Low Dielectric Resins (2): Features that are often used in product development in the electrical and electronic field !!

5G is now leading the way and 6G development is unstoppable~

 

In high-frequency and high-speed environments, low dielectric materials are gradually receiving attention!!

 

5G is the abbreviation of the fifth generation communication. Through the characteristics of high frequency and short wavelength, it can achieve faster and lower delay transmission effect, which is about 10 times higher than 4G transmission speed. In the technology era where 5G is prevalent, the connected value chain spans across telecommunications services, 5G network equipment, 5G infrastructure, 5G semiconductors, 5G consumer goods, etc. Frequency characteristics and the resulting high heat dissipation and low loss requirements have gradually attracted attention.

 

▲In the era of high-speed transmission, many new technological applications have been born

 

Low dielectric materials

 

In the application field of 5G, the characteristics that attract the most attention at present are the dielectric constant and dissipation factor of materials. The dielectric constant is a physical quantity that characterizes the response of a material to an electric field. The lower it is, the less susceptible it is to being affected by an electric field. Materials with lower dielectric properties can produce less loss under high-frequency transmission such as 5G, reduce signal loss, and reduce the pressure on heating conditions and heat dissipation functions. For example, in the PCB industry, copper foil substrate (Copper Clad Laminate, CCL), which accounts for nearly half of the cost, can be used in the development of low-dielectric materials, which is also one of the current hot topics. The corresponding upstream materials may include low-dielectric resin, low-dielectric glass fiber material, and low-dielectric filling material. The following table lists possible potential materials for resin, reinforcing materials, and filler materials in low dielectric applications based on the main components of the copper foil substrate.

 

Application	Resins	Reinforcing materials	Fillers
FR-4	Epoxy resin, phenolic resin, polyamine formaldehyde	Glass fiber cloth	Silicon dioxide
Low dielectric substrate	Polyphenylene ether, polytetrafluoroethylene, petroleum resin, low dielectric epoxy	Low dielectric glass fiber	Hollow silicon dioxide, hollow acrylic microspheres, hollow glass microspheres

 

(Further Reading: What is a low dielectric material? Organic resin or inorganic filler, the original application is very different!!)

 

Dielectric constant and loss factor of various resins (thermoset, thermoplastic)

 

Since resin has many advantages, such as excellent chemical resistance, electrical insulation, adhesion, corrosion resistance, mechanical strength, ease of processing, etc., it also plays an important role in electronic-related applications. The following table shows the dielectric constants and loss factors of various common resin types. The most common epoxy and phenolic resins have the highest dielectric constants among them. Polyphenylene ether and tetrafluoroethylene have lower dielectric constants and are emerging materials favored by the trend of high-frequency transmission.

 

Resin	Dk (1 MHz)	Df (1 Mhz)
Phenolic resin	3.1-4.0	0.03-0.037
Epoxy resin	3.0-3.9	0.01-0.03
Cyanate resin	2.7-3.2	0.004-0.010
Silcone resin	2.8-2.9	0.002-0.006
Polymide (PI)	2.7-3.2	0.005-0.008
Bismaleimide (BMI)	2.8-3.2	0.005-0.007
Polyester resin	2.7-3.2	0.005-0.020
Hydrocarbon resin	2.2-2.6	0.001-0.005
Modified polyphenylene oxide (PPO)/ Polyphenylene ether (PPE)	2.45	0.0007-0.001
Polycarbonate (PC)	2.8-3.8	-
Cyclic olefin copolymer (COC)	2.3	0.00007
Poly(p-phenylene sulfide) (PPS)	3.0	0.002
Poly(ether sulfone) (PES)	3.5	0.003
Polysulfone (PSF)	3.0-3.2	-
Poly(ether ether ketone) (PEEK)	3.2	0.003
Polyphenylene sulfide (PPS)	3.4-3.5	-
Liquid crystal polymer (LCP)	2.9	0.002
Polystyrene (PS)	2.4-3.1*	0.0002(1GHz)*
Polyethylene (PE)	2.3-2.4*	-
Poly tetra fluoro ethylene (PTFE)	2.1	0.0004

(Development of Halogen Free, Low Loss Copper-Clad Laminates Containing a Novel Phosphonate Oligomer, Y. Qiang, 2016)

*(https://www.professionalplastics.com/, Electrical Properties of Plastics)

 

Comparsion of the dielectric constant (Dk) and loss factor (Df) between resins

 

If the resin is divided into thermosetting type and thermoplastic type, draw a graph according to its dielectric properties, as shown in the figure below. It can be found that common thermosetting resins, such as phenolic resins, polyimides, and epoxy resins, are all in the upper right of this figure in comparison, and their dielectric constants and dissipation factors are relatively high. Polycarbonate has a small dielectric constant but a high loss factor. However, polytetrafluoroethylene is a material with relatively low two values, so it has attracted special attention in the development of 5G low-dielectric materials. However, because the cost is still relatively expensive compared with other materials, it has not been widely used.

 

 

(Tanigawa, Takao et al. “Low Transmission Loss Film Material for High-Speed High-Frequency Devices.” 2018 IEEE 68th Electronic Components and Technology Conference (ECTC) (2018): 1757-1761.)

 

Low dielectric epoxy

 

At present, low-dielectric epoxy resins have been developed on the market, which can provide excellent chemical resistance, mechanical strength, and low dielectric properties at the same time. The main difference between low-dielectric epoxy resin and ordinary epoxy resin is their dielectric constant, which can meet the same requirements in the application of materials. Therefore, low-dielectric epoxy resin has better signal transmission efficiency and anti-interference ability, and is suitable for high-speed, high-frequency, and high-density electronic products. The dielectric constant of low-dielectric epoxy resin is generally around 3, while that of ordinary epoxy resin is generally around 4. The following table shows the relevant numerical differences between general type and low dielectric epoxy resin.

 

Item	General epoxy resin	Low dielectric epoxy	Low dielectric epoxy
Epoxy type	bisphenol A, BPA	Dicyclopentadiene, DCPD	polyphenylene oxide, PPO
Tg (oC)	168	169	160
Dk (10 GHz)	3.8	3.25	2.8
Df (10 GHz)	0.032	0.016	0.011
CTE (ppm/o C)*	-	54	-

*Hardener: Novolak, Catalyst: 2-Methylimidazole, Curing Condition: 170 ^oC dry 240 ^oC press

 

Plot the Dk/Df values ​​of various types of epoxy resins as shown in the figure below. It can be found that through the improvement of epoxy resin, the dielectric properties are gradually approaching the low dielectric polyphenylene ether resin, and it has the characteristics of epoxy. Low dielectric epoxy has broad development prospects. It will play a greater role in high-end application fields such as high-speed transmission and wireless communications.