The high density of multi-layer circuit boards means that the use of high-precision wire technology, micro-aperture technology and narrow ring width or no ring width and other technologies, is the PCB assembly density greatly improved.
In the multilayer circuit board outer layer etching, Multilayer PCB if the copper foil ridge deep into the board resin is very deep, after etching the dense circuit area may also leave residual copper, these phenomena may not be easy to detect after etching, but in the After the nickel-soaking process, it is possible to find lines or metal areas where the lines or edges of the pads are deformed. This problem is sometimes thought to be the problem of residual or poor washing, but in fact is the problem of improper wiring or copper selection.
The development of multi-layer circuit board manufacturing technology is very fast, especially in the late 1980s, with the emergence of high-density I / O (input / output) lead VLSI, ULSI integrated circuits, Multilayer PCB SMD devices and the development of SMT, To promote multi-layer circuit board manufacturing technology to achieve a high level of technology. But also with the "light, thin, short, small" components are widely used in a large number of SMD's rapid development and SMT universal, interconnection technology is more complex, Multilayer PCB to promote multi-layer circuit board manufacturing technology to fine line width and Narrow spacing, thin high-level, small aperture of the direction of development. Multi-layer printed circuit board technology, that is, multi-layer printed circuit board manufacturing technology has been widely used in civilian appliances.
With the narrowing of the multi-layer circuit board, Multilayer PCB the drilling technology and equipment to put forward higher technical requirements, while the need for full chemical plating, Multilayer PCB direct plating technology to solve the hole plating adhesion and ductility and other issues.
2.4 Reduce the width of the hole
The narrowing of the circumference of the surrounding space increases the wiring space, thereby further improving the circuit pattern density of the multilayer circuit board.
2.5 thin multi-layer technology
Thin multi-layer technology fully adapt to the components of "light, thin, short, small" and high-density technical requirements. The current multi-layer circuit board manufacturing process technology trends are divided into: high-level thin plate and the general thin plate. Multilayer PCB High-layer multi-layer circuit board thickness will be 0.6-5.0MM, layer from 12-50 layer or higher; thin multilayer circuit board thickness will be 0.3-1.2MM, layer from 4-10 layer or higher.
2.6 multi-layer circuit board structure diversification
With the high stability of high-precision devices, high reliability requirements, multi-layer circuit board manufacturing density requirements and the number of interconnection and the increase in complexity, the diversity of its structure is inevitable.
2.7 Buried, blind and through-hole combination of multi-layer circuit board manufacturing technology
This type of multilayer printed circuit board is complex and will be built using a large number of electrical interconnection technology, which can increase the wiring density of 50%, Multilayer PCB greatly reducing the fine wire, small aperture of the ring width of the production pressure.
2.8 multi-layer wiring of multi-layer circuit boards
Multi-layer wiring structure is coated with copper foil on the surface of the substrate, and then use the computer-aided data provided by the control wiring machine, 0.06-0.1MM square enameled wire according to X, Y direction, vertical and horizontal wiring, and then 45 ° oblique wiring, Multilayer PCB were laid on both sides of the substrate, the wiring is completed with a thin film covered, play a fixed and protective effect, in the curing, CNC drilling and other processes.