11.1 Layout Guidelines
Use the following guidelines for the DRV2605L layout:
- The decoupling capacitor for the power supply (VDD) should be placed closed to the device pin.
- The filtering capacitor for the regulator (REG) should be placed close to the device REG pin.
- When creating the pad size for the WCSP pins, TI recommends that the PCB layout use nonsolder mask-defined (NSMD) land. With this method, the solder mask opening is made larger than the desired land area and the opening size is defined by the copper pad width. Figure 65 shows and Table 34 lists appropriate diameters for a wafer-chip scale package (WCSP) layout.
Figure 65. Land Pattern Dimensions
Table 34. Land Pattern Dimensions
| SOLDER PAD
| COPPER PAD
|| SOLDER MASK
| Nonsolder mask
| 275 µm
(0, –25 µm)
| 375 µm
(0, –25 µm)
| 1-oz maximum (32 µm)
|| 275 µm × 275 µm2
| 125-µm thick
- Circuit traces from NSMD defined PWB lands should be 75-µm to 100-µm wide in the exposed area inside the solder mask opening. Wider trace widths reduce device stand-off and impact reliability.
- The recommended solder paste is Type 3 or Type 4.
- The best reliability results are achieved when the PWB laminate glass transition temperature is above the operating the range of the intended application.
- For a PWB using a Ni/Au surface finish, the gold thickness should be less than 0.5 µm to avoid a reduction in thermal fatigue performance.
- Solder mask thickness should be less than 20 µm on top of the copper circuit pattern.
- The best solder stencil performance is achieved using laser-cut stencils with electro polishing. Use of chemically-etched stencils results in inferior solder paste volume control.
- Trace routing away from the WCSP device should be balanced in X and Y directions to avoid unintentional component movement because of solder-wetting forces.