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Schematic drawing without consideration of pcb

joe_ls , 04-21-2018, 06:26 AM
Hi Gents,

just a question, but I don't want to create a tempest in a teapot. And I don't want a pro/con discussion about pcb-software, it's just about the work-style. :-)

I just had a talk with another EE guy and he is an absolute fan of KiCAD. The pecularity about this software ist the possibility to create a schematic drawing without any second thought about footprints, case and any other specific considerations. Transistors are just, NPN or PNP, case is not important, cooling is not important, THT or SMT is not important - he just concentrates about the schematic drawing. Anything else is job of the PCB Artist. Also no definition of mounting holes or fiducials in the schematic.

Mind-boggling! My argumentatin was: ok, in principle I can do this in OrCAD as well (no footprint and padstack defined for a part), during the first stage of a schematic drawing but before I create the netlist I have to define these information and I have to complete these part definitions. I also define heatsinks if needed.

I can understand his argumentation but I just think this is more a hobbyiest or amateur approach to start a design. I don't know any company this would work. Even with a freelance project, with more freedom in your work-style, I have more specifications from begin. Some parts are predetermined, because of money, availability or whatever.

This work-style of my colleague is for me like the next step of doing the layout in some software like SprintLayout: Just drawing the pcb, without schematic at all. Generic footprints without partnames.

Does he have a point? Should it be more this abstract work-style? Is it just my limited imagination? Am I to much coined by software from Cadence or Altium?


robertferanec , 04-23-2018, 09:04 AM
I just think this is more a hobbyiest or amateur approach to start a design
I agree.

I keep saying: PCB Layout is just a small part of the whole project. Same for Schematic - it is just a small part of something much bigger.

If you are designing simple boards, maybe advantages of professional approach are not so visible (professional approach may even looks like it is slowing down the whole project - e.g. generating professional manufacturing outputs may take same time as designing the board).

However, here are a few examples what may happen if you are not seeing the bigger picture:

- if you do not think about how components are going to be purchased, you my end up with board which is very hard to manufacture due very high minimum order quantities, very long lead time, end of life components. So in schematic a component may look awesome (it does exactly what I need!), but in reality it is extremely hard to buy the component and build the board. If you only think about schematic, you may not see that.

- of course, you do not need to include heatsink, screws, mounting holes in the schematic, but then when people are generating BOMs or during layout, they may forget about it - and they keep adding the components into BOMs over and over every time when they need to create new board variant

- when you design a lot of boards, you really do not want people keep asking you about your past projects ... e.g. what is replacement for a component (because they can not get the component which you randomly found on internet), what is order number for the screws which we used in prototypes, etc ...

People usually start to care, when they had to do a lot of these things by themselves and they know how hard or easy it can be if it is (not) done properly.
joe_ls , 04-24-2018, 08:11 AM
Thank you, Robert.
It's always interesting to see other people work habits and pick up some good advice. Especially from experienced pcb designers.
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