multi-layer PCB
High-end design, multi-layer PCB internal structure and experience sharing
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HDI PCB Manufacturing and Assembly
HXPCB focuses on the research and development of ultra-large size circuits board, multi-layer PCBs, metal-based PCBs, rigid-flex high-frequency PCBs, HDI PCBs, and related processes. We offer comprehensive services, including PCB design, prototyping, processing, and assembly.
What is HDI PCB?
HDI PCB (High-Density Interconnector Printed Circuit Board) is a printed circuit board with higher circuit density, more interconnection points, smaller size and higher integration. Compared with traditional PCB, HDI PCB adopts more advanced technology in the manufacturing process, such as microvias, blind vias and buried vias, as well as more sophisticated design methods, which compresses the area and volume of the circuit board, while improving its signal transmission capability and performance.
HXPCB is a company engaged in PCB production and assembly. You can purchase our existing HDI PCB and other products at HXPCB, or you can tell us your problems and we will give you a preferential price and satisfactory solution.
HXPCB provides HDI PCB manufacturing services
HXPCB has significant professional capabilities in multi-layer PCB manufacturing, with an average number of layers ranging from 8 to 20 and a maximum of 64 layers, demonstrating its advanced level in inner-layer manufacturing technology and lamination processes. Multi-layer PCB technology is an important driving force for the entire PCB industry. HXPCB has established a clear competitive advantage in this field with years of technology accumulation and practical experience.
We deeply understand the complex requirements for multi-layer PCBs in various industries and are able to provide customers with high-quality and high-reliability solutions. Whether in the manufacturing or prototyping stages, HXPCB always adheres to strict quality standards and strives to become a trustworthy partner in the industry
Advantages and Applications of HDI PCB
HDI PCB uses advanced technologies such as microvias, blind buried vias, and stacked vias to achieve more sophisticated circuit layout and higher wiring density. Its main advantages are:
1. Significantly reduce the size of PCB to meet the needs of portable devices for thinness, shorten the signal transmission path, and improve signal integrity and transmission speed.
2. Reduce the number of connection points and welding times, improve product reliability and stability, support more complex circuit design, and meet the needs of multi-functional integration.
3. Adapt to complex applications, widely used in communications, consumer electronics, automotive electronics and other industries, support higher frequency and more complex circuit design polymer applications are as follows:
Consumer electronics
Smartphones, tablets, headphones, smart watches
Communication equipment
5G base stations and equipment, Wi-Fi routers, fiber-optic communication equipment
Automotive electronics
Advanced driver assistance systems (ADAS), in-vehicle entertainment systems, electric vehicle control systems
Medical equipment
Portable medical devices, imaging equipment, implantable devices
HPC and data centers,
Servers, AI accelerators, GPU, TPU hardware
Aerospace and military
Navigation and radar systems, satellite communication equipment, military equipment
Industrial control and IoT
Industrial automation equipment, IoT sensors and gateways
High-frequency and radio frequency (RF) equipment
Satellite communications, RF modules, radar systems: automotive radar, weather radar
Materials used to make HDI PCBs
1.FR-4: The most common PCB substrate, suitable for general applications, with good insulation and mechanical strength. Usually made of glass fiber and epoxy resin.
2.Polyimid (PIe): Suitable for high temperature and high frequency applications, with excellent thermal stability and electrical properties.
3.PTFE (polytetrafluoroethylene): Mainly used in high-frequency circuits, providing low dielectric constant and low loss characteristics, but the cost is higher.
4.Conductive materials
Copper foil: The most commonly used conductive material in HDI PCBs, usually used for the formation of circuit patterns.
Usually in the form of electroplated copper (Electrolytic Copper) and mechanically stripped copper (Copper Foil).
Gold or silver: Mainly used in applications with high frequency and high signal integrity requirements. They are used in contact points (such as connectors, pads) and can provide excellent conductivity.
5.Dielectric layer
Polyimide film: Used to form a dielectric layer between different layers, providing good insulation properties.
Synthetic resin: For example, epoxy resin, used between different layers in the laminate to increase reliability.
6. Filling materials
Micro glass beads and ceramic beads: These filling materials are often used to improve the mechanical strength and thermal stability of the substrate, especially in high-temperature applications.
7. Protective layer
Photoresist: Used in the formation of circuit patterns, used to encapsulate or remove excess copper during the manufacturing process.
Surface protective coating: Such as HASL (hot air solder immersion), ENIG (gold plating) or OSP (organic protective coating), used to protect the copper layer on the circuit board from oxidation and environmental effects.
8. Connecting materials
Solder: Commonly used solders include lead-tin alloys (although they are banned in some applications) and lead-free solders (such as tin-silver-copper).
Conductive adhesive: In some high-frequency and high-performance applications, it is used to bond and connect solder joints.
9. Special materials
Thermal management materials: In some high-power applications, thermal conductive materials can be used to help manage heat and maintain a stable operating temperature.
Difficulties in HDI PCB Design
1. High-density layout:
One of the biggest challenges is to realize complex circuit layout in a limited space, which requires designers to have superb layout skills.
2. Signal integrity issues:
In high-frequency applications, signal reflection, noise and crosstalk problems are more obvious, and simulation tools are needed for analysis.
3. Thermal management issues:
High-power components often have thermal problems, and thermal conduction and air flow need to be considered during design.
4. Manufacturing tolerance:
Differences in manufacturing processes and tolerances of different manufacturers may lead to mismatches between design and manufacturing.
5. Complexity of multi-layer stacking:
When designing multi-layer stacking, it is necessary to ensure that the electrical connection and mechanical strength between each layer meet the requirements.
HDI PCB Design Details
Layer design:
HDI PCBs usually use multi-layer design to achieve high-density circuit wiring, and the number of layers can range from 4 to 20 layers.
The functions of each layer should be reasonably planned during design, such as the distribution of signal layer, power layer and ground layer.
Microvia and blind hole design:
1. Use microvias (usually less than 0.2mm in diameter) and blind holes to achieve effective connections between different circuit layers.
2.Ensure that the hole design meets the manufacturer’s capabilities to avoid post-manufacturing problems.
Routing and signal integrity:
1.Consider the direction and length of the signal when routing to reduce interference and delay.
2.Use methods such as series, parallel, and differential pairs to optimize signal integrity, considering the number and location of vias.
Material selection:
1.Choose a suitable substrate (such as FR-4, polyimide) and copper thickness to adapt to current load and frequency requirements.
2.Choose a suitable surface treatment (such as hot air solder dipping ENIG, etc.) according to the application to ensure good solderability and corrosion resistance.
Thermal management:
Consider the heat dissipation path during design, use heat pipes and heat dissipation materials to manage the heat of high-power components.
Manufacturing process compatibility:
The design must consider the limitations of the manufacturing process, including hole spacing, line width, spacing, etc., to avoid affecting production.
HDI PCB Parameter Table
| Parameter | Typical Values/Range | Parameter | Typical Values/Range |
| Layer Count | 4 to 20 layers; often 8, 10 layers | Voltage Rating | > 2000 V (depends on materials and design) |
| Substrate Material | FR-4, Polyimide, PTFE, Ceramic Materials | Mechanical Strength | Varies significantly based on materials and thickness |
| Copper Thickness | 1 oz (35 μm), 2 oz (70 μm), or thicker | X-Ray Inspection | Common in complex high-density PCBs |
| Hole Size | Microvias ≤ 0.2mm; blind/buried vias generally <0.3mm | Test Points | Flexible arrangement based on design |
| Trace Width and Spacing | Trace width ≥ 0.1mm; spacing ≥ 0.1mm | Environmental Standards | RoHS, REACH, etc. |
| Surface Finish | HASL, ENIG, OSP, Immersion Gold | Manufacturing Process | Laser drilling, conventional milling, etc. |
| Impedance Control | 50 Ω, 75 Ω, 100 Ω (varies by application) | Pad Size | Depends on component type |
| Dielectric Constant | FR-4: 4.5-5.0; Polyimide: 3.2-3.5 | Ground Plane Design | Layered ground or circular ground, based on requirements |
| Thermal Endurance | Tg (Glass Transition Temperature): typically ≥ 130°C | Outline Dimensions | Based on product design requirements |
| Frequency Response | Optimization of 50Ω impedance for high-frequency applications |
| Parameter | HDI PCB | Standard PCB |
| Layer Count | Typically 4 to 20 layers | 1 to 10 layers, often up to 6 layers |
| Substrate Material | FR-4, Polyimide, specialized materials for high performance | Primarily FR-4, sometimes Phenolic |
| Copper Thickness | Generally 0.5 oz to 2 oz (average 1 oz) | Typically 1 oz, but can vary (0.5 oz, 2 oz) |
| Hole Size | Microvias (≤ 0.2mm) and blind/buried vias (< 0.3mm) | Standard vias with larger sizes |
| Trace Width and Spacing | Minimum trace width and spacing can be narrower (≥ 0.1mm) | Wider traces and spacing (usually ≥ 0.2mm) |
| Impedance Control | Often required for high-speed designs (50Ω, 75Ω, etc.) | Generally less critical, 50Ω mainly for RF boards |
| Dielectric Material | Low dielectric constant materials (e.g., PTFE) | Standard FR-4 with higher dielectric constant |
| Thermal Performance | Better thermal performance with high Tg materials | Limited thermal performance |
| Surface Finish | ENIG, OSP, immersion gold with better solderability | HASL, OSP, and basic finishes |
| Manufacturing Process | More complex processes (laser drilling, advanced lamination) | Traditional processes (mechanical drilling, simple lamination) |
| Design Complexity | High complexity with intricate layouts and via designs | Simpler layout, fewer constraints |
| Signal Integrity | Enhanced signal integrity due to controlled impedance and shorter paths | Adequate for low-frequency applications |
| Size and Form Factor | Compact, designed for miniaturization | Typically larger and bulkier |
| Cost | Higher due to complexity, advanced materials, and technology | Generally lower production costs |
| Applications | Used in smartphones, tablets, high-end electronics | Used in consumer electronics, appliances, basic devices |
| Testing and Inspection | Requires sophisticated testing (X-ray for hidden vias) | Conventional testing sufficient |
| Material Parameter | HDI PCB | Standard PCB |
| Base Material | Advanced materials like Polyimide, FR-4, or specialized low-loss substrates | FR-4 or Phenolic resin (double-sided PCB) |
| Dielectric Constant (Dk) | Low Dk materials for high-speed applications (e.g., Dk < 4.0) | Standard FR-4 (Dk around 4.5 — 5.0) |
| Glass Transition Temperature (Tg) | Higher Tg (≥ 170°C) to withstand higher temperatures | Tg typically around 130°C — 150°C |
| Copper Material | Electrolytic copper with controlled thickness | Electrolytic copper, can have varying thickness up to 2 oz |
| Copper Foil Types | Smooth or rough surface, reduced roughness for high-frequency | Standard rough or smooth copper foil |
| Surface Finish | ENIG, OSP, Immersion Gold, Electroless Nickel | HASL, OSP, ENIG, and sometimes LF HAL (Lead-Free Hot Air Leveling) |
| Solder Mask | High-resolution, often low-flow solder mask for precise applications | Standard solder mask with medium resolution |
| Via Filling Materials | Specialized filling compounds for microvias (could be resin) | Not commonly filled; standard plating or vias left open |
| Adhesive Materials | Advanced adhesives (like epoxy) used in multilayer bonding | Standard epoxy for multilayer lamination |
| Thermal Management Materials | Thermal via designs, thermal conductive materials for heat dissipation | Basic thermal management with thicker copper for heat sinks |
| Special Treatments | Surface treatments for RF and microwave applications | Limited surface treatments, mainly for standard solderability |
HXPCB: HDI PCB Assembly Service Provider
HXPCB is committed to providing customers with one-stop solutions for high-density interconnect (HDI) PCBs. We have our own production equipment and rich technical experience to meet the manufacturing and assembly needs of high-precision and high-complexity circuit boards.
Professional service advantages:
1. High-precision processing: support micro-hole drilling (minimum hole diameter 0.1 mm), fine lines (minimum width 0.075 mm), to ensure high-density design.
2. High-quality materials: select high-performance substrates (FR-4, Rogers, PTFE, etc.) to meet high-speed, high-frequency and high-reliability requirements.
3. Flexible assembly capabilities: support complex packages such as BGA, CSP, QFN, and provide comprehensive services from raw material procurement to finished product delivery.
4. Strict quality control: pass ISO certification and multiple tests (AOI, X-ray, electrical testing) to ensure product performance and reliability.
FAQ
Frequently Asked Question
The number of layers of an HDI PCB can range from 2 to dozens of layers, depending on the design requirements. Generally, 4 or 8 layers are more common configurations, but complex applications may require designs with higher layers.
HDI PCBs are generally more expensive than traditional PCBs because their manufacturing process is more complex and requires a higher level of technology. However, considering the performance improvements and reduced size they bring, this investment is usually worth it.
Microvia and blind via technology commonly used in HDI PCBs can achieve efficient connectivity between different layers. The diameter of these holes is usually small, sometimes up to 0.1mm, making the wiring more dense and efficient.
When designing HDI PCB, you need to consider the wiring density, signal integrity, power distribution, thermal management, and feasibility of the manufacturing process. At the same time, ensure that the design meets the cost budget and production capacity. efficiently. The challenge lies in high-precision alignment and quality control.
HDI PCB can provide higher electrical signal transmission speed and better electromagnetic compatibility. At the same time, due to its smaller size and lighter weight, it is suitable for applications with limited space and high performance requirements.
HDI PCB’s reliability is generally high, but this also depends on the design and manufacturing standards. High-quality materials, good soldering process, and appropriate electrical design are all key factors to ensure the reliability of HDI PCB.
HDI PCBs are used in many industries, including consumer electronics, communication equipment, automotive electronics, medical equipment, and industrial control. Their high-density advantage makes them very suitable for high-performance products.
HDI PCB can be produced in accordance with the ROHS directive, which requires the reduction or restriction of the use of certain hazardous substances. Ensuring that HDI PCBs are ROHS compliant is an important consideration for any modern electronics manufacturer, especially today when environmental protection and sustainability are increasingly valued.
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