Technical_reference - 第54页
Technical Service Manual 54 Revision Dat e: August 2004 MESH BEL T CO NVEYOR SY STEM The m esh belt c onvey or system is used to proc ess single s ided surfac e m ount printed circuit boar ds. Mesh Belt Conveyor COM BINA…
Technical Service Manual 53 Revision Date: August 2004
C - CONVEYOR
CONVEYOR TYPES
This Section describes the three types of conveyor transport systems available on the Vitronics-Soltec Reflow Ovens.
They are:
1) Edge Rail Conveyor System,
2) Mesh Belt Conveyor System,
3) Combination Conveyor System.
The Mesh Belt conveyor system is standard on most Vitronics-Soltec Reflow Ovens. By special order, Ovens may have
only the Edge/Rail or Combination Edge Rail / Belt Conveyor System’
The description of all three follow:
EDGE / RAIL CONVEYOR SYSTEM
The edge / rail conveyor system (shown below) permits single or double sided surface mount printed circuit boards to be
processed through the oven. The standard chain conveyor carries circuit boards on 0.185 inch (4.75mm) long pins
extending from the chains. This conveyor system provides a convenient interface to other equipment in the production
line. Some Ovens have two sets of rails and chains (Dual Rail) for the processing of two PCBs at the same time.
ADJUSTMENT LEAD SCREWS
PROCESS TUNNEL
Edge Conveyor Rails
Edge / rail conveyor system.
Technical Service Manual 54 Revision Date: August 2004
MESH BELT CONVEYOR SYSTEM
The mesh belt conveyor system is used to process single sided surface mount printed circuit boards.
Mesh Belt Conveyor
COMBINATION CONVEYOR SYSTEM
The combination belt/rail conveyor has both the edge rail and the mesh belt. The mesh belt is below the edge rail
conveyors, and both conveyors are driven together. The belt conveyor is shorter than the outside edge of the machine
with the sheet metal covers on, and shorter than the end of the rails with chain guards installed.
A
pproximately 3 inches between end of
belt and end of rail conveyor (both
ends).
Technical Service Manual 55 Revision Date: August 2004
PRINTED CIRCUIT BOARD DESIGN CONSIDERATIONS
Printed circuit board (PCB) design is an important factor in the selection of the oven conveyor system. The mesh
belt conveyor system limits PCB processing to single sided PCBs without projecting leads or traces on the bottom of the
PCB. The edge/rail conveyor system allows double-sided PCBs to be processed with few restrictions. Major factors to
be considered in processing PCBs on the edge/rail conveyor system are described below.
PCBs processed on the edge/rail conveyor system are supported by pins projecting from the chains on each side of the
PCB. These pins can act as heat sinks drawing heat away from the PCB. This heat sink effect can result in uneven
heating of the PCB if the artwork (circuit traces, contact pads, etc.) contacts the pins supporting the PCB. To avoid
uneven heating problems, allow at least 0.20 inches (5mm) of clearance from the artwork to the edge of the PCB resting
on the pins.
The rail can be adjusted for different PCB widths. However, there are limits to the rail width adjustment. Minimum PCB
width is 2.0 inches (50.8 mm) and the maximum is 18 inches (450mm). For wide tunnel conveyors the maximum width is
22 inches.
The edge/rail conveyor is positioned at the factory to allow the minimum (2.0 inches) and maximum (18 inches) PCB
widths to be processed without moving the fixed rail.
Moving the fixed rail is not recommended unless it is necessary to accommodate other equipment in the production line.
PCB
Extended Pins
Chain Links
Rail Width Measurement Illustration