.004	0.001 – 0.002	0.0005 – 0.001 (Lowest Loss)
Water Absorption	Low	Very Low	Minimal	Almost 0 (Best)
Heat Resistance	180 – 250 °C	180 – 260 °C	100 – 160 °C	260 – 300 °C (Best)
Typical Applications	Smartphones, Wi-Fi, 5G PCBs	High-frequency PCBs, mmWave Radar	5G Base Stations, Wi-Fi 6E, mmWave PCBs	Aerospace, Military Radar, Ultra-high-frequency Microwave Communications

 

 

How to Choose the Right Resin?

 

High-speed PCBs / 5G Communications

→ Hydrocarbon Resin is the best choice (lowest Dk/Df, suitable for millimeter-wave applications).

 

IC Packaging / High-temperature Electronics

→ Biphenyl Epoxy Resin is ideal (high thermal resistance, suitable for semiconductor packaging).

 

Heat-resistant & Flexible Electronics

→ PPO is more suitable (ideal for flexible PCBs and automotive electronics).

 

Low-cost 5G PCB Materials

→ Hydrocarbon Resin can serve as a PTFE alternative (low Dk/Df, low moisture absorption).

 

 

 

Fillers: The Unsung Heroes Enhancing PCB Strength and Stability

 

Fillers are an indispensable component of PCB materials, primarily used to enhance mechanical strength, reduce thermal expansion (CTE), and improve dielectric properties. With the rise of 5G and high-frequency communication devices, PCBs must not only transmit signals quickly but also remain stable under high-temperature and high-frequency conditions—this is where fillers play a critical role.

 

The proportion and distribution of fillers directly affect PCB performance. For example, high-loading ceramic fillers can reduce thermal expansion, ensuring PCBs maintain dimensional stability under high temperatures, making them suitable for 5G base stations and millimeter-wave antennas. Therefore, selecting the appropriate filler combination not only improves PCB durability but also ensures more stable and reliable signal transmission.

 

 

Table 2. Comparison of Four Types of PCB Fillers

 

Property	Ceramic Filler	Glass Fiber	Silica Filler	Hollow Silica
Primary Function	Reduce thermal expansion, improve heat resistance	Enhance mechanical strength, prevent deformation	Reduce moisture absorption, improve signal stability	Reduce density, improve dielectric properties, enhance heat dissipation
Coefficient of Thermal Expansion (CTE)	Lowest, suitable for high-frequency PCBs	Medium, provides rigidity	Low, improves dimensional stability	Relatively low, suitable for high-frequency and lightweight applications
Mechanical Strength	High, enhances impact resistance	Highest, ideal for rigid PCBs	Low, mainly for signal optimization	Medium, improves impact resistance and mechanical strength
Dielectric Properties (Dk/Df)	Excellent, suitable for 5G high-frequency applications	Good, slightly higher than ceramic fillers	Outstanding, reduces signal loss	Good, lowers Dk, suitable for high-frequency applications
Heat Resistance	Highest, can exceed 200 °C	High, suitable for standard PCB environments	Medium, with low moisture absorption	Medium, suitable for medium to high-temperature environments
Moisture Absorption	Low, suitable for high-humidity environments	Medium, long-term absorption may affect performance	Lowest, maintains signal stability	Low, maintains stable performance
Typical Applications	5G base stations, high-frequency PCBs, millimeter-wave radar	Smartphone PCBs, consumer electronics	High-speed PCBs, low-loss applications	High-frequency PCBs, lightweight composites, electronic packaging

 

 

With the rapid advancement of technology, the material requirements for PCBs have become increasingly diverse. In addition to traditional fillers such as ceramic, glass fiber, and silica, many emerging fillers are gaining attention to meet the demands of high-frequency, high-thermal-conductivity, and flexible electronic applications. In the high-frequency PCB sector, graphene and hexagonal boron nitride (h-BN) nanosheets are ideal fillers for 5G, millimeter-wave radar, and high-power components due to their exceptional thermal conductivity and low dielectric loss. Additionally, aluminum nitride (AlN) is widely used in high-power electronic devices because of its high thermal conductivity and low coefficient of thermal expansion (CTE).

 

 

On the other hand, to improve PCB weight and signal stability, hollow silica has gained attention in recent years, as it can reduce the dielectric constant (Dk) and lower material density, making it especially suitable for high-frequency and lightweight devices. Carbon nanotubes (CNTs), with their exceptional mechanical strength and electrical conductivity, are used as conductive fillers and for electromagnetic interference (EMI) shielding. In the field of flexible electronics, dielectric elastomer microparticles provide tunable dielectric properties, making them ideal for flexible circuits, wearable devices, and electronic skin. The development of these emerging fillers will continue to drive advancements in PCB technology, laying a stronger foundation for future high-performance electronic products.

 

(Extensive reading: Nano hollow silica(SiO₂)-5G Low K, heat insulation, low reflection AR film material)

 

 

Copper Foil: Conductivity Impacts Signal Quality

 

In PCBs, copper foil serves as the conductive layer, providing essential electrical connections for electronic devices. The quality of copper foil directly affects PCB performance, including signal transmission speed, stability, and reliability. Copper foil must have extremely high conductivity to transmit signals efficiently without excessive energy loss. To achieve this, high-purity copper foil is typically selected and often undergoes specialized surface treatments, such as gold or silver plating, to enhance corrosion resistance and conductivity.

 

With the evolution of electronic products, the choice of PCB materials has become increasingly diverse. Traditionally, copper foil has dominated PCB manufacturing due to its excellent conductivity and mature processing technology. However, as demands for high-frequency, high-power, and lightweight applications increase, traditional materials face certain challenges. Consequently, many new materials are gradually entering the market with the potential to replace copper foil.

 

Materials such as metal substrates, glass substrates, and ceramic substrates offer superior thermal management and mechanical strength, making them particularly suitable for high-frequency and high-power applications. Polyimide (PI) and carbon-fiber substrates, with their high-temperature resistance and lightweight properties, are increasingly prominent in high-performance electronics. Additionally, aluminum substrates, with excellent heat dissipation and lower cost, have become a popular choice in certain applications. The following section provides several potential substrate materials and compares their respective characteristics.

 

 

Table 3. Comparison and Progress of Various PCB Substrates

 

Material Type	Advantages	Challenges	Potential Applications	Development Companies / Research Progress
Copper Foil	Widely used, excellent conductivity, mature processing technology	Prone to oxidation, relatively heavy	Broad PCB applications, including consumer electronics, communications, automotive, etc.	Most copper foil materials are provided by existing suppliers such as Sumitomo Metal, DuPont, etc.
Metal Substrate	Superior thermal management, suitable for high-power applications, high stability	Higher cost, complex processing	LED, power electronics, high-frequency/high-power applications	Companies such as Nokia and Acrel are conducting research on metal substrates
Glass Substrate	Good high-frequency performance, high strength, heat resistance	Brittle, difficult processing, higher cost	High-frequency communications, aerospace, specialized environments	Corning has been researching glass substrate technology
Ceramic Substrate	Excellent high-temperature stability, strong heat dissipation, high corrosion resistance	High cost, difficult processing	High-power applications, aerospace, medical electronics	Companies such as Murata, Kyocera, and TE Connectivity invest in ceramic substrates
Polyimide (PI)	High heat resistance, good electrical properties, lightweight	Higher cost, requires complex processing	High-frequency, high-temperature, high-performance applications (e.g., aerospace, medical electronics)	PI research companies include DuPont and SABIC
Carbon Fiber Substrate	High strength, low weight, good mechanical properties, good thermal conductivity	Higher cost, difficult processing	High-performance electronics, military, aerospace	Some carbon fiber companies and research institutes, such as Toray and Hexcel, are developing this technology
Aluminum Substrate	Excellent thermal management, lower cost, lightweight	Prone to corrosion, lower mechanical strength, complex processing	High-power electronics, LED lighting, power electronics	Companies exploring aluminum substrates include Aavid and Advanced Thermal Solutions

 

 

In modern PCB materials, flame retardants and silane coupling agents are two very important additives, playing a key role in enhancing PCB performance, particularly in terms of safety, heat resistance, and mechanical properties.

 

Flame retardants are chemicals added to PCB materials to improve their fire resistance. Common flame retardants include phosphorus-based, chlorine-based, and nitrogen-based compounds. These chemicals release flame-inhibiting substances when heated or exposed to fire, reducing the spread of flames or delaying the combustion process. With the rise of environmental standards, halogen-free flame retardants (containing no chlorine, bromine, or other halogens) have become the mainstream choice due to their lower impact on the environment and human health, aligning with global green design principles.

 

In PCBs, fillers and resins often face issues with insufficient interfacial adhesion, which silane coupling agents effectively address. The active groups in silane molecules react chemically with resins, metals, or inorganic materials to form stable chemical bonds, enhancing adhesion between components. Additionally, silane coupling agents improve PCB water resistance, aging resistance, and UV resistance, which is crucial for high-end electronic products operating in extreme environments.

 

 

Table 4: Potential Applications of Silane Coupling Agents in PCBs

 

Application Area	Mechanism / Principle
Improve adhesion	Enhance chemical bonding between copper layers and epoxy resin, improving adhesion and preventing delamination.
Improve heat resistance	Increase the PCB's heat resistance, preventing delamination or degradation between copper layers and substrate under high temperatures.
Improve dielectric properties	Reduce moisture absorption, minimizing the impact on dielectric constant and maintaining stable electrical performance.
Enhance mechanical properties	Form cross-linked structures to strengthen the material's mechanical properties, improving impact resistance and wear resistance.

 

 

 

The stability of modern smartphone signals depends not only on the coverage of telecom base stations but also on the high-performance materials used inside the phone. In particular, the PCB (printed circuit board) materials ensure stable signal transmission and improved network quality through low dielectric constant (Dk) and low dissipation factor (Df).

 

Each of these materials plays a critical role—whether in reducing signal loss, enhancing mechanical strength, or improving heat resistance and durability. As new technologies emerge, the demand for and development of these materials continue to grow.

 

So, next time your phone signal is poor, don't be too quick to blame the base station—

 

it might just be that the materials inside your phone aren't performing at their best.

 

From the resins to the copper foil, every detail can affect your network experience.

 

Understanding the science behind these technologies helps us take a more informed and rational approach to the everyday "signal problems" we encounter.