LM3243

www.ti.com

SNVS782C – OCTOBER 2010 – REVISED AUGUST 2015

Layout Example (continued)

10.2.3 VBATT Star Supply Connection

Figure 34. Multiple Board Layers - VBATT Supply Star Connection

10.3 DSBGA Package Assembly and Use

Use of the DSBGA package requires specialized board layout, precision mounting and careful re-flow

techniques, as detailed in TI Application Note AN-1112 DSBGA Wafer Level Chip Scale Package (SNVA009).

Please refer to the section Surface Mount Assembly Considerations. For best results in assembly, local

alignment fiducials on the PC board should be used to facilitate placement of the device.

The pad style used with DSBGA package must be the NSMD (non-solder mask defined) type. This means that

the solder-mask opening is larger than the pad size. This prevents a lip that would otherwise form if the solder-

mask and pad overlap, which would hold the device off the surface of the board and interfere with mounting. See

SNVA009 for specific instructions how to do this.

The 16-pin package used for LM3243 has 265 micron solder balls and requires 0.225-mm pads for mounting the

circuit board. The trace to each pad should enter the pad with a 90°entry angle to prevent debris from being

caught in deep corners. Initially, the trace to each pad should be 5.6 mil wide, for a section approximately 5 mil

long, as a thermal relief. Then each trace should neck up or down to its optimal width. An important criterion is

symmetry to insure the solder bumps on the LM3243 re-flow evenly and that the device solders level to the

board. In particular, special attention must be paid to the pads for bumps A1, A3, B1, and B3 since PGND and

PVIN are typically connected to large copper planes, inadequate thermal reliefs can result in inadequate re-flow

of these bumps.

The DSBGA package is optimized for the smallest possible size in applications with red-opaque or infrared-

opaque cases. Because the DSBGA package lacks the plastic encapsulation characteristic of larger devices, it is

vulnerable to light. Backside metallization and/or epoxy coating, along with front-side shading by the printed

circuit board, reduce this sensitivity. However, the package has exposed die edges that are sensitive to light in

the read and infrared range shining on the package’s exposed die edges.

Copyright © 2010–2015, Texas Instruments Incorporated

Submit Documentation Feedback

25

Product Folder Links: LM3243