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PCB design tips 100, teach you to master PCB design easily (96-100)

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96. After floating copper automatically, the floating copper fills the blank space according to the position of the device on the board and the layout of the traces.

However, many sharp corners and burrs of less than or equal to 90 degrees are formed (for example, each pin of a multi-pin chip). There will be a lot of relative sharp angle floating copper), will discharge in the high voltage test, can not pass the high pressure test, I do not know in addition to automatically remove the copper manually removed after a little bit of these sharp corners and burrs there is no other good Method.

The sharp floating copper problem that occurs in the automatic floating copper is indeed a very troublesome problem. In addition to the discharge problem that you mentioned, the problem of processing is also caused by the accumulation of acid droplets in the processing. Since 2000, mentor supports dynamic copper foil edge repair in both WG and EN. It also supports dynamic copper clad and can automatically solve the problem you mentioned. See the animation demo. (If there is a problem with opening directly, click the right mouse button to select "Open in new window", or select "Save target as" to download the file to the local hard disk and open it.)


97. Does the distribution and wiring of the power supply in the PCB wiring also need to be as careful as grounding. If you do not pay attention to what kind of problems will be brought? Will it increase interference?

If the power supply is handled as a planar layer, the method should be similar to the processing of the ground layer. Of course, in order to reduce the common-mode radiation of the power supply, it is recommended that the power supply layer shrunk by 20 times from the ground. If wiring, it is recommended to walk the tree structure and pay attention to avoid power loop problems. Closed-loop power supplies can cause large common-mode radiation.

 

98. The address line should use star wiring? If star wiring is used, can the termination resistor of Vtt be placed at the connection point of the star or at the end of one branch of the star?

Whether or not the address line is to be star-type cabling depends on whether the delay requirements between the terminals meet the establishment and maintenance time of the system, and also the difficulty of the wiring. The reason of the star topology is to ensure that the delay and reflection of each branch are consistent. Therefore, terminal parallel matching is used in the star connection. Generally, matching is added at all terminals, and matching is performed only in one branch, and it is impossible to satisfy such requirements.


99. If you want to minimize the board area, and you plan to stick it up like a memory stick, can you?

Positive and negative paste PCB design, as long as your welding process is no problem, of course.


100. If there are only four DDR memory products on the motherboard, the clock can reach 150Mhz. What are the specific requirements for wiring?

The 150Mhz clock routing requires that the length of the transmission line should be minimized and the effect of the transmission line on the signal should be reduced. If you can not meet the requirements, simulation, look at the matching, topology, impedance control and other strategies are effective.


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