Abstract:
Circuit boards are manufactured by forming a substrate with a dielectric surface and laminating a metal foil onto the substrate. The metal foil is patterned to form a first wiring layer. A permanent photoimagable dielectric layer is formed over the wiring layer and via holes are formed through the dielectric layer over pads and conductors of the wiring layer. Holes are formed through the substrate and substrate surfaces including the photoimagable dielectric, walls of the via holes, and walls of the through holes subjected to an electroless copper plating process. The process includes seeding the surface, coating the surface with a first solution containing surfactant and electroplating in a second solution in which the level of surfactant is regulated by determining the surface tension and metering surfactant addition to the second solution depending on the determination of surface tension. The copper plating on the photoimagable dielectric is patterned to form an exterior wiring layer which is covered by solder resist with windows over lands around the through holes and surface mount connection pads of the exterior wiring layer to form a high density circuitized substrate. Surface mount components and/or pin in hole components are attached to the circuitized substrate with solder joints between terminals of the components and the lands and/or connection pads to form a high density circuit board assembly. One or more of the circuit board assemblies are mounted in an enclosure with a power supply, CPU, RAM, and I/O means to form an information handling system with increased performance due to shorter signal flight times due to the higher device density.
Abstract:
Method for controlling plating in an electroless plating process. The plating rate is continuously monitored. The plating rate is compared with a set point plating rate. A control voltage is derived proportional to the difference in .plating rate and the desired plating rate, the integral of the difference, and the derivative of the difference. The control voltage is applied to a replenishment control for controlling the replenishment rate of a constituent chemical of the plating process.
Abstract:
The quantity of an anionic material in a sample is determined by adjusting the pH of the sample to place the material in nonionic extractable form, extracting out the material, spectrophotometrically measuring the extracted material, and comparing the measured value to a standard in order to determine the quantity of the anionic material.