HDI PCB Design Tips
The demand for smaller, lighter, and faster products pushes manufacturers to pack more parts into a compact space. This creates the need for high-density circuit boards.
One central feature of HDI PCBs is microvias, which must be designed precisely to accommodate routing density between layers. They are sized using the interface and direction counter from the largest BGA component on the board.
Type I Stackups
Choosing an appropriate PCB stack-up is crucial to ensure that the layout can meet performance requirements, such as signal routing distance. The right layer arrangement can also save you money in production by reducing the number of vias and materials required. Additionally, proper placement of ground and power planes can minimize electromagnetic interference (EMI) emissions.
Stackup design is a complex process, but one that is vital for the success of your product. Using an advanced design tool can help you determine the best layer stack for your product. These tools allow you to model your circuit board and perform simulations, ensuring that the layout will work properly. They can even suggest a good starting point for your layer stack.
Another factor to consider when selecting a stackup is the manufacturing capabilities of your chosen fabricator. Some high-density stackups require specialized equipment and materials to fabricate, which can increase the cost of your project.
The most common type of stackup is the 2+N+2 stackup, which consists of two sequential laminations. This type of stack-up can be used for small boards and is ideal for a wide range of applications. Its copper layers can be connected to each other using blind and buried vias, which improve the circuit board’s electrical performance. However, it can be difficult to use this stack-up with a dense layout because it requires the layer count to be high.
Type II Stackups
In the case of high-speed circuits, it is important to avoid overcrowding components and using high-powered devices near the edges of a layer. This will prevent electrostatic interference and increase signal integrity. The thickness of a layer should also be considered, as it will affect the signal transmission speed and mechanical strength of the board. Ensure that the material types used in prepregs and cores are well matched. Dielectric constant mismatches can cause signal loss and thermal expansion issues.
This type of stackup is a good option hdi pcb design for a wide range of applications, from consumer electronics to industrial machinery and aerospace technology. Its versatility makes it a valuable addition to the manufacturing process. It has been found to reduce the time needed for lamination and improve production efficiency.
Another option is the 2+N+2 stackup, which consists of two sequential build-up layers. This allows you to use more copper layers in the design and gives you a greater flexibility in the routing of signals. It also reduces the number of vias and allows for greater layer density.
Another option is the i+N+2 stackup, which can be made with either an over-core or coreless structure. It is more complex than a standard PCB, but it offers many benefits, including buried vias and a greater level of performance. It also has the advantage of reducing the amount of time required for lamination and assembly, as it requires only one lamination cycle.
Materials
HDI PCBs require a high-density design, and the choice of materials plays a key role. It is important to choose materials that can withstand a high-speed environment and provide a good balance between electrical performance and cost. These materials also need to be compatible with the fabrication process, as well as be able to tolerate thermal and mechanical stresses.
When choosing HDI material, look for materials that have a low loss and good signal integrity. You can also use materials that are resistant to electromagnetic interference, a key consideration in high-speed applications. Avoid close spacing or crowding of components, as this can lead to stress on the board and a greater chance of failure.
The layer stackup is another essential factor in the design of an HDI circuit board. The choice of layers, thicknesses and the types of materials used impact manufacturing costs and the ability to drill holes. The choice of vias, whether blind, buried or microvias, is also a crucial decision. The choice of these factors can significantly affect the overall performance capacity of an HDI circuit board.
The layer stackup in a HDI circuit board depends on HDI PCB Design Supplier the fabricator. The board manufacturer must be able to perform a thorough reliability assessment of the materials, and determine the number of sequential laminations required. It is also crucial to decide on the via structure type, such as laser drilled or via in pad.
Via Type
For multilayer HDI PCBs, proper via design is crucial for high-density routing and signal transmission. The type and location of vias can affect both the cost and performance of your board. The via type you choose will depend on your fabricator’s capabilities, the number of layers in your project, and the size of the underlying pads. For this reason, you should always check with your fabricator before choosing a via type.
The most common type of via is the standard through-hole, which is mechanically drilled and plated. It connects all of the layer to layer connections on a multilayer hdi stackup. This is the most economical option, but it does not provide a good return path for high-speed signals. To avoid this problem, you should use a microvia.
Another type of via is the blind, which is laser-drilled and plated. It is suitable for boards up to 1.6mm in thickness. Its smaller finished hole and annular ring make it less likely to suck away copper from additional layers. It is also more space consuming than a microvia.
Another type of via is the buried, which is a laser-drilled hole that is covered by additional layers of the PCB. It is sometimes called the filled and capped via (VIPPO). When this type of via is used, it is important to ensure that the fabrication notes specify that the via hole needs to be filled and capped.