Copper PCB design as an important part, whether it is the domestic front green PCB design software, but also some foreign Protel, PowerPCB provides intelligent features copper, then how can we apply good copper, I will own some ideas with you to share, we hope colleagues benefit.
The so-called copper is the unused space on the PCB as a reference plane, and then filled with solid copper, the copper area is also known as copper pour. The significance of copper, reduce ground impedance, improve anti-jamming capability; to reduce pressure drop, increase power supply efficiency; connected with the ground, can also reduce the loop area. Also allow for possible PCB welding deformation of purpose, most PCB manufacturers will be required to PCB designers copper ground wire or mesh-like filling in an open area of the PCB, copper if handled improperly, it will Buy Debu loss, whether copper is “ good than harm ” or “ more harm than good ”?
We all know that at high frequencies, the distributed capacitance of the wiring of the printed circuit board will work, when the length is greater than the noise frequency corresponding to the wavelength of 1/20, it will have an antenna effect, the noise will be emitted outside through the wiring, If there are poorly grounded in the PCB copper, then copper has become the tool of noise propagation, therefore, in high-frequency circuits, do not think, to pick up a local ground, this is “ Ground &rdquo ;, must be less than λ spacing /20, played in the wiring hole and multilayer ground plane “ good ground &rdquo ;. If done properly the copper, copper not only increase the current, but also played the dual role of shielding interference.
Copper generally have two basic ways is a large area of copper and copper mesh, also often asked to, large copper mesh copper good or good, not good to generalize. Why? Large copper, has the dual role of increasing current and shield, but a large area of copper, if the wave soldering, the board would likely tilt, and even blistering. So large copper, generally will open several slots, ease copper blister, pure copper mesh shielding effect is mainly to increase the role of the current is reduced from the cooling point of view, the grid is good (which reduces the heating surface of copper) also played a certain role in electromagnetic shielding. But the need to point out that the grid is staggered so that the alignment direction of the composition, we know the circuit, the width of the traces of the operating frequency of the circuit board has its corresponding “ electrical length “ (actual size divided by the number that corresponds to the frequency of the operating frequency can be obtained, in particular books visible), when the operating frequency is not very high, when perhaps the role of the grid lines is not very obvious, once the electrical length and operating frequency to match, it is very bad You'll find a circuit simply will not work everywhere in the transmit signal jamming systems work. So for using the grid colleagues, my suggestion is based on the design work of the selection board, do not stick to one thing and hold. Therefore, the high frequency circuit for immunity requirements of multi-grid, low frequency circuit has a circuit large current and other commonly used copper to complete.
Having said that, then we in copper, in order to allow the copper to achieve our desired results, then copper areas requiring attention to those issues:
1. If the PCB ground more, there SGND, AGND, GND, etc., it is necessary according to different PCB board position, respectively, the most important of “ to ” as a baseline reference to independent copper, digital and Analog to separate the copper from small words, but before the copper, the first bold respective power connection: 5.0V, 3.3V, etc. As a result, the formation of a plurality of polygon structures of different shapes.
2. differently single point connection, the European approach is connected via a 0 resistance or beads or inductors;
Copper, crystal oscillator 3. The oscillator circuit is a high-frequency transmitter near the source, practice is surrounded by crystal copper, then the crystal case separately grounded.
The islands (dead zone) problem, if you feel great, then the definition of a ground vias added to it can not take much to do.
5. At the beginning of the wiring, respond equally ground, when traces of it should take a good ground, can not rely on the addition of vias to eliminate later on copper is connected to the pin, the effect is very bad.
6. On the board is best not to have the appearance of the horns ("= 180 degrees), because from the point of view of electromagnetism, which is composed of a transmitting antenna! For the other there will always be only one impact is large or small only, I recommend the use of arc along the edge.
7. A multilayer wiring open area in the middle layer, not copper. Because it is hard to do to make this copper “ good ground ”
8. The metal inside the device, such as a metal heat sink, metal reinforcing strips, etc., must realize “ good ground &rdquo ;.
9. The three-terminal regulator heat slug must be well grounded. Crystal nearby ground buffer zone must be well grounded. In short: copper PCB, grounding problem if handled well, certainly “ &rdquo ;, more good than harm it can reduce the reflux area signal line, reducing the signal external electromagnetic interference.