We are using the DM3730 in CUS package and are having trouble with the chip going for a walk during reflow. From what I can gather this problem gets worse as ball pitch is reduced, and is caused by the decreased adhesive forces between the chip and board and decreased space for the venting of gas. This problem seem exacerbated in the Via Channel design because the large number of missing balls gives again less adhesion, but also much more area for the gas pressure to act upon. It seems like adding a little weight to the chip will solve the problem, but I am not sure how much to add. We have also tried using a jig of sorts that gets reflowed with the board to prevent movement, but this is cumbersome and not suited to automated assembly.
Anyone else having this problem?
Thanks,
Jon Pry