sales@ipcb.com
The laminates industry is located in the middle of the whole PCB industry chain, providing raw materials for the PCB industry. Laminates are made of electronic glass fibre cloth or other reinforcing materials impregnated with resin binder, dried, cut, stacked into blanks, covered with copper foil on one or both sides and hot pressed into a plate material. It is mainly used in the production of printed circuit boards (PCBs), and plays the role of interconnection, insulation and support for PCBs. The upstream of the industrial chain is electrolytic copper foil, wood pulp paper, glass fibre cloth, resin and other raw materials, the downstream of the PCB circuit board, the terminal industry for aviation, aerospace, automotive, home appliances, communications, computers, etc....
In 19 years, the initial commercialisation of 5G, core materials, high-frequency laminates and other products, upstream raw materials and traditional laminates are basically similar. After being produced by downstream PCB manufacturers as high-frequency circuit boards suitable for high-frequency environments, they are applied to base station antenna modules and power amplifiers. The modules and other equipment components are ultimately widely used in high-frequency communication fields such as base stations (antennas, power amplifiers, low-noise amplifiers, filters, etc.), automotive assistance systems, aerospace technology, satellite communications, satellite television, military radar, and other high-frequency communication fields.
5G high-frequency technology puts higher requirements on circuits. RF circuits with operating frequency above 1GHz are generally called high-frequency circuits. In the process of mobile communication from 2G to 3G and 4G, the communication frequency band has developed from 800MHz to 2.5GHz. In the 5G era, the communication frequency band will be further upgraded. PCBs will be equipped with antenna components, filters and other components for 5G RF. According to the requirements of MIIT, it is expected that the early deployment of 5G will use the 3.5GHz frequency band, while the 4G frequency band is mainly around 2GHz. Electromagnetic waves with a wavelength of 1-10 mm in the 30-300 GHz band are generally referred to as millimetre waves.
When 5G becomes commercially available on a large scale, millimetre wave technology guarantees better performance: extremely wide bandwidths, with up to 1 GHz of usable spectrum in the 28 GHz band, and up to 2 GHz of usable signal bandwidth per channel in the 60 GHz band. Corresponding antennas have high resolution, good interference immunity and can be miniaturised. Faster propagation attenuation in the atmosphere enables safe communication at close range.
In order to meet the demand for high-frequency and high-speed, as well as to cope with the problem of poor millimetre-wave penetration and fast attenuation, 5G communication equipment has the following three requirements for PCB performance:
1. Low transmission loss.
2. Low transmission delay.
3. High characteristic impedance precision control.
There are two ways to improve the frequency of PCB. One is to require a higher PCB processing technology, and the other is to use high-frequency laminates - to meet the high-frequency application environment of the substrate material is called high-frequency laminates.
The performance of high-frequency laminates is measured by the dielectric constant (Dk) and the dielectric loss factor (Df). The smaller and more stable Dk and Df are, the better the performance of the high frequency and high speed substrate. In addition, in the case of RF boards, the PCB boards are larger in size and have more layers, which requires higher heat resistance (Tg, Temperature Modulus Retention) and tighter substrate thickness tolerances.
There are several common high-frequency, high-speed materials for circuit boards: hydrocarbon resins, PTFE, LCP liquid crystal polymers, PPE/PPO, and so on.
High Frequency High Speed Circuit Boards
Hydrocarbon Resin
Hydrocarbon resins are polyolefin homopolymers or copolymers, including butadiene styrene copolymer, butadiene homopolymer, styrene homopolymer, styrene/divinylbenzene copolymer, styrene-butadiene-divinylbenzene copolymer and so on.
Excellent dielectric performance: Dk≈2.4/Df≈0.0002
Higher heat resistance
Good chemical resistance, poor adhesion
Polytetrafluoroethylene flexible film
PTFE resin has a relatively high melt temperature and melt viscosity. Common commercial forms are resin dispersions, resin suspensions and resin powders. Common processing methods are moulding/turning, batching/moulding, extrusion/moulding, etc.Due to the disadvantages of PTFE such as high coefficient of linear expansion and low thermal conductivity, it needs to be enhanced and modified. Modified film products usually y have: PTFE + ceramic,PTFE + glass fibre cloth,PTFE + ceramic + glass fibre cloth
LCP Liquid Crystal Polymers
Liquid Crystal Polymers, or LCP for short, is a new type of high-performance special engineering plastics developed in the early 1980s.
According to the different conditions of formation, liquid crystal can be divided into thermally molten thermogenic liquid crystal and solvent dissolved solvent liquid crystal.
After being melted or dissolved by solvent heating,this kind of material will lose the solid macroscopic size, shape, hardness, rigidity and other properties, and obtain the liquid material's fluidity in appearance, while maintaining the orientation and order of the crystalline material.... As a result, anisotropy is formed in the physical form, forming a transition state with both liquid fluidity and orderly arrangement of crystalline molecules. This intermediate form becomes the liquid crystal state.
From the molecular design point of view, there are three main types of commercial LCP:
One is the copolymerisation of polyphenylene ring rigid monomers.
The second is the introduction of naphthalene rings into the molecular structure.
The third is the use of aliphatic chains in the molecular chain.
Depending on the molecular structure, different types of LCP have different melting points.Generally speaking,their heat resistance is Type I > Type II > Type III.
PPE/PPO
Polyphenylene ether is a high-strength engineering plastic developed in the 1960s. Its chemical name is poly-2,6-dimethyl-1,4-phenylene ether, abbreviated as PPO (Polyphenylene Oxide) or PPE (Polyphenene ether), also known as polyphenylene ether or polyphenylene ether.
The two methyl groups block the active sites of the two neighbours of the phenol group, increasing its rigidity,stability,heat resistance and chemical resistance.
The ether bond increases flexibility but decreases heat resistance.
The two methyl groups are hydrophobic and non-polar groups, which reduce the water absorption and polarity of PPO molecule,and block the two active points of phenol group, so that there is no hydrolysable group in the structure of PPO molecule, and it has good water resistance and hygroscopicity. Good performance, dimensional stability and electrical insulation.A large number of rigid phenol-based aromatic rings, the rigidity of the molecular chain and the force between the molecular chain makes the molecular chain difficult to internal rotation, resulting in a rise in its melting point, melt viscosity,reduced mobility, processing difficulties.