V0402MHS03H Просмотр технического описания (PDF) - Littelfuse, Inc

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производитель

V0402MHS03H

Surface Mount Varistors

Littelfuse, Inc 

Surface Mount Varistors

Multilayer High Speed Transient Voltage Surge Suppressor

MHS Varistor Series

Soldering Recommendations

The principal techniques used for the soldering of components in

surface mount technology are infared (IR) re-flow, vapour phase re-flow

and wave soldering. Typical profiles are shown in Figures 5, 6 and 7.

When wave soldering, the MHS suppressor is attached to the circuit

board by means of an adhesive. The assembly is then placed on a

conveyor and run through the soldering process to contact the wave.

With IR and vapour phase re-flow, the device is placed in a solder paste

on a substrate. As the solder paste is heated, it re-flows and solders the

unit to the board.

The recommended solder for the MHS suppressor is a 63/36/2

(Sn/Pb/Ag), 60/40 (Sn/Pb) or 63/37 (Sn/Pb). Littelfuse also

recommends an RMA solder flux.

Wave soldering is the most strenuous of the processes. To avoid the

possibility of generating stresses due to thermal shock, a preheat stage

in the soldering process is recommended, and the peak temperature of

6.

the solder process should be rigidly controlled. For 0402-size devices,

IR reflow is recommended.

When using a re-flow process, care should be taken to ensure that the

MHS chip is not subjected to a thermal gradient steeper than 4 degrees

per second; the ideal gradient being 2 degrees per second. During the

soldering process, preheating within 100 degrees of the solder’s peak

temperature is essentail to minimize thermal shock. Examples of the sol-

dering conditions for the MHS suppressor are given in the tables below.

Once the soldering process has been completed, it is still necessary

to ensure that any further thermal shocks are avoided. One possible

cause of thermal shock is hot printed circuit boards being removed

from the solder process and subjected to cleaning solvents at room

temperature. The boards must be allowed to cool gradually to less than

50oC before cleaning.

7.

Recommended Pad Outline

5.

TABLE 1: PAD LAYOUT DIMENSIONS

DIMENSION

A

B

C

mm

in mm

in

mm

in

0402 1.70 0.067 0.510 0.020 0.610 0.024

0603 2.54 0.100 0.760 0.030 0.890 0.035

3

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