Laser marking systems

Along with the beam hazard, care should also be taken in performing maintenance on laser marking systems because of the potential for chemical contamination from antimony trioxide (a fire retardant added to the epoxy plastic packages) and beryllium (ceramic packages containing this compound will be labeled). The potential for contamination with visible residues from either of theses two toxic metals is likely. 

Many technical papers have been written about the virtues of laser marking and equipment functionality (Q-switched Nd YAG, Modulated dot matrix CO2, Pulsed TEA CO2, Excimer). Less information has been presented about the engineering of laser optimized polymers. As manufactured, lasers of equivalent wavelength and scan format, may amplify light similarly relative to atomic absorption emission. However, not all lasers yield equivalent results. The successful implementation of laser marking systems requires knowledge of material science and laser function. 

Technical information Laser Marking - Trumpf laser marking systems, (www.trumpf.com). 

This approach is the simplest integration process of vision to laser marking system. It requires minor modifications to the existing hardware and standard camera lenses can be used to focus on a specific area of the mark field. 

Immediately upon excitation of an IPCT band with a fs laser at 400 nm, transient absorption was observed for both salts in solutions with a peak at about 600 nm, characteristic of 4,4/-bipyridinium radical cations. Figure 20 shows the transient absorption spectra of PV2+(I )2 in methanol solution. A marked increase in the absorbance of the 4,4/-bipyridinium radical cations took place within 1 ps after excitation. 4,4/-Bipyridinium radical cations were thus formed in a fs time scale by the photoinduced electron transfer from a donor I- to an acceptor 4,4/-bipyridinium upon IPCT excitation [48], The time profiles of transient absorption at 600 nm are shown in Fig. 21 for (a) PV2+(I )2 in a film cast from DME and (b) PV2+(TFPB )2 in DME solutions. Both of them showed a very rapid rise in about 0.3 ps, which was almost the same as the time resolution of our fs Ti sapphire laser measurement system with a regenerative amplifier. Similar extremely rapid formation of 4,4/-bipyridinium radical cations was observed for PV2+(I )2 salts in methanol and dimethylsulfoxide solutions upon IPCT excitation, respectively. These results demonstrated that the charge separated 4,4/-bipyridinium radical cations were formed directly upon IPCT excitation because of the nature of IPCT absorption bands (that the electrons correlated with the IPCT band are transferred partially at the ground state and completely at the excited state). Such a situation is very different from usual photochromism which is caused by various changes of chemical bonds mainly via the excited singlet state. No transient absorption was observed for PV2+(I )2... 

The laser drilling based marking system is commercially feasible and could be fully automated for a production procedure. It could also be used to tag individual items. If desired, the holes could be fully hidden by a treatment of the surface after drilling. Further work is in progress to evaluate the potential... 

Flammability requirements are stringent for electrical meters and are covered by EN 62053. Capacitor housings require good thermal resistance and dimensional stability. Additionally, both meters and capacitor housings are frequently laser marked, so materials that are compatible with laser marking processes have an advantage. Materials for transformers and insulation systems are tested in accordance with UL 1446 and EN 60085. 

Packaging of the chip portion of the chip/lead combined unit into a plastic or ceramic container is a semi-automated process involving the use of epoxy resins, usually epoxy novolak resin formations [15]. These should be fully cured prior to use, but unreacted monomers may be present, which can sensitise, as may other diluent and flame retardant materials, such as halogenated derivatives of bisphenol A, which are added to the resin prior to use. The completed devices are then laser marked in an enclosed system and tested, again in an automated process, prior to delivery for sale. 

A new pigment system that reacts to the laser beam itself, independent of the polymer matrix, is being developed by Merck, in addition to its present range of conventional laser marking pigments, based on mica coated with metal oxides such as selenium and ferric. 

In medical technology, there is an increasing trend for smart products. These are made possible by modem processes such as laser marking, two-component injection moulding and MID technology. Current examples include functional dmg delivery systems like pens for active ingredient injection and needleless syringes. 

The combination of high optical transparency and IR absorption in polymer composites is relevant for low-emissivity systems and protection against heat radiation but they can also be used for laser marking and engraving. Commercially available products as VP ITO from Evonik contain indium tin oxide nanoparticles with different surface modifications dispersible in different kinds of binder systems and polymers. 

The final step of the total solutions approach is the integration of the laser marking equipment with the materials handling system. Infinite automation, robotics and machine vision possibilities exist, and in any configuration, laser safety must conform to ANSI Z136 standards. 

Morishima et al. [75, 76] have shown a remarkable effect of the polyelectrolyte surface potential on photoinduced ET in the laser photolysis of APh-x (8) and QPh-x (12) with viologens as electron acceptors. Decay profiles for the SPV (14) radical anion (SPV- ) generated by the photoinduced ET following a 347.1-nm laser excitation were monitored at 602 nm (Fig. 13) [75], For APh-9, the SPV- transient absorption persisted for several hundred microseconds after the laser pulse. The second-order rate constant (kb) for the back ET from SPV- to the oxidized Phen residue (Phen+) was estimated to be 8.7 x 107 M 1 s-1 for the APh-9-SPV system. For the monomer model system (AM(15)-SPV), on the other hand, kb was 2.8 x 109 M-1 s-1. This marked retardation of the back ET in the APh-9-SPV system is attributed to the electrostatic repulsion of SPV- by the electric field on the molecular surface of APh-9. The addition of NaCl decreases the electrostatic interaction. In fact, it increased the back ET rate. For example, at NaCl concentrations of 0.025 and 0.2 M, the value of kb increased to 2.5 x 108 and... 

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