MCR08B View Datasheet(PDF) - Kersemi Electronic Co., Ltd.
Part Name
Description
Manufacturer
MCR08B Datasheet PDF : 9 Pages
| |||
MCR08B, MCR08M
SOLDERING PRECAUTIONS
The melting temperature of solder is higher than the rated
temperature of the device. When the entire device is heated
to a high temperature, failure to complete soldering within
a short time could result in device failure. Therefore, the
following items should always be observed in order to
minimize the thermal stress to which the devices are
subjected.
• Always preheat the device.
• The delta temperature between the preheat and
soldering should be 100°C or less.*
• When preheating and soldering, the temperature of the
leads and the case must not exceed the maximum
temperature ratings as shown on the data sheet. When
using infrared heating with the reflow soldering
method, the difference should be a maximum of 10°C.
• The soldering temperature and time should not exceed
260°C for more than 10 seconds.
• When shifting from preheating to soldering, the
maximum temperature gradient should be 5°C or less.
• After soldering has been completed, the device should
be allowed to cool naturally for at least three minutes.
Gradual cooling should be used as the use of forced
cooling will increase the temperature gradient and
result in latent failure due to mechanical stress.
• Mechanical stress or shock should not be applied
during cooling.
* Soldering a device without preheating can cause
excessive thermal shock and stress which can result in
damage to the device.
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 19 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
STEP 1 STEP 2 STEP 3
STEP 4
STEP 5 STEP 6 STEP 7
PREHEAT VENT HEATING
HEATING HEATING VENT COOLING
ZONE 1
“RAMP”
“SOAK” ZONES 2 & 5 ZONES 3 & 6 ZONES 4 & 7
“RAMP”
“SOAK”
“SPIKE”
205° TO
219°C
DESIRED CURVE FOR HIGH
170°C
PEAK AT
MASS ASSEMBLIES
160°C
SOLDER
150°C
JOINT
150°C
100°C
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)
TMAX
Figure 19. Typical Solder Heating Profile
www.kersemi.com
8
Share Link: 