AN1902 Freescale Semiconductor / Motorola, AN1902 Datasheet - Page 19

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

MOTOROLA
5.2.4.3 Micro-Sectioning
Micro-sectioning is another method of inspecting solder joints. This method is not
ideal for production inspection, but a tool to inspect the condition of the solder fillet.
Figure 23
5.2.4.4 Conventional Visual Inspection
The MAP style QFN is difficult to inspect from the top of the package compared to the
punch singulated style. It may be necessary to tilt the PCB to inspect solder joints for
the MAP style QFNs.
5.3 Rework Procedure
QFN components removed during PCB rework should not be reused for final assem-
blies. Motorola [2] follows standard component level qualifications for packages/com-
ponents and these include three solder reflows’ survivability. A package that has been
attached to a PCB and then removed has seen two solder reflows and if the PCB is
double sided the package has seen three solder reflows. Thus the package is at or
near the end of the tested and qualified range of known survivability. These removed
QFN components should be properly disposed of so that they will not mix in with fresh
equivalent QFN components.
Leadframe
PCB Copper
Freescale Semiconductor, Inc.
For More Information On This Product,
Pad
Solder
MAP QFN “S” Style
shows pictures of solder joints from different styles of QFN packages.
Quad Flat Pack No-Lead (QFN)
Figure 23 Micro-Sectioning of Various Styles of QFN
Go to: www.freescale.com
MAP QFN “E” Style
Punch Singulated QFN Style
Compound
Thermal
Exposed Pad
Thermal
Molding
Solder
Pad
AN1902/D
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