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What is HDI PCB?
HDI PCB stands for High-Density Interconnect PCB. If someone knows that HDI PCB is a circuit board designed to have high-density connections and components while minimizing board size, then we can tell he knows a lot about the PCB industry.
There is no reason why advanced electronic devices such as smartphones, tablets, medical devices and high-end computing devices should not use HDI PCB manufacturing. These devices require a high level of functionality, miniaturization, and performance in a small form factor, making high density PCBs an essential component in their HDI PCB design.
HDI PCB board representative is one of the quick development technology in PCB and PCBA process. If you know, it is a relatively high-density line distribution circuit board using micro-blind and buried-hole technology, then it means you are very concerned about the development of PCB industry technology.
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Why Choose Viasion for Your HDI PCB Manufacturer?
1. Our manufacturing of HDI PCBs has Impeccable Quality
2. Cost-effective HDI PCB board
3. Quick-turn HDI PCB Fabrication & Manufacturing
4. Your Trusted HDI PCB Manufacturer Since 2007
5. Leading manufacturing capabilities of our HDI PCB fabrication
Benefits of using HDI technology
There are many technical benefits to using HDI circuit boards. So you can use these benefits in your HDI PCB board design.
1. Design flexibility:
2. Small footprint:
4. Suitable for dense and complex packages:
5. Meeting the growing demand for smaller printed circuit boards:
6. Signal Integrity:
The advantages of HDI PCBs:
The differences between high density PCB and normal PCB:
No one would be naive enough to think that are the same as regular PCBs. Then readers will wonder, “What exactly are their differences?” Please read on.
HDI printed circuit boards are advanced technology PCBs that use a high density of components on a small area in HDI PCB manufacturing process, while normal PCBs are bare PCBs with low component density.
HDI printed circuits have a higher complexity level than normal PCBs. Normal PCBs cannot use micro vias and buried holes to connect different board layers, resulting in a higher density of components and smaller PCB size. Instead, these are quite normal in HDI PCB board design.
If someone thinks that the manufacturing process of HDI printed circuit board is as simple as a normal PCB, he is wrong. It involves multiple lamination cycles, laser drilling, and plating techniques. In contrast, normal PCBs are simpler to manufacture and use a basic lamination process.
High density interconnect PCBS are more expensive than normal PCBs due to their advanced technology and complex manufacturing process, especially for anylayer PCB.So you need to consider this in your HDI PCB board design.
HDI design are commonly used in advanced applications such as smartphones, tablets, and other portable devices with limited space. Normal PCBs are used in less complex household electronics and appliance applications.
HDI printed circuit boards have a much smaller volume and a lighter weight than normal PCBs due to smaller, finer lines and a higher layer count.
The high density of high density interconnect PCB is mainly reflected in holes, circuits, pad density, and interlaminar thickness.
Micro via: HDI PCB has blind via or micro via design. Its high requirements are mainly expressed in drilling technology of hole diameter less than 150um and cost, production efficiency and hole position accuracy control. Tradition multi-layer PCB only has through holes, not micro blinds and buried vias.
Refinement of trace width and space: It is mainly expressed in the requirement in trace defect, and trace surface roughness is increasingly strict. The standard trace width and space are not over 76.2 um.
High pad density: Solder joint density over 50 per square centimeter.
Thinning dielectric thickness is mainly expressed in dielectric thickness between layers developed to 80 um and below. It also has more and more strict requirements for thickness uniformity, especially for high-density PCBs with specific impedance and packaging substrate.
After understanding their differences, there will not be anyone who does not see that regardless of the size of the PCB or electrical performance, HDI printed circuit boards are better than ordinary PCBs. But everything has two sides. The other side of high density interconnect PCB is high-end PCB manufacturing. Its manufacturing threshold and process difficulty are much higher than normal PCB, so we need to pay more attention when manufacturing, especially for buried via plugging.
If an HDI PCB manufacturer readily assures you that the buried via plugging technology is without difficulty, you should be careful not to be fooled by it. If the buried via plugging is not done well, it will cause substantial quality problems for the whole PCB, including bumpy and uneven board surface, dielectric thickness nonuniform, and pad pitted.
Bumpy and uneven in board surface problem will make the trace not straight and causes beach phenomenon at the depression, and then cause defects, specific performance will be trace have gap, broken wire etc.
Some people take this uneven thickness of PCB media lightly. However, when undesirable results such as signal instability appear, they will regret it.
Pad pitted will make the subsequent poor packaging quality cause joint losses of components.
HDI printed circuit boards use different materials than normal PCBs, such as polyimide or polyamide-imide as the base material instead of FR4. HDI PCBs may also contain copper foils with higher electroplating thicknesses than normal PCBs, allowing for better electrical performance.
Now no one would conclude that a normal PCB would score much higher than an high density interconnect PCB in terms of performance, functionality and size. However, HDI PCBs will cost more.
Design considerations for HDI PCBs
As with any other PCB technology, the design of high density interconnect PCBs requires some specific concerns.
1. Each layer interconnect (ELIC)
2. Track uniformity and minimum line width
3. Component layout
4. Distribution of blind and buried vias:
5. Routing alignments to minimize signal integrity issues
One of the advantages of HDI PCB fabrication is the ability to use smaller routing widths for signal propagation. Despite the reduced routing width, it should be designed to achieve optimal width signal integrity. This includes using the shortest possible routing length, consistent path impedance, adequate grounding layers, and digital, analogue, and power signal isolation.
Classification and application of automobile HDI PCB:
One might wonder, “Are HDI PCBs good enough for automotive electronics?” Yes, that’s the case. HDI automobile PCBs are now used in various automotive applications, including power systems, electronic control units, audio systems, and telematics.
HDI automobile PCBs can be divided into two categories: single-sided and double-sided. Some familiar with the high density interconnect PCB industry may say, “Low-layer count automobile HDI printed circuit boards are used primarily in low-end and cost-sensitive electronics, as they are cheaper to manufacture than high-layer count automobile HDI technology PCB board, right?” Yes, you got the point. High-layer automobile HDI wiring boards are used for higher-end electronics, as they provide greater electrical performance and can support more components. Both types of automobile HDI PWB are designed to meet the stringent requirements of automobile applications. They feature advanced surface finishes that protect against corrosion and moisture, high current densities, and high thermal conductivity. There is no such thing as an HDI boards that cannot be found in a modern vehicle. They play a critical role in the safe operation of automobile electronics, making them an essential component of automobile manufacturing.
Requirements for automobile HDI PCB manufacturers:
HDI (High-Density Interconnect) PCBs are widely used in the automotive industry due to their high reliability, low signal loss, and compact size. If you are looking for an HDI printed circuits manufacturer for the automobile industry, here are some requirements that you should consider:
1. Quality certifications:
2. Automotive industry experience
3. Materials and processes:
4. Design capabilities
5. Testing and validation:
6. Supply chain management:
If an automotive HDI printed circuits manufacturer does not produce highly reliable and high-level high density interconnect HDI PCB, it cannot gain a foothold in the market.
Material requirements for automobile HDI boards:
Automobile HDI printed circuits are typically used in advanced driver assistance systems (ADAS), infotainment systems, and other safety-critical applications.
The specific material requirements for an automobile HDI boards will depend on the application, but generally, they should have the following characteristics:
1. High thermal conductivity;
2. High Tg (Glass Transition Temperature):
High-density Interconnect PCBs used in automotive applications should have a high Tg to withstand the high-temperature requirements of the automotive industry.
3. High CTE (Coefficient of Thermal Expansion):
4. High reliability and durability:
Automobiles are subject to harsh environments and a wide range of operating conditions. Using non-durable and unreliable materials to manufacture High-density Interconnect PCB is incredibly wrong.
Common materials used in automobile HDI printed circuits include high-temperature FR-4, polyimide, and ceramic materials. These materials have the above characteristics to meet the demands of automotive applications.
About the reliability test for automobile HDI PCB material:
HDI printed circuits materials are commonly used in automobiles due to their high reliability and durability characteristics that cars needed. No HDI board manufacturer is so confident in their products that it does not think it needs to perform various tests during the manufacturing process.
One common test is the thermal shock test, which involves subjecting the PCB material to extreme temperature changes between hot and cold environments to simulate the stress that the material may undergo during use.
which exposes the material to high humidity levels to evaluate its resistance to moisture and corrosion.
Mechanical tests are conducted to evaluate the strength and durability of the HDI PCB material. These tests include bend tests, vibration tests, and shock tests.
CAF tests are used to test the insulation resistance between two electric conductors of the material. The CAF test targets the chemical ageing of HDI boards and is used to ascertain the board’s long-term performance in various environmental conditions. The HDI boards are exposed to different chemicals including sulfur dioxide, nitrogen dioxide, hydrogen chloride, and ozone for a predetermined period of time. After exposure, the HDI board is tested for functionality and reliability. Any failures during the testing process are noted and can be used to improve HDI board design.
The thermal storage test of HDI boards is an integral part of the quality assurance process to ensure that these boards can withstand extreme temperatures and environmental conditions. This test is the strictest test for solder mask judgment.
According to the above test requirements for HDI PCB material, if the base material or other raw material can not meet the customer’s needs, it will cause some potential risks, and the risks for the automobile are unacceptable. So, whether to test the material or not may become the key factor to decide whether HDI PCB manufacturers are qualified manufacturers or not and also the key factor to determine whether this manufacturer can make automobile PCB.
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Frequently Asked Questions
HDI PCB, i.e. High-Density-Interconnection Printed Circuit Board, refers to a circuit board with dense circuits, high multi-layer, and drilled vias less than 0.15mm.
HDI PCBs are smaller and lighter.
High density PCBs enable smaller end-product designs and simultaneously meet higher electronic performance and efficiency standards.
In addition, HDI circuits offer better improvements for RFI, EMI, static discharge, thermal conductivity, etc.
Uneven surface of the circuit board and uneven lines in the depressions cause beaching, leading to defects such as line gaps and broken lines.
The characteristic impedance will also fluctuate due to the uneven thickness of the dielectric layer, causing signal instability.
The unevenness of the pad makes the subsequent packaging quality bad, further causing the collateral loss of components.
As mentioned above, the cost of HDI PCB is determined by many factors. Therefore, the specific price differs for different manufacturers. You are welcome to get a quote from our sales staff. We will offer you the most reasonable price.
Here are a few tips as below in HDI PCB design.
Tip 1: Select the through-hole type to minimize the complexity of the process.
Tip 2: Select the minimum number of components to apply HDI technology.
Tip 3: Space components to minimize stress and EMI.
Tip 4: Route alignments to minimize signal integrity issues.
Tip 5: Choose stack-up to minimize the costs of materials.
The above tips are a basic HDI PCB design guidelines for HDI designers.
The fabrication process for different types of and produced by using various technologies is different.
The following briefly describes the manufacturing process.
Core board fabrication → inspection → surface treatment → lamination of semi-cured sheets and RCC → press-fit → positioning the graphics for making holes→ etching of hole windows → CO2 laser drilling → de-protection film → hole metallization → pattern transfer → development → plating → de-protection film → etching → AOI inspection → coating of protective film selective plating → processing of the shape → electrical testing → final inspection → packaging
Yes, HDI PCB manufacturing process is much more complex than normal multi-layer circuit boards, since there are many times of micro vias drilling and lamination. Besides, HDI PCB board design is also much more difficult.
1+N+1 HDI structure
2+N+2 HDI structure
3+N+3 HDI structure
4+N+4 HDI structure
Any layer connection
A stack-up design is not a simple stacking of layers but usually contains a signal layer (S), a power layer (PWR), and a ground layer (GND). Among them, the arrangement of the ground layer is the key, which has a close relationship with the arrangement and direction of the signal.
Take the HDI PCB stackup design of a 6-layer HDI PCB as an example. The most conventional stack-up of 6-layer HDI PCB is arranged like this: signal – ground – signal – signal – power – signal. The stackup is very important in HDI PCB design.
Equipment: The manufacturing of HDI PCBs requires brand-new equipment and a considerable initial investment.
CO laser hole forming machine
Horizontal copper plating line PTH/CuPlating
Laser direct imaging equipment for fine line exposure
Fine line and solder-resist exposure equipment
Precision laminating machine
A complete HDI equipment production line can cost several million or even tens of millions of dollars in equipment investment alone. In addition, the factory must be equipped with a clean room to house various advanced equipment.
Personnel: The production of HDI multilayer PCB requires many professional engineers, including laser drilling engineers, HDI laminating engineers, HDI complete process engineers, line engineers, solder resist engineers, senior engineering R & D personnel, etc.
Production control: HDI PCB manufacturers need to have a complete production system, not outsource all processes, and strictly control the quality of the product.
The buried hole plugging is the core pain point and difficulty in manufacturing HDI PCBs. If the buried hole plugging is not done correctly, there will be significant quality problems, including uneven edges of the circuit board and puddle status of pads.
1) Different density in vias drill and trace width/space: the min. drill size in standard PCB is 0.2 mm, and the min. trace width/space is 0.1 mm. But HDI boards less than that.
2) HDI PCB board design is also much more difficulty since there are too much inter connections.
3) Prices are different which is very obviously.
4) Much more advance equipment are needed in HDI PCB manufacturing.
5) More difficulty in HDI PCB assembly since a lot of small chips are used.