MMA7455LR2 datasheet(22/27 Pages) FREESCALE

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Sensors

Freescale Semiconductor

MMA7455L

MINIMUM RECOMMENDED FOOTPRINT FOR SURFACE MOUNTED APPLICATIONS

Surface mount board 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 board and the package.

With the correct footprint, the packages will self-align when

subjected to a solder reflow process. It is always

recommended to design boards with a solder mask layer to

avoid bridging and shorting between solder pads.

SOLDERING AND MOUNTING GUIDELINES FOR THE LGA ACCELEROMETER SENSOR TO A PC BOARD

These guideline are for soldering and mounting the LGA

package inertial sensors to printed circuit boards (PCBs). The

purpose is to minimize the stress on the package after board

mounting. Both the MMA73x0L 3 axis analog output family of

accelerometers and the MMA7455L digital output

accelerometer use the Land Grid Array (LGA) package

platform. This section describes suggested methods of

soldering these devices to the PC board for consumer

applications. Figure 19 shows the recommended PCB land

pattern for the package.

Figure 19. Recommended PCB Land Pattern for the

5 x 3 mm LGA Package

OVERVIEW OF SOLDERING CONSIDERATIONS

Information provided here is based on experiments

executed on LGA devices. They do not represent exact

conditions present at a customer site. Hence, information

herein should be used as a 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.

The following are the recommended guidelines to follow

for mounting LGA sensors for consumer applications.

PCB MOUNTING RECOMMENDATIONS

1. The PCB land should be designed with Non Solder

Mask Defined (NSMD) as shown in Figure 22.

2. No additional metal pattern underneath package as

shown in Figure 21.

3. PCB land pad is 0.9mm x 0.6mm which is the size of

the package pad plus 0.1mm as shown in Figure 22.

4. The solder mask opening is equal to the size of the

PCB land pad plus an extra 0.1mm as shown in

Figure 22.

5. The stencil aperture size is equal to the PCB land pad

– 0.025mm. Also note that for the 4 corner pads the

aperture size must be larger for solder balancing as

shown in Figure 23 and Figure 24. A 6mil thick stencil

is recommended.

6x2

12x1

14x0.9

14x0.6

10x0.8

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