Have you ever wondered why smartphones, laptops, and high-end industrial control equipment can become thinner and thinner while still boasting increasingly powerful performance? Despite having just as many internal electronic components, they achieve optimal space utilization. This is thanks to a high-end PCB manufacturing process—buried resistor and capacitor technology.

Simply put, this involves "hiding" resistors and capacitors, which are normally mounted on the surface of the PCB, directly within the internal layers of the circuit board, essentially giving the electronic components an "invisibility glitch." Today, we'll explain this technology in layman's terms and see just how amazing it is!

What are buried resistors and capacitors? How do they differ from traditional processes?

Let's first look at traditional PCB boards. Resistors and capacitors are directly soldered onto the board surface using surface mount technology, like "attaching small squares" to a circuit board. This not only takes up space but is also susceptible to external interference.

Buried resistor and capacitor technology, on the other hand, embeds resistors and capacitors directly into the internal layers of the PCB board. The resulting circuit board has a unique structural design: from bottom to top, it consists of a first dielectric layer, buried resistors, a circuit layer, and a second dielectric layer. A special polymer insulating layer is also applied to the portion of the buried resistor not covered by the circuit layer to protect it from chemical corrosion. This is key to the stable mass production of buried resistor and capacitor boards.

In short: traditional processes "attach them to the surface," while buried resistors and capacitors are "hidden inside"—a difference of one word, but a qualitative leap.

What are the core advantages of this "stealth technology"?

The advantages of buried resistors and capacitors (BRCs) technology, which has become a standard feature in high-end electronic products, are numerous, each addressing a key pain point in high-end circuit design:

• 1. Space Saving! Achieving "Ultra-Compact" Circuit Boards: With resistors and capacitors hidden inside, the PCB surface no longer needs to be densely packed with surface-mount components, directly freeing up significant board space. This allows engineers to design more complex circuits on smaller boards, which is one of the core reasons why mobile phones and smartwatches can become smaller and smaller.
• 2. Noise Reduction! More Stable Circuit Operation: Surface-mount components are susceptible to electromagnetic interference, generating circuit noise and affecting device performance. However, buried resistors and capacitors, encased in the PCB material, act like an extra "protective shield," significantly reducing electromagnetic interference and making the circuit more stable, maximizing anti-interference capabilities.
• 3. Improved Performance! Smoother Signal Transmission: Buried resistors and capacitors shorten signal transmission paths, reducing signal transmission delay and reflection loss, greatly improving the integrity and reliability of signal transmission. This is especially important for products with extremely high signal requirements, such as mobile phones, base stations, and high-end industrial control equipment.
• 4. Reduced Thickness! Achieving "Thinness" in equipment eliminates the need for surface-mount components, directly reducing the thickness of the PCB board. Combined with specialized materials such as ultra-thin embedded capacitor core boards, the entire circuit board becomes thinner and lighter, perfectly matching the current trend towards thinner and lighter electronic products.

Hiding components is far from simple.

Buried resistors and capacitors are not just about "stuffing" them in; it's a precise manufacturing process with four steps, each with strict requirements:

• Step 1: Creating a Dedicated Internal Layer In addition to the standard outer and inner layers of a PCB, a separate internal layer is created for embedding resistors and capacitors. This layer reserves space for embedding the resistors and capacitors and utilizes conventional PCB manufacturing techniques such as electroplating and etching to ensure layer precision.
• Step 2: Special Component Packaging Ordinary resistors and capacitors cannot be directly embedded. They need to be made into thin, special packages that not only fit the PCB thickness but also have good thermal conductivity to prevent performance issues caused by heat dissipation during operation.
• Step 3: Precise Component Embedding This is the core step, primarily using two methods: either a special pressing technique is used to press the packaged resistors and capacitors between the inner layer materials; or laser technology is used to etch cavities into the inner layer material before precisely filling the components. The entire process requires extremely high precision.
• Step 4: Layer Connection and Integration. The internal layers containing the embedded components must be connected to other conventional layers of the PCB using lamination, drilling, and other techniques to form a complete circuit board, ensuring smooth conductivity between layers.

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While the advantages are significant, it's also important to understand the drawbacks. The embedded resistor and capacitor process, while excellent, is not a panacea. Its main drawbacks are concentrated in two areas, which is why it's currently only used in high-end products:

• Complex Manufacturing and Repair: Resistors and capacitors are hidden internally and cannot be directly observed. If a problem occurs, they cannot be directly replaced like surface-mount components, making repair difficult and potentially leading to the scrapping of the entire board;
• Relatively High Cost: Special packaging, precise embedding processes, and specialized materials make the manufacturing cost of embedded resistor and capacitor boards higher than traditional PCBs.

Therefore, this process is currently mainly used in high-end electronic products with high requirements for performance, size, and thickness, such as flagship mobile phones, high-end servers, precision industrial control equipment, and aerospace electronic components.

Summary: The "Spatial Magic" of High-End Electronics – Limitless Future Potential

Ultimately, PCB buried resistor and capacitor technology is a high-end technology born for high-density, high-performance, and thin circuit designs. By "burying" resistors and capacitors internally, it solves the pain points of traditional surface mount technology, such as space constraints, interference, and thickness, becoming a key driver for the miniaturization and high-end development of electronic products.

With continuous technological advancements, the manufacturing cost of buried resistor and capacitor technology will gradually decrease, and the process precision will continue to improve. In the future, it may expand from high-end products to more consumer applications, enabling more electronic products to achieve breakthroughs in "small size, high performance."