Common sense in purchasing inductor components

1. Inductance and allowable error
Inductance refers to the nominal value of inductance measured at the frequency required by the product technical specifications. Inductance is measured in units of Henry, millihenry, microhenry, and nanohenry, and the error is subdivided into: F class (±1%); G class (±2%); H class (±3%); J class (±5%); K class (±10%); L class (±15%); M class (±20%); P class (±25%); N class (±30%); the most commonly used are J, K, and M classes.

2. Test frequency
To correctly measure the L, Q, and DCR values ​​of an inductor, an alternating current must be applied to the inductor to be measured as required. The closer the frequency of the current is to the actual operating frequency of the inductor, the better. Assuming that the inductance value unit is as small as the nanohenry level (NH), the frequency of the measuring instrument is required to be as high as 3G.

3. DC resistance
Except for power inductors, which do not measure DC resistance (only check the wire specifications), other inductors must specify the maximum DC resistance as required, and the smaller the better.

4. Maximum operating current
Take 1.25 to 1.5 times the rated current of the inductor as the maximum operating current. Generally, it is safer to use it with a 50% reduction.

5. Stability of inductance
The ratio of the change in inductance △L/△t caused by a 1°C change in ambient temperature to the original inductance L value is the temperature coefficient a1 of the inductor, a1=△L/L*△t. In addition to the inductance temperature coefficient that determines its stability, attention should also be paid to the change in inductance caused by mechanical vibration and aging.

6. Dielectric strength and moisture resistance
For inductors with dielectric strength requirements, the packaging material should be selected with a high voltage resistance. Generally, inductors with better voltage resistance also have better moisture resistance. Resin impregnation, encapsulation, and die-casting processes can meet this requirement.

7. Solder pads or pins
Solder pads or pins are important aspects that cannot be ignored when purchasing and using inductor coils. They are mainly evaluated for their tensile strength, torsion, resistance to welding heat and solderability tests to ensure the reliability of welding.
For SMD inductors (SMD), they must be purchased strictly according to the designed pad size. Inductors with pins generally have no strict regulations on the same parameters and can be interchanged in vertical and horizontal types. They are only specified due to the restrictions on the installation position of the PC board.

8. Packaging of SMD components
All are packaged with carrier tape to avoid mutual collision and extrusion. Based on the requirements of SMT mounting operations for the upper tape of carrier tape packaging, the peeling force of the upper tape of our products is between 20g and 100g. The peeling force of less than 20g is unqualified except for self-adhesive tape. For components with larger volume and heavier weight, heat sealing tape must be used as the upper tape package.

9. Packaging protection
a. The magnetic material of the inductor is fragile. Please handle it with care during transportation and storage;
b. Product packaging: Generally, a small gift box is used as the inner packaging, and a sturdy double-layer carton is used as the outer packaging, which can withstand a maximum pressure of 40Kg.

10. Moisture-proof and anti-oxidation
Our company's products have passed the anti-oxidation treatment and salt spray test before leaving the factory to ensure the good solderability of the product. Desiccant and seal are placed in each small packaging bag and inner box to prevent the product from getting damp.

11. Shelf life
The shelf life of general inductors is within 6 months as the best use period. Products that exceed 6 months need to be re-tested for solderability before they can be used again. The inductors produced by Kodaka have been treated with anti-oxidation, and the best use period of the product can be extended to 8 months.