Technical_reference.pdf - 第94页
Technical Service Manual 94 Revision Dat e: August 2004 CONTRO LLED EXHAUST SYSTEM (AIR ONLY OR OVENS EQ UIPPED W ITH AIR SW ITCHING ) CONT ROLLED EXHAUST SYSTEM (CES) ( Air Mode) This exhaust subs y stem extrac ts heate…
Technical Service Manual 93 Revision Date: August 2004
BOARD SUPPORT
Board Support is:
! Standard, (installed on all ovens) ) An option, (NOT installed on all ovens)
The Board Support is a precision flexible metal belt carrying vertical pins positioned under the Printed Circuit Board during
the process through the oven. The adjustment of the location of the belt under the product is driven by an electric motor.
A selector switch on the operator’s panel operates the motor. If the Board Support is not required for a particular product,
it can be positioned between the fixed rail pin chain. The free space required is 8 mm on one side of the Printed Circuit
Board, facing the Operator.
There must be a clear space of 3mm (1/8 inch) on the bottom side of the PCB for the pins of the CBS.
CONTROLLED COOLING
Controlled Cooling is:
!Standard, (installed on all ovens) )An option, (NOT installed on all ovens)
DESCRIPTION:
The Controlled Cooling System consists of two independent cooling circuits on the oven. The cooling circuits operate by
recirculating a cooling fluid through gas-to-liquid heat exchangers in the cooling cells of the oven and through liquid-to-air
heat exchangers external to the process tunnel of the oven. By adjusting the liquid temperature of the coolant with a
circulation heater and by controlling the external cooling fan, the gas temperature in the cooling cells of the oven can be
controlled.
CONTROL:
The operator interface for adjusting controlled cooling zone setpoints is the same as for the heated zones of the oven. A
controlled cooling equipped oven has two cooling cell setpoints, which can be changed by the operator within the Oven
Control Program. An oven with two cooling zones has a set point for each. An oven with three cooling zones has a set
point for the first and second cooling zones (the first cooling zone being the one closest to the heated section of the
oven). An oven with four cooling zones has a set point for the first and third zones.
OPERATION & PROCESS:
Controlled Cooling provides the ability to stabilize the temperatures in the cooling zones of the oven. It provides
compensation for factors such as changes in ambient temperature and product loading. It also allows the cooling zones
to reach a stable temperature much sooner than is possible with uncontrolled cooling, and ties the cooling zone
temperatures to the process ready condition of the oven.
The temperature range which is attainable for Controlled Cooling zones is influenced by many factors, including, but not
limited to, the following: heated zone set-points, conveyor type, conveyor speed, product loading, nitrogen flow settings,
machine exhaust, controlled exhaust setting, etc.
Technical Service Manual 94 Revision Date: August 2004
CONTROLLED EXHAUST SYSTEM (AIR ONLY OR OVENS EQUIPPED WITH AIR SWITCHING)
CONTROLLED EXHAUST SYSTEM (CES) (Air Mode)
This exhaust subsystem extracts heated gas directly from the oven chamber between the last heating zone and the first
cooling zone, minimizing the amount of heat and flux entering the cooling section of the oven. The result is product
cooling improvement and maintenance reduction in the Air Mode. It generates a controllable, positive exhaust flow and
does not depend on the facility exhaust for its operation.
A small amount of compressed air flows through a Venturi (mounted inside the Controlled Exhaust Tube) and creates a
negative pressure at the CES slot in the oven chamber. This draws gas out of the Oven Chamber. The oven chamber
exhaust flow rate is controlled by the amount of air supplied to the oven.
The cooling effect of the incoming compressed air causes an accumulation of flux condensate in the exhaust nozzle.
The nozzle requires periodic cleaning
.
INDIVIDUAL CELL INLETS
The “makeup” gas to replace the exhaust flow is supplied by the gas intakes of the individual Zones (cells). Additional
“makeup” enters the oven chambers at the “onload” and “offload” openings.
CES system is not used with N2 to minimize nitrogen consumption.
Technical Service Manual 95 Revision Date: August 2004
INTEGRATED EXHAUST STACK FILTER
The Integrated Exhaust Stack Filter is:
! Standard, (installed on all ovens) ) An option, (NOT installed on all ovens)
PURPOSE:
To capture and dispose of the byproducts of SMT reflow by condensing and filtering the oven exhaust.
APPLICATION
The Integrated Exhaust Stack Filter option is a simple filtering method for capturing and disposing of many of the by-
products of the Surface Mount Reflow Process. The Integrated Exhaust Stack filter consists of two filters in metal
enclosure. The enclosure has an inlet and a connection point for a factory exhaust duct. There is an access door for
changing the disposable filters.
The introduction ambient room air powered by the facility exhaust accomplishes condensation. The hot gas exhaust
stream from the FFC system is routed to the intake tube of the filter enclosure where it is mixed with several streams of
ambient air. The cooling effect of the room air streams causes flux and other outgassed contaminants to condense in
the exhaust stream as it enters the box, but prior to passing through the filter. Contaminants are trapped in the filter, and
the cleaned gas continues out the exhaust duct.
BENEFITS
• Flux and other out-gassed contaminants are captured in an easily changed, disposable filter.
• Provides increased protection of the facility exhaust system from contaminants.
• Totally within the overall footprint of the Reflow Oven.
• Inexpensive locally available filter
MAINTENANCE:
Filter change interval is approximately every 2 weeks, but is throughput and paste dependent.
Filter change requires 1 minute or less
Filter Enclosure cleaning interval is approximately every two months, but is throughput and paste dependent.
Note: The contaminants caught by the filters are hazardous waste. Proper disposal techniques should be
followed. The filter contaminants are paste and product dependent. Refer to the paste specification for more
information.
Wear latex gloves, eye protection and breathing protection when changing filter.
Filters:
1 – 1x10x20 Polyester Smith 5003, part number #1248601
1 – 1x10x20 SEP Pleated Smith Special, part number #1248701