What is the difference between HDI and non HDI PCB?

What is an HDI PCB?

An HDI PCB is a printed circuit board that features a higher density of interconnects than traditional PCBs. This is achieved through the use of smaller vias, finer trace widths, and smaller spacing between traces. HDI PCBs can have multiple layers, with some designs incorporating up to 16 or more layers. The higher density of interconnects allows for more complex circuits to be designed in a smaller space, making HDI PCBs ideal for applications that require miniaturization and high performance.

Key features of HDI PCBs:

  • Smaller vias (microvias) with diameters less than 150 microns
  • Finer trace widths and spacing, typically less than 100 microns
  • Higher layer count, often 8 or more layers
  • Buried and blind vias for increased interconnect density
  • Sequential lamination process for fabrication

What is a non-HDI PCB?

A non-HDI PCB, also known as a traditional or standard PCB, is a printed circuit board that uses larger vias, wider traces, and more space between traces compared to HDI PCBs. Non-HDI PCBs typically have fewer layers, ranging from 1 to 4 layers, although some designs may have up to 6 layers. These PCBs are easier and less expensive to manufacture than HDI PCBs, making them suitable for applications that do not require high density or complex functionality.

Key features of non-HDI PCBs:

  • Larger vias with diameters greater than 150 microns
  • Wider trace widths and spacing, typically greater than 100 microns
  • Lower layer count, usually 1 to 4 layers
  • Through-hole vias that span the entire thickness of the board
  • Single lamination process for fabrication

Differences between HDI and non-HDI PCBs

1. Interconnect Density

One of the primary differences between HDI and non-HDI PCBs is the interconnect density. HDI PCBs have a much higher density of interconnects, allowing for more complex circuits to be designed in a smaller space. This is achieved through the use of smaller vias (microvias), finer trace widths, and tighter spacing between traces.

Feature HDI PCB Non-HDI PCB
Via Diameter < 150 microns > 150 microns
Trace Width and Spacing < 100 microns > 100 microns

2. Layer Count

HDI PCBs typically have a higher layer count than non-HDI PCBs. This allows for more complex routing and increased functionality in a smaller form factor. HDI PCBs can have 8 or more layers, while non-HDI PCBs usually have 1 to 4 layers, with some designs having up to 6 layers.

PCB Type Typical Layer Count
HDI PCB 8 or more layers
Non-HDI PCB 1 to 4 layers

3. Via Types

HDI PCBs use buried and blind vias to increase interconnect density and reduce the overall size of the board. Buried vias connect inner layers without penetrating the top or bottom layers, while blind vias connect an outer layer to an inner layer without penetrating through the entire board. Non-HDI PCBs primarily use through-hole vias, which span the entire thickness of the board.

Via Type HDI PCB Non-HDI PCB
Through-hole Used Primary
Buried Used Rarely used
Blind Used Rarely used

4. Manufacturing Process

The manufacturing process for HDI PCBs is more complex and involves sequential lamination, where layers are added one at a time with microvias drilled and filled between each lamination step. This process allows for the creation of buried and blind vias, as well as the high interconnect density characteristic of HDI PCBs.

Non-HDI PCBs are manufactured using a single lamination process, where all layers are laminated together at once. This process is simpler and less expensive than the sequential lamination used for HDI PCBs.

5. Cost

Due to the complex manufacturing process and higher interconnect density, HDI PCBs are generally more expensive than non-HDI PCBs. The cost difference can be significant, especially for smaller production runs. However, the increased functionality and miniaturization offered by HDI PCBs can justify the higher cost in applications where these features are necessary.

Applications of HDI and non-HDI PCBs

HDI PCB Applications

  • Smartphones and tablets
  • Wearable devices
  • Medical devices
  • Aerospace and defense systems
  • High-performance computing
  • Miniaturized IoT devices

Non-HDI PCB Applications

  • Consumer electronics
  • Industrial control systems
  • Automotive electronics
  • Power supplies
  • LED lighting
  • Home appliances

Factors to Consider When Choosing Between HDI and non-HDI PCBs

When deciding between HDI and non-HDI PCBs for your project, consider the following factors:

  1. Size and Complexity: If your design requires a small form factor and high component density, an HDI PCB may be the better choice. However, if your design is simpler and does not require miniaturization, a non-HDI PCB may suffice.

  2. Cost: HDI PCBs are generally more expensive than non-HDI PCBs due to the complex manufacturing process and higher interconnect density. Consider your budget and the trade-offs between cost and performance when making your decision.

  3. Performance Requirements: If your application demands high performance, such as in aerospace, defense, or medical devices, an HDI PCB may be necessary to meet the required specifications.

  4. Production Volume: For large production runs, the cost difference between HDI and non-HDI PCBs may be less significant. In these cases, the benefits of HDI PCBs, such as miniaturization and increased functionality, may outweigh the additional cost.

  5. Design Expertise: Designing HDI PCBs requires specialized knowledge and experience. If your team lacks HDI design expertise, it may be more practical to opt for a non-HDI PCB or to work with a design service provider that has experience with HDI PCB design.

FAQ

  1. Q: Can I convert a non-HDI PCB design to an HDI PCB?
    A: Yes, it is possible to convert a non-HDI PCB design to an HDI PCB. However, this process may require significant changes to the layout, component placement, and routing. It is essential to work with an experienced HDI PCB design team to ensure a successful conversion.

  2. Q: Are HDI PCBs more reliable than non-HDI PCBs?
    A: When designed and manufactured correctly, HDI PCBs can be just as reliable as non-HDI PCBs. However, the increased complexity of HDI PCBs can make them more susceptible to manufacturing defects, so it is crucial to work with a reputable manufacturer with experience in producing high-quality HDI PCBs.

  3. Q: Can I mix HDI and non-HDI layers in the same PCB?
    A: Yes, it is possible to mix HDI and non-HDI layers in the same PCB. This is known as a hybrid HDI PCB design. Hybrid designs can offer a balance between the benefits of HDI and the cost savings of non-HDI layers. However, designing hybrid HDI PCBs requires careful planning and expertise to ensure proper signal integrity and manufacturability.

  4. Q: What is the minimum feature size for HDI PCBs?
    A: The minimum feature size for HDI PCBs depends on the manufacturer’s capabilities and the specific design requirements. Typically, HDI PCBs can have trace widths and spacing as small as 50 microns (2 mil) and microvia diameters as small as 75 microns (3 mil). However, some advanced HDI PCB manufacturers may be able to achieve even smaller feature sizes.

  5. Q: Are there any limitations to using HDI PCBs?
    A: While HDI PCBs offer many benefits, there are some limitations to consider. The main limitations include higher cost, increased design complexity, and potential signal integrity issues if not designed properly. Additionally, not all PCB manufacturers have the capability to produce HDI PCBs, so it is essential to choose a manufacturer with the necessary expertise and equipment.

In conclusion, understanding the differences between HDI and non-HDI PCBs is crucial when designing and manufacturing electronic devices. HDI PCBs offer higher interconnect density, smaller form factors, and increased functionality, making them ideal for applications that require miniaturization and high performance. However, they also come with higher costs and design complexity compared to non-HDI PCBs.

When deciding between HDI and non-HDI PCBs, consider factors such as size and complexity, cost, performance requirements, production volume, and design expertise. By carefully evaluating these factors and working with experienced PCB design and manufacturing partners, you can select the most appropriate type of PCB for your project, ensuring optimal performance, reliability, and cost-effectiveness.