本帖最后由 myic200610 于 2013-9-23 11:58 编辑
下面是 CSR8465 datasheet中的一段话，请高手翻译下！
非常感谢！
1.4 PCB Design and Assembly Considerations
This section lists recommendations to achieve maximum board-level reliability of the 5.5 x 5.5 x 1mm VFBGA 68‑ball package:
■ NSMD lands, i.e. lands smaller than the solder mask aperture, are preferred because of the greater accuracy of the metal definition process compared to the solder mask process. With solder mask defined pads, the overlap of the solder mask on the land creates a step in the solder at the land interface, which can cause stress concentration and act as a point for crack initiation.
■ Ideally, use via-in-pad technology to achieve truly NSMD lands. Where this is not possible, a maximum of one trace connected to each land is preferred and this trace should be as thin as possible, this needs to take into consideration its current carrying and the RF requirements.
■ 35µm thick (1oz) copper lands are recommended rather than 17µm thick (0.5oz). This results in a greater standoff which has been proven to provide greater reliability during thermal cycling.
■ Land diameter should be the same as that on the package to achieve optimum reliability.
■ Solder paste is preferred to flux during the assembly process because this adds to the final volume of solder in the joint, increasing its reliability.
■ When using a nickel gold plating finish, the gold thickness should be kept below 0.5µm to prevent brittle gold/tin intermetallics forming in the solder.
说明：
NSMD:Non Solder Mask Defined(非焊接掩模定义) |
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