Manufacture And Investigation Of High Temperature Co-fired Black Ceramic With High Insulation And Low Dielectric Loss

Because semiconductors are usually photosensitive,the package is required to be shaded,so the color of the high temperature co-fired ceramic in the ceramic package for semiconductor chips must be black.High temperature co-fired ceramic packaging is larger in the ceramic package of high reliability semiconductor.Alumina ceramics occupy most of the market share in high temperature co-fired ceramics,and black ceramic occupies a large proportion.There is a big gap between the technology and the international advanced level of the domestic high temperature co-fired black ceramic,but the foreign technical blockade makes the development of our country limited in this field.Therefore,it is of great significance to develop the high temperature co-fired black ceramic with high insulation and low loss.Al₂O₃ black ceramic usually adds transition element oxide as colorant,so its bulk resistivity is usually lower than that of white ceramic,while dielectric loss increases.The black ceramic used for high temperature co-fired ceramics must have the characteristics of high insulation and low loss,so the key to the practical application of the alumina black ceramic is to coordinate the relationship between the coloring effect and the electrical properties.In this paper,the oxides of Mo,Cr and Ti are used as colorants,and the use ratio of the oxide of Ti which has an influence on the electrical properties is controlled.The high temperature co fired black ceramic with high insulation and low loss is obtained.The following conclusions are drawn through the study.?1?By studying the action of solvent,binder,plasticizer,plasticizer,dispersant and inorganic powder in the casting paste,the proportion of ceramic paste is designed,in which the inorganic powder is Mo,Cr and Ti oxide as the colorant,the binder is PVB,the solvent uses anhydrous ethanol and butyl acetate,the plasticizer is DBP,and the ball mill is used.The ceramic paste with uniform dispersion and large particle agglomeration was obtained.Through the study of the drying mechanism of the casting and the problems in the drying,the drying parameters of the casting are determined and the qualified raw ceramic strip is cast out.The tensile strength of the raw ceramic belt is greater than 2MPa,which meets the requirements of the multi-layer ceramic process.?2?The green ceramic parts were prepared by multi-layer ceramic processing technology,and the problems of filling cracks,printing film thickness and printing precision in multi-layer ceramic processing were analyzed and verified by experiments.By improving the solid content of filling slurry,the problem of circular hole cracks in filling holes is solved.In the printing process,the scraper pressure should be less than 30 lbs,the pressure of the scraper should be less than 3in/s,the thickness of the film's photosensitive film is better than the 10³0 m,and the viscosity of the printing paste can guarantee the proper film thickness and printing precision when the viscosity of the printing paste is 50¹50kcps.?3?The alumina black ceramic samples were prepared by high temperature sintering.The sintering atmosphere was a mixed gas of hydrogen and nitrogen.Through the study of the sintering process,it was found that the appropriate heat preservation temperature of the furnace was 1575 C,compared with 25%,50%and 75%hydrogen content sintered samples,and the sintering atmosphere was found to contain 75%hydrogen.The amount is the best.The results of X ray diffraction?XRD?and scanning electron microscopy?SEM?show that the grain distribution of the ceramics is uniform,the grain diameter is about 2⁴?m,the crystalline phase of the ceramics is mainly-Al₂O₃,and there is a small amount of MgAl₂O₄ and MgCr₂O₄.spinel.The test results of the insulation resistance tester and vector network analyzer show that the Al₂O₃ black ceramic maintains the functional characteristics of high insulation and low loss,the bulk resistivity of the ceramic is greater than 10¹²?.m,the dielectric loss tan delta is less than 5 x 10^-3,which meets the requirements of the high frequency circuit within the frequency of 38GHz.?4?The plating and brazing technology of high temperature co-fired black ceramic package were studied.Nickel plated ceramic parts and metal parts can be obtained by electroless nickel plating,and metal parts and ceramic parts can be welded to form packages through brazing process.Through the analysis and experiment of the soldering material,it can be found that under the conditions of non nickel plating,nitrogen atmosphere and reasonable control of welding temperature,the wide band of the solder can be controlled within 0.20mm,and the multilayer ceramic shell with good appearance can be obtained.The volume resistivity and dielectric loss of the high temperature co-fired black ceramic have a great relationship with the addition of the coloring agent,especially the addition ratio of TiO₂ has an important influence on the electrical properties of the ceramics.It is found that when the weight percentage of TiO₂ in ceramics is less than 1%,the bulk resistivity of the ceramic is greater than10¹²?.m,and the dielectric loss is greatly reduced.This paper reduces the proportion of TiO₂ to less than 0.5%,and adds a proper amount of MoO₃ to the color of the black ceramic,which makes the black ceramic uniform in color.Moreover,the color of the black ceramic is uniform and mediate.The electrical loss is also reduced to less than 5×10^-3.