With any PCB material, the primary purpose is to offer insulation between conducting layers and conduct electricity. Therefore, it is vital to know the things to consider when choosing materials for your project.
So, before you manufacture a Printed Circuit Board, there are a few things you need to know about Printed Circuit Board materials. Below is a simple guide on choosing PCB material for your project.
Factors you need to consider for PCB material
When choosing materials for your PCB project, there are some factors you need to put into consideration. For instance, you need to consider the materials’ electrical, thermal, chemical, and mechanical properties. This will ensure you pick the right fit for your project.
Here are the main factors you must consider when selecting a PCB material.
Electrical properties
*Dielectric loss or dissipation factor – materials can lose power if the dissipation factor is lost. The dissipation factor of materials in PCB usually is between 0.02 and 0.001.
*Dielectric constant – this is a factor that determines the material’s electrical performance. A material must have a stable dielectric constant to be safe for application.
*Volume resistivity – the resistance of dielectric material to electricity is known as volume resistance. But external factors such as cold, heat, and moisture can impact the PCB material’s resistivity.
*Surface resistivity – a dielectric material’s resistance to electricity and insulation.
Thermal Properties
*Glass transition temperature – in most cases, a PCB material is exposed to temperatures above a certain threshold. The rate at which transformation is applied to a substrate is referred to as glass transition. It is a factor that can affect the PCB material.
*Decomposition temperature – when PCB material is exposed to some temperature, it can decompose, and when this happens, it can lose a percentage of its overall mass.
*Thermal conductivity – heat conductive property of a printed circuit board is known as thermal conductivity. This is the ability of the material to be able to transfer heat.
*Coefficient of thermal expansion – printed circuit board’s expansion rate is known as the Coefficient of thermal expansion. When the material is exposed to high or very low temperatures, it undergoes a rise in CTE.
Chemical properties
*Moisture absorption – when the material is submerged in liquid, it should have the ability to withstand. Most PCB materials have a moisture absorption value of 0.01% to 0.20%.
*Methylene chloride resistance – chemical resistance of a circuit board is known as methylene chloride resistance. This measures the resistance of a PCB material to methylene chloride absorption.
Mechanical properties
*Density – a material density is measured in g/cc (grams per cubic centimeter). Nevertheless, the density can be measured in pounds per cubic inch.
*Peel strength –The bonding ability between copper layers and dielectric in a board is known as peel strength. It is a vital property that makes a PCB material effective.
When a board is being manufactured, the peel strength is tested at high temperatures, after thermal stress, and after chemical exposure.
*Flexural strength – the capability of a PCB material to bear physical strength without breaking is known as flexural strength. It is measured in pounds/square inch or kilograms/square meter.
To test the strength of a PCB, a force is applied at the center while only the ends are supported. This also helps to determine how well the material can withstand stress or strain.
Type of PCB material
Substrates
Whether a rigid PCB, flexible PCB or rigid-flex PCB, each one needs a support base known as a substrate. A PCB substrate is a material that holds components and traces.
However, the type of substrate used can affect the performance of the circuit board. For example, a flexible substrate offers more design options, while a rigid substrate increases the durability and strength of the board.
Various types of substrates include metal substrates, FR-2, FR-4, PTFE, Low-Temperature Co-fired Ceramics, Rigid-flex substrates, and Flexible substrates, among others.
Laminates
Normally, there are 4 layers, including Substrate, Copper, Soldermask, and Silkscreen, that make a circuit board. Laminate is what holds the layers together. Hence, the type of laminate you select determines the performance and stability of your circuit board.
FR-4 laminate – this is the common one used across the board. It offers remarkable performance across all characteristics.
High-performance FR-4 laminate – this is mainly used on multilayer PCBs. It is suitable for high-frequency circuits and has a high-reliability level.
High Tg Epoxy – for multilayer PCBs and other high-level circuit boards, High Tg epoxy is the best. A material with high Tg has better moisture, heat, and chemical resistance.
Copper-clad laminate (CCL) – is made of glass fiber or wood pulp. Hence, you can consider CCL for high-voltage circuits.
Polyimide – this type of laminate is known for producing extreme environmental stability. Hence, polyimide laminate is perfect for advanced automotive, consumer, military, and other electronics applications.
Common PCB manufacturing process
The manufacturing process of a printed circuit board is very wide. Whether going through a manufacturer or making one yourself, the typical steps are crucial to developing a circuit board.
Step 1 – the first step is designing the design of the PCB.
Step 2 – the second step is to print the design of the circuit board.
Step 3 – the next step is to create the substrate. This is the insulating material that holds the elements of the board together.
Step 4 – then, you need to print the inner layers.
Step 5 – you need to get rid of unwanted copper. You can use a chemical solution to eat away the unwanted copper.
Step 6 – then, you need to inspect the layers for alignment.
Step 7 – since the board has taken shape, the next step is to laminate the layers.
Step 8 – then drilling is done. Here, holes are drilled into the layers.
Step 9 – the panel is plated with a copper layer.
Step 10 – etching is done to remove unwanted copper under the resist layer.
Step 11 – after cleaning the panels, a Soldermask is applied.
Step 12 – silkscreening is the next step where vital information is printed on the board.
Step 13 – The next step is cnc milling V-cut, which will help to remove the PCB from the whole board.
Step 14 – before the board is considered complete, it has to undergo testing.
Bottom-line
A Printed Circuit Board needs solid and reliable materials to ensure they are practical and perform better. Hence, it is important to learn more about the materials before you start the manufacturing process.
The above information makes it possible to choose the right material for your PCB project. Moreover, select a reliable manufacturer that helps you develop the best circuit boards.
