Multilayer Varistors
The Varistors/components shall be placed on the PC
board such that both electrodes are subjected to uniform
stresses, or to position the component electrodes at right
angles to the grid glove or bending line. This should be
done to avoid cracking the Varistors from bending the
PC board after or during placing/mounting on the PC
board.
2. Adhesives for Mounting
(1) The amount and viscosity of an adhesive for
mounting shall be such that the adhesive shall
not flow off on the land during its curing.
(2) If the amount of adhesive is insufficient for
mounting, the Varistors may fall off after or during
soldering.
(1) To minimize mechanical stress caused by the
warp or bending of a PC board, please follow the
recommended Varistors’ layout below.
(3) If the adhesive is too low in its viscosity, the
Varistors may be out of alignment after or during
soldering.
Prohibited
Recommendded layout
(4) Adhesives for mounting can be cured by
ultraviolet or infrared radiation. In order to prevent
the terminal electrodes of the Varistors from
oxidizing, the curing shall be done under the
following conditions:
Layout the Varistor sideways
against the stressing direction.
160°C max., for 2 minutes max.
(5) Insufficient curing may cause the Varistors to fall
off after or during soldering. In addition, insulation
resistance between terminal electrodes may
deteriorate due to moisture absorption. In order to
prevent these problems, please observe proper
curing conditions.
(2) The following layout is for your reference since
mechanical stress near the dividing/breaking
position of a PC board varies depending on the
mounting position of the Varistors.
3. Chip Mounting Consideration
(1) When mounting the Varistors/components on a PC
board, the Varistor bodies shall be free from
excessive impact loads such as mechanical impact
or stress due to the positioning, pushing force and
displacement of vacuum nozzles during mounting.
(2) Maintenance and inspection of the Chip Mounter
must be performed regularly.
E
D
Perforation
C
A
B
Slit
Magnitude of stress A>B=C>D>E
(3) If the bottom dead center of the vacuum nozzle is
too low, the Varistor will crack from excessive force
during mounting.
(3) The magnitude of mechanical stress applied to the
Varistors when the circuit board is divided is in the
order of push back < slit < V-groove < perforation.
Also take into account the layout of the Varistors
and the dividing/breaking method.
The following precautions and recommendations
are for your reference in use.
(a) Set and adjust the bottom dead center of the
vacuum nozzles to the upper surface of the PC
board after correcting the warp of the PC board.
(b) Set the pushing force of the vacuum nozzle
during mounting to 1 to 3 N in static load.
(c) For double surface mounting, apply a supporting
pin on the rear surface of the PC board to
suppress the bending of the PC board in order to
minimize the impact of the vacuum nozzles.
Typical examples are shown in the table below.
2.5 Mounting Density and Spaces
If components are arranged in too narrow a space,
the components can be affected by solder bridges
and solder balls. The space between components
should be carefully determined.
■ Precautions for Assembly
1. Storage
(1) The Varistors shall be stored between 5 – 40°C
and 20 - 70%RH, not under severe conditions of
high temperature and humidity.
Item
Prohibited mounting
Recommended mounting
The supporting pin does not
necessarily
have
to
be
(2) If stored in a place that is humid, dusty, or contains
corrosive gasses (hydrogen sulfide, sulfurous acid,
hydrogen chloride and ammonia etc.), the solderability
of terminal electrodes may deteriorate.
positioned beneath the Varistor.
Crack
Single surface
mouting
Supporting
pin
In addition, storage in a place subjected to heating
and/or exposure to direct sunlight will causes
deformed tapes and reels, and component sticking
to tapes, both of which can result in mounting
problems.
Double surface
mounting
Supporting
Separation
of Solder
Crack
(3) Do not store components longer than 6 months.
Check the solderability of products that have been
stored for more than 6 months before use.
Design and specifications are each subject to change without notice. Ask factory for the current technical specifications before purchase and/or use.
Should a safety concern arise regarding this product, please be sure to contact us immediately.
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