Use/characteristics of PCB materials and matters needing attention

Today’s PCB substrate substrate is composed of Cooper Foil, Reinforcement, resin and other three main components, but since the Lead Free process began, the fourth powder Fillers have been massively added to the PCB board. To improve the heat resistance of PCB.

We can think of copper foil as the blood vessels of the human body, used to transport important blood, so that PCB can play the ability of activity; Reinforcement can be imagined as human bones, used to support and strengthen the PCB will not fall down; Resin, on the other hand, can be thought of as the muscle of the human body, the main component of PCB.

The uses, characteristics and matters needing attention of these four PCB materials are described below:

1. Copper Foil

Electric Circuit: a Circuit that conducts electricity.

Signal line: a number that sends a message.

Vcc: power supply layer, operating voltage. The working voltage of the earliest electronic products was mostly set as 12V. With the evolution of technology and the requirement of saving electricity, the working voltage gradually became 5V and 3V, and now it is gradually moving to 1V, and the requirement of copper foil is also getting higher and higher.

GND (Grounding) : Grounding ground. Vcc can be thought of as the water tower in the home, when we open the tap, through the water pressure (working voltage) will have water (electronics) flow out, because the action of electronic parts are determined by the flow of electrons; A GND is a drain. All the water that is used or unused goes down the drain. Otherwise the tap would keep draining and your home would flood.

Heat Dissipation (due to High thermal Conductivity) : Heat Dissipation. Have you heard of some CPU hot enough to boil eggs, this is not exaggerated, most of the electronic components will consume energy and generate heat, at this time need to design a large area of copper foil to release heat into the air as soon as possible, otherwise not only human can not tolerate, even the electronic parts will also follow the machine.

Reinforcement.

When selecting PCB reinforcement material, it must have the following excellent characteristics. Most of the PCB reinforcement materials we see are made of GF (Glass Fiber). If you look carefully, the material of Glass Fiber is a little like a very thin fishing line. Because of the following personality advantages, it is often used as the basic material of PCB.

High Stiffness: Makes PCB not easy to deform.

Dimension Stability: Good dimensional Stability.

Low CTE: provides Low “thermal expansion rate” to prevent the circuit contacts inside the PCB from disconnecting and causing failure.

Low Warpage: with Low deformation, that is, Low plate bending, plate warping.

High Modules: High Young’s modulus

3. Resin Matrix

Traditional FR4 boards are epoxy-dominated, LF (Lead Free)/HF (Halogen Free) boards are made of a variety of resins and different curing agents, making the cost of LF about 20%, HF about 45%.

HF plate is easy to crack and increase water absorption, thick and large plate is prone to CAF, it is necessary to use open fiber cloth, flat fiber cloth, and strengthen the material containing uniform immersion.

Good resins must have the following conditions:

Good Heat Resistance. Heat welding two to three times after the plate will not burst, is good heat resistance.

Low Water Absorption: Low Water Absorption. Water absorption is the main cause of PCB board explosion.

Flame Retardance: Must be Flame retarded.

Peel Strength: With high “tear Strength”.

High Tg: High glass state transition point. Most of the materials with high Tg are not easy to absorb water, and the basic reason for not exploding the board is not water absorption, rather than high Tg.

You said Toughness is great. The greater the toughness, the less explosive the board. The Toughness of the plate is called “fracture energy,” and the better the material is, the better it will be able to withstand impact and damage.

Dielectric properties: High Dielectric properties, i.e. insulating material.

4. Fillers System (powder, filler)

In the early stage of lead welding, the temperature was not very high, and the original PCB board was still bearable. Since the lead-free welding, the temperature increased, so the powder was added to the PCB board to make the PCB strongly resistant to temperature.

Fillers should be coupled first to improve dispersion and compactness.