Why Use High Density Interconnect?

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As technology advances, business professionals find that high-density interconnect (HDI) is becoming increasingly important to handle their ever-growing data requirements and achieve breakthrough performance. From improved miniaturization capabilities to enhanced board flexibility and cost savings, HDI has something to offer everyone from the hobbyist engineer to high-volume industrial manufacturers. As such, it has become critical for those designing products where space constraints play a role.

HDI offers a greater density of interconnects than traditional circuitry, allowing design engineers to increase technological capability while reducing the weight and size of these products. Its main strength is its ability to permit efficient use of tiny components, including 0201 chips and micro-vias. These small components help reduce the overall surface area required for product production, resulting in improved cost efficiency.

Furthermore, this cutting-edge technology also allows for smaller form factors and higher packing densities, resulting in faster switching times and better device performance. With these benefits and more, it is no wonder why HDI technology is increasing so rapidly within the electronic engineering arena.HDI technology allows for thecreation of smaller and more complex PCBs, making them suitable for use in various electronic devices, including smartphones, tablets, and other portable devices.

Compared to microvias and through-hole vias, HDI technology offers several benefits, including:

  • Higher density of interconnections: HDI technology allows for a higher density of interconnections, which means more connections can be made in a smaller area. This is important for creating smaller and more complex PCBs.
  • Improved performance: HDI PCBs have a higher density of interconnections, allowing for faster signal transmission and improved electronic device performance.
  • Increased reliability: HDI PCBs have smaller features and more densely packed interconnections, which makes them less prone to damage and more reliable than traditional PCBs.

How to do DDR and BGA Fanout Routing for Your High-Density Interconnect PCB

DDR (Double Data Rate) and BGA (Ball Grid Array) fanout routing can be challenging due to the high density of the interconnects and the need to maintain signal integrity.

Here are some general guidelines to follow when doing DDR and BGA fanout routing on a high density interconnect PCB:

  1. Start by creating a clear plan for your routing strategy. This should include the placement of your components, the routing layers you will use, and any routing constraints you need to consider.
  2. Use routing layers effectively to ensure that you have enough space for all of your routing. You may need to use more than two layers for DDR and BGA fanout routing, depending on the density of the interconnects.
  3. Pay careful attention to the spacing between your traces. You should follow the manufacturer's guidelines for trace spacing to ensure signal integrity.
  4. Use vias (vertical connections through the PCB layers) to change routing layers and to connect signals between different parts of the PCB. Be sure to use the appropriate size vias for your signals.
  5. Use differential pairs for high-speed signals to improve signal integrity. This involves routing two signals with opposite phases next to each other on the PCB.
  6. Use stubs (short sections of trace) to connect to the BGA balls, rather than routing directly to them. This will help to reduce signal reflections and improve signal integrity.
  7. Use a combination of routing techniques, such as microvias and blind vias, to effectively route signals in high-density areas.
  8. Use impedance controlled routing for your high-speed signals to ensure that they maintain the correct impedance.
  9. Finally, be sure to thoroughly test your PCB to ensure that all of your interconnects are functioning correctly. This may include testing for signal integrity, crosstalk, and other parameters.

Design Basics for HDI and the HDI PCB Manufacturing Process

High-density interconnect (HDI) refers to a class of printed circuit boards (PCBs) characterized by a high component density and many interconnections in a small area. HDI boards are typically fabricated using microvia technology, which allows for the creation of small, closely spaced via holes that enable the routing of high-density interconnections between layers.

High-density interconnect (HDI) technology has been around for several decades, but it has undergone significant evolution and development over time. The first HDI boards were developed in the 1980s and were primarily used in military and aerospace applications. These early HDI boards were fabricated using a photolithography process, which involved using light-sensitive photoresist materials and UV light exposure to create the circuit patterns on the PCB.

As HDI technology evolved, new fabrication techniques were developed, including laser drilling to create via holes and plasma etching to remove excess material from the PCB. These advances enabled the creation of more complex and sophisticated HDI designs and helped to drive the widespread adoption of HDI technology in various electronic applications.

In the 21st century, HDI technology has continued to advance, with new materials and processes enabling the creation of even more complex HDI designs. These advances have led to the miniaturization of electronic devices and the development of new and improved electronic products.

HDI has revolutionized how electronic devices are designed in terms of size, weight, and performance. The process of creating a high-density interconnect (HDI) printed circuit board (PCB) involves several steps:

1.      Design

The first step in creating an HDI board is to design the circuit layout using computer-aided design (CAD) software. This design specifies the placement and interconnection of the components mounted on the PCB.

Creating an HDI board requires precision, as the circuit layout is responsible for the device's proper functioning. CAD is used to streamline the design process, ensuring accuracy in a way that manual methods cannot. Utilizing this tool, a designer can effectively plan their layout and begin the exciting device creation process.

CAD allows for experimentation with diverse fabrication techniques, such as laser cutting and pick-and-place, which makes it possible to manufacture novel devices in no time and with minimal effort. CAD plays an integral role in HDI board design and construction from its initial conception to prototyping and final production.

2.      Photomask Creation

The circuit layout design creates a photomask, a transparent film containing the circuit layout pattern. Photomask creation is critical in fabricating HDI boards.

The photomask is a physical template that contains metal trace patterns and forms part of the substrate etching process. This second step relies heavily on precision, as this filter must contain many miniature components and intricate detail that cannot be created manually.

Consequently, state-of-the-art photolithography machines, along with etching processes such as reactive ion etch, produce accurate traces suitable for complex HDI board designs, are used. Even a tiny deviation from the specified place can lead to a lack of interconnectivity and consequential board failure. Therefore, utmost attention is devoted to photomask creation within an HDI fabricator's facility.

3.      Photoresist Application

In the third step of creating HDI boards, a photoresist is applied to the surface of the PCB. This photosensitive material is designed to protect certain areas of the board during chemical processes and facilitate a consistent etch pattern. Its solid-state protect areas where conductive tracks or pads are required on the PCB.

The precise patterns created by the photoresist necessitate exacting tolerances and precise imaging techniques; otherwise, problems may occur during later stages of production. As such, this step in HDI board creation requires precise attention from experienced technicians.

4.      Photolithography

The printed circuit board is placed in a photolithography tool in the fourth step of creating HDI boards. This device utilizes UV light to selectively expose the photoresist material that was previously applied on the board. Subsequently, when not exposed to this UV light, the photoresist will be removed from these areas employing chemical etching. Furthermore, this technique is also used to create patterns and features on integrated circuits and specific other components. As such, it is mainly responsible for driving today's miniaturization efforts in many industries reliant on electronics and related products.

5.      Layering & Via Creation

Layering and via creation are implemented in the fifth step of constructing an HDI board. This involves creating multiple copper layers used in the PCB design to accommodate circuitry, routing signals and more. These processes may include etching, plating, and drilling.

In addition, vias are created to connect between circuit trace/layers on different sides of the board to enable signal routing across multiple layers. By utilizing both layerings and via creation in this step of the HDI board-making process, advantageous features such as high-frequency performance or higher density levels can be obtained from even thinner boards than before.

6.      Testing

After carefully designing and constructing HDI boards, an essential last step is to put them through comprehensive testing. This process phase is crucial to verify functionality and ensure that the boards are optimized and safely operating to industry standards. Testing includes evaluating parameters such as signal integrity, current consumption, and component tolerances, enabling the detection of any potential issue before a board is put into use.

Crafting successful HDI boards requires dedication to detail throughout every stage of their production; moreover, comprehensive testing of the end product ensures these components are fit for purpose.

Advanced PCB Materials for HDI PCB Fabrication

High-Density Interconnect (HDI) Printed Circuit Boards (PCBs) rely on calibrated, advanced materials to produce the most efficient and cost-effective results. Space and signal management are key components in an optimized design, which can be achieved using HDI techniques and the highest grade base materials including laser microvia laminates, surface treatment photosensitive dry films, surface mount adhesive films, and copper foils.

For versatile and durable performance under extreme temperatures and other environmental conditions, it is critical to use the latest generation of PCB materials equipped with reliable adhesion abilities and circuit traces to meet all fabrication standards.

By combining advanced PCB materials with cutting edge technologies such as plating-thru-hole process for blind/buried vias or inkjet printing incorporating silver nanoparticles for improved signal transmission, manufacturers can ensure excellent product quality for all types of HDI applications.

1.      High Thermal Reliability

PCB fabrication using HDI (High Density Interconnect) technology provides numerous benefits, such as enhanced thermal reliability. Through careful board design and construction, HDI PCBs provide excellent thermal protection, even in extreme operating conditions. Layering copper directly to the surface of these boards produces optimum thermal dissipation, ensuring that an increased component count does not compromise operational performance--even over extended periods of time.

2.      Ultra-Low Loss

Ultra-Low Loss HDI PCB fabrications are quickly becoming the gold standard in circuit boards. This type of PCB is a powerful tool for improving overall electrical performance, with ultra-low losses and dielectric constants rivaling those of ceramic substrates.

There are several ways to design an ultra-low loss HDI PCB:

  • Using high-quality materials
  • Optimizing trace thickness and width
  • Using differential pairs
  • Using impedance-controlled routing
  • Using low-loss laminates
  • Using controlled depth microvias
  • Using low-loss connectors

3.      Halogen-Free

The use of halogen-free PCB for HDI PCB fabrication is increasingly popular due to a strong emphasis on product safety and environmental protection in many industries. By utilizing halogen-free technology, engineers are able to create long lasting devices that meet the stringent requirements set forth by governing agencies.

Such boards often champion higher levels of thermal stability, chemical resistance, flexibility and electrical insulation than traditional designs, making them highly suitable for various industrial applications and environments. In addition, the reduced risk of corrosion from halogen free designs can help reduce costly maintenance down the road by eliminating environmental factors as a source of system failure.

4.      RoHS Compliant

RoHS, is one of the most sought after standards in PCB fabrication today. This standard identifies materials used in the manufacturing of electronic components and products that contain hazardous amounts of lead, cadmium, mercury and other environmental pollutants.

Complying with RoHS ensures that customers are purchasing high-quality Printed Circuit Boards (PCBs) made without illegal or dangerous substances.

Wrapping Up!

To stay ahead of the curve, it is essential to be knowledgeable about HDI technology and how it can benefit your business. As the world moves towards smaller, more compact electronics, HDI will become increasingly prevalent. By understanding what HDI is and how it works, you can make informed decisions about utilizing this technology in your products and designs.

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