Copper Thickness Play in SMT Circuit Board

Copper thickness is a critical factor in the smt circuit board. It plays a role in lowering line resistance, improving thermal conductivity and extending the lifespan of the PCB. It also helps in ensuring the proper electrical current passing through the PCB. Standard 1 oz copper is suitable for most PCB applications, but high-current circuits require thicker layers to handle the higher current loads. The copper thickness is adjusted based on the specific needs of the application. The thicker the layer, the more expensive it is due to material needs and processing.

Printed Circuit Boards (PCBs) are flat, typically silver, tin-lead or gold-plated copper pads devoid of holes called solder pads that support the pins of the component connectors. They are the foundation of a modern electronic system. These pads are attached to the underlying substrate through solder connections. Surface mount technology (SMT) components are usually placed on these pads using an automated assembly process, or manually in prototypes and rework.

Each layer of a PCB is a level of conductive copper for signal routing, separated by insulating dielectric materials that prevent shorts between the conductive layers. Multilayer PCBs are a necessary feature of modern electronics to accommodate dense signal routing, complex designs, or specific power and ground planes. Multilayer PCBs also require additional insulating layers called prepreg to ensure adequate adhesion and insulation between the conductive layers.

Aside from the conductive layers, a PCB is comprised of insulating materials to provide structural integrity and protect the copper from corrosion. A typical PCB has four insulating layers in addition to the conductive copper.

What Role Does Copper Thickness Play in SMT Circuit Board?

The standard copper thickness in a PCB is around 1.4 to 2.8 mils (1 to 2 oz). It is generally adjusted depending on the requirements of the application. However, thicker copper is required for high-power applications to properly dissipate the heat generated by these large currents.

Thick copper PCBs tend to be more rigid and less flexable than their thinner counterparts. They also require longer etch times, making them more expensive than thin-copper boards. Moreover, they can be difficult to bend and shape into a desired form factor.

Unbalanced copper distribution can cause warpage, a major manufacturing issue in a PCB. A practical maximum of 0.7% of warpage on the board diagonal length is tolerated, but beyond this limit, the entire board can fail. To avoid this, the copper coverage on each layer of a PCB must be symmetrical.

As the copper thickness increases on a PCB, the minimum gap between copper features increases as well. This is a result of the etch compensation that manufacturers apply to compensate for lateral etch of copper features during the manufacturing process. However, the etch compensation is not linear and must be carefully applied to avoid signal degradation or overheating. To ensure this, Sierra Circuits’ DFM engineers apply a more efficient analysis to determine if heavy copper is suitable for the design, and the optimal etching timeframe. This ensures that the design will be manufacturable and reliable.