Appendix: QFN and BGA Assembly Guideline
Because of their small size and finer pitches, solder paste deposition for QFN packages requires extra care. However,
a uniform and precise deposition can be achieved if miniature stencil specific to the component is used. The stencil
aperture should be aligned with the pads under 50 to 100x magnification.
The stencil should then be lowered onto the PCB and the paste should be deposited with a small metal squeegee
blade. Alternatively, the mini stencil can be used to print paste on the package side. A 125 microns thick stencil with
aperture size and shape same as the package land should be used.
In addition, no-clean flux should be used, because small standoff of QFN packages does not leave much room for
cleaning.
7.4.4 Component Placement
QFN packages are expected to have superior self-centering ability due to their small mass. The placement of QFN
packages should be similar to that of BGAs. As the leads are on the underside of the package, split-beam optical
system should be used to align the component on the motherboard. This will form an image of leads overlaid on the
mating footprint and aid in proper alignment. The alignment should also be done at 50 to 100x magnification. The
placement machine should have the capability of allowing fine adjustments in X, Y, and rotational axes.
7.4.5 Component Attachment
The reflow profile developed during original attachment or removal should be used to attach the new component.
Because all reflow profile parameters have already been optimized, using the same profile will eliminate the need for
thermocouple feedback and will reduce operator dependencies.
7.5 RoHS Compliant
GR551x is RoHS compliant, as per directive 2002/95/EC and its subsequent amendments.
7.6 SVHC Materials (REACH)
GR551x is compliant with Substance of Very High Concern (SVHC) list based on the publication by European Chemicals
Agency (ECHA) on October 28, 2008 Regulation (EC) No 1907/2006 concerning
Registration, Evaluation, Authorisation
and Restriction of Chemicals (REACH)
.
7.7 Halogen Free
GR551x is compliant with BS EN 14582: 2007 in regards to halogens: fluorine, chlorine, bromine, and iodine content.
Copyright © 2021 Shenzhen Goodix Technology Co., Ltd.
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