dm00070854

AN4211
Application note
Guidelines for soldering MEMS microphones
By Alessandro Morcelli
Introduction
This application note provides guidelines and recommendations for soldering MEMS microphones on
application boards. Microphones, as pressure sensors, sense the mechanical stress coming from the
PCB, hence this force should be kept to a minimum. Printing and stencil parameters, followed by device
footprints/recommended land patterns, stencil openings, and process considerations are presented in
this document.
The following guidelines have been developed for the MEMS microphone family (MP45DT02/-M,
MP34DB01, MP34DT01/-M, MP33AB01/H, MP34DB02, and MP23AB02B) offered by
STMicroelectronics.
Demonstration boards (STEVAL-MKI129Vx) for the evaluation and promotion of the MP45DT02,
MP34DT01, and MP34DT01 are also available. Please refer to AN4184 "Microphone coupon boards
STEVAL-MKI129Vx based on the MP45DT02, MP34DB01, and MP34DT01" on www.st.com for further
information.
Figure 1: Mechanical specifications for soldering
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www.st.com
Contents
AN4211
Contents
1
Printing and stencil parameters ..................................................... 3
2
Device footprint, land pattern and stencil openings ..................... 4
2.1
MP45DT02 and MP45DT02-M dimensions ....................................... 4
2.2
MP34DB01 dimensions ..................................................................... 5
2.4
MP34DT01 and MP34DT01-M dimensions ....................................... 6
2.5
MP33AB01 and MP33AB01H dimensions ........................................ 7
2.6
MP34DB02 dimensions ..................................................................... 8
2.8
MP23AB02B dimension .................................................................... 9
3
Process considerations ................................................................ 10
4
Revision history ............................................................................ 11
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Printing and stencil parameters
Printing and stencil parameters
The soldering paste thickness and pattern are important for the proper microphone
soldering process. Some recommendations to be followed are listed below:







Stainless steel stencils are recommended
Stencil thickness of 75 - 100 µm (2.95 - 3.94 mils) is recommended for screen printing
The final soldering paste thickness should allow proper cleaning of flux residuals and
clearance between the sensor package and PCB
Stencil aperture should have a rectangular shape
The openings of the stencil for the signal pads should be between 70 - 90% of the
PCB pad
Optionally, for better solder paste release, the aperture walls should be trapezoidal
and the corners rounded
The fine IC leads pitch requires accurate alignment of the stencil to the PCB. The
stencil and printed circuit assembly should be aligned to within 25 µm (1 mil) prior to
application of the solder paste
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Device footprint, land pattern and stencil
openings
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2
Device footprint, land pattern and stencil openings
2.1
MP45DT02 and MP45DT02-M dimensions
Figure 2: MP45DT02 - device footprint and PCB land pattern
Figure 3: MP45DT02 - recommended stencil openings
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2.2
Device footprint, land pattern and stencil
openings
MP34DB01 dimensions
Figure 4: MP34DB01 - device footprint and PCB land pattern
Figure 5: MP34DB01 - recommended stencil openings
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Device footprint, land pattern and stencil
openings
2.4
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MP34DT01 and MP34DT01-M dimensions
Figure 6: MP34DT01 - device footprint and PCB land pattern
Figure 7: MP34DT01 - recommended stencil openings
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2.5
Device footprint, land pattern and stencil
openings
MP33AB01 and MP33AB01H dimensions
Figure 8: MP33AB01 and MP33AB01H - device footprint and PCB land pattern
Figure 9: MP33AB01 and MP33AB01H - recommended stencil openings
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Device footprint, land pattern and stencil
openings
2.6
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MP34DB02 dimensions
Figure 10: MP34DB02 - device footprint
Figure 11: MP34DB02 - recommended stencil openings
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2.8
Device footprint, land pattern and stencil
openings
MP23AB02B dimension
Figure 12: MP23AB02B - device footprint
Figure 13: MP23AB02B recommended stencil openings
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Process considerations
3
AN4211
Process considerations
If self-cleaning solder paste is not used, proper cleaning of the board after soldering must
be done to remove any possible source of leakage between pads due to flux residues. For
the soldering profile, refer to the table and figure below.
Table 1: Soldering profile
Description
Parameter
Average ramp rate
Pb free
TL to TP
3 °C/sec max
Minimum temperature
TSMIN
150 °C
Maximum temperature
TSMAX
200 °C
Time (TSMIN to TSMAX)
tS
60 sec to 120 sec
Ramp-up rate
TSMAX to TL
3 °C/sec max
Time maintained above liquidus
temperature
tL
60 sec to 150 sec
Liquidus temperature
TL
217 °C
Peak temperature
TP
260 °C max
Preheat
Time within 5 °C of actual peak
temperature
20 sec to 40 sec
Ramp-down rate
6 °C/sec max
Time 25 °C (t25 °C) to peak temperature
8 minutes max
Figure 14: Soldering profile
No solder material reflow on the side of the package is allowed since LGA packages have
metal traces on the sides of the package.
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Revision history
Revision history
Table 2: Document revision history
Date
Revision
Changes
12-Mar-2013
1
Initial release.
21-Jul-2014
2
Added Section 2.5: "MP34DB02 dimensions" and Section 2.6:
"MP23AB02B dimension".
08-Aug-2014
3
Modified Figure 9: "MP33AB01 and MP33AB01H - recommended
stencil openings".
15-Jun-2015
4
Updated Section "Introduction"
Updated Section 2: "Device footprint, land pattern and stencil
openings"
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IMPORTANT NOTICE – PLEASE READ CAREFULLY
STMicroelectronics NV and its subsidiaries (“ST”) reserve the right to make changes, corrections, enhancements, modifications,
and improvements to ST products and/or to this document at any time without notice. Purchasers should obtain the latest relevant
information on ST products before placing orders. ST products are sold pursuant to ST’s terms and conditions of sale in place at
the time of order acknowledgement.
Purchasers are solely responsible for the choice, selection, and use of ST products and ST assumes no liability for application
assistance or the design of Purchasers’ products.
No license, express or implied, to any intellectual property right is granted by ST herein.
Resale of ST products with provisions different from the information set forth herein shall void any warranty granted by ST for such
product.
ST and the ST logo are trademarks of ST. All other product or service names are the property of their respective owners.
Information in this document supersedes and replaces information previously supplied in any prior versions of this document.
© 2015 STMicroelectronics – All rights reserved
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