8.3.2 Component Removal, Surface Mount J Lead Components, Hot Gas Method

Preparation
This method uses hot air nozzles that do not touch the component. Gas or air is heated and forced through a specially designed nozzle and directed onto the component leads and surface pads.

Hot gas/air nozzles come in several sizes to accommodate many of the different styles and sizes of components. Measure the overall length and width of the component to select the proper size tip. Check the nozzle for proper fit prior to processing the part. Some hot gas/air nozzle designs will heat only the component leads and pad area. (See Figure 1, Left Side) Some hot air nozzle designs heat the entire component, the leads and pad area. (See Figure 1, Right Side)

Hot gas/air can be used to remove a number of different styles of SMT components but the heated gas/air must be directed onto the leads and pads and away from the top of the component and circuit board surface.

Hot gas/air nozzles may or may not include vacuum assistance to lift the component off the circuit board surface.

Procedure

1. Place the pre-heated circuit board on the positioning table. A heated positioning table is available to pre-heat the circuit board, or can be used to maintain the pre-heated temperature when many components need to be removed from one circuit board.
2. Apply a small amount of liquid flux to all leads of the component.
3. Place the nozzle directly over the top of the component and activate the air flow. When the solder has melted actuate the vacuum assist or lift off the component with a vacuum pen. Lift the component straight up. (See Figure 2)
   
   It's difficult to know precisely how long to dwell prior to safely removing the part. This is further complicated by the fact that when removing a bank of components, parts subsequent to the first come off much faster. Obviously, the smaller the part the quicker it reflows. Small SMT components may reflow in a few seconds and large SMT components may take more than a minute.
4. Clean the area.