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What's the skill to distinguish the good from the bad of PCB?

2019-07-18 16:34:04

How to distinguish the good from the bad of PCB, manufacturers all know that making PCB board is to turn the planned schematic into a real PCB board. Please don't underestimate this process. There are many things that work in principle that are difficult to accomplish in engineering, or others can't accomplish, so do a piece of P. CB board is not difficult, but to do a good PCB board is not an easy job.

  Two major difficulties in the field of microelectronics are the processing of high-frequency signals and weak and small signals. In this regard, the level of PCB manufacturing is particularly important. The same principle planning, the same components and different people produce PCB with different results. So how can we make a good PCB board? Based on our past experience, we want to make a good PCB board. The following are my views:

  Clear planning objectives

  Then encounter a planning mission, first of all, we need to clarify its planning objectives. Ordinary PCB board, high frequency PCB board and small signal processing PCB board are still PCB board with high frequency and small signal processing. If it is ordinary PCB board, as long as the layout and wiring are reasonable and neat, the mechanical scale is correct, if there are medium load line and long line, it is necessary. In order to reduce the load, the long-term driving should be strengthened, and the key point is to avoid long-term reflection. When there are signal lines over 40MHz on board, special consideration should be given to these signal lines, such as crosstalk between square lines. If the frequency is higher, the length of the wiring will be more stringent constraints. According to the network theory of dispersion parameters, the interaction between high-speed circuit and its wiring is the decisive factor, which can not be neglected in system planning. With the progress of gate transmission speed, the opposition on the signal line will be added correspondingly, the crosstalk between adjacent signal lines will be added proportionally, and the power and heat dissipation of general high-speed circuit are also very large, which should be paid enough attention to when making high-speed PCB.


  How to distinguish the good from the bad of PCB?

  When there are weak signals of millivolt level or even microvolt level on board, special care is needed for these signal lines. Small signals are too weak to be disturbed by other strong signals. Shielding measures are often necessary, otherwise the signal-to-noise ratio will be greatly reduced. So that the useful signal is submerged by noise and can not be extracted effectively.

  The adjustment of the board should also be considered in the planning stage. The physical orientation of the test points and the isolation of the test points should not be neglected, because some small and high frequency signals can not be directly added to the probe for measurement.

  In addition, some other related factors should be considered, such as the number of layers of the board, the packaging shape of the components, the mechanical strength of the board, etc. Before making PCB boards, we should have a clear idea of the planning objectives of the plan.

The article originated from Jiangmen single-sided and double-sided circuit boards.