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We report on a comprehensive study of laser percussion microvia drilling of Ajinomoto build-up film (ABF) material using an ultrashort pulsed laser in MHz burst mode. After laser processing, microvia drilling quality is being evaluated by the fabricated diameter and taper using laser scanning microscopy and metallography. The influences of the incubation effect, heat accumulation and shielding effects as a result of pulse to pulse interactions are being discussed on the ablation threshold, penetration depth and laser microvia drilling quality. We find that an increasing heat accumulation in MHz burst mode processing is responsible for the void formation and delamination of the insulating ABF layer. Therefore, the parameter clearance is introduced to evaluate these effects on the microvia sidewalls. For a comparable clearance, applying 2 intra-burst pulses achieves an average reduced taper of down to 19.5% compared to single pulse mode. At the same time, a reduced laser drilling time of 16.7% per microvia highlights the enormous potential of the MHz burst mode for laser drilling of ABF material in printed circuit board fabrication.
In this contribution we report on the possibilities of dry and lubricated friction modification
introduced by different laser surface texturing methods. We compare the potential of Laser-Induced
Periodic Surface Structures and Laser Beam Interference Ablation on 100Cr6 steel in a linear
reciprocating ball-on-disc configuration using 100Cr6 steel and tungsten carbide balls with load
forces between 50mN and 1000 mN. For dry friction, we find a possibility to reduce the coefficient
of friction and we observe a pronounced direction dependency for surfaces fabricated by Laser
Beam Interference Ablation. Furthermore, Laser-Induced Periodic Surface Structures result in
a load-dependent friction reduction for lubricated linear reciprocating movements. This work helps
to identify the modification behaviour of laser generated micro structures with feature sizes of
approximately 1μm and reveals new possibilities for surface engineering
In this contribution, we report on surface functionalization by introducing laser induced periodic surface structures on 100Cr6 bearing steel to modify complex tribological properties. The advanced approach of this study is the measurement of the coefficient of friction by performing a ball-on-disk Stribeck test on laser structured surfaces with polytetrafluoroethylene balls in a lubricant environment. The Stribeck test reveals the modified friction behavior using translation speeds up to 106 mm/min and load forces between 100 mN and 5000 mN. Our results show increased stiction and coefficient of friction for laser structured surfaces in the regime of boundary lubrication which is attributed to the laser induced surface asperities. Decreased coefficient of friction is observed in the regime of mixed and hydrodynamic lubrication, i.e. for velocities higher than 1000 mm/min, for surfaces covered by laser induced periodic surface structures with low spatial frequency.