How it works
X5R is a high-permittivity Class II ceramic. Its internal material can store more charge per unit volume than C0G, enabling compact decoupling and local energy storage. The same dielectric behaviour makes capacitance depend on operating conditions. Applied DC voltage can reduce the available capacitance, temperature changes it further, and capacitance ages after the relevant heat-treatment reference point. The X5R code specifies a temperature-characteristic band; it does not promise that a nominal ten-microfarad device supplies ten microfarads in service. Buyers therefore need exact-part curves or measurements at the intended voltage and temperature, plus a defined aging allowance.
The ceramic separates adjacent electrodes and determines temperature behaviour, bias dependence and losses.
Parameters that matter
- Temperature characteristic
- −55 to +85°C, with specified temperature-related capacitance change within ±15%; this is not the total operating error. (°C; %)
- Effective capacitance
- The capacitance remaining at the design's actual bias and temperature, including the required tolerance and aging allowance. (µF at Vdc, °C and time)
- Rated and maximum applied voltage
- Check the combined waveform against the exact part's voltage conditions. (Vdc; ripple peak V)
- ESR, impedance and self-heating
- These set useful bypass behaviour and ripple heating; nominal capacitance alone cannot predict them. (Ω, Hz, °C)
- Aging and measurement timing
- Time-dependent drift and the reference time after heat treatment; clarify whether quoted curves are typical or guaranteed. (% per decade of time; h)
A worked selection example
Illustrative calculation · not a product guarantee
Will 10 µF deliver a required 6 µF?
Teaching assumptions only: nominal 10 µF; −20% initial tolerance; a combined bias/temperature retention factor of 0.55; aging retention 0.97. These factors do not describe any listed supplier part.
- One capacitor provides 10 × 0.80 × 0.55 × 0.97 = 4.268 µF in this simplified budget.
- One piece misses the assumed 6 µF requirement.
- Two identical pieces in parallel provide about 8.54 µF before layout and frequency effects are considered.
- Compare two parts, a larger case, or another exact MPN using supplier combined-condition data and the regulator's stability requirements.
Order against an effective-capacitance requirement, not a nominal-value match.
Where it fits
Suitable starting points
- Low-voltage rail decoupling and local bulk capacitance
- Compact consumer or embedded products with verified component temperature
- Parallel capacitor banks after checking impedance and regulator requirements
Where to take extra care
- Locations exceeding the exact part's temperature range
- Timing or precision filters that require a stable absolute capacitance
- Direct replacement of a safety-certified or automotive-qualified part without matching that qualification
Series directions to investigate
Compare 0402 through 1210 inch and larger cases only as required by voltage and effective capacitance. A larger case may improve the available design options, but compare exact curves. Fenghua General MLCC publicly lists X5R.
What Chinese suppliers can offer
Where the opportunity lies
Fenghua's general MLCC documentation includes X5R. Common decoupling values are a practical area for evidence-based second-source evaluation alongside local sample and assembly coordination.
What still needs evidence
A matching nominal value, case and voltage cannot establish equivalence. Dense high-capacitance parts can differ materially under bias, and a domestic channel does not prove origin or factory authorization.
Questions for the supplier
- 01
What capacitance remains at our maximum DC voltage and hot/cold limits?
- 02
Are those curves typical, min/max or a guaranteed acceptance criterion?
- 03
What aging reference and allowance should we use after reflow and in service?
- 04
Can you confirm full MPN, case height, reel quantity, manufacturing site and lot traceability?
Technical references
These references support the principles and catalogue directions discussed here. Public documentation is a different evidence level from a supplier reply, a lot document or an independent test. This guide does not claim those later stages have been completed.
- 1. Use outside specified temperature range
- 2. DC bias and capacitance FAQ
- 3. GRM MLCC use cautions and capacitance aging
- 4. General Series Multi-layer Ceramic Capacitors A0006
These guides explain selection principles. Final decisions require the current datasheet for the exact ordering code, operating conditions and appropriate application testing.