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iii. Mouse click on Start button.
iv. Allow PCB and component to cool before removing.
c. Profile development
Note: General Information concerning the Profile Development Screen
The Reflow Graph area displays a representation of the Reflow cycle profile.
Time in minutes is graphed along the X-axis and temperature in degrees Celsius
or Fahrenheit is plotted along the Y-axis. The time and temperature axes incorporate
a dynamic scaling feature to optimize the display for extremely short or long profiles.
Profile graphs can be saved with profiles to be used for process validation by
operators while using the Operation screen. Profile graphs can also be stored as
individual records for each rework job for quality control purposes. Solid and dotted
lines are used to indicate profile parameters.
Profile Creation
There are 2 recommended methods for developing a profile. The first, involves an
actual component installation, while the second uses a previously installed package.
Either method can be used to develop a reliable profile. However, there are some
issues and considerations to be aware of with each.
When developing profiles through actual component installation, it is critical to make
sure the thermocouples remain in contact with the solder throughout the entire
process. Unreliable data will be collected should a thermocouple lose contact with
the solder. If measuring the temperature on the top of the package, it is best to use
a preinstalled component, as the thermocouple wire will typically cause the
component to not lay flat on the PCB.
When using a previously installed package, the placement of the thermocouples is
important. They must be in contact with the existing solder joints. This task can be
accomplished by either (1) drilling through the bottom of the PCB into a solder joint
and attaching the thermocouple or by (2) sliding the thermocouple under the
package in the case of a BGA or along side in the case of other SMD's. When sliding
a thermo couple under a component, it is critical that the thermocouple be in contact
with the solder. Method 2 is the most commonly used. Information from the
thermocouples will assist in determining the proper time and temperature
parameters. In general, the following guidelines should be adhered to when
developing profiles.
Ramp and Maximum Temperatures
Acceptable ramp rates and maximum temperatures should be obtained from the
component manufacturer. Typical ramp rates are 2-5 ºC/s (4-9 ºF/s) for plastic parts
and 1 ºC/s (2 ºF/s) for ceramic parts. It is recommended to select a maximum
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Figure 20
System Operations Manual
Page 23 of 38
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