Ultrasonic Metal Welding

Ultrasonic Metal Welding

Date:Jan 25, 2021

Ultrasonic metal welding


Ultrasonic metal welding is a special method that uses the mechanical vibration energy of ultrasonic frequency to connect the same or dissimilar metals. When metal is ultrasonically welded, neither electric current nor high temperature heat source is applied to the workpiece, but under static pressure, the mechanical energy is transformed into internal energy, deformation energy and limited temperature rise. Solid phase welding occurs when the two base materials reach the recrystallization temperature. Therefore, it effectively overcomes the spatter and oxidation caused by resistance welding. Ultrasonic metal welding machine can perform single-point welding, multi-point welding and short strip welding on thin wire or sheet materials of non-ferrous metals such as copper, silver, aluminum, and nickel. It can be widely used in the welding of SCR leads, fuse pieces, electrical leads, lithium battery pole pieces, and tabs


Ultrasonic metal welding uses high-frequency vibration waves to be transmitted to the metal surface to be welded. Under pressure, the two metal surfaces are rubbed against each other to form a fusion between molecular layers.


The advantages are fast speed, energy saving, high fusion strength, good electrical conductivity, no sparks, and close to cold processing; the disadvantages are that the welded metal parts cannot be too thick (generally less than or equal to 5mm), the welding point cannot be too large, and pressure is required.


 


Advantages of ultrasonic metal welding

 


1. The welding material does not melt, and the metal is not fragile.


 


2. After welding, the conductivity is good, and the resistivity is extremely low or nearly zero.


 


3. Low requirements on the surface of the welded metal, both oxidation and electroplating can be welded.


 


4. The soldering time is short, without any flux, gas, or solder.


 


5. Welding without sparks, environmental protection and safety.


 


Ultrasonic metal welding range

 


1. Ni-MH battery Ni-MH battery nickel mesh and nickel sheet mutual fusion and nickel sheet mutual fusion. .


 


2. Lithium battery and polymer battery copper foil and nickel sheet are mutually fused, and aluminum foil and aluminum sheet are mutually fused. .


 


3. The wires are fused to each other, and the wires are fused into one and multiple wires.


 


4. The wires are fused with famous electronic components, contacts and connectors.


 


5. Mutual fusion of large heat sinks, heat exchange fins and honeycomb cores of famous household appliances and automotive products.


 


6. High current contacts such as electromagnetic switches and non-fuse switches, and mutual fusion of dissimilar metal sheets.


 


7. The sealing and cutting of the metal pipe can be water and air tight.


 


Influencing factors of ultrasonic metal welding

 


Ultrasonic metal welding amplitude

Amplitude is a key parameter for the material to be welded, which is equivalent to the temperature of ferrochrome.


If the temperature is not reached, the welding will not be possible, and if the temperature is too high, the raw material will be scorched or the structure will be damaged and the strength will be deteriorated. The selected ultrasonic transducer is different, the output amplitude of the transducer is different, after adapting the ultrasonic transducer of different transformation ratio


The amplitude and welding head can correct the working amplitude of the welding head to meet the requirements. The output amplitude of the transducer is usually 10-20μm, and the working amplitude is generally about 30μm. The transformation ratio of the horn and the welding head is related to the shape of the horn and the welding head, the front-to-rear area ratio and other factors.


In terms of shapes, such as exponential amplitude, functional amplitude, stepped amplitude, etc., it has a great influence on the transformation ratio, and the front and rear area ratio is proportional to the total transformation ratio. Choose welding machines of different brands. The easiest way is to make them in proportion to the size of the working welding head to ensure the stability of the amplitude parameters.


Ultrasonic metal welding frequency

Any ultrasonic welding machine has a center frequency, such as 20KHz, 40 KHz, etc. The working frequency of the welding machine is mainly composed of the mechanical resonance of the ultrasonic transducer (Transducer), ultrasonic horn (Booster), and welding head (Horn) Determined by frequency.


The frequency of the ultrasonic generator is adjusted according to the mechanical resonance frequency to achieve consistency, so that the welding head works in a resonant state, and each part is designed as a half-wavelength resonant body. Both the ultrasonic generator and the mechanical resonance frequency have a resonance working range.


 


It is generally set to ±0.5 KHz, and the welding machine can basically work normally within this range. When we make each welding head, we will adjust the resonant frequency, and the error between the resonant frequency and the design frequency is required to be less than 0.1 KHZ. For the 20KHz welding head, the frequency of our welding head will be controlled at 19.90-20.10 KHZ, with a small error of 5‰.


Ultrasonic metal welding node

The nodes, welding heads, and ultrasonic horns are all designed as a half-wavelength resonator of the working frequency. In the working state, the amplitude of the two end faces is the largest and the stress is the smallest, while the node in the middle position has zero amplitude and the largest stress. .


The node position is generally designed as a fixed position, but the thickness of the usual fixed position design is greater than 3mm, or the groove is fixed, so the fixed position is not necessarily zero amplitude, which will cause some calls and some energy loss. Calls are usually isolated from other parts by rubber rings, or shielded by sound insulation materials. Energy loss is considered when designing the amplitude parameters.


Ultrasonic metal welding mesh

Ultrasonic metal welding is usually designed on the surface of the welding position and the surface of the base. The purpose of the mesh design is to prevent the sliding of the metal parts and to transmit energy to the welding position as much as possible. The reticulation design generally has square, diamond, and strip reticulation. Metal-clad welding heads and bases such as gold hand ornaments require no lines to be designed. The size and depth of the lines are determined according to the specific welding material requirements.


Ultrasonic metal welding transducer

There is no big difference between the transducer used for metal welding device and the transducer used for plastic welding device. The special feature is that the welding metal has higher quality requirements, because it often requires a large instant power when welding metal. The transducer is required to have high power capacity and low impedance, without the use of transducers used in plastic welding devices.


Ultrasonic metal welding power supply

There is no big difference between the ultrasonic power supply used in metal welding equipment and the ultrasonic power supply used in plastic welding equipment. [span] The particularity is that welding metal has higher requirements. In order to meet the needs of metal welding, it is necessary to use an intelligent ultrasonic power source-ultrasonic generator.


The ultrasonic generator has an automatic frequency tracking system. Changes in the working conditions of mechanical devices or electronic components during the welding process will cause a change in the vibration frequency. [span] The ultrasonic generator will track the frequency of the vibration system to make the generator and the vibration system The frequency automatic tracking system can compensate for the changes in the working state during the welding process, so that the system is in resonance again and maintains the stability of the welding parameters. The focus is on the stability of the amplitude, which is very important for metal welding. .


 


Ultrasonic metal welding accuracy

 


Because the ultrasonic welding head works under high-frequency vibration, it should try to maintain a symmetrical design to avoid unbalanced stress and lateral vibration caused by the asymmetry of sound wave transmission (the welding head we use for welding uses the longitudinal ultrasonic vibration Transmission, for the entire resonant system), unbalanced vibration can cause the welding hair to heat and break. Ultrasonic welding is used in different industries for different processing accuracy requirements. For particularly thin workpieces such as the welding of lithium ion battery pole pieces and tabs, and the coating of gold foil, the requirements for processing accuracy are very high. All our processing equipment All use numerical control equipment (such as machining centers, etc.) to ensure that the accuracy of the machining meets the requirements.


 


Ultrasonic metal welding life

The service life of a welding head is critically determined by two aspects: first, material, and second, process


Material aspect: Ultrasonic welding requires metal materials to have good flexibility (small mechanical loss during sound wave transmission) and good characteristics, so the most commonly used materials are aluminum alloy and titanium alloy, but ultrasonic metal welding requires the welding head to be wear-resistant (requires more High hardness) makes the choice of materials more difficult, because hardness and toughness seem to be inherently opposed, which requires us to choose very demanding materials. The high-quality steel materials we choose can better solve this contradiction. The effective life of the welding head is maximized.


Process: Including the processing technology and subsequent processing technology. The processing technology has been described in detail above. The subsequent processing includes heat treatment and parameter trimming. Based on the material selected by our company, we have an original heat treatment process to guarantee; in each welding After the head is made, the parameters must be measured and adjusted separately to ensure the product.



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