What Factors Should be Considered When Choosing the Right PCB Material?

April 7, 2025

PCB Material selection is a crucial process before proceeding to the fabrication of printed circuit boards. Selecting the wrong combination of PCB materials has serious consequences such as manufacturing defects and product failures. Going over the whole design process again due to material choice issues entails significant costs and resources. This is aside from the cost implications and bad reputation to customers if failing products are shipped to their end. It is therefore important to choose carefully the PCB materials that will meet the intended performance of the PCB. In this discussion, we will dwell on the factors that need to be considered when choosing the right PCB board material.

The PCB Stack-Up and Construction of a Printed Circuit Board

What makes up a PCB is worth understanding before diving into the discussion of PCB material selection guidelines. Each part of the PCB serves unique roles in the functionality of the circuit boards. Having a mental picture of the circuit board construction and PCB board materials will assist us in comprehending the required characteristics of each PCB material.

Dielectric Material. The layer that is sandwiched between copper layers of the PCB is called a dielectric material. For multi-layer boards, the dielectric boards consist of the core and prepreg that are laminated together to complete the stack-up. The most popular used dielectric material of PCB is the FR4 or Flame Retardant with code “4” indicative of an epoxy resin with woven fibreglass. Despite the popularity of FR4, there are vast selections of dielectric materials that can be substituted, which will all depend on the desired properties of the designer and the fabricators.
Copper Layers. The copper on the PCB provides connectivity which sits above and below the dielectric layer. This layer comes in various thicknesses which can come in standard specifications or customized sizes which can be more costly. The number of PCB layers is counted based on the layer count of the copper and not on the dielectric material of the PCB. The copper structure on a multi-layered board also comes in the form of vias to allow connection and signal transfer across the layers.
Solder Mask. The solder mask is the top mask that is applied at the top and bottom of the printed circuit boards. It serves at least two purposes. One is to protect the copper from oxidation and degradation from exposure to the environment. Second, it isolates and assists the solder to be confined on the pads during the soldering process.
Silkscreen. Another peripheral layer of the PCB is the silkscreen. Human readable information is applied on the solder mask for traceability and fabrication reference purposes. Silkscreen also allows test engineers to immediately spot the components on the PCB during debugging.

Factors to Consider in Choosing the Right PCB Materials

An effective technique when doing PCB material selection assessments is to tabulate all the important factors and PCB board material properties that are crucial in the decision process. In this way, side-by-side comparisons are done to determine the best option that will meet the requirements.

Performance Targets. Every PCB is designed uniquely in accordance with its applications. For instance, automotive and aerospace applications are expected to have tighter reliability requirements compared to consumer electronics due to the criticality of device safety. Also, the primary PCB material characteristic will be what needs to be prioritized. As an example, if efficient heat dissipation is important in the design, then a metal core may be the best choice to have a high thermal conductivity laminate material of PCB. If there is a space constraint and the need for tiny electronics, then it is best to go for flexible or rigid laminate PCB materials.
Dielectric Constant. The dielectric constant, which is often abbreviated as Dk is an important laminate property that is primarily affected by the ratio of raw PCB materials on a PCB such as resin and filler volume. The values for Dk directly affect the performance of the PCB in terms of signal integrity and impedance. Note as well that the dielectric constant of a PCB circuit board material may change over certain frequencies, thus a PCB material that has a constant value for dielectric constant over the operating range is much preferred especially for high-frequency applications.
Thermal Management. PCB Materials behave differently when subjected to various temperatures. They tend to have different compression and tensile stresses because of varying coefficients of thermal expansion (CTE). PCB design without considering proper thermal management may lead to delamination issues and overheating components. For PCBs that will be subjected to high temperatures such as LED applications, an aluminum or copper heat sink or substrate may be a good option.
Mechanical Properties. In real-life applications, PCB does not operate in an ideal situation with controlled environments, instead, it is often subjected to shock and vibration. This is why the mechanical properties of the PCB material are extremely important. The adhesion of the laminate to the copper structure is often influenced by the roughness of the copper material. A comparison of the peel strength of the dielectric material must be done.
Quality. When choosing the right PCB materials, quality is of high importance. It can be tempting to choose a cheap, sub-standard alternative to a specific part, but know that this can influence the expected lifetime and performance of the PCB. Quality means that the materials will be able to fulfil the requirements and criteria of the functional circuit board.
Cost. Considering cost means sourcing the least cost material of PCB that can perform the intended function effectively. The advancement in research and technology led to wide PCB material options of varying mechanical strength, dielectric properties and thermal characteristics. The decision to go for the least cost PCB circuit board material should be balanced with the design performance requirements.

Selection for Copper Foil Used in Circuit Boards

Putting PCB materials together will result in a different set of properties based on the interaction of the combined materials. As earlier stated, copper foil is part of the PCB structure that connects components and allows interconnection across the layers. Thus, a basic understanding of the copper foil material is also as equally important as knowing the dielectric material.

Copper Thickness. The thickness of the copper layer has a direct influence on the thermal conductivity of the PCB. A multi-layer PCB may consist of a copper layer with different thicknesses.
Purity. Copper foil is not 100% copper as some impurities can be present. An electronic grade copper has at least 99.7% purity. The impurities introduced in copper foil have an impact on its mechanical and electrical properties.
Surface Roughness. Copper foil in a PCB comes in different roughness grades. For high-speed electronics, it is particularly important in the signal transmission known as the skin effect. The rougher surface has better bonding with the laminate but must be regulated to avoid skin effects.
Type of Copper Foil Fabrication. There are two types of manufacturing methods for copper foil: electrodeposited and rolled. Each type presents unique properties and advantages. During electrodeposition, copper foil is slowly deposited on a rotating form immersed in a copper solution connected to a voltage source. Rolled copper is done by subjecting the copper to a series of rolling operations until the foil thickness is achieved. Surface treatment is done to attain the desired surface roughness.