FR-4 epoxy sheet has excellent temperature resistance, and it is often used in various temperature-resistant occasions. Different environments require different grades of epoxy sheets.
The main materials of FR-4 epoxy sheet are glass fiber cloth and resin (mostly epoxy resin). In order to pursue the best product cost performance, different temperature-resistant FR-4 epoxy sheets can be selected for different use environments.
The temperature rating of common FR-4 epoxy sheet is divided into 8 levels, and the temperature resistance, winding temperature rise limit and performance reference temperature of each level are different. The eight temperature resistance levels are A, E, B, F, H, C, N, and R. Among them, the FR-4 epoxy sheet with the highest grade of R grade, and the FR-4 epoxy sheet with the lowest grade of A grade. Our common FR-4 epoxy sheets are class E and class B. See the FR-4 epoxy sheet temperature grade table below for details.
| Insulation temperature grade | A | E | B | F | H | C | N | R |
| Maximum allowable temperature (℃) | 105 | 120 | 140 | 155 | 180 | 200 | 220 | 240 |
| Winding temperature rise limit (K) | 60 | 75 | 80 | 105 | 125 | 135 | 150 | 170 |
| Performance reference temperature (℃) | 80 | 95 | 100 | 120 | 145 | 155 | 170 | 190 |
The corresponding limit operating temperature and normal operating temperature environment will be clearly marked in the electrical equipment when used. The supporting FR-4 epoxy sheet must be able to withstand the test of this temperature to ensure that it can work normally at this temperature for a long time. Do not cause the failure of the entire device because of the incompatible insulation grade.
In addition, the FR-4 epoxy sheet will lead to accelerated aging and failures due to the persistent work in a high temperature environment. It is very important to choose the appropriate FR-4 epoxy sheet.