METHOD FOR MONITORING THE QUALITY OF ULTRASONIC WELDING

Abstract

A method for monitoring the quality of an ultrasonic weld includes monitoring a vibration behavior during a joining process with respect to an actual value of a vibration frequency and/or a vibration amplitude of at least one joining partner of joining partners involved in the joining process. A tool of an ultrasonic welding device is used in the joining process, and at least one measuring device is configured to quantify mechanical vibrations. The detected vibration behavior is analyzed using a Fourier analysis and compared to a predefined set value as reference value.

Claims

1. A method for monitoring quality of an ultrasonic weld, the method comprising: monitoring a vibration behavior during a joining process with respect to an actual value of at least one of: at least one of a vibration frequency and a vibration amplitude of at least one joining partner of joining partners involved in the joining process; and at least one of a vibration frequency and a vibration amplitude of a tool of an ultrasonic welding device used in the joining process, by measuring with at least one measuring device configured to quantify mechanical vibrations, wherein a detected vibration behavior is analyzed using a Fourier analysis and compared to a predefined target value as a reference value.

2. The method according to claim 1, wherein an optical measurement device is used to quantify the mechanical vibrations during the joining process.

3. The method according to claim 1, wherein at least one of an eddy current sensor and a laser vibrometer is used to quantify the mechanical vibrations during the joining process.

4. The method according to claim 1, wherein a plurality of measurement points are monitored by the at least one measuring device with regard to vibration behavior of the measurement points differing from respective target values.

5. The method according to claim 4, wherein one measurement point on at least one of a sonotrode, an anvil, a first joining partner, and a second joining partner is used to quantify the mechanical vibrations.

6. The method according to claim 5, wherein the first joining partner is a first conductor.

7. The method according to claim 5, wherein the second joining partner is a second conductor.

8. The method according to claim 1, wherein to determine the predefined target value as the reference value for a specified pair of joining partners, a pair of uncontaminated joining partners is used, and using the measurement device a quantifying of the mechanical vibrations is captured during the joining process by at least one of the vibration amplitude and the vibration frequency being detected at one or more reference points.

9. The method according to claim 8, wherein the pair of uncontaminated joining partners are a pair of cleaned joining partners.

10. The method according to claim 1, further comprising measuring for a relative deviation of the actual value, from the predefined target value, is used as a measure for a purity of a connection of the joining partners.

11. The method according to claim 10, wherein when the relative deviation of the actual value from a corresponding predefined target value is greater than a predetermined limit value, at least one of the joining process is interrupted and the joining partners are detected as unacceptable parts.

12. The method according to claim 11, wherein the predetermined limit value is less than or equal to 10%.

13. The method according to claim 12, wherein the predetermined limit value less than or equal to 5%.

14. The method according to claim 1, wherein a frequency shift between an excitation frequency of the ultrasonic welding device and a frequency measured at a measurement point during the joining process is detected and is compared to a saved set-frequency shift to determine a degree of purity of the joining partners based on an amount of the frequency shift.

15. A device to implement the method according to claim 1, the device comprising: an ultrasonic welding device; and a measurement device configured to detect the vibration behavior during the joining process, to analyze the detected vibration behavior using the Fourier analysis, and to compare the detected vibration behavior to a predetermined target value as a reference value to monitor the quality of the ultrasonic weld.

16. The device according to claim 15, wherein the measurement device comprises at least one of an eddy current sensor and a laser vibrometer.

Description

DRAWINGS

[0025] In order that the disclosure may be well understood, there will now be described various forms thereof, given by way of example, reference being made to the accompanying drawings, in which:

[0026] FIG. 1 shows a schematic representation of a device according to the teachings of present disclosure; and

[0027] FIG. 2 shows a flow chart for a method according to the teachings of the present disclosure.

[0028] The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way.

DETAILED DESCRIPTION

[0029] The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. It should be understood that throughout the drawings, corresponding reference numerals indicate like or corresponding parts and features.

[0030] FIG. 1 shows a schematic view of a device according to one form of the present disclosure including an ultrasound welding device 30 including a tool including a sonotrode 31 and an anvil 32, between which joining partners 10, 20 are arranged in order to weld them using a vibrational excitation of the sonotrode 31.

[0031] The ultrasound welding device 30 is provided with an optical measurement device 40 which is arranged such that a mechanical vibration behavior can be detected. In the described form, the measurement device 40 is a laser vibrometer. Wires of a cable harness are used as joining partners 10, 20. In a further form, different joining partners are used. In a further form, the measurement device 40 comprises an eddy current sensor which is attached near the sonotrode surface.

[0032] The measurement device 40 serves for detecting and quantifying the mechanical vibrations, in the present case, the occurring vibration frequency at the sonotrode 31 or at one of the joining partners 10, 20 during the joining process.

[0033] FIG. 2 shows a flow chart for a method according to one form of the present disclosure.

[0034] In step 201, the measurement device 40 detects the vibration data, in particular frequency and amplitude, and analyzes the frequency and amplitude using a Fourier analysis. The measurement device then compares the analyzed vibration data in step 203 to a target value and/or to target reference data. If a deviation is found in step 205, then the sample can be deemed as contaminated if the deviation is greater than the permissible limit value.

[0035] If no deviation is found or if a deviation of less than the permissible limit value is found in step 205, then the weld can be deemed as good or acceptable.

[0036] Unless otherwise expressly indicated herein, all numerical values indicating mechanical/thermal properties, compositional percentages, dimensions and/or tolerances, or other characteristics are to be understood as modified by the word “about” or “approximately” in describing the scope of the present disclosure. This modification is desired for various reasons including industrial practice, material, manufacturing, and assembly tolerances, and testing capability.

[0037] As used herein, the phrase at least one of A, B, and C should be construed to mean a logical (A OR B OR C), using a non-exclusive logical OR, and should not be construed to mean “at least one of A, at least one of B, and at least one of C.”

[0038] The apparatuses and methods described in this application may be partially or fully implemented by a special purpose computer created by configuring a general-purpose computer to execute one or more particular functions embodied in computer programs. The functional blocks, flowchart components, and other elements described above serve as software specifications, which can be translated into the computer programs by the routine work of a skilled technician or programmer.

[0039] The description of the disclosure is merely exemplary in nature and, thus, variations that do not depart from the substance of the disclosure are intended to be within the scope of the disclosure. Such variations are not to be regarded as a departure from the spirit and scope of the disclosure.