Recent developments in miniaturization have been the main reason for the strong growth of the electronics industry. As miniaturization continues to drive the industry, making electronics and PCB is becoming more challenging. The most challenging aspect of PCB manufacturing is the combination of high-density through-holes and through-holes used for interconnection. Through holes are used to install the electronic components that make up the circuit.

As the packing density of through holes in PCB assembly line increases, the demand for smaller holes also increases. Mechanical drilling and laser drilling are the two main techniques used to produce precise and repeatable micron holes. Using these PCB drilling techniques, through-holes can range in diameter from 50 to 300 microns with depths of approximately 1-3 mm.

Precautions for PCB drilling

The drill press consists of a high-speed spindle that rotates at approximately 300K RPM. These speeds are critical to achieving the precision required to drill micron scale holes on PCBS.

To maintain accuracy at high speeds, the spindle uses air bearings and a direct bit assembly held in place by precision collet chucks. In addition, the vibration of the bit tip was controlled within 10 microns. In order to maintain the exact position of the hole on the PCB, the drill bit is mounted on a servo workbench that controls the movement of the workbench along the X and Y axes. Channel actuators are used to control the movement of the PCB along the Z axis.

As the spacing of the holes in the PCB assembly line decreases and the need for higher throughput increases, the electronics controlling the servo may fall behind at some point in time. Using laser drilling to create the through-holes used to make PCBS helps reduce or eliminate this lag, which is a next-generation requirement.

Laser drilling

The laser bit used in PCB manufacturing consists of a complex set of optical elements that control the accuracy of the lasers needed to punch the holes.

The size (diameter) of the holes to be drilled on the PCB is controlled by the aperture of the installation, while the depth of the holes is controlled by the exposure time. Moreover, the beam is divided into multiple bands to provide further control and precision. The mobile focusing lens is used to concentrate the energy of the laser beam at the exact location of the borehole. Galveno sensors are used to move and position PCBS with high accuracy. Galveno sensors capable of switching at 2400 KHz are currently used in industry.

In addition, a novel method called direct exposure can also be used to drill holes in circuit boards. The technology is based on the concept of image processing, where the system improves accuracy and speed by creating a PCB image and converting that image into a location map. The position map is then used to align the PCB below the laser during drilling.

Advanced research in image processing algorithms and precision optics will further improve the productivity and yield of PCB manufacturing and high-speed drilling used in the process.