MTB10N40E

http://onsemi.com

10

RECOMMENDED PROFILE FOR REFLOW SOLDERING

For any given circuit board, there will be a group of control

settings that will give the desired heat pattern. The operator

must set temperatures for several heating zones, and a

figure for belt speed. Taken together, these control settings

make up a heating “profile” for that particular circuit board.

On machines controlled by a computer, the computer

remembers these profiles from one operating session to the

next. Figure 18 shows a typical heating profile for use when

vary among soldering systems but it is a good starting point.

Factors that can affect the profile include the type of soldering

system in use, density and types of components on the

board, type of solder used, and the type of board or substrate

material being used. This profile shows temperature versus

time. The line on the graph shows the actual temperature that

might be experienced on the surface of a test board at or near

a central solder joint. The two profiles are based on a high

density and a low density board. The Vitronics SMD310

convection/infrared reflow soldering system was used to

generate this profile. The type of solder used was 62/36/2 Tin

Lead Silver with a melting point between 177−189°C. When

this type of furnace is used for solder reflow work, the circuit

boards and solder joints tend to heat first. The components

on the board are then heated by conduction. The circuit

board, because it has a large surface area, absorbs the

thermal energy more efficiently, then distributes this energy

to the components. Because of this effect, the main body of

a component may be up to 30 degrees cooler than the

adjacent solder joints.

STEP 1

PREHEAT

ZONE 1

RAMP"

STEP 2

VENT

SOAK"

STEP 3

HEATING

ZONES 2 & 5

RAMP"

STEP 4

HEATING

ZONES 3 & 6

SOAK"

STEP 5

HEATING

ZONES 4 & 7

SPIKE"

STEP 6

VENT

STEP 7

COOLING

200

°C

150

°C

100

°C

50

°C

TIME (3 TO 7 MINUTES TOTAL)

SOLDER IS LIQUID FOR

40 TO 80 SECONDS

(DEPENDING ON

MASS OF ASSEMBLY)

205

° TO 219°C

PEAK AT

SOLDER JOINT

DESIRED CURVE FOR LOW

MASS ASSEMBLIES

DESIRED CURVE FOR HIGH

MASS ASSEMBLIES

100

°C

150

°C

160

°C

170

°C

140

°C