SPI_Layout_Guide_AN(8)

针对高速SPI FLASH的PCB走线规则。

Application

Note

Figure 4.7 SMD vs. NSMD Landing Pad Definition

SolderPadSolderPad

MaskMask

Mask Opening

Pad

Mask Board material

Pad

Board Material

NSMD

SMD

NSMD is generally the recommended land pad configuration because it enables a stronger bond between the solder pad and the solder ball with less stress concentration.

For SMD configurations, it is good practice to make the solder mask opening the same size as the diameter of the solder ball. On NSMD configurations, the solder pad should be between 80% and 100% of the solder ball diameter and the solder mask opening should be 0.15 mm larger than the solder pad to provide ample space for excess solder. Table4.1 provides dimensional recommendations for SMD and NSMD configurations suitable for use with the FAB024, FAC024 and ZSC024 packages.

Table 4.1 NSMD and SMD Dimensional Recommendations for BGA Packages

Configuration

SMDNSMD

OpeningSolder PadSolder MaskSolder PadSolder Mask

Recommended Dimension

0.55 mm0.45 mm0.45 mm0.60 mm

5.Printed Circuit Board Design Recommendations

This section contains general layout recommendations.

5.1Power Supply Decoupling

All S25FL and S70FL SPI Flash have one power supply input pin (VCC) and one ground pin (GND).

Additionally, certain models support a separate I/O supply input pin (VIO) for applications that require I/O levels to be less than VCC. Use of one 0.1 µF ceramic capacitor, normally in a 0603 or 0402 package, is recommended for decoupling each power supply input pin. A decoupling capacitor should be placed as close as possible to the VCC supply input pin, as well as the VIO supply input pin if present.

The routing of the decoupling capacitor should be optimized to achieve low inductance. Power supply trace lengths from the package pads to the vias should be as short as possible with a trace width of approximately 0.6 mm. It is recommended to avoid sharing the same via with 2 or more decoupling capacitors. Figure5.1 shows examples of routing the decoupling capacitor.