PCB Design Process: From RFQ to Manufacturing Release

1. Preparing the PCB Design RFQ

The RFQ is the starting point for defining the work. A complete package allows the PCB designer to understand the technical requirements, identify missing information and estimate the effort more accurately.

Useful RFQ information may include:

• Approved or preliminary schematics
• Existing PCB source files
• Mechanical board outline
• Mounting-hole locations
• Connector locations
• Component-height restrictions
• Keepout areas
• Enclosure or chassis requirements
• Required EDA platform
• Existing symbols, footprints and libraries
• Preferred layer count or stackup
• Controlled-impedance requirements
• Differential-pair and length-matching requirements
• Fabrication and assembly requirements
• Required deliverables
• Target schedule
• Planned review milestones

The selected design environment should also be confirmed at the beginning of the project. 911EDA supports major PCB design platforms including Altium Designer, Cadence Allegro, Cadence OrCAD and Siemens PADS.

The RFQ should also explain the current status of the design. A new layout based on an approved schematic requires a different level of effort than a targeted revision to an existing board. A platform conversion, legacy-board update or library-development assignment will also have its own requirements.

When complete information is not yet available, a preliminary review may still be useful. The designer can identify the missing inputs needed before the work begins.

Teams preparing to request a PCB design quote should provide sufficient information to define the intended board, the required work and the expected release package.

2. Reviewing the Schematic and Design Requirements

Before layout begins, the schematic and supporting requirements should be reviewed for completeness and consistency.

This review does not replace the customer’s electrical-design responsibility. Its purpose is to identify layout-related questions, missing information and requirements that may affect placement, routing or manufacturability.

Important review areas may include:

• Power architecture
• Grounding approach
• High-speed interfaces
• Memory buses
• Differential-pair assignments
• Analog inputs and outputs
• Switching-power circuitry
• RF sections
• Isolation requirements
• Connector pin assignments
• Test points
• Redundant or safety-related signals
• Programming and debug interfaces
• Mechanical restrictions
• Thermal considerations

The designer also needs to understand how the circuitry should be partitioned. Sensitive analog circuits, high-speed digital interfaces and switching-power sections often have different placement, routing and return-path requirements.

Questions discovered during schematic review should be resolved before they become layout problems. For example, an unclear connector assignment may affect placement and routing channels. A missing impedance requirement may affect the stackup. An incomplete footprint may prevent reliable component placement.

911EDA can work from an approved customer schematic or provide schematic capture services when schematic development, revisions, hierarchy or library work are included in the project scope. For a detailed look at the steps involved before PCB layout begins, review our schematic capture process guide.

3. Defining Scope, Deliverables and Schedule

Once the design package has been reviewed, the project scope should be documented clearly.

A well-defined scope identifies:

• The work 911EDA will complete
• The source files that will be provided
• The EDA platform and version
• The required output package
• Customer review responsibilities
• Project milestones
• Target completion date
• Assumptions and exclusions
• How changes will be handled

Projects with stable requirements and clearly defined deliverables may be suitable for fixed-price quoting. Projects with changing requirements, incomplete information or frequent engineering changes may be better supported on an hourly basis.

The schedule should account for more than routing time. Library validation, stackup planning, component placement, customer reviews, mechanical coordination and final documentation all require time.

Defined review milestones may help prevent major changes late in the project. A typical project may include reviews after initial placement, critical routing, major design completion and final release preparation. Learn how a staged PCB design approval process can help reduce downstream rework and control project schedule, scope and cost.

The agreed deliverables should also be identified before work begins. These may include native schematic files, native PCB files, libraries, fabrication outputs, assembly outputs, drawings and revision documentation.

A clear scope definition helps both the customer and the PCB designer understand what constitutes project completion.

4. Library and Footprint Verification

Component-library quality directly affects PCB design.

A library may include:

• Schematic symbols
• PCB footprints
• Pin assignments
• Component parameters
• Manufacturer part information
• Courtyard information
• Assembly data
• 3D models

Existing customer libraries should be reviewed before use, particularly when they contain legacy components or incomplete data.

Critical footprints should be checked against current manufacturer drawings. The review should confirm pad dimensions, pad spacing, pin numbering, component orientation, exposed-pad requirements, mechanical dimensions and applicable assembly information.

Library discrepancies can create serious risk. An incorrect pin assignment may connect signals incorrectly. An inaccurate footprint can create assembly problems. A missing courtyard or incorrect body outline can interfere with placement and mechanical fit.

For high-density designs, reliable library data becomes even more important. Fine-pitch BGAs, dense connectors and tightly spaced components leave little room for late footprint corrections.

When required, 911EDA can create new symbols and footprints, correct existing libraries and validate important component data as part of its PCB library and component engineering services .

5. PCB Stackup and Design Constraints

The PCB stackup influences routing, controlled impedance, power distribution, return-current paths and manufacturability.

Stackup planning may include:

• Total layer count
• Signal-layer allocation
• Ground-plane locations
• Power-plane locations
• Core and prepreg structure
• Finished board thickness
• Copper weights
• Controlled-impedance requirements
• Differential-pair geometry
• Via structures
• Microvia use
• Fabricator capabilities

The stackup should support the required electrical performance while remaining practical for fabrication.

High-speed signals generally benefit from adjacent reference planes. Power-distribution needs may affect plane allocation. Dense BGA routing may require additional signal layers or selective microvias. Board thickness and copper-weight requirements can also limit the available construction options.

Early fabricator involvement may help confirm material availability, impedance feasibility and construction details. The final stackup should reflect both the electrical requirements and the capabilities of the intended PCB fabricator.

The design constraints should then be entered into the EDA system. These may include:

• Trace widths
• Differential-pair spacing
• Length limits
• Length-matching tolerances
• Clearance rules
• Creepage rules
• Via restrictions
• Layer restrictions
• Component-class rules
• Room or region constraints

Constraint management helps turn the design requirements into enforceable layout rules.

6. Component Placement

Component placement establishes the board’s physical structure and strongly influences routing quality.

The placement process normally begins with fixed mechanical elements such as:

• Board outline
• Mounting holes
• Connectors
• Switches
• Displays
• LEDs
• Heat sinks
• Enclosure interfaces
• Restricted areas

Critical circuitry is then placed according to electrical and functional requirements.

Placement decisions may consider:

• Signal flow
• Critical path length
• BGA escape feasibility
• Analog and digital partitioning
• Switching-power loop area
• Power-distribution paths
• Thermal performance
• Component-height restrictions
• Test access
• Assembly access
• Return-current paths
• EMI and EMC concerns

Large processors, FPGAs, memory devices and fine-pitch BGAs often require placement studies before the surrounding components are finalized. Connector location and pin assignment may also have a major effect on routing congestion.

Power converters should be placed to control high-current loops and noisy switching nodes. Sensitive analog circuitry may require separation from digital and power sections. Decoupling capacitors should be positioned according to the device’s needs and the available connection geometry.

Placement should be reviewed before full routing begins. Major placement changes made late in the project can affect many completed connections and increase schedule risk.

For a detailed look at the physical board implementation stages, including placement planning, critical routing, power and plane development, verification and manufacturing release, review our PCB layout process guide.

7. PCB Routing

Routing converts the logical connections in the schematic into physical copper paths on the PCB.

The routing sequence usually prioritizes the most constrained signals first.

These may include:

• High-speed serial interfaces
• DDR memory
• Clock signals
• Controlled-impedance nets
• Differential pairs
• Precision analog signals
• RF paths
• High-current power paths
• Isolation boundaries
• Critical timing signals

Controlled-impedance traces must follow the approved stackup geometry. Differential pairs should be routed with appropriate spacing, coupling and reference-plane continuity. Length matching should be applied where required by the interface or device specifications.

Return-current paths should be considered throughout the routing process. A signal may meet its trace-length requirement but still create problems if it crosses a plane split or loses a continuous reference path.

BGA breakout calls for careful planning. Escape routing, via selection, layer transitions and available routing channels all affect the feasibility of the design. Microvias may be useful in congested areas, but they should be applied selectively and coordinated with the fabricator.

Power routing should account for current requirements, voltage drop, copper area and connection to planes or pours. Switching-power paths should be kept compact where possible.

Analog and mixed-signal routing requires careful attention to noise coupling, grounding, shielding and separation from fast digital or switching nodes.

After critical routing is complete, the remaining connections can be routed while maintaining the established constraints and design intent. For projects that begin with an approved schematic and defined requirements, review our dedicated PCB layout services.

8. Design Review and Verification

Completing the routing does not mean the design is ready for release.

The board should undergo a structured review and verification process.

Automated checks may include:

• Design-rule checking
• Unrouted-net verification
• Clearance checking
• Differential-pair verification
• Length and matching checks
• Via-rule checks
• Component-placement checks
• Board-boundary checks
• Silkscreen checks

Automated DRC is essential, but it cannot confirm every aspect of design quality.

A manual review should also evaluate:

• Return-current continuity
• Reference-plane transitions
• Routing through sensitive areas
• Power-distribution paths
• Connector congestion
• BGA breakout quality
• Analog and digital partitioning
• Switching-node placement
• Thermal considerations
• Mounting and keepout compliance
• Mechanical fit
• Test access
• Fabrication practicality
• Assembly practicality

The design should also be compared with the schematic and project requirements. Critical interfaces and constraint groups should be reviewed individually rather than relying only on a general “no violations” result.

Customer reviews may be conducted at defined milestones. These reviews provide an opportunity to confirm placement, routing decisions, connector assignments and mechanical requirements before release.

A design-for-manufacturing review can help identify fabrication or assembly issues that may not appear in the electrical design rules.

9. Manufacturing Release Package

The manufacturing release package contains the files required to fabricate, assemble and document the PCB.

The exact package depends on the customer and manufacturing partners, but it may include:

• Gerber files
• ODB++ data
• IPC-2581 data
• NC drill files
• Fabrication drawing
• Assembly drawing
• Pick-and-place data
• Solder-paste data
• Bill of materials support
• PDF schematics
• PDF drawings
• Native schematic files
• Native PCB files
• Library files
• Stackup documentation
• Impedance requirements
• Revision records
• Readme or release notes

The fabrication drawing should communicate the applicable construction, dimensions, tolerances, drill information, finishes and other board requirements.

The assembly package should identify component locations, reference designators, polarity information and any special assembly notes.

Native source files are important because they allow the customer to maintain, revise and reuse the design. Delivering only manufacturing outputs can limit future control of the project.

Before release, the files should be checked for consistency. The revision identifiers, drawing information, output data and source files should all correspond to the same approved design state.

10. Support After Release

PCB design support may continue after the initial manufacturing release.

Fabricators and contract manufacturers may have questions about:

• Stackup details
• Impedance requirements
• Drill information
• Via structures
• Drawings
• Copper features
• Panel considerations
• Assembly notes
• Component orientation

Prompt technical communication helps resolve these questions without delaying production.

Prototype fabrication and assembly may also generate feedback. Minor documentation updates, controlled engineering changes or manufacturing clarifications may be required.

When design revisions are needed, they should be documented carefully. Changes should be incorporated into the native source files, reviewed and released under the appropriate revision.

Lessons from the prototype build can also be applied to later production versions, cost-reduction efforts or future products.