My Message
Suggestions
Many people think that silk screen will not affect the circuit performance. But professional hardware engineers must pay attention to these details:
In general, do not use four directions to place the silk screen of resistance, capacitance, tube and other devices, this will lead to bad visual effects when debugging, maintenance and welding.Therefore, the proposed placement is in two directions, as shown above.
As shown in the figure above, it is hard to tell it is R48 or R49.
This proposal is for the top or bottom of the high-speed signal line, because such signal lines can be seen as micro strip lines.
And the speed of the signal on the microstrip line (phase velocity) is related with the media, if the silk screen is pressed on the line, as shown above, the media will become uneven, resulting in phase velocity changes and impedance discontinuity affecting signal quality.Of course, there will be no such problem with the signal lines in the inner layer.
As shown above, this can help reduce the probability of reverse welding mainly when welding.
Other, such as: electrolytic capacitors, etc., you don't need to follow the recommendations, because you can indicate positive and negative polarity.
For BGA, QFN this special package, silk screen size should have the same size with the chip exactly (as shown above), otherwise, it will be difficult to align, thus affecting the welding.
7. The silk screen of installation
Increase the silk screen of screw near the installation hole and indicate the length and the total number of screws to facilitate the installation.
Teo Anca
2017/5/11 16:03:03
nice words and pictures.