Multilayer varistors (MLVs)
Radio frequency series
7.5
Adhesive application
Thin or insufficient adhesive causes chips to loosen or become disconnected during curing.
Low viscosity of the adhesive causes chips to slip after mounting. It is advised to consult the
manufacturer of the adhesive on proper usage and amounts of adhesive to use.
7.6
Selection of flux
Used flux should have less than or equal to 0.1 wt % of halogenated content, since flux residue
after soldering could lead to corrosion of the termination and/or increased leakage current on the
surface of the component. Strong acidic flux must not be used. The amount of flux applied should
be carefully controlled, since an excess may generate flux gas, which in turn is detrimental to sol-
derability.
7.7
Storage of CTVSs
Solderability is guaranteed for one year from date of delivery for multilayer varistors, CeraDiodes
and ESD/EMI filters (half a year for chips with AgPd terminations) and two years for SHCV and
CU components, provided that components are stored in their original packages.
Storage temperature:
Relative humidity:
ꢁ25 °C to +45 °C
≤75% annual average, ≤95% on 30 days a year
The solderability of the external electrodes may deteriorate if SMDs and leaded components are
stored where they are exposed to high humidity, dust or harmful gas (hydrogen chloride, sulfurous
acid gas or hydrogen sulfide).
Do not store SMDs and leaded components where they are exposed to heat or direct sunlight.
Otherwise the packing material may be deformed or SMDs/ leaded components may stick togeth-
er, causing problems during mounting.
After opening the factory seals, such as polyvinyl-sealed packages, it is recommended to use the
SMDs or leaded components as soon as possible.
7.8
Placement of components on circuit board
Especially in the case of dual-wave soldering, it is of advantage to place the components on the
board before soldering in that way that their two terminals do not enter the solder bath at different
times.
Ideally, both terminals should be wetted simultaneously.
7.9
Soldering cautions
An excessively long soldering time or high soldering temperature results in leaching of the outer
electrodes, causing poor adhesion and a change of electrical properties of the varistor due to
the loss of contact between electrodes and termination.
Wave soldering must not be applied for MLVs designated for reflow soldering only.
Keep the recommended down-cooling rate.
Please read Cautions and warnings and
Important notes at the end of this document.
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