How to select the PCB Material for a Board?

How to select the PCB Material for a Board?

How to select the PCB Material for a Board?

Introduction

In order to make your PCB, it is important to know, among other things, the electrical properties of the board material. Such materials are, naturally, the bases of many circuits and are distinguished by many different parameters, some related to applications, some related to manufacturing issues, some related to environmental and mechanical considerations. With a good understanding of various PCB material properties, the process of selecting a specific one for a given set of circuit performance requirements will certainly be simpler.

You need to learn how to choose the right material in PCB production for your PCB model. There are many different material classes, each with different properties and in choosing the right one, you need to consider the needed property and the cost. A PCB generally consists of several layers of heat laminated in a single layer together. From top to bottom the material used in PCB incorporates such parts as Silkscreen, Soldermask, Copper, and Substrate.

Guidelines for the choice of right PCB Material

PCBs are made in single- and double-sided forms, some of which are copper-clad, while others use aluminum in military and aviation, industrial and medical applications. The material used should provide optimal performance for these specific areas.

PCB materials are chosen for their lightweight, quality or power handling ability. Since material levels align with performance levels, when selecting PCB materials, it is vital to determine which functions should be compared with the other. Quality is also important when making a board for home electronics or industrial equipment.

Some of the main PCB material are the followings:

  1. FR-4 (FR = Flame Retardent ) – It is a glass fiber epoxy laminate and is the most commonly used material for PCB production
  2. CEM-1-3 Composite material – it is composed of woven glass fabric surfaces and paper core combined with epoxy resin
  3. Aluminum Metal Core PCB – this means that Aluminum is used as the base material and not normal FR4/CEM1-3
  4. Heavy Copper PCB- Heavy copper PCBs are used for such applications as high power distribution, High current applications, etc.
  5. Rogers PCB- This board is used for high-frequency applications

When picking the material for a PCB, the following two key characteristics should be considered:

  1. Thermal properties
  2. Electrical properties

The thermal and electrical properties are also divided into a wide variety of properties that are very significant for the selection of PCB material. Below are the sub-properties of each category

  1. Thermal Properties
    • Thermal conductivity (K)
    • Decomposition temperature (Td)
    • Glass transition temperature (Tg)
    • The coefficient of thermal expansion (CTE)
  1. Electrical Properties
    • Electrical strength of a PCB material
    • Volume Resistivity
    • The surface resistivity of a dielectric material
    • Loss of tangent/dissipation factor
    • Relative permittivity/dielectric constant

Here are a few general ideas that can act as a starting point for choosing products for specific applications of substrates/laminates:

  • In standard boards, FR-4 is widely used. The Tg value is 135˚C. It also has a high-Tg (150-210 C) version that makes it ideal for use in high-density applications
  • For high-density systems, CEM-1, CEM-2, and CEM-3 also work well. CEM-1 offers a 122 ° C Tg, CEM-2 has a 125 ° C Tg and a 125 ° C Tg CEM-3.
  • RF-35 has a 130 ° C Tg for substrates, making it a choice for high-density systems.
  • With its Tg of 160, Teflon can be a good choice for high-frequency, microwave and high-power boards
  • For high-frequency, high-power and microwave applications, PTFE is able to supply a substrate with a 240-280 C Tg.
  • Polyimide as a substrate for high-power, high-frequency and microwave situations provides a Tg of 250 ˚C or more. Because FR4 substrates are very rigid, polyimide substrates are suitable for flex circuits. Besides flexibility, polyimides have a high-temperature resistance but are more expensive than FR4s.

Conclusion

When selecting PCB board materials, quality is of the highest importance in manufacturing any kind of board, whether it is designed for home electronics or industrial equipment. A component containing a printed circuit board may be large or small, cheap or expensive, but what matters most is that the item in question should offer superior performance throughout its expected lifespan.

To reach a consistency, the selection of PCB material must satisfy the design requirements, manufacturing quality and cost criteria. Electrical and thermal parts are included in the design requirements. Normally such considerations are important when making very high-speed PCB boards. For example, the widely used FR-4 material may not be used where the dielectric losses occur at several GHz frequencies, which may have a significant effect on signal attenuation In electrical situations. For such applications, is important to note whether the dielectric constant and dielectric loss are correlated at the specified frequency or not and Rogers material is the best choice while it is more expensive compared to FR4

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