SI engineers who don’t know how to process can’t be called Mr. Gao

SI engineers who don’t know how to process can’t be called Mr. Gao

     Simulation is the simulation of PCB design, and PCB design is the design for processing and production.

      As processing brings more and more error factors to the design, should the simulation be a simulation of PCB design or should it consider the simulation after production and processing?Of course, we all know that as the speed becomes higher and higher, processing factors will have greater and greater influence on the performance of high-speed signals, such as the stub of the via, the hole diameter, the layer deviation, and the etching.The articles have been introduced and shared with cases.

    Now that we have talked a lot about high-speed processing factors, let's talk about a simpler one today, that is, the simulation design of power supply voltage drop, which is what everyone often calls DC simulation.

    Now that we have talked a lot about high-speed processing factors, let's talk about a simpler one today, that is, the simulation design of power supply voltage drop, which is what everyone often calls DC simulation.

     As for its simulation principle, it may be the simplest,

simulation theory. The picture below can make it clear.

     Therefore, as long as we get the voltage value and maximum current value of the power supply network, we can simulate the voltage drop of the PCB power supply link.Just like the following example, the power link from the VRM to the sink has a voltage of 0.85V and a current of 5A. After knowing these parameters, we can easily do it .

   The following is the simulation result of the power supply link. It seems that both the voltage at the load end and the current density of the entire link can meet the requirements, that is to say, the PCB power supply design after simulation is ok!

    This is of course a very objective result, which objectively and accurately reflects the requirements of the PCB design of this power link.Basically, the simulation ends here.

    Suddenly one day, Mr. Hi-speed thought about whether the PCB link of the power supply might and might be affected by some processing factors like high-speed signals?Then Mr. Hi-speed consulted some IPC standards to see if there are any machining tolerances that would affect the design of the power supply. Finally, in a certain chapter, he found the standard for copper thickness processing, which is the picture below.basically, the simulation ends here.

    As can be seen from the figure, the copper thickness of 0.5oz is generally made at 0.6mil, but the most extreme limit is 0.449mil.

     Since it is listed in the IPC standard, it means that even if the 0.5oz copper is really made as thick as 0.449mil after processing, it will meet the requirements!

     Mr. Hi-Speed suddenly thought, if the copper thickness of the case mentioned above is really only 0.449mil after processing, will the pressure drop be enough?

    While everyone was still worried, Mr. Gao had directly changed the copper thickness from 0.6mil to 0.449mil on the original case for simulation verification!It turns out that such a change has a lot of deterioration in terms of voltage drop and current density!

    From the simulation result of 0.449mil, the voltage drop has increased by about 7mV, the current density has deteriorated by 33A/mm², and the degree of deterioration cannot be ignored.

    Of course, after realizing the "seriousness" of the problem, Mr. Gao also communicated with our DFM engineers and colleagues in the board factory, wanting to know whether the probability of achieving such a limit copper thickness is high or not. Fortunately, they said that basically

There has never been such a situation, and it is mainly about 0.6m.The following are some of the slice diagrams of the PCB copper thickness they provided, which is also consistent with their statement

     Although this is just a whim of Mr. Gao's ideas and simulation verification, it has not actually made such a thick copper board.but from a general perspective, it is very helpful to know more about processing, especially the impact of processing on design and simulation, whether it is for hardware engineers, PCB engineers or SI engineers！

nt with their statement.

. The following are some of the slice diagrams of the PCB copper thickness they provided, which is also consistent with their statement.