Especially when using hard-brittle materials such as ceramics made of aluminum oxide, silicon nitride or low-temperature co-fired ceramics (LTCC) for the production of circuit carriers in hybrid electronics, the production in a so-called panel arrangement, which means the arrangement of several individual circuits on a raw substrate or wafer for joint production as a batch, has proven itself. With the help of laser scribing, scribe lines are inserted on the substrate. This bullet hole or these bullet holes are visible in the form of closely spaced blind holes or notches. A blind hole is only lasered to a certain depth. This creates predetermined breaking points while avoiding a breakthrough. This weakening of the material serves as a perforation line. After the production run, breaking along these scribe lines enables the mechanical separation of the multiple panel into the individual components.
With the pearl chain-like stringing of blind holes, both the penetration depth and the spacing or overlapping of the individual blind holes can be determined. If there is a large overlap, this is referred to as the production of a notch trench, which in turn has a strong resemblance to the notch trenches introduced during the punching of unfired ceramic substrates (green state). This processing technology enables more efficient production of individual parts by means of a panel arrangement not only for ceramic materials, but also for glasses, silicon and even some metals.
Due to its special properties in terms of thermal conductivity and electrical insulation, ceramics are increasingly being used in electronic circuits. Different types of lasers are used for laser processing, such as laser scribing, notching, cutting, drilling and structuring of ceramics and other materials:
- CO2 lasers or gas lasers operate in the infrared range at wavelengths of approximately 9 µm to 11 µm. High output power and comparatively high efficiency are crucial.
- YAG lasers or solid-state lasers are used for finely structured materials. These are characterized by a smaller focal point and a correspondingly narrower cutting gap.
- Ultra-short pulse lasers (USP lasers) offer the advantage of particularly short laser pulses. The result is extremely precise cutting edges and low material stress.
Wafer dicing, abrasive cutting or sawing continue to be used as classic processing variants for hard-brittle materials, for small components under 5x5 mm2 also in combination with laser processing.
The advantages of laser scribing in detail:
- non-contact process, no micro-cracks in the material
- minimal heat-affected zone and high scribing speed
- high flexibility because of individually determinable scribing depth and distance
- optimum area utilisation and material yield due to smallest possible joint widths
- clean, precise cutting with high quality of the individual elements
A small selection of possible applications for laser scribing:
- for separating wafers in the semiconductor industry
- for separating already printed, sputtered ceramic substrates, for example low-temperature co-fired ceramics (LTCC), into individual elements
- for separating panel arrays on thick-film/thin-film substrates
- for structuring IR filter elements
- friction bars
- ceramic spacers, washers, diffusers and depaneling substrates
- ceramic insulating disks consisting of oxide ceramics such as aluminum oxide (AI2O3), aluminum nitride (AIN), silicon carbide (SiC), silicon nitride (Si3N4)