Air-Vac PCBRM15, Руководство пользователя

Страница: 51 / 120

PCBRM15 & PCBRM System 5.2 User’s Manual Chapter 4: Processes & Applications
Part No. 4005.00.906
4-9
4.5 PCB Hole Cleaning Procedure
The hole cleaning operation starts immediately at the end of the component removal procedure. Referring
back to the component removal cycle, there will be an audible signal that indicates solder has stopped
flowing against the PCB. At this point, lower the air cleaning hood. It is important that sufficient downward
pressure be applied to insure a good seal between the hood and board surface. However, excessive
pressure can force the board to contact the flow well stand offs.
Low pressure air comes on automatically 1½ seconds after the solder stops flowing, forcing the molten
solder to drop from the holes into the empty flow well. The 1½ seconds delay prevents pressurized air
from coming in contact with the flowing solder.
The bottom of the PCB may have bridging or icicling caused by the moving air. The next operation of
resoldering of the replacement component will eliminate these conditions.
4.6 Soldering Replacement Component
After the holes have been cleaned, flux the leads of the replacement component, insert into PCB, and
start the cycle to solder the component. Where leads are “free”, exert a slight downward force on the
component to prevent “floating” of the component when the solder wave contacts the leads.
4.7 Specific Production Soldering Applications
In addition to component removal and replacement, the PCBRM15 is commonly used for Selective
Soldering in the production process.
Small Sub-Assemblies
The PCBRM12 has many advantages compared to hand soldering sub-assemblies. The average solder
cycle is 5-10 seconds regardless of the number of component leads. The heat exposure on the PCB is
less, since the average solder temperature is 500
°
F, compared to soldering irons that are higher.
Operator skill is minimal, since the solder cycle is controlled and the entire area is soldered at once.
Seating Soldered Components
In production wave soldering, a common problem is the “floating” of components that do not have clinched
leads resulting in components that are not properly seated. These components can be positioned over
the flow well and as the solder is flowing and all joints are molten, downward force may be used to
properly seat the component.
Selective Soldering
For a variety of reasons, many components cannot be on the board during the production wave or drag
soldering and cleaning operation. These components have to be soldered on the board individually in a
secondary operation. Rather than hand soldering these components, they can be positioned over the
flow well and wave soldered without reflowing components already on the board. Very common selective
soldering applications are for edge connectors that cannot be on the board due to pallet restrictions and
components like switches and relays that cannot go through the cleaning process.