Quality and reliability of high aspect-ratio blind microvias formed by laser-assisted seeding mechanism in PCB
The laser-assisted seeding (LAS) mechanism should be able to plate microvias with a high aspect ratio that may not be feasible by conventional electroless plating due to the small via geometry. In particular, the plating of microvias with a high aspect ratio close to one is difficult due to the limited accessibility of chemical solution to the via internal wall surface in conventional plating technology. LAS is a promising alternative. The objectives of this paper are to report the deposition mechanism of a thin copper film layer (laser-assisted seeding) on printed circuit board (PCB) microvias dielectric and to study the quality and reliability of the microvias produced by this mechanism. Results find that the microvias produced by LAS have acceptable quality and are as reliable as that formed by conventional electroless plating technology. The hole wall of the microvia was covered with deposited copper, and the thickness of which was found related to some LAS parameters. A set of experimental best LAS processing conditions is also given.
Laser (UV) microvia application in cellular technology
In the past three years, microvia drilling using laser technology has become the dominant method of producing blind vias smaller than 150μm. The ablation characteristics of the materials used in the manufacture of PWBs can be divided into three categories: organics, glass, and metals. Organics are composed of resins and epoxies commercially available from a variety of vendors. Two types of resins that are typically used for microvia formation in the telecommunication applications are resin coated copper foil® (RCC or RCF) for subtractive PCB process, and thermal‐curing resin (TCR) for additive PCB process respectively. This paper details the basics of UV YAG laser capabilities, alignment techniques, plating tests, reliability tests, manufacturable microvia design rules, and production experiences.
Laser beam drilling applications in novel materials for the aircraft industry
The efficiency of gas turbines can be improved by raising the temperature of combustion. This necessitates stronger cooling which is achieved by blowing additional air through numerous very small holes, having typical diameters between 0.3 and 2.5 mm. To enable higher temperatures the NiCo-alloys are additionally coated with zirconia oxide.A 350 W cw-pumped Nd:YAG-laser with a beam parameter product of 10 mm*mrad which was acousto-optically Q-switched is used for trepan drilling. With argon as an assisted gas with a pressure of abt. 10 bar, clean cuts were obtained. Any diameter between 0.3 and several mm can be chosen. Perpendicular as well as 17°, 33°, 45° and 57° inclined trepan drillings were made. A 0.6 mm hole into a 2 mm alloy was made in 1 s. This is four to ten times faster as with a free-running pulsed laser. Thus, process time and heat load of the work piece are substantially reduced: The recast layer is narrower. The smooth process in the absence of oxygen yields crack-free and purely metallic surfaces. With zirconia coated sheets, no case of chipping was observed.Another drilling application for the aircraft industry is the perforation of the wings with millions of small holes. Numerical simulations have shown that these holes with diameters between 40 and 70 μm drilled into the so called laminar wing can improve the aerodynamic conditions. This could effectivly reduce the fuel consumption. 400 holes per cm2drilled in an acceptable time through 0.8 mm thick titanium are required.A two rod Nd:YAG-laser including birefringence compensation, delivers an output power up to 200 W with a beam parameter product less than 3 mm*mrad. Using argon as assisted gas 185 holes per second with 80 μm diameter were drilled in a 1 mm thick titanium alloy. The single shot technique enables the treatment at a moving workpiece.The efficiency of gas turbines can be improved by raising the temperature of combustion. This necessitates stronger cooling which is achieved by blowing additional air through numerous very small holes, having typical diameters between 0.3 and 2.5 mm. To enable higher temperatures the NiCo-alloys are additionally coated with zirconia oxide.A 350 W cw-pumped Nd:YAG-laser with a beam parameter product of 10 mm*mrad which was acousto-optically Q-switched is used for trepan drilling. With argon as an assisted gas with a pressure of abt. 10 bar, clean cuts were obtained. Any diameter between 0.3 and several mm can be chosen. Perpendicular as well as 17°, 33°, 45° and 57° inclined trepan drillings were made. A 0.6 mm hole into a 2 mm alloy was made in 1 s. This is four to ten times faster as with a free-running pulsed laser. Thus, process time and heat load of the work piece are substantially reduced: The recast layer is narrower. The smooth process in the absence of oxygen yields crack-free and purely metallic...