Pace TF 1500 Operation And Maintenance Manual page 25

temperature below the manufacturer's specification to provide for a margin of safety.
Typically, 20 ºC below maximum specified temperature is selected.
Pre-Heat Phase
1. In a "step profile", the top of the PCB and package should reach a stable
temperature of 95-105 ºC. If plotting the temperature curve, the trace will usually
level off within this temperature range.
2. If a "linear slope" is desired, pre-heat and soak phases are combined. Both the
package and the PCB are warmed at a constant ramp rate (usually 2-4 ºC/second)
until the desired soak temperature is reached.
Soak Phase
The soak phase is a crucial part of the reflow process. During this period, the flux
activates and drives off volatiles and excess flux. A temperature of 145-165 ºC
(determined by the activation temperature of the flux used) should be maintained for
approximately 20-40 seconds. This allows for uniform ramping across the entire
package and PCB during reflow.
Reflow Phase
During this phase, the solder reaches solder melt and forms joints between the
package and the lands. It is critical for all areas of the component to reach solder
melt together and all solder joints remain in a liquid state for at least 10-20 seconds.
Generally, plastic packages should not be exposed to temperatures higher than
220 ºC. Always consult the device specifications for maximum temperature
recommendations. As a rule of thumb, a safe "maximum temperature" is the
maximum temp specified by the manufacturer minus 20ºC. Lower temperatures and
shorter times are common in CSPs and FCs. The lowest temperatures possible
should always be used to ensure safety of the device and PCB.
Cool Down Phase
The cool down phase is necessary to bring the temperature of the package, solder
joints and PCB under the package below solder melt temperatures. Cooling should
be controlled. A good reference is to use the same cool down rate as for ramp up.
The cooling fan on the TF 1500 will remain on for a minimum of 30 seconds from the
start of the cool down cycle. Some types of components (like CBGAs) should be
allowed to cool without external assistance from the cooling fan. When installing
these packages, turn the fan away from the PCB so the air doesn't blow on it.
General
Using one of the two baseline (default) profiles will provide a good starting point for
profile development. The reflow graph provides an excellent tool for monitoring
profile parameters and fine tuning or perfecting the profile development process.
When adjusting profile parameters "on-the-fly", all changes are reflected immediately
on the profile development screen and graph.
Procedure
i. If the component needs to be placed first, conduct steps in paragraph 6a
ii. Mouse click on Profile for the Profile Development Screen. (Figure 7)
iii. Conduct steps ii thru v in paragraph 6a.
iv. Position the board so the red laser sighting light is roughly in the center
v. Mouse click the cycle start button. Make adjustments in accordance with
vi. To return to the beginning of the development stage mouse click on the
vii. If you're finished, allow the PCB to cool and remove.
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to step xv then do sections ii, vii thru x below.
of the component. To move the board forward and back simply move
the PCB in the arms. To move the assembly left and right push the
release handle away from you and move the assembly. Pull the release
handle towards you to secure the assembly.
paragraph 5i.
cycle start button.
System Operations Manual
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