LIDE - Laser Induced Deep Etching
LIDE - Laser Induced Deep Etching
A highly productive laser system and an innovative process technology are revolutionizing the machining of thin glass substrates. With the Laser Induced Deep Etching (LIDE) process, micro-structuring of glass is now easier and more economical than before.
In microsystems technology, thin glass with a thickness of 50 µm to 500 µm is very suitable as a substrate material for a variety of applications. However, because it is prone to microcracking and stress formation when machined using conventional methods, its industrial-scale use has failed time and time again. The new LIDE process by LPKF Laser & Electronics AG uses the laser as a noncontact precision tool for micromachining glass with unrivaled productivity and quality. The processing is easy and amazingly fast.
LIDE makes new product designs in microsystems technology possible and has the potential to transform entire process chains in production.
Conventional processing methods for cutting and drilling thin glass often cause microcracks or stresses, which compromise quality and can lead to component failure. Quality deficiencies make the use of glass in industrial microsystems technology uneconomical.
Especially in thin glass substrates with thicknesses of 50 μm – 500 μm, structures cannot be generated with the high aspect ratios required for applications in microtechnology. The embedded structures are not small and precise enough for many applications.
The production speed for fragile glass substrates is too low for conventional materials to be used economically.
The Laser Induced Deep Etching (LIDE) process by LPKF is a two-step process. In the first step, the glass is locally laser-modified according to the desired layout. This is done by laser radiation from a specially developed source. The radiation is focused within the workpiece and guided through its entire thickness. The optical and chemical properties of the material are modified to enable selective chemical etching in a second process step. The modified areas of the glass are removed much more rapidly than the unmodified material is. In order to yield structures with specific widths, the glass is soaked in the etching bath for a predefined time.
The package comprising the innovative LIDE process and a new high-end laser system paves the way for numerous new applications in
To prepare holes and cuts in glass substrates, LPKF uses a laser system specially developed for LIDE. The machine is equipped with a high-speed axis. In the drilling operation mode, the system prepares Through Glass Vias (TGV). The mentioned axis is used to scan the glass substrate in a meandering way. The laser pulses of the specifically developed laser source are emitted according to the desired TGV pattern design while the axis is traveling at full speed. This means that the laser pulses are emitted on the fly. Thus, a laser processing speed of > 5000 TGV modifications per second can be reached in this mode - with glass thicknesses of up to 500 μm.
After laser modification, the glass is modified in a multitude of spots placed with a position tolerance of ± 5 μm (Cpk > 1.33) across an area of 510 mm x 510 mm. These modified areas can be transformed into blind or through holes in the subsequent wet etching step. Without further measures being taken, the modified regions are removed by the etching solution on both sides of the glass substrate to yield hourglass-shaped holes.
V-shaped vias are obtained through masking of one side of the glass during the etching step. Typical taper angles range from 3° to 8°, depending on the nature of the glass and the chemical composition of the bath.
Micro Cutting Mode
In the micro-cutting mode the laser beam is moved along an arbitrary two-dimensional tool path. The laser pulses are emitted at equal distances along the path, resulting in a curtain of modified regions extending from one side of the glass substrate to the other. As in the TGV operation mode, the final features are then generated through removal of the modified areas of the glass by etching. The minimal feature size is in the range of 10 μm. The modification speed in this mode is up to 100 mm/s and is independent of the glass thickness up to a thickness of 500 μm.