How should you choose PCB material

Materials used to manufacture printed circuit boards (PCBS) include a group of insulating/dielectric and conductive materials used to construct the circuit board interconnects. A wide variety of materials are available to meet different performance and budget requirements. The type of material used to make PCBS is a key factor in the durability and functionality of PCB components. Choosing the right PCB material requires an understanding of the available materials and their physical properties, as well as how they align with the desired function of the board.

Type of printed circuit board

There are 4 main types of PCBS:

L Rigid — solid, non-deforming single – or double-sided PCB

Flexible (Flex) – usually used when the PCB cannot be confined to a single plane or in a non-plane position

L Rigid-flexible — is a combination of rigid and flexible PCB, where the flexible board is connected to the rigid board

L High frequency — These PCBS are typically used in applications that require special signal transmission between the target and the receiver.

The PCB material chosen is required to optimize the performance of the final printed circuit board assembly. Therefore, it is important to consider the performance and environmental requirements of the circuit components.

Material properties to be considered when selecting PCB materials

Four Main Characteristics (from IPC 4101 — Rigid and Multilayer PCB Base Materials Specification) The type of PCB material is critical to help define the performance of the base material.

1. CTE — Thermal expansion coefficient is a measure of how much the material expands when heated. This is very important on the Z-axis. In general, expansion is greater than the decomposition temperature (Tg). If the CTE of the material is insufficient or too high, failure may occur during assembly because the material will rapidly expand over the Tg.

2. Tg — The vitrification transition temperature of a material is the temperature at which the material changes from a rigid glassy material to a more elastic and flexible rubbery material. At temperatures higher than Tg materials, the expansion rate increases. Keep in mind that materials can have the same Tg but have different CTE. (A lower CTE is desirable).

3.Td — decomposition temperature of laminates. This is the temperature at which the material breaks down. Reliability is impaired and delamination may occur as the material releases up to 5% of its original weight. PCB with higher reliability or PCB operating under harsh conditions will require a TD greater than or equal to 340°C.

4. Delamination time at T260 / T288 — 260°C and 280°C — Cohesion failure of laminates due to thermal decomposition (Td) of epoxy resin matrix when PCB thickness is irreversibly changed.

To choose the best laminate material for your PCB, it is important to know how you expect the material to behave. One of the purposes of material selection is to align the thermal properties of the laminated material closely with the components to be welded to the plate.