PCBRM_User_Manual_R9.pdf - 第52页

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.

PCBRM15 & PCBRM System 5.2 User’s Manual

Chapter 4: Processes & Applications

Part No. 4005.00.906 4-10

4.8 Temperature Controller (Watlow)

Programmable Set Points. The Programmable Digital Readout Temperature Controller has two set

points that are programmable. “Set point one (SP1)” is the process temperature; “set point two (SP2)” is

the standby/interlock temperature.

Process Temperature (SP1). The process temperature determines the temperature of the flowing solder

during the rework and soldering cycles. The controller is connected to a thermocouple located at the

bottom of the solder pot. The actual temperature contacting the bottom of the printed circuit board is

approximately 10°F less than the process temperature, which is factory set at 500°F.

Standby/Interlock Temperature (SP2). The standby/interlock temperatures are the same

temperature. The standby temperature minimizes oxidation by automatically reducing the temperature

when the module is not being used. The purpose of the interlock temperature is to prevent the pump

motor from operating until the solder reaches a molten condition. SP2 is factory set at 70°F less than the

process temperature (500°F - 70°F = 430°F).

1. Actual Temperature (110)

2. Process Temperature (500)

3. Standby/Interlock Temperature

(-70)

4. Overtemp Temperature (617)

PCBRM15 & PCBRM System 5.2 User’s Manual

Chapter 4: Processes & Applications

Part No. 4005.00.906 4-11

4.9 Temperature Controller (CAL 9900)

Programmable Set Points. The Programmable Digital Readout Temperature Controller has two set

points that are programmable. Set point one (SP1) is the process temperature; set point two (SP2) is the

standby/interlock temperature. The temperature selector switch determines which set point is activated.