Pitch Routing in HDI Circuit Boards
Achieving fine pitch routing in HDI circuit boards requires careful planning of the board layer stackup, trace widths and spacing, and via size. It also involves using smaller components to allow for more space and higher routing density. These factors, when combined, can have a big impact on signal integrity and performance.
The first step in achieving fine pitch routing in hdi circuit board is to select the right materials and construction process. This can be accomplished by choosing core materials, like FR4, metal or fiberglass; surface finishes like HASL, immersion tin, immersion silver and gold; and via structure types. You should also choose the number of sequential laminations that your board will require. Although more laminations add cost, the benefits of a multi-layer PCB can help reduce thermal stress and warping during assembly and test.
Another important consideration in achieving fine pitch routing in HDI PCBs is to consider the design rules for these types of circuit boards. These rules are set by the manufacturer and may include limitations on via diameters, trace widths and spacing, and other factors that affect the performance of the circuit board.
Achieving Fine Pitch Routing in HDI Circuit Boards
It is recommended that you work closely with your PCB fabricator to ensure that the design meets fabrication requirements and to avoid potential delays in the manufacturing process. The manufacturer should also be able to guide you in choosing the right material for your circuit board. They can also advise you on which via structures to use and the best methods for incorporating them in your PCB layout.
Depending on your application, you may need to consider the use of multiple layers and buried and blind vias. These are used for high-speed signal connections between components and the power plane. They can also provide one of the shortest ways to bypass decoupling capacitors in high-frequency applications. In addition, these vias are easier to place than traditional through-hole pins and can reduce the overall number of layers in a circuit board.
To achieve fine pitch routing in HDI circuit boards, you should use a solid ground plane beneath and between high-speed signal layers to minimize crosstalk and maintain impedance control. You should also try to avoid routing traces over a split plane or a void in the reference plane to prevent degradation of the signals. If this is unavoidable, you should consider stitching capacitors to compensate for this degradation and improve signal integrity.
For buried and blind vias, you will need to use a multi-layer PCB with a special prepreg that is heated during the production process to liquify it. The PCB is then layered together, with the copper layers separated by the prepreg, and then cured. The layers are etched, and the vias are punched through both the surface and the underlying layers. The holes are filled with different fill types, capped and then plated over. The final result is a high-performance, fine-pitch PCB that can support the latest, high-speed components.