LEARN WHAT IS PCB DESIGN FLOW ?

 In this tutorial we are going to learn about WHAT IS PCB DESIGN FLOW ?

Design Flow Process

Create a set of PCB design flow processes that can used as a guide to step you through the development of a PCB layout. If we follow the best design flow then its helps you avoid duplicating steps. Once you have completed a step, you should never need to repeat it on that design.

1. DESIGN REVIEW

 ̈ The best design review should take place between all applicable disciplines: i.e. hardware Engineer, Project Management, Layout, Mechanical & Manufacturing. For the PCB designer the following information needs to be determined: Layer stack-up & plane layers, PCB thickness & board material, default trace width, component complexity & qty of new components, proto board or production, auto route or manual route, high speed rules, impedance control, test ability and Schedule.

2. COMPONENT DATA SHEETS

Engineering Dept will submit all component data sheets prior to the start date of a PCB layout, of all of the components that can’t be located in your Library Handbook.

3. MECHANICAL DATA SHEET

Engineering Dept will also provide a Board Outline constraint drawing if one is available/ ASAP The mechanical  drawing should be drawn from the top side, include all mounting holes, fixed connector locations, indicate the Layer Stackup & board thickness of the PCB.

4. PART NUMBER & BOARD NAME ASSIGNMENT

After the Engg Dept submits the data sheets, a part no & a board name is assigned to PCB.

5. LIBRARY MANAGEMENT

  As you create library parts, using the naming convention that you developed, populate the applicable blank pages with the new decals, representing the pin assignments & all applicable notes & documentation for each part. Keep the PDF file “Up to Date” every time new parts are built.

6. CUSTOM BOARD OUTLINE

 ̈ Select the correct “Start File” that matches the layering scheme that the Engr has provided & copy the master “Start File” to a new name.

 ̈ Fill out the Title Block.

 ̈ Enter the Board Outline.

 ̈ Add all Mounting/Tooling Holes & Fiducials that are necessary then glue them down.

 ̈ Move the Targets to the outer extremities of the board outline.

 ̈ Fully dimension the board edges & at least one mounting hole.

 ̈ For auto routing should be  Create the “Auto router Keep-in or out” inside the Board Outline.

7. STANDARD BOARD OUTLINE

 ̈ If a Std Board Outline is selected from the Library, the Designer will fill out the Title Block & edit the

text on Layer 26 that will eventually go on the Silkscreen.

 ̈ Setup the correct Layer and Color Scheme.

8. NETLIST

 ̈ At the start of the PCB design, the Engg Dept will provide a net list, from the schematic capture tool.

 ̈ The net list will contain all of the correct Shape Names.

 ̈ The net list will not contain Pin Names over 4 characters long.

 As per given name of PIN should be as per this : Collector = C, Emitter = E, Base = B, Anode = A,

Cathode = K, Source = S, Drain = D, Gate = G, Positive = 1, Negative = 2.

 ̈ Import the net list into Package. If errors are found, in the net list, the Designer will report them to

the Project Engineer. The Project Engineer will fix the problems & provide the Designer with an

updated netlist.

 ̈ After the net list is successfully imported into layout, the Designer will Disperse the parts.

9. REPORTS

 ̈ Create and e-mail to Project Engineer Unused Pins, Part List 2 & Statistic Reports.

 ̈ PCB Designer must review  and make the list for unused components which have two pin.

 ̈ Project Engineer also  must review Unused Pins list of schematic which main project part.

10.PART PLACEMENT

 ̈ The Designer & Engineer will perform the part placement or Engineers suggested layout.

 ̈ The placement must meet the Engrs guidelines & design rules. Engr will provide the DRC.

 ̈ The placement must meet all manufacturing requirements.

 ̈ The placement must meet all routability requirements.

 ̈ Tools/Verify Design – check clearance to ensure no over lapping parts.

11. SPLIT PLANES

 ̈ Use CAM Plane option & use a 2D-Line to separate the different Plane Nets, or use the Split or Mixed Plane option.

 ̈ Use the View or Nets feature to discriminate different nets by color.

12.SILKSCREEN

 ̈ Create Silkscreen (use 0.1mm snap grid) and bottom side etch text.

 ̈ All Ref designators must be moved outside component, & must not exceed 2 different rotations. All Text like company logo and REV must be board inside on TOP side . Default text height/width is .080”/.008” Minimum height/width is .060”/.006”.

13.1ST SET OF QUALITY CONTROL PRINTS

 ̈ 1:1 scale Drill & Assembly drawing laser print/bond paper.

14.FINAL PART PLACEMENT

 ̈ After Split Planes & New library parts are checked, Designer makes final part placement adjustments.

 ̈ PCB Designer will make final silkscreen adjustments.

15.GENERATE OUTPUT FOR MECHANICAL CHECKS USING AutoCAD or PRO-E

TRANSLATORS

16.PREPARE LAYOUT FOR TRACE ROUTING

 ̈ Compare Schematic net list with the PCB Design net list using Netcheck Tools.

17.SETUP DESIGN RULES

 ̈ Setup DRC on “Default Clearance” rules and …

 ̈ Setup DRC on “Net Clearance” rules are to be set up for Voltage, GND & Critical Nets.

 ̈ Set class rules for high speed technology.

18.MANUAL ROUTING

 ̈ Manually Bus route memory sections using Copy or Paste command.

 ̈ Manually fanout all powers that connect to an inner layer plane using Via Share technique.

 ̈ Manually fan out all GND connections so that every GND Pin gets its own Via.

 ̈ Manually route all other Voltages that require large trace widths.

 ̈ Manually route all high-speed matched length traces and critical nets.

 ̈ Use Tools or Verify Design or Check Planes to insure 100% fan out of all SMT Plane Pins.

 ̈ Use Tools or Verify Design or Check Clearances to insure no short circuits.

 ̈ If the design is a 2-Layer board, all voltages should be manually routed/Engineers spec.

19.2nd SET OF QUALITY PRINTS

 ̈ Designer will print all layers that were affected by manual routing & give them to the engineer.

 ̈ If the placement and  pad-stacks have changed run check prints of assembly & drill drawing.

20.SIGNAL INTEGRITY OUTPUT

21.FIX ENGINEERS RED-LINED PRINTS

 ̈ Incorporate all of the Project Engineers corrections.

 ̈ If there were many traces, PCB Designer will create a new set of check prints.

22.TESTABILITY

 Below are the following questions:

 ̈ Does every Net need a test point/just some of the nets?

 ̈ Do voltage nets require extra test points?

 ̈ Do non-connected pins need to be testable?

̈ Can vias be used as test points, or do they have to be “Bottom Side” non-drilled Pads?

 ̈ What size do the test points have to be, what is the point to point spacing requirements & amount of pins per square inch?

If PCB Design requires testability on every net, the Designer will add a test point for every net, using

DFT program & place the test points, near the pins, of the net it belongs to.

23.ROUTE REMAINDER OF NON-CRITICAL ROUTES

 ̈ If the PC Board has a large number of production boards made, it must be 100 % manually which can minimize the trace length & layer.

 ̈ If Engineer requested a quick turn prototype, use an autorouter to route remainder of pcb.

 ̈ If autorouting used, clean up the traces on all layers after the router has completed 100%

 ̈ Make and save a pre-auto routed version of the PCB. This will be use for future revisions.

24.FINAL DRC CHECKS

 ̈ PCB Designer & Project Engr: Tools/Verify Design – Check Clearances, Continuity & Panes.

25.3rd SET OF QUALITY PRINTS

 ̈ Make the  check prints of all Routed Layers, Silk-screens, Solder & Paste Masks.

 ̈ Make the check prints of final AutoCAD Drill & Assembly Drawings.

 ̈ Make final CAE Netlist with final CAD Netlist.

26.FINAL CAM OUTPUT

 ̈Generate final prints of  AutoCAD Assembly & Drill Drawings.

 ̈ Create  Gerber Data, Drill Data & Fabrication Drawing for Febrication.

 ̈ Import the Geber file into CAM350 to extract an IPC-D-356 Netlist.

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