PCB prototype: PCB design: Basic PCB Composition

Basic PCB Composition

Sourced by EEWEB, Editor by Erin KOU （PCBWay）

Here are four basic composition of a Printed Circuit Board.

Substrate:
Figure:1 PCB Composition

Figure 1 PCB Composition

Figure 2 Substrate

The base material, or substrate, is usually fiberglass and its most common designator is “FR4”. This solid core gives the PCB its rigidity and thickness. Cheaper PCBs and perf boards will be made with other materials such as epoxies or phenolics which lack the durability of FR4 but are much less expensive.

Copper:

Figure 3 Copper

The next layer is a thin copper foil, which is laminated to the board with heat and adhesive. On common, double sided PCBs, copper is applied to both sides of the substrate. When we refer to a double sided or 2-layer board we are referring to the number of copper layers. This can be as few as 1 layer or as many as 16 layers or more.

Soldermask:

Figure 4 Solder Mask

The layer on top of the copper foil is called the soldermask layer. This layer gives thePCB its green color. It is overlaid onto the copper layer to insulate the copper traces from accidental contact with other metal, solder, or conductive bits. Soldermask is most commonly green in color but nearly any color is possible.

Silkscreen:

Figure 5 Silkscreen

The white silkscreen layer is applied on top of the soldermask layer. The silkscreen adds letters, numbers, and symbols to the PCB that allow for easier assembly and indicators for humans to better understand the board. Silkscreen is most commonly white but any ink color can be used. Black, gray, red, and even yellow silkscreen colors are widely available; it is, however, uncommon to see more than one color on a single board.