What Are The Requirements For High-precision PCB Circuit Boards?
High-precision PCB is not a simple matter. While it puts forward higher standards for the company's equipment and operator experience, it is also an unavoidable important problem in production technology. Today we will talk about what conditions do we need to have for the high-precision PCB circuit board?
The high-precision circuit board refers to the use of fine line width/spacing, micro holes, narrow ring width (or no ring width), and buried and blind holes to achieve high density. High precision means that the result of "fine, small, narrow, and thin" will inevitably lead to high precision requirements. Take the line width as an example: 0.20mm line width, 0.16～0.24mm is qualified as required, and the error is (0.20 ± 0.04) mm; and the line width of 0.10 mm, the error is (0.1 ± 0.02) mm, obviously the accuracy of the latter is doubled, and so on is not difficult to understand, so high precision is required No longer discuss separately. But it is an outstanding problem in production technology.
In the future, the high-density line width/pitch will be from 0.20mm-0.13mm-0.08mm-0.005mm to meet the requirements of SMT and multi-chip package (Mulitichip Package, MCP). Therefore, the following technology is required.
①Substrate
Using thin or ultra-thin copper foil (<18um) substrate and fine surface treatment technology.
②Process
Using thinner dry film and wet pasting process, thin and good quality dry film can reduce line width distortion and defects. Wet film can fill small air gaps, increase interface adhesion, and improve wire integrity and accuracy.
③Electrodeposited photoresist film
Electro-deposited Photoresist (Electro-deposited Photoresist, ED) is used. Its thickness can be controlled in the range of 5-30/um, and it can produce more perfect fine wires. It is especially suitable for narrow ring width, no ring width, and full-board electroplating. There are currently more than a dozen ED production lines in the world.
④ Parallel light exposure technology
Using parallel light exposure technology. Since the parallel light exposure can overcome the influence of the line width variation caused by the oblique rays of the "point" light source, it is possible to obtain fine wires with precise line width dimensions and smooth edges. However, the parallel exposure equipment is expensive, the investment is high, and it is required to work in a high cleanliness environment.
⑤Automatic optical inspection technology
Using automatic optical inspection technology. This technology has become an indispensable means of detection in the production of fine wires, and is rapidly being promoted, applied and developed.
