Enhanced Signal Integrity: The use of blind and buried vias brings components closer together, shortening the length of signal paths. This improves signal quality and reduces EMI.
PCB manufacturing for hdi circuit board requires different production methods due to its small line widths. The conductive layers are thinner than standard PCBs, requiring careful design to ensure impedance matching and avoiding signal interference.
High-Density Interconnection
The high-density interconnection (HDI) circuit board contains more components within a smaller area than other types of PCBs. This allows you to create thinner, lighter devices that run faster and longer with greater reliability. The higher density also decreases the chance of signal reflections, which can interfere with performance and cause erratic behavior.
In addition to a thin core, HDI circuit boards use specialized dielectric materials that handle high heat levels from the traces and components. They also have a special prepreg layer that separates and isolates the conductive tracks from each other to reduce electrical interference and prevent charge buildup. The prepreg layer is also thick enough to resist the expansion that occurs when a circuit board gets hot.
The layered structure of a HDI circuit board includes both blind and buried vias, both of which hdi circuit board link layers to each other. These vias can be drilled mechanically or by laser depending on the diameter needed, and are filled with either a conductive paste or an anisotropic material.
HDI circuit boards can support more complex, higher-frequency designs than conventional circuits because they have lower thermal and electrical losses. This enables them to operate under extreme environmental conditions and withstand high levels of vibration, making them ideal for mobile phones and other consumer devices that need high-speed operation. They can also support IoT equipment used in manufacturing, warehousing and other industrial settings, such as smart sensors that monitor and control machinery.
High-Speed Signal Transmission
A high-speed PCB supports fast data transmission, which is required in many electronic devices and systems like telecommunications equipment and high-performance computers. Unlike traditional PCBs, high-speed circuit boards must have adequate termination schemes and attenuation control to maintain signal integrity. This requires careful planning of the layout.
High-speed signals travel over traces and have faster rise and fall times than their waveforms, which can cause interference or signal reflections. In order to mitigate these issues, designers must use techniques like proper termination schemes, attenuation control, EMI suppression, and power integrity control.
Impedance matching refers to the process of matching the characteristic impedance of a PCB track with the impedance of its source and receiver components. This prevents signal degradation due to unwanted reflections.
Other techniques for preserving signal integrity include avoiding crosstalk between traces through the use of low-dielectric materials, solid ground planes, and minimizing parallel run lengths. In addition, orthogonal routing and consideration of differential and clock routing can also reduce signal interference.
Finally, proper power distribution is essential for high-speed PCBs. This includes using large power and ground planes, placing them on the same hdi circuit board design layer as critical ICs, ensuring enough decoupling capacitance between the ground and power lines, and designing an appropriate power supply voltage regulation. This helps in preventing voltage droops, noise, and other power-related problems.
Minimal Crosstalk
High-speed digital signals can generate crosstalk between adjacent traces that degrade signal quality. This phenomenon is known as electromagnetic interference (EMI) and electromagnetic compatibility (EMC), and it can be minimized by shielding circuits, keeping traces as far apart as possible, using differential signaling, and using a solid ground plane.
As a PCB designer, you can also use various tools and techniques to detect and analyze crosstalk, such as oscilloscopes and eye diagrams. The simplest way to reduce crosstalk is through spacing, which is one of the few design parameters that a PCB designer has control over. The closer a pair of traces are, the higher the likelihood of coupling due to fringe electric and magnetic fields that induce currents in the aggressor trace that are not equal in amplitude and opposite in phase with the victim.
Fortunately, you have a powerful ally in the form of functionality built into most PCB design software. Using layer rules and net class rules, you can set your designs up to avoid broadside coupling by specifying routing directions and creating microstrip stackups. Also, you can use the 3W spacing rule to ensure that you have enough clearance between traces that carry high-speed signals. The result will be less crosstalk between the pairs of traces, and you’ll get the performance and reliability that your PCBs need to perform at their best.
Lower Parasitic Loads
The capacitance created between conductors that run in close proximity is known as parasitic capacitance. It stores a charge per unit change in electric potential and can induce crosstalk or interference between different signals in a circuit. It’s a common phenomenon in all electrical circuits.
High-speed digital applications require impedance matching of signal lines to limit reflections. Any mismatch causes jitter and bit error rates to increase. In order to avoid this, it’s important to design a PCB with the right layer stack and thickness. Using a CAD tool with an embedded 3D field solver can help you calculate the effects of layers, layer stacks and copper width on impedance matching.
Sierra Circuits’ Transmission Line Reflection Calculator makes it easy to see the effect of a change in impedance on signal reflections and ringing. The calculation also lets you determine the right layer stack for your project.
The layer stack for HDI PCBs can be designed to reduce parasitic inductance. A 3-D lattice structure is used to generate vertical magnetic flux cancellation between adjacent layers and horizontal magnetic flux cancellation between segments within a layer. This structure allows for the optimization of the PCB’s power loop current path and a reduction in parasitic inductance.
The top and bottom layers for an HDI PCB can be routed to minimize inductance, especially with the use of buried vias. A buried via is an electroplated hole that’s located inside the layer of the PCB and can only be accessed through a drill file.
