CBM-202PC User’s Manual
35
CITIZEN
1) Thermal Gradient 1
On a sudden temperature increase, unevenness in temperature is produced among package parts of
a surface mounting device, where difference in thermal expansion coefficients of materials can
cause a warp in the package, resulting in damaged chips. Attention, therefore, should be paid to the
upper limit for the increase speed. The lower limit is based on operation efficiency of the reflow
device.
2) Preparatory Heating
The parts and base boards are prepared at a temperature below the solder melting temperature so that
solder jointing is stabilized and thermal shock is lessened. In general, the temperature is set to a level
close to the rated temperature of the surface mounting device.
3) Thermal Gradient 2
The upper limit of increase temperature, as in 1), is determined based on necessity to maintain the
peak temperature and time within the specific range.
4) Peak Temperature and Time
The greatest care must be taken to minimize damage of a package. As a peak temperature directly
influences to reduce package strength and steam pressure inside a package, temperature should be held
low. Also, as steam pressure rises as time passes, set time as short as possible. Conditions shown
here indicate, not in mean values but in the maximum values, the points at which both the above
allowable region and the solder available region are satisfied. On setting conditions, therefore, be
careful not to exceed the upper limit values.
The recommended conditions for the various mounting methods are shown in Figs. 6.2 and 6.3:
Fig. 6.2 Recommended Conditions for Infrared Rays Reflow and Air Reflow
1 to 5
℃
/ sec.
Package
Surface
Temperature
Time
140 to 160
℃
235
℃
max
max. 60 sec.
10 sec. max.
max
1 to 4
℃
/ sec.
Fig. 6.3 Recommended Conditions for Vapor Phase Reflow
1 to 5
℃
/ sec.
Package
Surface
Temperature
Time
140 to 160
℃
215
℃
max
max. 60 sec.
30 sec. max.
max
Summary of Contents for CBM-202PC Series
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