AN1902 Freescale Semiconductor / Motorola, AN1902 Datasheet - Page 20

• Manufacturer Part Number: AN1902
• Description: Quad Flat Pack No-Lead (QFN)
• Manufacturer: Freescale Semiconductor / Motorola

AN1902/D
20
5.3.1 Package Removal
In general, a rework station should have a split light system, an XY table for alignment
and a hot air reflow system with top and bottom heaters for component removal.
To remove the faulty component from the board, hot air is applied from the top and
bottom heaters. An air nozzle of the correct size should be used to conduct the hot air
to the QFN component such that the vacuum pick up tool can properly remove the
component. The temperature for the top heater should be set at 300°C for 30 seconds
and the bottom heater applied simultaneously at 150°C for 30 seconds. The pictorial
procedure is shown in
knowledge on rework and their experts should be consulted for further guidance.
5.3.2 Site Preparation
Once the QFN component is removed, the site is cleaned and dressed to prepare for
the new component placement. A de-soldering station can be used for solder dress-
ing. It should be noted that the applied temperature should not be >245°C. Otherwise
the copper pad on the PCB may peel off.
5.3.3 Solder Paste Printing
A mini-stencil (See
pattern as the normal stencil are placed at the component site. A mini-metal squeegee
blade deposits solder paste in the specific area. The printed pad should be inspected
to ensure even and sufficient solder paste before component placement.
Load PCB on XY Table
Freescale Semiconductor, Inc.
For More Information On This Product,
Quad Flat Pack No-Lead (QFN)
Go to: www.freescale.com
Figure 25 Mini-Stencil for Solder Paste Printing
Figure
Figure
Figure 24 Package Removal Process
25) with the same stencil thickness, aperture opening and
24. Many assembly sites have extensive in-house
Select Appropriate Nozzle
Removal
MOTOROLA