Support Center

We've put together some commonly asked questions to give you more information about Coilcraft services and products we offer.

Frequently Asked Questions

Cleaning / Washing

What cleaning solutions can be used on Coilcraft's parts?
Coilcraft products are compatible with a wide range of commercial cleaning systems. Many of our customers use cleaning systems without reporting problems. However, cleaning systems involve many variables, including mechanical forces, vibration, pressure, temperature, number of cycles, and cleaning solvents. Ultrasonic cleaning involves repeated vibratory forces that may cause fatigue in fine wire components and may lead to crack propagation in core materials. Cleaning solvents may include neutralizers, surfactants, saponifiers, dispersants and anti-foaming agents. For so many possible variations of neutralizers, surfactants, saponifiers, dispersants and anti-foaming agents, it is not practical for Coilcraft to test or make recommendations. Coilcraft tests for resistance to solvents per MIL-STD-202 Method 215 plus an additional aqueous wash. Details

Core and winding losses

Do you have a way to determine the core and winding losses of your power inductors??
Yes, core and winding loss data for many of our power inductors is included in our online core loss calculator.
A detailed discussion of core and winding losses is provided in Choosing Inductors for Energy Efficient Power Applications.

Date code / Lot code

How do I interpret the codes on the label on the reel of parts I received?

Coilcraft reel labels contain a manufacturing date code embedded in the first six characters of the "LOT CODE" field.

The date is in MMDDYY format. In the example below, the code 101314 = October 13, 2014.


Dash numbers

What is a dash number?
The dash number is typically a three-digit code that corresponds to the three numbers that follow the dash in the part number. This code refers to the value in nanoHenries, where the first two digits are the value and the last digit is the multiplier (10^x) or number of zeros that follow.

Therefore, 103 would be 10 × 10^3 (or 10 followed by three zeroes), equals 10,000 nH, equivalent to 10 µH.

Other examples:
  • -394 = 39 × 10^4 = 390000 = 390,000 nH = 390 µH
  • -102 = 10 × 10^2 = 1000 = 1000 nH = 1.0 µH
  • -501 = 50 × 10^1 = 500 = 500 nH = 0.5 µH

Discontinued / Obsolescence / EOL / PCN / PDN

Some of your parts are marked "Discontinued."

While Coilcraft has discontinued a small number of series, we will, when feasible, continue to support existing customers (with previous order history for this series). For many of these parts we have developed a newer series that surpasses the performance of the discontinued part. If you search for the discontinued part on our web site, you will be guided to the replacement part.

Coilcraft can notify your company in the event that products that you purchase are changed (Product Change Notice) or discontinued (Product Discontinuation Notice). Sign up for PCN and PDN emails here.

ESD (Electrostatic discharge)

Do you perform ESD testing on your components?
Electrostatic discharge (ESD) testing is typically performed on active components, such as transistors or ICs that have very thin ESD-sensitive semiconductor junctions. Coilcraft products are not typically susceptible to ESD damage. Therefore, we do not regularly test our products for ESD damage. To minimize the risk of damage to other, more sensitive components, Coilcraft uses low-ESD packaging wherever feasible.

Export Classification Number (ECCN)

Where can I find the ECCN for your parts?
Coilcraft components are subject to the Export Administration Regulations (EAR), but not listed with a specific Export Control Classification Number (ECCN) on the Commerce Control List (CCL). EAR99 items generally consist of low-technology consumer goods and do not require a license in many situations. However, if the proposed export of an EAR99 item is to an embargoed country, to an end-user of concern or in support of a prohibited end-use, a license may be required.

Effects of Ground Plane

How can I predict the changes in inductance, Q and SRF when mounting your RF inductors over a ground plane?
Modelithics has measured many Coilcraft RF inductor series with a variety of different substrate types and thicknesses. They have created global models that scale the substrate-sensitive parasitics for accurate simulations. Their models may be viewed at:

The effects of ground plane proximity depend on inductor geometry and test frequency, along with substrate thickness and dielectric constant. In many cases the effect is fairly small, but it can be significant in very tight-tolerance applications. The interaction of the magnetic field of an inductor with a metal ground plane is a complicated 3D E/M problem that requires careful measurement or simulation under specific application conditions. For this reason Coilcraft cannot quantify these effects in general.

Inductance of transformer secondaries

Transformer data sheets don’t specify the inductance of the secondary winding. Could you please provide it?
We do not provide a specification for transformer secondary inductance. However, it can be calculated as primary inductance times the square of the turns ratio. For example, for a 2 : 1 transformer with a primary inductance of 10 µH, the inductance of the secondary is 10 µH × (0.5)^2 = 2.5 µH.

Junction temperature

Why don't you specify the junction temperature on any of your data sheets?
Theta JA, Theta JC, Rja and Rjb are terms applicable only to active devices, such as integrated circuits. Inductors and transformers do not contain semiconductor material junctions and so do not have the same potential failure modes. Theta JA and Theta JC are therefore not applicable to inductors and transformers.

Moisture Sensitivity Level (MSL)

What is the Moisture Sensitivity Level of Coilcraft parts?
All Coilcraft components have a Moisture Sensitivity Level (MSL) = 1, indicating unlimited floor life at <30°C / 85% relative humidity. To be classified MSL level 1, the component must pass the JEDEC J-STD-020 criteria of 168 hours in a chamber with 85°C / 85% relative humidity.


During testing of our board, there is a buzzing sound from one of your inductors. Is this normal? Can it be eliminated?
Noise is usually due to a mechanical resonance in the component that is excited by the electrical conditions of the circuit, a phenomenon known as magnetostriction, and does not indicate a defect in the part. It is very dependent on the application conditions and not always possible to eliminate by changes to the inductor alone. Changing the switching frequency is often the best way eliminate the noise. Applying a dampening material (electronic-grade encapsulant, potting compound, etc.) may decrease the sound level produced or the increased mass of a larger inductor may dampen or shift the resonance to a different frequency.

Non-magnetic products

My applications require the use of non-magnetic inductors. Which of your products are not magnetic?

All of our air-core inductors are non-magnetic: Air-Core Inductors

All of our ceramic-core RF chip inductors are non-magnetic, with the exception of those with nickel in terminations. Ceramic Chip Inductors

Please contact us for any specific inquiry.


Why don't you provide polarity markings on all of your parts?
Unlike capacitors or diodes, inductors do not have a functional polarity and work equally in either direction, so polarity is not important in the vast majority of end-use circuits. On rare occasions, it has been reported that some inductors perform better when mounted in one particular orientation, due to interaction with nearby components or ground plane conductors. Any asymmetrical performance is very much a function of the application, especially board layout. For further comments on board layout see our sections on part spacing (minimum recommended inductor spacing) and shielding. For any applications in which inductor polarity is critical please contact Coilcraft.

Potting / Conformal coating / Encapsulating

Can Coilcraft parts be potted?
While many Coilcraft parts may be potted, it is difficult to generalize about the possible effects of potting or coating. Potential considerations include differing thermal expansion coefficients of the potting compound vs. the inductor materials and changes in overall inductance and capacitance of the potted component vs. the original component. We recommend testing specific application conditions to determine the effects of any proposed potting material.

Power ratings

What are the power ratings for your inductors? They are not specified on your data sheets.

There is a reason that we do not specify power ratings for our inductors. The more meaningful rating for inductors is the rms current rating. Inductor rms current ratings are derived by applying dc or low frequency ac current and measuring the resultant temperature rise. This allows for an accurate determination of temperature rise vs rms current, which can easily be related to temperature rise vs power loss by Power Loss = Irms2 × DCR.

In practice inductor losses can include high frequency core loss, skin effect and proximity effect, which can add to the temperature rise. While these losses are application dependent and should be verified in situ, Coilcraft offers tools for predicting frequency effects. Core loss, conductor loss, and temperature rise can be estimated using the Core & Winding Loss Calculator.

ESR vs frequency for chip inductors can be graphed using the RF Inductor Comparison Tool.

Ratings (Inductance, Q, DCR, SRF, Current, Voltage, Temperature)

Do you have any documents describing the electrical specifications on your data sheets and how they are tested?


Can Coilcraft products be returned?
Custom made parts and/or CPS components are non-cancelable and non-returnable.

Coilcraft standard products can be returned within thirty (30) days of receipt of product by contacting Customer Service Department for a Return Material Authorization (RMA). Returned merchandise must be in original packaging and conform to minimum package requirements. Returned merchandise may be subject to a restocking fee. 

Safety agency approvals

Can you provide UL and other Safety Organizations approvals for your products?
Coilcraft products are typically not certified by UL, CSA, TUV, CE or other agencies. Safety standard listings most commonly apply to complete electronic assemblies such as power supplies, computers, modems, televisions, etc. and not specifically to the high-frequency transformers or inductors that Coilcraft manufactures. In most cases, Coilcraft products are evaluated as part of the end equipment built by our customers; the inductors or transformers are not usually individually listed.

Upon customer request, Coilcraft may obtain specific transformer listings, for example, per UL / IEC 60950 Harmonized Standard for “Safety of Information Technology Equipment.” However, doing so will not automatically qualify the end equipment for agency approval. The manufacturer still has to submit the entire product to UL for approval. Alternatively, Coilcraft can supply certain pertinent information about Hi Pot voltages and insulation to support customers with the approval process on a per request basis.

Some Coilcraft parts are designed to meet specific UL / CSA / IEC or other standards as noted on the particular Coilcraft data sheet.

For more information or further assistance, please contact technical support.

Selecting the best part

Can you help me pick the right inductor for my application?

Yes, we provide many web based tools and applications notes that can help you select the correct part.

RF inductor finder Find every RF inductor that meets your specific requirements.

Power inductor finder Get a sortable list of products that fit your application.

Parametric Search See all available Coilcraft inductors - filter, sort and compare.

Additional Resources are also available on - use the links below:

Converter inductor selector Input your parameters and get detailed inductor specifications.

Flyback transformer selector A structured listing of Coilcraft off-the-shelf flyback transformers.

We also provide cross references to IC applications and competitor parts:

IC / Inductor matching tool  Get a list of Coilcraft parts suitable for 1000s of IC reference designs

Our Application Notes page contains valuable information for selecting the right component for many applications.

How do I select the appropriate parts for my EMI / RFI filter application?
These three application notes contain in-depth discussions:
Common Mode Filter Design GuideCommon Mode Filter Inductor Analysis and Data Line Filtering.
I need a coupled inductor for a SEPIC application. Do you have any guidelines for selecting one?
The design procedure used in this tool is explained in Selecting Coupled Inductors for SEPIC Applications
You don’t have an off the shelf transformer that exactly meets the requirements of my application. Can you provide some guidance to use one of your standard transformers in my application?
Many of our transformers can be adapted to a variety of circuit uses, by considering different connections for the windings. There are, however, many variables to consider when adapting a component designed for one application for use in a different application. Review the application note Using Standard Transformers in Multiple Applications to determine if one of our off the shelf products will work for you.

Shelf life

What is the shelf life of Coilcraft's parts?
For 30°C / 85% relative humidity maximum, our parts are good for indefinite time, whether in or out of packaging (based on MSL-1).

For uncontrolled or unknown environments, our parts are good for one year in packing.
For uncontrolled or unknown environments, our shelf or floor life cannot be certified out of packaging.


What's the advantage of using shielded parts?
The purpose of magnetic shielding is to reduce the amount of magnetic flux generated outside the inductor, in turn reducing the likelihood of radiating energy to nearby components or circuit board traces causing electro-magnetic interference (EMI). Whether a shield is necessary depends on the proximity of other components and how field interaction would affect the performance of the circuit. Field interactions are quite challenging to model and measurement of the final circuit design is recommended. In addition to reducing radiated fields, magnetic shielding typically contributes to the inductance of the component, helping achieve more inductance per given size of inductor.


Can Coilcraft parts be hand soldered?
Most through-hole parts can easily be hand soldered. While our surface mount parts are designed to be reflow soldered, many may be soldered by hand. We do not recommend attempting to hand solder our small chip inductors. Refer to Soldering Surface Mount Components application note for a detailed discussion.
Can I use tin-lead solder with your RoHS-compliant parts?
Coilcraft RoHS parts can be soldered using lead-based solders. As with soldering with lead-free solder, there are many factors that affect solder wetting and need to be taken into account: solder amount, flux, temperature limit of each soldered component, heat transfer characteristics of the circuit board and component materials, and the layout of all components. Details
Can you provide a reflow soldering profile for your parts?
The optimal reflow profile for a circuit board assembly is dependent on the solder material, solder amount, flux, temperature limit of each soldered component, heat transfer characteristics of the circuit board and component materials, and the layout of all components. Therefore, there is no set profile for any of our parts. Refer to Soldering Surface Mount Components application note for a detailed discussion.

Spacing / Board layout

How much space should be allowed between components to counter interactions?
It is not feasible for Coilcraft to recommend a specific minimum spacing between inductors. Electro-magnetic fields created by inductors generally only interact with metallic surfaces or other inductors in close proximity, however the extent of interaction between inductors depends on current (magnitude, waveform shape and frequency), orientation to each other as well as the distance between inductors. (Tip: Making sure to orient the axes of inductors perpendicular to each other, rather than parallel, helps to minimize interaction.) 

Tape and reel

According to your data sheet, I can order my parts on a machine-ready reel, or in tape, but not machine ready. What is the difference?
A machine ready reel has a 400 mm leader of cover tape that includes 100 mm of empty sealed pockets, and a 160 mm trailer of empty pockets sealed with cover tape. The leader is used to thread the tape through your pick and place machine. When you purchase a full reel of parts, the reel comes machine ready. If you purchase less than a full reel, the parts come in tape on a reel, but the tape does not have the leader or trailer. A leader and trailer can be added for an additional cost.