SU554117A1 - Ultrasonic welding method - Google Patents

Description

from / min, TO / min; in fig. 3 - curves of the dependence of the strain rate of the output and strength of welded joints for separation from time. Repeated amnlitud change during welding from | max. permits one to control the average power released in the welding zone, per one modulating voltage period. In this case, the peak power remains unchanged, pre-set. This allows for high peak acoustic powers to obtain a small average power introduced into the contact zone during welding. It can be seen from the graph of amnlituds that in one period of modulating voltage, the amplitude g changes twice from ~ 0 to max. This is achieved by changing the oscillator frequency deviation from / max to / min. (fit. 1) relative to the frequency of mechanical resonance (/ m.r.) welding system. With a smooth change in the lower limit of the generator frequency from / min to / MIN2, the duration of each change in amplitude from "O to | x. increases at frequency / min, they merge (Fig. 2). In this case, the average power released in the weld zone reaches its maximum value.

Example. The aluminum strip output is welded from material grade A-995 with a cross section of 250 x 18 µm with an aluminum film. The film is applied to monocrystalline silicon by resistive evaporation of aluminum. In a vacuum of 10 mm Hg. Art. Before welding, diffusion annealing of the hardening is carried out in an atmosphere of hydrogen at 350 ° C for 30 minutes. The terminals are connected to the contact pad at optimally selected values of the loading force (, 65; n) and the amplitude of the tool oscillations (2 µm). During the welding process, the change in the width of the ribbon output in the weld zone is measured at regular intervals and then the strain rate is calculated. Simultaneously with the tape deformation measurement, the strength of the welded joints (Q) is monitored in the weld zone. Graph of strain rate (Vi) output (curve 1)

and the strength of welded joints, the gap (curve 2) from time to time proves that the stages of formation of joints are not merged, but occur sequentially. At the initial moment in time (/ O-0.12 sec.), The deformation of the output increases, since under the action of the loading force and ultrasonic vibrations the tool engages with the output. Next (/ 0.12-0.3 sec) occurs

gripping the output surfaces and the contact pad and separate seizures appear. At t 0.3–0.7 sec, strain deformation increases, the joint strength increases dramatically due to intensive fusion of foci.

seizure

Therefore, the time over which only the formation of a strong welded joint occurs is about 0.4 s of the total welding time total (, 7 s) in this particular case (Fig. 3), while with other welding methods the whole process takes just 0.32 seconds

As a result of the extended time range of obtaining high-strength joints, the welding process becomes less critical to the heterogeneity of the physical properties of the material of both the hatch itself and the surfaces being joined, increasing its reproducibility. With this method, it becomes possible to trace the entire process of the formation of a joint and select the optimal mode for welding thin leads, including from soft material, by stopping the process at a specified time.

This method of welding enhances the yield of welded parts in the operation of connecting the terminals in the assembly of semiconductor devices and integrated circuits.

Claims (1)

Invention Formula An ultrasonic welding method in which the oscillation amplitude of the tool is changed from O to max and again to O in the welding process, characterized in that, in order to improve the quality of the joint, the amplitude change during welding is performed repeatedly. TP f max  D rltf and min. a §WOX. -, -; rt -i.  I: I I l r-r-- -I M I il I I I I 1 l A  h A i one i 1 i / I; I I -4-H - | -Н Vn-th I П I Tt I S t. 2T 4L Shch1 gt cS p1 / e.1 2 c oS T tfe.2 -one 70n. l f HMceK. n1S 120 17 sixteen 15 14 20