SHINHOP laser

In the production process of high-end electronic products, laser processing plays a significant role in optimizing the product's volume and improving quality, making the products lighter, thinner, and more stable.
Currently, laser precision welding is mainly applied to the housings of electronic products, shielding covers, USB connectors, conductive patches, etc. It has advantages such as low thermal deformation, precise control of the action area and position, high welding quality, the ability to weld dissimilar materials, and ease of automation. However, different welding methods need to be adopted when welding different materials.
Laser welding engineers have summarized from multiple experimental results that in the manufacturing process of consumer electronics, different materials such as high-reflective materials, metal sheets, and dissimilar materials should use specific methods for laser precision spot welding to achieve the best welding results.
1. Laser precision spot welding method for high-reflective materials
When welding high-reflective materials such as aluminum and copper, different welding waveforms greatly affect the welding quality. By using a laser waveform with a front peak, it can break through the high reflectivity barrier. The instantaneous high peak power can quickly change the state of the metal surface, raising its temperature to the melting point, thereby reducing the reflectivity of the metal surface and improving energy utilization. Additionally, since materials like copper and aluminum have fast thermal conductivity, using a gradual decline waveform can optimize the appearance of the weld.
On the other hand, the absorption rate of materials such as gold, silver, copper, and steel decreases as the wavelength increases. For copper, when the laser wavelength is 532nm, the absorption rate is close to 40%. Furthermore, by using infrared lasers and green lasers for pulsed spot welding on copper, it can be observed that the weld size with the infrared laser is inconsistent (Figure 1), while the weld size with the green laser is more uniform, with consistent depth and a smooth surface (Figure 2). Therefore, using a green laser results in more stable welding effects, and the required peak power is more than half lower than that of the infrared laser.

▲ Peak waveform

▲ Welding effect at a wavelength of 1064nm (Figure 1)

▲ Welding effect at a wavelength of 532nm (Figure 2)
2. Laser precision spot welding method for metal sheet materials
Traditional pulsed lasers tend to penetrate and create larger weld spots when welding metal sheet materials; high-reflective materials often exhibit unstable behavior and low absorption rates when solid, leading to issues such as burn-through and poor welding. To address the challenges of welding thin sheets and high-reflective metals, by simulating both analog and digital modulation of the fiber laser's QCW/CW mode, it is possible to trigger one output to achieve multiple pulses, enabling multi-pulse welding at lower power.

▲ Modulation method

▲ High-frequency pulsed spot welding surface formation

▲ Weld seam cross-section
3. Laser precision spot welding method for dissimilar materials
When laser welding thin sheet dissimilar materials, issues such as poor welding, cracks, and low connection strength are common due to significant differences in physical properties, low mutual solubility, and the tendency to form brittle compounds, which greatly reduce the mechanical properties of the weld joint. By selecting a high beam quality nanosecond laser and using high-speed scanning methods, precise control of heat input can suppress the formation of intermetallic compounds, achieving lap welding of dissimilar metal sheets and improving weld formation and mechanical properties.

Domestic advanced lasers such as quasi-continuous fiber lasers and MOPA pulse fiber lasers with adjustable pulse width have become ideal light sources for laser precision spot welding due to their high beam quality, high peak power, and adjustable control.
4. Introduction to the lasers used
A. 150W/1500W quasi-continuous fiber laser
It has diverse compatibility and control modes, can switch between pulsed and continuous modes, and can simultaneously handle processing tasks of two different lasers. The pulse width waveform is flexibly adjustable, air-cooled, and has an electro-optical conversion rate of over 30%, making it another choice for long pulse width and high peak power applications.
B. 120W MOPA pulse fiber laser with adjustable pulse width
The pulse fiber laser with adjustable pulse width adopts a MOPA structure with two-stage amplification, allowing independent adjustment of pulse width and frequency, making more laser applications possible. The pulse width is flexibly adjustable from 60 to 350ns, with a peak power of up to 10kW and a repetition frequency of up to 1000kHz, equipped with an online isolator, making it an ideal laser source for precision laser processing.