HDI PCB design guidelines

Among the three above, the last is especially suitable for High Density Interconnect PCB (HDI PCB). Hemeixin Electronics Co.,Ltd., eminent HDI PCB manufacturer,recommends using lamination buildup with microvias for HDI printed circuit boards that have high pin-count Ball Grid Arrays (BGA) and other fine-pitch packages, as each type has its own advantages and disadvantages.

For instance, standard lamination with through vias may be low cost for 28 layers and below, but is very difficult to route when multiple BGAs with over 1500 pins and less than 0.8 mm pitch are involved. Likewise, sequential lamination with blind and buried vias have potentially shorter via stubs and fairly simple via models, with smaller via diameters than those required for through hole vias. Costing more than the standard lamination with through vias, sequentially laminated boards maintain the same minimum trace widths and their practical reliability limits their number of layers to a maximum of two or three.

Above limitations and more are leading to a larger number of HDI PCB manufacturers moving towards building up laminations with microvias and other advanced features for HDI PCBs. Advantages of the microvia HDI PCB design include achieving very high route density with fewer layers, as the traces and vias have much smaller dimensions comparatively. In microvia HDI PCBs, the potential for a lower number of layers comes from the effective use of patterns with microvias, as this opens up more space for routing, providing the only applicable way of designing with several large, fine-pitch BGAs with pitch measuring 0.8 mm or lower.

Offering the lowest cost for high frequency, high-density boards, HDI technology, with suitable stackup definition, also improves power and signal integrity in high frequency PCBs. Although typical materials fabricators use for HDI PCBs do well in processes requiring RoHS, use of newer materials has the potential of higher performance with the lowest costs. Notably, these newer materials are not suitable for fabrication of boards using standard or sequential lamination.

HDI is one of the more complex pcb board fabrication processes we specialize in. We use SBU technology, which allows sequential addition of more pairs of layers to form a multilayer core, to create this type of highly integrated PCB.

SBU pcb is a multilayer technology that can be achieved by putting a dielectric element and a copper foil on both top and bottom of the core before it is submitted to laser drilling, image transferring, and etching processes. Multilayer PCBs designed through this technological procedure are marked by a sequence of numbers and Ns, (e.g., 1+N+1, 2+N+2, etc.), where N represents the number of layers that form the core and the numerical values represent the number of layers added.

To provide modern PCB designers with a review of robust rules and methods that will allow them to design a highly reliable printed circuit board with the lowest cost, most commonly used features, and least number of manufacturing issues (that may result in a no-bid, engineering questions, placing the job on hold, or negatively impact the final yield).

High Density Interconnect (HDI) circuit board designs have a higher wiring and pad density than conventional PCBs, along with smaller trace widths and spaces. They require advanced PCB technologies such as blind vias, buried vias, and microvias. HDI PCBs are usually more costly than conventional PCBs due to the complex build-up process involved in fabrication.

Here we only wish to provide the minimums that if adhered to will provide the designer with a highly reliable physical PCB.

Below guildelines including these contents for Blind Vias, Buried Vias & Microvias pcb;

1. Footprint Design Assistance
2. HDI Microvia Standard Design Rules
3. HDI Microvia Types definition
4. Cost of MicroVia HDI pcb Types
5. Plated Through High Aspect Ratio
6. lamination cycles up to 6 times for Stacked Microvia

See also: How to BGA Fanout Routing in your HDI PCB