Nordson 303 779B, Customer Product Manual

Page: 71 / 176

Operation
B 3-9
E
1998 Nordson Corporation
All rights reserved
303 779B
Issued 11/98
Manual 12-44
NOTE: It is important to calibrate the exhaust before creating a profile or
recalling a profile. The exhaust volume should remain constant from the
first day the oven is set-up. If the exhaust stays constant, exhaust
calibration before profiling is not required, but verification should be
performed periodically.
See Figure B 3-1. When creating a curing profile for a circuit board,
follow the substrate, component, and material manufacturers’ guidelines.
Profiles should include:
1. A rise rate of <2
°
C/second (<5) to limit stress on components and
product. A slow rise rate eliminates pock marks and bubbling in
conformal coating by slowing out-gassing.
2. Temperature stabilization at, or slightly above, the cure temperature
for the required cure time. Typical cure temperatures are generally
120
°
C and 150
°
C (248
_
F and 302
_
F). Increasing the cure
temperature will decrease the cure time required. Consult the
material datasheet.
3. Calculate the dwell time by: (cure temp -25
°
C)/(2
°
C/sec) + (cure
time in seconds). Once you know the dwell time for each circuit
board the conveyor speed can be calculated; this will be the
maximum speed. On the other side of the equation is the throughput
requirement; this will be the minimum speed.
1244009A
100
°
200
°
1 2 3
Cure Time
Cure T
emperature
Fig. B 3-1 Curing Profile
The Curing Profile Theory