PCB Production Part 2

Hello everybody,

in the previous post I gave a brief overview of the design of my own circuit boards. Today I would like to introduce you to various manufacturing options.

Each method has its own advantages and disadvantages:

  • Milling: One of the most practical ways to produce an individual circuit board is milling with a CNC milling machine. If you have such a device available and some experience in mechanical engineering, it is easy to implement correctly created layouts. Many programs support this natively, for example Tartget3000 has its own CAM module, which converts the design of the board directly into G code. A corresponding module is also on board at EAGLE.

    In the past, CNC milling machines were incredibly expensive to buy, but today, in particular, self-made machines have become affordable. However, keep in mind that building your own milling machine without practice in this area is a project for many months. With cheap Machines from China  I've personally had rather bad experiences, one-sided boards can be made with it, but a lot of patience is required here. Double-sided PCBs  are a lot more demanding. Another disadvantage is that the Prick and milling cutters are quite expensive and wear out relatively quickly. Small series can therefore quickly become expensive, especially if you only want to get started with this topic. A small setting incorrectly set and the clamped tool is no longer, at a price of approx. 10 € per piece, errors are quite exclusive.

 

  • Preparatory work for etching: Probably the most common method of manufacturing printed circuit boards is the etching of the boards. There are two different ways to get the finished board. Photo boards are the classic here. With this, clean results can be achieved quite reliably. The necessary work steps are exposure, development and the subsequent etching. This method has proven itself over the years. When using high quality material, exposure and subsequent development is relatively easy.

    There are different methods photosensitive Expose layer. A fairly simple but not ideal method is exposure using black printed paper in combination with sunlight. However, since the sun always shines differently, reproducibility problems can arise. In addition, the edges of the conductor tracks are sometimes a little blurred when used with paper, which works much better with foils.
    A relatively new way of exposure is to use a blue laser diode. There are projects in the network that use a 3D printer in connection with the diode, for example. However, this is not suitable for beginners, since there are many things to consider. For example, many diodes are so powerful that under no circumstances may work without adequate protective equipment! Even the scattered light reflected from a white wall can be enough to irreparably damage the retina! Since the diodes are quite sensitive, the control or supply is sometimes more complex than expected.

    If something goes wrong during development, you can even use Photoresist touch up. Once you have found the necessary settings, the results are easily reproducible for other projects (assuming you use the same material). Another disadvantage is that not only the etching bath, but also the developer must be disposed of as special waste.

    Another option is the toner transfer method. This is usually cheaper and easier to implement because there is no need to expose and develop. Here, a laser printer is used to apply toner to a transfer medium, which then serves as an etching mask. There are special foils on the market that are expensive, however, and nullify the price advantage compared to the photo method. In practice, the Reichelt catalog has proven itself as a transfer medium, this tip is very often mentioned on the Internet. From my own experience, I know that other glossy papers are also suitable, but not all.

    The third, and in my opinion, the best method is manufacturing using a small CO2 laser cutter. Many of our readers now think that this is not possible because a CO2 laser can only cut copper with difficulty - well, they are right. However, I am not talking about cutting printed circuit boards. If you coat a printed circuit board with black lacquer, it can be lasered away with the laser cutter without leaving any residue, the etching mask remains. However, it takes a few tries to find the right paint. In principle, acrylic paints are very suitable, but the result depends on the pigments used in the paint. Since the large-area removal of the lacquer requires a lot of lamp time, it is cheaper to use the same method as for insulation milling.

  • The etching itself: Once you have prepared your circuit board, it is time to etch. In principle, there are special devices that can be bought to achieve comfortably reproducible results, but such devices only pay off from a certain quantity. These can also be built yourself. There are Baths  and Spraying equipment, Baths are easier to implement and also cheaper, depending on the price range, they consist of a heater with circulation pump, control and mechanics. Spray systems usually deliver more even results. There are sets from various manufacturers for home use, e.g. here 
    Concerning. the opinions of the etchant differ, there are

    - Iron III chlorite
    - Hydrogen peroxide  and hydrochloric acid
    - Ammonium persulfate
    - Sodium hydroxide
    - Sodium persulfate
    - Oxalic acid

    Some of the methods listed above are extremely dangerous for untrained users, some are no longer freely available in retail stores and there are reasons for this.
    The best advice is for beginners Starter sets and sodium persulfate. Good results can be achieved at 50 ° C, with a water bath and Glass thermometer you are on the safe side. For the sake of the environment, please remember to dispose of the agent properly. Solved copper is extremely harmful for most aquatic organisms and the acids or bases not only dissolve metals.

Are you particularly interested in a method? Let us know via a comment, we will endeavor to implement this in a further follow-up post.

Until next time :)

Specials

1 comment

Arduinofrosch

Arduinofrosch

Ein kleiner Tipp für Anfänger: Es gibtauch Stifte mit einer leitenden Flüssigkeit. So kann man sich die Leiterplatte zeichnen. Ich nehme das aber nur für einfache Leiterplatten.

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