METHODS OF METALIZATION OF CERAMICS USED IN PRODUCTION OF POWER ELECTRONIC MODULES AND ELECTRIC VACUUM DEVICES

Power electronic modules are used in engineering related to the need to transmit high-current signals. Typical areas of application of such modules are aircraft navigation systems, elements of switching power circuits and other high-load connections. The central unit of the module is a ceramic base, on which conductive tracks are formed and electronic components are mounted. The finished substrate is often called a switchboard. The substrate performs two main functions: Is the dielectric basis of the printed circuit formed on one or two sides. Provides heat dissipation emitted by semiconductor crystals and circuit elements. Used for substrates non-hygroscopic ceramics, heat-resistant, is an insulating material with high mechanical and dielectric properties. It is relatively easy to manufacture and low cost. In the manufacture of power modules using ceramic substrates of aluminum oxide or nitride with a multilayer metallized coating with a thickness of several microns to several tens of microns (depending on the application), which provides the required degree of adhesion of the coating to ceramics and applied on one or both sides. The main requirements for the finished product are the minimum dimensions and low cost of materials and production process. In addition, the decisive factors are high technical characteristics, resistance to environmental influences and reliability. The design of the finished module must provide minimum values of transient thermal resistances, distributed inductances of power busbars, high insulation voltage. Adhesion strength depends on many factors: coating technology, film material, substrate material; and may decrease during operation of the finished product. During the operation of power modules, they are subjected to thermal and mechanical loads, including vibration. This leads to the destruction of components from overheating and damage to the mechanical damage of the modules. Often the failure occurs in the structure of the substrate-coating conductor. The main reason for this destruction is the low adhesive strength of the metal film to the ceramic base.

The Efficiency of Tribocoupling with МоS2-Based Solid Lubricant Coatings Using Magnetron and Suspension Sputtering

An analysis of studies conducted under vacuum conditions revealed that MoS2-based solid lubricant coatings applied to a titanium base using magnetron sputtering was virtually unusable. It was established that satisfactory working capacity of the considered couplings could be achieved by preliminary treatment of the base, that is by galvanic chrome plating and nickel plating. It was shown that life of a coupling with solid lubricant coatings sputtered using the magnetron method on a ceramic base was higher than those sputtered on a metal base. However, starting from the middle of operational life, temporary “surges” in the coefficient of friction occurred and subsequently stabilized. The life of coatings sputtered using the magnetron method was 2.51 times lower than that of a coupling with coatings of the BNII NP 212 type obtained using the suspension method, and 3.65 times lower than that of similar types by foreign manufacturers. The coefficient of friction for the considered couplings under vacuum conditions varied from 0.02 to 0.07.

Unconventional processes of ceramic and composite materials shaping

In order to reach the high quality parts of machines or tools very often ceramic or composite materials on metalic or ceramic base are being applied. Efficient shaping above mentioned materials using cutting or classical grinding is difficult because of their high mechanical properties. Rational solution is application of unconventional machining methods as: electrochemical, electrodischarge or electrochemical – electrodischarge (ECDM) in case when machined materials are at least partly conductive of electrical current. In case of shaping ceramic materials unconductive for electrical current the rational solution can be application of Spark Assisted Chemical Engraving (SACE) process – the special kind of ECDM process.