MBV109T1 Datasheet, PDF (4/8 Pages) ON Semiconductor – Silicon Epicap Diodes

MBV109T1 MMBV109LT1 MV209
SOLDER STENCIL GUIDELINES
Prior to placing surface mount components onto a printed
circuit board, solder paste must be applied to the pads. A
solder stencil is required to screen the optimum amount of
solder paste onto the footprint. The stencil is made of brass
or stainless steel with a typical thickness of 0.008 inches.
The stencil opening size for the surface mounted package
should be the same as the pad size on the printed circuit
board, i.e., a 1:1 registration.
TYPICAL SOLDER HEATING PROFILE
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 5 shows a typical heating profile
for use when soldering a surface mount device to a printed
circuit board. This profile will 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.
200°C
150°C
100°C
STEP 1
PREHEAT
ZONE 1
RAMP"
STEP 2
VENT
SOAK"
STEP 3
HEATING
ZONES 2 & 5
RAMP"
STEP 4
STEP 5
HEATING ^HEATING
ZONES 3 & 6 ^{ZONES 4 & 7}
SOAK"
SPIKE"
DESIRED CURVE FOR HIGH
MASS ASSEMBLIES
160°C
170°C
150°C
STEP 6 STEP 7
VENT COOLING
205° TO 219°C
PEAK AT
SOLDER JOINT
100°C
140°C
SOLDER IS LIQUID FOR
40 TO 80 SECONDS
(DEPENDING ON
MASS OF ASSEMBLY)
DESIRED CURVE FOR LOW
MASS ASSEMBLIES
50°C
TIME (3 TO 7 MINUTES TOTAL)
T_MAX
Figure 5. Typical Solder Heating Profile
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