The need to make iron periodically occurs in many techies. Sometimes the task allows nafigachit all the wires on the breadboard, and sometimes, unfortunately, you need something more serious. One day, the need to make printed circuit boards overtook me ... Laser-iron technology for making handicrafts at first strongly repels its randomness (what to print, how to warm, how much to press, how to tear, etc.), but friends shared their experience and it turned out that it is really not that difficult. LUT is unquestionably cheaper than any other option, and (suddenly) is quite suitable for dual layer boards.
Anyone interested is more complicated, more expensive and more accurate, you can make a photoresist , but our technique (the main element of which is a special paper) allows us to stably work tires of 0.3 / 0.3 mm, so that in our community there is an opinion that tyan photoresists are not needed.
Whoever does not see the point in the handicraft production of boards, most likely will be able to recall a couple of cases when they had to cut the tracks and solder the wiring for the whole batch of boards. And by making one board at home, you can properly debug it and gain confidence in the factory boards.
Under the cut, I will share the deterministic method of manufacturing two-layer printed circuit boards using LUT technology with different backup circuits in case of jambs. From idea to inclusion. We will work with KiCad, Inkscape, sandpaper, iron, ammonium persulphate and engraver.
Any device starts with a circuit. Most board errors can be fixed at the design stage. And to ensure that the scheme is consistent with the board, you need a good EDA-software. For example, KiCad.
If you are still working with proprietary limited solutions, start with the article Tracing PCBs in KiCAD or skip this section.
We use the recently released KiCad 5, because I deeply like this program, its community (including CERN) and the idea of multiplatform FOSS as a whole.
So, the algorithm with life hacks :
When the board is ready, you need to overtake it in SVG for further refinement. It is better to unload the board from EDA without mirroring, so as not to get confused and mirror it properly.
And it is necessary to mirror only the front layer of F.Cu. Since we look at the back layer of B.Cu in the editor from the front, it is already mirrored. For reliability, it is better to place at least some text on both layers and make sure that this text is not read))
( thank you , dShaded ) From KiCad it is better to upload via File | Plot , since there it is possible to make all the holes 0.35 mm at once. For LUT, fat holes are not needed, it is better to have more copper and it will be cleaned with a drill.
Actually:
Now you need to send SVG to the printer on plain paper. And do the following with this paper:
- It is easy to guess that the holes are necessary for precise orientation of the front layer relative to the back. If you want it easier, there is a way without holes: very precisely fold a piece of paper with a template and place the textolite inside. As already mentioned, a slight deviation will not be fatal (unless, of course, the holes have not been drilled yet)
- Another modification of the folding shared TonnyRed :
Freshly printed sheets with the upper and lower layers put on each other, shining through the lamp and combining. We fasten in several places along the edges. In the resulting envelope put textolite.
- Another (much more advanced) way of orienting layers is shared by dgrees . Thank!
Tax, this is a section about SVG, and we have already moved to the machines ... That's all, the final touch on SVG and more will not be needed:
Fill everything around with black so that the PCB parts that do not belong to the board are not etched and do not saturate the ammonium persulfate with copper. Yes, ferric chloride is also possible, but ammonium is blue.
The whole article is, in fact, written only in order to share with the world the most correct paper for LUT. Here she is:
Also, we have information on the benefits of Black Diamond paper. Other brands may have the necessary properties, but may not. HP does not fit exactly (melts under the iron), Lomond conditionally fits, "but somehow medium . " You can experiment with different glossy inkjet photo paper . Write in komenty cho as with other papers)
oco advises using a roasting sleeve. It is a transparent film, does not melt under the iron and is easily removed from the board, leaving the toner. The printer is refilled with a sheet of plain paper.
Algorithm:
In case of errors, you can erase one of the layers with acetone, put the already torn piece of paper of the opposite layer (so that the toner does not detach from the board and does not transfer to the board on which you iron) and repeat.
For pickling, we will need a plastic container (or any non-metal container in which the board will fit while lying). And also, a disposable spoon or varibis for stirring the board (against bubbles that interfere with etching).
Ammonium persulphate is recommended to be diluted in warm water 1: 2. But this is a fairly high concentration, 1: 3 or even 1: 4 is enough. In the end, you can still mix up the sweat. Recommended temperature reassurance - 40-50 degrees.
However, please note that overheating all kinds of chemicals is quite dangerous. High concentration, high temperature and copper salts can lead to a creep effect:
https://vk.com/video-24764675_456239191
Use a respirator.
It is advisable to move the board, blow bubbles from it and maintain the temperature in the region of 35-45 degrees in a water bath. But if the persulfate is not dead, it can itself be maintained (see video above).
If poorly poisoned, you can:
Thank you, Helium4 for advice in a personal on this section.
After etching, the toner is wiped off with acetone.
It remains to drill and connect vias.
Layfkhak: If it so happened that there is a displacement of layers, it can be compensated for by the angle of inclination of the drill .
From the first hole it is difficult to catch the desired angle, so it is better to first drill the least demanding holes to the exit point (for example, those that go to the metallization area or bulk copper islands)
After drilling, it is necessary to connect the holes. Of course, we will do this with the help of resistor / capacitor legs and a soldering iron. But sometimes it is necessary to put an SMD component on top of the transition hole, and in this case, a high solder bun is unacceptable. We came up with the following trick:
You can also order and use rivets , thanks to tretyakovmax for reminding them (True, his way of ripping up a patchcord lived - this seems to be a topic for a separate article)
If you still made a mistake and etched a layer with components that have more than two mirrored conclusions, try to bend the legs of the components in the opposite direction and solder them upside down.
Like all))
You can solder components and cut in power.
After testing and correcting, fix vias, transfer text and logos to the silk-screen layer and order purple boards on OSHPark , or many boards on EasyEDA .
The board at KDPV is indeed manufactured by LUT, and not ordered from OSHPark. Purple solder mask solves :)
Here is another suitable vidos for the further study of all kinds of subtleties (carefully, sticky channel, there are victims):
Thanks for attention!
Source: https://habr.com/ru/post/417501/