1. Define the Capacitance the Circuit Actually Requires

Begin with the role of the capacitor in the released design. Ask the circuit owner what capacitance requirement must be met at that node and under which operating conditions. Keep that requirement separate from the catalogue nominal value. A procurement spreadsheet should preserve the original approved part while identifying the application evidence needed to review a candidate.

Murata explains that high dielectric constant ceramic capacitors can change capacitance when DC voltage is applied. Its FAQ contrasts that behaviour with temperature-compensating ceramic types such as C0G. This supports asking for the relevant characteristic data; it does not supply a universal loss percentage for every MLCC or establish a particular candidate's performance.

Record the intended voltage across the capacitor, the relevant temperature conditions and the design owner's required minimum or permitted range. If those inputs are unavailable, leave the review incomplete rather than applying an assumed derating factor. Identify who can approve the requirement and whether it belongs to one operating mode or several modes of the equipment.

  • Keep nominal capacitance and the application requirement separate.
  • Record the intended DC voltage and operating conditions.
  • Assign an owner to unresolved circuit requirements.

2. Link the Exact Part to Its Characteristic Data

Use the complete manufacturer ordering code, including the documented dielectric, package, tolerance and voltage option. Confirm those fields against the actual product information rather than expanding a shortened description from memory. Keep a reference to the manufacturer page or data file so engineering can identify which part the comparison covers.

Murata's characteristic-data FAQ describes using SimSurfing to view bias, temperature and other electrical characteristics, compare part numbers and export data. That is a manufacturer-specific source route. The same preparation principle is to retain the exact item and the conditions attached to the data; it does not require a particular tool or prove that an exported curve is a guaranteed acceptance limit.

For the review record, note the document or export date, selected conditions and whether the information is typical data, a specification or a model. Ask engineering to resolve differences between the data basis and the intended application. Do not transfer a curve from a similar case size or another series to an unidentified code, or present a missing curve as a confirmed result.

  • Link data to the complete ordering code.
  • Preserve the selected conditions and data classification.
  • Identify missing or inapplicable evidence before comparison.

3. Compare Candidates Against One Approved Requirement

Build a comparison row using the same application inputs for the approved part and each candidate. Include the nominal value, exact identity, characteristic reference and design-owner decision. Where a supplier provides only a catalogue description, mark the technical comparison pending. The buyer should be able to see which requirement has evidence and which still depends on clarification.

Keep the capacitance review bounded. Other characteristics may matter to the circuit, but the responsible engineer should specify them rather than assuming that DC-bias information settles every substitution question. Ask whether separate checks of the footprint, temperature classification, assembly conditions or other application limits are needed. Record those checks as additional requirements with their own evidence.

If engineering needs simulation or measurements on the actual equipment, retain that evaluation status beside the candidate. Murata advises confirming suitability under actual conditions and equipment. A public FAQ cannot stand in for that decision. This article provides a comparison workflow, without a measured customer example or a claim that ICULTRA has qualified the proposed capacitor.

  • Use one defined voltage and operating-condition basis.
  • Keep supplier descriptions separate from technical review results.
  • Preserve the engineering decision and remaining evaluation needs.

4. Send a Quote Request for the Defined Capacitor

After the design decision, send the approved complete code and quantity as the confirmed inquiry line. Attach the relevant technical requirement or reference when it is appropriate to share. If alternatives may be considered, name the review owner and ask suppliers to identify their proposed codes separately. A substitute should not be written under the original component's identity.

Record the accepted evidence reference in the controlled BOM or its linked review record. If the design owner changes the capacitor, identify the revision and affected rows before a supplier quote is treated as comparable. The related BOM guide covers that version control; the general RFQ guide covers wider delivery, packing and commercial inputs.

For an ICULTRA sourcing review, provide the exact capacitor requirement and any unresolved candidate questions. State whether the request concerns the existing approved code or proposals needing engineering review. Ask for current availability and offer conditions for each identified item. The technical checklist helps define the request, while the written supplier response establishes the actual offer scope.

Sources and further reading

Murata's public guidance supports the DC-bias and data-source discussion. The comparison record is a preparation suggestion; this article supplies no part-specific curve, measured result, engineering approval or availability promise.