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How To Deal With High Speed PCB Microhole
Jun 13, 2018

Circuits of different properties must be separated on a circuit board, but connected at the best possible time without electromagnetic interference. Microvia is needed by the circuit board manufacturer. Usually, the diameter of microholes is 0.05mm to 0.20mm. These holes are generally divided into three types, namely blind via, bury via and through via. Blind hole located at the top of the printed circuit board and the underlying surface, has the certain depth, used for surface line and below the inner line connection, the depth of the hole is usually no more than a certain ratio (aperture). Embedded hole refers to the connection hole in the inner layer of the printed circuit board, which will not extend to the surface of the printed circuit board. Both of the above types of holes are located in the inner layer of the circuit board. Before lamination, the through-hole forming process is used to complete the process. The third, called a through-hole, passes through the entire circuit board and can be used to interconnect internally or as a adhesive orifice for components.

In the design of RF circuit boards, should as far as possible the high RF power amplifier (HPA) and low noise amplifier (LNA) apart, in simple terms, is to make high power RF transmitting circuit from low noise receiving circuit. This can be easily done if there is a lot of space on the PCB board. But usually when you have a lot of zero components, the PCB space becomes very small, so it's hard to get there. You can put them on both sides of the PCB, or let them work alternately, rather than simultaneously. High power circuits can sometimes include RF buffers and VCO.Wells has the most advanced equipment NXTIII .

Zero component layout is the key to achieving an excellent RF design. The most effective technology is to fix the zero component on the RF path and adjust its orientation to minimize the length of the RF path. And keep RF input away from RF output, and away from high power circuit and low noise circuit as far as possible.

Design partitioning can be divided into physical partitioning and Electrical partitioning. Physical partition mainly involves zero component layout, orientation and shielding, etc. Electrical partitions can continue to be divided into power distribution, RF routing, sensitive circuits and signals, grounding, etc

The most efficient PCB stack method is to place the main ground on the second layer below the surface layer and to move the RF line as far as possible on the surface layer. The RF path to minimize the size of hole can not only reduce the path inductance, but also can reduce the main grounding on the solder joint, and can reduce the RF energy in other area of the leak to the laminated board.

In physical space, linear like multistage amplifier circuit is usually enough to multiple RF area between separate from each other, but the duplexer, mixer, and the intermediate frequency amplifier always have multiple RF/IF signal interference, so we must carefully to minimize the impact. RF and IF wires should be crossed as far as possible and as far as possible separated by a ground area between them. The correct RF path is important for the performance of the entire PCB board, which is why the zero-component layout usually takes up most of the time in PCB design for mobile phones.

On the mobile phone PCB, usually low noise amplifier circuit can be placed on one side of the PCB, and high power amplifier on the other side, and finally by duplexer on the same side they will be connected to one end of the RF antenna and the other end of the base band processor. This requires some skill to ensure that the RF energy does not pass through the hole from one side of the board to the other. The common technique is to use a blind hole on both sides. By arranging the blind hole in the area free from RF interference on both sides of PCB board, the adverse effect of hole crossing can be minimized.

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