FXOS8700CQ datasheet(80/86 Pages) FREESCALE

80 / 86 page

Sensors

Freescale Semiconductor, Inc.

Mounting Guidelines for the Quad Flat No Lead (QFN) Package

Printed Circuit Board (PCB) layout is a critical portion of the total design. The footprint for the surface mount packages must be

the correct size to ensure proper solder connection interface between the PCB and the package. With the correct footprint, the

packages will self-align when subjected to a solder reflow process.

These guidelines are for soldering and mounting the Quad Flat No-Lead (QFN) package inertial sensors to PCBs. The purpose

is to minimize the stress on the package after board mounting. The FXOS8700CQ uses the QFN package platform. This section

describes suggested methods of soldering these devices to the PCB for consumer applications.

10.1

Overview of soldering considerations

Information provided here is based on experiments executed on QFN devices. They do not represent exact conditions present

at a customer site. Hence, information herein should be used for guidance only and process and design optimizations are

recommended to develop an application specific solution. It should be noted that with the proper PCB footprint and solder stencil

designs, the package will self-align during the solder reflow process.

10.2

Halogen content

This package is designed to be Halogen Free, exceeding most industry and customer standards. Halogen Free means that no

homogeneous material within the assembly package shall contain chlorine (Cl) in excess of 700 ppm or 0.07% weight/weight or

bromine (Br) in excess of 900 ppm or 0.09% weight/weight.

10.3

PCB mounting recommendations

The PCB land should be designed with Non-Solder Mask Defined (NSMD) as shown in Figure 138 and Figure 139

No additional via pattern underneath package.

PCB land pad is 0.8 mm by 0.3 mm as shown in Figure 138 and Figure 139.

Solder mask opening = PCB land pad edge + 0.113 mm larger all around.

Stencil opening = PCB land pad -0.015 mm smaller all around = 0.77 mm by 0.27 mm.

Stencil thickness is 100 or 125

μm.

Do not place any components or vias at a distance less than 2 mm from the package land area. This may cause

additional package stress if it is too close to the package land area.

Signal traces connected to pads are as symmetric as possible. Put dummy traces on NC pads in order to have same

length of exposed trace for all pads.

Use a standard pick and place process and equipment. Do not use a hand soldering process.

10. Do not use a screw down or stacking to fix the PCB into an enclosure because this could bend the PCB, putting stress

on the package.

11. The PCB should be rated for the multiple lead-free reflow condition with max 260°C temperature.

12. No copper traces on top layer of PCB under the package. This will cause planarity issues with board mount. Freescale

QFN sensors are compliant with Restrictions on Hazardous Substances (RoHS), having halide-free molding

compound (green) and lead-free terminations. These terminations are compatible with tin-lead (Sn-Pb) as well as tin-

silver-copper (Sn-Ag-Cu) solder paste soldering processes. Reflow profiles applicable to those processes can be used

successfully for soldering the devices.

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