Nanosecond Laser Micro Welding: The Possibilities!

The nanosecond fiber laser is the most recent addition to AMADA MIYACHI AMERICA’s broad portfolio of laser micro welding solutions. Its output parameters are a bit different than other laser welding sources like pulsed Nd:YAG , quasi-continuous-wave (QCW) fiber and the CW fiber laser. As the name suggests, the nanosecond fiber laser’s pulse widths are in the nanosecond range – under 250 nanoseconds (ns) – with pulse energies around 1 millijoule (mJ).

Typically, the nanosecond fiber laser uses many pulses to make a weld, and, with pulse frequency typically set between 200-500 kilohertz (kHz), can do this very rapidly. The ability to use such low pulse energy while precisely controlling the number of pulses provides excellent resolution of the energy input, and ultimately weld stability.

For comparison, a low energy pulsed Nd:YAG or QCW fiber laser weld may be 0.5 joules (J) in a single pulse. This is equivalent to 500 pulses for the nanosecond fiber laser, which enables very fine metering of energy for micro laser welds. Figure 1 shows the pulse differences among various welding lasers: continuous wave (CW) fiber, pulsed Nd:YAG and QCW fiber, and nanosecond fiber.

Figure 1 – Peak power and pulse width

Furthermore, with a maximum peak power of around 10-15kW, the nanosecond laser has no difficulty coupling into reflective materials like copper and aluminum. A great example of this is welding copper tabs to cylindrical battery cells. The nanosecond welder can weld 0.007-inch thick copper to the cold rolled steel cans, as shown in Figure 2.

Figure 2 – Nanosecond fiber laser applications

Another great feature of certain nanosecond fiber lasers is the ability to independently adjust peak power and pulse width, which isn’t possible with Q-switched lasers. This adds an extra dimension of flexibility in dialing the exact weld needed, and makes the laser good for both reflective materials that need high peak power and metals like steel, which need less peak power.

To have sufficient power density to weld, the nanosecond fiber laser uses a focus spot size of around 30 microns (0.001-inch). That means an XY motion is needed to create sufficient joint volume. This allows flexible programmable of the weld size and shape.

A somewhat surprising result of using such short pulse durations is the ability to create joints in dissimilar metals that would otherwise be considered impossible due to the creation of brittle intermetallics. Figure 3 shows two cross sections of such examples of metal combinations. On the left, we show copper and aluminum and on the right, aluminum to steel which has traditionally not been possible.

Figure 3 – Cross section of dissimilar metal welding

Here’s even more good news for the nanosecond fiber welder – it can be used for laser marking and thin metal laser cutting. That makes it a versatile, inexpensive, in-stock, off-the-shelf piece of equipment that can be multi-purposed for many processes.

These units offer motion through scan heads, which can be easily programmed using a simple graphical user interface (GUI). The user interface functions like a simple drawing package, so you can easily create and position square, circle, line and spiral weld paths in the process area without the need to program G (preparatory) and M (action/ auxiliary) CNC codes. You can also import .dxf and other graphics files if necessary, so it’s super easy.

A good example of this is welding a wire to a ring. Here, the ideal weld shape is rectangular, with the width just larger than the wire diameter, but not so large that it overheats the ring. It should be long enough for the required weld strength. Typically, the working area of the welder is 2×2 to 4×4 inches, and welding can occur anywhere in that area. This also offers the potential to nest parts and process in one go without need for additional motion.  The galvo scanning solutions offers extremely quick part to part positioning, significantly faster than linear translation stages.

In this blog, I have provided basic information on the unique qualities and benefits of using a nanosecond fiber laser for spot and seam welding metals. This is a rapidly expanding technology and new possibilities are found each day. Please contact us if you would you like to know more about this technology and how it might apply to your process.