? freescale semiconductor, in c., 2009. all rights reserved. an3839 rev 1, 4/2009 freescale semiconductor application note MMA7660FC board mounting guidelines by: laura salhuana acronyms pcb: printed circuit board dfn: dual flat no-lead cl: chlorine br: bromine rohs: restrictions on hazardous substances sn: tin pb: lead ag: silver cu: copper abstract this application note discusses board mounting guidelines and co nsiderations for the MMA7660FC sensor. the first topic that will be discussed is the minimum recommended footprint for surfac e mount applications. this is a critical portion of design and if not done properly can affect soldering connection interface between the board and the package. next, will be soldering and mounting guidelines and considerations for the dfn acceleromete r sensor to a pcb. these suggested methods will minimize the stress on the package after board mount. following these guidelines and considerations for board mounting will result in better performance from the MMA7660FC sensor. figure 1. pin connections n/c dvdd dvss sda scl reserved n/c avdd avss int 1 2 3 4 5 6 7 8 9 10 MMA7660FC table 1. pin description pin # pin name description pin status 1 reserved connect to avss (pin 4) input 2 n/c no internal connection, leave unconnected or connect to ground input 3 avdd analog power input 4 avss analog ground input 5 int interrupt/data ready output 6scl i 2 c serial clock input 7sda i 2 c serial data open drain 8 dvss digital i/o ground input 9 dvdd digital i/o power input 10 n/c no internal connection, recommended to connect to ground input
an3839 sensors freescale semiconductor 2 figure 2. i 2 c connection to mcu minimum recommended f ootprint 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 proc ess. 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 dfn accelerometer sensor to a printed circuit board these guidelines are for soldering and mounting the dfn package in ertial sensors to pcbs. the purpose is to minimize the stress on the package after board mounting. the mma7660 digita l output accelerometer uses the dfn package platform. this section describes suggested methods of soldering th ese devices to the pcb for consumer applications. pages 5, 6, and 7 show the package outline drawing for the package. overview of soldering considerations information provided here is based on ex periments executed on dfn devices. they do not represent exact conditions present at a customer site. hence, information herein should be used as a guideline only and process and design optimizations are recommended to develop an application specific solution. it shoul d be noted that with the proper pcb footprint and solder stenc il designs the package will self-align during the solder reflow proc ess. the following are the recommended guidelines to follow fo r mounting dfn sensors for consumer applications. halogen content this package is designed to be halogen free, exceeding most indus try and customer standards. halogen free means that no homogeneous material within the assembly package shall contain cl in excess of 700 ppm or 0.07% weight/weight or br in excess of 900 ppm or 0.09% weight/weight. nc3 dvdd dvss sda scl reserve nc2 avdd avss int 1 2 3 56 7 8 9 10 4 gnd vdd vdd vdd gnd MMA7660FC sda scl int1 mcu r1 4.70 k r2 4.70 k note: a 10 f ceramic capacitor can be placed connecting pin 3 (avdd) to pin 4 (avss). in addition, another 10 f ceramic capacitor can be place connecting pin 9 (dvdd) to pin 8 (dvss). the capac itors should be placed close to the pins of the MMA7660FC and is recommended for testing and to adequately decouple the accelerometer from noise on the power supply. u13
an3839 sensors freescale semiconductor 3 pcb mounting recommendations 1. the pcb land should be designed with non solder mask defined (nsmd) as shown in figure 3 and figure 4 . 2. no additional via pattern underneath package. 3. pcb land pad is 0.825 mm x 0.3 mm as shown in figure 3 and figure 4 . 4. do not solder down smaller side tabs on either end of the package. 5. the solder mask opening is equal to the size of the pcb land pad plus 0.15 mm. 6. the stencil aperture size is equal to the pcb land pad ? minus 0.03 mm total. 7. stencil thickness should be 75 m. 8. 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. 9. signal traces connected to pads should be as symmetric as possible. put dummy tr aces on nc pads in order to have same length of exposed trace for all pads. signal traces with 0.15 mm width and minimum 0.5 mm length for all pcb land pads near the package are recommended as shown in figure 3 and figure 4 . wider trace can be cont inued after the 0.5 mm zone. 10. use a standard pick and place process and equi pment. do not use a hand soldering process. 11. it is recommended to use a no clean solder paste. 12. do not use a screw down or stacking to fix the pcb into an enclosure because this coul d bend the pcb putting stress on the package. 13. the pcb should be rated for the multiple lead- free reflow condition with max 260c temperature. 14. no copper traces on top layer of pcb under the pack age. this will cause planarit y issues with board mount. freescale dfn sensors are compliant with rohs, having halide free molding compound (green) and lead-free terminations. these terminations are compatible with tin-lead (sn-pb) as we ll as tin-silver-copper (sn-ag-cu) solder paste soldering processes. reflow profiles applicable to those proce sses can be used successfully for soldering the devices. figure 3. package footprint, pc b land pattern, and stencil design
an3839 sensors freescale semiconductor 4 figure 4. pcb land pattern detail
an3839 sensors freescale semiconductor 5 package dimensions
an3839 sensors freescale semiconductor 6 package dimensions
an3839 sensors freescale semiconductor 7 package dimensions
how to reach us: home page: www.freescale.com web support: http://www.freescale.com/support usa/europe or locations not listed: freescale semiconductor, inc. technical information center, el516 2100 east elliot road tempe, arizona 85284 1-800-521-6274 or +1-480-768-2130 www.freescale.com/support europe, middle east, and africa: freescale halbleiter deutschland gmbh technical information center schatzbogen 7 81829 muenchen, germany +44 1296 380 456 (english) +46 8 52200080 (english) +49 89 92103 559 (german) +33 1 69 35 48 48 (french) www.freescale.com/support japan: freescale semiconductor japan ltd. headquarters arco tower 15f 1-8-1, shimo-meguro, meguro-ku, tokyo 153-0064 japan 0120 191014 or +81 3 5437 9125 support.japan@freescale.com asia/pacific: freescale semiconductor china ltd. exchange building 23f no. 118 jianguo road chaoyang district beijing 100022 china +86 010 5879 8000 support.asia@freescale.com for literature requests only: freescale semiconductor lite rature distribution center p.o. box 5405 denver, colorado 80217 1-800-441-2447 or +1-303-675-2140 fax: +1-303-675-2150 ldcforfreescalesemiconductor@hibbertgroup.com information in this document is provided solely to enable system and software implementers to use freescale semiconduc tor products. there are no express or implied copyright licenses granted hereunder to design or fabricate any integrated circuits or integrated circuits based on the information in this document. freescale semiconductor reserves the right to make changes without further notice to any products herein. freescale semiconductor makes no warranty, representation or guarantee regarding the suitability of its products for any particular purpose, nor does freescale semiconductor assume any liability ar ising out of the application or use of any product or circuit, and specifically discl aims any and all liability, including without limitation consequential or incidental damages. ?typical? parameters that may be provided in freescale semiconductor data s heets and/or specifications can and do vary in different applications and actual performance may vary over time. all operating parameters, including ?typicals?, must be validated for each customer application by customer?s technical experts. freescale se miconductor does not convey any license under its patent rights nor the rights of others. freescale semiconductor products are not designed, intended, or authorized for use as components in systems intended for surgical implant into the body, or other applications intended to support or sustain life, or for any other application in which the fa ilure of the freescale semiconductor product could create a situation where personal injury or death may occur. should buyer purchase or use freescale semiconductor products for any such unintended or unauthorized application, buyer shall indemni fy and hold freescale semiconductor and its officers, employees, subsidiaries, affili ates, and distributors harmless against all claims, costs, damages, and expenses, and reasonable attorney fees arising out of, directly or indirectly, any claim of personal injury or death associated with such unintended or unauthorized use, even if such claim alleges that freescale semiconductor was negligent regarding the design or manufacture of the part. freescale? and the freescale logo are trademarks of freescale semiconductor, inc. all other product or service names are the property of their respective owners. ? freescale semiconductor, inc. 2009. all rights reserved. an3839 rev. 1 4/2009
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