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Q. What is a Net List?
Q. If I have my circuit schematics & netlists in non ORCAD format, can you design the PCBs?
Q. If I have my drawings in Autocad or some other non-gerber format, can you make the PCBs?
Q. What is the difference between NET LABEL and ANNOTATION?
Q. What is Back Annotation?
Q. What does the Design Rule Check do at the completion of the layout?
Q. What information and files are needed by you so that you can quote for the Layout design and subsequent PCB fabrication?
Q. Why it is desirable to capture the circuit schematics in a Schematics capture software package?
Q. What are the various steps in the Circuit Schematic Capture process?
Q. What are the various steps in the PCB Layout design process?
Q. What is a Net List?
Netlist is the set of all the pin connections of the various components that comprise a particular schematic or project.
Q. If I have my circuit schematics & netlists in non ORCAD format, can you design the PCBs?
Yes, the PCB layout design software needs the netlists and the libraries of the parts, and proceeds from there. Some translation may be required here; it will depend on case to case. It may not always be possible to back annotate your original schematic diagram with the parts allocation changes made at the time of circuit layout design. As a general rule, our designers will avoid making any part allocation changes on their own; and if they make any changes, suitable ECOs will be documented.
Q. If I have my drawings in Autocad or some other non-gerber format, can you make the PCBs?
Yes; but remember that PCB fabrication requires files in Gerber format. Hence all the other format files need to be converted to Gerber format. That is a semi-automatic process; one cannot rely on the accuracy of Translation software packages to produce error free and 100% accurate translations.
This would involve feasibility study, extra time and effort. After examination of your source files, we can say if the work is doable. Many times, it would be best to reenter the circuit schematics in a Schematics Capture package and proceed from there.
Q. What is the difference between NET LABEL and ANNOTATION?
Annotation is only a note for the readers benefit; A NET LABEL is a tool to connect two or more points with the same NET LABEL.
Q. What is Back Annotation?
If certain parts - like gates, resistors etc that are contained in the same package are interchanged at the PCB layout stage for the sake of better layout, one needs to change the circuit schematics and the Netlists accordingly, and this modification is called "Back Annotation". Many PCB CAD packages are able to do Back annotation in an automatic manner. Otherwise we have to do it manually, and the re-export the revised Netlists to the PCB CAD package.
Q. What does the Design Rule Check do at the completion of the layout?
When the LAYOUT is complete, a Design Rule Check operation is performed to test the PCB layout against the Netlist and the set of previously specified design rules. DRC will report any rule or netlist violations encountered. These are then corrected by the designer.
It is also important to check Hole sizes of the Pads for correctness before the design is released to production.
It is also a good practice for the Fabrication department to separately check all the drawings & files for accurate manufacturability.
Q. What information and files are needed by you so that you can quote for the Layout design and subsequent PCB fabrication?
You should provide us with the following information:
· Net List and Circuit Schematics
· Parts List and their details & package sizes/ footprints- This gives an idea about their size, the number of parts and the total number of pins/pads involved.
· A mechanical drawing of the board or its size
· Any critical considerations in the design like shielding, EMI, Control Impedance, Differential matched pairs, tuned nets etc.
If you do not have complete information listed above, you should still send us whatever information you have in whatever form (it should be readable). It is possible to give you estimates of the quote based on whatever information you have sent and our sales engineer's subsequent discussions with you.
Please send the information to: quotes@pcbdesignexpress.com
What information and files are necessary to start the PCB layout design?
· A complete Circuit Schematic and Netlist.
· A fabrication drawing giving the board outline, board size, type of material and other fabrication details.
· A drawing showing the placement of any fixed components.
· A PARTS LIST of all components .
· Data/ specification sheet for each component. ( you can also give web URLs of each vendors part's data sheet.)
· Special/ Custom design Rules that need to be followed in the design. This will include all the design and routing requirements, testability, critical signals, minimum spacings, impedance matching requirements, differential pairs etc.
Q. Why it is desirable to capture the circuit schematics in a Schematics capture software package?
A Schematic Capture package captures the circuit schematics. From the schematics, it will generate a Netlist. This Netlist will be used as input to the PCB Layout CAD package.
The use of a schematic capture package makes it possible to link the circuit schematic with the final layout; and this makes it possible to run a Design Rule Check to verify that the final PCB matches the original schematics.
Q. What are the various steps in the Circuit Schematic Capture process?
· The process starts with the allocation of PCB Drawing number, Version number, Project name and any other ID name that may be required.
· Appropriate components are taken from the component library (most Schematic Capture packages have Component Libraries), placed on the schematics, and are edited if required to ensure that the component package details & silkscreen legend to be printed on the PCB are as per requirements. If a component is not in the library, the component is defined and its definition and details are added to the component library.
· Existing library components may need to be further edited to reflect the actual circuit diagram, and this may require that the pins of a particular component have to be moved around as per desired circuit schematics.
· Once all the parts have been placed on the schematics, then all the required connections between pins for of various components are drawn. This is done in a manner so as to ensure very good readability; many times two pins that need to be connected together are physically connected ny a connecting line on the schematic, rather they are given the same Net Label. A Net Label always means a connection to all Net Labels of the same name.
· After all the connections have been made on the schematics, a NETLIST is prepared automatically by the Schematic capture package.
Q. What are the various steps in the PCB Layout design process?
You should visit our section on Design Services and Processes.
The above section attempts to address the regular queries that our website users might have, we eagerly look forward to other queries and suggestions from you, please write to us at info@pcbdesignexpress.com
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For details of our entire design services portfolio, click here.
PCB Design Express
1068 West Evelyn Avenue
Sunnyvale, CA 94086
Send files at files@pcbdesignexpress.com
Contact us at 408-731-2550; Fax: 408-731-2551
Email at sales@pcbdesignexpress.com
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