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Read the complete manufacturer part number from the BOM, reel label, purchasing record or approved drawing. A short body code may identify a family without uniquely identifying capacitance, voltage or packaging. Confirm that the supplied item is the approved part, including relevant suffixes. Then locate its terminal diagram, polarity mark and viewing direction in the current datasheet. Save the document revision with the assembly records so that another engineer can reproduce the decision.

Many wet aluminum electrolytic capacitors mark the negative side, while many molded tantalum parts mark the positive side. Solid-electrolyte aluminum constructions can introduce another marking convention. These differences are why a universal stripe rule is unsafe. A photograph in a general guide can teach recognition, but it cannot release an unidentified component for assembly. Nippon Chemi-Con explains its aluminum polarity conventions in its manufacturer FAQ; consult the actual series documentation for the part being ordered.

Do not resolve a missing identification mark by trying both directions under power. Likewise, a resistance or diode-mode reading is not a dependable way to identify the polarity of an unknown capacitor. The meter, charge state, leakage paths and surrounding circuit all affect the observation. A part with damaged or unreadable identification should be quarantined, traced through purchasing records or replaced with a documented item.

A plus sign beside a through-hole footprint normally communicates the designer鈥檚 intended positive terminal, but it still needs to agree with the schematic and footprint pin mapping. A square pad, shaded semicircle or heavy outline is not a universal polarity standard. Libraries use these features differently, and a square pad can simply mean pin 1. Establish what the chosen library means before treating an outline as an assembly instruction.

Check the physical orientation in the PCB editor using the released board revision. Follow the positive device terminal to its numbered pad, then follow that pad鈥檚 net to the schematic. Repeat for the negative terminal. This deliberate two-way comparison catches a footprint with reversed pin numbers even when its silkscreen looks convincing. An assembly drawing should show the component reference and an unambiguous terminal mark that remains understandable after soldering.

Place useful identification outside the body outline where space permits. Do not put critical information only beneath the installed component. If board space cannot accommodate a clear mark, provide an enlarged assembly detail instead of shrinking text until it becomes unreadable. Solder-mask openings and paste apertures serve manufacturing purposes; they should not become the only source of polarity information.

For a polarized capacitor, assess the voltage from its designated positive terminal to its designated negative terminal. Ground is simply a reference node in the circuit. In an illustrative negative supply, the positive terminal may connect to 0 V and the negative terminal to a 鈭�5 V rail. The capacitor then sees +5 V in its intended direction. Copying a rule that the negative terminal must always connect to ground would reverse this arrangement.

Also consider startup, shutdown, rail sequencing and externally driven connectors. A circuit that has the expected DC polarity in steady operation may briefly impose a different voltage during a transient. Capacitor selection must account for the actual operating conditions and manufacturer restrictions. A polarity checklist cannot establish allowable reverse voltage, ripple current, lifetime or surge capability. Those are separate component and circuit design decisions.

Nonpolar ceramic and film capacitors generally do not have a positive and negative installation direction in the same sense. Some other markings can concern construction or identification, so do not interpret every stripe as electrical polarity. For choosing between polarized and nonpolar constructions, use the polarized capacitor selection guide. This page stays focused on identifying and transferring the orientation of the part already specified.

The tool asks whether the part identification, terminal definition, footprint mapping and assembly view have been checked. It records your answers and highlights missing or conflicting evidence. It does not inspect a component photograph, read a CAD file or infer polarity from a selected package type. Choosing 鈥渞ecorded鈥� means that you have supplied a reference; it does not mean 吃瓜tv has reviewed that reference or accepted the build.

For an internal review, enter the component reference, exact part and the drawing or datasheet revision in the evidence field. Record the source used to establish each mapping. If a purchasing substitution changes the manufacturer or package, reopen the review rather than reusing a record based on the previous item. A familiar outline can still contain different pin assignments or polarity indicators.

Generate the record after completing the checks. Editing an input invalidates the previous result and download so that stale information is not silently retained. The browser creates a text file locally when you choose Download. The tool does not send the data to an enquiry form, analytics service or approval system. You can attach the reviewed record to your own engineering correspondence when that is useful.

Consider an illustrative assembly in which C18 has a plus sign on the PCB, but the assembly drawing places the manufacturer鈥檚 marked terminal on the opposite pad. First stop the affected build step and record the revisions of the BOM, PCB and drawing. The correct resolution is not a majority vote among the files. Determine the intended circuit nodes from the schematic, confirm the device terminal definition, and identify which artifact is inconsistent with them.

If the footprint pin mapping is wrong, changing only the drawing may leave a future board revision vulnerable to the same mistake. If the footprint is correct but the exported view is mirrored without a clear label, repair the drawing and its export convention. If the supplied part differs from the approved BOM, the component substitution needs a separate engineering decision. Preserve the corrected files as a coherent release, with a change note that explains the affected references.

An assembled suspect part should not be 鈥渧erified鈥� by briefly powering the board and watching for normal operation. Reverse connection can damage the component even when it does not immediately fail visibly. Follow the product鈥檚 controlled rework and inspection process, including any component replacement and electrical checks defined by the responsible engineer. Do not assume that reversing it again restores its original reliability.

For a polarity-related enquiry, provide the PCB revision, affected reference designators, approved manufacturer part numbers, BOM and the relevant assembly drawing. Include the exact question: unknown marking, disagreement between drawing and layout, alternate part evaluation, or review of an already assembled board. A cropped detail can help explain the location, but it should retain enough orientation and reference information to be interpreted correctly.

Keep the board-level circuit requirement separate from the component鈥檚 voltage rating. A higher printed voltage rating alone does not make a replacement suitable. Capacitance, tolerance, ESR or impedance, ripple capability, temperature characteristics, physical fit and lifetime conditions can also matter. The decoupling capacitor guide addresses the circuit role and layout task; the design for assembly review addresses the completeness of placement and manufacturing information.

If the parts are being supplied by the customer, identify the reel or bag labels and any handling instructions. If sourcing is included in the assembly request, specify whether alternatives are permitted and who approves them. These simple decisions prevent an orientation discussion from becoming an informal substitute-part approval. The final enquiry should make both the known facts and the unresolved item visible to the reviewer.

A useful polarity record contains more than a checked box. Record the reference designator, complete approved part number, datasheet revision, positive and negative terminal definitions, footprint pad numbers and assembly drawing revision. If a mark is only visible from one side of the component, state that view. This makes the decision reproducible when another engineer, buyer or assembly operator takes over the job.

For example, a review note could state that C18 uses the approved part listed in BOM revision B, that the marked terminal is identified by a specific datasheet figure, and that its connection maps to pad 2 in the released footprint. The note must say whether pad 2 is positive or negative for that exact item. A phrase such as 鈥渟tripe faces left鈥� is incomplete without an unambiguous view and board datum, and becomes especially fragile when a drawing is rotated.

When an alternate is proposed, compare the marking convention again even if the electrical values appear similar. Update the assembly detail if the physical cue changes. Procurement should retain the approved alternate decision with the material records so that an operator does not have to reverse-engineer it from the delivered reel. The board鈥檚 electrical requirement and the alternate part鈥檚 terminal definition both need to remain visible.

For an already assembled sample, retain the as-built identification and any relevant inspection detail before rework. A photograph should show the reference and orientation clearly, but it should not be used to claim electrical suitability that was not tested. Record what was observed, what remains uncertain and which document resolves the question. This separation of observation and conclusion is particularly useful when the original complaint comes from a field-return board with incomplete history.

The checklist therefore asks for evidence references rather than assigning a confidence percentage. A partially completed record can still be valuable: it identifies exactly what must be obtained before the next step. It is better to hand over a clear unresolved terminal definition than a reassuring score based on a guessed marking rule.

Can lead length identify polarity? It can be a useful clue for certain new through-hole parts, but leads may have been formed, trimmed or reworked. Confirm the series documentation and the actual component condition. Do not use relative lead length as the only evidence for a recovered or unidentified part.

Does the capacitor symbol settle physical orientation? No. The symbol expresses circuit intent; its pins still need the correct mapping to footprint pads. A correct symbol connected to an incorrect library footprint can produce a physically reversed assembly. Review both representations and the exported placement information.

Must all polarized capacitors face the same direction on a board? Consistent orientation can simplify inspection when the circuit and layout allow it, but connectivity determines the required orientation. Do not rotate a device merely to make the board look uniform. Document necessary exceptions clearly.

Can an automated optical inspection result replace this review? Inspection checks an assembled board against a programmed reference. An incorrect reference can reproduce the same design error across every board. Establish the correct part and placement first, then use the agreed inspection and electrical test plan to check the build. Acceptance requirements and responsibilities belong in the project documentation.