Question 1

Please explain how to interpret the ambient temperature of power supplies.

Accepted Answer

A. The intake temperature of the power supply is defined as the ambient temperature of the power supply with forced air cooling type power supplies.

Forced air cooling type power supplies

The location that is not affected by the heat generated from the power supply is defined as the ambient temperature with convection cooling type power supplies. Also, please be careful so that there is no exposure to radiation heat from the power supply.

Convection cooling type power supplies

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Question 2

What is MTBF?

Accepted Answer

A. MTBF (Mean Time Between Failures) is the numerical value that determines the number of repair parts prepared for products that are operating in the market.

(example) If there are 1ꯠ products operating in the market; the number of units that will fail after 100 hours is estimated and the number of products that must be prepared is determined.
The calculation formula used in this case is “1ꯠ units × 100 hours = 100ꯠ hours/units”.
The forecasted number of failures is 100ꯠ ÷ 50ꯠ = 2 units if the MTBF is 50ꯠ hours.
Therefore, there should be replacements ready for 2 units if 1ꯠ of these devices are used for 100 hours.
MTBF calculation values vary according to manufacturer as their calculation methods and calculation conditions are different.
There are two kinds of calculation methods and various environmental conditions depending on how they are combined.
Basic failure rates for parts are figures produced by the American Military Standard MIL STD 217, the JEITA, and so on. This is why there are multiple forms of calculation results.
Calculations are based on parts stress reliability projections and parts count reliability projections.
The generic failure rates for parts are classified by usage environments, and with our part count reliability projections;
Ground, benign: An environment fixed on the ground where people can live
Ground, fixed: An environment fixed on the ground for devices
are assumed for calculations. “Ground, benign

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Question 3

How can I check the useful life of a product?

Accepted Answer

A. In many cases, the useful life of a product depends on the life span of its electrolytic capacitors.
Various types of electrolytic capacitors with different Lo and rated temperatures are used, and the useful life varies depending on these characteristics.
For details, check the Electrolytic Capacitor Lifetime in the reliability data on the technical data pages for each product on the product information website (TDK Product Center).
(For fan-embedded products, check the Electrolytic Capacitor Lifetime and Fan Life Expectancy.)

The useful life of an electrolytic capacitor is generally controlled by a phenomenon whereby the electrolyte evaporates to the outside of the product through a seal. The pace of evaporation depends on the temperature. The Arrhenius equation (the rate doubles for each 10°C increase in temperature) is presented as a representative example of a formula used for calculating the estimated useful life of electrolytic capacitors.

The Electrolytic Capacitor Lifetime in the reliability data indicates the useful life calculated according to the Arrhenius equation assuming use for 24 hours per day, and therefore, the actual useful life may differ depending on the operational status of the customer’s device.
Even in cases where a longer useful life is projected as a result of shorter operating times or lower temperature, however, it is necessary to take into consideration degradation of the electrolytic capacitor seal rubber. It is generally said that it takes 15 years for the seal rubber to degrade.

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Question 4

There are products that indicate time to failures with MTBF and those that indicate time to failures with MTTF&#44 but what is the difference between the two?

Accepted Answer

A. MTBF (Mean Time Between Failures) indicates the average time it takes for a product to become faulty from the time it is first used or from the time it becomes faulty after it has been once recovered.
MTTF (Mean Time To Failure), on the other hand, indicates the time until a product becomes faulty after initial use.
The same calculation methods are used for both, but MTBF is generally used in reference to products that can be repaired and MTTF is generally used in reference to products that cannot be repaired.
We normally use MTBF to represent the reliability of power supply products, but also particularly use MTTF to represent products that are obviously difficult to repair such as compact on-board products.

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Question 5

Please explain what the FIT rate is as the failure rate.

Accepted Answer

A. FIT (Failure In Time) is a unit that represents failure rates and how many failures occur every 10⁹ hours.
For example, there is the occurrence of 10 failures for every 10⁹ hours in the case of 10FIT.
FIT values can be calculated with the formulas below with the MTBF or MTTF shown in the reliability data.

(Formulas)

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Question 6

What is the specific area where the temperature must be measured to find the ambient temperature?

Accepted Answer

A. The ambient temperature is the temperature of the atmosphere around the product so please measure the internal temperature of the device to be mounted on the product.
Please make the measuring point about 5 centimeters horizontally away from the product. If it is on the upper part of the product, it will be affected by factors such as the increasing of self-generated heat and natural convections. Please also note that it can be affected by radiation from the power supply and thus preventing accurate measurements from being made if it is too close.

Figure 1

There are also separate measuring methods for products that are compliant with forced air cooling (products with exposed mounting boards). Refer to the instruction manuals of the respective products for details.

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Question 7

What storage method do you recommend for the power supply?

Accepted Answer

A. 1. Please store it in the package (box).
2. Do not apply excessive vibration, impact, or load directly to the product.
3. Do not expose the product to direct sunlight.
4. Please observe the following conditions for the approximate storage humidity and temperature.
Temperature Range: 5℃ to 30℃
Humidity Range: 40%to 60% RH
*Please avoid storage in a place where temperature and humidity change drastically. Such environments will cause condensation on the product, which
may cause deterioration of the product.
5. After delivery, we recommend that products used no more than 2 years before use.

(When storing products such as on-board products, power module products, and other products which are soldered to the substrate and do not use aluminum electrolytic capacitors)
If more than one year has passed after delivery, check the lead for rust, oxidation, solderability, etc., before use.
Note that SMD-type products may be subject to MSL (Moisture Sensitivity Level) regulations.
Please be sure to check the storage conditions or delivery specifications described in the instruction manual and product catalog.

If stored for a long period of one year or more, there is a concern that the terminal pins will be oxidized, thus making soldering impossible.
Countermeasures to this problem are listed below.
For example, when storing the product for a long period of time, as countermeasures against the oxygen and water that cause oxidation, we recommend that
you perform degassing packaging with a desiccant (silica gel) and store it with emphasis on preventing oxidation of the terminal pins.

(When storing products that use aluminum electrolytic capacitors inside the power supplies, such as unit types, substrate types and some on-board types)
Leakage current of aluminum electrolytic capacitors tend to increase if left unpowered for a long period of time.
This undesirable phenomenon can be improved by applying a voltage to the aluminum electrolytic capacitor, which reduces the leakage current that increases
due to the repairing action of the electrolytic solution.
Therefore, when using a product that has been stored for a long period of one year or more, please be sure to carry out no-load energization for about
30 minutes or more before use.

(Energization conditions)
(1) For products that are more than one year old after delivery
(2) Energization conditions
Input voltage: Rating
Load: 0A
Ambient temperature: Room temperature
Time: 30 minutes or higher

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Question 8

I would like to coat a substrate which is equipped with on-board type power supply. What cautions should I take?

Accepted Answer

A. Please perform masking so that the coating material does not get on the power supply.
If the coating material infiltrates into the power supply, it may enter the gap between internal parts and expand/contract, thus creating the possibility of damage.

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Question 9

If a fan malfunctions&#44 can I replace it myself?

Accepted Answer

A.Please contact us for fan replacement. We will provide a replacement for a fee.
Use the fan’s expected lifespan in the Reliability Data as a guide when it is time to replace the fan.
Please contact our nearest service center at least 3 to 6 months before the replacement date.
If the fan is replaced by the customer, the product safety standards (UL, CE, etc.) will not apply.
Note that the product warranty will also be voided.
Please note that fan replacement is not available for discontinued products that are no longer supported.

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