NeoDen IN12, User Manual

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melting point of alloy and the desired maximum temperature of reflow.
Before you start, you must have a basic understanding of the ideal temperature
wave. Theoretically, the ideal wave consists of four parts or sections, the first three
regions are heated and the last one is cooled. The more the temperature zone of the
oven, the more accurate and close the profile of the temperature wave can be
achieved. Most pastes can be successfully reflowed with four basic temperature
zones.
(Fig. 2. Theoretically, the ideal reflow wave consists of four zones, the first three
zones are heated and the last zone is cooled.)
It is also used to warm up the ambient temperature of the PCB from the active zone.
In this region, the temperature of the product rises continuously at a rate of no
more than 2-5
℃
per second
If the temperature rises too fast, it will cause some defects, such as tiny cracks in
ceramic capacitors. If the temperature rises too slowly, the solder paste will feel
too much temperature, and there is not enough time for PCB to reach the active
temperature. The preheating zone of the oven generally accounts for 25 ~ 33% of
the total length of the heating channel.
The active area, sometimes called dry or wet area, generally accounts for 33 ~ 50%
of the heating channel, and has two functions. The first is to sense the temperature
of PCB at a relatively stable temperature, allowing components of different quality
to be homogeneous in temperature, so as to reduce their considerable temperature
difference. The second function is to allow the flux to be activated and volatile
substances to volatilize from the solder paste. The general active temperature range
is 120 ~ 150
℃
. if the temperature of the active zone is set too high, the flux does
not have enough time to activate, and the slope of the temperature wave is an
upward increasing slope. Although some solder paste manufacturers allow some
temperature increase during activation, the ideal wave requires a fairly stable
temperature so that the PCB temperature is equal at the beginning and end of the
active zone. Some ovens on the market can not maintain a flat active temperature
wave. Choosing a oven that can maintain a flat active temperature wave will
improve the weld performance, and users will have a larger processing window.
The reflow zone is sometimes called the peak or final heating zone. The function
of this area is to increase the PCB assembly temperature from the active
temperature to the recommended peak temperature. The activation temperature is