Laser micromachining is a process used to make tiny features in parts - measured in micrometers or millimeters. Pulsed lasers effectively complete this work by depositing very small, finite amounts of energy into a material, resulting in extremely precise and reproducible material removal. Suitable deposition of energy enables the laser to ablate, cut, drill, machine or scribe a material. A number of pulsed lasers are available for micromachining; in these examples, we used a 20W single mode pulsed fiber laser marker.
Laser micro drilling creates holes that are important features for many applications – via holes for wafers, medical cannulae, or microchannels for fluids. Our first example, is an application to drill a hole into stainless steel. This particular hole is to be used in a precision flow application, so it’s really important to have a smooth wall without burring at the edges. The thickness of the material is 0.01” (~250 µm), and the desired size of the finished hole is 0.008” (~200 µm) with hole diameter tolerances of ± 0.0005”.
The tolerance for the hole diameter was so tight on this application, that a four step process was used (see table). The long pulse duration creates a large melt pool which is then ejected. Because a lot of heat is deposited into the part, a large heat affected zone is created, resulting in a melted region. The short pulse duration that follows creates a smaller melt pool which results in a very fine expulsion of the material, thereby cleaning the outside edge of the hole.
Machining/Laser Micro Milling
Our next application looks at a generic machining process which involves the removal of material to a specified depth, creating a variety of relief features such as grooves, slots and profiles, without actually cutting through the material. This technique is used frequently in the medical and electronics industries. The application below, looks at a cross machined into a thin sheet of stainless steel. The thickness of this sheet is 0.001” (~25 µm). The application required a machining depth of 0.0005” (~12.5 µm ) without breaking through the back side. Process parameters are detailed in the table, and results are shown in the picture.
Short pulse duration was critical in this application to achieve a shallow depth of marking. As noted in the previous example, the short pulse duration creates a shallow melt pool which is then extracted, removing very fine layers of material.
Both of the above are excellent examples of precision results that can be achieved using a single mode fiber laser marker for laser micro milling.