Printed Circuit Board (PCB) materials are the backbone of electronic devices and play a crucial role in determining electronic product reliability, performance, and cost. The choice of the right PCB material is crucial for the success of any electronic project, as it affects the final product’s electrical and mechanical performance, thermal stability, and durability.
This article will provide a comprehensive guide to selecting the right PCB material for your project.
Types of PCB Materials
The main types of PCB materials are:
- FR-4: This is the most commonly used PCB material and is a type of fiberglass-reinforced epoxy laminate. FR-4 is a strong and durable material that offers good electrical insulation, excellent dimensional stability, and good thermal stability. It is also flame-resistant and suitable for a wide range of applications.
- CEM-1: CEM-1 is a low-cost alternative to FR-4 and is made from a combination of paper and phenolic resin. It is not as durable as FR-4 and is not suitable for high-temperature applications, but it is an economical choice for simple projects.
- CEM-3: CEM-3 is a higher-performance alternative to CEM-1 and is made from a combination of glass-reinforced resin and a paper core. It offers better dimensional stability and electrical insulation than CEM-1 and is suitable for a wide range of applications.
- Aluminum-based PCBs: These PCBs are made from an aluminum core and are designed for use in high-power applications. They offer excellent thermal conductivity, making them ideal for use in high-temperature environments.
Factors to Consider When Selecting a PCB Material
When selecting a PCB material, there are several factors to consider, including:
- Operating temperature: This is one of the most important factors to consider when selecting a PCB material. Different materials have different thermal stability, and it’s important to choose a material that can withstand the operating temperature of your application.
- Electrical performance: The electrical performance of a PCB material is determined by its dielectric constant and dissipation factor. It’s important to choose a material that has a low dielectric constant and dissipation factor in minimizing signal loss and interference.
- Mechanical stability: PCB materials must have good mechanical stability to withstand the mechanical stress that is generated during the manufacturing process. Choosing a material with good dimensional stability and mechanical strength is important.
- Cost: The cost of PCB materials can vary greatly, and choosing a material that fits your budget is important. It’s also important to consider the total cost of ownership, including the cost of the material, manufacturing, testing, and inspection.
It is also important to consider the environmental impact of PCB materials. Some materials, such as FR-4, contain hazardous substances like bromine and lead that can have a negative impact on the environment. Choosing a material that is both environmentally friendly and safe for human health is important.
- Availability: Another factor to consider is the availability of the material. Some materials may not be readily available in certain regions or may have longer lead times. It is important to choose a readily available material that can be delivered in a timely manner.
- End-use application: When selecting a PCB material, it is also important to consider the end-use application. For example, a PCB used in a medical device must meet strict regulatory requirements and must be able to withstand harsh environmental conditions. On the other hand, a PCB used in a consumer electronic device may have different requirements and may be subject to different regulations.
Raw Material Choices for Multilayer PCBs
Materials used in multilayer PCB manufacturing must meet two key requirements: limiting manufacturing problems and meeting performance requirements.
High-quality and successful printed circuit board production starts with the correct material selection. For common standard PCBs, your PCB manufacturer’s default materials are usually your best choice because they are reliable and cost-effective. However, when the design has special requirements or is a multilayer PCB, the choice of materials is particularly important to the project’s success.
The most important material for PCB fabrication is copper-clad laminate. It accounts for the largest part of multilayer PCB manufacturing costs. Copper-clad laminate has a critical impact on PCBs’ prices and delivery time. Different materials incur different costs and possess different characteristics, but higher-quality laminates are typically more expensive.
The following are some of the main characteristics to take note of when comparing the properties of different laminates:
- Tg = Glass Transition Temperature – At which a critical change of physical properties will occur. In the case of laminates, it transitions from a hard, glassy material into a soft, rubbery material.
- Td = Decomposition Temperature – Temperature at which the laminate chemically decomposes.
- Dk = Dielectric Constant (also referred to as εr in electromagnetics) – Indicates the relative permittivity of an insulator material, which refers to its ability to store electrical energy in an electric field. For insulating purposes, a material with a lower dielectric constant is better, and in RF applications, a higher dielectric constant may be desirable.
- Df = Dissipation Factor – Indicates an insulating material’s efficiency by showing the energy loss rate for a certain mode of oscillation, such as mechanical, electrical, or electromechanical oscillation.
Copper Clad Laminate Choices For Multilayer PCBs
Our PCB manufacturing facilities are located in China, so choosing high-quality local laminates is advisable to minimize shipping costs and lead time. The Shengyi S1000-H (Tg 150) laminate is our default choice for a high-performance, mid-Tg laminate. Shengyi S1000-H is comparable to Isola FR406 (Tg 150), a standard North American laminate option.
As outlined in Table 2 below, FR406 does slightly outmatch Shengyi S1000H in terms of Dielectric Constant and Dissipation Factor. Still, some clients may be willing to compromise on these factors for a lower cost and a faster lead time.
Table 1: Comparison of PCB Materials
|Tg 130||Tg 150||Tg 170||Tg 180|
|Td (TGA @ 5% Weight Loss)||N/A||300||N/A||300||N/A||300||350||340|
|Dk (50% Resin @ 2 GHz)||4.2||3.93||4.38||3.93||4.28||3.93||4.3||4.04|
|DF (50% Resin @ 2 GHz)||0.015||0.0157||0.015||0.0167||0.017||0.0167||0.015||0.21|
Shengyi S1141 (TG 130) is a good alternative to lower the cost of your project at the sacrifice of some quality. In cases where higher quality is needed, we recommend Shengyi S1000-2M (TG 170), the closest quality to Isola FR406 (Tg 170). Where quality is the highest priority, we recommend utilizing ITEQ IT180A (TG 180), which is also RoHS compliant. ITEQ IT180A (TG 180) is comparable in quality to Isola 370HR (TG 180). We would suggest using Shengyi S1000H (Tg 130) for typical projects. We would recommend using one of the higher quality laminate materials if any of these three conditions occur: if the PCB Design has 8 or more layers, if Copper Board is heavy with a copper weight heavier than 3oz, or if PCB Board is thin with a board thickness of less than 0.5mm.
Dielectric Thickness Choices For Multilayer PCBs
The next element to consider is the dielectric thickness, which must be specified for impedance requirements. Multilayer materials range from 0.125mm to 1mm in thickness. Thin laminates (i.e., 0.1mm or less) are necessary for some low-power applications and the continued densification of multilayer circuit PCBs. You may specify your layer stackup or use one of our recommended options outlined in this document: Guide To Multilayer PCB Layer Stackup And Thickness.
- Table 2 lists the core material thickness with copper weight for normal FR4 Material.
- 1/1 = 1 oz. copper per square foot on BOTH sides of the sheet
- 1/0 = 1 oz. copper per square foot, coated on only 1 ONE side of the sheet
- H/H = 0.5 oz. copper per square foot, coated on BOTH sides of the sheet
0/0 = UNCLAD (NO Copper).
Table 2: Core material thicknesses at available copper weights
|Thickness including copper (mm.)||Copper Weight (oz.)|
|0.145 mm.||H/H oz.|
|0.17 mm.||1/1 oz.|
|0.185 mm.||H/H oz.|
|0.2 mm.||1/1 oz. or H/H oz.|
|0.25 mm.||1/1 oz. or H/H oz.|
|0.3 mm.||1/1 oz. or H/H oz.|
|0.4 mm.||1/1 oz. or H/H oz.|
|0.5 mm.||1/1 oz. or H/H oz.|
|0.6 mm.||1/1 oz. or H/H oz.|
|0.7 mm.||1/1 oz. or H/H oz.|
|0.8 mm.||1/1 oz. or H/H oz.|
|0.9 mm.||1/1 oz. or H/H oz.|
|1.0 mm.||1/1 oz. or H/H oz.|
|1.1 mm.||1/1 oz. or H/H oz.|
|1.2 mm.||1/1 oz. or H/H oz.|
|1.5 mm.||1/1 oz. or H/H oz.|
|1.6 mm.||1/1 oz. or H/H oz.|
|2.2 mm.||1/1 oz.|
|2.4 mm.||1/1 oz.|
|2.5 mm.||1/1 oz.|
|3.0 mm.||1/1 oz.|
Prepreg Choices For Multilayer PCBs
Prepreg is a bonding material used in the fabrication of multi-layer PCB boards, which have the same properties as the core /base layer materials after curing. Board fabricators use a variety of prepreg glass styles. These styles include 106, 1080, 3313, 2116, and 7628. Limitations may apply to the number and types of prepreg, so it is best to contact us for further details.
Table 3: Prepeg material choices
|Prepreg /Glass Styles||Pressed Thickness (mm)||Prepreg Resin content|
|106||0.05 mm.||Approx. 73%|
|1080||0.075 mm.||Approx. 65%|
|3313||0.09 mm.||Approx. 57%|
|2116||0.115 mm.||Approx. 55%|
|7628||0.185 mm.||Approx. 46%|
|7628H||0.195 mm.||Approx. 51%|
Copper Thickness Choices For Multilayer PCBs
Lastly, the thickness of copper layers should be specified. This specification is usually decided based on the amount of current expected to pass through the traces of a board. Use our Trace Width Calculator to determine standard trace widths for a given copper thickness. Thicker traces can safely handle more current than thinner traces of the same width. You may also wish to specify thicker copper layers for a more robust board if you expect the board to operate in harsh conditions.
Copper-clad FR-4 laminate materials are measured using ounce(oz.) weight per square foot. The following are available sizes and their equivalent layer thickness.
- 0.25 oz. = 0.00035” (8.75μm)
- 0.5 oz. = 0.0007” (17.5 μm)
- 0.75 oz. =0.00105” (26.25μm)
- 1.0 oz. = 0.0014” (35 μm)
- 2.0 oz. = 0.0028” (70 μm)
- 3.0 oz. = 0.0042” (105 μm)
- 4.0 oz. or more = 0.0056” (140 μm) or more
The right PCB material can make the difference between a successful electronic product and a failure. By considering the operating temperature, electrical performance, mechanical stability, and cost of different materials, you can select the right material for your project and ensure its success. When in doubt, it is always best to consult with a professional PCB manufacturer to determine the best material for your project.
In conclusion, the selection of the right PCB material is a critical step in the design and development of electronic products. By considering the various factors outlined in this guide, you can select a material that meets the specific requirements of your project and helps ensure its success.