AC08FSM datasheet(150/223 Pages) TECCOR

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AN1005

Application Notes

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AN1005 - 2

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Thyristor Product Catalog

Reflow Soldering Zones

Zone 1: Initial Pre-heating Stage (25 °C to 150 °C)

•

Excess solvent is driven off.

•

PCB and Components are gradually heated up.

•

Temperature gradient shall be <2.5 °C/Sec.

Zone 2: Soak Stage (150 °C to 180 °C)

•

Flux components start activation and begin to reduce the

oxides on component leads and PCB pads.

•

PCB components are brought nearer to the temperature at

which solder bonding can occur.

•

Soak allows different mass components to reach the same

temperature.

•

Activated flux keeps metal surfaces from re-oxidizing.

Zone 3: Reflow Stage (180 °C to 235 °C)

•

Paste is brought to the alloy’s melting point.

•

Activated flux reduces surface tension at the metal interface so

metallurgical bonding occurs.

Zone 4: Cool-down Stage (180 °C to 25 °C)

Assembly is cooled evenly so thermal shock to the components

or PCB is reduced.

The surface tension of the liquid solder tends to draw the leads of

the device towards the center of the soldering area and so has a

correcting effect on slight mispositionings. However, if the layout

is not optimized, the same effect can result in undesirable shifts,

particularly if the soldering areas on the substrate and the com-

ponents are not concentrically arranged. This problem can be

solved by using a standard contact pattern which leaves suffi-

cient scope for the self-positioning effect (Figure AN1005.3 and

Figure AN1005.4) Figure AN1005.5 shows the reflow soldering

procedure.

Figure AN1005.3

Minimum Required Dimensions of Metal Connection

of Typical DO-214 Pads on Hybrid Thick- and Thin-

film Substrates

Figure AN1005.4

Modified DO-214 Compak — Three-leaded Surface

Mount Package

Figure AN1005.5

Reflow Soldering Procedure

After the solder is set and cooled, visually inspect the connec-

tions and, where necessary, correct with a soldering iron. Finally,

the remnants of the flux must be removed carefully.

Use vapor degrease with an azeotrope solvent or equivalent to

remove flux. Allow to dry.

After the drying procedure is complete, the assembly is ready for

testing and/or further processing.

0.079

(2.0)

0.110

(2.8)

0.079

(2.0)

Pad Outline

Dimensions are in inches (and millimeters).

0.079

(2.0)

0.040

(1.0)

0.030

(0.76)

0.079

(2.0)

0.079

(2.0)

0.110

(2.8)

Pad Outline

Dimensions are in inches (and millimeters).

1. Screen print solder paste

(or flux)

2. Place component

(allow flux to dry)

3. Reflow solder

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