Research On Electrodeposited Copper Filling Microvias And Its Application In High Power Package Substrate

As the device density in the chip gradually approaches the physical limit,the denser transistor arrangement of the chip and the increase of the operating frequency and bandwidth bring a greater heat dissipation burden.The package substrate is used as a bridge for the electrical interconnection between the chip and the printed circuit board.The copper column array made in the package substrate by the electrodeposited copper through-hole filling technology can greatly improve the heat dissipation rate of the package substrate,which is a research hotspot in the current packaging technology field.However,it is very difficult to achieve perfect filling without voids in the hole,and it is even more difficult to ensure the requirement of fine electronic circuits fabrication on the surface after filling the hole.In this paper,a commercial additive was taken as the research object,and the influence of key factors such as current density,gas flow rate,sulfuric acid concentration and chloride ion concentration on electrodeposition filling was studied through single-factor experiments.Then,the influence degree of each component and concentration of additives on the electroplating hole filling performance was studied by orthogonal test.In order to further study the action mechanism of additives in hole filling,The electrochemical properties of hole-filling additives were analyzed by GM and CV electrochemical tests on commercial additive components and developed organic additive components,and were verified by simulation models and electroplating experiments.Finally,a secondary etching technology is proposed to realize the fabrication of fine electronic circuits after filling holes,and completing the filling of the through holes to fabricate the copper pillar array improves the heat dissipation rate of the package substrate.The specific research contents are as follows:1.The effect of different plating parameters on electroplating filling holes was studied by single factor experiment method.Plating the thickness 0.2mm,hole diameter0.2mm test board with hole filling,The optimum current density obtained was 0.9 A/dm~2;the optimum air flow rate was 0.5 L/min;the optimum concentration of sulfuric acid was50 g/L;and the optimum concentration of chloride ion was 60 mg/L.Then,the influence of different components and concentrations of commercial additives on hole filling was studied through 3-factor and 4-level orthogonal experiments.Taking the ratio of the copper deposition thickness at the orifice and the hole center as the index,the influence of different components of additives on the hole filling is obtained through the range analysis.The order of influence of different components of additives on the effect of electroplating through hole filling is obtained:leveler>accelerator>inhibitor.2.From the commercial additive GM test,it can be seen that the final potential difference is larger at high speed and low speed,and from the CV results,it can be seen that the plating solutions with different concentrations of leveling agent have the characteristics of"convection-dependent adsorption"for different convection conditions.The self-developed additive formula SH110+PEG+JGB was screened out with good super-filling ability.Its electrochemical properties are similar to those exhibited by commercial additives.The hole filling performance of the hole filling additive is further verified by the simulation model and the overfilling results of the Haring cell electroplating experiment.3.The secondary etching technology of the metal tin buffer layer is proposed to realize the production of fine lines after the surface copper is thinned.Compared with direct etching,the surface copper roughness R_a obtained by this method is reduced by0.371μm,and the R_z is reduced by 1.713μm,which meets the requirements of fine circuit fabrication.By comparing the heat dissipation effect of the base plate and the copper column array board,the heat dissipation effect of the copper column array is significantly improved.The maximum heat flux density is 71.66 W/cm~2 under the heat source 120℃,which can be used as an excellent heat dissipation structure in the package substrate.