By comparison, with laser drilling the smaller the hole diameter, the deeper the hole. This is valuable as today’s high density PCBs need smaller and smaller via holes. Thus, laser drilling has gaining in popularity. And this trend is growing. as even higher density PCBs become necessary to accommodate. even more electronic circuitry over a small area. Laser drilling offers a long pathway of opportunities with many more parameters. which can impact the drilling. Not until hole diameters and PCB layer thicknesses approach the micron level. will today’s laser drilling reach. its physical limits.
pcb sheet material
PCB Material Composition PCB generally consists of four layers. which are heat laminated together into a single layer. The material used in PCB from top to bottom includes. Silkscreen, Soldermask, Copper and Substrate.
The last of those layers, substrate. made of fiberglass and is also known as FR4, with the FR letters standing for "fire retardant." This substrate layer provides a solid foundation for PCBs. though the thickness can vary according to the uses of a given board.
A cheaper range of boards also exist on the market that don't use the same remove PCB materials. but instead consist of phenolics or epoxies. Due to the thermal sensitivity of these boards, they tend to lose their lamination . These cheaper boards are often easy to identify by the smell they give off when soldered.
PCB second layer is copper. which laminated onto the substrate with a mixture of heat and adhesive. The copper layer is thin, and on some boards there are two such layers - one above and one below the substrate. PCBs with only one layer of copper tend to used for cheaper electronics devices.
The massively-used copper clad laminate (CCL) can classified into different categories. according to different classification standards including reinforcing material. used resin adhesive, flammability, CCL performance. The brief classification of CCL shown in the following table.
Above the green soldermask is the silkscreen layer, which adds letters. and numerical indicators that make a PCB readable to tech programmers. This, in turn, makes it easier for electronics assemblers to place each PCB in the proper place. and in the right direction on each component. The silkscreen layer is usually white, though colors. such as red, yellow, gray and black are also sometimes used.