# Connector insulation material selection: LCP, PA6T, PA9T, PBT performance and cost comparison
In the structural composition of the connector, although the insulating base (commonly known as the plastic shell) is not directly involved in electrical conduction, its importance cannot be ignored. Insulation materials not only determine the mechanical strength, heat resistance, insulation performance and other key indicators of the connector, but also directly affect the manufacturing cost and processing technology of the product. 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 paper comprehensively compares these four materials from multiple dimensions such as heat resistance, mechanical properties, electrical properties, processing characteristics, and cost, providing a reference for connector selection.
# # First, PBT: cost-effective choice, the main material of universal connector
PBT (polybutylene terephthalate) is a representative of polyester engineering plastics and has become the most widely used insulating material in low-end connectors with good comprehensive performance and low cost.
# # # Performance characteristics of PBT
* * Heat resistance * *: The long-term use temperature of PBT is about 120 ℃ ~ 140 ℃, and the thermal deformation temperature (HDT, 1.8MPa) is about 55 ℃ ~ 65 ℃ (unreinforced), which can be increased to more than 200 ℃ after glass fiber reinforcement. For most indoor environments and general industrial applications, PBT is heat resistant enough to meet the requirements.
* * Mechanical properties * *: PBT has good mechanical strength and rigidity, the tensile strength after glass fiber reinforcement can reach more than 130MPa, and the bending strength can reach more than 200MPa. However, its impact strength is relatively low, and it is more prone to brittle fracture at low temperatures and notches.
* * Electrical performance * *: PBT has excellent insulation performance, volume resistivity can reach more than 10 ^ 16Ω · cm, dielectric constant is about 3.0~3.5, dielectric loss factor is low, and it remains stable in a wide frequency range. Arc resistance is also good, suitable as an insulating material for low-voltage electrical appliances.
* * Chemical resistance * *: PBT has good corrosion resistance to organic solvents, greases, weak acids, weak bases, etc., 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, resulting in degraded performance.
* * Processability * *: PBT has good fluidity, small molding shrinkage, good dimensional stability, and easy injection molding. The crystallization speed is fast, the forming cycle is short, and the production efficiency is high.
# # # Applicable scenarios and costs of PBT
PBT is mainly used in general-purpose connector products that do not require high heat resistance, such as consumer electronics connectors, home appliance connectors, general industrial connectors, etc. A large amount of PBT materials are used in products such as pin headers, Wafer hubs, and simple wire-to-board connectors.
In terms of cost, PBT is the lowest of the four materials, and the price is usually only 60% -70% of PA6T and 30% -50% of LCP. For cost-sensitive, high-volume products, PBT offers great value for money. For cost-effective needle row headers and Wafer products, refer to the relevant product line of Rui Xinsheng Industry, which uses high-quality PBT materials for reliable performance and cost optimization.
# # II. PA6T: Representatives of high-temperature nylon, balancing performance and cost
PA6T (polyhexylene terephthalamide) is a type of aromatic nylon that belongs to the high-temperature nylon family. Compared with the 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 about 80 ℃ ~ 100 ℃, the melting point is about 320 ℃, the thermal deformation temperature (glass fiber reinforced) can reach more than 280 ℃, and the long-term use temperature can reach more than 150 ℃. Much better than PBT and ordinary nylon, able to meet the temperature requirements of most lead-free welding.
* * Mechanical properties * *: PA6T has excellent mechanical properties, the tensile strength after glass fiber reinforcement can reach more than 180MPa, and the bending strength can reach more than 250MPa. Impact strength is also superior to PBT, with better toughness and less brittle fracture.
* * Electrical properties * *: PA6T has good electrical properties, but its insulation properties are greatly affected by humidity due to the presence of amide groups. In the dry state, the volume resistivity can reach more than 10 ^ 15Ω · cm, but the insulation resistance will decrease after absorbing water. The dielectric constant is about 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 eroded by strong acids, strong bases, and phenolic solvents.
* * Water absorption * *: As a nylon material, PA6T has a higher water absorption rate than PBT and LCP, resulting in dimensional changes and decreased mechanical properties after water absorption. However, compared to ordinary nylon such as PA6 and PA66, the water absorption rate of PA6T has been greatly reduced.
* * Processability * *: The processing temperature of PA6T is high, usually between 310 ℃ and 340 ℃. The fluidity of the melt is good, but attention needs to be paid to controlling the mold temperature and the molding process to obtain good crystallinity and dimensional stability.
# # # Applicable scenarios and costs of PA6T
PA6T is widely used in connector products that require high temperature resistance, such as automotive connectors, industrial connectors, surface mount connectors, etc. For SMT connectors that require reflow soldering, PA6T is a common material choice. Connectors in automotive engine compartments, industrial control equipment connectors, etc. also use PA6T extensively.
In terms of cost, the price of PA6T is between PBT and LCP, which is about 1.5 to 2 times that of PBT and 60% to 80% that of LCP. PA6T has achieved a good balance between heat resistance and cost, and is one of the mainstream materials in the field of high-temperature connectors.
# # III. PA9T: High-temperature nylon with better performance
PA9T (poly (azonyl-phenylenediamine)) is another important high-temperature nylon that was first commercialized by the Japanese company Coraline. Compared with PA6T, PA9T has better 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 about 308 ℃, the thermal deformation temperature (glass fiber reinforced) can reach more than 270 ℃, and the long-term use temperature can reach more than 150 ℃. 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 rate, which is one of the lowest among all high-temperature nylons, only about 1/3 of that of PA6T. Low water absorption means that the dimensional stability is good, the dimensional change after water absorption is small, and the electrical performance is less affected by humidity. This feature gives the PA9T a distinct advantage in precision connector and high humidity applications.
* * Mechanical properties * *: PA9T has excellent mechanical strength and toughness, and the tensile strength after glass fiber reinforcement can reach more than 200MPa. Especially in high temperature environment, the mechanical property retention rate of PA9T is better than that of PA6T.
* * Electrical performance * *: PA9T has more stable electrical performance due to low water absorption. Insulation resistance and dielectric properties can be maintained at high levels even in high humidity environments. The leakage resistant trace index (CTI) is also high, which is suitable for high-voltage applications.
* * Chemical resistance * *: PA9T has excellent chemical corrosion resistance and good resistance to various solvents, oils, acids and bases. In particular, it has outstanding resistance to gasoline and oil, making it ideal for oil mist environments such as automobile engine compartments.
* * Processability * *: PA9T has a wide processing temperature range, good melt stability, and easy injection molding. Compared with PA6T, PA9T has better formability and is less prone to burrs.
# # # Applicable scenarios and costs of PA9T
PA9T is mainly used in high-end connectors with high requirements for dimensional stability and moisture resistance, such as automotive electronic connectors, high-speed connectors, and precision board-to-board connectors. The PA9T is ideal for products that require stable performance in humid environments.
In terms of cost, the price of PA9T is slightly higher than that of PA6T, which is about 1.1 to 1.3 times that of PA6T. Although the cost is slightly higher, its excellent low water absorption characteristics and dimensional stability make the PA9T a better overall performer in many high-end applications.
# # IV. LCP: High-performance liquid crystal polymer
LCP (liquid crystal polymer) is a high-performance special engineering plastic with a unique liquid crystal structure, and molecules are oriented in the molten state, giving it excellent performance. LCP is the material of choice for high-end connectors, especially miniaturized, high-precision connectors.
# # # Performance characteristics of LCP
* * Heat resistance * *: LCP has excellent heat resistance. Depending on the grade, the thermal deformation temperature can reach 250 ℃ ~ 350 ℃, and the long-term use temperature can reach 180 ℃ ~ 260 ℃. Can easily cope with the high temperature requirements of lead-free reflow soldering, and can even withstand multiple reflow soldering.
* * Mechanical properties * *: LCP has the characteristics of high strength and high modulus, the tensile strength can reach more than 150MPa, and the bending strength can reach more than 200MPa. More importantly, LCP retains a high rate of mechanical properties at high temperatures and retains good rigidity at temperatures close to the melting point.
* * Dimensional stability * *: The molding shrinkage of the LCP is extremely low, and although anisotropy exists, it can be controlled by a reasonable mold design. The water absorption rate is very low and almost negligible, so the dimensional stability is excellent and it is very suitable for manufacturing sophisticated small connectors.
* * Electrical performance * *: LCP has excellent electrical performance and maintains stable dielectric performance in the high frequency range. Low dielectric constant (about 3.0) and low dielectric loss factor make it an ideal insulating material for high-speed and high-frequency connectors. LCP has high insulation resistance and good arc resistance, and is widely used in electronic and electrical fields.
* * Chemical resistance * *: LCP has excellent corrosion resistance to most chemicals, strong acid, strong alkali, organic solvents, etc. Stable performance in high temperature and high humidity environment, almost unaffected by hydrolysis.
* * Processability * *: LCP has excellent melt flowability, strong filling capacity, and the ability to form products with extremely thin wall thickness and high precision, which is also an important reason for its suitability for small precision connectors. However, the anisotropy of LCP requires attention when designing and molding to avoid warping and strength directional issues due to molecular orientation.
# # # Applicable scenarios and costs 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 electronic connectors, etc. In particular, precision connectors with a small pitch of 0.5mm and below are almost all made of LCP materials, because PBT and PA6T are difficult to meet such high precision and high heat resistance requirements.
In terms of cost, LCP is the most expensive of the four materials, and the price is usually 2 to 4 times that of PBT and 1.5 to 2.5 times that of PA6T. The high cost limits the application of LCP in low- and medium-end products, but in the field of high-end and precision connectors, the performance advantages of LCP make it irreplaceable.
# # V. Comprehensive Comparison and Selection Suggestions
| Performance Dimension | PBT | PA6T | PA9T | LCP |
|———|—–|——|——|—–|
| Long Term Use Temperature | 120°C ~ 140°C | 150°C + | 150°C + | 180°C ~ 260°C |
| Thermal deformation temperature (glass fiber reinforced) | ~ 200°C | ~ 280°C | ~ 270°C | 250°C ~ 350°C |
| Mechanical Strength | Medium | High | High | High |
| Dimension stability | Medium | Medium | Good | Excellent |
| Water Absorption | Low | Medium | Low | Very Low |
| Electrical performance | Good | Good (affected by humidity) | Good | Excellent (excellent high-frequency performance) |
| Chemical resistance | Moderate | Good | Excellent | Excellent |
| Processing Fluidity | Good | Good | Good | Excellent |
| Price Level | Low | Medium | Medium High | High |
| Typical Applications | Universal Connectors, Pin Headers | Automotive Connectors, Industrial Connectors | High-End Automotive Connectors, Precision Connectors | Precision FPC/BTB, High-Speed Connectors |
When selecting a model, you can comprehensively consider the following dimensions:
* * 1. Operating Temperature * *: First screen the material according to the maximum operating temperature of the connector. Generally, PBT is selected, PA6T or PA9T is selected at around 150 °C, and higher temperatures or multiple reflow soldering of LCP is required.
* * 2. Precision requirements * *: The smaller the pitch and the more precise the structure of the connector, the higher the requirements for the dimensional stability and molding ability of the material. PBT or PA6T can be considered above 0.8mm, and LCP is preferred for small pitches of 0.5mm and below.
* * 3. Ambient humidity * *: If the product is used in a high humidity environment, low water absorption materials such as PA9T or LCP should be preferred to avoid dimensional changes and performance degradation due to water absorption.
* * 4. Electrical performance requirements * *: LCP is preferred 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 be used for general signal transmission.
* * 5. Cost budget * *: Prioritize lower-cost materials to meet performance requirements. PBT is the most cost-effective, PA6T balances performance and cost, and LCP is suitable for high-end and high-performance applications.
Conclusion
The selection of connector insulation 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 occupies the general-purpose connector market with high cost performance, PA6T and PA9T have their own strengths in the field of high temperature, and LCP leads the development of high-end precision connectors with excellent comprehensive performance.
In product design, Ruixin Shengye reasonably selects materials according to different application scenarios to ensure that each product can achieve an optimal balance between performance and cost. For more information on connector material selection and product information, please refer to the Rui Xin Sheng Ye product line, we will provide you with professional technical support and quality product solutions.
