How to Cross Reference Capacitors.

Everett Frank Everett Frank August 20, 2025
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Suggesting the wrong capacitor to an engineer is a quick way to get your email ignored. But when a part goes obsolete, is backordered for months, or suddenly costs triple, procurement needs to bring options to the table fast. The trick is knowing which specs are must-match and which can be safely equal-or-better so your recommendation actually gets approved.

This guide walks you through what to check before sending a substitute up for review, so you save time and avoid frustrating back-and-forth.

Read More: Understanding Form-Fit-Function For Electronic Components

Specs That Must Match Exactly

If these don’t align with the original capacitor, the engineer will likely reject your suggestion immediately.

Capacitance Value

This is the primary rating of the capacitor—measured in µF, nF, or pF.

If it changes, the circuit might not work as intended. Unless the engineer specifically says otherwise, find the exact same value.

Case Type

Same size, same shape, same footprint. If the replacement won’t fit on the board or into the housing, it’s a non-starter.

Examples: radial leaded, axial, SMD 1206, SMD 0603.

Part Type

The construction category matters. Ceramic, electrolytic, tantalum, and film all behave differently.

For example:

Electrolytic parts are polarized—installing them backwards can destroy them.

Ceramic parts are non-polarized but can be sensitive to vibration.

Changing part type can alter performance, so keep it the same.

Specs That Can Be Equal or Higher

These are areas where going better is safe, but going lower needs engineering sign-off.

Voltage Rating

Match or exceed the original. A higher voltage rating is fine; a lower one risks failure under load.

Temperature Range

Maximum temperature: higher is okay.

Minimum temperature: same or lower (able to handle colder environments).

Tolerance

Tighter tolerance is usually fine. Looser tolerance can change circuit behavior—check with engineering first.

Dielectric Type

A higher-grade dielectric can improve performance if size and form factor match, but always confirm before changing.

Examples: X7R, X5R, C0G

Compliance & Qualification Checks

Even if the specs line up, these factors can still stop an alternate from being approved.

RoHS / REACH Compliance

Needed for any product sold in Europe, modern default components are no-lead.

Automotive Qualification (AEC-Q200)

Essential if the part is used in a vehicle system.

Moisture Sensitivity Level (MSL)

Higher MSL parts need special handling before soldering, or they can fail during assembly.

Lifecycle Status

 Avoid parts that are discontinued, obsolete, or flagged “Not Recommended for New Designs (NRND).”

Takeaway for Procurement

When you’re sourcing alternates:

  • Start with exact matches for capacitance, case type, and part type.

  • For other specs match or exceed—but never downgrade

  • Check compliance and qualification requirements before proposing.

Bringing the engineer a well-researched alternate shows you understand both sourcing realities and technical needs—making approvals faster and less painful.

Read More: Expert Guide to Cross-Referencing Electronic Components

**Want cross-references at no cost?** Visit X-Refs.com, for comprehensive alternates, parametric differences, and real-time inventory.

Frequently Asked Questions
How to cross reference capacitors? Check which specs must match exactly and which can be equal-or-better, then only propose substitutes that meet those must-match specs before sending them up for engineer review so you save time and avoid back-and-forth.
What is the most important rating of a capacitor? The capacitance value (measured in µF, nF, or pF) is the primary rating; if it changes the circuit might not work as intended, so find the exact same value unless the engineer specifically allows a change.
Why does an engineer reject a suggested capacitor? Because key specs don't align with the original—if capacitance value, case type, or part type differ (and aren't explicitly approved), the replacement will likely be rejected immediately.
Can I use a capacitor with a different capacitance value? Generally no; you should find the exact same capacitance value unless the engineer specifically says a different value is acceptable.
Is case type important when substituting capacitors? Yes. Case type (size, shape, footprint) must match exactly—if the replacement won't fit on the board or into the housing, it's a non-starter. Examples include radial leaded, axial, SMD 1206, and SMD 0603.
What part types should I avoid mixing when cross referencing? Avoid swapping construction categories—ceramic, electrolytic, tantalum, and film behave differently—so part type is a must-match spec.
When should procurement look for substitute capacitors? When the original part goes obsolete, is backordered for months, or suddenly costs substantially more—procurement needs to bring viable options to the engineer quickly.
Do I need engineer approval before finalizing a substitute capacitor? Yes; procurement should check and present substitutes that meet the must-match specs, then get the engineer's review and approval before finalizing the recommendation.
Best approach to avoid frustrating back-and-forth with engineers? Know which specs are must-match and which can be equal-or-better, verify those before proposing substitutes, and only send options that are likely to be approved.
Where to read more about form-fit-function for electronic components? See the linked article 'Understanding Form-Fit-Function For Electronic Components' at https://www.x-refs.com/blog/posts/understanding-form-fit-function-for-electronic-components/ for more detail.