MMA8652FC datasheet(69/77 Pages) FREESCALE

69 / 77 page

MMA8652FC

Sensors

Freescale Semiconductor, Inc.

Mounting Guidelines

Surface mount 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 Dual Flat No-Lead (DFN) package inertial sensors to PCBs. The purpose is to minimize the stress on the package

after board mounting. The MMA865xFC digital output accelerometers use the DFN package platform. This section describes

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

7.1

Overview of soldering considerations

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

at a customer site. Therefore, this information should be used as 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.

7.2

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.

7.3

PCB mounting/soldering recommendations

The PCB land should be designed as Non Solder Mask Defined (NSMD) as shown in Figure 62.

No additional via pattern underneath package.

PCB land pad is 0.6 mm x 0.225 mm as shown in Figure 62.

Solder mask opening = PCB land pad edge + 0.125 mm larger all around = 0.725 mm x 1.950 mm

Stencil opening = PCB land pad -0.05 mm smaller all around = 0.55 mm x 0.175 mm.

Stencil thickness is 100 or 125 um.

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, 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. Use caution when putting an assembled PCB into an enclosure, noting where the screw-down holes are and if any

press-fitting is involved. It is important that the assembled PCB remain flat after assembly, to ensure optimal electronic

operation of the device.

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

DFN 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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