Introduction
In the structural composition of connectors, although the insulating base (commonly known as the plastic housing) does not directly participate in electrical conduction, its importance cannot be ignored. Insulating materials not only determine key indicators such as mechanical strength, heat resistance, and insulation performance of connectors, but also directly affect product manufacturing costs and processing technology. LCP, PA6T, PA9T, and PBT are the four most commonly used engineering plastics in the connector industry, each with its own performance characteristics and applicable scenarios. This article provides a comprehensive comparison of these four materials from multiple dimensions such as heat resistance, mechanical properties, electrical properties, processing characteristics, and cost, providing a reference for connector selection.
1. PBT: The Cost-Effective Choice and Main Material for General Connectors
PBT (Polybutylene Terephthalate) is a representative polyester engineering plastic. With its good comprehensive performance and relatively low cost, it has become the most widely used insulating material in mid-to-low-end connectors.
Performance Characteristics of PBT
Heat Resistance: The long-term use temperature of PBT is approximately 120C-140C, and the heat deflection temperature (HDT, under 1.8MPa conditions) is approximately 55C-65C (unreinforced), which can be increased to over 200C after glass fiber reinforcement. For most indoor environments and general industrial applications, the heat resistance of PBT is sufficient to meet requirements.
Mechanical Properties: PBT has good mechanical strength and rigidity. After glass fiber reinforcement, tensile strength can reach over 130MPa, and bending strength can reach over 200MPa. However, its impact strength is relatively low, and it is more prone to brittle fracture at low temperatures and in notched conditions.
Electrical Properties: PBT has excellent insulation performance, with volume resistivity of over 10^16 ohm-cm, dielectric constant of approximately 3.0-3.5, low dielectric loss factor, and remains stable over a wide frequency range. It also has good arc resistance, making it suitable as an insulating material for low-voltage electrical appliances.
Chemical Resistance: PBT has good corrosion resistance to organic solvents, oils, weak acids, and weak bases, but is not resistant to strong acids, strong bases, and hot water hydrolysis. In high-temperature and high-humidity environments, the ester bonds of PBT are prone to hydrolysis, leading to performance degradation.
Processing Properties: PBT has good flowability, low molding shrinkage, good dimensional stability, and is easy to injection mold. It has fast crystallization speed, short molding cycle, and high production efficiency.
Applicable Scenarios and Cost of PBT
PBT is mainly used in general connector products with not very high heat resistance requirements, such as consumer electronics connectors, home appliance connectors, ordinary industrial connectors, etc. Products such as pin headers and female headers, wafer connectors, and simple wire-to-board connectors extensively use PBT material.
In terms of cost, PBT is the lowest among the four materials, with prices usually only 60%-70% of PA6T and 30%-50% of LCP. For cost-sensitive high-volume products, PBT has an extremely cost-effective advantage. For high cost-effective pin headers, female headers, and wafer products, you can refer to RXSY’s related product series, all using high-quality PBT material with reliable performance and optimized cost.
2. PA6T: Representative of High-Temperature Nylon, Balancing Performance and Cost
PA6T (Polyhexamethylene Terephthalamide) is a type of aromatic nylon, belonging to the high-temperature nylon family. Compared with traditional PA6 and PA66, PA6T has significantly improved heat resistance, dimensional stability, chemical resistance, etc., and is widely used in the field of high-temperature connectors.
Performance Characteristics of PA6T
Heat Resistance: The glass transition temperature (Tg) of PA6T is approximately 80C-100C, the melting point is approximately 320C, the heat deflection temperature (glass fiber reinforced) can reach over 280C, and the long-term use temperature can reach over 150C. Far superior to PBT and ordinary nylon, it can meet the temperature requirements of most lead-free soldering.
Mechanical Properties: PA6T has excellent mechanical properties. After glass fiber reinforcement, tensile strength can reach over 180MPa, and bending strength can reach over 250MPa. Its impact strength is also superior to PBT, with better toughness and less prone to brittle fracture.
Electrical Properties: PA6T has good electrical properties, but due to the presence of amide groups, its insulation performance is greatly affected by humidity. In the dry state, volume resistivity can reach over 10^15 ohm-cm, but after absorbing water, insulation resistance will decrease to some extent. Dielectric constant is approximately 3.5-4.0.
Chemical Resistance: PA6T has good corrosion resistance to oils, organic solvents, hydrocarbons, etc. Compared with PBT, PA6T has better hydrolysis resistance and higher performance retention in high-temperature and high-humidity environments. However, it is still subject to erosion by strong acids, strong bases, and phenolic solvents.
Water Absorption: As a nylon material, PA6T has higher water absorption than PBT and LCP, and water absorption will lead to dimensional changes and decreased mechanical properties. However, compared with ordinary nylons such as PA6 and PA66, PA6T’s water absorption has been greatly reduced.
Processing Properties: PA6T has a high processing temperature, usually between 310C and 340C. Melt flowability is good, but attention needs to be paid to controlling mold temperature and molding process to obtain good crystallinity and dimensional stability.
Applicable Scenarios and Cost of PA6T
PA6T is widely used in connector products requiring high temperature resistance, such as automotive connectors, industrial connectors, surface mount connectors, etc. For SMT connectors that need to pass reflow soldering, PA6T is a common material choice. Connectors in automotive engine compartments, industrial control equipment connectors, etc. also extensively use PA6T.
In terms of cost, the price of PA6T is between PBT and LCP, approximately 1.5-2 times that of PBT and 60%-80% of LCP. PA6T achieves a good balance between heat resistance and cost, making it one of the mainstream materials in the high-temperature connector field.
3. PA9T: High-Temperature Nylon with Better Performance
PA9T (Polynonamethylene Terephthalamide) is another important high-temperature nylon, first commercialized by Kuraray of Japan. Compared with PA6T, PA9T has more excellent performance in terms of water absorption, dimensional stability, chemical resistance, etc., and is one of the preferred materials for high-performance connectors.
Performance Characteristics of PA9T
Heat Resistance: The melting point of PA9T is approximately 308C, the heat deflection temperature (glass fiber reinforced) can reach over 270C, and the long-term use temperature can reach over 150C. Heat resistance is comparable to PA6T, slightly lower than LCP, but far superior to PBT.
Low Water Absorption: The biggest advantage of PA9T is its low water absorption, one of the lowest water absorption rates among all high-temperature nylons, only about 1/3 of PA6T. Low water absorption means good dimensional stability, small dimensional changes after water absorption, and electrical properties less affected by humidity. This feature makes PA9T have obvious advantages in precision connectors and high-humidity environment applications.
Mechanical Properties: PA9T has excellent mechanical strength and toughness. After glass fiber reinforcement, tensile strength can reach over 200MPa. Especially in high-temperature environments, PA9T’s mechanical property retention rate is superior to PA6T.
Electrical Properties: Due to low water absorption, PA9T’s electrical properties are more stable. Even in high-humidity environments, insulation resistance and dielectric properties can be maintained at a high level. It also has a high Comparative Tracking Index (CTI), suitable for high-voltage application scenarios.
Chemical Resistance: PA9T has excellent chemical corrosion resistance, with good tolerance to various solvents, oils, acids, and bases. Especially outstanding in gasoline and engine oil resistance, very suitable for oil mist environments such as automotive engine compartments.
Processing Properties: PA9T has a wide processing temperature range, good melt stability, and is easy to injection mold. Compared with PA6T, PA9T has better moldability and is less prone to burrs.
Applicable Scenarios and Cost of PA9T
PA9T is mainly used in high-end connectors with high requirements for dimensional stability and moisture resistance, such as automotive electronics connectors, high-speed connectors, precision board-to-board connectors, etc. For products that need to maintain stable performance in humid environments, PA9T is an ideal choice.
In terms of cost, the price of PA9T is slightly higher than PA6T, approximately 1.1-1.3 times that of PA6T. Although the cost is slightly higher, its excellent low water absorption characteristics and dimensional stability make PA9T’s comprehensive performance superior in many high-end applications.
4. LCP: High-Performance Liquid Crystal Polymer
LCP (Liquid Crystal Polymer) is a high-performance special engineering plastic with a unique liquid crystal structure. In the molten state, molecules are oriented, giving it excellent properties. LCP is the preferred material for high-end connectors, especially miniaturized and high-precision connectors.
Performance Characteristics of LCP
Heat Resistance: The heat resistance of LCP is very excellent. Depending on the grade, the heat deflection temperature can reach 250C-350C, and the long-term use temperature can reach 180C-260C. It can easily handle the high-temperature requirements of lead-free reflow soldering, and can even withstand multiple reflow soldering cycles.
Mechanical Properties: LCP has the characteristics of high strength and high modulus. Tensile strength can reach over 150MPa, and bending strength can reach over 200MPa. More importantly, LCP has a high mechanical property retention rate at high temperatures, and can still maintain good rigidity at temperatures close to the melting point.
Dimensional Stability: LCP has extremely low molding shrinkage, and although anisotropy exists, it can be controlled through reasonable mold design. Water absorption is extremely low, almost negligible, so dimensional stability is excellent, making it very suitable for manufacturing precision miniature connectors.
Electrical Properties: LCP has excellent electrical properties, maintaining stable dielectric properties even in the high-frequency range. Low dielectric constant (approximately 3.0) and small dielectric loss factor make it an ideal insulating material for high-speed connectors and high-frequency connectors. LCP has high insulation resistance and good arc resistance, and is widely used in the electronic and electrical fields.
Chemical Resistance: LCP has excellent corrosion resistance to most chemicals, resistant to strong acids, strong bases, organic solvents, etc. It has stable performance in high-temperature and high-humidity environments and is almost unaffected by hydrolysis.
Processing Properties: LCP has excellent melt flowability and strong filling ability, capable of molding products with extremely thin walls and high precision, which is also an important reason why it is suitable for miniature precision connectors. However, the anisotropy of LCP needs to be considered during design and molding to avoid warpage and strength directionality problems caused by molecular orientation.
Applicable Scenarios and Cost of LCP
LCP is mainly used in the field of high-end precision connectors, including: FPC connectors, board-to-board connectors, high-speed connectors, RF connectors, automotive electronics connectors, etc. Especially for precision connectors with fine pitch of 0.5mm and below, almost all use LCP material, because PBT and PA6T have difficulty meeting such high precision and high heat resistance requirements.
In terms of cost, LCP is the most expensive of the four materials, with prices usually 2-4 times that of PBT and 1.5-2.5 times that of PA6T. The high cost limits the application of LCP in mid-to-low-end products, but in the field of high-end and precision connectors, LCP’s performance advantages make it irreplaceable.
5. Comprehensive Comparison and Selection Recommendations
| Performance Dimension | PBT | PA6T | PA9T | LCP |
|---|---|---|---|---|
| Long-term Use Temperature | 120C-140C | 150C+ | 150C+ | 180C-260C |
| Heat Deflection Temperature (GF) | ~200C | ~280C | ~270C | 250C-350C |
| Mechanical Strength | Medium | High | High | High |
| Dimensional Stability | Medium | Medium | Good | Excellent |
| Water Absorption | Low | Medium | Low | Extremely Low |
| Electrical Properties | Good | Good (affected by humidity) | Good | Excellent (excellent high-frequency performance) |
| Chemical Resistance | Average | Good | Excellent | Excellent |
| Processing Flowability | Good | Relatively Good | Good | Excellent |
| Price Level | Low | Medium | Medium-High | High |
| Typical Applications | General connectors, pin headers/female headers | Automotive connectors, industrial connectors | High-end automotive connectors, precision connectors | Precision FPC/BTB, high-speed connectors |
When selecting, comprehensive consideration can be made from the following dimensions:
1. Operating Temperature: First, screen materials based on the maximum operating temperature of the connector. PBT for general applications, PA6T or PA9T for around 150C, LCP for higher temperatures or requiring multiple reflow soldering.
2. Precision Requirements: The smaller the pitch and the more precise the structure of the connector, the higher the requirements for dimensional stability and molding ability of the material. Above 0.8mm pitch, PBT or PA6T can be considered; for fine pitch of 0.5mm and below, LCP is preferred.
3. Environmental Humidity: If the product is used in a high-humidity environment, low water absorption materials such as PA9T or LCP should be prioritized to avoid dimensional changes and performance degradation due to water absorption.
4. Electrical Performance Requirements: LCP is the first choice for high-frequency and high-speed applications, and its excellent high-frequency dielectric properties are difficult to replace with other materials. PBT or PA series can meet general signal transmission requirements.
5. Cost Budget: On the premise of meeting performance requirements, prioritize selecting lower cost materials. PBT has the highest cost-effectiveness, PA6T balances performance and cost, and LCP is suitable for high-end high-performance applications.
Conclusion
The selection of connector insulating materials needs to be combined with specific application scenarios to find the best balance between heat resistance, mechanical properties, electrical properties, processing characteristics, and cost. PBT dominates the general connector market with high cost-effectiveness, PA6T and PA9T each have their strengths in the high-temperature field, and LCP leads the development of high-end precision connectors with excellent comprehensive performance.
RXSY reasonably selects materials in product design according to different application scenarios, ensuring that each product achieves an optimal balance between performance and cost. For more information on connector material selection and product information, please refer to the RXSY product series. We will provide you with professional technical support and high-quality product solutions.
