The practical problems of thin line production of circuit board

- Mar 30, 2017-

With the development of electronic industry, the integration degree of electronic components is more and more high, but the volume is smaller and smaller, and the BGA type is widely used. Therefore, the PCB line will become smaller and smaller, more and more layers. Reduce the line width and line spacing is to make use of the limited area, increase the number of layers is the use of space. The main line circuit board in the future when 23mil, or less.

It is generally believed that the production of circuit boards every increase or rise of a grade, you must invest once, and the larger the investment funds. In other words, the high-grade circuit board is made of high-grade equipment. However, large-scale investment is not affordable for every enterprise, but also to invest in the trial after the collection of process data, trial production costs a lot of time and money. It seems to be a better way to decide whether or not to invest in accordance with the actual situation and the market situation, first of all, according to the current situation of the enterprise. This paper describes the equipment under normal production lines, can limit the width of the condition and method and fine line production.

The general production process can be divided into cover hole etching method and pattern plating method. The line obtained by acid etching method is very uniform, which is favorable for the control of the impedance, and the pollution of the environment is little, but a hole is broken, and the production control of alkali corrosion is easy.

First of all, the first is the dry film production line, different dry film of different resolution but can generally be shown after exposure line distance of 2mil/2mil, the resolution of the common exposure machine can reach 2mil, the general line in this range the distance will not cause problems.

The influence of developing conditions on the resolution is more obvious when the line is smaller. When the line above the 4.0mil/4.0mil developing conditions (speed, liquid concentration, pressure etc.) the influence is not obvious; line is 2.0mil/2.0/mil, the shape of the nozzle, the pressure for developing a normal line can play a key role, then the developing speed may decrease, while the concentration of liquid line appearance effect, its possible why is the fan nozzle pressure, the line spacing is small, momentum can still reach the dry film at the bottom, so it can be developed; the conical nozzle pressure is small, so have difficulty developing fine lines. The direction of the other plate has a significant influence on the resolution and the side wall of the dry film.

For alkaline etching, there is always a mushroom effect after plating, usually only obvious and not obvious distinction. If the line is larger than 4.0mil/4.0mil, mushroom effect is small.

In acid and alkali corrosion is the same line width and line shape of different speed different, but generally with the dry film etching process, easy in transmission and in front of the mask and the surface pore membrane break or scratch, so be careful with production, acid alkali corrosion is better effect than the line. There is no mushroom effect side etching alkali corrosion is less, the other with a fan-shaped nozzle is better than the conical nozzle. The corrosion resistance of the wire is smaller.

So that ordinary equipment does not make special adjustments, can realize the production of 3.0mil/3.0mil (refers to the film width and spacing) board; but the qualified rate is influenced by the environment and personnel operation proficiency and operation level, suitable for the production of alkali corrosion under 3.0mil/3.0mil base copper circuit board, except the small to a certain extent, fan-shaped nozzle the effect is obviously better than the conical nozzle.

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