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.
Characteristics of spatter formation under the effects of different laser parameters during laser drilling
Abstract Laser-drilled holes are known to be inherently associated with the formation of spatter. In this paper, characterisation of the spatter deposited on laser-drilled holes in a Nimonic alloy has been performed and investigated for various laser-processing parameters using a fibre optic delivered Nd:YAG laser. The main findings are: (a) a large proportion of the spatter (approx. >70%) was accumulated due to the initial laser pulses required to drill a through hole; (b) short pulse width, low peak power, high pulse frequency produced smaller spatter areas; (c) at high frequencies, the spatter distribution can be altered due to the interaction between the laser beam and ejected material; (d) focal plane positions between −0.5 and +1.5 mm produced similar spatter areas. In addition, a generic relationship between the spatter area and d entrance / d exit with increasing total laser energy is established.
The Japanese PCB Industry
The Japanese PCB industry is in many ways comparable with the industry in the UK and yet is achieving higher levels of output and taking a somewhat different route in technology. This paper examines the structure of the industry in terms of company size and number, looks at the level and nature of investment and goes on to examine technologies being used and results being achieved.