3312 - 2 mm SMD Trimming Potentiometer

AVHT Series - High Temperature Automotive Grade Varistors

Specifications are subject to change without notice.

Users should verify actual device performance in their specific applications.

Soldering Recommendations for SMD Components

Popular soldering techniques used for surface mounted components are Wave and Infrared Reflow processes. Both processes can be

performed with Pb-containing or Pb-free solders. The terminations for these soldering techniques are NiSn Barrier Type End

Terminations.

End Termination

Designation

Recommended and Suitable for

RoHS Compliant

NiSn End Termination

AVHT Series...Ni

Pb-containing and Pb-free soldering

Yes

Wave Soldering

This process is generally associated with discrete components mounted on the underside of printed circuit boards, or for large top-side

components with bottom-side mounting tabs to be attached, such as the frames of transformers, relays, connectors, etc. SMD varistors

to be wave soldered are first glued to the circuit board, usually with an epoxy adhesive. When all components on the PCB have been

positioned and an appropriate amount of time is allowed for adhesive curing, the completed assembly is then placed on a conveyor and

run through a single, double wave process.

Infrared Reflow Soldering

These reflow processes are typically associated with top-side component placement. This technique utilizes a mixture of adhesive and

solder compounds (and sometimes fluxes) that are blended into a paste. The paste is then screened onto PCB soldering pads specifi-

cally designed to accept a particular sized SMD component. The recommended solder paste wet layer thickness is 100 to 300 µm. Once

the circuit board is fully populated with SMD components, it is placed in a reflow environment, where the paste is heated to slightly above

its eutectic temperature. When the solder paste reflows, the SMD components are attached to the solder pads.

Solder Fluxes

Solder fluxes are generally applied to populated circuit boards to keep oxides from forming during the heating process and to facilitate

the flowing of the solder. Solder fluxes can be either a part of the solder paste compound or separate materials, usually fluids.

Recommended fluxes are:

• non-activated (R) fluxes, whenever possible

• mildly activated (RMA) fluxes of class L3CN

• class ORLO

Activated (RA), water soluble or strong acidic fluxes with a chlorine content > 0.2 wt. % are NOT RECOMMENDED. The use of such

fluxes could create high leakage current paths along the body of the varistor components.

When a flux is applied prior to wave soldering, it is important to completely dry any residual flux solvents prior to the soldering process.

Thermal Shock

To avoid the possibility of generating stresses in the varistor chip due to thermal shock, a preheat stage to within 100 °C of the peak sol-

dering process temperature is recommended. Additionally, SMD varistors should not be subjected to a temperature gradient greater than

4 °C/sec., with an ideal gradient being 2 °C/sec. Peak temperatures should be controlled. Wave and Reflow soldering conditions for SMD

varistors with Pb-containing solders are shown on the next page in Fig. 1 and 2 respectively, while Wave and Reflow soldering conditions

for SMD varistors with Pb-free solders are shown in Fig. 1 and 3.

Whenever several different types of SMD components are being soldered, each having a specific soldering profile, the soldering profile

with the least heat and the minimum amount of heating time is recommended. Once soldering has been completed, it is necessary to

minimize the possibility of thermal shock by allowing the hot PCB to cool to less than 50 °C before cleaning.