In the intricate world of printed circuit boards (PCBs), the layering process plays a crucial role in determining the functionality and appearance of the final product. In this blog post, we will delve into the typical layers of a 2-sided PCB board, exploring the significance of each layer in the fabrication process.
The following shows a complete stack-up of all the layers that must be sent in gerber file format to the PCB fabrication house to make a completed circuit board.
The following explains the roles of the individual pcb layer.
Outline Layer:
The first layer we encounter in the stack-up is the outline layer, which defines the shape of the PCB. This structure serves a vital role in separating a specific circuit board from others in the manufacturing panel. An endmill is employed to precisely drill out the board from the larger panel, a process known as "routing out." It's important to note that "routing out" should not be confused with the use of "routing" when drawing traces on the board. Many fabrication shops insist on the presence of an outline layer before committing to the fabrication process. Without it, they lack the information needed to distinguish where one board ends and another begins within the large panel.
Drill Layer:
Moving on to the drill layer, this component provides essential information about hole sizes and their precise locations on the PCB. A precision CNC drilling machine utilizes this information to drill every hole required for the circuit. The drill layer is a crucial aspect of PCB fabrication, ensuring the accurate placement and sizing of holes for various components.
Silk Screen Layer:
The silk screen, sometimes referred to as the overlay layer, is present on both the top and bottom surfaces of the PCB. This layer is responsible for displaying printed text or numbers that identify each part, along with any additional written reference information. Beyond textual elements, the silk screen can also include images, logos, and pictures, providing a visual guide for assembly and maintenance purposes.
Soldermask Layer:
The soldermask is a dielectric layer with small openings strategically placed to reveal the underlying metal. These openings expose pads to which components will be soldered. The soldermask coating is essential in preventing solder from flowing over the covered copper traces, ensuring precise and controlled soldering connections. This layer is instrumental in protecting the PCB from potential short circuits and enhancing the overall durability of the circuit board.
Understanding the typical layers of a 2-sided PCB board is crucial for both PCB designers and fabricators. Each layer serves a unique purpose in the fabrication process, contributing to the functionality, durability, and visual appeal of the final product. As technology advances, the importance of these layers continues to grow, shaping the landscape of electronic design and manufacturing.
See also the previous post on PCB Technology and PCB Design remarks on Thermal and Thermal Relief Vias.
