Frequently Asked Questions

Coilcraft products are compatible with a wide range of commercial cleaning systems. 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. For this reason, we have standardized our testing on pure water and alcohol. Details

Yes, core and winding loss data for many of our power inductor are included in our on-line core loss calculator.
A detailed discussion of core and winding losses is provided in Inductor performance in dc-dc converters.

The first six characters of the lot code represent the date code. Details

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.

For these series, we will continue to support existing customers (with previous order history).

Manufacturing processes have consistently improved, and all of our ceramic chip inductors now fall into the 5% or better tolerance range. These parts, in essence, are an improvement of the parts you used to buy.

Electrostatic discharge (ESD) testing is typically performed on active components such as transistors or ICs which 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. In order to minimize risk of damage to other, more sensitive components, Coilcraft uses low ESD packaging wherever feasible.

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.

Gate drive transformers are typically limited by the volt-time product rating of the transformer. The peak primary current (Isat) can be estimated using the equation V = L × di/dt, and rearranging it in the form Isat = V × T/L
Where, V × T is the volt-time product in volt-µsec, L is the inductance in µH, and it is assumed that di/dt is approximated by Isat/T.

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: http://www.modelithics.com/mvp/coilcraft/

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.

Theta JA, Theta JC, Rja and Rjb are terms applicable only to active devices, such as integrated circuits. Inductors 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. 

Almost all of our parts are RoHS compliant, but not necessarily lead free. Any lead present in our RoHS-compliant parts is within allowed limits or is explicitly exempt in the RoHS directive.
Please read Coilcraft RoHS policy.

Coilcraft's Critical Products and Services Group offers products designed and tested specifically for these applications. Address your needs in an email to cp@coilcraft.com, or fax quote requests to 1-847-639-1508.

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.

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. 

All of our air-core inductors and many of our RF chip inductors are non-magnetic. Inductors with all ceramic cores like our CS, DS, HP, HQ, PA, HC, CT, HS, and HT series contain no magnetic material.

All power products, shielded inductors, and chip inductors with ferrite cores (AF series) or ceramic/ferrite cores (LS series) are magnetic and do not meet your requirements.

There can be outgassing from any material under the right conditions but as a general rule outgassing has not been reported with Coilcraft parts in commercial applications and testing has not been required. For specialized applications where outgassing is a particular concern, we recommend you contact our Critical Products group for products that have passed NASA low outgassing specifications

Many Coilcraft chip inductors and some power inductors are marked with dots for identification. For an explanation of the color dots, please see RF Inductor Color Coding or Power Inductor Color Coding.

Part identification is specific to each product series. Refer to the part's data sheet for specific part identification markings. In the case of very small parts, a marking may not be used. In these cases, traceability to the original packaging information is required for accurate identification.

Power inductors, except for our smallest series are commonly marked with 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 number of zeros. Therefore, 103 would be 10 plus three zeros, or 10000 nH, equivalent to 10 µH.

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.

Yes, many Coilcraft parts may be potted, but 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.

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.

Coilcraft products are typically not certified by UL, CSA. TUV, CE or other agencies. However, we are ready to provide data necessary to help customers obtain approvals for their finished products. Safety standard listings generally 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. More information

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

Design Support Tools page Quickly zero in on the optimal part with these easy-to-use tools

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.

SM power inductor selection chart  A visual guide to power inductor size and performance.

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

Competitor cross-reference  Find Coilcraft alternatives to other manufacturers’ part numbers

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

Our on-line SEPIC Inductor Selector tool will step you through selecting the right coupled or separate inductors for your SEPIC application.The design procedure used in this tool is explained in Selecting Coupled Inductors for SEPIC Applications

These three application notes contain in-depth discussions:
Common Mode Filter Design Guide, Common Mode Filter Inductor Analysis and Data Line Filtering.

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.

The shelf life of Coilcraft inductors depends on the inductor type and packaging and may be affected by high levels of humidity, pollution or other contamination. Shelf life is generally greater than one year if in original, sealed bag packaging. If the bag is open or damaged, the shelf life may be affected.

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.

Coilcraft RoHS parts can be soldered using lead-based solders. As with soldering with lead-free solder, there are many factors that 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

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.

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.

The electro-magnetic fields created by inductors generally only interact with metallic surfaces or other inductors in very close proximity. The extent of interaction depends on a number of application factors, including the current through the inductor, the axis of orientation to each other and the distance between them. The minimum spacing between inductors depends on the orientation to each other and the sensitivity of the end-use application to the interaction. Coilcraft cannot advise on minimum spacing between inductors. Shielded inductors are designed to minimize this interaction. Orienting the coil axes of two inductors perpendicular to each other also helps to minimize interaction.

A machine ready reel has a tape leader that is not populated with parts. 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. A leader can be added for a nominal cost.

Thermal resistance is not specified for Coilcraft inductors because they are mostly open frame style and not solid, homogenous bodies like molded IC packages. These body styles have a variety of thermal flow paths and multiple heat sources (winding and core) as opposed to an IC that may generate heat in a specific junction and conduct heat consistently throughout a solid body. You can calculate an approximate thermal resistance by dividing the temperature rise due to Irms current (e.g. 40°C rise) by the power required to generate that rise.
(Power = DCR × Irms²)
Rth (in °C/W) = 40°C ÷ (DCR × Irms²) where DCR is in Ohms and Irms is in Amps.

Where tin is used in terminations, Coilcraft applies one or more of the tin whisker mitigation techniques described in  the iNEMI Recommendations on Lead-Free Finishes for Components Used in High-Reliability Products Version 4 (12-1-06).

The weight of a Coilcraft part is typically specified on the data sheet for the part. In the case of a part series, a weight range may be given that covers the entire series.