Metal fusion bonding – Means to apply vibratory solid-state bonding energy to work
Patent
1990-02-13
1992-09-15
Seidel, Richard K.
Metal fusion bonding
Means to apply vibratory solid-state bonding energy to work
228110, B23K 106
Patent
active
051470829
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a tool configuration for ultrasonic welding consisting of a sonotrode as an active tool and an anvil as a work fixture for the workpieces. Such a tool configuration is meant to be used in ultrasonic plastic welding as well as in metal welding and particularly also in the bonding of thin wires.
The vibrational amplitude resulting from the roughness of the working surface of the sonotrode is passed on to the workpiece situated above. This is especially true in the ultrasonic welding of metals. A reproducible vibrational initiation is a basic requirement for a uniform welding quality. Just as important is the fixing in position of the part assigned to the anvil. In this case as well, the part to be joined is often retained by the surface roughness of the anvil. To obtain this roughness, the latter is provided with cross grooves or so-called waffle patterns or the like using sandblasting or eroding methods. With such constructional measures, one can ensure that the reproducible relative movement necessary for ultrasonic welding arises as a friction movement in the surface to be joined.
The rough working surfaces of the machining insert wear away very quickly on the sonotrode and on the anvil, particularly when hard metals are ultrasonically welded. If very large peak-to-valley heights are selected to attain a longer tool life, then heavy impressions will develop on the parts to be joined, for example, when the so-called waffle pattern is used. Besides the unsightly visual effect such impressions cause, they can also adversely affect the quality of the workpieces leading to damages such as low shearing resistance or peel strength, or they can also cause the parts to split.
On the other hand, when the roughness is too shallow, as is especially the case in the welding of parts made of aluminum or its alloys, material remains stuck to the sonotrode and the anvil. As a result, the bond can be partially or completely torn apart again when the welding press is opened after the ultrasonic welding operation.
In the case of ultrasonic welding installations in the prior art, the working or bearing surfaces of the tools must therefore be machined at regular intervals or else be provided from the start with replaceable pins.
Therefore, the object of the invention is to produce a tool configuration for ultrasonic welding, in which the working surfaces have improved resistance to wear.
The objective is solved according to the invention in that at least the sonotrode is provided with synthetic hard material on its working surfaces, through which the ultrasound is injected into the workpieces to be welded together. Preferably, the anvil is also provided with such a synthetic hard material on its working surfaces.
Polycrystalline diamond, in particular, polycrystalline boron nitride, or also cubic-crystalline boron nitride, come under consideration as synthetic hard materials within the scope of the invention. These types of synthetic hard materials are already known in the coating of machining tools. Compared to the usual hard metals, they are distinguished by their improved hardness properties. However, this is inevitably linked to greater brittleness and susceptibility to breaking, so that as such one cannot expect them to be used for ultrasonic tools.
It was able to be shown within the scope of the invention, however, that the polycrystalline diamond, for example, in spite of its brittleness, withstands the ultrasonic vibrations, and thus is suited for application in ultrasonic tool configurations.
Further details and advantages of the invention are revealed in light of the drawings in the following description of the figures of exemplified embodiments, in connection with the further sub-claims.
The figures depict in rough schematic representation respectively:
FIG. 1 a tool configuration for ultrasonic metal welding;
FIG. 2 a tool configuration for ultrasonic plastic welding or riveting;
FIG. 3 a sonotrode head with bonding cotter to bond thin wires and
FIG. 4 a variant of the bonding cotter accord
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IEEE Transactions on Components, Hybrids, and Manufacturing Technology, vol. Chmt--2, No. 3, pp. 283-288, Sep. 1979.
Western Electric, "Multi directional Ultrasonic Wire Bonding Tip", Avedissian, Technical Digest No. 20, pp. 7,8, Oct. 1970.
Krause Ralf D.
Moll Helmut
Miner James
Seidel Richard K.
Siemens Aktiengesellschaft
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