Is it better to use mica sheet for the heat dissipation insulating sheet of the triode, or is it better to use a silicone pad
Oct 24, 2022
The installation of power amplifier power tubes (power devices) all need to install insulating sheets to isolate them from heat sinks (except for special circuit structures). Although there are all kinds of thermally conductive insulating sheets, there are basically only two types of thermally conductive insulating sheets used for the installation of power amplifier power tubes (power devices), namely mica insulating sheets and silicone (silica gel) insulating sheets. Among the two insulating sheets, the mica insulating sheet has the characteristics of good thermal conductivity, high voltage resistance and thinness. The mica insulating sheet in the picture is 0.06mm thin and 0.13mm thick. However, due to the high hardness of the mica insulating sheet, in order to ensure that the installation contact surface is consistent, it is generally used in conjunction with thermal grease. The purpose of applying thermal grease is to fill the gaps that may appear on the installation contact surface. The thinner the thermal grease, the better. It is enough to flatten the entire surface of the insulating sheet. Let's talk about the silicone (silicone) insulating sheet. Silicone (silica gel) insulating sheet has soft texture, strong plasticity, and its insulating performance can meet the requirements of installing power amplifier power tube insulation. It can be filled without applying thermal conductive silicone grease during installation. However, it is thicker, and the thickness of the silicone (silica gel) insulating sheet is about 0.3mm. For those with high requirements, a 0.15-thick silicone (silica gel) insulating sheet can be used. The usual usage is that there are more mica sheets for triodes and field tubes, and more silicone sheets for power integrated blocks.
It should be noted that mica will undergo cleavage under high temperature, so it is not suitable for too high temperature. There are different types of mica, and the cleavage temperature is also different. Generally, it is used below the red hot temperature.
Introduction of mica sheet material:
The mica flakes are composed of muscovite, quartz, garnet and rutile, among which albite, zoisite and hard chlorite can appear. Garnet is rich in Fe and Mg, and the Si in muscovite can reach 3.369. Also a high pressure combination. It has the function of insulation and low loss thermal resistance, and it is still a very good black body.
Mica and its products are widely used as insulating materials in electrical products. Its varieties are: natural mica, synthetic mica, mica tape, mica plate, mica foil, mica glass, etc.
