A few things you must know about mica insulators in power devices
Oct 24, 2022
Today, let's talk about a small object - thermal insulation sheet. 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. Although ceramic has advantages in thermal conductivity and insulation, if it is only used in power amplifiers, it is not as good as mica and silica gel.
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. However, the mica sheet for electric heating is not suitable for the thermal insulation sheet of the power amplifier tube, because it is bonded by broken mica, only has insulating properties, and the thermal conductivity is not ideal, and there is no special mold for a large piece of mica sheet. Cropping is also difficult.
Let's talk about the silicone (silica gel) insulating sheet. Silicone (silica gel) insulating sheet has a soft texture, strong plasticity, and its insulation performance can meet the requirements of installing power amplifier power tube insulation. It can be filled without applying thermal conductive silicone grease during installation. But it is thicker, the thickness of the silicone (silica gel) insulating sheet in the picture is about 0.3mm. For those with high requirements, a 0.15-thick silicone (silica gel) insulating sheet can be used.
The above insulating sheets are all suitable for the installation of power amplifier power tubes (power devices), and the fact also shows that there is no example of burning the power amplifier due to the use of some kind of thermal insulating sheet.
