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In the modern electronics industry, a substrate serves as a critical support structure, connecting and stabilizing electronic components. It's not only a core component of PCBs, but is also widely used in chip packaging, display panels, and various electronic devices. With the rapid advancement of technology, substrate technology has continuously evolved, from traditional rigid substrates to flexible substrates, and then to advanced glass and ceramic substrates. Its function has expanded from simple mechanical fixation to efficient electrical connections and thermal management. According to industry data, the global PCB market has exceeded $80 billion, and the substrate, as its foundation, directly impacts the reliability and performance of electronic products.
A substrate is the base material used to secure electronic components (such as chips, resistors, and capacitors). It is typically made of insulating materials such as epoxy, fiberglass, or ceramic, and covered with a conductive layer such as copper foil to form the circuit path. Simply put, the substrate acts like the "skeleton" of an electronic device, providing mechanical support while ensuring that the electrical interconnections between components do not fail due to vibration, thermal expansion and contraction, or other external factors. In electronics engineering, the term "fixing" a substrate has two meanings: first, the substrate itself is secured within the device housing or frame; second, the components are secured to the substrate. For example, during chip packaging, the wafer die is secured to the substrate through a bonding process, forming a complete integrated circuit module. This securing requires not only mechanical strength but also electrical performance and thermal conductivity. Bonding is a critical step in semiconductor manufacturing, securing the die to the substrate to prevent it from falling off or shorting during subsequent use.
substrate
The choice of substrate material directly determines its securing performance. Common materials include FR-4, which is affordable and mechanically strong, making it suitable for consumer electronics; ceramic substrates, which are heat-resistant and used in high-power devices; and glass substrates, commonly found in displays and high-end chip packaging, which offer excellent flatness and optical properties. These materials ensure that the substrate remains stable during the securing process and prevents deformation.
There are several types of fixing substrates.
Rigid substrate: This is the most common type and is made of hard materials such as FR-4 or metal substrates. They provide a sturdy mounting platform suitable for applications requiring high stability, such as desktop computers and automotive electronics. Rigid substrates have the advantage of strong bending resistance, but lack flexibility and cannot adapt to curved designs.
Flexible substrates: Made of soft materials such as polyimide (PI), they are bendable and foldable and are widely used in wearable devices and smartphones. Special adhesives are used in the mounting process to ensure components do not fall off when bent. The flexible substrate market is growing rapidly; according to statistics, the global flexible PCB market is expected to reach $15 billion in 2024.
Rigid-flex substrates: Combining the advantages of rigidity and flexibility, they are used in complex electronic systems such as medical devices and aviation equipment. They allow components to be fixed in some areas while enabling dynamic connections in other areas, greatly improving space utilization.
Glass substrates: Primarily used in liquid crystal display (LCD) and OLED panels, as well as advanced chip packaging. Glass substrates are highly flat and can precisely secure micron-level components. Since the 1970s, glass substrates have evolved from simple supports to high-precision carriers, enabling the integration of more transistors. In addition, metal substrates are used in high-heat applications, such as LED lighting, to ensure rapid heat dissipation and prevent component failure from overheating.
The process of securing substrates is central to electronics manufacturing and includes two stages: component mounting and substrate installation.
First, component mounting primarily relies on bonding technology. Traditional bonding uses solder or conductive adhesive to secure the chip to the substrate; advanced methods include ultrasonic bonding and laser bonding, which improve precision and speed. In PCB production, surface mount technology (SMT) is the mainstream: components are secured to the substrate surface through reflow soldering, ensuring a reliable electrical connection.
Second, the substrate itself is secured using rails, screws, or snap-fit systems. In device assembly, PCB mounting rails are used to prevent vibration-induced displacement, particularly in automotive and industrial applications. Modern designs emphasize screwless mounting, using slots or adhesives to simplify the process and improve production efficiency.
In the consumer electronics sector, smartphones and tablets rely on PCB substrates to secure countless components and enable high-speed data transmission. Ansys notes that PCBs are mechanical substrates used to secure circuit components and are essential to nearly all modern devices.
In automotive electronics, rigid substrates secure sensors and control modules, enabling autonomous driving technology. Electric vehicle battery management systems use metal substrates to secure power components and manage heat.
Medical devices such as heart rate monitors utilize flexible substrates, which can be attached to the body's curved surfaces for comfort. The aerospace industry favors ceramic substrates, which withstand extreme environments and ensure stable satellite communications.
Furthermore, in the 5G and AI eras, fixed substrates support high-density integration, such as HDI (high-density interconnect) substrates, which can secure more layers of circuitry and improve performance.