There are several kinds of etchants; I am using Ammonium persulfate solution from MG chemicals. It comes as loose powder or crystals. The content releases gasses over time, so you should punch a small hole on the lid of its plastic bottle. These are dangerous and corrosive chemicals, so use a lot of common sense when working with them. There are several variables in the process which you can try to control for the most efficient etching. The goal is to have the shortest etching time and minimal use of etchant chemicals. There is a sweet point in that compromise and you can reach it by experimentation. ...continue reading "PCB Making: 8. Etching"
This step is optional and many people skip it. Copper will oxidize over time, though, and this simple step will protect it. I’ve found several methods to be reasonable but I always use liquid tin to start.
...continue reading "PCB Making: 9. Tinning"
The best bits to drill holes in your FR-4 board are tungsten carbide bits. They are, however, more expensive. You can also use HSS (high speed steel) bits, but they will quickly dull. To drill larger holes start with a small bit and then progressively go larger.
...continue reading "PCB Making: 10. Drilling holes"
It is time to solder through-hole and surface mounted parts.
I use Chip Quick solder paste for SMT components. When not in use, keep it in the freezer to extend its shelf life (it should not dry up). Chip Quick has a very low melting point and it’s perfect to use for SMT since you can apply tiny drops of it through a syringe it comes with. Apply small drops to pads and then position SMT components on it using a tweezers.
...continue reading "PCB Making: 11. Solder parts"
Even tinned, the PCB traces will still corrode. Soldered joints will also oxidize since the solder is exposed to air.
After soldering, the board could be further protected by applying a coat of clear lacquer. The lacquer dries fast and can be soldered through afterwards if needed.
...continue reading "PCB Making: 12. Protection and Sealing"
This particular board did not need an enclosure. Instead, I mounted it on raisers. Holes for raisers were already drilled.
If you do have an enclosure, you may want to try to fit it: drill the holes and/or cut openings using a tool like a nibbler.
...continue reading "PCB Making: 13. Enclosure"
This is a general guidance for the initial testing.
Thoroughly examine the board for physical defects: are all traces complete or there are breaks?
Are all pins soldered and is the quality of the solder joints acceptable? Soldering point may be missing (forgot to solder it), may have a bridge or a short, or it may be a poor joint (cold point). Just redo it.
Is any component missing? (Something blunt but may happen!)
You may need a magnifying glass or a loupe with a strong light.
...continue reading "PCB Making: 14. Testing and Troubleshooting"
Quality of the tools that we use to write software for projects like this is very important when selecting which MCU we may want to use. Atmel has a very robust IDE based on the Microsoft’s Visual Studio (which is arguably the best development environment out there). Coupled with a JTAG interface, writing and debugging firmware with Atmel toolset becomes a pleasure.
...continue reading "PCB Making: 15. Software"
There are few things that I did not get to try this time around:
- Adding a bitmap (for example, a logo) to the board’s layout. I believe you create it as a custom part and use it from your library? Or you somehow download an image.
- Similarly, it would be useful to make bitmaps for parts like diodes to help orient them as a guide when soldering.
- How do you remove Eagle layers like Cream, Glue, etc. which are populated? There are also many other tricks to learn with Eagle.
I really wanted to find out exactly how much etchant would I need for a given board. That would be at least a theoretical minimum to etch all exposed copper, so after some calculation I made this table. In practice, you would probably want to double that amount to get it to etch faster, but that's a good starting value to measure.