Analysis of PCB Vacuum Etching Technology (2)

The vacuum here refers to the negative pressure in the operating area of ​​the system and the low suction just enough to prevent the puddled effect of the etching solution. Even the thinnest inner-layer board cannot be sucked up by the suction unit, and the production accuracy needs to be guaranteed. By connecting the track of the suction machine with the upper fixed reel in the conveying system, the designer ensures that the distance between the suction process and the board surface is the best value, regardless of whether the production is thin or thick. This means that regardless of the type of PCB, a uniform extraction rate of the etching solution can be obtained. On the surface of the entire 24″X24″ large board, the side of the circuit board facing upwards, only 1 micron copper thickness fluctuation was found. By comparison, the etching effect of the upward-facing part and the downward-facing part of the board is basically the same.

The circuit quality of the boards produced using vacuum etching technology is also very good. Detailed tests with different PCB manufacturers have shown that the new vacuum etching technique produces straighter conductor profiles, so that the resulting boards more precisely approximate routing requirements.

In the vacuum etching process, the shrinkage rate of the attack amount of the etching medium on the side of the wire under the resist film and the etching factor used to describe the etching depth of the wire and the amount of lateral etching are very high.​​
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Of course, there are also a series of other factors that are largely unaffected by the manufacturer that can affect the actual etching effect. For example, the thickness of the resist, the quality of the exposure and development processes, and the copper thickness of the etched substrate all have a great impact. In general, it is estimated that the etching process or the update frequency of the etching solution only accounts for half of the impact on the etching effect. But PILL project manager Oliver Briel stressed that “it turns out we have that 50% completely under control”.

Vacuum etching technology also shows a series of advantages in other areas:

The capacity of the etching process can be fully utilized. The throughput of the etching process increases as the production time is shortened due to the increased etching speed.
Since the first etching can achieve satisfactory results, there is no need to re-etch for re-etching.
It can reduce the related factory control engineering and reduce the corresponding cost.
The vacuum etching system uses relatively simple technology to produce ultra-fine wires, eliminating the need for swinging jet manifolds.
The nozzle structure with intermittently adjustable injection pressure can be eliminated. The design was primarily designed to ensure a reduction in the puddle effect, which is now accomplished simply with a suction system.
Vacuum etching technology allows for shorter and tighter process modules, where both getter and etch functions can be performed simultaneously in the same module.

An additional advantage of the vacuum etching technology system is that the spray manifold can be positioned laterally in the direction of travel. Conventional jet manifolds for the production of fine wire sheets usually have jets arranged longitudinally in the direction of travel so that different jet pressures can exist at the edge and in the sheet. The proper angle of the nozzles to the direction of travel facilitates maintenance and requires less time to replace, and this arrangement also allows for simple electrical flow monitoring of each injection manifold individually. If an irregularity occurs, the user can immediately identify which injection manifold is at fault and can then make adjustments directly without delay.

The future potential of vacuum etching technology is very great, because this process is especially suitable for the production of thin wires and ultra-fine wire structural boards. Preliminary testing of conductive patterns below 50 microns yields promising results. Further evaluation of the ability to produce thick copper board circuits using vacuum etch technology is underway, and all data so far indicate good results. It is particularly worth noting that not only the traditional copper chloride is used as the etching medium, but also the ferric chloride (III), which is commonly used at present, especially in Asia, is used as the etching medium. Although it takes longer to use this etch medium, it works better with steeper conductor profiles and undoubtedly provides an alternative to processes that are now accepted as standard, especially for a special production of fine lines.

If required, the vacuum etching line can be equipped with an environmentally friendly regeneration system: according to the technology developed by HUMLEITEC, hydrogen peroxide is no longer used, and oxygen in the air is used, that is, no additional pure oxygen is needed to re-oxidize the copper chloride solution. In practical application for a long time, the system using this technology has proved to be successful, and the investment cost can be recovered quickly.