The Design Process

Our goal at Largo Circuit Design is to produce the highest quality designs in the most expedient way possible. The most effective way to achieve our customer’s goals is to be flexible and attentive.

Here we outline our work process on a typical design job. It describes the input requirements, milestones, options and deliverables.

While this is not intended to serve as a a contract or an agreement, our intention is to familiarize you with the design process and to enhance the communication between our service bureau and our clients.

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    Step 1: Quotation

    First, a quote will be provided within 24 hours. A price estimate will be provided if no minimum input is provided.

    Standard Input | This is the information we typically prefer to have to prepare an accurate quotation.

    • Board size
    • Parts list (BOM)
    • Schematic drawings
    • Technology description:
      • High Speed
      • Analog
      • Mixed Signal
      • RF
      • Power Supply / Servo
      • Backplane
      • PCMCIA
      • Flexible board
      • SMT (one or two sides)
      • MCM
    • Special requirements:
      • Number of layers
      • Impedance and termination
      • Cross talk avoidance
      • Differential pairs
      • Length control and matching
      • Placement restrictions
      • Height restrictions
      • Heat sinking
      • Any special routing requirements
      • ATE test probes
    • Netlist format
    • Deliverables required
    • Applicable documents
    • Design system preference, if any

    Minimum Input | This is the minimum information we need to prepare an accurate quotation.

    • Board size
    • Parts list (BOM)
    • Schematic drawings
    • Technology description
    • Deliverables Required

    Step 2: Work Start

    It is best to start a job when all the items listed on the “Standard input” are available.
    This way the “clock starts ticking” and the work can be continuous and flow uninterrupted.

    Standard Input | Needed data

    • Mechanical drawing with all dimensions clearly noted and fixed components location specified
    • Readable schematics with all reference designations shown
    • Netlist or .DAT files
    • Data sheets for all components. The data sheets should provide the following information:
      • Part body and pins dimensions
      • Internal electrical description
      • Pin numbers and polarity
        (The pin numbering on the data sheet must match the
        netlist provided!)
    • Placement guidelines:
      • Block diagram
      • Suggested placement if available
      • Height restrictions
      • Keep outs
      • Parts grouping and associations
    • Applicable documents if different than MIL-STD-275F and IPC-2221
    • Layer stackup requirement
    • Any other information, documents, samples, etc. that can help us better understand the nature of the project and its requirements
    • Special routing instructions:
      • Controlled impedance lines
      • High current lines
      • Clock lines
      • Shielded lines
      • Length controlled lines
      • Matched length lines
      • Differential pairs
      • Connection sequences
      • Noise sensitive lines
      • Special lines to layer assignment

    Minimum Input | We can start working once we have these items

    • Purchase Order number
    • Any one of the following:
      • Mechanical drawing
      • Netlist
      • Available data sheets

    For boards that have critical design parameters, like impedance control, fine lines, tight spacing and the like, it is recommended that a board manufacturer be selected early on and be put in touch with us. This way the critical board parameters will be reviewed and approved by the manufacturer and guaranty smooth transition to fabrication.

    Step 3: Parts Placement

    After all necessary data has been received and processed, the board parts placement will be completed and the following items sent to the customer for approval:

    • Placement drawing: A plot showing parts location, pins polarity and pad size. The format of the file can be PDF, DXF or the actual design file. Free viewers are available to view the design file.
    • Netlist: as derived from the board database on our CAD system.
    • Layer count and order and routing parameters.

    If the customer has comments regarding the parts placement, they will be implemented and a new set of files will be sent for approval. This process will repeat until the customer is satisfied and approves the placement. At this point routing can begin.

    Step 4: Routing

    During the routing phase all the board interconnections will be made, as well as parts renaming and silk screen (legend) design. The following items will be sent to the customer for approval:

    • Check plots (same format as was used for placement check):
      • Assembly drawings (with old reference designators)
      • Etch layers (with old reference designators)
      • Silkscreen (with new reference designators)
    • Netlist
    • Rename report
    • Swap report
    • Length report
    • Manhattan report

    The customer needs to approve the routing and silkscreen as depicted in the plots.
    If the customer has comments regarding the routing, they will be implemented and a new set of files will be sent for approval.
    This process will repeat until the customer approves the routing. At that point the board is ready to be finished and the design package
    can be completed.

    Step 5: Completion

    After routing approval, all remaining tasks are completed. Using an extensive checklist, all aspects of the design will be revisited and checked and the design package items will be created.

    The Design Package / Deliverables include:

    • Board GERBER files
    • Gerber files description
    • Apertures list
    • NC Drill tape
    • IPC-D-356 netlist
    • Machine control files
    • Parts placement data
    • Fabrication drawing
    • Assembly drawing

    Other items are available and will be delivered at that point, if ordered:

    • Design database
    • AutoCAD DXF/DXB files
    • PDF files
    • Test probe data
    • Laser photoploted films and contacts
    • Fabrication data transmitted directly to the board manufacturer
    • Any special reports or files


    If prototype manufacturing and/or assembly is ordered directly from Largo, it will start immediately after the design package is completed, unless otherwise instructed by the customer.


    Changes during the original design cycle:

    It is well known and understood at Largo that changes and modifications are an almost unavoidable part of the design process.

    A reasonable amount of time (up to 6 hours) is allocated for E.C.O.s in the original price.

    The customer has to be aware that excessive changes might disrupt the work scheduling and result in delays longer than the actual time they take to implement.

    To minimize the adverse impact on cost and schedule, the customer is encouraged to notify Largo as early as possible about impending changes.

    New revision changes:

    After a design has been completed and delivered, the project is considered closed. Any changes from that point on are consider a new job (Revision role).

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