Resistor Precaution Usage
|Resistor Precautions in Usage
| When an ambient temperature exceeds a rated ambient temperature,
resistors shall be applied on the derating curve by derating the load
power. General resistors are not combustion- resistant and are likely
to emit, flame, gas, smoke, red heat, etc. under overloads. Flame
retardant resistors generally emit smoke and red heat in a certain
power and over but do not emit fire or flame.
When resistors are shielded or coated with resin etc., stress from
the storage heat and the resin are applied to the resistors. So, performance
and reliability of resistors should be checked well before use.
When a voltage higher than rated is applied in a short time (single
pulse, repeated pulses, surge, etc.), it does not necessarily ensure
safety that an effective wattage is not higher than a rated wattage.
Then consult with us with your specified pulse wave shape. Resistors
shall be used in a condition causing no dew condensation.
Keep temperature from rising by choosing resistors with a higher
rated capacity; do not use a component having the exact load value
required. For considerations of safety in extended period applications,
the rating should be more than four times higher than the
actual wattage involved, but never use resistors at less than 25%
of its rated power.
In applications where resistors are subject to intermittent current
surges and spikes, be sure in advance that the components selected
are capable of withstanding brief durations of increased load.
Do not exceed the recommended rated load. Resistors must used within
the rated voltage range to prevent the shortening of service life
and/or failure of the wound resistance elements.
Minimum load: Resistors must be utilized at 1/10 or more of the rated
voltage to prevent poor conductance due to oxidation build-up.For
basic particulars for cautions, refer to EIAJ Technical Report RCR-
2121 "Guidance for care note on fixed resistors".
|Metal Oxide Film Resistors
|All resistors manufactured by Token Electronics Co., Ltd. comply
with the U.S. UL-94 non-flammability test, Class V-0, a continuous
combustion period of zero seconds.
Smoke emitted from non-flammable resistors on initial use in powered
circuits is a normal phenomenon and the component can be safely utilized.Never
use organic solvents to clean non-flammable resistors.
Non-flammable resistors cannot be utilized in oil. Non-flammable resistors
cannot be used in high frequency machinery because of the inductance
produced by the windings.
Although the hardness exceeds that of a 3H pencil lead, do not nick
the coating with screwdrivers or other pointed objects.
Avoid touching non-flammable resistors in operation; the surface temperature
ranges from approximately 350 °C to 400°C when utilized at
the full rated value. Maintaining a surface temperature of 200°C
or less will extend resistors service life.
Less resistant against external shocks than ordinary resistors due
to special flame retardant coating. So, never give shocks or vibrations
on the resistors. Also never damage them by picking up the coated
films with pliers, tweezers, etc. After cleaning, no external power
should be put on the coated films before they are well dried.
A suitable type of resistors must be selected. Contact us for details.
|When being used in AC circuits, some wirewound structures give inductance
ingredients or parasitic capacity, so they may cause unusual phenomena
such as oscillations etc. Quorum deviations of other components should
be carefully taken into account for use.
Application and Placement: Wire wound resistors use different gauges
of wire as resistance elements. Sometimes the gauge is extremely thin
(finer than a strand of human hair) and very susceptible to breakage
in environments containing salts, ash, dust and corrosives. Avoid
utilization in such environments.
Do not install in dusty areas because the accumulation will cause
shorts and poor conductance.
| When using, it shall be made sure that the overload conditions
at unusual moments lie within the fusing territory.
Consult with us in advance when overloaded higher than the rated voltage
under an ordinary situation since such an overload may store up damages
on resistors. Use at the maximum open- circuit voltage or lower as
an arc phenomenon may arise when high voltage is applied again after
fusing by an over current.
Consult with us for the maximum open- circuit voltage because it varies
with type and resistance.
| Care should be taken to the fact that slipping out of position
during mounting may increase to cause solder bridges.
As chip networks receive mechanical stress easier than chip resistors,
take care so that no strong mechanical stress is given during and
after the mounting. An incorrect solder volume increases stress on
resistors and may result in cracks or performance defects. Be careful
to avoid too much or too little soldered volume.
|The types and the specifications in this catalog are typical ones.
Before use, please make sure of specifications and precautions in
use with the contents of specifications for supply or ask our sales
offices for the specifications.
|Particulars Common to all Kinds of Product Types
| When components are used for special applications requiring high
reliability (life maintenance equipment, atomic energy, airplanes,
artificial satellites, etc.), contact us beforehand. Also make sure
to evaluate and verify the components in a state that they are mounted
on actual equipment.
| Soldering shall be performed within the specified temperature,
time and number of times for each component. If the components are
heated to high temperature for a long time, the colors and characteristics
may change, and disconnection may occur.
After soldering, keep the component from stress until it is cooled
After soldering, be sure not to give any mechanical stress on the
terminal section by warping of the printed board, etc.
| The coating is covered to ensure the performance of components.
Do not give any damages or excessive impacts on the products with
pliers or pinsetter, or improper adjustment of an automatic mounter.
They may cause characteristic changes, disconnection, crack, etc.
Do not use the components dropped at the time of mounting or ones
removed from the printed boards.
Make sure to avoid heat radiation generated by other heated components.
In case boards are sealed by molding or coated after mounting components,
consult us beforehand.
Take care not to have electrostatics applied to the components when
| If the components are used in circuits where pulse wave current
(single pulse, repeated pulse) or surge current flows, consult us
beforehand. Also note that it is necessary to check with actual circuits
considering dispersion of the tolerance values of the other components.
| The components should be kept away from high temperature, high
humidity, direct sunlight, heat, corrosive gas (brimstone, chlorine,
acid, alkali, etc.). Please inquire us about the storage term of products.
| Be careful not to leave ionic substances contained in solder flux
after washing the flux. Especially when non-washing- soldering, water
washing or water- soluble detergent is used, it is essential to confirm
reliability of the components before use.
| For basic particulars for cautions, refer to EIAJ Technical Report
RCR-1001 "Safety application guide for electronic parts ".
|Particulars Common to Chip Components
| Warping of printed boards, which is caused by heat, gives stress
directly to components when boards are cooled down. Be careful of
the following particulars:
The arrangement of electrodes of chip components should go along with
the fiber direction (vertical direction) of printed boards.
When printed boards are divided after soldering, proper positioning
of the components is required in order to avoid any stress caused
by warping, bending, etc. of the boards.
Be sure to design the same size of pads both on left and right sides.
If far different sizes of components are mixed on a board, take care
of the positioning of the components.
|Particulars Common to Discrete Components
| To avoid mechanical force to components, pay attention to following
Be careful not to create resonance by vibration.
The bodies of the discrete components should be free from twisting
The bodies of the large components should be firmly fixed.
When the lead wires need to be bent, try to make larger radius of
curve in order to avoid excessive force at the foot of the terminals.
When cutting or clinching the lead wires on the mounter, be careful
not to apply excessive forces to them.