PCB Materials

Resin Coated Copper (RCC)

Discover the importance of Resin Coated Copper (RCC) in HDI PCB manufacturing and how it can improve stability, reliability, and reduce costs.

What is Resin Coated Copper?

Resin Coated Copper (RCC) is a material used in the production of high-density interconnection circuit boards, which provides the ability to create small holes and fine circuitry. RCC combines a layer of uncured B-stage resin with a layer of copper foil, which makes it a unique dielectric material for building multilayer circuitry, particularly in HDI printed circuit boards. This material is crucial for HDI PCB manufacturing, as it replaces traditional bonding sheets and copper foils, serving as both an insulating medium and conducting layer. RCC is used in non-mechanical drilling methods such as laser, allowing for micro-via interconnect formation. Additionally, RCC materials are compatible with conventional PCB fabrication processes such as layup, lamination, and DES, and are amenable to mass blind microvia formation methodologies. RCC’s ability to meet the specific requirements of high-density circuit board production has made it a vital material in the industry.

What is HDI PCB?

HDI PCB stands for High-Density Interconnect Printed Circuit Board. It is a type of circuit board that is designed with dense and complex structures, consisting of multiple layers of copper and different materials such as resin coated copper, ceramic, or FR-4, which provide distinctive electrical and mechanical properties. HDI PCBs often have blind vias, buried vias, and microvias that allow the traces to be routed to different layers, reducing the size of the board and increasing the routing density. HDI PCBs are widely used in smartphones, tablets, laptops, cameras, medical equipment, and other electronic devices due to their high performance and compact size.

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Function and application of Resin Coated Copper

Resin Coated Copper is widely used in the electronics industry as a dielectric material for building multilayer circuitry, particularly in HDI PCBs. Its main function is to provide a reliable and stable insulation layer between the conductive layers of the PCB, ensuring that the electrical signals transmitted through the board are not disrupted or disturbed.

RCC is an ideal choice for high-density circuit board production as it is highly compatible with conventional fabrication processes, such as layup and lamination, and can be easily incorporated into the PCB production process. It also offers several advantages, such as low dielectric constant, low loss tangent, and excellent thermal stability, which make it a preferred choice for high-speed and high-frequency applications.

Some of the common applications of RCC include smartphones, tablets, laptops, servers, aerospace, medical equipment, automotive electronics, and other electronic devices that require high-speed data transfer and reliable signal integrity. RCC has become an indispensable material in the electronics industry due to its unique properties and its ability to meet the specific requirements of high-density circuit board production.

Composition of Resin Coated Copper

Resin Coated Copper is a composite material that consists of two main components – copper foil and resin.

Copper Foil

Copper foil is the foundation of RCC, and its properties directly influence the final performance of RCC. Copper foils can have different thicknesses, textures, and surface roughness. The most commonly used thicknesses for RCC are 18µm and 35µm. The texture of copper foil can be either smooth or treated with an etching process to produce a rough surface. A rough copper foil texture can enhance the adhesion of resin to copper, which is essential for RCC to function properly.

Resin

Resin, the other essential component of RCC, is a thermosetting polymer that provides mechanical and chemical stability to the circuit board. There are different types of resins that can be used in the production of RCC, including epoxy, phenolic, and polyimide. Epoxy resins are commonly used due to their low cost and easy availability. Phenolic and polyimide resins are more expensive but have superior thermal and mechanical properties. These resins can also be modified with various additives to improve their specific properties.

The Manufacturing Process of RCC

The manufacturing process for RCC involves a series of steps that begin with the preparation of copper foil. The copper foil is first cleaned and treated with a chemical process to produce a rough surface texture. Then, the resin is applied to the surface of the copper foil, typically using a roller or a spray method. The coated copper foil is then subjected to a curing process, during which the resin undergoes a cross-linking reaction to form a stable and rigid matrix. Finally, the RCC is trimmed and cut to the desired size, ready for use in circuit boards.

The properties and advantages of Resin Coated Copper

RCC’s properties make it an excellent choice for HDI PCB manufacturing, and its advantages can contribute to the improvement of the overall performance of electronic devices while also reducing manufacturing costs.

a) Properties:

Corrosion resistance: RCC has excellent corrosion resistance, making it ideal for use in HDI PCB manufacturing where moisture and other environmental factors can cause damage.
Good electrical conductivity: RCC has good electrical conductivity, which helps ensure reliable signal transmission in HDI PCBs.
Strong malleability: RCC is highly malleable, meaning it can be easily formed into a variety of shapes and sizes during the manufacturing process.
Wear resistance: RCC has strong wear resistance, which helps ensure the longevity and durability of HDI PCBs.

b) Advantages:

Improves stability and reliability of HDI PCBs: RCC’s excellent corrosion resistance and electrical conductivity help improve the stability and reliability of HDI PCBs, making them less prone to damage or failure.
Reduces latency and resistance: RCC’s good electrical conductivity helps reduce the latency and resistance of HDI PCBs, allowing for faster and more reliable signal transmissions.
Lowers manufacturing costs: RCC’s strong malleability and wear resistance make it a cost-effective material for HDI PCB manufacturing, helping to reduce overall production costs.

Origin and Development of RCC for HDI Microvias

The origin of RCC for high density interconnect microvias can be traced back to the need for increased board density and faster processing speeds. By reducing layer counts and utilizing blind and buried vias with lower capacitance, electrical signals can travel faster between devices. Resin coated copper, or RCC, offers a new material solution for constructing large numbers of blind vias in an economical manner. This is because the all resin construction of RCC enables the creation of ultra-small microvias, which can be as small as 6 mil, and reduces the line and space circuit features in order to achieve greater circuit density. In addition, some microvias formation techniques, such as laser ablation, allow for mass hole formation.

Microvia formation using laser ablation technique

Laser ablation is a microvia forming technique that utilizes directed laser beams to break down copper and dielectric on nonreinforced dielectrics, particularly for microvias with diameters equal to or less than 6mil (0.15mm), 5mil (0.12mm), 4mil (0.1mm), and 3mil (0.075mm). While conventional drilling is impeded by fiberglass, laser ablation has the advantage of being faster and reducing consumable costs. However, the use of laser ablation may also result in the outer layer copper being ablated with the dielectric layer, including low flow PP and polyimide. Although RCC is expensive, many HDI PCB fabricators replace it with 106 PP and copper foil when making HDI boards.

What is the optimal microvia diameter for laser drilling on RCC?

When designing a board with blind microvias and needing the via-in-pad treatment process, selecting the best microvia diameters is important to improve laser drilling efficiency. It is also best to use the same diameter microvias. If the microvia diameter is small, the copper deposition and plating onto the microvia walls will be poor, resulting in a poor copper cap to form planarized pads (large dimple). On the other hand, if the microvia diameter is large, the copper deposition and plating onto the microvia walls will be good, resulting in a good copper cap to form planarized pads (OK dimple). Based on years of experience in laser drilling RCC and “copper + 106 PP”, a 4mil microvia diameter is always the ideal choice for HDI boards, even if the board requires ultra-fine pitch PoP component soldering.

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FAQs on Resin Coated Copper

What is resin coated copper (RCC)?

Resin coated copper, or RCC, is a type of copper foil free from glass fiber coated on one or both sides with a thermosetting resin. This coating provides several advantages, including increased durability, improved adhesion to other materials, and enhanced resistance to corrosion and humidity.

What is the thickness of the RCC?

The Resin copper foil thickness is generally 18μm 12μm, or even 8.75μm, which is easy to process.

What are the features of RCC?

a) free of glass dielectric layer, easy to form by laser and plasma microhole.

b) thin dielectric layer.

c) extremely high peel strength.

d) high toughness and easy to operate.

e) smooth surface, suitable for micro-narrow line etching.

What are the advantages of using RCC in HDI PCB manufacturing?

Using RCC in HDI PCB manufacturing offers several key advantages, including increased reliability and stability, reduced delay times and resistances, and lower manufacturing costs. RCC's enhanced durability and resistance to corrosion also make it an ideal option for use in high-performance applications.

What are some common applications for RCC in PCB manufacturing?

RCC is commonly used in a range of PCB manufacturing applications, including in high-speed digital, microwave, and RF circuits, as well as in automotive, aerospace, and military applications. RCC is also commonly used in applications where high reliability and durability are essential.