What is the electrical performance of Parylene?
1. Electrical properties of Parylene coating
Parylene coating has excellent dielectric properties (Figure 1), as it can form a continuous homogeneous coating process and does not experience a decrease in dielectric strength due to defects and fillers caused by the process, unlike liquid coatings. Parylene coating has excellent insulation performance and is the preferred protective coating for insulation protection of electronic components. Parylene N and F8 have lower dielectric constants and dissipation factors, which can prevent signal absorption or loss, making them excellent protective coatings for MEMS, sensors, and other components.
2. Insulation impedance of circuit board
Parylene is a type of conformal coating material with excellent performance, which was first applied in the field of electronics after its introduction. Listed in the US military standard 46058C and the national military standard GJB150.7.1986, it is allowed to be used as a conformal coating material for military printed circuit boards, with a coating thickness of 0.0005-0.002 inches. As a protective coating for electronic circuits, Parylene does not require additional mold inhibitors and can achieve zero level mold resistance. In the salt spray experiment, compared with other coatings, the circuit resistance of Parylene protection hardly decreased, while other coatings showed a significant decrease. A very thin Parylene coating can provide good protective performance and facilitate the dissipation of heat during the operation of circuit boards. Therefore, as a protective coating, Parylene can make circuits more reliable, especially for the protection of small and high-density electronic circuits. Parylene also demonstrates its unique advantages (Figure 2).
Figure 1. Dielectric properties of Parylene
| performance | Parylene N | Parylene C | Parylene F4 | Parylene F8 | Epoxy resin ER | Silicone resin SR | Polyurethane UR | Polyacrylate AR | |
| Dielectric strength DC (V/mil) | 7000 | 5600 | 5300 | 5400 | 2200 | 2000 | 3400 | 3500 | |
| Surface resistance Ω· cm23 ℃ 50% RH | 1.4×10¹⁷ | 6~8×10¹⁶ | 1.4×10¹⁷ | 1.4×10¹⁷ | 1 0 ^ { 1 2 ~ 1 7 } | 1 0 ^ { 1 5 ~ 1 6 } | 1 0 ^ { 1 1 ~ 1 5 } | 1013~14 | |
| Volume resistance Ω | 10¹³ | 10¹⁴ | 10¹⁶ | 10¹⁶ | 10¹³ | 10¹³ | 10¹⁴ | 1¹⁴ | |
| dielectric constant | 60Hz | 2.65 | 3.15 | 2.20 | 2.21 | 3.5-5.0 | 2.7-3.1 | 5.3-7.8 | 3-4 |
| 1KHz | 2.65 | 3.10 | 2.25 | 2.20 | 3.5-4.5 | 2.6-2.7 | 5.4-7.6 | 2.5-5 | |
| 1MHz | 2.65 | 2.95 | 2.39 | 2.17 | 3.3-4.0 | 2.6-2.7 | 4.2-5.2 | 3-4 | |
| dielectric loss | 60Hz | 0.0002 | 0.020 | <0.0002 | 0.002-0.01 | 0.001-0.007 | 0.015-0.05 | 0.2-0.4 | |
| 1KHz | 0.0002 | 0.019 | 0.0013 | 0.0019 | 0.002-0.02 | 0.001-0.005 | 0.04-0.06 | 0.02-0.04 | |
| 1MHz | 0.0006 | 0.013 | 0.008 | 0.0010 | 0.03-0.05 | 0.001-0.002 | 0.05-0.07 | 0.035-0.056 | |
| 1GHz | 0.0043 | ||||||||
| 10GHz | 0.0032 | ||||||||
Figure 2. Parylene C coated circuit board alternating humidity test insulation electricity (Ω)
| Thickness (μ m) | Initial value 23 ° C50% RH | Pre cycle 23 ° C90% RH | Cycle 3 Step 565 ° C90% RH | Cycle 7 steps 565 ° C90% RH | Cycle 10 steps 725 ° C90% RH |
| 50 | 5.0×10¹⁴ | 4.2×10¹³ | 2.5×10¹² | 3.5×10¹¹ | 6.5×10¹² |
| 38 | 5.0×10¹⁴ | 4.4×10¹³ | 9.7×10¹¹ | 2.9×10¹¹ | 6.3×10¹² |
| 25 | 5.0×10¹⁴ | 1.2×10¹³ | 8.4×10¹¹ | 3.6×10¹¹ | 6.5×10¹² |
| 13 | 5.0×10¹⁴ | 3.6×10¹³ | 4.3×10¹² | 3.4×10¹¹ | 4.9×10¹² |
| 8 | 5.0×10¹⁴ | 2.9×10¹³ | 4.6×10¹² | 1.1×10¹¹ | 3.1×10¹² |
| 2.5 | 5.0×10¹⁴ | 3.5×10¹² | 1.8×10¹¹ | 1.3×10¹¹ | 2.8×10¹² |
