High-precision PCB circuit board refers to the use of fine line width/spacing, tiny holes, narrow ring width (or no ring width), and buried and blind holes to achieve high density. And high precision means that the result of "thin, small, narrow, thin" will inevitably bring high precision requirements. Take the line width as an example: 0.20mm line width, according to the regulations, 0.16 ~ 0.24mm is qualified, and the error is ( 0.20±0.04) mm; and the line width of 0.10mm, the error is (0.10±0.02) mm, obviously the latter’s accuracy is doubled, and so on is not difficult to understand, so the high-precision requirements will not be discussed separately . But it is a prominent problem in production technology.

　　(1) In the future, the high and fine line width/spacing of fine wire technology will be from 0.20mm-0.13mm-0.08mm-0.005mm to meet the requirements of SMT and Multichip Package (MCP). Therefore, the following techniques are required.

　　①Using thin or ultra-thin copper foil (<18um) substrate and fine surface treatment technology.

　　②PCB circuit board adopts thinner dry film and wet film process. Thin and good quality dry film can reduce line width distortion and defects. Wet lamination can fill small air gaps, increase interfacial adhesion, and improve wire integrity and accuracy.

　　③ using electrodeposited photoresist film (Electro-deposited Photoresist, ED). Its thickness can be controlled in the range of 5-30/um, which can produce more perfect fine wires, especially suitable for narrow ring width, no ring width and full-board electroplating. At present, there are more than ten ED production lines in the world.

　　④Using parallel light exposure technology. Since parallel light exposure can overcome the influence of line width variation caused by the "point" light source's oblique light in all directions, fine wires with precise line width dimensions and clean edges can be obtained. However, parallel exposure equipment is expensive, requires high investment, and requires work in a high-cleanliness environment.

　　⑤ Using automatic optical inspection technology (AutomaticOpticInspection, AOI). This technology has become an essential means of detection in the production of fine wires, and is being rapidly promoted, applied and developed. For example, AT&T Company has 11 AoIs, and}tadco Company has 21 AoIs specially used to detect the inner layer graphics.

　　(2) The functional holes of the printed board for surface mounting of micro-hole technology mainly play the role of electrical interconnection, which makes the application of micro-hole technology more important. Using conventional drill bit materials and CNC drilling machines to produce tiny holes has many failures and high costs. Therefore, the densification of printed boards is mostly due to the densification of wires and pads. Although great achievements have been made, its potential is limited. To further improve the densification (such as wires less than 0.08mm), the cost has risen sharply. , thus turning to the use of micropores to improve densification.

Read recommendations:

High frequency PCB

Six-layer Immersion Gold Board (BGA)

DIP plugin

Mobile phone board

The distinction and pros and cons of circuit boards.AOI circuit board