HDI PCB Design
HDI PCB is a type of printed circuit board that enables designers to maximize components and signal interconnections in a small space. HDI PCBs require special design for manufacturability (DFM) techniques to ensure that the fabrication and assembly processes can accommodate them.
The choice of components and their placement is crucial for an efficient hdi pcb design. Careful routing minimizes SI effect and signal reflection, as well as impedance mismatches between signals and components.
Layering
PCBs with a high density of components and connections require multiple conductive layers to function. These layers need to be thin so that many can fit in a small area. These layers must be carefully designed to achieve impedance matching and prevent signal interference. They also need to be placed close together to minimize the distance that signals travel and reduce signal reflections. This technology is being used in a variety of advanced devices, including touch screen computing and compact, low-footprint gadgets. It is also being utilized in advanced military and telecommunications equipment.
These PCBs are typically made using a sequential lamination process. This allows for good control over the thickness of the finished product, reduces warping and breaking, and helps with the drilling and plating process. It also allows for the use of thinner dielectrics, which improve thermal management and reduce the amount of copper needed to make a circuit board.
There are six different types of HDI PCBs, which are divided into categories based on their stackup design. Type I has through-hole and blind vias on one or both sides of the substrate and core material, and has no buried vias. Type II has through-hole and stacked microvias, with some having buried vias that can be prefilled with conductive or non-conductive paste.
Type III has a passive substrate and may have through-hole and stacked microvias, and some with buried vias that can be partially or completely filled with the laminate’s dielectric material. Type IV has a coreless construction, and Type V has a build-up structure.
Vias
A key aspect of HDI PCB design is the use of vias, which are holes that connect layers. The size and depth of the vias determine the performance of high-speed signals. They should be smaller than traditional PCB traces, and their length should not exceed six mils. In addition, the diameter of the drilled holes should be small enough to fit the components being used in the circuit board.
Several types of vias are available for high-density PCBs. Some of them are blind and buried, while others are through-hole. Each type hdi pcb design has its own advantages and disadvantages. Choosing the right one is crucial, because it can affect the overall manufacturing cost.
For example, microvias are a good choice for HDI PCBs because they reduce the hdi pcb number of layers and help with BGA breakout. These microvias are drilled through the top and bottom layers of the board, then filled with copper using a process called SBU (sequential build up). They can also be used to improve signal integrity by eliminating ground planes and shortening trace lengths.
Another benefit of microvias is their ability to reduce manual routing time for complex projects. They can also be a good choice for high-speed designs, as they are less likely to introduce parasitic effects. They are also ideal for BGA breakouts because they allow for a direct connection from the component lead to an internal layer.
Components
The components used in HDI PCBs are smaller than those found on traditional circuit boards. This allows for a higher circuitry density, which results in a more powerful device. However, this technology requires more precision in the assembly process and a greater focus on component placement. It’s also important to separate analog and digital circuit sections to avoid interference. In addition, it’s crucial to place decoupling capacitors close to the circuit sections to help reduce noise.
The process of manufacturing HDI PCBs is also more complex than traditional ones. It requires more sophisticated photo tools, laminate prep, and imaging parameters. In addition, it requires a semiconductor class 100 clean room for proper processing. This is necessary to prevent abrasions that can cause defects. In addition, the thinner traces and vias require more precise positioning than conventional PCBs.
The use of microvias instead of through holes in HDI PCBs improves signal integrity and provides a more reliable design. However, the smaller aspect ratio can also lead to problems with routing. To avoid this, designers need to take into account signal lengths, adequate planes in ground, and consistent path impedances. They also need to keep the via size in mind when designing high-speed signals. In addition, the traces should be short for better signal integrity. This will ensure that the signal can travel through the shortest path and minimize signal loss and crossing delays.
Layout
HDI PCBs are used in complex electronic devices that require compact circuit boards with high functionality. They support miniaturization, allow for higher performance, and provide better signal transmission due to shorter paths. They are also less susceptible to electromagnetic interference (EMI). They are the perfect solution for mobile / cellular phones, touch-screen devices, digital cameras, 4/5G network communications, and military applications like avionics and smart munitions.
The key to successful HDI design is to focus on the right DFM requirements. These include component placement, routing widths, via size, and BGA fanout. These requirements are critical to the overall success of the board, as mistakes can increase manufacturing costs and lengthen manufacturing times.
It is important to note that the component and trace layout is different for HDI PCBs. To achieve optimal results, the traces should be placed symmetrically on both sides of the board, and the components should be spaced correctly to avoid overheating. It is also important to consider the direction of components when placing them on the board, as this can help ensure error-free soldering during assembly.
Another aspect to consider when creating an HDI circuit board is the number of layers. The higher the number of layers, the more complicated the design will be. For this reason, it is vital to have an effective CAD tool that can support HDI design and manufacturing processes.