How To Choose The Right Material For You HDI PCBs

​High-Density Interconnect (aka HDI) technology is gaining market approval lately as many electronics designers are trooping to get it. It is of note that HDI sales double that of its conventional lines based on the latest market trends. Ordinarily, any electronics designer must select the correct HDI PCB materials regardless of which application they are building. But with HDI, choosing the right equipment is particularly important because you are working with light, small, and powerful PCBs. The pitch is often below eight mils (equiv. 200um) while its aperture is usually below ten mils (equiv. 250um).

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1. What is an HDI Stack-Up ?

This section briefly outlines the definition of HDI stack and its role in determining its performance.

2. ​The Dielectric Material Properties To Consider Before Choosing

​This section describes that the best performance of HDI depends on the correct choice of dielectric materials, and is introduced from the following aspects:
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• 2.1: Decomposition Temperature (Td)
• 2.2: Glass Transition Temperature (Tg)
• 2.3: Coefficient of Thermal Expansion (CTE)
• 2.4: Delamination Time

3. What are the Material Requirements for HDI Flexible PCB ?

This section mainly lists the technical material requirements of HDI flexible PCB from the following subsections:
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• 3.1: Dimensional Stability of Flexible Materials
• 3.2 Fluidity Control of Cladding Adhesive
• 3.3 Low and Thin Profile Copper Foils
• 3.4 Material ’s Resistance to Electron Migration of Binders

4. ​Different HDI Materials Can be Used for Different

This section mainly describes PCB materials with low loss factor (Df) or dielectric loss tangent to reduce energy loss at high frequencies. For this reason, at least four types of HDI materials are suitable. Check them in the following sections.

• 4.1: Moderate speed and loss

These are currently the most popular PCB materials. They belong to the FR-4 family. Their ratio of dielectric constant to frequency response is not flat and therefore suffers from higher dielectric losses. Consequently, it can be found useful only for analog or digital applications that do not require high GHz.

• 4.2 High speed, low loss

This category of HDI materials has a Dk. to frequency curve flatter. The result is a significant low dielectric loss, which is up to half of what is obtainable with Medium Speed materials. Applications with approximately 0 GHz requirements will find it most useful.

• 4.3 High speed, low loss, high signal integrity

Dk's curve. The frequency is equally flat, and the dielectric loss is also quite small. Another advantage is that they eliminate unnecessary electrical noise common in other material categories.

• 4.4 High speed, shallow loss, high signal integrity, RF and microwave

Of all the HDI materials discussed, this type of Dk.to frequency curve is the flattest. Also, they have the lowest dielectric loss. This material category is most suitable for applications with GHz requirements up to 20.

5.  Functional cost of HDI material

​In principle, materials with lower Dk and Df. Values with excellent SI capabilities are the best choice for excellent HDI performance. Besides, the higher the quality of the required materials, the more money you are prepared to spend. Generally, high speed, a slight loss, high signal integrity, RF, and microwave materials are the most expensive categories.

6. Where can I find materials suitable for HD

You can order directly from Amazon, and it would get to your doorstep.

7. The Future of HDI PCB Based on Recent Market Trend

​Although HDI can indeed be improved, its advantages and applications are endless. HDI PCBs are now being adopted in almost all sectors, including the military, which has further increased their acceptability.

6. Conclusion

HDI technology is rapidly developing globally, and many applications are running on it. However, choosing the right dielectric material for it can be a daunting task. There are a few factors you need to consider before making your choice, and this is what we are trying to help you in this article. We do hope you find this information useful.

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