Recommended Soldering

Conditions

Since Chip resistors come into direct contact with melted solder during soldering, it is exposed to potential mechanical stress caused

by the sudden temperature change. The chip resistors may also be subject to silver migration, and to contamination by the flux.

Because of these factors, soldering technique is critical.

•There are 3 soldering methods.

- Flow(wave) soldering.

- Reflow soldering. (Reflow soldering is broadly divided into the total heating method and local heating method.)

- Iron soldering.

•Features

PCB

solder

Primary wave

Secondary wave

There are two types of soldering methods in flow(wave) soldering.

One is single wave soldering, the other is a double waves soldering.

However, double waves soldering is mainly used. This method is

designed so that the continuous and multiple dipping processes

by waves of solder having completely different primary and

secondary characteristics and waveforms.

With the primary wave, a comparatively strong jet flow is used

to remove the flux gas and to solder.

With the secondary wave, it is used to remove excessive solder.

With the primary wave, the solder flows into a very small gap

between components and air bubbles remaining on the soldered

joint are removed.

With the secondary wave, the peel back is used to prevent bridging.

•Preheating

If a chip component is heated suddenly during soldering, it may be

cracked by the thermal shock caused by the temperature difference

between the surface and the inside of the chip. To prevent this,

a full preheating is necessary. In case of wave soldering, the

temperature difference between solder and surface of the

component is kept within 150℃. Also when cooling is done by

dipping into solvent, care should be taken to keep the temperature

difference within 150℃.

•Standard Soldering Condition

Soldering must be carried out without exceeding the approved

soldering temperature and time shown within the shaded area

of the right graph. An excessively long soldering time or high

soldering temperature results in leaching of the outer terminations.

When a PCB is warped, mechanical stress applied to the chip will

be increased and might be a cause of chip crack, especially if there

is big amount of solder on the chip. So, care should be taken not

to use excessive amount of solder on the PCB. For the flow(wave)

soldering, the solder amount can be controlled by land size.

Soldering Methods

Reflow Soldering

Total Heating

Local Heating

Laser

Wave Soldering

Single Wave

Double Waves

Infrared Ray

Iron Soldering

Convection/Infrared

Hot Air

Hot Plate

Optical Beam

Air Heater

< Flow Soldering>

Abstract

Flow(wave) Soldering

Pre-heating

120 sec. min.

Time(sec.)

Soldering

Temp.(

℃)

Pre-heating

Temp.(

℃)

Gradual Cooling

in the air

245

±10℃

5 sec. max.

(Ⅰ)1206(3216) and below

:150

℃ max.

△T