As the demand for lasers capable of processing progressively smaller devices continues to grow, laser manufacturers are switching their focus toward the development of fiber lasers.

Originally, solid state lasers based upon Nd:YAG laser technology were used for medical device manufacturing. These lasers use high-energy flash lamps to pump the active crystal which is in a rod form, while the laser resonator is formed in freespace between two mirrors.

In contrast, the fiber laser’s active medium is a Ytterbium (Yb)- doped gain fiber some tens of meter long, which is pumped by compact and efficient laser diodes with long lifetimes. Wavelength selective components, called Bragg gratings, are fused onto the gain fiber to perform the function of the mirrors. This leads to an all-fiber device needing no alignment and having no internal surfaces open to the air, providing very high reliability.

These lasers are economical and offer high stability and tightly focussed spot sizes for precision applications, ranging from cutting and welding to niche projects such as laser sintering, all of which will be discussed here.

Lasers for welding

Lasers are most commonly used for welding implants and surgical instruments made of expensive materials. These applications must fit precisely into small areas. Because the fiber laser is able to achieve tolerances down to several microns, is well-suited for these costly and precise devices.

One reason why the fiber laser has grown in popularity is its ability to provide strong, smooth, hermetic seals. This is important for several reasons. First, many components are permanently implanted into the body; therefore it is crucial that they do not degrade or corrode over time. Second, surgical instruments that must be sterilized must have hermetic joints that are free from pores, as this enables the equipment to be sterilized in an autoclave without causing damage to the instrument. Finally, the laser’s ability to produce strong, impenetrable welds is vital for manufacturing pacemakers and other devices that contain electronic components.

The laser’s focused energy can prevent damage from occurring to the battery upon manufacture, while the hermetic seal can prolong the lifespan of the device once implanted.

In addition to the strength of the weld, the aesthetic quality of the component is extremely important to medical device manufacturers. While conventional techniques can be difficult to control, resulting in unclean or discolored welds, the low heat input and focused beam benefit the fiber laser.

When using a laser for welding, energy is delivered with exceptional control only to the area where it is required to form the join. This controlled heat input results in clean welds with minimal part distortion or discoloration – a key requirement in the sterile medical industry.

The low heat input can also increase the number of parts that can be welded and have a significant effect upon the areas in which welds can be formed. As energy is delivered only to the specific weld site, lasers can be used to create joins near to polymer seals, glass-to-metal seals, soldered components, and electronic circuits.

Fiber lasers can also have a considerable economic impact upon the production line. Not only do they use less input power than the earlier lamp pumped lasers, but their high-beam quality can create small spot sizes with a diameter of approximately 10μm. This provides a higher peak power density, allowing manufacturers to increase welding speeds up to 10 m/min when processing thinner materials.

Continue on next page