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• Fe-Ni film with smooth surface could be electrodeposited at high current density due to the reducing of internal stress of film by ultrasonic power. • The iron content, grain size, micro-hardness and Young's modulus of film all present an upward trend with ultrasonic power increases from 13 W to 93 W, and then a downward trend due to the intensively transient cavitation caused by higher ultrasonic power 120 W. • With the ultrasonic power of 93 W and current density of 1 A/dm2, a good surface quality of Fe-Ni films with 60.07 wt.% iron content, microhardness 351 HV, Young's modulus 167.5 GPa and CTE 3.38 × 10−6/°C can be electrodeposited. Fe-Ni alloy is considered as the most suitable metal for OLED mask making due to its excellent properties. However, electrodeposited Fe-Ni film is often companied with poor surface quality and thermal expansion. To get proper film for masks making, experiments of electroforming Fe–Ni were performed with different ultrasonic powers and current densities. Results show that Fe-Ni film with smooth surface could be electrodeposited at high current density due to the reducing of internal stress of film by ultrasonic power. The iron content, grain size, micro-hardness and Young's modulus of film all present an upward trend with ultrasonic power increases from 13 W to 93 W, and then a downward trend due to the intensively transient cavitation caused by higher ultrasonic power 120 W. With the ultrasonic power of 93 W and current density of 1 A/dm2, a good surface quality of Fe-Ni films with 60.07 wt.% iron content, microhardness 351 HV, Young's modulus 167.5 GPa and CTE 3.38 × 10−6/℃ can be electrodeposited. [ABSTRACT FROM AUTHOR]

• In this work, periodic ultrasound was introduced into the electroforming process to electrodeposit fe–ni foil layers with high properties and low coefficient of thermal expansion that satisfied the requirements for avionics packaging. The periodic ultrasound was realized by a time relay. T on represents the working time of the time relay, while t off is the off time. During T on , the ultrasonic transducer and the power supply are simultaneously active. Under the action of an electric field force and ultrasonic waves, the metal cations in solution are rapidly deposited on the surface of the cathode. During T off , the ultrasonic transducer is inactive, while the power supply continues to function. In this case, no ultrasound-assisted process is active on the surface of the cathode, and the metal cations in solution are deposited on the surface only under the action of the electric field. The infinite loop created by the t on and t off time relay enables intermittent ultrasound-assisted electrodeposition on the cathode surface. • Electrochemical analysis and morphological testing indicated that periodic ultrasonic can sufficiently weaken the stripping effect caused by continuous high-power ultrasonic treatment. Under periodic ultrasonic treatment, it is possible to apply both high current density and high ultrasonic power in the electroforming system. By adjusting the current density and the duty cycle, fe–ni deposits with coefficients of thermal expansion ranging from 2.96 to 6.71 × 10−6/°C were obtained. Compared to fe–ni alloys prepared via traditional electrodeposition methods, the fe–ni layers obtained in this study exhibit a larger range of CTE values and great improvements in other physical and mechanical properties. Periodic ultrasound was introduced into the electroforming process to electrodeposit Fe–Ni foil layers with high properties and low coefficient of thermal expansion that satisfied the requirements for avionics packaging. Electrochemical analysis and morphological testing indicated that periodic ultrasound can sufficiently weaken the stripping effect caused by continuous high-power ultrasonic treatment. Under periodic ultrasonic treatment, applying both high current density and high ultrasonic power in the electroforming system is possible. By adjusting the current density and the duty cycle, Fe–Ni deposits with coefficients of thermal expansion (CTEs) ranging from 2.96 to 6.71 × 10−6/ °C were obtained. Compared to Fe–Ni alloys prepared via traditional electrodeposition methods, the Fe–Ni layers obtained in this study exhibit a larger range of CTE values and great improvements in other physical and mechanical properties. The Fe–Ni alloy foil obtained at a duty cycle of 0.57 and current density of 1 A/dm2 possessed a low surface roughness of 0.95 μm, the iron content of 63 wt.%, micro-hardness of 373.1 HV, Young's modulus of 133.7 MPa, and CTE of 5.39 × 10−6/ °C. [Display omitted]. [ABSTRACT FROM AUTHOR]