How to choose and use thermal grease correctly?

How to choose a suitable silicone grease?

How to choose CPU and GPU?

How to choose IGBT?

IGBT generally requires a relatively large coating area, and the flatness limitation of the large size makes it impossible to obtain a relatively low BLT. At this point, the main choice should be silicone grease with high thermal conductivity to achieve low thermal resistance, while small-sized IGBTs can use thermal resistance as the main reference.

How to choose a bare die application?

The main feature of bare die is that it is easy to pump out, and the chip can withstand low stress, so of course, the one with good pumping out and flowability should be selected. Currently, there are no pumps available on the marketsilicone greaseBasically none, only slow and fast pumping. Later, I will have the opportunity to introduce a thermal grease that we have developed specifically for bare die applications without pumping out.

LED lamp

How to use silicone grease?

The poor use of silicone grease is mainly reflected in the usage process. The general thickness of silicone grease used is about 0.1mm, which is equivalent to the thickness of a piece of paper. Such thinness can easily cause an increase in thermal resistance. One is uneven brushing, with pores between interfaces; The second reason is that brushing too much results in thicker keys and lines (BLT). When the flatness control of interface devices is poor, it can also cause a rapid increase in interface thermal resistance.

The most commonly used methods for silicone grease include printing and dispensing. Printing is divided into types such as wire mesh, steel mesh, and steel plate, with the difference being the "mold" used for printing, collectively referred to as wire mesh.

There are many factors that affect the brushing effect during printing, and various factors have a significant impact on the brushing effect. It is necessary to choose a suitable printing process for our company.

The recommended mesh size for the wire mesh is 60-80 mesh, and the steel plate thickness is 0.1-0.3mm. The material of the wire mesh is generally nylon, and the thickness of the brush coating is directly related to the mesh size of the wire mesh. The larger the mesh size, the lower the thickness of the wire mesh, and the lower the brush coating thickness. The thickness of the brush coating can be measured using a wet film gauge or a height block.

Low brush coating thickness is beneficial for achieving low Bond Line Thickness (BLT), which can effectively reduce the thermal resistance of silicone grease.

The optimal gap height between the wire mesh and the base is 1-3mm. Too low a height can make it difficult to separate the mesh from the base plate, while too high can increase the required brushing force.