Gain an In-depth Understanding of FR4 PCBs, from Grade Classification to Manufacturing Processes - Essential Knowledge in the Electronic Field

PCB substrates are generally made of fiberglass. In most cases, the fiberglass substrate of a PCB usually refers to "FR4". The FR4 PCB is a kind of epoxy - resin - coated copper - clad fiberglass PCB board and is made entirely of fiberglass. It's commonly used in the production of double - sided circuit boards and multi - layer circuit boards.

I. How many grades is FR - 4 PCB divided into?

1.FR - 4 A1 Copper - Clad Laminate
This grade of board is mainly used in electronic products such as communications, computers, digital circuits, industrial instruments, and automotive circuits. The quality of this series of products has fully reached the world - class level, the highest grade, and the best performance.

2.FR - 4 A2 Copper - Clad Laminate
This grade of board is mainly used in ordinary computers, instruments and meters, high - end household appliances, and general - purpose electronic products. This series of products is widely used, and various performance indicators can meet the needs of general industrial electronic products. Moreover, it is reasonably - priced and can effectively enhance price competitiveness.

3.FR - 4 A3 Copper - Clad Laminate
This grade of board is an FR - 4 product specially developed and produced for the home appliance industry, computer peripheral products, and ordinary electronic products. It is characterized by having a highly competitive advantage of an extremely low price while meeting the performance requirements.

4.FR - 4 A4 Copper - Clad Laminate
This grade of board belongs to the low - end products of FR - 4 PCB. However, the performance indicators can still meet the needs of ordinary household appliances, computers, and general - purpose electronic products. Its price is the most competitive, and the cost - performance ratio is quite excellent.

5.FR - 4 B Copper - Clad Laminate
This grade of board is relatively inferior and has poor quality stability. Generally speaking, it is suitable for products with a size of 100mm x 200mm. It is the cheapest, and we should pay attention to its selection and use.

II. The Fabrication of FR4 PCB

1.Appearance: Substrate (Insulation) + Circuit
The FR4 PCB consists of a substrate that provides insulation and the printed circuits on it.

2.Function: The ultimate goal is to connect all components according to the correct circuit diagram to form a complete working circuit. This allows for the proper flow of electrical signals and the operation of electronic devices.

3.Components and Materials: The commonly - used substrate is FR4 (fiberglass), which is composed of multiple layers (single - sided board, double - sided board, four - layer board, eight - layer board, 12 - layer, 16 - layer, and 24 - layer PCBs).

4.A printed circuit is actually formed by printing a layer of conductive material on the surface of a non - conductive substrate according to the circuit composition. Finally, a non - conductive FR4 core is formed inside, and a copper layer that constitutes the circuit is formed outside. To prevent the copper from being oxidized or conducting with the outside, there is a layer of ink on the outside. When applying the ink, the solder joints should be exposed.

5.Due to space - design limitations of the product, for FR4 multi - layer PCBs, in addition to the surface wiring, multi - layer circuits can be stacked inside. During the production process, after each layer of the circuit is fabricated, it can be positioned and pressed through optical equipment so that the multi - layer circuits are stacked in a circuit board.

6.FR4 multi - layer PCBs are made by stacking two or more layers of circuits together with reliable pre - set interconnections. The innermost two layers are composed of a traditional double - sided panel, while the outer layers are composed of independent single panels. Before lamination, the internal substrate will be drilled, through - hole plated, pattern - transferred, developed, and etched. The drilled outer layers are signal layers and are plated through by forming a balanced copper ring on the inner edge of the through - holes. Then these layers are laminated together to form a multi - substrate that can be interconnected through wave - soldering.

FR4 PCB is a traditional board frequently used by PCB MASTER Company. PCB MASTER's preferred FR - 4 boards are from Shengyi and Taiwan's Nan Ya, such as TG140, TG150, TG170, and TG260 boards. Through advanced preparation processes and technologies, high - quality FR4 PCB products are produced, which are widely used in electronics, optoelectronics, sensors, and many other fields. The company will continue to focus on technological innovation and process improvement to provide customers with better - quality products and services.