Re: PCB

On 1 Mar 2006 13:07:33 -0800, the renowned "Jackie"
<Shuangshuang.Zhou@xxxxxxxxx> wrote:

Hi, guys, I am a layman, I want to know the basic process of PCB.
I was told that the process is:
1. draw out the schematic of the circuit in the software: Orcad, PADS
DxDesigner, or something else.
2. generate the netlist of the schematic

So far, so good. You'd run design rule checks before generating the
netlist. You will likely have to create new schematic entities for
parts not in the libraries.

3. the software will generate the PCB layout automatically according to
the netlist file

No, there is quite a bit of manual work to get from the netlist to the
final layout. You'd want to set constraints on spacing and trace width
for an autorouter. You may wish to route manually, in which case the
program will typically keep you from creating a layout that does not
match the netlist and some of the constraints. You will have to do
much of the placement of parts manually. You will have to create the
board outline manually. Some of the processes can be iterative (you
may find that the parts won't fit on the outline you hoped to use, or
you may find that routing is impossible with the placement you have,
or you may have to add layers to the board). Footprints can be
associated with each component at the schematic stage or at this
stage. Generally you'll have to create new footprints for parts that
are not in the library.

4. the PCB manufacturer will make the PCB according to the layout.

right? Thanks.

When you're done the 'layout', you run Design Rule Checks to ensure
that the desired rules are not being violated. Then you generally
generate Gerber and Excellon files, which the PCB manufacturer can use
to generate film and 'drill tapes' (a file of instructions for the
drilling machines). Some PCB makers work with the design files
directly, which eliminates a step, but it's not a very important step,
and would usually be limited to one or two 'softwares'.



Best regards,
Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
speff@xxxxxxxxxxxx Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com
.

Loading