SLUA271C June   2002  – December 2023 ADS1013 , ADS1014 , ADS1015 , ADS1018 , ADS1112 , ADS1113 , ADS1114 , ADS1115 , ADS1118 , ADS1120 , ADS1148 , ADS114S06 , ADS114S06B , ADS114S08 , ADS114S08B , ADS1158 , ADS1191 , ADS1192 , ADS1203 , ADS1204 , ADS1205 , ADS1220 , ADS1225 , ADS1226 , ADS124S06 , ADS124S08 , ADS1257 , ADS1258 , ADS1261 , ADS1283 , ADS1287 , ADS1287D , ADS1291 , ADS1292 , ADS1292R , ADS1293 , ADS6222 , ADS6224 , ADS6242 , ADS6243 , ADS6244 , ADS6245 , ADS6422 , ADS6423 , ADS6424 , ADS6425 , ADS6442 , ADS6443 , ADS6444 , BQ24010 , BQ24012 , BQ24013 , BQ24020 , BQ24022 , BQ24023 , CC2560 , CC2564C , CSD13202Q2 , CSD15571Q2 , CSD16301Q2 , CSD16321Q5 , CSD16322Q5 , CSD16323Q3 , CSD16325Q5 , CSD16327Q3 , CSD16340Q3 , CSD16342Q5A , CSD16401Q5 , CSD16403Q5A , CSD16404Q5A , CSD16406Q3 , CSD16407Q5 , CSD16408Q5 , CSD16409Q3 , CSD16410Q5A , CSD16411Q3 , CSD16412Q5A , CSD16413Q5A , CSD16414Q5 , CSD16415Q5 , CSD16556Q5B , CSD16570Q5B , CSD17301Q5A , CSD17302Q5A , CSD17303Q5 , CSD17304Q3 , CSD17305Q5A , CSD17306Q5A , CSD17307Q5A , CSD17308Q3 , CSD17309Q3 , CSD17310Q5A , CSD17311Q5 , CSD17312Q5 , CSD17313Q2 , CSD17318Q2 , CSD17322Q5A , CSD17327Q5A , CSD17501Q5A , CSD17505Q5A , CSD17506Q5A , CSD17507Q5A , CSD17510Q5A , CSD17522Q5A , CSD17527Q5A , CSD17551Q3A , CSD17551Q5A , CSD17552Q3A , CSD17552Q5A , CSD17553Q5A , CSD17555Q5A , CSD17556Q5B , CSD17559Q5 , CSD17570Q5B , CSD17571Q2 , CSD17573Q5B , CSD17575Q3 , CSD17576Q5B , CSD17577Q3A , CSD17577Q5A , CSD17578Q3A , CSD17578Q5A , CSD17579Q3A , CSD17579Q5A , CSD17581Q3A , CSD17581Q5A , CSD18501Q5A , CSD18502Q5B , CSD18503Q5A , CSD18504Q5A , CSD18509Q5B , CSD18510Q5B , CSD18511Q5A , CSD18512Q5B , CSD18513Q5A , CSD18514Q5A , CSD18531Q5A , CSD18532NQ5B , CSD18532Q5B , CSD18533Q5A , CSD18534Q5A , CSD18537NQ5A , CSD18540Q5B , CSD18543Q3A , CSD18563Q5A , CSD19502Q5B , CSD19531Q5A , CSD19532Q5B , CSD19533Q5A , CSD19534Q5A , CSD19537Q3 , CSD19538Q2 , CSD19538Q3A , CSD25310Q2 , CSD25402Q3A , CSD25404Q3 , CSD85301Q2 , CSD85312Q3E , CSD86330Q3D , CSD86336Q3D , CSD86350Q5D , CSD86356Q5D , CSD86360Q5D , CSD87312Q3E , CSD87313DMS , CSD87330Q3D , CSD87331Q3D , CSD87333Q3D , CSD87334Q3D , CSD87335Q3D , CSD87350Q5D , CSD87351Q5D , CSD87351ZQ5D , CSD87352Q5D , CSD87353Q5D , CSD87355Q5D , CSD87502Q2 , CSD87503Q3E , CSD88584Q5DC , CSD88599Q5DC , DAC3482 , DAC3484 , LMR10510 , LMR10515 , LMR10520 , LMR10530 , MSC1202Y2 , MSC1202Y3 , MSP430F1122 , MSP430F1132 , MSP430F122 , MSP430F1222 , MSP430F123 , MSP430F1232 , MSP430F2001 , MSP430F2002 , MSP430F2003 , MSP430F2011 , MSP430F2012 , MSP430F2013 , MSP430F2013-EP , MSP430F2112 , MSP430F2122 , MSP430F2132 , MSP430FR5969 , MSP430G2001 , MSP430G2101 , MSP430G2102 , MSP430G2111 , MSP430G2112 , MSP430G2121 , MSP430G2131 , MSP430G2132 , MSP430G2152 , MSP430G2201 , MSP430G2201-Q1 , MSP430G2211 , MSP430G2212 , MSP430G2221 , MSP430G2231 , MSP430G2231-Q1 , MSP430G2232 , MSP430G2252 , MSP430G2302 , MSP430G2312 , MSP430G2332 , MSP430G2352 , MSP430G2402 , MSP430G2432 , MSP430G2452 , TLA2021 , TLA2022 , TLA2024 , TLV62065 , TLV62080 , TLV62085 , TLV62090 , TLV62130 , TLV62130A , TLV62150 , TLV62150A , TPS60150 , TPS60151 , TPS61020 , TPS61021A , TPS61024 , TPS61025 , TPS61026 , TPS61027 , TPS61028 , TPS61029 , TPS61029-Q1 , TPS61030 , TPS61031 , TPS61032 , TPS61042 , TPS61045 , TPS61086 , TPS61087 , TPS61087-Q1 , TPS61088 , TPS61089 , TPS61090 , TPS61091 , TPS61092 , TPS61093 , TPS61093-Q1 , TPS61100 , TPS61107 , TPS61120 , TPS61130 , TPS61170 , TPS61170-Q1 , TPS61200 , TPS61201 , TPS61202 , TPS61240 , TPS61240-Q1 , TPS61251 , TPS61252 , TPS61260 , TPS61261 , TPS61291 , TPS62020 , TPS62021 , TPS62026 , TPS62040 , TPS62042 , TPS62043 , TPS62044 , TPS62046 , TPS62060 , TPS62061 , TPS62063 , TPS62065 , TPS62067 , TPS62080 , TPS62080A , TPS62081 , TPS62082 , TPS62085 , TPS62086 , TPS62087 , TPS62090 , TPS62090-Q1 , TPS62091 , TPS62092 , TPS62093 , TPS62095 , TPS62097 , TPS62097-Q1 , TPS62110 , TPS62110-EP , TPS62110-Q1 , TPS62111 , TPS62111-EP , TPS62112 , TPS62112-EP , TPS62113 , TPS62122 , TPS62125 , TPS62130 , TPS62130A , TPS62131 , TPS62132 , TPS62133 , TPS62134A , TPS62134B , TPS62134C , TPS62134D , TPS62135 , TPS62136 , TPS62140 , TPS62141 , TPS62142 , TPS62143 , TPS62150 , TPS62150A , TPS62151 , TPS62152 , TPS62153 , TPS62160 , TPS62161 , TPS62162 , TPS62163 , TPS62170 , TPS62171 , TPS62172 , TPS62173 , TPS62175 , TPS62177 , TPS62230 , TPS62231-Q1 , TPS622314-Q1 , TPS62240 , TPS62242 , TPS62243 , TPS62250 , TPS62260 , TPS62260-Q1 , TPS62261 , TPS62261-Q1 , TPS62262 , TPS62262-Q1 , TPS62263 , TPS62263-Q1 , TPS62270 , TPS62272 , TPS62273 , TPS62290 , TPS62290-Q1 , TPS62291 , TPS62293 , TPS62293-Q1 , TPS62300 , TPS62301 , TPS62302 , TPS62303 , TPS62304 , TPS62305 , TPS62320 , TPS62321 , TPS62352 , TPS62355 , TPS62400 , TPS62400-Q1 , TPS62401 , TPS62402 , TPS62403 , TPS62404 , TPS62404-Q1 , TPS62406-Q1 , TPS62407-Q1 , TPS62410 , TPS62410-Q1 , TPS62420 , TPS62420-Q1 , TPS62421 , TPS62422-Q1 , TPS62423-Q1 , TPS62424-Q1 , TPS62510 , TPS62560 , TPS62562 , TPS62590 , TPS62590-Q1 , TPS62730 , TPS62732 , TPS62733 , TPS62740 , TPS62750 , TPS62751 , TPS62821 , TPS62822 , TPS62823 , TPS62825 , TPS62826 , TPS62840 , TPS62870 , TPS62870-Q1 , TPS62871 , TPS62871-Q1 , TPS62872 , TPS62872-Q1 , TPS62873 , TPS62873-Q1 , TPS62874-Q1 , TPS62875-Q1 , TPS62876-Q1 , TPS62877-Q1 , TPS63000 , TPS63000-Q1 , TPS63001 , TPS63002 , TPS63020 , TPS63021 , TPS63030 , TPS63031 , TPS63050 , TPS63051 , TPS63060 , TPS63061 , TPS63070 , TPS63700 , TPS63710 , TPS84620 , TPSM82810 , TPSM82813 , TPSM82816 , TPSM82821 , TPSM82822 , TPSM82864A , TPSM82866A , TPSM82866C , TPSM8287A06 , TPSM8287A10 , TPSM8287A12 , TPSM8287A15 , TUSB7320 , TUSB7340 , TUSB8040A , TUSB8040A1

 

  1.   1
  2.   QFN and SON PCB Attachment
  3.   Trademarks
  4. 1Texas Instruments Quad Flatpack No Leads and Small-Outline No Leads
    1. 1.1 Introduction
  5. 2Manufacturing Considerations
    1. 2.1 SMT Process
  6. 3Printed Circuit Board (PCB) Design Guidelines
    1. 3.1 Land Pad Styles
    2. 3.2 Land Pad Design
    3. 3.3 Lead Finger Pad PCB Design
    4. 3.4 Exposed Pad PCB Design
      1. 3.4.1 Thermal Pad Via Design
    5. 3.5 Solder Mask
    6. 3.6 Surface Finishes
    7. 3.7 Board Layout Considerations
  7. 4Solder Paste Screen Printing Process
    1. 4.1 Solder Paste
    2. 4.2 Solder Stencils
    3. 4.3 Lead Finger Stencil Design
    4. 4.4 Exposed-Pad Stencil Design
  8. 5Package to Board Assembly Process
    1. 5.1 Placement and Alignment
    2. 5.2 Solder Reflow
    3. 5.3 PCB Cleaning
    4. 5.4 Inspection
  9. 6Rework Guidelines (Hot Gas Convection and Manual)
    1. 6.1 Compound Removal
    2. 6.2 Site Redress
    3. 6.3 Component Replacement and Reflow
    4. 6.4 Manual Rework Considerations
  10. 7Revision History

4.4 Exposed-Pad Stencil Design

The QFN and SON package is thermally and electrically efficient due to the exposed die attach pad on the under side of the package. The exposed die must be soldered to the PCB or motherboard substrate.

It is good practice to minimize the presence of voids within the exposed pad interconnection. Total elimination is difficult, but the design of the exposed pad stencil is crucial. The proposed stencil design enables out-gassing of the solder paste during reflow and also regulates the finished solder thickness. Typically, the solder-paste coverage is approximately 50% to 70% of the pad area (see Figure 4-3). Designing an aperture that prints solder 1:1 with the exposed pad results in excessive metal volume that can "float" the part and cause opens and other manufacturing defects. In addition, the amount of voiding post reflow in the thermal pad solder joint should not exceed 50% in high-power applications (to be verified using an x-ray). Based on a JEDEC High K board stackup, 25% has been determined to be a point of diminishing thermal performance returns, but TI prefers a limit of 50% to be set (reference JESD51-7).

GUID-FDB36A8E-D114-477C-B10C-4170147C014F-low.gifFigure 4-3 Example Land Pattern and Exposed-Pad Stencil Design