The mother of electronics

PCB, the Chinese name is called printed circuit board, is an important electronic component, the support of electronic components, and also the carrier for the electrical connection of electronic components, so it is called the ‘mother of electronic products’. Don't underestimate this seemingly ordinary board, it is a kaleidoscope in the electronics industry, turning our technological dreams into reality.

Printed circuit boards are classified into rigid printed boards, flexible printed boards and rigid-flexible boards according to the strength of the printed board substrate; they are like the three musketeers in the electronics industry, each with its own strengths and abilities.

The rigid printed circuit board is like a ‘steel warrior’. It is made of rigid substrates. Its rigid substrates include phenolic paper laminates, epoxy paper laminates, polyester glass felt laminates, and epoxy glass cloth laminates.

Flexible printed circuit boards are like a ‘judo master’. They use flexible substrates, such as polyimide or polyester film, and are like ‘yoga masters’ in the electronics industry. This type of circuit board not only has good heat dissipation but also can be bent, folded, and twisted and even stretch freely in three-dimensional space, just like ‘Transformers’ in the electronics industry. It can reduce the size of electronic equipment, achieve lightweight, miniaturization, and thinness, and thus realize the integration of component devices and wire connections.

The rigid-flexible PCB is like a ‘Tai Chi master’. It cleverly combines the flexible substrate and the rigid substrate, just like a "hybrid" in the electronics industry. It has both the firmness of a rigid printed circuit board and the flexibility of a flexible printed circuit board, making it a ‘jack of all trades’ in the electronics industry.

According to the conductive structure of printed circuit boards, there are single-sided boards, double-sided boards, and multi-sided boards.

Single-sided board, this ‘lone ranger’, has conductive patterns on only one side. It is simple and direct, just like a tough guy who goes straight ahead and moves forward courageously.

Double-sided board, this ‘double agent’, has conductive patterns on both sides. It can handle more complex circuit tasks.

Multi-sided board, this ‘multi-layer tower’, is made of three or more layers of conductive patterns and insulating materials bonded together alternately and laminated together. It is like a ‘high-rise building’ in the electronics industry, stacked layer by layer, complex and powerful, and able to carry more electronic tasks.

These three have their own strengths. Single-sided boards are suitable for simple circuits, double-sided boards are suitable for slightly more complex circuits, and multi-sided boards are suitable for circuits that require multiple layers of space to achieve complex functions.

So how are printed circuit boards made? Today we take ‘single-sided boards as an example to explore the manufacturing process of printed circuit boards.

Single-sided panels are made using screen printing, which requires printing three layers of ink: anti-corrosion ink, solder mask ink, and character ink. Currently, photocuring is basically used.

The birth of copper circuits on printed circuit boards is like a carefully planned "metal sculpture exhibition". Our artists are ferric chloride or cupric chloride solutions, which perform the magic of corrosion on copper-clad boards and carve out delicate circuit patterns. But not all circuits want to be works of art. Those circuit parts that do not need to be corroded will wear ‘protective clothing (corrosion-resistant ink)’ made of corrosion-resistant materials to ensure that they are safe and sound in this 'corrosion’. The corrosion-resistant ink is screen-printed to leave an corrosion-resistant pattern on the copper-clad board, and then solidifies to become a ‘tattoo’ on the circuit board. After the baptism of corrosion, the copper-clad board is reborn, and the copper circuits reveal their true appearance. Then the ‘makeup remover’ of lye comes on stage, and with a light touch, the corrosion-resistant ink is completely removed.

Next, our printed circuit board needs a loyal guardian - solder mask ink. On the board, except for the solder joints, the ‘social masters’, the rest of the board needs to be protected by solder mask ink to ensure that only the solder joints can have ‘intimate contact’ with the solder during the wave soldering ‘party, while other circuit graphics remain ‘cold’. The selection of solder mask ink is very strict. It must not only have excellent electrical and physical and mechanical properties, but also be able to withstand the high temperature test of 260°C. Solder mask ink is screen printed and becomes a ‘permanent resident’ on the circuit board after curing.

In order to prevent the plug-in and maintenance partners from getting lost, the circuit diagram and the location of electronic components need to be clearly marked on both sides of the circuit board with lines and characters. This is the role of character ink, which is also printed on the circuit board by screen printing and is also a ‘permanent resident’ on the printed circuit board. Its performance requirements are the same as those of solder mask ink.