PCB Assembly Polarity and Pin 1 Checklist

PCB assembly polarity, pin 1 and orientation checks must connect the actual component to the intended PCB nets—not merely match two visible marks. Identify the exact manufacturer part number, interpret its package drawing in the stated view, and trace each relevant terminal to the footprint pad and circuit connection. When the silkscreen, assembly drawing or supplied component disagrees, hold the affected placement for engineering disposition. Release it only after the design authority approves the mapping and manufacturing and inspection instructions reflect that decision.

Distinguish Pin 1, Polarity and Orientation Indicators

Pin 1, polarity and orientation answer different questions. Pin 1 identifies a designated terminal in a package numbering system. Polarity identifies an electrical terminal relationship, such as anode versus cathode or positive versus negative. Orientation describes how the component is positioned relative to a board, viewing direction or mating interface. Confirm each separately before deciding that two marks agree.

A pin-1 indicator does not establish a universal positive terminal. For example, the DCK package pin table in the TPS22919 datasheet assigns pin 1 to IN and pin 2 to GND. Its pin configuration is explicitly a top view. The accompanying DCK0006A outline identifies a pin-1 index area; it does not instruct users to interpret every circular feature as pin 1.

Treat a board dot, square pad, chamfered outline or component stripe as a cue requiring interpretation. The release question is not “Which side looks familiar?” It is “Which documented terminal reaches which intended net when this exact part is assembled in this view?”

Keep mechanical direction in the same review. A connector can require a particular cable exit and mating direction as well as correct electrical numbering. Approving one does not approve the other.

Use Component Documentation to Interpret Package Marks

Component documentation must match the actual manufacturer, complete orderable part number and package option. Start with the BOM and received material identity, then collect the pin table, package outline and applicable marking diagram. Include packing information when reel presentation is relevant to setup, but do not substitute a tape-pocket view for a board assembly view.

The following examples demonstrate different documented meanings, not interchangeable marking conventions.

When the actual body differs from an expected dot or notch, request clarification tied to the component photograph and part identity. For example, a photographed TPS22919 required interpretation of its line mark to establish orientation. That component-specific interpretation is not a rule for all line-marked ICs.

A component marking lookup can help establish the identity of a marked part. Use the resulting identity to retrieve the correct documentation; a code match alone is not approval of its placement on your PCB.

Keep an unannotated photograph alongside any marked-up copy. Include the package edges and enough board context to establish the view. An isolated crop of a dot can remove the very reference needed to interpret it.

Compare Footprint, Silkscreen and Assembly-Drawing Intent

Footprint, silkscreen and assembly-drawing review should establish one traceable terminal-to-net mapping. Do not resolve disagreement by counting which files show the same direction: several outputs may inherit the same library error. Identify what each document controls and reconcile it against the component definition and approved circuit intent.

The referenced supplier’s BOM and CPL guidance distinguishes the BOM’s part identity and reference designators from the placement list’s position, rotation and board side. Use that separation during review. A valid part number does not validate the placement data, and a populated placement row does not prove that its footprint pin mapping is correct.

Use this matrix to organize a conflict review. “Primary reference” identifies the evidence to consult, not permission to disregard a conflicting released instruction.

Verify the physical board revision, not just the filename of the supplied artwork. Label every comparison image as component top view, component bottom view, PCB top view, PCB bottom view or connector mating view as applicable. State whether a PCB view is shown from that side or looking through the board.

Silkscreen remains valuable when its meaning is controlled. The referenced supplier’s orientation guidance recommends legend indicators aligned with component documentation. When an assembled body covers the cue, retain an approved inspection reference that does not depend on reading hidden ink.

Resolve Diode, Capacitor and IC Marking Conflicts

A marking conflict is a symptom requiring investigation, not proof that the component, drawing or PCB is wrong. Hold the affected reference designators and material scope while engineering determines whether the problem is identity, view interpretation, pin mapping or a released-document error. Do not quietly rotate parts until the pictures appear to agree.

Use this decision path:

Identify the discrepancy → hold affected placement → freeze the compared revisions → confirm material identity → normalize the views → trace terminal-to-pad-to-net connections → obtain design-authority disposition → update placement and inspection references → verify implementation → release the defined build scope.

Determine what must change

For a diode, write anode and cathode explicitly rather than relying on a stripe-to-stripe comparison. For a polarized capacitor, write positive and negative explicitly. For an IC, trace the numbered terminals and their functions, not just the first corner. Check the complete applicable pin mapping before accepting a library correction.

A drawing-only error may call for a drawing revision. A misleading legend on otherwise correct copper may require an approved, revision-limited exception and clearer assembly instructions. A footprint-to-net error requires design disposition; rotation alone is not an acceptable assumption about its remedy. Evaluate whether board rework, a revised PCB or another approved correction is necessary.

Preserve the approval boundary

Ask the supplier to present the conflict, exact affected parts, evidence and proposed mapping. Assign the customer’s design authority—or its formally delegated engineering authority—to approve the electrical interpretation. Manufacturing translates that decision into build instructions; quality confirms the acceptance reference is usable. A disposition can correct a project instruction, but cannot redefine the device terminals. If the manufacturer references themselves conflict, obtain manufacturer clarification before approving the mapping.

Do not use energization to discover an uncertain capacitor direction. For the FK series, the applicable usage instructions prohibit reverse voltage and require polarity confirmation before use. Any subsequent electrical verification should follow the approved test plan; it does not replace resolving the original documentation conflict.

Apply the Relevant Specifications and View Conventions

Orientation specifications should define the data convention used between design and manufacturing, while manufacturer documentation defines the component terminals. Record both in the release package, with the revisions actually adopted by the project. A familiar standard name is not sufficient evidence that an imported library or placement file implements the intended convention.

IEC 61188-7:2017 addresses electronic component orientation and land-pattern description for CAD-library construction and data transfer. Use the applicable project convention to support consistent communication. Continue to verify the actual part and circuit mapping; a library convention does not turn an ambiguous body mark into an approved terminal identification.

Specify the viewing side, board datum, package identity and terminal naming used in the review. Record the agreed inspection method and evidence retention in the manufacturing acceptance requirements. Keep numerical rotation conversion in the placement-data workflow, after the physical orientation is settled. Neither a default software angle nor a generic pin-1 corner replaces this engineering decision.

Approve Orientation Before Programming the Placement Machine

Placement programming should receive an approved physical orientation and terminal mapping, not an unresolved question. Make that approval the prerequisite for committing the production program. Offline preparation may proceed under a hold, but do not release affected machine instructions or production placement until the disagreement is closed.

Use the following project release checklist to separate responsibilities. These are recommended acceptance gates for the orientation review, not universal machine settings.

Separate “the source orientation is approved” from “the machine implementation is verified.” After programming, compare the setup preview or controlled first-placement evidence with the approved reference, including board side and reference designator. Use the project’s verification sequence before proceeding to the next irreversible operation.

For automated optical inspection, specify what feature the system is expected to recognize. Do not approve an inspection image merely because it was learned from the first assembled board: that would use the build to validate itself. Where the relevant feature is hidden or ambiguous, agree another evidence route before release. An optical comparison alone cannot establish a terminal’s intended electrical function.

Record Confirmed References for Inspection and Repeat Builds

An orientation record should let a different engineer reproduce the decision without reopening an informal conversation. Save the controlled mapping, the documents and images that support it, the approval authority, and the exact build scope. Retain the correction as part of the released package rather than a detached email instruction.

Keep the evidence chain intact

Record the board and assembly revisions, reference designators, manufacturer/order code, package designation and relevant received-lot identity. Store the manufacturer document title, identifier, revision and relevant page or figure, together with the retrieved copy used for approval. A web address alone does not preserve the reviewed content.

Keep both the original discrepancy image and the annotated approved view. Include the terminal names, footprint pads, net names and physical board reference. Attach the engineering change or deviation record, approval identities and dates, placement-program version and inspection-reference version. Identify the superseded drawing or inspection image so it cannot remain an equally valid instruction. Define the applicability and expiry of any temporary exception.

An adequate orientation statement is more precise than “stripe toward connector.” An illustrative format is: “D12 cathode connects to footprint pad 2 on net CLAMP_NODE; anode connects to pad 1 on RETURN. View is PCB top side, with connector J1 at the upper edge.” These invented designators and nets illustrate the required specificity; the project record must use its actual mapping and supporting approval.

Before a repeat build, compare the planned material and document revisions with the approved record. Reopen review when an alternative part, package option, marking change, footprint revision or board revision affects that evidence. A previous successful build is useful context, but it does not automatically authorize a changed configuration.

Five Application Scenarios for Orientation Review

Orientation review is useful whenever the received component or manufacturing data no longer matches the approved reference. The following scenarios illustrate how to apply the checklist; they are not reports of customer builds. In each case, distinguish the observed discrepancy from the cause that engineering must establish.

1. A replacement IC has an unfamiliar line instead of the expected dot

A buyer sources the approved IC, but incoming inspection cannot match its visible line to an old inspection photograph. Hold the affected lot and confirm the full part/package identity. Use the manufacturer’s applicable marking explanation, then check the terminal map. Update the inspection reference only after approval; neither a familiar package size nor readable text settles the question.

2. A diode library calls a different terminal “1”

A footprint library’s terminal naming differs from the component drawing. Compare electrical roles before declaring the board reversed. Document the symbol-pin-to-footprint-pad correspondence and check the resulting nets. Resolve any incorrect mapping through design control; do not renumber a pad in the assembly instructions while leaving the design database inconsistent.

3. Capacitor technologies are confused during review

An inspector applies a negative-marking assumption to a molded tantalum part. Consult the exact series marking drawing and identify both terminals before judging the board. Correct the inspection criterion as well as any assembly instruction affected by the misunderstanding. Keep the reference specific to the approved component rather than issuing a factory-wide rule that every stripe means the same polarity.

4. A connector mating view is mistaken for a board view

The assembly drawing shows the housing from its mating face, while the PCB reference is viewed from the opposite side. Establish the contact numbering and viewing direction from the exact connector drawing. Verify the cable exit against the interface drawing, then issue a labeled installation view. Do not resolve the issue solely by making the latch face the photograph’s edge.

5. A repeat order uses a board with incorrect silkscreen

A repeat-build package includes a PCB revision with a misleading legend that an earlier build handled through an informal instruction. Do not treat that history as continuing authorization. Identify the affected stock, confirm the copper and terminal mapping, and obtain a controlled disposition. Link its permitted scope to the revised assembly and inspection references before releasing that stock.

FAQ

PCBA polarity and pin 1 questions should be answered against the exact part, board revision and controlled release evidence. These answers explain what can establish orientation, what cannot settle a conflict alone, and what must be approved before a build proceeds.

Prepare the Orientation Evidence for Your Next Build

Prepare an orientation review package with the controlled BOM, board revision, schematic or relevant net mapping, placement data, assembly drawing and exact component documentation. Add photographs of the conflicting marks, identify affected reference designators, and name the engineering authority responsible for disposition. Include a proposed correction, but keep unresolved positions on hold.

For a JASPER PCB assembly services enquiry, send that evidence with the build files and the required inspection scope. Agree which approved record will control placement and repeat builds. The next step is a documented orientation decision—not another guess at a dot, stripe or corner.