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PCB Technology

PCB Technology - FR-4 substrates for PCB

PCB Technology

PCB Technology - FR-4 substrates for PCB

FR-4 substrates for PCB
2023-02-05
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Author:PCB

What is the composition of PCB board?

PCB is the abbreviation of English Printed Circuit Board, the Chinese name is Printed Circuit Board, also known as Printed Circuit Board, Printed Circuit Board, is an important electronic component. It is the provider of electrical connection for electronic components.

The PCB starts with the most basic unit: the substrate, which consists of several layers, each of which plays an important role in the function of the final PCB. These alternate layers include:


1. Substrate: This is the base material of the PCB. It gives the PCB board its rigidity, and is now most commonly used as the FR4 substrate.

2, Copper: Add a thin layer of conductive copper foil to each functional side of the PCB - on one side if it is a single-sided PCB, on both sides if it is a double-sided PCB. This is the copper alignment layer.

3.Solder Resist Layer: On top of the copper layer is the solder resist layer, which gives each PCB its distinctive green colour. It keeps the copper traces from intentionally coming into contact with other conductive materials that could cause a short circuit. In other words, the solder keeps everything in place. The holes in the soldermask are where the solder is applied to connect the components to the board. Soldermask is a critical step in the smooth manufacture of PCBAs because it prevents soldering from occurring on unwanted parts and avoids short circuits.

4, silkscreen: white silkscreen is the last layer on the PCB. This layer adds labels in the form of characters and symbols on the PCB. This helps to train the function of each component on the board.


PCBary according to their substrate information, high frequency microwave boards, metal substrates, aluminium substrates, iron substrates, copper substrates, double-sided FR4 substrates and multi-layer FR4 substrates. The wiring is used as a communication tool between the components, and a large copper surface is designed as a grounding and power layer. The wiring and graphics are made at the same time. The high wire density, small size and light weight make it suitable for the miniaturisation of electronic equipment.


The substrate of the PCB itself is made of insulating and non-bending material. The small wires visible on the surface are copper foils, which originally covered the entire board, but were partially etched away during the manufacturing process, leaving behind a mesh of small wires.


Advantages and Features of FR-4 Substrates

General single- and double-sided FR-4 substrates and multi-layer FR-4 substrates are made of FR-4, the FR in FR-4 indicates flame retardant, and the number 4 separates this data from other data in this category. FR-4 is a glass fibre reinforced epoxy laminate that looks like a thin woven fabric sheet. FR-4 also represents the grade used in the manufacture of these laminates. The glass fibre structure provides structural stability to the data. The glass fibre layer is covered with a flame retardant epoxy resin. This brings durability and strong mechanical performance to the material. All these properties make FR-4 substrates very popular among circuit board manufacturers.


The technical characteristics of FR-4 substrate are mainly in: electrical insulation, stable performance, good flatness, smooth surface, no pits, thickness tolerance standards, suitable for high-performance electronic insulation requirements of products, such as FPC reinforcement boards, PCB drilling pads, glass fibre dielectrics, potentiometers carbon film printed glass fibre boards, precision planetary gear (wafer lapping), precision test panels, power (electrical) equipment insulation support bar Spacer plates, insulating gaskets, transformer insulating plates, motor insulating parts, grinding gears, electronic switch insulating plates and so on.


FR-4 substrate has been widely used in military, communications, computers, digital circuits, industrial instruments and meters, automotive electronic circuits and other electronic products, various performance indicators can meet the needs of general industrial electronic products. It has a good price-performance ratio.

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