SPRAA99C March   2008  – May 2021 AM3351 , AM3352 , AM3354 , AM3356 , AM3357 , AM3358 , AM3359 , AM4372 , AM4376 , AM4377 , AM4378 , AM4379 , OMAPL138B-EP , TMUX646

 

  1.   Trademarks
  2. 1Introduction
  3. 2PCB Design Considerations
    1. 2.1 Solder Land Areas
    2. 2.2 Conductor Width/Spacing
    3. 2.3 High-Density Routing Techniques
    4. 2.4 Via Density
    5. 2.5 Conventional PCB Design
    6. 2.6 Advanced Design Methods
  4. 3Reliability
    1. 3.1 Reliability Calculations
    2. 3.2 Package Characteristics
    3. 3.3 Thermal Modeling
  5. 4Surface-Mounting nFBGA Packages
    1. 4.1 Design for Manufacturability (DFM)
    2. 4.2 Solder Paste
    3. 4.3 Solder Ball Collapse
    4. 4.4 Reflow
    5. 4.5 Inspection
  6. 5Packing and Shipping
    1. 5.1 Tray Packing Method
    2. 5.2 Tape-and-Reel Packing Method
    3. 5.3 Tape Format
    4. 5.4 Device Insertion
    5. 5.5 Packaging Method
  7. 6Sockets
    1. 6.1 The Design Challenge
    2. 6.2 Contacting the Ball
    3. 6.3 Pinch Contact
    4. 6.4 Micro Tuning Fork Contact
    5. 6.5 Texas Instruments Sockets
  8. 7Summary
  9.   A Frequently Asked Questions
    1.     A.1 Package Questions
    2.     A.2 Assembly Questions
    3.     A.3 Small Body nFBGA Package Questions
  10.   B Package Data Sheets
  11.   C Thermal Modeling Results
  12.   Revision History

2.6 Advanced Design Methods

Another option is to use a combination of blind and buried vias. Blind vias connect either the top or bottom side of the board to inner layers. Buried vias usually connect only the inner layers. Figure 2-7 illustrates this method using 4-mil laser-drilled microvias in the center of the pads and burying the dog bone on layer 2.

GUID-6642F2D7-C0E5-4546-BA4A-AE38CD108699-low.gifFigure 2-7 Buried Vias

Since the buried via does not extend through the underside of the board, the designer can use another set of laser-drilled blind microvias, if needed, to connect the bypass capacitors and other discrete components to the bottom side.

More information on these advanced techniques is available by contacting your local TI field sales office.