The HDI multi-layer PCB design is suitable for large boards and high connections per square inch. But if your board is small and you do not need a high number of connections, a conventional multi-layer PCB design is fine. In addition, we can enhance a traditional PCB of multi-layer design with laser drilling. However, this process is more expensive.
2+N+2 HDI multi-layer PCB
A 2+N+2 HDI multi-layer PCB is a multi-layer PCB with a minimum of two high-density interconnection layers and buried vias. Its construction is similar to conventional PCBs, except that the material used for each layer is different. The most common materials are resin-coated copper, metalized polyimide, pure polyimide, and cast polyimide. Other materials include FR4 laminate and PTFE.
The 2+N+2 HDI multi-layer PCB is a Type III construction that uses two sequential layers of high-density interconnects. Each layer can interconnect with any other layer, which allows for a higher routing density. This method also keeps the finished board thin and allows for smaller ball pitch components.
HDI PCBs are ideal for a variety of complex electronic devices. They often use touch-screen devices, mobile phones, laptop computers, and digital cameras. Additionally, they are helpful in 4/5G network communications and military applications. In addition, their flexibility allows for smaller and more efficient boards.
HDI PCBs have many benefits, including a small surface area, high frequency, and increased strength. These advantages, combined with a smaller size, make HDI PCBs valuable for hi-tech devices. HDI PCBs are also more energy-efficient than traditional PCBs because they use fewer layers and raw materials. As a result, a single HDI multi-layer PCB can replace several traditional PCBs.
HDI PCBs can replace heavy wiring in many advanced electronic devices. The smaller size and weight of HDI PCBs make them an excellent choice for space-constrained products. The thinner size and lighter weight of HDI PCBs allow the inclusion of many transistors. They also feature a stable voltage rail and minimal stubs. This helps improve signal integrity.
Resin-coated-copper
Resin-coated copper is a versatile material for circuit boards. Its advantages include a uniform thickness, high insulation, and low dielectric loss. It also has excellent heat and chemical resistance. Another benefit is that we can make it into precise circuits with higher densities.
RCC is a hybrid material that combines uncured B-stage resin with copper foil. It also has a unique dielectric property and allows for a balance between dielectric thickness and circuitry filling. This material is more expensive than prepreg or copper foil, but improved laser drill throughput can offset the additional cost.
To make a PCB with a resin-coated copper layer, the copper foil has a polyimide and halogen-free resin layer. The two layers are then placed in a press and exposed to high pressure. The temperatures required are 340degF (170degC), and 1500psi for an hour.
Resin-coated copper is the most popular type of copper-based multi-layer PCB material. It has higher electrical and thermal conductivity than traditional copper-based PCBs. Moreover, we can use it for many applications, including automotive and consumer electronics. A multi-layer PCB features two patterned layers.
Resin-coated-copper multilayered PCBs can include embedded chips. This technology allows manufacturers to control and tune the lamination process to fit the product’s requirements. It can also replace spin-coating processes. We can also fabricate it in three-dimensional packages.
Resin-coated-copper multi-layer PCBs consist of copper-clad board stock. This material has different additives for improved thermal and electrical properties during manufacturing. In addition, a base epoxy resin helps to create these PCBs.
Laser micro vias
The formation of microvias using laser drilling is crucial for forming high-density interconnect PCBs. This new technology can create a finer hole diameter than traditional mechanical drilling techniques. In addition, HDI boards are highly compact and reliable, thanks to their ability to accommodate high pin density components.
HDI PCBs have advantages over conventional multi-layer boards, including superior thermal dissipation and a greater current load. These boards also feature flat pads, which make it easier to weld modern-generation components. To create high-quality HDI boards, laser holes must be free of glass fibers and have a diameter between 80 and 100um. This process also requires high-precision drilling.
Laser drilling eliminates the disadvantages of mechanical drilling and makes it possible to create high-quality microvias on HDI multi-layer PCBs. Laser drilling uses a beam of light instead of a conductor to avoid contamination of the PCB board or wear of the drilling part.
Microvias are often helpful for High-Density Interconnect structures (HDI). Microvias significantly improve circuit performance while saving wiring space. This technology can also produce via-in-pads, reducing the need for additional wiring. The equivalent impedance of a via is 12% lower than the transmission line. This translates to a significant reduction in signal reflection.
Microvias can be stacked, staggered, or individual. Each method involves different process steps. For example, staggered microvias form an interlayer connection between two or three conductive layers.
Flexibility
We can produce HDI multi-layer PCBs in a variety of ways. For example, they can often have a single or double dielectric layer with one or more layers of flexible conductive material. The dielectric layer is usually made of highly purified electrolytic copper but can also be an acrylic or fiberglass material. A layer of polyimide, known as a PI layer, insulates the conductive layers. The PI layer is similar to the solder mask in a conventional PCB.
The HDI PCB is an excellent choice for devices requiring a high degree of flexibility. Among its many benefits, it offers better signal integrity and allows the use of smaller components on smaller boards. It also offers simplified circuit routes, thanks to its buried and blind microvias. In addition, HDI PCBs are ideal for IoT devices, thanks to their small size and increased channel routing width.
HDI multi-layer PCBs are extremely flexible and have high-performance levels. In addition, placing more components on the same raw PCB and reducing the size of the components can help designers get more I/O in smaller geometries. This decreases signal loss and reduces crossing delays.
HDI PCBs have a sequential lamination process that enables them to have high-density interconnections. This process can produce all multi-layer PCBs. The HDI process requires multiple steps that ensure the highest possible level of reliability. This allows HDI multi-layer PCBs to withstand repeated mechanical and thermal shocks.
Flexible PCBs also reduce the weight of an application. Since they come from the thinnest substrates, they can minimize the weight of an application by nearly 95 percent.
Cost
The cost of HDI multi-layer PCBs is affected by many factors. The type of PCB you are producing, the size of the vias, and the number of layers all impact the cost. Smaller vias are more expensive than larger ones, and adding more vias will increase the price. Additionally, the number of layers and stackup height will affect the cost. For instance, the cost of producing a ten-layer board that uses a build-up structure will be higher than that of a five-core 4-Z interconnect structure. Furthermore, the more layers you use, the higher the cost of your HDI PCB.
The costs of HDI PCBs also largely depend on the materials’ quality. For example, when manufacturing HDI parts, it is essential to use semiconductor Class 100 clean rooms. A clean room atmosphere reduces defects. In addition, high-quality photo tools and laminate prep are essential to a successful process.
The size of the PCB is another essential factor. Some PCBs are extremely small, while others require a larger size. The size of your PCB will affect its cost as well. For some applications, a small PCB will cost less than one that requires a larger size. However, tiny PCBs will also require more outline routing paths, resulting in higher labor costs.
HDI PCBs are ideal for many devices that need to withstand harsh environments. For example, these boards can be helpful in VR headsets, which can use large amounts of current. Another important use of HDI PCBs is in the automotive industry. Vehicles with HDI PCBs contain about 50 microprocessors that control the vehicle’s engine, diagnostics, and safety features.